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1. WO2020114588 - EXTENDING COVERAGE OF A COMMUNICATION SYSTEM

Note: Text based on automatic Optical Character Recognition processes. Please use the PDF version for legal matters

[ EN ]

Extending Coverage of a Communication System

Field

The following embodiments relate to communication systems that may need to extend coverage dynamically.

Background

It is beneficial to have network functionality available as widely as possible. Therefore, network coverage is an important issue and having as wide network coverage as possible may be beneficial. Various methods of increasing network coverage are therefore of interest.

Brief description of the invention

According to an aspect, there is provided a method comprising: determining, by an apparatus, that data is to be exchanged between the apparatus and another apparatus, wherein the other apparatus does not have a wired backhaul connection; obtaining, by the apparatus, a time domain resource partitioning, wherein the time domain resource partitioning comprises a plurality of portions grouped to a first group and to a second group such that a first portion of the first group is available to a first downlink transmission and a first portion of the second group is available to a second downlink transmission; detecting, by the apparatus, if a channel is available for transmission; and if the channel is available for transmission, transmitting, by the apparatus, to the other apparatus according to the time domain resource partitioning.

According to another aspect, there is provided an apparatus, comprising: at least one processor, and at least one memory including a computer program code, wherein the at least one memory and the computer program code are configured, with the at least one processor, to cause the apparatus to: determine that data is to be exchanged between the apparatus and another apparatus, wherein the other apparatus does not have a wired backhaul connection; obtain a time domain resource partitioning, wherein the time domain resource partitioning comprises a plurality of portions grouped to a first group and to a second group such that a first portion of the first group is available to a first downlink transmission and a first portion of the second group is available to a second downlink transmission; detect if a channel is available for transmission; and if the channel is available for transmission, transmit to the other apparatus according to the time domain resource partitioning of the first group.

According to another aspect there is provided a computer program product readable by a computer and, when executed by the computer, configured to cause the computer to execute a computer process comprising: determining, by an apparatus, that data is to be exchanged between the apparatus and another apparatus, wherein the other apparatus does not have a wired backhaul connection; obtaining, by the apparatus, a time domain resource partitioning, wherein the time domain resource partitioning comprises a plurality of portions grouped to a first group and to a second group such that a first portion of the first group is available to a first downlink transmission and a first portion of the second group is available to a second downlink transmission; detecting, by the apparatus, if a channel is available for transmission; and if the channel is available for transmission, transmitting, by the apparatus, to the other apparatus according to the time domain resource partitioning.

According to another aspect there is provided an apparatus comprising means for determining, that data is to be exchanged between the apparatus and another apparatus, wherein the other apparatus does not have a wired backhaul connection; means for obtaining a time domain resource partitioning, wherein the time domain resource partitioning comprises a plurality of portions grouped to a first group and to a second group such that a first portion of the first group is available to a first downlink transmission and a first portion of the second group is available to a second downlink transmission; means for detecting if a channel is available for transmission; and

means for, if the channel is available for transmission, transmitting to the other apparatus according to the time domain resource partitioning.

According to another aspect there is provided a system comprising a first apparatus and a second apparatus and where the system is configured to:

determine that data is to be exchanged between the apparatus and another apparatus, wherein the other apparatus does not have a wired backhaul connection; obtain a time domain resource partitioning, wherein the time domain resource partitioning comprises a plurality of portions grouped to a first group and to a second group such that a first portion of the first group is available to a first downlink transmission and a first portion of the second group is available to a second downlink transmission; detect if a channel is available for transmission; and if the channel is available for transmission, transmit to the other apparatus according to the time domain resource partitioning.

List of drawings

In the following, the invention will be described in greater detail with reference to the embodiments and the accompanying drawings, in which

Figure 1 illustrates an example embodiment of a communication system. Figures 2a - 2c illustrate example embodiments of allocating resources within a communication system.

Figures 3a and 3b illustrate examples of cross-link interference.

Figures 4a-4e illustrate various links that are to be supported by time domain resources.

Figures 5a and 5b illustrate time domain resource partitioning.

Figures 6-8 are flow charts illustrating example embodiments.

Figure 9 illustrates an example embodiments of an apparatus.

Description of embodiments

The following embodiments are exemplifying. Although the specification may refer to "an", "one", or "some" embodiment(s) in several locations of the text, this does not necessarily mean that each reference is made to the same embodiment(s), or that a particular feature only applies to a single embodiment. Single features of different embodiments may also be combined to provide other embodiments.

Embodiments described herein may be implemented in a

communication system, such as in at least one of the following: Global System for Mobile Communications (GSM) or any other second generation cellular communication system, Universal Mobile Telecommunication System (UMTS, 3G) based on basic wideband-code division multiple access (W-CDMA), high-speed packet access (HSPA), Long Term Evolution (LTE), LTE-Advanced, a system based on IEEE 802.11 specifications, a system based on IEEE 802.15 specifications, and/or a fifth generation (5G) mobile or cellular communication system. The embodiments are not, however, restricted to the system given as an example but a person skilled in the art may apply the solution to other communication systems provided with necessary properties.

Figure 1 depicts examples of simplified system architectures only showing some elements and functional entities, all being logical units, whose implementation may differ from what is shown. The connections shown in Figure 1 are logical connections; the actual physical connections may be different. It is apparent to a person skilled in the art that the system typically comprises also other functions and structures than those shown in Figure 1. The example of Figure 1 shows a part of an exemplifying radio access network.

