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1. (WO2018143864) SYSTEMS AND METHODS FOR USING NEIGHBORING CELL INFORMATION TO PERFORM MEASUREMENTS
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SYSTEMS AND METHODS FOR USING NEIGHBORING CELL INFORMATION TO

PERFORM MEASUREMENTS

TECHNICAL FIELD

The present disclosure relates, in general, to wireless communications and, more particularly, systems and methods for using neighboring cell information to perform measurements.

BACKGROUND

There has been a lot of work in 3GPP lately on specifying technologies to cover Machine-to-Machine (M2M) and/or Internet of Things (IoT) related use cases. Most recent work for 3 GPP Release 13 includes enhancements to support Machine-Type Communications (MTC) with a new user equipment (UE) category Ml (Cat-Mi), supporting reduced maximum bandwidth of up to 6 physical resource blocks (PRBs), and a Narrowband IoT (NB-IoT) work item specifying a new radio interface (and UE category NB l, Cat-NBl).

Herein, LTE enhancements introduced in 3 GPP Release 13 for MTC will be referred to as "eMTC," while enhancements introduced in 3 GPP Release 14 will be referred to as "FeMTC," including (and not limited to) support for bandwidth limited UEs, Cat-Mi, Cat-M2 and support for coverage enhancements. This is to separate discussion from NB-IoT, although the supported features are similar on a general level.

There are multiple differences between "legacy" LTE and the procedures and channels defined for eMTC or FeMTC work (likewise for NB-IoT). Some important differences include a new physical downlink control channel, called MPDCCH used in eMTC and NPDCCH used in NB-IoT.

In the LTE specifications, multicast and broadcast services have been specified under Multimedia Broadcast Multicast Services (MBMS) enabling transmission of the same content to multiple UEs (in a specified area) at the same time.

At the 3 GPP RAN#70 meeting, a new work item named NB-IoT was approved. The

objective is to specify a radio access for cellular IoT that addresses improved indoor coverage, supports a massive number of low throughput devices, and is not sensitive to delay, ultra-low device cost, low device power consumption and optimized network architecture.

For NB-IoT, three different operation modes are defined. The three operation modes include stand-alone, guard-band, and in-band. In stand-alone mode, the NB-IoT system is operated in dedicated frequency bands. For in-band operation, the NB-IoT system can be placed inside the frequency bands used by the current LTE system, while in the guard-band mode, the NB-IoT system can be operated in the guard band used by the current (legacy) LTE system. NB-IoT can operate with a system bandwidth of 180 kHz. When multiple carriers are configured, several 180 kHz carriers can be used, for example, for increasing the system capacity, inter-cell interference coordination, load balancing, etc.

Certain use cases may require more capacity than usual. These cases may include, for example, software or firmware upgrades. To adapt to these use cases, multi-carrier operations are used. The NB-IoT device listens to the system information on the anchor carrier, but when there is data, the communication can be moved to a secondary carrier.

With respect to Narrowband Reference Signal Received Power (NRSRP), TS 36.214 version 13.3.0 states:

Narrowband reference signal received power (NRSRP), is defined as the linear average over the power contributions (in [W]) of the resource elements that carry narrowband specific reference signals within the considered measurement frequency bandwidth.

For NRS based NRSRP determination of the narrowband reference signals for the first antenna port (R2000) according to TS 36.331 version 14.1 .0 shall be used. If the UE can reliably detect that a second antenna port (R2001) is available it may use the second antenna port in addition to the first antenna port to determine NRSRP.

The reference point for the NRSRP shall be the antenna connector of the UE.

According to TS 36.214 version 13.3.0, NRSRP is applicable for RRC IDLE intra-frequency, RRC IDLE inter-frequency, and RRC CONNECTED intra-frequency.

With respect to Narrowband Reference Signal Received Quality (NRSRQ) measurement for NB-IoT, TS 36.214 version 13.3.0 states:

Narrowband Reference Signal Received Quality (NRSRQ) is defined as the ratio NRSRP/NRSSI. The measurements in the numerator and denominator shall be made over the same set of resource blocks_.

Narrowband Received Signal Strength Indicator (NRSSI), comprises the linear average of the total received power (in [W]) observed [Orthogonal

Frequency Division Multiplex (OFDM)] symbols of measurement subframes, in the measurement bandwidth by the UE from all sources, including co- channel serving and non-serving cells, adjacent channel interference, thermal noise etc.

NRSSI is measured from all OFDM symbols of measurement subframes.

The reference point for the NRSRQ shall be the antenna connector of the UE.

According to TS 36.214 version 13.3.0, NRSRQ is applicable for RRC IDLE intra-frequency and RRC IDLE inter-frequency.

As demonstrated from the emphasized text, for the NRSRQ measurement, the measurement should be done in the same set of resource blocks for both NRSRP and NRSSI. The NRSRP is based on NRS measurement, and NRSSI is measured from all OFDM symbols of measurement subframes. However, there is no clear definition of measurement subframes in the current specification.

In NB-IoT, invalid subframes can be configured and there are no NRSs transmitted in the invalid subframes. The invalid subframes configurations are broadcast in the system information (SI). When performing the idle mode measurement, the UE is neither required to acquire nor verify the SI of its serving cell nor the neighboring cells. Therefore, the UE has no knowledge regarding whether the configuration of its serving cell has changed, or regarding the invalid subframes of the neighboring cells. Therefore, the UE can only make minimum assumptions when it measures NRSRP and NRSSI. In the current NB-IoT specification regarding NRS, we have the following in TS 36.211 version 13.3.0:

When UE receives higher-layer parameter operationModelnfo indicating guardband or standalone,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS.

When UE receives higher-layer parameter operationModelnfo indicating inband-SamePCI or inband-DifferentPCI,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS

Furthermore, as described in TS 36.214 version 13.3.0, for the NRSRQ measurement, the measurement should be done in the same set of resource blocks for both NRSRP and NRSSI. The NRSRP is based on NRS measurement, and NRSSI is measured from all OFDM symbols of measurement Subframes. However, there is no clear definition of measurement Subframes in the current specification.

The non-serving cells can have a different operation mode compared to the serving cell of a UE. As such, Subframes #0, #4 and #9 not containing NSSS are the Subframes that are the minimum assumption a UE can use for the NRSRP/NRSSI measurements. This problem was briefly discussed in Rl-1613071 NRSRP and NRSRQ measurement in NB-IoT, source Ericsson, Reno, USA 14th - 18th November 2016, and Rl -1613450, WF on NB-IoTRel-13 NRSRP, NRSRQ & RLM measurements, source Ericsson, Reno, USA 14th -18th November 2016, but no solution has been reached.

SUMMARY

To address the foregoing problems with existing solutions, disclosed is systems and methods for using neighboring cell information to perform measurements. In certain embodiments, the systems and methods may be implemented in or by a wireless device, which may include a user equipment (UE), and/or a network node, which may include a eNodeB (eNB).

According to certain embodiments, a method is provided in a wireless device in a first cell that receives assistance information from a first network node. The method may include receiving, from the first network node, assistance information related to at least one of an operation mode and a subframe configuration associated with a second cell that is neighboring the first cell. Based on the assistance information, a plurality of measurement subframes may be determined and measurements may be performed using the plurality of measurement subframes.

According to certain embodiments, a wireless device may include memory storing instructions and processing circuitry operable to execute the instructions to cause the wireless device to receive, from a first network node, assistance information related to at least one of an operation mode and a subframe configuration associated with a second cell that is neighboring the first cell. Based on the assistance information, a plurality of measurement subframes may be determined and measurements may be performed using the plurality of measurement subframes.

According to certain embodiments, method by a first network node providing assistance information to a wireless device in a first cell may include acquiring assistance information related to at least one of an operation mode and a subframe configuration associated with a second cell that neighbors the first cell. The assistance information is transmitted to the wireless device for use in determining a plurality of measurement subframes and performing measurements in the plurality of measurement subframes.

According to certain embodiments, a network node providing assistance information to a wireless device in a first cell may include memory storing instructions and processing circuitry operable to execute the instructions to cause the network node to acquire assistance information related to at least one of an operation mode and a subframe configuration associated with a second cell that neighbors the first cell. The assistance information is transmitted to the wireless device for use in determining a plurality of measurement subframes and performing measurements in the plurality of measurement subframes.

Certain embodiments of the present disclosure may provide one or more technical advantages. For example, certain embodiments provide wireless devices with information about the operation mode and/or subframe configurations of neighboring cells. As such, a technical advantage may be that wireless devices are provided with more opportunities for neighboring cell measurements. Another technical advantage may that measurement accuracy may be improved. Still another technical advantage may be that measurement time is reduced. Certain embodiments may additionally or alternatively improve initial MIB acquisition.

Other advantages may be readily apparent to one having skill in the art. Certain embodiments may have none, some, or all of the recited advantages.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the disclosed embodiments and their features and advantages, reference is now made to the following description, taken in conjunction with the accompanying drawings, in which:

FIGURE 1 illustrates an example wireless network broadcasting and using neighboring cell information concerning a narrowband reference signal (NRS) configuration, according to certain embodiments;

FIGURE 2 illustrates an example wireless device for using broadcasted neighboring cell information concerning NRS configuration to perform measurements, according to certain embodiments;

FIGURE 3 illustrates an example method by a wireless device for using broadcasted neighboring cell information concerning NRS configuration to perform measurements, according to certain embodiments;

FIGURE 4 illustrates another example method by a wireless device for using broadcasted neighboring cell information concerning NRS configuration to perform measurements, according to certain embodiments;

FIGURE 5 illustrates an example virtual computing device for using broadcasted neighboring cell information concerning NRS configuration to perform measurements, according to certain embodiments;

FIGURE 6 illustrate an example network node for broadcasting neighboring cell information concerning NRS configuration to assist wireless devices in performing measurements, according to certain embodiments;

FIGURE 7 illustrates an example method by a network node for broadcasting neighboring cell information concerning NRS configuration to assist wireless devices in performing measurements, according to certain embodiments;

FIGURE 8 illustrates another example method by a network node for broadcasting neighboring cell information concerning NRS configuration to assist wireless devices in performing measurements, according to certain embodiments;

FIGURE 9 illustrates another example virtual computing device for using broadcasted neighboring cell information concerning NRS configuration to perform measurements, according to certain embodiments;

FIGURE 10 illustrates an exemplary radio network controller or core network node, according to certain embodiments;

FIGURE 11 illustrates an example of a virtualization environment in which functions implemented by some embodiments may be virtualized, according to certain embodiments; FIGURE 12 illustrates NRS around PO on non-anchor carriers, according to certain embodiments;

FIGURE 13 illustrates NRS around Random Access Response (RAR) window on non-anchor carriers, according to certain embodiments;

FIGURE 14 illustrates NB-SIB scheduling, according to certain embodiments;

FIGURE 15 shows the performance of MIB-NB acquisition for the in-band deployment, according to certain embodiments; and

FIGURE 16 illustrates of NB-SIB l transmission in layer 1 (LI), according to certain embodiments.

DETAILED DESCRIPTION

Particular embodiments of the present disclosure may provide solutions for broadcasting and using neighboring cell information concerning narrowband reference signal (NRS) configuration to assist in performing measurements. Particular embodiments are described in FIGURES 1-16 of the drawings, like numerals being used for like and corresponding parts of the various drawings.

FIGURE 1 illustrates a wireless network 100 for broadcasting and using neighboring cell information concerning a narrowband reference signal (NRS) configuration, in accordance with certain embodiments. Network 100 includes one or more wireless devices 110A-C, which may be interchangeably referred to as wireless devices 110 or UEs 110, and network nodes 115A-C, which may be interchangeably referred to as network nodes 115 or eNodeBs 115. A wireless device 110 may communicate with network nodes 115 over a wireless interface. For example, wireless device 1 10A may transmit wireless signals to one or more of network nodes 115, and/or receive wireless signals from one or more of network nodes 115. The wireless signals may contain voice traffic, data traffic, control signals, and/or any other suitable information. In certain embodiments, an area of wireless signal coverage associated with a network node 115 may be referred to as a cell 120. For example, network node 115A may serve a wireless device 110A in a first cell 120 A, while network node 115 B may serve a wireless device HOB in a second cell 120B. Two cells that lie adjacent to each other and/or include an overlapping area of signal coverage may be considered to be neighboring cells. Thus, second cell 120B may be considered a neighboring cell to first cell 120A and third cell 120C. Likewise, network node 115A and network node 115B that serve neighboring areas may be considered to be neighboring nodes. Though network node 115A and network node B are depicted as being located at different physical locations, certain embodiments described herein may contemplate network node 115A and network node 115B being co-located at one physical location. In such a scenario, first cell 120 A and second cell 120B may substantially overlap, though it may be that one of first cell 120A and second cell 120B is larger than the other.

