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1. (WO2018007670) ADAPTIVE AUTOMATIC REPEAT REQUEST
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ADAPTIVE AUTOMATIC REPEAT REQUEST

FIELD

[0001] The present invention relates to managing error controlling in communication systems.

BACKGROUND

[0002] In communication networks, such as cellular and also non-cellular networks, tasks relating to managing communications are assigned to various network elements. In cellular networks, a radio-access network may comprise base stations and, in some technologies, base station controller or radio-access network controller nodes. Core networks, on the other hand, may comprise switches and various registers, for example.

[0003] Nodes in radio-access networks, RAN, are typically assigned tasks with scope relating locally to managing communications in a limited geographic area. Examples of such tasks include power control and dynamic resource management relating to specific wireless links. Core networks, CN, on the other hand may comprise nodes assigned with tasks that have broader geographic scope. Examples of such tasks include maintenance of subscriber registers and interfacing with further networks. Interfacing tasks may be referred to as providing a gateway functionality.

[0004] Cloud services comprise data services provided from data centres to remote clients. Examples of cloud services include data storage and data processing services. For example, consumers may store their digital photographs in a cloud storage, to keep them safe from theft, house fires and other unforeseen events. Likewise, cloud or grid computing may be used to meet occasional need for high computing power, to avoid a need to obtain costly computing hardware.

[0005] Information communicated over a communication network may develop bit errors in transit. This is particularly the case in wireless communication networks with mobile terminals, since a radio channel between a mobile terminal and a base station is susceptible to fading, reflections and Gaussian noise. Further, interference from other transmitters in the communication system may degenerate performance. In general, to minimize interference, communication should be performed at a lowest power that still produces acceptable performance. Bit errors may occur also in wired communication networks.

[0006] Error detection and correction may be employed using mathematical methods, known as coding. For example, a cyclic redundancy check, CRC, algorithm may be used to detect errors. A hash function may be employed to obtain a hash over a message payload, and the thus obtained hash may be compared to a hash received with the payload over the network. In case the hashes match, a degree of confidence may be assumed the payload does not contain errors. In addition to error detection, some coding methods have a limited ability to also correct bit errors. In general, the higher the error detection and correction capability, the higher is the associated coding overhead.

SUMMARY OF THE INVENTION

[0007] The invention is defined by the features of the independent claims. Some specific embodiments are defined in the dependent claims.

[0008] According to a first aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to participate in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, process information concerning a segmentation of the first ARQ layer, select a segment size of the second ARQ layer at least partly in dependence of the information, and modify the segment size of the second ARQ layer less frequently than once each transmission time interval.

[0009] Various embodiments of the first aspect may comprise at least one feature from the following bulleted list:

• the first ARQ layer comprises a hybrid ARQ layer

• the apparatus is configured to modify a segment size of the first ARQ layer more frequently than the segment size of the second ARQ layer

• the apparatus is configured to select the segment size of the second ARQ layer at least partly in dependence of both the information and further information

• the further information comprises at least one received status packet data unit

• the apparatus is configured to employ different segment sizes for the second ARQ layer for different connection legs in a multi-connectivity session

• the apparatus comprises or is comprised in a user equipment and the apparatus is configured to select the segment size of the second ARQ layer for the uplink direction

• the apparatus is configured to receive the information from at least one of the following: a base station, a radio access point and a central server

• the apparatus comprises or is comprised in a node that does not contain the first ARQ layer, and the apparatus is configured to select the segment size of the second ARQ layer for the downlink direction

• the apparatus is configured to receive the information from a base station or access point

• the information comprises at least one of the following: a segment size recommendation, a transport block size averaged over more than one transmission time interval, a smallest transport block size used during a time interval, a current radio channel condition and a predicted radio channel condition.

[0010] According to a second aspect of the present invention, there is provided a method comprising participating in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, processing information concerning a segmentation of the first ARQ layer, selecting a segment size of the second ARQ layer at least partly in dependence of the information, and modifying the segment size of the second ARQ layer less frequently than once each transmission time interval.

[0011] Various embodiments of the second aspect may comprise at least one feature corresponding to a feature from the preceding bulleted list laid out in connection with the first aspect.