Figure 1 shows terminal devices 100 and 102 configured to be in a wireless connection on one or more communication channels in a cell with an access node (such as (e/g)NodeB) 104 providing the cell. The physical link from a terminal device to a (e/g)NodeB is called uplink or reverse link and the physical link from the (e/g)NodeB to the terminal device is called downlink or forward link. It should be appreciated that (e/g)NodeBs or their functionalities may be implemented by using any node, host, server or access point etc. entity suitable for such a usage.

A communication system typically comprises more than one (e/g)NodeB in which case the (e/g)NodeBs may also be configured to communicate with one another over links, wired or wireless, designed for the purpose. These links may be used for signalling purposes. The (e/g)NodeB is a computing device configured to control the radio resources of communication system it is coupled to. The NodeB may also be referred to as a base station, an access point or any other type of interfacing device including a relay station capable of operating in a wireless environment. The (e/g)NodeB includes or is coupled to transceivers. From the transceivers of the (e/g)NodeB, a connection is provided to an antenna unit that establishes bi directional radio links to user devices. The antenna unit may comprise a plurality of antennas or antenna elements. The (e/g)NodeB is further connected to core network 110 (CN or next generation core NGC). Depending on the system, the counterpart on the CN side can be a serving gateway (S-GW, routing and forwarding user data packets), packet data network gateway (P-GW), for providing connectivity of terminal devices (UEs) to external packet data networks, or mobile management entity (MME), etc.

The terminal device (also called UE, user equipment, user terminal, user device, etc.) illustrates one type of an apparatus to which resources on the air interface are allocated and assigned, and thus any feature described herein with a terminal device may be implemented with a corresponding apparatus, such as a relay node. An example of such a relay node is a layer 3 relay (self-backhauling relay) towards the base station. Another example of such a relay node is a layer 2 relay. Such a relay node may contain a terminal device part and a Distributed Unit (DU) part. A CU (centralized unit) may coordinate the DU operation via F1AP -interface for example.

The terminal device typically refers to a portable computing device that includes wireless mobile communication devices operating with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (mobile phone), smartphone, personal digital assistant (PDA), handset, device using a wireless modem (alarm or measurement device, etc.), laptop and/or touch screen computer, tablet, game console, notebook, and multimedia device. It should be appreciated that a user device may also be a nearly exclusive uplink only device, of which an example is a camera or video camera loading images or video clips to a network. A terminal device may also be a device having capability to operate in Internet of Things (loT) network which is a scenario in which objects are provided with the ability to transfer data over a network without requiring human-to-human or human-to-computer interaction. The terminal device may also utilise cloud. In some applications, a terminal device may comprise a small portable device with radio parts (such as a watch, earphones or eyeglasses) and the computation is carried out in the cloud. The terminal device (or in some embodiments a layer 3 relay node) is configured to perform one or more of user equipment functionalities.

Various techniques described herein may also be applied to a cyber physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the implementation and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, etc.) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems. Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals.

Additionally, although the apparatuses have been depicted as single entities, different units, processors and/or memory units (not all shown in Figure 1) may be implemented.

5G enables using multiple input - multiple output (MIMO) antennas, many more base stations or nodes than the LTE (a so-called small cell concept), including macro sites operating in co-operation with smaller stations and employing a variety of radio technologies depending on service needs, use cases and/or spectrum available. 5G mobile communications supports a wide range of use cases and related applications including video streaming, augmented reality, different ways of data sharing and various forms of machine type applications (such as (massive) machine-type communications (mMTC), including vehicular safety, different sensors and real-time control. 5G is expected to have multiple radio interfaces, namely below 6GHz, cmWave and mmWave, and also being integratable with existing legacy radio access technologies, such as the LTE. Integration with the LTE may be implemented, at least in the early phase, as a system, where macro coverage is provided by the LTE and 5G radio interface access comes from small cells by aggregation to the LTE. In other words, 5G is planned to support both inter-RAT operability (such as LTE-5G) and inter-RI operability (inter-radio interface operability, such as below 6GHz - cmWave, below 6GHz - cmWave - mmWave). One

of the concepts considered to be used in 5G networks is network slicing in which multiple independent and dedicated virtual sub-networks (network instances) may be created within the same infrastructure to run services that have different requirements on latency, reliability, throughput and mobility.

The current architecture in LTE networks is fully distributed in the radio and fully centralized in the core network. The low latency applications and services in 5G require to bring the content close to the radio which leads to local break out and multi-access edge computing (MEC). 5G enables analytics and knowledge generation to occur at the source of the data. This approach requires leveraging resources that may not be continuously connected to a network such as laptops, smartphones, tablets and sensors. MEC provides a distributed computing environment for application and service hosting. It also has the ability to store and process content in close proximity to cellular subscribers for faster response time. Edge computing covers a wide range of technologies such as wireless sensor networks, mobile data acquisition, mobile signature analysis, cooperative distributed peer-to-peer ad hoc networking and processing also classifiable as local cloud/fog computing and grid/mesh computing, dew computing, mobile edge computing, cloudlet, distributed data storage and retrieval, autonomic self-healing networks, remote cloud services, augmented and virtual reality, data caching, Internet of Things (massive connectivity and/or latency critical), critical communications (autonomous vehicles, traffic safety, real-time analytics, time-critical control, healthcare applications).

