Low overhead soft hybrid automatic repeat request and code block group based feedback

Abstract

Described herein is a User Equipment, UE, configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with a network node of a radio access network, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: receive, from the network node, a Transport Block, TB, comprising a plurality of Code Block Groups, CBGs; and for the received TB: determine, among the plurality of received CBGs, one or more CBGs that are received in error; determine a first bit string corresponding to a number of the one or more CBGs received in error; determine a second bit string indicating indices of the one or more CBGs received in error; determine a third bit string relating to a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits; concatenate the first bit string, the second bit string and the third bit string; and transmit the concatenated bit string to the network node as HARQ feedback for the received TB, wherein the UE is further caused to: determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the received TB, the lookup table comprises a corresponding codeword in the form of a bit string.

Description

Low Overhead Soft Hybrid Automatic Repeat Request and Code Block Group Based FeedbackTECHNOLOGY

[0001] The present disclosure relates to Hybrid Automatic Repeat Request, HARQ, feedback procedures, in particular to Code Block Group based soft HARQ feedback procedures.BACKGROUND

[0002] Any discussion of the background art throughout the specification should in no way be considered as an admission that such art is widely known or forms part of common general knowledge in the field.

[0003] When using soft Hybrid Automatic Repeat Request (HARQ) feedback instead of a single bit ACK / NACK response, the number of bits to report increases depending on the granularity of the soft decision. The initial expectation of this reporting is for each received Transport Block (TB). On the other hand, for some applications such as extended reality (XR), it is recommended to use Code Block Group (CBG) based feedback to improve the spectral efficiency.

[0004] However, combination of the soft feedback and per CBG report creates a large amount of overhead per transmission. For example, if an HARQ process is configured with 8 CBGs and soft HARQ of 4 bits per unit / per CBG, the HARQ feedback length will be 8*4=32 bits for each Downlink (DL) transmission which is significantly larger than single bit per TB report (legacy scheme). This excessive overhead hinders the applicability of the method.

[0005] Hence, there is a need to reduce the overhead of the combination of soft HARQ and CBG based feedback; in particular, there is a need to reduce the overhead in reporting a CBG based soft HARQ feedback; further, there is a need to provide resource-efficient retransmission of failed CBG(s) based on CBG based HARQ feedback; further, there is a need to improve applicability of CBG based HARQ feedback.SUMMARY

[0006] In accordance with a first aspect of the present disclosure, there is provided a User Equipment, UE, configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with a network node of a radio access network, comprising: at least one processor; andat least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: receive, from the network node, a Transport Block, TB, comprising a plurality of Code Block Groups, CBGs; and for the received TB: determine, among the plurality of received CBGs, one or more CBGs that are received in error; determine a first bit string corresponding to a number of the one or more CBGs received in error; determine a second bit string indicating indices of the one or more CBGs received in error; determine a third bit string relating to a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits; concatenate the first bit string, the second bit string and the third bit string; and transmit the concatenated bit string to the network node as HARQ feedback for the received TB, wherein the UE is further caused to: determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the received TB, the lookup table comprises a corresponding codeword in the form of a bit string.

[0007] In some examples, the UE is further caused to: calculate, for each possible number of CBGs in error in one TB, a corresponding error probability of having the each possible number of CBGs in error, based on following parameters: a selected target Block Error Rate, BLER, the number of CBGs in error and the total number of CBGs in the one TB; and determine for each calculated error probability, a corresponding codeword, wherein as the number of possible CBGs in error in the one TB increases, the corresponding error probability decreases and length of the corresponding codeword increases.

[0008] In some examples: if the number of the one or more CBGs received in error is greater than a first threshold, the UE is caused to determine a soft HARQ feedback for each of the plurality of CBGs in thereceived TB and transmit, to the network node, soft HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

[0009] In some examples: if the number of the one or more CBGs received in error is greater than a second threshold and / or if at least one CBG received in error has a soft HARQ feedback value lower than a third threshold, the UE is caused to determine a single bit HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, single bit HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

[0010] In some examples: if at least one CBG received in error has a soft HARQ feedback value lower than a fourth threshold, the UE is caused to determine a single bit HARQ feedback for the received TB and transmit, to the network node, the single bit feedback as HARQ feedback for the received TB.

[0011] In some examples: the third bit string comprises a soft HARQ feedback for one CBG received in error as a reference soft HARQ feedback, wherein the third bit string further comprises, for each of the remaining CBGs received in error, a difference between a soft HARQ feedback for the each remaining CBG received in error and the reference soft HARQ feedback.