In some embodiments, wireless devices 110 may have D2D capability. Thus, wireless devices 110 may be able to receive signals from and/or transmit signals directly to another wireless device 110. For example, wireless device 110A may be able to receive signals from and/or transmit signals to wireless device HOB.

In certain embodiments, network nodes 115 may interface with a radio network controller (not depicted in FIGURE 1). The radio network controller may control network nodes 115 and may provide certain radio resource management functions, mobility management functions, and/or other suitable functions. In certain embodiments, the functions of the radio network controller may be included in network node 115. The radio network controller may interface with a core network node. In certain embodiments, the radio network controller may interface with the core network node via an interconnecting network. The interconnecting network may refer to any interconnecting system capable of transmitting audio, video, signals, data, messages, or any combination of the preceding. The interconnecting network may include all or a portion of a public switched telephone network (PSTN), a public or private data network, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a local, regional, or global communication or computer network such as the Internet, a wireline or wireless network, an enterprise intranet, or any other suitable communication link, including combinations thereof.

In some embodiments, the core network node may manage the establishment of communication sessions and various other functionalities for wireless devices 110. Wireless devices 110 may exchange certain signals with the core network node using the non-access stratum layer. In non-access stratum signaling, signals between wireless devices 110 and the core network node may be transparently passed through the radio access network. In certain embodiments, network nodes 115 may interface with one or more network nodes over an internode interface. For example, network nodes 115A and 115B may interface over an X2 interface.

As described above, example embodiments of network 100 may include one or more wireless devices 110, and one or more different types of network nodes capable of communicating (directly or indirectly) with wireless devices 110. Wireless device 110 may refer to any type of wireless device communicating with a node and/or with another wireless device in a cellular or mobile communication system. Examples of wireless device 110 include a target device, a device-to-device (D2D) capable device, a machine type communication (MTC) device or other UE capable of machine-to-machine (M2M) communication, a mobile phone or other terminal, a smart phone, a PDA (Personal Digital

Assistant), a portable computer (e.g., laptop, tablet), a sensor, a modem, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, ProSe UE, V2V UE, V2X UE, MTC UE, eMTC UE, FeMTC UE, UE Cat 0, UE Cat Ml, narrowband Internet of Things (NB-IoT) UE, UE Cat NB1, or another device that can provide wireless communication. A wireless device 110 may also be referred to as UE, a station (STA), a device, or a terminal in some embodiments. Also, in some embodiments, generic terminology, "radio network node" (or simply "network node") is used. It can be any kind of network node, which may comprise a Node B, base station (BS), multi- standard radio (MSR) radio node such as MSR BS, eNode B, MeNB, SeNB, a network node belonging to MCG or SCG, network controller, radio network controller (RNC), base station controller (BSC), relay donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, RRU, RRH, nodes in distributed antenna system (DAS), core network node (e.g. MSC, MME etc.), O&M, OSS, SON, positioning node (e.g. E-SMLC), MDT, test equipment, or any suitable network node. Example embodiments of wireless devices 110, network nodes 115, and other network nodes (such as radio network controller or core network node) are described in more detail with respect to FIGURES 2, 6, and 10, respectively.

Although FIGURE 1 illustrates a particular arrangement of network 100, the present disclosure contemplates that the various embodiments described herein may be applied to a variety of networks having any suitable configuration. For example, network 100 may include any suitable number of wireless devices 110 and network nodes 115, as well as any additional elements suitable to support communication between wireless devices or between a wireless device and another communication device (such as a landline telephone). Furthermore, although certain embodiments may be described as implemented in a long term evolution (LTE) network, the embodiments may be implemented in any appropriate type of telecommunication system supporting any suitable communication standards and using any suitable components, and are applicable to any LTE based systems such as MTC, eMTC, and NB-IoT. As an example, MTC UE, eMTC UE, and NB-IoT UE may also be called UE category 0, UE category Ml and UE category NB1, respectively. However, the embodiments are applicable to any radio access technology (RAT) or multi -RAT systems in which the wireless device receives and/or transmits signals (e.g., data). For example, the various embodiments described herein may also be applicable to, LTE-Advanced, and LTE-U UMTS, LTE FDD/TDD, WCDMA/HSPA, GSM/GERAN, WiFi, WLAN, cdma2000, WiMax, 5G, New Radio (NR), another suitable radio access technology, or any suitable combination of one or more radio access technologies. It is noted that 5G, the fifth generation of mobile telecommunications and wireless technology is not yet fully defined but in an advanced draft stage with 3GPP. It includes work on 5G New Radio (NR) Access Technology. LTE terminology is used herein in a forward looking sense, to include equivalent 5G entities or functionalities although a different term may be specified in 5G. A general description of the agreements on 5G NR Access Technology is contained in most recent versions of the 3GPP 38-series Technical Reports. Although certain embodiments may be described in the context of wireless transmissions in the downlink, the present disclosure contemplates that the various embodiments are equally applicable in the uplink and vice versa. The described techniques are generally applicable for transmissions from both network nodes 115 and wireless devices 110.

FIGURE 2 illustrates an example wireless device 1 10 for using neighboring cell information concerning NRS configuration in performing measurements, in accordance with certain embodiments. As depicted, wireless device 110 includes transceiver 210, processing circuitry 220, and memory 230. In some embodiments, transceiver 210 facilitates transmitting wireless signals to and receiving wireless signals from network node 115 (e.g., via an antenna), processing circuitry 220 executes instructions to provide some or all of the functionality described above as being provided by wireless device 110, and memory 230 stores the instructions executed by processing circuitry 220. Examples of a wireless device 110 are provided above.

Processing circuitry 220 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of wireless device 110. In some embodiments, processing circuitry 220 may include, for example, one or more computers, one or more central processing units (CPUs), one or more processors, one or more microprocessors, one or more applications, and/or other logic.

Memory 230 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by processing circuitry. Examples of memory 230 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or or any other volatile or non-volatile, non-transitory computer-readable and/or computer-executable memory devices that store information.

Other embodiments of wireless device 110 may include additional components beyond those shown in FIGURE 2 that may be responsible for providing certain aspects of the wireless device's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above).

According to certain embodiments, wireless device 110 may use the NRS configuration information when performing measurements. For example, as noted above, a NRSRQ measurement may be performed in the same set of resource blocks for both NRSRP and NRSSI. The NRSRP may be based on NRS measurement. NRSSI is measured from all OFDM symbols of measurement subframes. In NB-IoT, invalid subframes can be configured. However, wireless devices may not know which subframes are measurement subframes that include NRS and which subframes are invalid subframes.

According to conventional wireless systems, a wireless device 1 10 will not acquire the system information of the non-serving cells, which may also be referred to as neighboring cells. Additionally, when performing RSRP measurement, wireless device is not required to verify the system information in the serving cell, and therefore, if there is a configuration change of the valid subframes, wireless device 110 may not be informed. Therefore, conventionally, a wireless device may only make the minimum assumption when it measures the NRSSI. As stated above, the current NB-IoT specification in TS 36.21 1 version 13.3.0 states:

When UE receives higher-layer parameter operationModelnfo indicating guardband or standalone,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may

assume narrowband reference signals are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS.

When UE receives higher-layer parameter operationModelnfo indicating inband-SamePCI or inband-DifferentPCI,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may

assume narrowband reference signals are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS.

However, non-serving cells may have a different operation mode and/or different valid subframe configurations than the serving cell of wireless device 1 10. Accordingly, wireless devices 110 have conventionally assumed that only subframes #0, #4 and #9 can be used for the NRSSI measurement.

Currently, for NB-IoT, TS 36.331 version 14.1.0 provides:

• The IE SystemInformationBlockType3-NB contains cell re-selection information common for intra-frequency, and inter-frequency cell re- selection as well as intra-frequency cell re-selection information other than neighboring cell related.

• The IE SystemInformationBlockType4-NB contains neighboring cell related information relevant only for intra-frequency cell re-selection. The IE includes cells with specific re-selection parameters.

• The IE SystemInformationBlockType5-NB contains information relevant only for inter-frequency cell re-selection i.e. information about other NB-IoT frequencies and inter-frequency neighboring cells relevant for cell re- selection. The IE includes cell re-selection parameters common for a frequency.

However, none of the SI block contains information regarding operation modes or valid downlink subframe configurations or neighboring cells.

Accordingly, in certain embodiments, a network node 1 15 may signal assistance information about neighboring cells to wireless device 1 10 to assist wireless device 110 in the performance of measurements. In certain embodiments, the assistance information may be received from and/or related to a cell that a wireless device 110 listens to or has selected. For example, the assistance information may be received from network node with which wireless device is synchronized. In particular embodiments, the assistance information is

signaled in one of the previously mentioned SI blocks or a new SI block. In other particular embodiments, the assistance information may be signaled to wireless device 110 through dedicated signaling. For example, the assistance information may be signaled using dedicated RRC signaling.

If, based on the wireless device's measurements, wireless device 1 10 decides to select a new serving cell, it may be beneficial for wireless device 110 to know the operation mode and valid downlink subframe configurations of the new serving cell prior to obtaining the MIB and SIBl of the new serving cell. For example, such assistant information may help wireless device to improve the performance when acquiring the new MIB and SIB 1. Specifically, in a particular embodiment, wireless device 1 10 may perform better cross subframe channel estimations by using more or all of the available subframes rather than assuming the minimum number of subframes that can be used where assistance information is not provided.

In a particular embodiment, for example, network node 115 may signal assistance information including any one or a combination of the following:

• Information indicating whether the neighboring cell is in the same operation mode as the serving cell. In general, the serving cell may be the current cell that wireless device 110 is served in or has selected to remain in. A technical advantage of such an embodiment may be the minimization of signaling overhead in the system information. Based on the assistance information, wireless device 110 may conclude that NRS are present in subframes #0, #1, #3, #4 and #9 or in #0, #4 and #9, depending on the specific operation mode of the serving cell and neighboring cell.

• Information explicitly indicating the operation mode of each of one or more neighboring cells.

• Information explicitly indicating the operation mode of each of carrier frequency. This is based on the assumption that usually the same carrier frequency will be used for the same operation mode. A technical advantage may be that a balance between SI overhead and flexibility is obtained.

• Information indicating whether the neighboring cell is in the same valid downlink subframe configuration as the serving cell. Serving cell is the current cell that a UE selected to stay in. A technical advantage may be a minimization of the signaling overhead in the SI. The operation mode may not need to be signaled explicitly.

• Information explicitly indicating the operation mode of each of the neighboring cells and/or the valid downlink subframe configuration of each of the neighboring cells. While this may result in additional signaling overhead, a technical advantage may be guaranteed maximum knowledge of the NRS configuration to give best idle mode performance.

• Information explicitly indicating the valid downlink subframe configuration of each of carrier frequency. This is based on the assumption that usually the same carrier frequency will be used for the same operation mode, and in a synchronized network with broadcast service such as, for example, MBMS, the same valid subframe configuration is preferred. A technical advantage may be that a balance between SI overhead and flexibility is obtained.

FIGURE 3 illustrates an example method by a wireless device 1 10 for using broadcasted neighboring cell information to perform measurements, according to certain embodiments. The method may begin at step 302 when wireless device 110 receives, from a first network node 115, assistance information related to an NB-IoT operation mode in a first cell. Though NB-IoT operation mode is described as an example, it is recognized that the assistance information may relate to any suitable operation mode such that the described techniques are not limited to NB-IoT.

At step 304, wireless device 110 determines a plurality of measurement subframes based on the assistance information related to the NB-IoT operation mode. Optionally, the wireless device determines a number of resource elements containing and/or comprising NRS based on assistance information related to the NB-IoT operation mode such as number of antenna ports used for transmission of the NRS.