The communication system is also able to communicate with other networks, such as a public switched telephone network or the Internet 112, or utilise services provided by them. The communication network may also be able to support the usage of cloud services, for example at least part of core network operations may be carried out as a cloud service (this is depicted in Figure 1 by "cloud" 114). The communication system may also comprise a central control entity, or a like, providing facilities for networks of different operators to cooperate for example in spectrum sharing.

Edge cloud may be brought into radio access network (RAN) by utilizing

network function virtualization (NFV) and software defined networking (SDN). Using edge cloud may mean access node operations to be carried out, at least partly, in a server, host or node operationally coupled to a remote radio head or base station comprising radio parts. It is also possible that node operations will be distributed among a plurality of servers, nodes or hosts. Application of cloudRAN architecture enables RAN real time functions being carried out at the RAN side (in a distributed unit, DU 104) and non-real time functions being carried out in a centralized manner (in a centralized unit, CU 108).

It should also be understood that the distribution of labour between core network operations and base station operations may differ from that of the LTE or even be non-existent. Some other technology advancements probably to be used are Big Data and all-IP, which may change the way networks are being constructed and managed. 5G (or new radio, NR) networks are being designed to support multiple hierarchies, where MEC servers can be placed between the core and the base station or nodeB (gNB). It should be appreciated that MEC can be applied in 4G networks as well.

5G may also utilize satellite communication to enhance or complement the coverage of 5G service, for example by providing backhauling. Possible use cases are providing service continuity for machine-to-machine (M2M) or Internet of Things (IoT) devices or for passengers on board of vehicles, or ensuring service availability for critical communications, and future railway/maritime/aeronautical communications. Satellite communication may utilise geostationary earth orbit (GEO) satellite systems, but also low earth orbit (LEO) satellite systems, in particular mega-constellations (systems in which hundreds of (nano) satellites are deployed). Each satellite 106 in the mega-constellation may cover several satellite-enabled network entities that create on-ground cells. The on-ground cells may be created through an on-ground relay node 104 or by a gNB located on-ground or in a satellite.

It is to be noted that the depicted system is only an example of a part of a radio access system and in practice, the system may comprise a plurality of (e/g)NodeBs, the terminal device may have an access to a plurality of radio cells and the system may comprise also other apparatuses, such as physical layer relay nodes or other network elements, etc. At least one of the (e/g)NodeBs may be a Home(e/g)nodeB. Additionally, in a geographical area of a radio communication system a plurality of different kinds of radio cells as well as a plurality of radio cells may be provided. Radio cells may be macro cells (or umbrella cells) which are large cells, usually having a diameter of up to tens of kilometers, or smaller cells such as micro-, femto- or picocells. The (e/g)NodeBs of Figure 1 may provide any kind of these cells. A cellular radio system may be implemented as a multilayer network including several kinds of cells. Typically, in multilayer networks, one access node provides one kind of a cell or cells, and thus a plurality of (e/g)NodeBs are required to provide such a network structure.

For fulfilling the need for improving the deployment and performance of communication systems, the concept of "plug-and-play" (e/g)NodeBs has been introduced. Typically, a network which is able to use "plug-and-play" (e/g)Node Bs, includes, in addition to Home (e/g)NodeBs (H(e/g)nodeBs), a home node B gateway, or HNB-GW (not shown in Figure 1). A HNB Gateway (HNB-GW), which is typically installed within an operator’s network may aggregate traffic from a large number of HNBs back to a core network.

In a communication system the communication between a terminal device and an access node may be configured to happen such that uplink communication is allocated a certain frequency band to be used while the downlink has a different frequency band allocated to its communication. This is illustrated in Figure 2a. Because of the different frequency bands allocated to downlink (210) and uplink (220), downlink (210) and uplink (220) transmissions may happen simultaneously. This model is called frequency division duplexing, FDD. Transmission may be understood as transmittance of one or more data package between a terminal device and an access node. Transmission direction may be uplink or downlink direction. The downlink (210) and uplink (220) frequency bands may be separated by a frequency offset (215). As the downlink (210) and uplink (220) have separate frequency bands, transmissions in uplink and downlink directions do not interfere each other.

Another approach is technology called time division duplex, TDD,

introduced in Figure 2b. In this technology, uplink (230) and downlink (240) are using the same frequency band but are separated by time slots for using the frequency band allocated to them. In other words, while the frequency band is the same for uplink (230) and downlink (240) transmissions, they do not use the frequency band for transmissions simultaneously but are allocated separate time slots for using the frequency band. TDD thereby emulates full duplex communication over a half-duplex communication link. An advantage of TDD is that it may adapt well to a situation in which the data rates of uplink (230) and downlink (240) are asymmetrical. For example, if the amount of data to be transmitted in uplink (230) direction increases, more communication capacity may easily be allocated by dynamically allocating more time slots for uplink (230) transmission. Correspondingly, if the amount of data to be transmitted in the uplink (240) direction reduces, communication capacity may be freed from the uplink (240) transmission and allocated to downlink (240) transmission. The same applies when the amount of data to be transmitted in downlink (240) direction increases or decreases. Although not explicitly illustrated in Figure 2b, it is to be noted that it is possible to have guard period time slots between adjacent time slots. This may be advantageous if the adjacent time slots are allocated such that the transmission direction changes from uplink (230) to downlink (240) or vice versa. It is to be noted that the time slot allocations illustrated in Figure 2b are for illustrating purpose only. As the uplink (230) and downlink (240) transmissions take place in the same frequency band, TDD is suitable to be used in an unpaired spectrum which can be understood as spectrum that is allocated by the regulators as one block that is to be used for both uplink (230) and downlink (240).