[0012] In some examples, the UE is further caused to: receive, from the network node, a plurality of TBs, each TB comprising a plurality of CBGs; for each received TB, determine a corresponding HARQ feedback comprising a concatenated bit string; concatenate all HARQ feedbacks of the plurality of received TBs; and transmit the concatenated HARQ feedbacks to the network node as cumulative HARQ feedback for the plurality of received TBs.

[0013] In some examples, the UE is further caused to: generate the lookup table based on Hoffman coding.

[0014] In some examples, the UE is further caused to: receive the lookup table or an index of the lookup table from the network node, wherein the index of the lookup table corresponds to a BLER selected for the UE.

[0015] In some examples, the UE is further caused to: determine a fixed total size of the concatenated bit string; determine a first fixed size of the first bit string;determine a second size of the second bit string based on the first fixed size and the number of CBGs in error; and determine a third size of the third bit string based on the fixed total size, the first fixed size, the determined second size and the number of CBGs in error.

[0016] In some examples, the UE is further caused to downsample the soft HARQ feedbacks for all CBG received in error, to obtain the third bit string that has the determined third size.

[0017] In some examples, if the fixed total size is less than sum of the determined first fixed size and the determined second size, the UE is further caused to determine a single bit HARQ feedback for the received TB or for each received CBG as HARQ feedback for the received TB.

[0018] In accordance with a second aspect of the present disclosure, there is provided a network node of a radio access network, configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with a User Equipment, UE, the network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network node least to: configure the UE with an HARQ feedback format for a Tansport Block, TB, comprising a plurality of Code Block Groups, CBGs, wherein the format comprises a concatenation of a first bit string, a second bit string and a third bit string, wherein: the first bit string corresponds to a number of one or more CBGs in one TB that are received at the UE in error, the second bit string indicates indices of the one or more CBGs received in error; and the third bit string indicates a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits, wherein the network node is further caused to configure the UE to determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the one TB, the lookup table comprises a corresponding codeword in the form of a bit string.

[0019] In some examples, the network node is further caused to:calculate, for each possible number of CBGs in error in one TB, a corresponding error probability of having the each possible number of CBGs in error, based on following parameters: a selected target Block Error Rate, BLER, the number of CBGs in error and the total number of CBGs in the one TB; and determine for each calculated error probability, a corresponding codeword, wherein as the number of possible CBGs in error in the one TB increases, the corresponding error probability decreases and length of the corresponding codeword increases.

[0020] In some examples, the network node is further caused to configure with UE with a first threshold, and configure the UE to: after receiving a TB, if the number of the one or more CBGs received in error is greater than the first threshold, determine a soft HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, soft HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

[0021] In some examples, the network node is further caused to configure with UE with a second threshold and / or a third threshold, and configure the UE to: after receiving a TB, if the number of the one or more CBGs received in error is greater than the second threshold and / or if at least one received CBG in error has a soft HARQ feedback value lower than the third threshold, determine a single bit HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, single bit HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

[0022] In some examples, the network node is further caused to configure with UE with a fourth threshold, and configure the UE to: after receiving a TB, if at least one received CBG in error has a soft HARQ feedback value lower than a fourth threshold, determine a single bit HARQ feedback for the received TB and transmit, to the network node, the single bit feedback as HARQ feedback for the received TB.

[0023] In some examples: the third bit string comprises a soft HARQ feedback for one CBG received in error as a reference soft HARQ feedback, wherein the third bit string further comprises, for each of the remaining CBGs received in error, a difference between a soft HARQ feedback for the each remaining CBG received in error and the reference soft HARQ feedback.

[0024] In some examples, the network node is further caused to:transmit, to the UE, a plurality of TBs, each TB comprising a plurality of CBGs; for each transmitted TB, configure the UE with said HARQ feedback format comprising a concatenated bit string; and for said plurality of TBs, configure the UE with a cumulative HARQ feedback format comprising a concatenation of all HARQ feedbacks of the plurality of received TBs.

[0025] In some examples, the network node is further caused to: generate the lookup table based on Hoffman coding.

[0026] In some examples, the network node is further caused to: transmit to the UE the lookup table or an index of the lookup table, wherein the index of the lookup table corresponds to a BLER selected for the UE.

[0027] In some examples, the network node is further caused to: configure the UE to generate the lookup table.

[0028] In some examples, the network node is further caused to receive from the UE an HARQ feedback for one or more transmitted TBs, and determine the CBGs that are received at the UE in error and retransmit the determined CBGs in error.