At step 306, wireless device 110 performs measurements using the measurement subframes . In certain embodiments, the measurement subframes may contain NRS and the NRS may be used in performing the measurements. In certain embodiments, a NRSSI

measurement may be performed from all OFDM symbols in the plurality of measurement subframes. Additionally or alternatively, a NRSRP measurement may be performed based on one or more OFDM symbols containing NRS in the plurality of measurement subframes. Optionally, the wireless device performs the measurements using the determined number of resource elements.

In certain embodiments, the assistance information related to the NB-IoT operation mode may include an explicit indication of the NB-IoT operation mode of the first network node. For example, in particular embodiments, the NB-IoT operation mode is selected from the group consisting of a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode.

In certain other embodiments, the assistance information may include an explicit indication of a respective operation mode of each of a plurality of carrier frequencies. Determining the plurality of measurement subframes may thus comprise assuming the NB-IoT is the same for a carrier frequency.

Additionally or alternatively, in certain embodiments, the assistance information may include any one or combination of the following:

• whether the neighboring cell is in a same valid downlink subframe configuration as the serving cell;

• an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

• an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells.

• an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies;

• the number of antenna ports used for transmission of the Narrowband reference signals (NRS);

• configuration information for the cell-specific reference signals (CRS).

In one example embodiment, wireless device 110 may receive assistance information from first network node 115A. First network node 115A may operate as a serving node for wireless device 110A in a second cell 120A. The assistance information may include a NB-IoT operation mode for a second network node 1 15B that is a serving node for the first cell 120B. Second network node 115B may neighbor first network node 115A and second cell 120A.

In another example embodiment, first network node 115B may be a non-serving node for wireless device 110A and a neighboring node to a second network node 115A. Second network node 115 A may be a serving network node to wireless device 11 OA. As such, in order for first network node 115B to transition from a non-serving node to a serving node for wireless device 110A a handover would have to take place. However, wireless device 110A may be synchronized with first network node 115B and receive assistance information for a NB-IoT operation mode of a first cell HOB from first network node 115B.

In another example embodiment, first network node 115B may be a non-serving node for wireless device 110A and a neighboring node to a second network node 115A. Second network node 115 A may be a serving network node to wireless device 11 OA. As such, in order for first network node 115B to transition from a non-serving node to a serving node for wireless device 110A a handover would have to take place. However, wireless device 110A may be synchronized with first network node 115B and receive assistance information for a NB-IoT operation mode of a third network node 115C that is a neighboring node to at least one of the first network node 115A or the second network node 115B.

FIGURE 4 illustrates another example method by a wireless device 110 for using neighboring cell information to perform measurements in a first cell, according to certain embodiments. The method may begin at step 402 when wireless device 1 10 in a first cell receives, from a first network node 115, assistance information related to an operation mode and/or a subframe configuration associated with a second cell 120 that neighbors the first cell.

At step 404, wireless device 110 determines a plurality of measurement subframes based on the assistance information. In a particular embodiment, for example, wireless device 110 may determine a number of resource elements containing and/or comprising NRS based on assistance information. For example, wireless device 110 may determine a number of antenna ports used for transmission of the NRS based on the assistance information. As another example, wireless device 110 may determine an antenna port configuration based on the assistance information.

At step 406, wireless device 110 performs measurements using the measurement subframes. According to certain embodiments, the measurement subframes may contain NRS and the NRS may be used in performing the measurements. In a particular embodiment, for example, the measurement subframes may contain NPSSs and/or NSSSs. One or both of the NPSS and NSSS may be used in performing the measurements.

In a particular embodiment, a NRSSI measurement may be performed from all OFDM symbols in the plurality of measurement subframes. Additionally or alternatively, a NRSRP measurement may be performed based on one or more OFDM symbols containing NRS in the plurality of measurement subframes. Optionally, the wireless device performs the measurements using the determined number of resource elements.

According to certain embodiments, the assistance information may include an NB-IoT operation mode of the second cell 120. In a particular embodiment, the assistance information is an explicit indication of the NB-IoT operation mode of the second cell 120. For example, in various embodiments, the assistance information may identify the NB-IoT operation mode as being a stand-alone operation mode, a guard-band operation mode, or an in-band operation mode.

In certain other embodiments, the assistance information may include an explicit indication of a respective operation mode of each of a plurality of carrier frequencies. In a particular embodiment, it may be assumed that the NB-IoT is the same within each carrier frequency.

Additionally or alternatively, in certain embodiments, the assistance information may include any one or combination of the following:

• whether the second cell 120 has a same downlink subframe configuration as the first cell 120;

• an explicit indication of the operation mode of the second cell 120 and a valid downlink subframe configuration for the second cell 120;

• an explicit indication of a respective operation mode of each of a plurality of additional cells 120 that neighbor the first cell 120 and a valid downlink subframe configuration for each of the additional cells 120.

• an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies;

• the number of antenna ports used for transmission of the Narrowband reference signals (NRS);

· configuration information for the cell-specific reference signals (CRS).

In one example embodiment, first network node 115A, which serves wireless device 110A in the first cell 120, also serves the second cell 120. For example, first network node 115A may serve multiple cells 120A-B and provide assistance information for all cells 120A-B to wireless device 110A.

In another example embodiment, first network node 115A may serve wireless device

110A in first cell 120A, and the assistance information may relate to a second network node 115B in second cell 120B that neighbors first cell 120A. In a particular embodiment, the first network node 115A and second network node 115B may be physically remote from one another. In another embodiment, first network node 115A and second network node 115B may be physically co-located.

In certain embodiments, the method for using broadcasted neighboring cell information to perform measurements as described above may be performed by a computer networking virtual apparatus. FIGURE 5 illustrates an example virtual computing device 500 for using broadcasted neighboring cell information to perform measurements, according to certain embodiments. In certain embodiments, virtual computing device 500 may include modules for performing steps similar to those described above with regard to the method illustrated and described in FIGURES 3 and/or 4. For example, virtual computing device 500 may include a receiving module 502, a determining module 504, a performing module 506, and any other suitable modules for using broadcasted neighboring cell information concerning NRS configuration to perform measurements. In some embodiments, one or more of the modules may be implemented using processing circuitry 220 of FIGURE 2. In certain embodiments, the functions of two or more of the various modules may be combined into a single module.

The receiving module 502 may perform the receiving functions of virtual computing device 500. For example, in a particular embodiment, receiving module 502 may receive, from network node 115, assistance information related to an NB-IoT operation mode in a

second cell 120 that neighbors a first cell 120. As another example, in a particular embodiment, receiving module 502 may receive, from network node 115 serving wireless device 110 in a first cell 120, assistance information related to operation mode and/or a subframe configuration associated with a second cell 120 that neighbors the first cell 120.

The determining module 504 may perform certain of the determining functions of virtual computing device 500. For example, in a particular embodiment, determining module 504 may determine a plurality of measurement subframes based on the assistance information.

The performing module 506 may perform certain performing functions of virtual computing device 500. For example, in a particular embodiment, using module 506 may perform measurements using the measurement subframes.

Other embodiments of virtual computing device 500 may include additional components beyond those shown in FIGURE 5 that may be responsible for providing certain aspects of the wireless device's 110 functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solutions described above). The various different types of wireless devices 110 may include components having the same physical hardware but configured (e.g., via programming) to support different radio access technologies, or may represent partly or entirely different physical components.

FIGURE 6 illustrate an example network node 115 for broadcasting neighboring cell information concerning NRS configuration to assist wireless devices 1 10 in performing measurements, according to certain embodiments. As described above, network node 115 may be any type of radio network node or any network node that communicates with a wireless device and/or with another network node. Examples of a network node 115 are provided above.

Network nodes 115 may be deployed throughout network 100 as a homogenous deployment, heterogeneous deployment, or mixed deployment. A homogeneous deployment may generally describe a deployment made up of the same (or similar) type of network nodes 115 and/or similar coverage and cell sizes and inter-site distances. A heterogeneous deployment may generally describe deployments using a variety of types of network nodes 115 having different cell sizes, transmit powers, capacities, and inter-site distances. For example, a heterogeneous deployment may include a plurality of low-power nodes placed throughout a macro-cell layout. Mixed deployments may include a mix of homogenous portions and heterogeneous portions.

Network node 115 may include one or more of transceiver 610, processing circuitry 620, memory 630, and network interface 640. In some embodiments, transceiver 610 facilitates transmitting wireless signals to and receiving wireless signals from wireless device 110 (e.g., via an antenna), processing circuitry 620 executes instructions to provide some or all of the functionality described above as being provided by a network node 115, memory 630 stores the instructions executed by processing circuitry 620, and network interface 640 communicates signals to backend network components, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), core network nodes or radio network controllers, etc.

In certain embodiments, network node 115 may be capable of using multi-antenna techniques, and may be equipped with multiple antennas and capable of supporting MTMO techniques. The one or more antennas may have controllable polarization. In other words, each element may have two co-located sub elements with different polarizations (e.g., 90 degree separation as in cross-polarization), so that different sets of beamforming weights will give the emitted wave different polarization.

Processing circuitry 620 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of network node 115. In some embodiments, processing circuitry 620 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic.

Memory 630 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by a processor. Examples of memory 630 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or or any other volatile or non-volatile, non-transitory computer-readable and/or computer-executable

memory devices that store information.

In some embodiments, network interface 640 is communicatively coupled to processing circuitry 620 and may refer to any suitable device operable to receive input for network node 115, send output from network node 115, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. Network interface 640 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

Other embodiments of network node 115 may include additional components beyond those shown in FIGURE 6 that may be responsible for providing certain aspects of the radio network node's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solutions described above). The various different types of network nodes may include components having the same physical hardware but configured (e.g., via programming) to support different radio access technologies, or may represent partly or entirely different physical components. Additionally, the terms first and second are provided for example purposes only and may be interchanged.

FIGURE 7 illustrates an example method 700 by a network node 115 for broadcasting neighboring cell information to assist wireless devices in performing measurements, according to certain embodiments. The method begins at step 702 when network node 115 acquires assistance information related to an NB-IoT operation mode in a first cell.

At step 704, network node 115 transmits the assistance information related to the NB-IoT operation mode to a wireless device for use in performing measurements in a plurality of measurement subframes.

In certain embodiments, the assistance information may include any one or combination of the following:

• whether the first cell is in a same valid downlink subframe configuration as a serving cell of wireless device 110;

· an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

• an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells;

• an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies

• the number of antenna ports used for transmission of the Narrowband reference signals (NRS);

• configuration information for the cell-specific reference signals (CRS).

In one example embodiment, first network node 115A may transmit assistance information to wireless device 110A. First network node 115A may operate as a serving node for wireless device 110A in a second cell 120A. The assistance information may include a NB-IoT operation mode for a second network node 115B that is a serving node for the first cell 120B. Second network node 115B may neighbor first network node 115A and second cell 120 A.

In another example embodiment, first network node 115B may be a non-serving node for wireless device 110A and a neighboring node to a second network node 115A. Second network node 115A may be a serving network node to wireless device 1 10A in cell 120A, while first network node 115B serves cell HOB. As such, in order for first network node 115B to transition from a non-serving node to a serving node for wireless device 11 OA a handover would have to take place. However, wireless device 11 OA may be synchronized with first network node 115B, and first network node 115B may transmit assistance information for a NB-IoT operation mode of a first network node 115B in cell 110B .

In another example embodiment, first network node 115B may be a non-serving node for wireless device 110A and a neighboring node to a second network node 115A. Second network node 115A may be a serving network node to wireless device 1 10A in cell 120A, while first network node 115B serves cell HOB. As such, in order for first network node 115B to transition from a non-serving node to a serving node for wireless device 11 OA a handover would have to take place. However, wireless device 11 OA may be synchronized with first network node 115B and receive assistance information for a NB-IoT operation mode of a third network node 115C that is a neighboring node to at least one of the first network node 115A or the second network node 115B.