To support the bi-directional communication, the time domain resources need to be allocated. Figure 2c illustrates an example partitioning of the time domain resources (250). The partitioning may also be known as a frame structure or it may also be known as channel occupancy time, COT, structure and it may be understood as a timing structure that supports bi-directional communication. The partitioning of the time domain resources may have a fixed overall duration or the overall duration may vary. Within the time domain resource partitioning (250), there

can be portions (260) that each have a duration. The portions (260) are available to uplink and downlink communication. The time domain resource partitioning (250), which may be understood as the allocation of the portions (260), to be used may be determined by an access node. In a cellular communication system, the time domain resource partitioning used by each access node may be the same thereby causing the same time domain resource partitioning to be used in all cells. It is to be noted that a portion (260) may in some example embodiments comprise one orthogonal frequency division multiplexing, OFDM, symbol while in some other example embodiments the portion (260) may correspond to a mini-slot, which may comprise e.g. 7, 4 or 2 OFDM symbols for example. In yet some other example embodiments, the portion (260) may correspond to a slot that may comprise 14 OFDM symbols. In some example embodiments, the time domain resource partitioning to be used is fixed and may be modified only in maintenance. In some alternative examples the time domain resource partitioning may be modified dynamically by the access node. Dynamic modification of the time domain resource partitioning in a cellular communication system may cause adjacent cells to use time domain resource partitionings that are structured differently from each other.

It is to be noted that TDD technology may be used not only in a cellular communication system but also in other communication systems such as wired, optical or acoustic communication systems.

If the time domain resource partitioning is dynamically modified, the transmission direction may be changed between uplink and downlink efficiently and thereby improve utilization of physical resources both in time and frequency domain. This may result in higher throughput and reduced latencies.

If adjacent cells have different time domain resource partitionings, probability of cross-link interference occurring increases. Figure 3a illustrates cross link interference that may occur between terminal devices. An access node (310) provides a cell within which a terminal device (320) is located. The terminal device (310) is however located close to the edge of the cell. An access node (330) provides another cell that is a neighbor cell to that provided by the access node (310). Terminal device (340) is located within the cell provided by the access node (330) such that it is close to the edge of the cell and adjacent to the terminal device (320). The cell provided by the access node (310) uses, in this example embodiment, a time domain resource partitioning (360) in which the first five portions are available to downlink transmission (315) and the rest of the portions are available to uplink transmission. The cell provided by the access node (330) on the other hand uses a time domain resource partitioning (370) in which the first four portions are available to downlink transmission and the rest of the portions, portions 5-10, are available to uplink transmission (335).

Because the time domain resource partitionings (360) and (370) are different, the portion 5 is available in the time domain resource partitioning (360) to downlink direction (315) but in the time domain resource partitioning (370) the portion 5 is available to uplink direction (335). As the frequency band used is the same for the terminal device (320) and the terminal device (340) and they are physically located close to each other, the simultaneous transmission to opposite directions using the same frequency band may cause interference called cross-link interference. If the terminal device (330) transmits a data packet in uplink direction (335) using the same frequency domain resources that are simultaneously used by the terminal device (320) to receive a data packet in downlink direction (315), it is possible that the packet received by the terminal device (320) cannot be successfully decoded due to an interference level. This cross-link interference (350) occurs between the terminal devices (320) and (340) and the closer the terminal devices are to each other while still being served by different access nodes, the higher the probability of the cross-link interference (350) occurring.

Figure 3a illustrated an example embodiment in which the cross-link interference occurred between terminal devices. Figure 3b illustrates another example embodiment in which cross-link interference occurs between two access nodes instead of two terminal devices. Like in Figure 3a, the access node (310) provides a cell within which the terminal device (320) is located. The time domain resource partitioning (360) is used by the access node (310). The access node (330) provides the cell in which the terminal device (340) is located and the time domain resource partitioning (370) is used by the access node (330). Therefore, during the portion five the access node (310) transmits a data packet to the terminal device (320) in the downlink direction (315). At the same time, using the same frequency band, the access node (330) receives in the uplink direction (335) a data packet from the terminal device (340). The data packet transmitted by the access node (310) may provide interference for the access node (330) in receiving of the data packet transmitted by the terminal device (340). This cross-link interference (380) thereby occurs between the access nodes (310) and (330).

For the purpose of achieving high-speed broadband communication, millimetre wave may be utilized. It is to be noted that also other frequency bands, such as unlicensed band at 5 GHZ could be used. Millimetre waves have short wavelengths that range from 10 millimeters to 1 millimeter. Millimeter wave, mmWave, spectrum is the frequency band between 30GHz and 300GHz. It may also be possible to use technologies defined for mmWave also below 30 GHz. For example, 28 GHz could be used. Some sub-bands of the mmWave frequency band may require a license from the regulators while other sub-bands may be unlicensed and thereby available without a license. Due to the wide frequency spectrum available and the high data speeds enabled, the mmWave is currently foreseen as a promising bandwidth to be used for 5G communication systems. Yet the short wavelength of mmWave causes high attenuation and the waves may be absorbed by gases in the atmosphere as well as attenuated by buildings and other obstacles in the environment.