[0012] According to a third aspect of the present invention, there is provided an apparatus comprising at least one processing core, at least one memory including computer program code, the at least one memory and the computer program code being configured to, with the at least one processing core, cause the apparatus at least to participate in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, prepare a recommendation concerning a segmentation of the second ARQ layer, and cause transmission of the recommendation to a node comprised in a radio access network. Additionally or alternatively, the node may be not comprising the first ARQ layer.

[0013] At least some embodiments of the third aspect may comprise at least one feature from the following bulleted list:

• the apparatus is configured to transmit retransmissions in accordance with the first ARQ layer

• the apparatus is configured to include in the recommendation information concerning at least one of the following: a transport block size averaged over more than one transmission time interval, a smallest transport block size used during a time interval, a current radio channel condition and a predicted radio channel condition.

[0014] According to a fourth aspect of the present invention, there is provided a method, comprising participating in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, preparing a recommendation concerning a segmentation of the second ARQ layer, and causing transmission of the recommendation to a node comprised in a radio access network. Additionally or alternatively, the node may be not comprising the first ARQ layer.

[0015] According to a fifth aspect of the present invention, there is provided an apparatus comprising means for participating in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, means for processing information concerning a segmentation of the first ARQ layer, means for selecting a segment size of the second ARQ layer at least partly in dependence of the information, and means for modifying the segment size of the second ARQ layer less frequently than once each transmission time interval.

[0016] An apparatus according the fifth aspect may further comprise means for performing the method according the second or fourth aspect.

[0017] According to a sixth aspect of the present invention, there is provided a non-transitory computer readable medium having stored thereon a set of computer readable instructions that, when executed by at least one processor, cause an apparatus to at least participate in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer, process information concerning a segmentation of the first ARQ layer, select a segment size of the second ARQ layer at least partly in dependence of the information, and modify the segment size of the second ARQ layer less frequently than once each transmission time interval.

[0018] According to a seventh aspect of the present invention, there is provided a computer program configured to cause a method in accordance with at least one the second and fourth aspects to be performed.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention;

[0020] FIGURE 2 illustrates an example system in accordance with at least some embodiments of the present invention;

[0021] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention;

[0022] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention;

[0023] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention, and

[0024] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention.

EMBODIMENTS

[0025] In a communication system with two automatic repeat request, ARQ, layers, an inner ARQ layer may be configured to adapt quickly to changing communication conditions, with an outer ARQ layer being configured to adapt slower, such that the outer layer may be controlled from a more remote node than the inner ARQ layer. In adapting a segment size of the outer ARQ layer, the node controlling the outer ARQ layer may use information obtained from a device that participates in adapting the inner ARQ layer. For example, information on a segment size of the inner ARQ layer may be used in selecting a segment size for the outer ARQ layer. In general, a segment size may be referred to as a packet data unit, PDU, size. In detail, a segment of the inner ARQ layer may be referred to as a PDU.

[0026] FIGURE 1 illustrates an example system in accordance with at least some embodiments of the present invention. The system comprises a user equipment, UE, 110, which may comprise a smartphone, mobile phone, tablet computer, laptop computer, desktop computer or indeed another kind of suitable device. UE 110 is in wireless communication with a base station 120, via wireless link 112. Base station is a term employed frequently when discussing radio nodes in cellular communication systems, however in the context of the present document it should be appreciated that also non-cellular systems are envisaged to benefit from embodiments of the present invention, and are not to be excluded by this terminological choice. Access point is a term often employed when discussing non-cellular radio nodes.

[0027] Base station 120, wireless link 112 and UE 110 are arranged to operate in accordance with a communication standard, to thereby obtain interoperability. For example, wideband code division multiple access, WCDMA, and long term evolution, LTE, and 5G are cellular communication standards. On the other hand, wireless local area network, WLAN, and worldwide interoperability for microwave access, WiMAX, are examples of non-cellular communication standards. While described herein as a wireless communication system, other embodiments of the invention may be implemented as wired communication systems. Wired communication standards include Ethernet, for example.