FIGURE 8 illustrates another example method 800 by a first network node 115 providing assistance information to a wireless device 110 in a first cell 120, the first network node, according to certain embodiments. The method begins at step 802 when a first network node 115 acquires assistance information related to an operation mode and/or a subframe configuration associated with a second cell 120 that neighbors the first cell 120.

At step 804, first network node 115 transmits the assistance information to the wireless device 110 for use in determining a plurality of measurement subframes and performing measurements in the plurality of measurement subframes. According to certain embodiments, the measurement subframes may contain NRS for use in performing the measurements. In a particular embodiment, for example, the measurement subframes contain at least one of NPSS and NSSS for use in performing the measurements.

According to certain embodiments, the assistance information may include an NB-IoT operation mode of the second cell 120. For example, the assistance information may identify whether the operation mode of the second cell 120 is a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode. In a particular embodiment, the assistance information may include an explicit indication of a respective operation mode of each of a plurality of carrier frequencies. Additionally or alternatively, the assistance information may indicate whether the second cell 120 has a same downlink subframe configuration as the first cell 120.

According to certain other embodiments, the assistance information may alternatively or additionally include a subframe configuration of the second cell 120. In a particular embodiment, for example, the assistance information may include an explicit indication of the operation mode of the second cell 120 and a downlink subframe configuration for the second cell 120.

According to a particular embodiment, the assistance information includes an antenna port configuration for the second cell 120. For example, the assistance information may identify a number of antenna ports used for transmission of the NRS. In another embodiment, the assistance information may additionally or alternatively include configuration information for CRS.

In one example embodiment, first network node 115 may serve the first cell 120 and the second 120. For example, first network node 115A may serve multiple cells 120A-B and provide assistance information for one or more cells 120A-B to wireless device 110.

In another example embodiment, first network node 115 may serve wireless device 110 in cell 120A, and the assistance information may relate to a second network node 115B in second cell 120B. In a particular embodiment, the first network node 115A and second network node 115B may be physically remote from one another. In another embodiment, first network node 115A and second network node 115B may be physically co-located.

In certain embodiments, the method for providing assistance information to a wireless device 110 in a first cell 120, the first network node as described above may be performed by a computer networking virtual apparatus. FIGURE 9 illustrates an example virtual computing device 900 for providing assistance information to a wireless device 110 in a first cell 120, the first network node, according to certain embodiments. In certain embodiments, virtual computing device 900 may include modules for performing steps similar to those described above with regard to the method illustrated and described in FIGURE 8. For example, virtual computing device 900 may include a acquiring module 902, a transmitting module 904, and any other suitable modules for broadcasting neighboring cell information concerning NRS configuration to assist wireless devices in performing measurements. In some embodiments, one or more of the modules may be implemented using processing circuitry 620 of FIGURE 6. In certain embodiments, the functions of two or more of the various modules may be combined into a single module.

The acquiring module 902 may perform the acquiring functions of virtual computing device 900. For example, in a particular embodiment, acquiring module 902 may acquire assistance information related to an NB-IoT operation mode in a first cell. As another example, in a particular embodiment, acquiring module 902 may acquire assistance information related to at least one of an operation mode and a subframe configuration of a second cell 120 that neighbors the first cell 120.

The transmitting module 904 may perform the transmitting functions of virtual computing device 900. For example, in a particular embodiment, transmitting module 904 may transmit the assistance information related to the NB-IoT operation mode to a wireless device for use in performing measurements in a plurality of measurement subframes. As

another example, in a particular embodiment, transmitting module 904 may transmit the assistance information to a wireless device 110 for use in determining measurement subframes and performing measurements in the measurement subframes.

Other embodiments of virtual computing device 900 may include additional components beyond those shown in FIGURE 9 that may be responsible for providing certain aspects of the network node's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solutions described above). The various different types of network node 115 may include components having the same physical hardware but configured (e.g., via programming) to support different radio access technologies, or may represent partly or entirely different physical components.

FIGURE 10 illustrates an exemplary radio network controller or core network node, in accordance with certain embodiments. Examples of network nodes can include a mobile switching center (MSC), a serving GPRS support node (SGSN), a mobility management entity (MME), a radio network controller (RNC), a base station controller (BSC), and so on. The radio network controller or core network node 1000 includes processing circuitry 1002, network interface 1004, and memory 1006. In some embodiments, processing circuitry 1002 executes instructions to provide some or all of the functionality described above as being provided by the network node, memory 1006 stores the instructions executed by processing circuitry 1002, and network interface 1004 communicates signals to any suitable node, such as a gateway, switch, router, Internet, Public Switched Telephone Network (PSTN), network nodes 115, radio network controllers or core network nodes 1000, etc.

Processing circuitry 1002 may include any suitable combination of hardware and software implemented in one or more modules to execute instructions and manipulate data to perform some or all of the described functions of the radio network controller or core network node 1000. In some embodiments, processing circuitry 1002 may include, for example, one or more computers, one or more central processing units (CPUs), one or more microprocessors, one or more applications, and/or other logic.

Memory 1006 is generally operable to store instructions, such as a computer program, software, an application including one or more of logic, rules, algorithms, code, tables, etc. and/or other instructions capable of being executed by a processor. Examples of memory

1006 include computer memory (for example, Random Access Memory (RAM) or Read Only Memory (ROM)), mass storage media (for example, a hard disk), removable storage media (for example, a Compact Disk (CD) or a Digital Video Disk (DVD)), and/or or any other volatile or non-volatile, non-transitory computer-readable and/or computer-executable memory devices that store information.

In some embodiments, network interface 1004 is communicatively coupled to processing circuitry 1002 and may refer to any suitable device operable to receive input for the network node, send output from the network node, perform suitable processing of the input or output or both, communicate to other devices, or any combination of the preceding. Network interface 1004 may include appropriate hardware (e.g., port, modem, network interface card, etc.) and software, including protocol conversion and data processing capabilities, to communicate through a network.

Other embodiments of the network node may include additional components beyond those shown in FIGURE 10 that may be responsible for providing certain aspects of the network node's functionality, including any of the functionality described above and/or any additional functionality (including any functionality necessary to support the solution described above).

FIGURE 11 is a schematic block diagram illustrating an example of a virtualization environment 1500 in which functions implemented by some embodiments may be virtualized. In the present context, virtualizing means creating virtual versions of apparatuses or devices which may include virtualizing hardware platforms, storage devices and networking resources. As used herein, virtualization can be applied to a node 115 (e.g., a virtualized base station or a virtualized radio access node) or to a device 110 (e.g., a UE, a wireless device or any other type of communication device) or components thereof and relates to an implementation in which at least a portion of the functionality is implemented as one or more virtual components (e.g., via one or more applications, components, functions, virtual machines or containers executing on one or more physical processing nodes in one or more networks).

In some embodiments, some or all of the functions described herein may be implemented as virtual components executed by one or more virtual machines implemented in one or more virtual environments 1500 hosted by one or more of hardware nodes 1530.

Further, in embodiments in which the virtual node is not a radio access node or does not require radio connectivity (e.g., a core network node), then the network node may be entirely virtualized.

The functions may be implemented by one or more applications 1520 (which may alternatively be called software instances, virtual appliances, network functions, virtual nodes, virtual network functions, etc.) operative to implement some of the features, functions, and/or benefits of some of the embodiments disclosed herein. Applications 1520 are run in virtualization environment 1500 which provides hardware 1530 comprising processing circuitry 1560 and memory 1590. Memory 1590 contains instructions 1595 executable by processing circuitry 1560 whereby application 1520 is operative to provide one or more of the features, benefits, and/or functions disclosed herein.

Virtualization environment 1500, comprises general -purpose or special -purpose network hardware devices 1530 comprising a set of one or more processors or processing circuitry 1560, which may be commercial off-the-shelf (COTS) processors, dedicated Application Specific Integrated Circuits (ASICs), or any other type of processing circuitry including digital or analog hardware components or special purpose processors. Each hardware device may comprise memory 1590-1 which may be non-persistent memory for temporarily storing instructions 1595 or software executed by processing circuitry 1560. Each hardware device may comprise one or more network interface controllers (NICs) 1570, also known as network interface cards, which include physical network interface 1580. Each hardware device may also include non-transitory, persistent, machine-readable storage media 1590-2 having stored therein software 1595 and/or instructions executable by processing circuitry 1560. Software 1595 may include any type of software including software for instantiating one or more virtualization layers 1550 (also referred to as hypervisors), software to execute virtual machines 1540 as well as software allowing it to execute functions, features and/or benefits described in relation with some embodiments described herein.

Virtual machines 1540, comprise virtual processing, virtual memory, virtual networking or interface and virtual storage, and may be run by a corresponding virtualization layer 1550 or hypervisor. Different embodiments of the instance of virtual appliance 1520 may be implemented on one or more of virtual machines 1540, and the implementations may be made in different ways.

During operation, processing circuitry 1560 executes software 1595 to instantiate the hypervisor or virtualization layer 1550, which may sometimes be referred to as a virtual machine monitor (VMM). Virtualization layer 1550 may present a virtual operating platform that appears like networking hardware to virtual machine 1540.

As shown in FIGURE 11, hardware 1530 may be a standalone network node with generic or specific components. Hardware 1530 may comprise antenna 15225 and may implement some functions via virtualization. Alternatively, hardware 1530 may be part of a larger cluster of hardware (e.g. such as in a data center or customer premise equipment (CPE)) where many hardware nodes work together and are managed via management and orchestration (MANO) 15100, which, among others, oversees lifecycle management of applications 1520.

Virtualization of the hardware is in some contexts referred to as network function virtualization (NFV). NFV may be used to consolidate many network equipment types onto industry standard high volume server hardware, physical switches, and physical storage, which can be located in data centers, and customer premise equipment.

In the context of NFV, virtual machine 1540 may be a software implementation of a physical machine that runs programs as if they were executing on a physical, non-virtualized machine. Each of virtual machines 1540, and that part of hardware 1530 that executes that virtual machine, be it hardware dedicated to that virtual machine and/or hardware shared by that virtual machine with others of the virtual machines 1540, forms a separate virtual network elements (VNE).

Still in the context of NFV, Virtual Network Function (VNF) is responsible for handling specific network functions that run in one or more virtual machines 1540 on top of hardware networking infrastructure 1530 and corresponds to application 1520 in FIG. 15.

In some embodiments, one or more radio units 15200 that each include one or more transmitters 15220 and one or more receivers 15210 may be coupled to one or more antennas 15225. Radio units 15200 may communicate directly with hardware nodes 1530 via one or more appropriate network interfaces and may be used in combination with the virtual components to provide a virtual node with radio capabilities, such as a radio access node or a base station.

In some embodiments, some signalling can be effected with the use of control system 15230 which may alternatively be used for communication between the hardware nodes 1530 and radio units 15200.

According to certain embodiments, RS may be transmitted on non-anchor carriers. In an approved work item (WI) on Rel-14 enhancements for NB-IoT, one of the WI objectives is the following non-anchor PRB enhancements:

• Support transmission of PRACH on a non-anchor NB-IoT PRB [RAN2,RAN4]

• Support transmission of paging on a non-anchor NB-IoT PRB [RAN2,

RAN1,RAN3]

Due to paging and random access are supported on non-anchor carriers in Rel-14, one related issue is the presence of narrowband reference signals (NRSs) on a non-anchor carrier. To ensure a robust operation of the system as well as enhance the resource usage, the presence of the NRS on non-anchor carriers can be optimized. Thus, the presence of NRSs on a non-anchor carrier are discussed both from the network and UE point of view.

In Rel-13, NRS is defined and used to facilitate the UE DL measurement and the decoding of the various DL channels. A bit map of valid DL subframes is broadcast in NB-SIBl . On an anchor carrier, prior a NB-IoT UE device acquiring NB-SIBl, in standalone and guardband modes, the UE may assume NRSs are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS, and in inband mode, the UE may assume NRSs are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS. After acquiring NB-SIBl, the UE can assume NRSs are in all valid NB-IoT DL subframes in addition to the previous mentioned subframes in different operation modes.