Because of the high attenuation, the cell coverage achieved by one access node operating in the mmWave bandwidth is relatively small when comparing to the cell coverage of a 4G access node operating on a lower frequency band for example. In some examples, massive M1MO may be used as means to compensate the increased propagation loss. It is to be noted that regulatory rules may set a power spectral density limit which may limit the possibilities for improving the cell coverage by means of beamforming. This may be situation for example with regard to using an unlicensed band. Due to the relatively small cell coverage achieved by an access node, there may be a need for having more access nodes to cover a geographical area. It may be that not all such access nodes are equipped with a wired backhaul connection.

If an access node does not have a wired backhaul connection, the access node may utilize the wireless channel resources to connect to an access node that does have a wired backhaul connection or the access node may connect to another access node and the other access node is then connected to an access node with a wired backhaul connection. The access node may therefore be called as an integrated access and backhaul, IAB, node. The access node that does have the wired backhaul connection and to which the IAB node connects to for backhauling, may be called as a donor node. In the case of self-backhaul (a.k.a. integrated access and backhaul) the donor node uses the same wireless channel to serve terminal devices that are within a cell provided by the donor access node and to provide a wireless backhaul connection for the IAB node. Out-of-band relaying corresponds to a scenario without access terminal devices in a spectrum where the out-of-band relaying takes place. In some examples, a donor node may also have out-of-band relayed backhaul connection instead of a wired backhaul connection.

By having donor nodes and IAB nodes, the coverage of a communication system may be extended without having to equip all access nodes with a wired backhaul connection. This may be useful if the communication system operates using an unlicensed frequency band, like at or around 60 GHz for example. As the donor node (and/or CU) is configured to have an overall control of the radio resources, coverage extension may be achieved with minimal manual efforts and self configuration of the communication system may be enabled.

Figures 4a-4d illustrate how IAB node (420) may communicate with a donor node (410) and a terminal device (440) when operating under TDD half duplex constraint. It is to be noted that while in this example embodiment the donor node (410) is illustrated serving only one IAB node (420), in some other example embodiments there could be multiple IAB nodes the donor node (410) serves. In this example embodiment the donor node (410) also serves a terminal device (430), but in some other example embodiments, the donor node (410) could serve multiple terminal devices. Likewise, the IAB node (420) serves in this example embodiment only the terminal device (440), but in some other example embodiments, the IAB node (420) could serve multiple terminal devices and/or one or more access nodes.

Four separate time domain resources are to be available in the example embodiment illustrated by Figures 4a-4d. Figure 4a illustrates the backhaul downlink phase, Figure 4b illustrates the access downlink phase, Figure 4c illustrates the backhaul uplink phase and figure 4d illustrates the access uplink phase. In the phase of Figure 4a, the donor access node (410) transmits downlink data/control (415) to the terminal device (430) and downlink data/control (425) to the 1AB node (420). In the phase of Figure 4b, the donor node (410) continues to transmit downlink data/control (415) to the terminal device (430) but does not transmit downlink data/control to the 1AB node (420). Instead the 1AB node (420) transmits downlink data/control (445) to the terminal device (440). As can be seen from the Figures 4a and 4b, the transmitting phases of the access nodes, the donor node (410) and the 1AB node (420), are to be co-ordinated. The receiving phases of the access nodes, the donor node (410) and the 1AB node (420), are to be co-ordinated as well as can be seen from Figures 4c and 4d. In Figure 4c, the donor node (410) receives uplink/control data (455) from the terminal device (430) and uplink data/control (465) from the 1AB node (420). In Figure 4d the donor access node (410) continues to receive uplink data/control (455) from the terminal device (430) but no longer receives uplink data/control from the 1AB node (420). Instead, the 1AB node (420) receives uplink data/control (485) from the terminal device (440). Co-ordination of the transmitting and receiving phases of the access nodes enables the 1AB node (420) to listen to scheduling information from the donor node (410). Also, the co ordination enables the donor node (410) to listen to scheduling request information from the 1AB node (420).

Figure 4e illustrates an example embodiment of 1AB nodes and links between 1AB nodes and access terminal devices that are terminal devices having access links to the 1AB node. In the Figure 4e there is a backhaul downlink (4015) and a backhaul uplink (4025) between and 1AB node (4010) and a parent node (4020) which may be another 1AB node. The parent node (4020) provides backhaul links to the 1AB node (4010) but, in some example embodiments, it may not have a wired backhaul connection itself. Arrow (4100) illustrates the direction towards a donor node having a wired backhaul connection. Transmissions between the parent

node (4020) and the IAB node (4010) may be scheduled by the parent node (4020). Therefore, the link (4015) may also be called as parent backhaul downlink and the link (4025) may also be called as parent backhaul uplink.

In Figure 4e there is also link (4065) which is a backhaul downlink and link (4055) which is a backhaul uplink between the IAB node (4010) and another IAB node, that is a child node, (4040). The IAB node (4010) schedules transmission between the IAB node (4010) and the child node (4040). Therefore, the link (4065) may also be called as child backhaul downlink and the link (4055) may also be called as child backhaul uplink. Links (4055) and (4065) may also be called as child links.