[0029] In some examples, the network node is further caused to: configure the UE with a fixed total size of the concatenated bit string and a first fixed size of the first bit string; configure the UE to determine a second size of the second bit string based on the first fixed size and the number of CBGs in error; and configure the UE to determine a third size of the third bit string based on the fixed total size, the first fixed size, the determined second size and the number of CBGs in error, wherein the network node is further caused to configure the UE to downsample the soft HARQ feedbacks for all CBG received in error, to obtain the third bit string that has the determined third size.

[0030] In some examples, after receiving from the UE an HARQ feedback for one TB, the network node is further caused to: determine the number of CBGs received at the UE in error based on the first bit string included in the HARQ feedback; determine the second bit string based on the determined number of CBGs in error and the number of CBGs in the one TB; and determine the third bit string based on the first bit string, the second bit string and the fixed total size of the HARQ feedback of the one TB.

[0031] In accordance with a third aspect of the present disclosure, there is provided a system, comprising: a user equipment, UE, according to any one of the first aspect and its related examples, and a network node according to any one of the second aspect and its related examples, wherein the UE and the network node are configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with each other.

[0032] In accordance with a fourth aspect of the present disclosure, there is provided a method of a User Equipment, UE, that supports a Hybrid Automatic Repeat Request, HARQ, process when communicating with a network node of a radio access network, the method comprising: receiving, from the network node, a Transport Block, TB, comprising a plurality of Code Block Groups, CBGs; and for the received TB: determining, among the plurality of received CBGs, one or more CBGs that are received in error; determining a first bit string corresponding to a number of the one or more CBGs received in error; determining a second bit string indicating indices of the one or more CBGs received in error; determining a third bit string relating to a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits; concatenating the first bit string, the second bit string and the third bit string; and transmitting the concatenated bit string to the network node as HARQ feedback for the received TB, wherein the method further comprises: determining the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the received TB, the lookup table comprises a corresponding codeword in the form of a bit string.

[0033] In accordance with a fifth aspect of the present disclosure, there is provided a method of a network node that supports a Hybrid Automatic Repeat Request, HARQ, process when communicating with a User Equipment, UE, the method comprising:configuring the UE with an HARQ feedback format for a Tansport Block, TB, comprising a plurality of Code Block Groups, CBGs, wherein the format comprises a concatenation of a first bit string, a second bit string and a third bit string, wherein: the first bit string corresponds to a number of one or more CBGs in one TB that are received at the UE in error, the second bit string indicates indices of the one or more CBGs received in error; and the third bit string indicates a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits, wherein the method further comprises configuring the UE to determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the one TB, the lookup table comprises a corresponding codeword in the form of a bit string.

[0034] In accordance with a sixth aspect of the present disclosure, there is provided a computer program comprising instructions for causing an apparatus to perform the method according to the fourth aspect, or for causing an apparatus to perform the method according to the fifth aspect.

[0035] In accordance with a seventh aspect of the present disclosure, there is provided a memory storing computer readable instructions for causing an apparatus to perform the method according to the fourth aspect, or for causing an apparatus to perform the method according to the fifth aspect.

[0036] In addition, according to some other example embodiments, there is provided, for example, a computer program product for a wireless communication device comprising at least one processor, including software code portions for performing the respective steps disclosed in the present disclosure, when said product is run on the device. The computer program product may include a computer-readable medium on which said software code portions are stored. Furthermore, the computer program product may be directly loadable into the internal memory of the computer and / or transmittable via a network by means of at least one of upload, download and push procedures.

[0037] While some example embodiments will be described herein with particular reference to the above application, it will be appreciated that the present disclosure is not limited to such a field of use, and is applicable in broader contexts.

[0038] Notably, it is understood that methods according to the present disclosure relate to methods of operating the apparatuses according to the above example embodiments and variations thereof, and that respective statements made with regard to the apparatuses likewise apply to the corresponding methods, and vice versa, such that similar description may be omitted for the sake of conciseness. In addition, the above aspects may be combined in many ways, even if not explicitly disclosed. The skilled person will understand that these combinations of aspects and features / steps are possible unless it creates a contradiction which is explicitly excluded.

[0039] Implementations of the disclosed apparatuses may include using, but not limited to, one or more processor, one or more application specific integrated circuit (ASIC) and / or one or more field programmable gate array (FPGA). Implementations of the apparatus may also include using other conventional and / or customized hardware such as software programmable processors, such as graphics processing unit (GPU) processors.