In Rel-13, on a non-anchor carrier, as the non-anchor carrier is assigned to a NB-IoT UE device upon RRC setup, a bit map for valid subframes for the non-anchor carrier configuration is signaled upon RRC configuration to the UE. This is because, the anchor and non-anchor carriers may have different valid subframe configurations. Since in Rel-13, a NB-IoT UE device has no knowledge of the non-anchor carriers in RRC idle mode, it cannot make any assumptions on the NRS presence of the non-anchor carriers.

It may be observed that the Rel-13 decision related to the presence of NRS on non- anchor carriers only applies to RRC connected mode, and cannot be extend to cover the RRC idle case, n Rel-14, both paging and random access are introduced on the non-anchor carriers. Therefore, NRSs should be transmitted on a non-anchor carrier that supports paging and/or random access, even when there is no UEs are in RRC connected mode on the non-anchor carrier to facilitate the paging and random access activities of the NB-IoT UEs. However, the presence of the NRSs when there is no paging or random access response (RAR) on a non-anchor carrier both wastes the DL resources and prevents the dynamic resource sharing between legacy LTE and NB-IoT, if NB-IoT carriers are deployed inband.

The NRSs are used by the UEs for time/frequency tracking, channel estimation, and various measurements. In the following sections, the presence of the NRSs no non-anchor carriers is discussed case by case.

According to certain embodiments, NRS may be present on on-anchor carriers.

With regard to idle mode measurements, in RAN2#96, the following agreement was made regarding non-anchor paging and applies to idle mode UEs.

=> UE camps on and performs measurement on the anchor carrier.

Therefore, an NB-IoT UE should base on the quality of the anchor carrier to perform cell selection and re-selection. There are several reasons for this. First, since NB-IoT is designed for frequency reuse factor of 1, a typical scenario, at least for inband and guard-band deployment, is that the anchor carrier frequency is the same among neighboring cells, but it is not necessary for the non-anchor carriers. The load among neighboring cells varies, and therefore the amount of non-anchor carriers that are needed may not be the same. The non-anchor carrier configurations of the neighboring cells are not available to the UEs, and therefore, the UE can only perform measurement on the anchor carrier for the neighboring cells. Secondly, the anchor carriers are usually power boosted, which can give better measurement accuracy. In TS36.133, it is required that "the UE shall measure the NRSRP and NRSRQ level of the serving NB-IoT cell and evaluate the cell selection criterion S defined in for the serving NB-IoT cell at least every DRX cycle." Therefore, it is beneficial for the UE to wake up on the anchor carriers, to correct the time/frequency error, and performance the measurements.

Since the cell selection and re-selection criteria is based on the anchor carrier measurements, it is necessary that a UE wakes up on the anchor carrier, and performs measurement and frequency/time error correction.

In NB-IoT, invalid subframes (SFs) can be configured and there are no NRSs transmitted in the invalid SFs. The invalid SFs configurations are broadcast in the SI. When performing the idle mode measurement, the UE is neither required to acquire nor verify the SI of its serving cell nor the neighboring cells. Therefore, the UE has no knowledge regarding whether the configuration of its serving cell has changed, or the invalid SFs of the neighboring cells. Therefore, the can UE only make minimum assumption when it measures NRSRP and NRSSI. In the current NB-IoT specification regarding NRS, we have the following in TS 36.211 :

"When UE receives higher-layer parameter operationModelnfo indicating guardband or standalone,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS.

When UE receives higher-layer parameter operationModelnfo indicating inband-SamePCI or inband-DifferentPCI,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS"

Furthermore, as described in TS 36.214, that for the NRSRQ measurement, the measurement should be done in the same set of resource blocks for both NRSRP and NRSSI. The NRSRP is based on NRS measurement, and NRSSI is measured from all OFDM symbols of measurement SFs. However, there is no clear definition of measurement SFs in the current spec.

Notice that the non-serving cells can have a different operation mode compared to the serving cell of a UE, e.g., for the inter-frequency case. Hence, SFs #0, #4 and #9 not containing NSSS are the SFs that are the minimum assumption a UE can use for the

NRSRP/NRSSI measurements. Therefore, it is very important to clarify this in the RANI spec for the RRC IDLE mode measurements.

According to certain embodiments, it is proposed that RANI clarifies the anchor carrier idle mode measurement subframes to avoid mis-match behaviours between eNB and UE.

According to certain embodiments, it is proposed that for RRC IDLE intra-frequency, and RRC IDLE inter-frequency measurements that anchor carrier NRSRP/NRSRQ measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling SFN-l mod 2 = 0.

With respect to connected mode measurements, there is currently no support for RRC C ONNEC TED mode NRSRQ measurements. In RRC C ONNEC TED mode, a UE should perform radio link monitoring (RLM) to monitor the DL quality. Furthermore, for RRC CONNECTED mode measurements, it is beneficial from the UE power consumption point of view that a UE only monitors the downlink subframes that it should check, which can already guarantee good enough NRSRP measurements.

Based on the understanding of the sourcing company, the RAN4 specification requires that when (connected mode) DRX is used in the RRC CONNECTED state, the measurement period is in a number of DRX cycles (see section 8.14 in TS36.133). This implies that a UE in RRC CONNECTED state should only measure SFs of NPDCCH UE-specific search space and the SFs used for its NPDSCH transmission.

According to certain embodiments, it is proposed that for RRC CONNECTED mode measurements:

• If the UE is on an anchor carrier, then NRSRP/RLF measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling NF-1 mod 2 = 0 and the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in the NPDSCH subframes addressed to the UE.

· If the UE is on a non-anchor carrier, then NRSRP/RLF measurements shall be limited to the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in NPDSCH subframes addressed to the UE.

In Rel-14, paging is supported on non-anchor carriers. UEs are distributed according to UE ids on all carriers that support paging. Prior the paging occasion (PO) that a UE should monitor for the paging, the UE should wake up and correct its frequency and time errors due to that the local oscillator of the UE may have drifted. As mentioned before, since the idle mode measurement during DRX cycle should be performed on the anchor carrier, it is reasonable that the UE wakes up on the anchor carrier to perform time and frequency correction, and then listens to the paging if the paging carrier is a different carrier. According to previous studies in eMTC, the re-tuning time is around 2 OFDM symbols between two frequencies.

According to certain embodiments, it is feasible and potentially necessary for the UE to correct frequency and time error on the anchor carrier, and then listen to paging on the non-anchor carrier if configured. FIGURE 12 illustrates NRS around PO on non-anchor carriers.

FIGURE 13 illustrates NRS around RAR window on non-anchor carriers. As shown in FIGURE 13, if there is a paging message being transmitted to a UE, there is a fixed scheduling gap of 4 ms between the DCI carried in type-1 CSS and the NPDSCH carrying the paging message. If there is no paging that is being addressed to the UE, it is not necessary to transmit the NRS in the type-1 search space, since there is no risk of the UE misses the paging. If there is a paging being transmitted to a UE, then the NRS should be present at least within the SFs that carry the actual NPDCCH candidate and NPDSCH. In order to assist the UE perform cross SF channel estimation, it is also possible to have NRS presented some SFs prior of the PO and after the actual NPDCCH candidate. Similar arrangement can be made for the subsequence NPDSCH carrying the paging message as well. However, since there is only a 4 ms fixed scheduling gap between the actual NPDCCH candidate and the NPDSCH carrying the paging, the NRS should be transmitted within this 4 ms scheduling gap.

According to certain embodiments, if there is no non-anchor paging messaging addressed to any UE, it is not necessary to transmit NRS in the type-1 CSS, as there is no risk that the UE misses the paging.

In a particular embodiment, on a non-anchor carrier, if there is a paging messaging addressed to any UE, the NRSs may be transmitted in SFs, starting from Xi subframes prior to the first subframe of the type-1 CSS and until 4 subframes after the actual NPDCCH candidate. Xi, may be determined by the R value actual NPDCCH candidate.

In a particular embodiment, on a non-anchor carrier, a UE may assume that the NRS will be in SFs, starting from 4 subframes prior to the first subframe of the NPDSCH carrying paging messages and until Yi subframes after the NPDSCH. Yi may be determined by the length of NPDSCH.

During the previous RANI discussions, there was a concern that if there are no NRSs transmitted during in a PO when there is no paging, but immediately after that there might be UE initiated traffic, and the UE should access the network by initiating the random access procedure. In this case, it is preferred the UE keeps tracking the frequency and time on the non-anchor carrier even if there is no paging addressed to it. However, this is not the case. This is because, before initiating random access, it is required the UE to have a valid SI including the barring status, and the UE should verify the SI before initiating the random access. The UE should make sure it has valid SI info as well as barring is not enabled before access. Since the SI is only transmitted on the anchor carrier, the UE should listens to the anchor carrier to verify the SI and the barring status before initiating the random access.

According to certain embodiments, since the SI is only broadcast on the anchor carrier, it is necessary that the UE verifies the SI and barring status on the anchor carrier before initiating the random access.

For random access (RA) on non-anchor carriers, a UE first randomly selects an UL carrier that supports RA to send pre-amble, and then listens to RAR on a corresponding DL carrier as configured in the SI. FIGURE 2 illustrates the case of random access response on a non-anchor carrier.

After a UE sending an NPRACH pre-amble, the UE listens to a DL carrier configured for the RAR in the RAR window. The RAR window starts M SFs after the NPRACH, where M = 4 if the number of repetitions of NPRACH is smaller than 64, and M = 41 if the number of repetitions of NPRACH is larger than or equals to 64. The scheduling gap between the actual NPDCCH candidate scheduling the RAR message is configurable, depending on the Rmax of the search space, it can be up to 1024 ms. And X is the number of SFs between the NPDSCH carrying the RAR message and the beginning of Msg3, where X can be up to 64 ms. A type-2 CSS is used for the NPDCCH for RAR. Unlike type-1 CSS where an NPDCCH candidate always starts at the beginning of the search space, in the type-2 CSS the NPDCCH candidate can start in several places in a search space. Moreover, there can be several search space opportunities in a long RAR window. After a UE sending a NPRACH pre-amble, and if the UE does not receive any RAR, it will try to send the a new NPRACH pre-amble.

For UEs in bad coverage, the RAR window can be long, and therefore if there is no NRS when there is no RAR transmit to the UE, the UE may loss its time and frequency sync. Based on the RAN4 study of UL gap in NB-IoT, we can assume that the UE can keep its time and frequency synced for 256 ms without have NRSs, and beyond that the UE needs to acquire sync again. Therefore, in order to have a good trade off, the best solution is to transmit the NRS in the entire RAR window non non-anchor carriers, if the length of the RAR window is longer than a threshold, e.g., [256] ms.

According to certain embodiments, if the length of the configured RAR window is longer than [256] ms, a NB-IoT UE can assume the NRSs are transmitted in the entire RAR window.

Therefore, based on the above analysis and discussions, the following may be observed:

• The Rel-13 decision related to the presence of NRS on non-anchor carriers only applies to RRC connected mode, and cannot be extend to cover the RRC idle case.

It is feasible and necessary for the UE to correct frequency and time error on the anchor carrier, and then listens to paging on the non-anchor carrier if configured.

• If there is no non-anchor paging messaging addressed to any UE, it is not necessary to transmit NRS in the type-1 CSS, as there is no risk that the UE misses the paging.

• Since the SI is only broadcast on the anchor carrier, it is necessary that the UE verifies the SI and barring status on the anchor carrier before initiating the random access.

According to certain embodiments, the following may be proposed:

• Since the cell selection and re-selection criteria is based on the anchor carrier measurements, it is necessary that a UE wakes up on the anchor carrier, and performs measurement and frequency/time error correction.

• It is proposed that RANI clarifies the anchor carrier idle mode measurement subframes to avoid mis-match behaviours between eNB and UE.

• It is proposed that for RRC IDLE intra-frequency, and RRC IDLE inter- frequency measurements that anchor carrier NRSRP/NRSRQ measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and sub frame #9 in every 2nd radio frame not containing NSSS and fulfilling SFN-1 mod 2 = 0.

• It is proposed that for RRC CONNECTED mode measurements:

• If the UE is on an anchor carrier, then NRSRP/RLF measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling NF-1 mod 2 = 0 and the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in the NPDSCH subframes addressed to the UE.

• If the UE is on a non-anchor carrier, then NRSRP/RLF measurements shall be limited to the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in NPDSCH subframes addressed to the UE.