In Figure 4e there is further link (4045) which is an access downlink and link (4035) which is an access uplink between the IAB node (4010) and a terminal device (4030). The IAB node (4010) schedules transmission between the IAB node (4010) and the terminal device (4030). Therefore, the link (4045) may also be called as child access downlink and the link (4035) may also be called as child access uplink. Links (4035) and (4045) may also be called as child links.

The IAB node (4010) comprises a mobile terminal, MT, functionality that facilitates reception of parent backhaul downlink and transmission of parent backhaul uplink. The IAB node (4010) further comprises data unit, DU, functionality which is separate from the MT functionality. The DU functionality facilitates e.g. transmission of child backhaul downlink and access link and reception of child backhaul uplink and access link.

The link (4015) is facilitated by downlink time resources and the link (4025) is facilitated by uplink time resources. In some example embodiments, there may further be flexible time resources that facilitate dynamic capacity allocation between downlink and uplink and between parent backhaul links and child links.

In the example embodiment of Figure 4e, the child links may have the following resources available: downlink time, uplink time, flexible time and not available time. The not available time resource is not to be used for communication on the DU child links. The time resources available for the child links may be categorized as hard or soft. Hard resources are such that corresponding time resource is always available for the DU child link and soft resources are such that availability of the corresponding time resource for the DU child link is explicitly and/or implicitly controlled by the parent node. In some example embodiments, flexible resources from MT point of view may be seen as soft resources from DU point of view.

In some example embodiments, the 1AB node (4010) operates according to centralized co-ordination. Yet in some other example embodiments, the 1AB node (4010) operates according to a distributed co-ordination. In the distributed co ordination the parent node (4020) is responsible for downlink and uplink scheduling for the parent links using the resources available. The parent node (4020) is also responsible for dynamic adaptation of available resources between parent and child links. In some example embodiments this is based on soft resources.

In some example embodiments, a CU may determine a semi-static resource configuration separately for each 1AB node. One resource configuration may then cover both MT and DU parts of the 1AB node. Alternatively, separate resource configuration is provided for MT and DU parts of an the 1AB node. It may also be possible for available resources to further comprise additional resource types. The parent node then allocates the available soft resources in the parent backhaul links to facilitate dynamic resource allocation between downlink and uplinks and also between parent and child links.

In order to detect when to start transmitting data, on the other hand, a concept called "listen before talk", LBT, may be utilized. In an example embodiment of the LBT, type 1 LBT, a device, such as an access node, may generate a random number N uniformly distributed over a contention window. Once the device has measured the channel to be vacant for N times or occasions, it may acquire the channel with transmission. In another example embodiment of the LTB, type 2 LTB, a device performs a single channel measurement in time interval, of 25 us for example, before acquiring the channel for transmission. Yet, the usage of LTB may cause uncertainty regarding the starting time for channel occupancy time, COT, which may conflict with the co-ordination of the transmitting and receiving phases of the devices. COT may be defined as a time interval when the device acquires the channel, or as a period that device reserves for transmissions. In some literature, transmission opportunity, TXOP, may be used for the same purpose. The duration of COT is bound to be equal or less than a maximum channel occupancy time. The maximum channel occupancy time may be predetermined by regulations or in system specifications. The device initiating the COT may share the COT with other device or devices. In other words, COT may contain transmissions from the device initiating the COT as well as transmissions sent to the initiating device from other devices. Within the COT there may be one or multiple switching points for the transmission directions controlled by the initiating device. A time domain resources partitioning may be done according to the maximum channel occupancy time.

Figure 5a illustrates an example embodiment that may be used to address the conflict mentioned above. In the example embodiment of Figure 5a, there is a donor node (510) that has a wired backhaul connection. The donor node (510) serves a terminal device (530) and an access node (520), which is an 1AB node that does not have a wired backhaul connection. In this example embodiment, the donor node (510) performs type 1 LBT before it transmits downlink data/control (515) to the terminal device (530) or downlink control/data (525) to the 1AB node (520). In this example embodiment, the 1AB node (520) also performs type 1 LBT before it transmits downlink data/control (535) to the terminal device (540). The terminal device (530) on the other hand performs type 2 LTB before transmitting uplink data/control (515) to the donor node (510). The terminal device (540) also performs type 2 LTB before transmitting uplink data/control (535) to the 1AB node (510) and the 1AB node (520) performs type 2 LTB before transmitting uplink data/control (525) to the donor node (510). It is to be noted that other types of LTB (including also an option without LBT) could alternatively be used.

In the example embodiment illustrated in Figure 5a, the time domain resources are divided into COT 1 (550) and COT 2 (560). This is illustrated by a time domain resource partitioning (580) used as a time structure for the COT. In the time domain resource partitioning (580) there is one switch point between COT1 (550) and COT 2 (560), but it is to be noted that in some other example embodiments, there could be multiple different switching points. The duration of the time domain resource partitioning (580), comprising COT1 (550) and COT2 (560), is less than or equal to maximum channel occupancy time. The starting time of the time domain resource partitioning is defined by COT starting time. The COT starting time is within a predefined (short) time interval after the last vacant channel measurement of LBT. In other words, the starting time of the time domain resource partitioning depends on the preceding LBT, and the time between consecutive time domain resource partitinings may be irregular. COT 1 (550) contains portions that are available to backhaul transmissions (515, 525) between the donor node (510) and the terminal device (530) and between the donor node (510) and the IAB node (520). The portions of COT 1 (550) are available such that downlink transmissions are scheduled first and after that uplink transmissions are scheduled. COT 2 (560) contains portions that are available to backhaul transmissions (515, 535) between the donor node (510) and the terminal device (530) and between the IAB node (520) and the terminal device (540). The portions of COT 2 (560) are available such that downlink transmissions are scheduled first and after that uplink transmissions are scheduled.