[0040] Other and further example embodiments of the present disclosure will become apparent during the course of the following discussion and by reference to the accompanying drawings.BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Example embodiments of the disclosure will now be described, by way of example only, with reference to the accompanying drawings in which:

[0042] Figure 1 schematically illustrates an example of a lookup table generation procedure for providing a CBG based HARQ feedback according to an example embodiment of the present disclosure;

[0043] Figure 2 schematically illustrates an example of a signaling diagram for a CBG based HARQ feedback procedure according to an example embodiment of the present disclosure; and

[0044] Figure 3 schematically illustrates an example of a signaling diagram for a CBG based HARQ feedback procedure according to an example embodiment of the present disclosure.DESCRIPTION OF EXAMPLE EMBODIMENTS

[0045] In the following, different exemplifying embodiments will be described using, as an example of a communication network to which examples of embodiments may be applied, a communication network architecture based on 3 GPP standards for a communication network, such as a 5G / NR, without restricting the embodiments to such an architecture, however. It isapparent for a person skilled in the art that the embodiments may also be applied to other kinds of communication networks where mobile communication principles are integrated with a D2D (device-to-device) or V2X (vehicle to everything) configuration, such as SL (side link), e.g. Wi-Fi, worldwide interoperability for microwave access (WiMAX), Bluetooth®, personal communications services (PCS), ZigBee®, wideband code division multiple access (WCDMA), systems using ultra-wideband (UWB) technology, mobile ad-hoc networks (MANETs), wired access, etc. Furthermore, without loss of generality, the description of some examples of embodiments is related to a mobile communication network, but principles of the disclosure can be extended and applied to any other type of communication network, such as a wired communication network.

[0046] The following examples and embodiments are to be understood only as illustrative examples. Although the specification may refer to “an”, “one”, or “some” example(s) or embodiment(s) in several locations, this does not necessarily mean that each such reference is related to the same example(s) or embodiment(s), or that the feature only applies to a single example or embodiment. Single features of different embodiments may also be combined to provide other embodiments. Furthermore, terms like “comprising” and “including” should be understood as not limiting the described embodiments to consist of only those features that have been mentioned; such examples and embodiments may also contain features, structures, units, modules, etc., that have not been specifically mentioned.

[0047] A basic system architecture of a (tele)communication network including a mobile communication system where some examples of embodiments are applicable may include an architecture of one or more communication networks including wireless access network subsystem(s) and core network(s). Such an architecture may include one or more communication network control elements or functions, access network elements, radio access network elements, access service network gateways or base transceiver stations, such as a base station (BS), an access point (AP), a NodeB (NB), an eNB or a gNB, a distributed unit (DU) or a centralized / central unit (CU), which controls a respective coverage area or cell(s) and with which one or more communication stations such as communication elements or functions, like user devices or terminal devices, like a user equipment (UE), or another device having a similar function, such as a modem chipset, a chip, a module etc., which can also be part of a station, an element, a function or an application capable of conducting a communication, such as a UE, an element or function usable in a machine-to-machine communication architecture, or attached as a separate element to such an element, function or application on capable of conducting acommunication, or the like, are capable to communicate via one or more channels via one or more communication beams for transmitting several types of data in a plurality of access domains. Furthermore, core network elements or network functions, such as gateway network elements / functions, mobility management entities, a mobile switching center, servers, databases and the like may be included.

[0048] The following description may provide further details of alternatives, modifications and variances: a gNB comprises e.g., a node providing NR user plane and control plane protocol terminations towards the UE, and connected via the NG interface to the 5GC, e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 3.2 incorporated by reference.

[0049] A gNB Central Unit (gNB-CU) comprises e.g., a logical node hosting e.g., RRC, SDAP and PDCP protocols of the gNB or RRC and PDCP protocols of the en-gNB that controls the operation of one or more gNB-DUs. The gNB-CU terminates the Fl interface connected with the gNB-DU.

[0050] A gNB Distributed Unit (gNB-DU) comprises e.g., a logical node hosting e.g., RLC, MAC and PHY layers of the gNB or en-gNB, and its operation is partly controlled by the gNB- CU. One gNB-DU supports one or multiple cells. One cell is supported by only one gNB-DU. The gNB-DU terminates the Fl interface connected with the gNB-CU.

[0051] A gNB-CU-Control Plane (gNB-CU-CP) comprises e.g., a logical node hosting e.g., the RRC and the control plane part of the PDCP protocol of the gNB-CU for an en-gNB or a gNB. The gNB-CU-CP terminates the El interface connected with the gNB-CU-UP and the Fl-C interface connected with the gNB-DU.