[0028] Base station 120 is coupled, via connection 123, with node 130. Node 130 may be comprised a node in a core network or a radio access network, for example. Connection 123 may comprise a wired connection, or an at least partly wireless connection. Connection 123 may be used to convey payload traffic between node 130 and base station 120. Node 130 is coupled with gateway 140 via connection 134, and gateway

140 is, in turn, coupled with further networks via connection 141. Connections 134 and

141 may comprise wire-line connections, for example. Wire-line connections may comprise Ethernet and/or fibre-optic connections, for example.

[0029] Via base station 120, node 130 and gateway 140, UE 110 may communicate with correspondent entities, which may be servers on the Internet, telephone endpoints in domestic or foreign locations or, for example, banking services in an corporate extranet.

[0030] An inner ARQ layer, or process, may be present over wireless link 112, the inner ARQ being managed by base station 120 and UE 110. The inner ARQ layer may comprise a hybrid-ARQ, HARQ, layer, for example. HARQ may comprise chase combining or incremental redundancy, for example. In chase combining, in case of a transmission error, a block is re-sent by the transmitter, which keeps the previous copy of the same block and soft combines the retransmission with the previous copy, to then attempt detection of the bits comprised in the block once more. In a sense, in chase combining the retransmission adds energy to each bit in the block. On the other hand, in incremental redundancy a retransmission may comprise additional information to assist the receiver in decoding the block correctly. For example, the additional information may comprise error-control coding bits derived from the payload, these bits not being present in the original transmission.

[0031] While the inner ARQ layer is expected to detect and correct most errors that occur over wireless link 112, occasionally it is inevitable that an error will occur on wireless link 112 that is missed by the inner ARQ layer. Examples of errors the inner ARQ layer may miss include ACK/NACK detection errors and CRC detection errors, which may cause a block error to go unnoticed. By ACK it is meant an indication that a PDU is correctly received, and by NACK it is meant an indication that a PDU is incorrectly received, requiring retransmission. The inner ARQ layer has a smaller delay in the sense that retransmissions of the inner ARQ layer take place sooner than retransmissions of an outer ARQ layer.

[0032] An outer ARQ layer is arranged to detect errors missed by, or incurred in, the inner ARQ layer. To such end, the outer ARQ layer may be associated with segments of its own, containing the same payload data and outer-ARQ coding. The outer-ARQ coding may comprise error detection coding, enabling detection of errors. An example of error detection coding is the aforementioned CRC. Thus, when the outer ARQ layer triggers a retransmission, the payload of the outer-ARQ segment where an error was detected is retransmitted, also through the inner ARQ layer. Segment sizes need not be identical in the inner ARQ layer and the outer ARQ layer. The segment sizes of the ARQ layers may be modified at least partly, and in some embodiments entirely, independently of each other.

[0033] The outer ARQ layer may be arranged between UE 110 and node 130, that is, the outer ARQ layer may be managed by node 130 and UE 110. In detail, ARQ management function 135 in node 130 may be configured to manage the outer ARQ layer in the downlink direction.

[0034] A segment size selection for an ARQ layer, be it the inner or the outer layer, represents a tradeoff. On the one hand, a small segment size creates overhead, since each segment requires a header. On the other hand, a large segment size lead to re-transmission of a larger quantity of payload in case an error is encountered. For example, where the outer ARQ layer has a large segment size, incorporating several inner ARQ layer PDUs, a single erroneous inner ARQ PDU in the outer ARQ segment causes a retransmission of several other inner ARQ PDUs, which are also in the outer ARQ segment that contains the error.

[0035] The segment sizes benefit from being adaptable, since higher layers use packets of different sizes, and an appropriately selected ARQ segment size may avoid a need to zero-pad ARQ segments, for example. Avoiding zero-padding increases communication efficiency, thus providing a technical advantage.

[0036] In general, in for example a LTE system, the network-side endpoint of the outer ARQ layer may be more easily placed in node 130, as opposed to base station 120, by re-segmenting and concatenating already in a first transmission, and fixing a first segmentation of packet data convergence protocol, PDCP, PDUs into acknowledged mode data, AMD, PDUs.

[0037] While adapting the segment size of the outer ARQ layer, in the downlink direction, in node 130 may be difficult for each segment separately, as described above overall it is useful to keep the segment size adaptable. One way to achieve this is to maintain adaptability the segment size but to modify it less frequently than is done in the inner ARQ layer. The inner ARQ layer benefits from being managed in base station 120 and UE 1 10, which both have an insight into the current state of a radio channel wireless link 112 propagates over. Thus, for the inner ARQ layer, the PDU size can be selected frequently, in response to changes in the radio channel.