It is proposed that on a non-anchor carrier, if there is a paging messaging addressed to any UE, the NRSs are transmitted in SFs, starting from Xi subframes prior to the first subframe of the type-1 CSS and until 4 subframes after the actual NPDCCH candidate. Xi, may be determined by the R value actual NPDCCH candidate.

It is proposed that on a non-anchor carrier, a UE can assume that the NRS will be in SFs, starting from 4 subframes prior to the first subframe of the NPDSCH carrying paging messages and until Yi subframes after the NPDSCH. Yi may be determined by the length of NPDSCH.

If the length of the configured RAR window is longer than [256] ms, a NB- IoT UE can assume the NRSs are transmitted in the entire RAR window.

In Rel-14, with regard to enhancement for NB-IoT, a work item (RP-161901, "Revised work item proposal: Enhancements of NB-IoT", RAN#73, source Huawei, HiSilicon, 19 - 22 September, 2016) is approved to further enhance the performance of NB-IoT in terms of device power consumption, while maintaining the coverage and capacity of the NB-IoT network, and ultra-low UE cost NB-IoT.

In Rel-13 NRS is defined and used to facilitate the UE DL measurement, and the decoding of the various DL channels. A bit map of valid DL subframes, where NRSs are transmitted, is broadcast in NB-SIBl . On an anchor carrier, prior a NB-IoT UE device acquiring NB-SIB l, in standalone and guardband modes, the UE may assume NRSs are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS, and in inband mode, the UE may assume NRSs are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS. After acquiring NB-SIBl, the UE can assume NRSs are in all valid NB-IoT DL subframes in addition to the previous mentioned SFs in different operation modes.

As pointed out in Rl-1613071, "NRSRP and NRSRQ measurement in NB-IoT", source Ericsson, Reno, USA 14th - 18th November 2016, due to the operation mode and valid SF configurations of neighboring cells are not known to the UE, it is not clearly specified how the UE measurement is done in RRC IDLE and RRC C ONNEC TED modes. Therefore, both the eNB and UE can only infer certain behaviors of each other, which may cause problem in some cases, e.g., network optimization and UE cell selection or re-selection.

In Rl-1613071, the problems are discussed in detail, and certain clarifications in the spec are proposed to ensure a common understanding of the behaviors among eNB and UE.

Currently, in TS 36.214, the NRSRP and NRSRQ measurement for NB-IoT is given as follows:

5.1.26 Narrowband Reference Signal Received Power (NRSRP)

5.1.27 Narrowband Reference Signal Received Quality (NRSRQ)

As emphasized in the text above, for the NRSRQ measurement, the measurement should be done in the same set of resource blocks for both NRSRP and NRSSI. The NRSRP is based on NRS measurement, and NRSSI is measured from all OFDM symbols of measurement subframes. However, there is no clear definition of measurement subframes in the current spec. As mentioned above, as the UE has no knowledge about the invalid SF configurations as well as operation mode of the non-serving cells, the UE may have measured the invalid SFs that is used by the neighbouring non-serving cells.

In the current specification, there is no clear definition of measurement subframes for NRSRQ measurements. It is proposed that RANI clarifies the idle mode measurement subframes to avoid mis-match behaviours between eNB and UE.

In TS36.133, it is required that "the UE shall measure the NRSRP and NRSRQ level of the serving NB-IoT cell and evaluate the cell selection criterion S defined in for the serving NB-IoT cell at least every DRX cycle." Notice that the NRSRQ is defined as NRSRP/NRSSI. However, NRSRP is measured based on NRS, but NRSSI is based on any observed OFDM symbols of measurement SFs. Furthermore, it is required that for NRSRQ measurement, measurements of NRSRP and NRSSI shall be made over the same set of

resource blocks. The inband NB-IoT carrier is usually power boosted, but it is not required in the spec that the power should also be boosted in the invalid SFs. Therefore, for the neighbouring cell measurement, if the UE measure SFs #0, #4 and in subframes #9 not containing NSSS assuming the neighboring cell is in inband mode, and SFs #0, #1, #3, #4 and in subframes #9 not containing NSSS assuming the neighboring cell is in standalone or guardband mode. There is a risk that the SFs that the UE measure can be invalid SFs which is neither power boosted or contain NRS. Therefore, due to potential different invalid SF configurations and/or different operation modes among neighbouring cells, when performing measurement of non-serving cells, the UE may experience significant power fluctuation, which leads to wrong conclusion of the non-serving cell quality. This is very harmful in terms of cell re-selection.

Due to different invalid SF configurations and/or different operation modes of serving and non-serving cells, the UE may experience significant received power fluctuation for NRSRQ measurements, which leads to wrong conclusion of the non-serving cell quality that harms the cell re-selection.

More in details, in NB-IoT, invalid subframes (SFs) can be configured and there are no NRSs transmitted in the invalid SFs. The invalid SFs configurations are broadcast in the SI. When performing the idle model measurement, the UE is neither required to acquire nor verify the SI of its serving cell nor the neighboring cells. Therefore, the UE has no knowledge regarding whether the configuration of its serving cell has changed, or the invalid SFs of the neighboring cells. Therefore, the UE only can make minimum assumption when it measures NRSRP and NRSSI. In the current NB-IoT specification regarding NRS, we have the following in TS 36.211.

"When UE receives higher-layer parameter operationModelnfo indicating guardband or standalone,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #1, #3, #4 and in subframes #9 not containing NSSS.

When UE receives higher-layer parameter operationModelnfo indicating

inband-SamePCI or inband-DifferentPCI,

Before the UE obtains SystemlnformationBlockTypel-NB, the UE may assume narrowband reference signals are transmitted in subframes #0, #4 and in subframes #9 not containing NSSS."

Notice that the non-serving cells can have a different operation mode compared to the serving cell of a UE. Hence, SFs #0, #4 and #9 not containing NSSS are the SFs that are the minimum assumption a UE can use for the NRSRP/NRSSI measurements. Therefore, it is very important to clarify this in the RANI spec for the RRC IDLE mode measurements.

According to certain embodiments, it is proposed that for RRC IDLE intra-frequency, and RRC IDLE inter-frequency measurements that NRSRP/NRSRQ measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling SFN-1 mod 2 = 0.

Additionally, there is currently no support for RRC CONNECTED mode NRSRQ measurements. In RRC connected mode, the UE should perform radio link monitoring (RLM) by monitoring the DL quality. For RRC CONNECTED mode measurements, it is beneficial from the UE power consumption point of view that a UE only monitors the downlink subframes that it needs to check, which can already guarantee good enough NRSRP measurements.

Based on the understanding of the sourcing company, the RAN4 specification requires that when (connected mode) DRX is used in the RRC CONNECTED state, the measurement period is in a number of DRX cycles (see section 8.14 in TS36.133). This implies that a UE in RRC CONNECTED state should only measure SFs of NPDCCH UE-specific search space and the SFs used for its NPDSCH transmission.

According to certain embodiments, it is proposed that for RRC CONNECTED mode measurements:

• If the UE is on an anchor carrier, then NRSRP/RLF measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling NF-1 mod 2 = 0 and the subframes that

are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in the NPDSCH subframes addressed to the UE.

• If the UE is on a non-anchor carrier, then NRSRP/RLF measurements shall be limited to the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in NPDSCH subframes addressed to the UE.

Thus, based on the above analysis and discussions, the following are observed:

In the current specification, there is no clear definition of measurement subframes for NRSRQ measurements.

Due to different invalid SF configurations and/or different operation modes of serving and non-serving cells, the UE may experience significant received power fluctuation for NRSRQ measurements, which leads to wrong conclusion of the non-serving cell quality that harms the cell re-selection.

Thus, based on the above analysis and discussions, the following are observed:

It is proposed that RANI clarifies the idle mode measurement subframes to avoid mis-match behaviours between eNB and UE.

It is proposed that for RRC IDLE intra-frequency, and RRC IDLE inter- frequency measurements that NRSRP/NRSRQ measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling SFN-1 mod 2 = 0.

It is proposed that for RRC CONNECTED mode measurements:

• If the UE is on an anchor carrier, then NRSRP/RLF measurements shall be limited to NRS and/or all the OFDM symbols in subframes #0, #4, in every frame, and subframe #9 in every 2nd radio frame not containing NSSS and fulfilling NF-1 mod 2 = 0 and the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in the NPDSCH subframes addressed to the UE.

• If the UE is on a non-anchor carrier, then NRSRP/RLF measurements shall be limited to the subframes that are found in the configured UE specific search space (USS) on NPDCCHs addressed to the UE, and in NPDSCH subframes addressed to the UE.

RAN4 indicated the UE requirements for the acquisition delays of system information for REL-13 category NBl UEs in normal and enhanced coverage in R4-1610972, LS to RANI, RAN2 on eNB-IoT SI acquisition delay, Outgoing LS, Source: RAN4, To: RANI, RAN2, RAN4#81, REL-14 and R4-1610547, "Summary of NB-IoT SI acquisition delay simulation results," Intel Corporation, 3 GPP RAN4 #81, November 2016.

Table 1 RAN4 MIB and SIB acquisition observations [1], [2].

RAN4 observed the following:

• It is RAN4 understanding that the acquisition delay of the MIB-NB and SIB l- NB may become greater than or equal to the SIBl-NB modification boundary, and then the UE may have to re-acquire the MIB-NB.

• Since the SI acquisition delay values for NB-IoT in Table 1 are derived from baseband only simulations, the inclusion of RF impairment margin is expected to increase the delays for both coverage conditions.

• And RAN4 asks RAN2 (and RANI):

Action 1 : RAN4 respectfully asks RANI and RAN2 to consider future enhancements that can reduce the system information acquisition delay.

Action 2: RAN4 respectfully asks RANI and RAN2 to clarify whether the UE is expected to re-acquire the MIB-NB in those situations where the UE does not acquire the SIBl-NB before the end of the SIBl-NB modification period.

In the SI acquisition process, the UE first has to acquire MIB-NB to be able to acquire SIBl-NB. The MIB-NB, among other, contains the SFN and SIBl-NB scheduling info. After the UE has acquired SIBl-NB the UE can acquire the other SIBs. SIBl-NB contains the scheduling info of the other SIBs, and may also indicate which specific SI messages have changed. The systemlnfoValueTag in MIB-NB indicates if any of the SIBs other than MIB- NB/SIB14-NB/SIB16-NB have changed, i.e. is common for all the other SIBs. The SI acquisition process is depicted in FIGURE 14, which illustrate NB-SIB scheduling.

MasterlnformationBlock-NB (MIB-NB) scheduling is fixed with a periodicity of 640 ms and with LI repetitions in between, i.e. in every sub-frame 0. MIB-NB is sent on NPBCH. The MIB-NB contains:

• SFN (4 MSB bits)

• H-SFN (2 LSB bits)

• schedulinglnfoSIB 1

• systemlnfoValueTag (any SIB change other than MIB-NB/SIB 14-NB/SIB16- B)

• ab-Enabled (access barring activated/de-activated, SIB 14 acquisition) · operationModelnfo

Due to the 4 MSB bits of the SFN in MIB-NB, the MIB-NB content is changed every 640 ms. Besides the SFN the modification period equals 40.96 sec.

SIBl-NB scheduling is fixed with a periodicity of 2.56 sec. SIBl-NB is broadcasted in every second sub-frame 4. SIBl-NB is sent on DL-SCH. The number of NPDSCH repetitions are indicated in MIB-NB {schedulinglnfoSIB 1). SIBl-NB has a modification period of 40.96 sec, i.e. only after 40,96 sec the SIBl-NB content may change.

SIBl-NB contains important system information, e.g. cell access and cell re-selection info, which is typically not changed that frequently. However SIB l-NB also contains the 8 MSB bits of the hyper SFN, and is therefore updated every 4x10,24 = 40,96 sec. When H-SFN in SIBl-NB is updated, systemlnfoValueTag in MIB-NB is not updated. SIBl-NB also carries the scheduling information of the other SIBs and optionally an SI message specific value tag list, which can indicate which SI message has changed.

The UE can accumulate and combine SIBl-NB (NPDSCH repetitions) for up to 40,96 sec because the content does not change during that time.