[0052] A gNB-CU-User Plane (gNB-CU-UP) comprises e.g., a logical node hosting e.g., the user plane part of the PDCP protocol of the gNB-CU for an en-gNB, and the user plane part of the PDCP protocol and the SDAP protocol of the gNB-CU for a gNB. The gNB-CU-UP terminates the El interface connected with the gNB-CU-CP and the Fl-U interface connected with the gNB-DU, e.g., according to 3GPP TS 38.401 V16.6.0 (2021-07) section 3.1 incorporated by reference.

[0053] Different functional splits between the central and distributed unit are possible, e.g., called options:Option 1 (lA-like split):• The function split in this option is similar to the 1 A architecture in DC. RRC is in the central unit. PDCP, RLC, MAC, physical layer and RF are in the distributed unit.Option 2 (3C-like split):• The function split in this option is similar to the 3C architecture in DC. RRC and PDCP are in the central unit. RLC, MAC, physical layer and RF are in the distributed unit.Option 3 (intra RLC split):• Low RLC (partial function of RLC), MAC, physical layer and RF are in the distributed unit. PDCP and high RLC (the other partial function of RLC) are in the central unit.Option 4 (RLC-MAC split):• MAC, physical layer and RF are in the distributed unit. PDCP and RLC are in the central unit.Or else, e.g., according to 3GPP TR 38.801 V14.0.0 (2017-03) section 11 incorporated by reference.

[0054] A gNB supports different protocol layers, e.g., Layer 1 (LI) - physical layer.

[0055] The layer 2 (L2) of NR is split into the following sublayers: Medium Access Control (MAC), Radio Link Control (RLC), Packet Data Convergence Protocol (PDCP) and Service Data Adaptation Protocol (SDAP), where e.g. :• The physical layer offers to the MAC sublayer transport channels;• The MAC sublayer offers to the RLC sublayer logical channels;• The RLC sublayer offers to the PDCP sublayer RLC channels;• The PDCP sublayer offers to the SDAP sublayer radio bearers;• The SDAP sublayer offers to 5GC QoS flows;• Comp, refers to header compression and Segm. To segmentation;• Control channels include (BCCH, PCCH).

[0056] Layer 3 (L3) includes e.g., Radio Resource Control (RRC), e.g., according to 3GPP TS 38.300 V16.6.0 (2021-06) section 6 incorporated by reference.

[0057] A RAN (Radio Access Network) node or network node like e.g. a gNB, base station, gNB CU or gNB DU or parts thereof may be implemented using e.g. an apparatus with at least one processor and / or at least one memory (with computer-readable instructions (computer program)) configured to support and / or provision and / or process CU and / or DU related functionality and / or features, and / or at least one protocol (sub-)layer of a RAN (Radio Access Network), e.g. layer 2 and / or layer 3.

[0058] The gNB CU and gNB DU parts may e.g., be co-located or physically separated. The gNB DU may even be split further, e.g., into two parts, e.g., one including processing equipment and one including an antenna. A Central Unit (CU) may also be called BBU / REC / RCC / C- RAN / V-RAN, O-RAN, or part thereof. A Distributed Unit (DU) may also be called RRH / RRU / RE / RU, or part thereof. Hereinafter, in various example embodiments of the present disclosure, the CU-CP (or more generically, the CU) may also be referred to as a (first) network node that supports at least one of central unit control plane functionality or a layer 3 protocol of a radio access network; and similarly, the DU may be referred to as a (second) network node that supports at least one of distributed unit functionality or the layer 2 protocol of the radio access network.

[0059] A gNB-DU supports one or multiple cells, and could thus serve as e.g., a serving cell for a user equipment (UE).

[0060] A user equipment (UE) may include a wireless or mobile device, an apparatus with a radio interface to interact with a RAN (Radio Access Network), a smartphone, an in-vehicle apparatus, an loT device, a M2M device, or else. Such UE or apparatus may comprise: at least one processor; and at least one memory including computer program code; wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to perform certain operations, like e.g. RRC connection to the RAN. A UE is e.g., configured to generate a message (e.g., including a cell ID) to be transmitted via radio towards a RAN (e.g., to reach and communicate with a serving cell). A UE may generate and transmit and receive RRC messages containing one or more RRC PDUs (Packet Data Units).

[0061] The UE may have different states (e.g., according to 3GPP TS 38.331 V16.5.0 (2021- 06) sections 42.1 and 4.4, incorporated by reference).

[0062] A UE is e.g., either in RRC CONNECTED state or in RRC INACTIVE state when an RRC connection has been established.