[0038] In the outer ARQ layer, ARQ management function 135 may use internal and/or external information in selecting the outer ARQ layer segment size. External information may comprise information received from an entity managing the transmission medium, for example the medium access control, MAC, layer. In the downlink direction, ARQ management function 135 may thus, for example, receive information, for example a recommendation, from a MAC entity and/or inner ARQ entity in base station 120. ARQ management function 135 may receive this via an interface 125, for example. Interface 125 may comprise a CI or a Fronthaul, Fs, interface, for example. Interface 125 may proceed physically on connection 123, for example, or, alternatively, it may have a separate physical connection. Where interface 125 proceeds along connection 123, an advantage

may be obtained, wherein information communicated over interface 125 may be protected with the outer ARQ layer, as well.

[0039] The information obtained in ARQ management function 135 may comprise an average transport block size, TBS, the average being calculated over a certain time period or number of transport blocks communicated, for example. TBS may be considered another term for the inner ARQ layer PDU size, which is also known as the MAC PDU. The average TBS may be obtained using a filter, for example a recursive average with forgetting factor. Additionally or alternatively, the information may comprise a minimum TBS used in a time period. Additionally or alternatively, the information may comprise a percentile of the TBS in a time period. This may mean determining a TBS such that only a set percentage of TBSs used during a time period were smaller. Additionally or alternatively, the information may comprise a predicted radio channel condition or predicted traffic condition, which base station 120 may obtain, for example, from a channel estimator or from velocity information relating to UE 110. By adapting the segment size thus, an advantage is obtained in that byte-wise signalling is avoided, since byte-wise signalling may be triggered where re-segmentation events take place, that is, in case the segment sizes are incompatible between different layers. Byte-wise signalling increases a signalling overhead, which reduces communication efficiency and increases an overall energy per bit expended.

[0040] ARQ management function 135 may consider the information received over interface 125 as a recommendation, that is, it is not forced to use this recommendation, such that it still may take into account the current buffer status, for example. Larger segments may be created in case only few bytes would be left, and smaller packets may be created in case of small PDCP PDUs, such as Voice-over-IP, VoIP, or transmission control protocol, TCP, acknowledgements. The information could be incremental, for example, the MAC or ARQ entity in base station 120 may be configured to send short information updates on whether the produced segments were too small or too large.

[0041] ARQ management function 135 may consider the information received over interface 125 when selecting a segment size for the outer ARQ layer. While ARQ management function 135 may select the segment size for the outer ARQ layer in accordance with the received information, ARQ management function 135 may alternatively deviate from the received information. ARQ management function 135 may

alternatively, or in addition, use internal information available in ARQ management function 135 in selecting the segment size for the outer ARQ layer.

[0042] In case UE 110 is connected to multiple radio nodes, such as base station

120, ARQ management function 135 may receive information for selecting the segment size for the outer ARQ layer from several sources, the information from the several sources differing from source to source. In such a case, ARQ management function 135 may be configured to use different outer ARQ layer segment sizes depending on which leg the segments are sent to. In other words, ARQ management function 135 may manage the outer ARQ layer segment sizes of the legs independently of each other. Alternatively, ARQ management function 135 may be configured to apply the smallest segment size to all legs.

[0043] In the uplink direction, the outer ARQ layer is controlled in UE 110. UE 110 may employ PDU size information from the inner ARQ layer in selecting the uplink outer ARQ layer segment size, and/or radio channel information. The UE 110 has access to such information as it participates in radio channel adaptation, inner ARQ layer and the outer ARQ layer. As in the downlink case, the outer ARQ layer segment size may be adapted in UE 110 in a non-realtime manner, that is, less frequently than is done on the inner ARQ layer. Also for the uplink, UE 110 may receive information it may use as a recommendation for selecting the segment size. In detail, such information may be transmitted from the network to UE 110 over wireless link 112.