In the example embodiment of Figure 5a, the donor node (510) allocates the resources for different links, which in this example embodiment comprise links (515, 525 and 535) in both uplink and downlink directions. The donor node (510) may indicate the maximum allowed duration of COT 2 (560) explicitly using for example Group Common - Physical Downlink Control Channel (GC-PDCCH) (such as DCI format 2_0). The donor node (510) may also indicate a portion configuration to be used during the COT 2 (560) which may reduce the probability of cross-link interference occurring.

Figure 5b illustrates another example embodiment, which differs from the example embodiment of Figure 5a such that the IAB node (520) has a transmission link (545) to another access node (590) that does not have a wired backhaul connection either. Yet, the transmission link (545) between the IAB node (520) and the access node (590) enables a multi-hop extension possibility. In the example embodiment of Figure 5b the donor node (510) indicates one or more portions (5100) during which the transmission links (535 and 545) have a discontinuous reception, DRX, opportunity, which may enable saving of energy. The indication of the one or more portions (5100) is first received by the IAB node (520), which then forward the indication to the terminal device (540) and the access node (590). In other words, during the time one or more portions (5100) the terminal device (540) does not have to detect downlink transmission and the access node (590) may arrange the access link (545) during the one or more portions (5100) without having to detect downlink transmission (545). It should be noted that the one or more portions (5100) do not limit the maximum duration of the COT 1 (550).

In the example embodiments on Figures 5a and 5b it is also possible that the IAB node (520) determines that not all the portions available to uplink transmission (525) within the COT 1 (550) are needed. In such a situation the IAB node (520) may begin to perform LBT already before the boundary between the COT 1 (550) and the COT 2 (560).

It is to be noted that the example embodiments mentioned above are compatible with any LBT enhancements such as beam domain starting with omni-LBT followed by a single-shot LBT in the beam domain, beam specific type 1 LBT followed by a single-shot omni-direction LBT or type 1 LBT constructed from a combination of beam-specific and omni-directional LBT measurements.

Figure 6 is a flow chart that illustrates another example embodiment. In step S60, it is determined that data is to be transmitted between a first access node, that has a wired backhaul connection and a second access node, that does not have a wired backhaul connection. The first access node may also be called as a donor node. In some example embodiments, the first access node is a gNodeB. The second access node may also be called as IAB node or a relay node. Then in step S61, it is detected, by the first acces node if a channel is available for transmission. This detection may be done using for example type 1 LBT towards the second access node as described above. If the channel is not available, the first access node continues to detect the availability of the channel. If the channel is available, in step S62 it is determined, by first access node, a frame structure to be used. The frame structure may comprise a COT 1 and COT 2 as described above. The first access node may thereby determine the duration of COT 1 and COT 2, the portion allocations for downlink and uplink transmissions within the COT 1 and COT 2, the number of switching points between

COT 1 and COT 2 and possible time portions that may provide DRX opportunities to some terminal devices. Next, in step S63, the first access node indicates the determined time domain resource partitioning to the second access node. The indication may be done using GC-PDCCH for example. Then in step 64, the first access node transmits downlink data/control in accordance with the determined time domain resource partitioning to the second access node. The first access node also receives uplink data/control from the second access node according to the determined time domain resource partitioning. In some example embodiments, the first access node transmits downlink data/control also to a terminal device and receives uplink data/control from the terminal device. It is to be noted that the steps described above may be implemented in different order in some other example embodiments. It is also to be noted that the first access node may repeat the steps above each time it assigns new resources for an access link to an access node without a wired backhaul connection.

Figure 7 is a flow chart that illustrates a further example embodiment. In step S70 it is determined that data is to be exchanged between a first access node, that has a wired backhaul connection and a second access node, that does not have a wired backhaul connection. The first access node may also be called as a donor node. In some example embodiments, the first access node is a gNodeB. The second access node may also be called as 1AB node or a relay node. Next in step S71 the second access node receives information, from the first access node, regarding a frame structure to be used. The frame structure may comprise a COT 1 and COT 2 as described above. The first access node may thereby determine the duration of COT 1 and COT 2, the portion allocations for downlink and uplink transmissions within the COT 1 and COT 2, the number of switching points between COT 1 and COT 2 and possible time portions that may provide DRX opportunities to some terminal devices. Then in step S72 it is detected, by the second access node, start of downlink transmission by the first access node. Next, in step S73, the second access node receives from the first access node, downlink data/control according to the time domain resource partitioning and transmitting, by the second access node to the first access node, uplink data/control according to the frame structure. Step S73 may take place during the COT 1 of the time domain resource partitioning. Next in step S74, it is detected, by the second acces node if a channel is available for transmitting data/control to a terminal device. This may be done for example by using type 1 LTB towards the terminal device. If the channel is not available, the second access node continues to detect channel availability. If the channel is available, then, according to step S75, the second access node transmits downlink data to the terminal device according to the time domain resource partitioning and/or receives uplink data/control from the terminal device. Step S75 may take place during the COT 2 of the time domain resource partitioning.