[0063] In RRC CONNECTED state a UE may:• store the AS context;• transfer unicast data to / from the UE;• monitor control channels associated with the shared data channel to determine if data is scheduled for the data channel;• provide channel quality and feedback information;• perform neighboring cell measurements and measurement reporting.

[0064] The RRC protocol includes e.g. the following main functions:• RRC connection control;• measurement configuration and reporting;• establishment / modification / release of measurement configuration (e.g. intrafrequency, inter-frequency and inter-RAT measurements);• setup and release of measurement gaps;• measurement reporting.

[0065] The general functions and interconnections of the described elements and functions, which also depend on the actual network type, are known to those skilled in the art and described in corresponding specifications, so that a detailed description thereof may omitted herein for the sake of conciseness. However, it is to be noted that several additional network elements and signaling links may be employed for a communication to or from an element, function or application, like a communication endpoint, a communication network control element, such as a server, a gateway, a radio network controller, and other elements of the same or other communication networks besides those described in detail herein below.

[0066] A communication network architecture as being considered in examples of embodiments may also be able to communicate with other networks, such as a public switched telephone network or the Internet. The communication network may also be able to support the usage of cloud services for virtual network elements or functions thereof, wherein it is to be noted that the virtual network part of the telecommunication network can also be provided by non-cloud resources, e.g. an internal network or the like. It should be appreciated that network elements of an access system, of a core network etc., and / or respective functionalities may be implemented by using any node, host, server, access node or entity etc. being suitable for such a usage. Generally, a network function can be implemented either as a network element on a dedicated hardware, as a software instance running on a dedicated hardware, or as a virtualized function instantiated on an appropriate platform, e.g., a cloud infrastructure.

[0067] Furthermore, a network element, such as communication elements, like a UE, a terminal device, control elements or functions, such as access network elements, like a base station / BS, a gNB, a radio network controller, a core network control element or function, such as a gateway element, or other network elements or functions, as described herein, and any other elements, functions or applications may be implemented by software, e.g., by a computer program product for a computer, and / or by hardware. For executing their respective processing, correspondingly used devices, nodes, functions or network elements may includeseveral means, modules, units, components, etc. (not shown) which are required for control, processing and / or communication / signaling functionality. Such means, modules, units and components may include, for example, one or more processors or processor units including one or more processing portions for executing instructions and / or programs and / or for processing data, storage or memory units or means for storing instructions, programs and / or data, for serving as a work area of the processor or processing portion and the like (e.g. ROM, RAM, EEPROM, and the like), input or interface means for inputting data and instructions by software (e.g. floppy disc, CD-ROM, EEPROM, and the like), a user interface for providing monitor and manipulation possibilities to a user (e.g. a screen, a keyboard and the like), other interface or means for establishing links and / or connections under the control of the processor unit or portion (e.g. wired and wireless interface means, radio interface means including e.g. an antenna unit or the like, means for forming a radio communication part etc.) and the like, wherein respective means forming an interface, such as a radio communication part, can be also located on a remote site (e.g. a radio head or a radio station etc.). It is to be noted that in the present specification processing portions should not be only considered to represent physical portions of one or more processors, but may also be considered as a logical division of the referred processing tasks performed by one or more processors. It should be appreciated that according to some examples, a so-called “liquid” or flexible network concept may be employed where the operations and functionalities of a network element, a network function, or of another entity of the network, may be performed in different entities or functions, such as in a node, host or server, in a flexible manner. In other words, a “division of labor” between involved network elements, functions or entities may vary case by case.

[0068] The present disclosure generally seeks to reduce the overhead in reporting an HARQ feedback, in particular to reduce the overhead in providing a CBG based HARQ feedback, more particularly to reduce the overhead in providing a CBG based soft HARQ feedback.

[0069] The present disclosure further seeks to improve efficiency in applying soft HARQ feedback in combination with CBG based feedback. The present disclosure further seeks to provide efficient resource scheduling for retransmissions based on CBG based HARQ feedback.

[0070] The present disclosure further seeks to improve applicability of CBG based HARQ feedback.

[0071] Soft HARQ feedback schemes and CBG based feedback schemes are briefly discussed in the following.

[0072] Recent release-19 proposals for the extended reality (XR) topics hint towards using a so-called “soft HARQ”, where HARQ stands for hybrid automatic repeat request. For instance, in RP-231856 it is proposed to use some sort of soft-NACK / ACK for the HARQ feedback for the following use-cases according to RP-231856:

[0073] On the other hand, in RP -232429 it is also supported a more informative HARQ feedback, which has the following proposal:

[0074] Therein, HARQ feedback optimization is hinted to guide the gNB to enhance capacity and power saving gains.