[0044] In the uplink direction, Status PDUs may be used, at least partly, by UE 101 to select the segment size for the outer ARQ layer. In detail, in case Status PDUs contain ACKs for full acknowledged mode data, AMD, PDUs this indicates the AMD PDUs have fitted in MAC PDUs. Responsive to this, UE 110 may increase the outer ARQ layer segment size. In case the Status PDUs comprise byte-wise AC/NACKs, this may indicate re-segmentation has occurred. The difference between start and end may be used as an indication of the segment size supported by MAC.

[0045] There may be a mismatch of the RLC segments and the instantaneously supported MAC PDU size, but the mismatch should be moderate. The following principles can be used to compensate for this mismatch:

[0046] 1) If the RLC segments are slightly too large, the MAC can squeeze them into MAC PDUs by using a slightly more aggressive modulation and coding scheme (or by choosing more resources, that is, the scheduler may take into account the size of the RLC segment).

[0047] 2) If the RLC segments are significantly larger, re-segmentation may be applied.

[0048] 3) If the RLC segments are too small, the MAC may automatically either select a smaller TBS, implying fewer resources or more conservative modulation and coding system, MCS, or it may concatenate multiple RLC segments into a single MAC PDU.

[0049] FIGURE 2 illustrates an example system in accordance with at least some embodiments of the present invention. Like numbering denotes like structure as in FIGURE 1. The system of FIGURE 2 differs from that illustrated in FIGURE 1 in that ARQ management function 135 is located in a cloud server 210. Cloud server 210 may be tasked with various other network management actions as well, and in particular it may host a large number of ARQ management functions for a number of active connections. Such active connections need not all traverse a same base station.

[0050] In general, in at least some embodiments, cloud server 210 of FIGURE 2, and node 130 of FIGURE 1 do not contain the inner ARQ layer. By this it may be meant, for example, that these nodes do not perform retransmissions of the inner ARQ layer.

[0051] FIGURE 3 illustrates an example apparatus capable of supporting at least some embodiments of the present invention. Illustrated is device 300, which may comprise, for example, a mobile communication device such as UE 110 of FIGURE 1 or FIGURE 2. In applicable parts, device 300 may correspond to node 130 or cloud server 210. Comprised in device 300 is processor 310, which may comprise, for example, a single- or multi-core processor wherein a single-core processor comprises one processing core and a multi-core processor comprises more than one processing core. Processor 310 may comprise more than one processor. A processing core may comprise, for example, a Cortex-A8 processing core manufactured by ARM Holdings or a Steamroller processing core produced by Advanced Micro Devices Corporation. Processor 310 may comprise at least one Qualcomm Snapdragon and/or Intel Atom processor. Processor 310 may

comprise at least one application- specific integrated circuit, ASIC. Processor 310 may comprise at least one field-programmable gate array, FPGA. Processor 310 may be means for performing method steps in device 300. Processor 310 may be configured, at least in part by computer instructions, to perform actions.

[0052] Device 300 may comprise memory 320. Memory 320 may comprise random-access memory and/or permanent memory. Memory 320 may comprise at least one RAM chip. Memory 320 may comprise solid-state, magnetic, optical and/or holographic memory, for example. Memory 320 may be at least in part accessible to processor 310. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be means for storing information. Memory 320 may comprise computer instructions that processor 310 is configured to execute. When computer instructions configured to cause processor 310 to perform certain actions are stored in memory 320, and device 300 overall is configured to run under the direction of processor 310 using computer instructions from memory 320, processor 310 and/or its at least one processing core may be considered to be configured to perform said certain actions. Memory 320 may be at least in part comprised in processor 310. Memory 320 may be at least in part external to device 300 but accessible to device 300.

[0053] Device 300 may comprise a transmitter 330. Device 300 may comprise a receiver 340. Transmitter 330 and receiver 340 may be configured to transmit and receive, respectively, information in accordance with at least one cellular or non-cellular standard. Transmitter 330 may comprise more than one transmitter. Receiver 340 may comprise more than one receiver. Transmitter 330 and/or receiver 340 may be configured to operate in accordance with global system for mobile communication, GSM, wideband code division multiple access, WCDMA, long term evolution, LTE, 5G, IS-95, wireless local area network, WLAN, Ethernet and/or worldwide interoperability for microwave access, WiMAX, standards, for example.