Figure 8 illustrates yet another flow chart illustrating another example embodiment. In step S80, a terminal device detects start of downlink transmission by an access node without wired backhaul connection. The detection may be downlink burst detection for example. Next, in step S81, the terminal device receives downlink data/control from the access node and/or transmits uplink data/control to the access node. The transmission is performed according to a time domain resource partitioning determined by an access node with a wired backhaul connection. The time domain resource partitioning may comprise a COT 1 and COT 2 as described above. The first access node may thereby determine the duration of COT 1 and COT 2, the portion allocations for downlink and uplink transmissions within the COT 1 and COT 2, the number of switching points between COT 1 and COT 2 and possible time portions that may provide DRX opportunities to some terminal devices. Next, in step S82, the terminal device receives an indication, from the access node, to end detecting start of downlink transmission. In other words, the terminal device receives an indication of a DRX opportunity.

The example embodiments discussed above provide various advantages. Some of the advantages include providing a fully dynamic time domain resource partitioning between an access node and backhaul, operations of a relay or IAB node are fully controllable by a donor node, supporting of operation without cross-link interference, supporting multi-hop relaying and supporting power saving for terminal devices connected to IAB nodes.

The apparatus 900 of Figure 9 illustrates an example embodiment of an

apparatus that may be an access node or be comprised in an access node. The apparatus may be, for example, a circuitry or a chipset applicable to an access node to realize the described embodiments. The apparatus (900) may be an electronic device comprising one or more electronic circuitries. The apparatus (900) may comprise a communication control circuitry (910) such as at least one processor, and at least one memory (920) including a computer program code (software) (922) wherein the at least one memory and the computer program code (software) (922) are configured, with the at least one processor, to cause the apparatus (900) to carry out any one of the example embodiments of the access node described above.

The memory (920) may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, flash memory, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The memory may comprise a configuration database for storing configuration data. For example, the configuration database may store current neighbour cell list, and, in some example embodiments, structures of the frames used in the detected neighbour cells.

The apparatus (900) may further comprise a communication interface (930) comprising hardware and/or software for realizing communication connectivity according to one or more communication protocols. The communication interface (930) may provide the apparatus with radio communication capabilities to communicate in the cellular communication system. The communication interface may, for example, provide a radio interface to terminal devices. The apparatus (900) may further comprise another interface towards a core network such as the network coordinator apparatus and/or to the access nodes of the cellular communication system. The apparatus (900) may further comprise a scheduler (940) that is configured to allocate resources.

As used in this application, the term 'circuitry' refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and/or digital circuitry, and (b) combinations of circuits and software (and/or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s)/software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of 'circuitry' applies to all uses of this term in this application. As a further example, as used in this application, the term 'circuitry' would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and/or firmware. The term 'circuitry' would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processor integrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device. The above-described embodiments of the circuitry may also be considered as embodiments that provide means for carrying out the embodiments of the methods or processes described in this document.

The techniques and methods described herein may be implemented by various means. For example, these techniques may be implemented in hardware (one or more devices), firmware (one or more devices), software (one or more modules), or combinations thereof. For a hardware implementation, the apparatus(es) of embodiments may be implemented within one or more application-specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), graphics processing units (GPUs), processors, controllers, micro controllers, microprocessors, other electronic units designed to perform the functions described herein, or a combination thereof. For firmware or software, the implementation can be carried out through modules of at least one chipset (e.g. procedures, functions, and so on) that perform the functions described herein. The software codes may be stored in a memory unit and executed by processors. The memory unit may be implemented within the processor or externally to the processor. In the latter case, it can be communicatively coupled to the processor via various means, as is known in the art. Additionally, the components of the systems described herein may be rearranged and/or complemented by additional

components in order to facilitate the achievements of the various aspects, etc., described with regard thereto, and they are not limited to the precise configurations set forth in the given figures, as will be appreciated by one skilled in the art.

Embodiments as described may also be carried out in the form of a computer process defined by a computer program or portions thereof. Embodiments of the methods described in connection with Figures 2 to 8 may be carried out by executing at least one portion of a computer program comprising corresponding instructions. The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, which may be any entity or device capable of carrying the program. For example, the computer program may be stored on a computer program distribution medium readable by a computer or a processor. The computer program medium may be, for example but not limited to, a record medium, computer memory, read-only memory, electrical carrier signal, telecommunications signal, and software distribution package, for example. The computer program medium may be a non-transitory medium. Coding of software for carrying out the embodiments as shown and described is well within the scope of a person of ordinary skill in the art.

Even though the invention has been described above with reference to an example according to the accompanying drawings, it is clear that the invention is not restricted thereto but can be modified in several ways within the scope of the appended claims. Therefore, all words and expressions should be interpreted broadly and they are intended to illustrate, not to restrict, the embodiment. It will be obvious to a person skilled in the art that, as technology advances, the inventive concept can be implemented in various ways. Further, it is clear to a person skilled in the art that the described embodiments may, but are not required to, be combined with other embodiments in various ways.