Other SIBs

SIBs other than SIBl-NB are sent in Si-messages, which are sent on DL-SCH. An SI message may contain one or more SIBs, as indicated in the scheduling info in SIBl-NB.

The content of these other SIBs may change after the BCCH modification period. The BCCH modification period is larger or equal to 40.96s and indicated in SIB2-NB (modificationPeriodCoeff * defaultPagingCycle). SIB change (content and/or scheduling) is indicated by systemlnfoValueTag in MasterlnformationBlock-NB or systemlnfoValueTagSI in SystemlnformationBlockType 1 -NB .

The Access Barring parameters in SIB14-NB can change at any point in time (section 5.2.1.7 in 36.331), and such change does not impact systemlnfoValueTag in

MasterlnformationBlock-NB or systemlnfoValueTagSl in SystemlnformationBlockType 1-NB .

The content in the other SIBs is not expected to change frequently, except for SIB 14-NB during congestion periods.

UE requirements

In NB-IoT the UE is not required to accumulate several SI messages in parallel. But the UE may need to accumulate an SI message across multiple SI windows depending on coverage condition (section 5.2.1.2a in 36.331).

When camped on a cell the UE monitors for system information change. UE is notified of SI change through paging when the DRX cycle is smaller than the modification period. Otherwise the UE needs to have valid system information before access, i.e. before access the UE needs to check systemlnfoValueTag and ab-Enabled in MIB-NB. When the UE is in eDRX the UE is paged for any essential SI changes, such that the UE is not required to acquire SI changes when monitoring paging only.

When the UE re-selects to a cell, for which it does not have stored info, the UE needs to re-acquire the complete system information. This use case is more relevant for mobile UEs, than for stationary UEs. For mobile UEs the UE should be able to re-acquire the complete system information for the duration the UE is in the cell. The UE is reachable in cell after the UE has acquired SIB2-NB and has configured the paging channel.

Methods that may be considered for enhancing the performance of MIB-NB and SIB 1-NB acquisitions. Improved acquisition performance gives rise to a shorter acquisition time.

Specifically, the methods below may be considered,

1. Improved cross-subframe channel estimation

2. Accumulation of MIB-NB across multiple 640 ms TTI's

3. Accumulation of SIB 1-NB over multiple 2.56 seconds transmission periods.

FIGURE 15 shows the performance of MIB-NB acquisition for the in-band deployment. Specifically, FIGURE 15 illustrates MIB-NB acquisition performance in the Typical Urban channel with 1 Hz Doppler with acquisition time = 1920 ms. (in-band deployment with two NRS ports). The channel model used in the simulation is Typical Urban with 1 Hz Doppler. Here, the "keep-trying" method is used during a period of 1920 ms. This can be compared with the 2560 ms indicated in Table 1. The receiver accumulates and combines the NPBCH subframes according to the repetition pattern and code subblock structure of NPBCH for up to 640 ms, during which all 8 subblocks, each of 8 repetitions, are decoded jointly. If the receiver fails to check the CRC, it starts a new accumulation and combining process. The main point of FIGURE 15 is to illustrate that channel estimation may impact the MIB-NB acquisition performance very significantly. The three curves shown in FIGURE 15 correspond to three different channel estimators differentiated by different levels of cross-subframe channel estimation. The red curve is the performance without cross-subframe channel estimation. In this case, the channel coefficients are estimated based on NRS in only one subframe. The blue curve represents the performance achieved by jointly using NRS' s in 8 subframes for channel estimation, whereas the magenta curve represents the performance achieved by jointly using NRS's in 20 subframes for channel estimation. In the simulations, the NRSs are transmitted in all subframes not transmitting NPSS or NSSS. This is a possible situation for cell re-selection or RRC re-establishment if the UE has previously acquired SIB l-NB; and the SIB l-NB has indicated that the NRSs are transmitted in all subframes not transmitting NPSS or NSSS. Note however that during cell initial acquisition though, the UE can only assume that NRS' s are available in subframe #0, #4, and #9 not transmitting NSSS. In such scenarios, the subframes that can be assumed to have NRS' s are spread out in time. However, the UE can still use cross-subframe channel estimation in such scenarios. The SI acquisition performance is the most challenging for UEs in static channel due to lack of time diversity. However for these UEs, the channel coefficients also change very slowly, and thus having NRS's spread in time does not pose a problem for cross-subframe channel estimation. The SNR of -12 dB corresponds to the enhanced coverage scenario used in the RAN4 study R4-1610972. We see that with an 8-subframe cross-subframe channel estimator, MIB-NB acquisition performance after 1920 ms reaches 2% BLER.

According to certain embodiments, cross-subframe channel estimation improves MIB-NB acquisition performance significantly. Note however that the performance of the keep-trying method is far from optimal. A more sophisticate MIB-NB decoder can jointly decode the NBPCH signal across 640-ms TTI borders. Such a technique is described in [3], which recognizes that in most cases the only information content changes across NPBCH TTI borders is the SFN information. The SFN information changes follow a predictable pattern.

The feasibility of the joint decoding of MIB blocks differing only in an incremented SFN value has been demonstrated under AWGN conditions. The reduction in acquisition time compared to using the keep-trying method is substantial. In Rl-152190, PBCH repetition for MTC, Ericsson, RANl#80bis, it was shown that in extended coverage situation, the required acquisition time can be reduced by more than 80%.

According to certain embodiments, jointly decoding MIB blocks differing only in an incremented SFN value has been demonstrated to reduce the acquisition time significantly in an extended coverage scenario.

According to R4-1610972, SIBl-NB acquisition time dominates T SI for cell re-selection and for RRC re-establishment. SIBl-NB transmission in LI is illustrated in Figure 14. One SIBl-NB transmission period is 2.56 seconds, and within one SIBl-NB modification period there are 16 transmission periods. We believe the results in R4-1610972 were based on the "keep-trying" algorithm suggested in R4- 168805 which was agreed in RAN4#80bis. The "keep-trying" algorithm does not combine received signals over multiple SIBl-NB transmission periods. Instead, it decodes the received SIBl-NB signal in each transmission period separately. Note that the SIBl-NB information content remains the same across all the 16 transmission periods within the same SIBl-NB modification period. Therefore, it is straightforward for a UE to accumulate SIB l-NB across these transmission periods. Accumulation across multiple SIBl-NB transmission periods is expected to improve performance significantly. In addition, cross-subframe channel estimation is also expected to improve SIBl-NB acquisition performance significantly.

FIGURE 16 illustrates of SIBl-NB transmission in LI . SIBl-NB acquisition performance after 10.24 seconds at different SINR levels are shown in Table 1. SINR level of -12 dB corresponds to RAN4 extended coverage scenarios. It can be seen that without cross-subframe channel estimation and without SIBl-NB combining across multiple transmission periods gives rise to poor SIBl-NB acquisition performance after 10.24 acquisition time. In this case, the SIBl-NB decoder buffer is reset after a transmission period when the decoding is an error. The UE attempts SIBl-NB decoding with a fresh start in the subsequent SIBl-NB transmission period.

Table 2 demonstrates SIBl-NB acquisition error rate in the Typical Urban channel with 1 Hz Doppler. Acquisition time = 10.24 seconds, (in-band deployment with two NRS

ports):


It can be seen from Table 2 that combining across multiple transmission periods together with cross-subframe channel estimation (using NRS' s in 20 subframes) gives rise to very good SIB l-NB performance after 10.24 sec acquisition time, to be compared with 29.44 sec observed in Table 1. It is therefore suggested taht the UE could keep accumulating SIB l-NB across multiple transmission periods (within a 40.96 sec modification period) until it can decode SIB l -NB successfully.

According to certain embodiments, SIB l-NB acquisition performance can be significantly improved by combining across multiple SIB l -NB transmission periods within a SIBl -NB modification period and cross-subframe channel estimation.

Thus, the RAN4 finding that the acquisition performance for both could be poor for certain UE implementations is confirmed. A number of methods are described that can be used to significantly improve the acquisition performance of MTB-NB and SIB l-NB, according to certain embodiments. With these improvements, MTB-NB and SIB-NB acquisition performance is summarized in Table 3 :



The following observations can be made from the numerical results and discussions presented in this contribution.

• Cross-subframe channel estimation improves MIB-NB acquisition performance significantly.

• Jointly decoding MIB blocks differing only in an incremented SFN value has been demonstrated to reduce the acquisition time significantly in an extended coverage scenario.

• SIBl-NB acquisition performance can be significantly improved by combining across multiple SIBl-NB transmission periods within a SIBl-NB modification period and cross-subframe channel estimation.

These methods can be considered for UE implementations aiming for better SI acquisition performance, without any impact on RANI specifications. Therefore, it is proposed that no RANI action is needed to enhance the SI acquisition performance.

At RAN#75 it was agreed to start the Release 15 work item on Further NB-IoT enhancements. The objective on measurement accuracy improvements is to evaluate and if appropriate specify use of additional existing signals than NRS for RRM measurements, with associated RAN4 core requirements taking into account e.g. UE complexity, power

consumption, system capacity.

Items that may improve the RSRP measurement accuracy are discussed.

NB-IoT RSRP measurements for cell (re)selection, NPRACH CE level, and UL open loop power control are all based on the UE NRSRP measurement accuracy. Inaccurate NRSRP estimates will lead to inaccurate selection of cell, CE level and uplink power. In Release 13 NB-IoT NRSRP measurement requirements have been relaxed to the point where they tolerate measurement errors above ±10 dB. Discussions are now ongoing in RAN4 on UL power accuracy and a tolerance in the range of ±15 dB is under consideration. These high tolerances may impact the stability of NB-IoT system operation, especially in extended coverage, and lead to a waste of radio resources and dropped connections.

To address this critical issue RANI needs to consider means to improve the UE measurement accuracy. In idle mode it is natural to study the improvement potential from using the NPSS and NSSS signals in addition to the NRS for measuring RSRP.

According to certain embodiments, for idle mode measurements NPSS and NSSS may be considered in addition to the NRS for measuring RSRP.

It should also be considered to make more efficient use of the existing NRS transmission. A serving cell may e.g. broadcast neighboring cell information in terms of:

• NB-IoT mode of operation (inband, guardband, standalone),

• NRS antenna port configurations, and,

· valid sub-frame configuration.

This will allow the device to improve its neighbor cell NRS measurements which today typically can be assumed to be based on NRSs in subframes 0, 4 and 9 not containing NSSS. If possessing the above information for the neighboring cells the minimum set of measurement subframes can be expanded. For guardband and standalone NRS is e.g. always transmitted in subframes 0, 1, 3, 4, and 9 not containing NSSS.

According to certain embodiments, a NB-IoT UE may improve its neighbor cell RSRP measurements if knowing the neighbor cell mode of operation, antenna port configuration and valid sub-frame configuration. Thus, it is proposed that RANI sends a LS to RAN2 to inform them about this observation, and kindly asks them to take this into consideration. In a particular embodiment, RANI may send a LS to RAN2 to inform them

about the potential to improve NRSRP measurements in neighbor cells through the signaling of neighbor cell mode of operation, antenna port configuration and valid sub-frame configuration.

In Release 13, one reason for not allowing RSRP measurements on NPSS/NSSS was that different power may be configured on the NPSS/NSSS compared to the NRS. This may be because NPSS/NSSS is typically configured with a high output power to secure robust UE synchronization to these physical signals. Since NRSRP measurements are only permitted on the NRS, it's also natural to use the same high output level on these physical signals. Therefore, this as a blocking issue for specifying measurements on the NPSS/NSSS in addition to the NRS.

According to certain embodiments, it is expected that the NPSS/NSSS are configured with a similar, or the same, output power as the NRS. This should facilitate parallel NRSRP measurements on the NPSS/NSSS and NRS.

Also the measurement accuracy in connected mode is highly important. This to support efficient NPUSCH power control and robust RLF performance. Also in connected mode measurements on NPSS/NSSS may be considered to improve the UE performance.

According to certain embodiments, for connected mode measurements NPSS and NSSS may be considered in addition to the NRS for measuring RSRP. In a particular embodiment, RANI to send a LS to RAN2 to inform them about the potential to improve NRSRP measurements in neighbor cells through the signaling of neighbor cell mode of operation, antenna port configuration and valid sub-frame configuration.