[0075] However, sending a more detailed HARQ feedback does not come for free and requires sending more bits on the PUCCH, where the resources are not abundant. Therefore, smarter solutions are needed to really utilize the available resources for the HARQ feedback.

[0076] On the other hand, options with code block group (CBG)-based HARQ transmission is also supported by 5GNR. CBG-based transmission is specified in 3GPP TS 38.214, in section 5.1.7 entitled “Code block group based PDSCH transmission”. Details of HARQ feedback for CBG based transmissions are specified in 3GPP TS 38.213, section 9.1.1 “CBG-based HARQ- ACK codebook determination”. Aspects of CBG-based transmissions also appear in the MAC specification (3GPP TS 38.321).

[0077] The basic principle is that the TB is organized as into multiple Code Blocks (CBs). The maximum size of a CB is 8448 bits. The CBs are grouped into CBGs. For each received TB, the receiver provides feedback to indicate which CBGs are in error, and only the erroneously received CBGs are thereafter retransmitted by the transmitter.

[0078] For transmission of large TB sizes (as is the case for XR use cases as defined in 3GPP TR 38.838) such techniques are promising. Cases with up to 8 CBGs per TB are supported by current NR specs. More generally, the maximum number of CBGs per TB is configurable as M 6 {2, 4, 6, 8} for the Physical Downlink Shared Channel (PDSCH).

[0079] In view of the above, it is proposed in accordance with the present disclosure a combination of soft HARQ feedback and CBG based feedback. In particular, it is proposed in accordance with the present disclosure compression methods, based on the probabilistic properties of CBGs in a TB, to reduce the overhead of the HARQ feedback, while still capturing CBG and soft-HARQ information for the purpose of being able to schedule more resourceefficient HARQ retransmissions with just the right amount of information, not more, and not less than what is needed. It is also proposed in accordance with the present disclosure CBG based HARQ feedback methods that are more applicable to different error scenarios.

[0080] The key idea in accordance with the present disclosure is to divide the HARQ feedback into three main parts: (i) reporting the number of CBGs in error; (ii) index of the erroneous CBGs and (iii) soft feedback of the corresponding CBGs. By utilizing a coding principle, the average feedback length can be reduced significantly. For instance, with a configuration that allows N=3 bits for each soft feedback, and has 4 CBGs per TB M=4 and maintains a BLER target of 10%:Feedback size without compression = M*N =12 bitsCompressed feedback size - 1.68 bits < 2 bits

[0081] Therefore, the overhead reduction gain can be calculated as 12 / 1.68 - 700% from using the proposed methods, i.e., a significant benefit.

[0082] References are now made to the figures. In particular, it is to be noted that identical or like reference numbers used in the figures of the present disclosure may, unless indicated otherwise, indicate identical or like elements, such that repeated description thereof may be omitted for reasons of conciseness.

[0083] In an exemplary embodiment, it is proposed in accordance with the present disclosure a three-level HARQ feedback scheme, wherein as an example Huffman codes are used to compress the information. The algorithm is composed of two stages: 1. Look up table generation 2. HARQ feedback generation.Stage 1. Lookup table generation

[0084] This step is preferably only done once, and the resulting tables can be stored for future use. The lookup table may be generated by the gNB and / or the UE. A simpler way is to include the tables in the specifications where each table is assigned with an index. The gNB may use the index to let the UE know which lookup table should be used for HARQ feedback process.

[0085] In order to create the tables, two parameters are required: Block Error Rate (BLER) target set for the Channel quality indicator (CQI) reporting (for instance, it could be 0.1 or lOe- 5 depending to the configuration in 5G specifications), and number of CBGs per TB (for instance, M e {2, 4, 6, 8}).

[0086] Indexation of the lookup table may therefore be based on a selected BLER. That is, depending on the selected BLER value, a corresponding lookup table is generated for that BLER value.