[0054] Device 300 may comprise a near-field communication, NFC, transceiver 350.

NFC transceiver 350 may support at least one NFC technology, such as NFC, Bluetooth, Wibree or similar technologies.

[0055] Device 300 may comprise user interface, UI, 360. UI 360 may comprise at least one of a display, a keyboard, a touchscreen, a vibrator arranged to signal to a user by causing device 300 to vibrate, a speaker and a microphone. A user may be able to operate device 300 via UI 360, for example to accept incoming telephone calls, to originate telephone calls or video calls, to browse the Internet, to manage digital files stored in memory 320 or on a cloud accessible via transmitter 330 and receiver 340, or via NFC transceiver 350, and/or to play games.

[0056] Device 300 may comprise or be arranged to accept a user identity module

370. User identity module 370 may comprise, for example, a subscriber identity module, SIM, card installable in device 300. A user identity module 370 may comprise information identifying a subscription of a user of device 300. A user identity module 370 may comprise cryptographic information usable to verify the identity of a user of device 300 and/or to facilitate encryption of communicated information and billing of the user of device 300 for communication effected via device 300.

[0057] Processor 310 may be furnished with a transmitter arranged to output information from processor 310, via electrical leads internal to device 300, to other devices comprised in device 300. Such a transmitter may comprise a serial bus transmitter arranged to, for example, output information via at least one electrical lead to memory 320 for storage therein. Alternatively to a serial bus, the transmitter may comprise a parallel bus transmitter. Likewise processor 310 may comprise a receiver arranged to receive information in processor 310, via electrical leads internal to device 300, from other devices comprised in device 300. Such a receiver may comprise a serial bus receiver arranged to, for example, receive information via at least one electrical lead from receiver 340 for processing in processor 310. Alternatively to a serial bus, the receiver may comprise a parallel bus receiver.

[0058] Device 300 may comprise further devices not illustrated in FIGURE 3. For example, where device 300 comprises a smartphone, it may comprise at least one digital camera. Some devices 300 may comprise a back-facing camera and a front-facing camera, wherein the back-facing camera may be intended for digital photography and the front-facing camera for video telephony. Device 300 may comprise a fingerprint sensor arranged to authenticate, at least in part, a user of device 300. In some embodiments, device 300 lacks at least one device described above. For example, where device 300 corresponds to node 130 or cloud server 210, it may lack NFC transceiver 350 and/or user identity module 370.

[0059] Processor 310, memory 320, transmitter 330, receiver 340, NFC transceiver

350, UI 360 and/or user identity module 370 may be interconnected by electrical leads internal to device 300 in a multitude of different ways. For example, each of the aforementioned devices may be separately connected to a master bus internal to device 300, to allow for the devices to exchange information. However, as the skilled person will appreciate, this is only one example and depending on the embodiment various ways of interconnecting at least two of the aforementioned devices may be selected without departing from the scope of the present invention.

[0060] FIGURE 4 illustrates signalling in accordance with at least some embodiments of the present invention. On the vertical axes are disposed, in terms of FIGURE 1 and FIGURE 2, on the left, ARQ management function 135, in the centre, base station 120 and on the right, UE 1 10.

[0061] Although illustrated as sequential, it is to be understood the phases of the illustrated process occur continuously or periodically in a continual process. 410 represents the outer ARQ layer, inside which the inner ARQ layer is disposed, labelled 420. UE 1 10 participates in both ARQ layers in the uplink direction. In the downlink, the outer ARQ layer is managed by ARQ management function 135 and the inner ARQ layer is managed by an entity in base station 120, for example a MAC entity therein.

[0062] Phase 430 represents communication between base station 120 and UE 110, over wireless link 112. This phase comprises, among others, adaptation of the inner ARQ layer PDU size, for example, as well as, optionally, adaptation to changing radio channel circumstances.

[0063] Phase 440 represents provision of information to ARQ management function

135, the information relating, for example, to TBS size and/or segment size or sizes in use over at least one of: the inner ARQ layer, MAC or RLC. Phase 450 represents ARQ management function 135 adapting the segment size of the outer ARQ layer. The adapting of phase 450 may occur at last partly in dependence of the information provided in phase 440.