According to certain embodiments, for idle mode measurements NPSS and NSSS may be considered in addition to the NRS for measuring RSRP.

According to certain embodiments, a NB-IoT UE may improve its neighbor cell RSRP measurements if knowing the neighbor cell mode of operation, antenna port configuration and valid sub-frame configuration.

According to certain embodiments, it is expected that the NPSS/NSSS are configured with a similar, or the same, output power as the NRS. This should facilitate parallel NRSRP measurements on the NPSS/NSSS and NRS.

According to certain embodiments, for connected mode measurements NPSS and

NSSS may be considered in addition to the NRS for measuring RSRP.

According to certain embodiments, a method in a wireless device may include:

• receiving, from a first network node, assistance information related to an NB- IoT operation mode associated with the network operating in a first cell;

• based on the assistance information related to the NB-IoT operation mode, determining a plurality of measurement subframes;

• performing measurements using the plurality of measurement subframes;

• optionally, the plurality of measurement subframes contain NRS and the NRS are used in performing the measurements;

• optionally, the plurality of measurement subframes contain at least one of NPSS and NSSS and the at least one of NPSS and NSSS are used in performing the measurements;

• optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation mode comprises the NB-IoT operation mode of the first network node;

• optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, and wherein the assistance information related to the NB-IoT operation mode comprises the NB-IoT operation mode of a neighboring node other than the first network node;

• optionally, the first network node is a serving node for the wireless device in a second cell and the assistance information related to the NB-IoT operation mode is received from the first network node, the assistance information being related to a second network node that is a serving node for the first cell, the second network node neighboring the second cell;

optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information identifies whether the NB-IoT operation mode of the first network node is the same as and/or different from the NB-IoT operation mode of the second network node;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the NB-IoT operation mode of the first network node;

optionally, the NB-IoT operation mode is selected from the group consisting of a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of carrier frequencies, and determining the plurality of measurement subframes containing NRS comprises assuming the NB-IoT is the same for a carrier frequency;

optionally, the assistance information related to the NB-IoT operation mode indicates whether the neighboring cell is in a same valid downlink subframe configuration as the serving cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies

optionally, performing the measurements comprises performing a NRSSI measurement from all OFDM symbols in the plurality of measurement subframes;

optionally, performing the measurements comprises performing a NRSRP measurement based on one or more OFDM symbols in the plurality of measurement subframes comprising NRS;

optionally, wherein the wireless device is in an idle mode when using the NRS in the measurement subframes to perform measurements;

optionally, the method may further include determining NRS are transmitted in measurement subframes associated with #0, #1 , #3, #4, and #9 based on the assistance information related to the NB-IoT operation mode;

optionally, the method may further include determining NRS are transmitted in measurement subframes associated with #0, #4, and #9 based on the assistance information related to the NB-IoT operation mode;

optionally, the assistance information related to the NB-IoT operation mode comprises the number of antenna ports used for transmission of the

Narrowband reference signals (NRSj;

optionally, the determining of plurality of measurement subframes are based on assistance information related to the NB-IoT operation mode, antenna port configurations, and valid sub-frame configuration;

optionally, determining a number of resource elements containing and/or comprising NRS based on assistance information related to the NB-IoT operation mode such as number of antenna ports used for transmission of the NRS;

• optionally, performing the measurements using the determined number of resource elements;

• optionally, the assistance information related to NB-IoT inband operation mode comprises configuration information for the cell-specific reference signals (CRS).

According to certain embodiments, a wireless device may include:

• processing circuitry, the processing circuitry configured to:

• receive, from a first network node, assistance information related to an NB-IoT operation mode associated with the network operating in a first cell;

• based on the assistance information related to the NB-IoT operation mode, determine a plurality of measurement subframes;

• performing measurements using the plurality of measurement subframes; · optionally, the plurality of measurement subframes contain NRS and the NRS are used in performing the measurements;

• optionally, the plurality of measurement subframes contain at least one of NPSS and NSSS and the at least one of the NPSS and NSSS are used in performing the measurements;

· optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation mode comprises the NB-IoT operation mode of the first network node;

• optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a

serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, and wherein the assistance information related to the NB-IoT operation mode comprises the NB-IoT operation mode of a neighboring node other than the first network node;

optionally, the first network node is a serving node for the wireless device in a second cell and the assistance information related to the NB-IoT operation mode is received from the first network node, the assistance information being related to a second network node that is a serving node for the first cell, the second network node neighboring the second cell;

optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information identifies whether the NB-IoT operation mode of the first network node is the same as and/or different from the NB-IoT operation mode of the second network node;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the NB-IoT operation mode of the first network node;

optionally, the NB-IoT operation mode is selected from the group consisting of a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of carrier frequencies, and determining the plurality of measurement subframes containing NRS comprises assuming the NB-IoT operation mode is the same for a carrier frequency;

optionally, the assistance information related to the NB-IoT operation mode indicates whether the neighboring cell is in a same valid downlink subframe configuration as the serving cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies

optionally, the processing circuitry may be configured to perform a NRSSI measurement from all OFDM symbols in the plurality of measurement subframes;

optionally, the processing circuitry may be configured to perform a NRSRP measurement based on one or more OFDM symbols in the plurality of measurement subframes comprising NRS;

optionally, wherein the wireless device is in an idle mode when using the NRS in the measurement subframes to perform measurements;

optionally, the processing circuitry may be configured to determine that NRS are transmitted in measurement subframes associated with #0, #1, #3, #4, and #9 based on the assistance information related to the NB-IoT operation mode; optionally, the processing circuitry may be configured to determine that NRS are transmitted in measurement subframes associated with #0, #4, and #9 based on the assistance information related to the NB-IoT operation mode; optionally, the assistance information related to the NB-IoT operation mode comprises the number of antenna ports used for transmission of the Narrowband reference signals (NRSj;

• optionally, the processing circuitry may be configured to determine a plurality of measurement subframes based on assistance information related to the NB- IoT operation mode, antenna port configurations, and valid sub-frame configuration;

• optionally, the processing circuitry may be configured to determine a number of resource elements containing and/or comprising NRS based on assistance information related to the NB-IoT operation mode such as number of antenna ports used for transmission of the NRS;

• optionally, the processing circuitry may be configured to perform the measurements using the determined number of resource elements;

• optionally, the assistance information related to NB-IoT inband operation mode comprises configuration information for the cell-specific reference signals (CRS).

According to certain embodiments, method by a first network node may include

• acquiring assistance information related to an NB-IoT operation mode in a first cell;

• transmitting the assistance information related to the NB-IoT operation mode to a wireless device for use in performing measurements in a plurality of measurement subframes;

• optionally, the plurality of measurement subframes contain NRS and the NRS are used in performing the measurements;

• optionally, the plurality of measurement subframes contain at least one of NPSS and NSSS and the at least one of NPSS and NSSS are used in performing the measurements;

• optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation mode is associated with the first network node;

optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation comprises the NB-IoT operation mode of a third network node that is a neighboring node to at least one of the first or the second network node;

optionally, the first network node is a serving node for the wireless device in a second cell, wherein the assistance information related to the NB-IoT operation mode is received from the first network node, wherein the assistance information is related to a second node associated with the first cell, the second node comprising a neighboring node of the first network node;

optionally, the assistance information identifies whether the NB-IoT operation mode associated with the first cell is the same as and/or different from that of a second network node that serves the wireless device;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the NB-IoT operation mode in the first cell; optionally, the NB-IoT operation mode is selected from the group consisting of a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of carrier frequencies, and determining the plurality of measurement subframes containing NRS comprises assuming the NB-IoT is the same for a carrier frequency;

• optionally, the assistance information related to the NB-IoT operation mode indicates whether the neighboring cell is in a same valid downlink subframe configuration as the serving cell;

• optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

• optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells;

• optionally, the information related to the NB-IoT operation mode comprises an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies

• optionally, the assistance information related to the NB-IoT operation mode comprises the number of antenna ports used for transmission of the Narrowband reference signals (NRSj;

• optionally, the transmitted assistance information includes NB-IoT operation mode, antenna port configurations, and valid sub-frame configuration;

• optionally, the assistance information related to NB-IoT inband operation mode comprises configuration information for the cell-specific reference signals (CRS).

According to certain embodiments, a network node may include:

• processing circuitry, the processing circuitry configured to:

• acquire assistance information related to an NB-IoT operation mode in a first cell;

• transmit the assistance information related to the NB-IoT operation mode to a wireless device for use in performing measurements in a plurality of measurement subframes;

optionally, the plurality of measurement subframes contain NRS and the NRS are used in performing the measurements;

optionally, the plurality of measurement subframes contain at least one of NPSS and NSSS and the at least one of NPSS and NSSS are used in performing the measurements;

optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation mode is associated with the first network node;

optionally, the wireless device is synchronized with the first network node, the first network node being a non-serving node for the wireless device and a neighboring node to a second network node, the second network node being a serving network node for the wireless device such that in order for the first network node to transition from a non-serving node to a serving node for the wireless device a handover must take place, wherein the assistance information related to the NB-IoT operation comprises the NB-IoT operation mode of a third network node that is a neighboring node to at least one of the first or the second network node;

optionally, the first network node is a serving node for the wireless device in a second cell, wherein the assistance information related to the NB-IoT operation mode is received from the first network node, wherein the assistance information is related to a second node associated with the first cell, the second node comprising a neighboring node of the first network node;

optionally, the assistance information identifies whether the NB-IoT operation mode associated with the first cell is the same as and/or different from that of a second network node that serves the wireless device;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the NB-IoT operation mode in the first cell; optionally, the NB-IoT operation mode is selected from the group consisting of a stand-alone operation mode, a guard-band operation mode, and an in-band operation mode;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of carrier frequencies, and determining the plurality of measurement subframes containing NRS comprises assuming the NB-IoT is the same for a carrier frequency;

optionally, the assistance information related to the NB-IoT operation mode indicates whether the neighboring cell is in a same valid downlink subframe configuration as the serving cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of the operation mode of the first cell and a valid downlink subframe configuration for the first cell;

optionally, the assistance information related to the NB-IoT operation mode comprises an explicit indication of a respective operation mode of each of a plurality of neighboring cells and a valid downlink subframe configuration for each of the neighboring cells;

optionally, the information related to the NB-IoT operation mode comprises an explicit indication of a valid downlink subframe configuration of each a plurality of carrier frequencies

optionally, the assistance information related to the NB-IoT operation mode comprises the number of antenna ports used for transmission of the Narrowband reference signals (NRSj;

optionally, the transmitted assistance information includes NB-IoT operation mode, antenna port configurations, and valid sub-frame configuration;

• optionally, the assistance information related to NB-IoT inband operation mode comprises configuration information for the cell-specific reference signals (CRS).

Certain embodiments of the present disclosure may provide one or more technical advantages. For example, certain embodiments provide wireless devices with information about the operation mode and/or valid invalid subframe configurations of neighboring cells. As such, a technical advantage may be that wireless devices are provided with more opportunities for neighboring cell measurements. Another technical advantage may that measurement accuracy may be improved. Still another technical advantage may be that measurement time is reduced. Certain embodiments may additionally or alternatively improve initial MIB acquisition.

Modifications, additions, or omissions may be made to the systems and apparatuses described herein without departing from the scope of the disclosure. The components of the systems and apparatuses may be integrated or separated. Moreover, the operations of the systems and apparatuses may be performed by more, fewer, or other components. Additionally, operations of the systems and apparatuses may be performed using any suitable logic comprising software, hardware, and/or other logic. As used in this document, "each" refers to each member of a set or each member of a subset of a set.

Modifications, additions, or omissions may be made to the methods described herein without departing from the scope of the disclosure. The methods may include more, fewer, or other steps. Additionally, steps may be performed in any suitable order.

Although this disclosure has been described in terms of certain embodiments, alterations and permutations of the embodiments will be apparent to those skilled in the art. Accordingly, the above description of the embodiments does not constrain this disclosure. Other changes, substitutions, and alterations are possible without departing from the spirit and scope of this disclosure, as defined by the following embodiments.