[0064] FIGURE 5 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in UE 1 10, ARQ management function 135, or in a control device configured to control the functioning thereof, when implanted therein. In general, the method of FIGURE 5 may be performed in a node not comprised in a radio access network.

[0065] Phase 510 comprises participating in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer. Phase 520 comprises processing information concerning a segmentation of the first ARQ layer. Phase 530 comprises selecting a segment size of the second ARQ layer at least partly in dependence of the information. Phase 540 comprises modifying the segment size of the second ARQ layer less frequently than once each transmission time interval. The apparatus performing the method may be configured to not modify the segment size of the second ARQ layer at a transmission time interval, TTI, frequency.

[0066] FIGURE 6 is a flow graph of a method in accordance with at least some embodiments of the present invention. The phases of the illustrated method may be performed in base station 120, or in a control device configured to control the functioning thereof, when implanted therein.

[0067] Phase 610 comprises participating in communication of data, the communication employing a first automatic repeat request, ARQ, layer and a second ARQ layer, the first ARQ layer being arranged to operate with a smaller delay than the second ARQ layer, the second ARQ layer being arranged to correct errors occurring in the first ARQ layer. Phase 620 comprises preparing a recommendation concerning a segmentation of the second ARQ layer. Phase 630 comprises causing transmission of the recommendation to a node comprised in a radio access network. The transmission of phase 630 may be directed to a node comprised in a radio access network, for example, and/or a node that does not comprise the first ARQ layer.

[0068] It is to be understood that the embodiments of the invention disclosed are not limited to the particular structures, process steps, or materials disclosed herein, but are extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular embodiments only and is not intended to be limiting.

[0069] Reference throughout this specification to one embodiment or an

embodiment means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Where reference is made to a numerical value using a term such as, for example, about or substantially, the exact numerical value is also disclosed.

[0070] As used herein, a plurality of items, structural elements, compositional elements, and/or materials may be presented in a common list for convenience. However, these lists should be construed as though each member of the list is individually identified as a separate and unique member. Thus, no individual member of such list should be construed as a de facto equivalent of any other member of the same list solely based on their presentation in a common group without indications to the contrary. In addition, various embodiments and examples of the present invention may be referred to herein along with alternatives for the various components thereof. It is understood that such embodiments, examples, and alternatives are not to be construed as de facto equivalents of one another, but are to be considered as separate and autonomous representations of the present invention.

[0071] Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the preceding description, numerous specific details are provided, such as examples of lengths, widths, shapes, etc., to provide a thorough understanding of embodiments of the invention. One skilled in the relevant art will recognize, however, that the invention can be practiced without one or more of the specific details, or with other methods, components, materials, etc. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring aspects of the invention.

[0072] While the forgoing examples are illustrative of the principles of the present invention in one or more particular applications, it will be apparent to those of ordinary skill in the art that numerous modifications in form, usage and details of implementation can be made without the exercise of inventive faculty, and without departing from the principles and concepts of the invention. Accordingly, it is not intended that the invention be limited, except as by the claims set forth below.

[0073] The verbs "to comprise" and "to include" are used in this document as open

limitations that neither exclude nor require the existence of also un-recited features. The features recited in depending claims are mutually freely combinable unless otherwise explicitly stated. Furthermore, it is to be understood that the use of "a" or "an", that is, a singular form, throughout this document does not exclude a plurality.

INDUSTRIAL APPLICABILITY

[0074] At least some embodiments of the present invention find industrial application in communication systems, such as cellular and/or non-cellular communication systems.

ACRONYMS LIST

ABC Definition

ARQ automatic repeat request

CN core network

CRC cyclic redundancy check

HARQ hybrid-ARQ

LTE long term evolution

MAC medium access control

PDU packet data unit

RAN radio access network

RLC radio link control

TBS transport block size

UE user equipment

WCDMA wideband code division multiple access

WiMAX worldwide interoperability for microwave access

WLAN wireless local area network

REFERENCE SIGNS LIST

UE

Base station

Node

Gateway

ARQ management function

Wireless link

Interface

, 134, Connections

Cloud server

- 370 Structure of the device of FIGURE 3 - 450 Phases of FIGURE 4

- 530 Phases of FIGURE 5

- 630 Phases of FIGURE 6