[0087] The table can be created using the algorithm below:

[0088] Numerical example: Assume a scenario where the BLER target is 10% and there are4 CBGs per TB; and assume that the Hoffmann coding scheme is applied. As illustrated inFigure 1 and following the steps above, for each possible number of CBGs in error, a corresponding codeword is generated:

[0089] As shown in Figure 1, events a to e correspond respectively to having 0, 1, ..., all CBGs received in error, wherein the events are arranged following a non-increasing order of the probabilities of those events, i.e., pa> pb>. . . > pe. The tree is constructed by connecting two child nodes of e and d to a new parent node nl with probability of pnl= pe+ the treeis further constructed by connecting the now two child nodes of d and nl to a new parent node n2 with probability of pn2= Pd + pnl; the previous constructing steps are repeated until all events shrink into 2 events and the tree is completed, i.e., until obtaining even n4 in Figure 1. The codewords for events a to e are obtained by assigning to the constructed tree a 0 (or 1) to each branch on top (e.g., on top of the respective new parent nodes nl to n4) and assign a 1 (or 0) to each branch on the bottom (e.g., on the bottom of the respective new parent nodes nl to n4). The codeword includes the assigned values on the branches, starting from the new parent event / node n4 on the top of the constructed tree, to the corresponding CBG error event, via the new parent events / nodes in between.

[0090] In the above example, the resulting look up table has the following shape:

[0091] In the above table, as the number of possible CBGs in error in one received TB increases, the corresponding error probability decreases and length of the corresponding codeword increases. Therefore, in accordance with the present disclosure, since the least possible event (i.e., the largest possible number of CBGs in error) is attributed a longest codeword, whereas the most possible event (i.e., the smallest possible number of CBGs in error) is attributed a shortest codeword, the overall / average length / size of bits used in the feedback is reduced.

[0092] It is assumed in step 1 (Error Probability calculation) the identical and independent distributions (iid) for the CBG error rate, which is done only to reduce computational complexity in case the table should be generated on the fly (not specified or hard-coded). Other assumptions can be considered as well, e.g. correlated errors, and it will not impact the lookup table generation algorithm and the possibility of the HARQ feedback compression. The main assumption in the table design is that the failure probability of 0 CBGs > 1 failed CBG > 2failed CBGs >. . . > all CBGs in the one received TB failed. As long as this condition holds, the table design is valid.Stage 2. HARQ feedback generation

[0093] This stage is done per PDSCH transmission at the UE side where a step-by-step procedure may be as follows:

[0094] After configuring the lookup table (stage 1) via a semi-static signaling, e.g. RRC signaling, the UE is able to report the number of failed CBGs Ci. For C2 and C3 the procedure is as follows: in C2 the UE reports the index of the failed CBGs and in C3 the value of the soft- HARQ feedback (or a function of it) for the indicated CBG in C2 is reported.

[0095] In the present disclosure, the soft feedback is referred to as multibit feedback instead of a single bit ACK / NACK feedback, where the multibit string guides the gNB on how far the receiver was on decoding the block (TB or CBG). One way to generate such a bit string can be the use of soft output of the decoder (LDPC decoder for the case of 5G) that shows the soft estimate of the decoder for block with a failed CRC check.

[0096] The details for the steps at the UE side to form F as Ci, C2 and C3 can be specified in the physical layer specification in TS 38.213 in section 9.1.1 on CBG-based HARQ-ACK codebook determination, where an additional subsection can cover the cases of soft feedback combined with CBG based HARQ.

[0097] Three numerical cases:• All CBGs are received correctly => feedback: 0 (with probability 90%)• Only CBG2 is in error with feedback of 1100 => Ci = 10 C2 = 01 C3 =1100 => feedback: 10011100 (with probability 9%)• CBG3 and CBG1 are in error with soft feedback of 0011 and 1010 respectively=> Ci = 110 C2= 10 00 C3=0011 1010 => feedback: 110 1000 00111010 (with probability 0.4%)

[0098] The average feedback size for this compressed scheme is lower than the basic solution of no-compression. To give a numerical example, with the same parameters of N=3, M=4 and BLER target= 10% :• Feedback size without compression = M*N=12bits• Compressed feedback size - 1.68 bits < 2bits

[0099] The overhead reduction gain can be calculated as 12 / 1.68 - 700%

[0100] In one embodiment, the size of Cl part can be fixed to M to avoid confusion while decoding the feedback. Therefore, the aforementioned step to generate the Cl bit string will be modified to have a fixed size via zero-padding.

[0101] Figure 2 schematically illustrates an example of a signaling diagram for a CBG based HARQ feedback procedure according to an example embodiment of the present disclosure.

[0102] As illustrated in Figure 2, the network node (e.g., gNB) and the UE both support an HARQ process when communicating with each other. In particular, the gNB transmits to the UE one or more TB, each TB comprising a plurality of CBGs.

[0103] At step S20: the gNB configures the UE with a format for HARQ feedback. In particular, the gNB configures the UE with an HARQ feedback format as discussed above in accordance with the present disclosure.

[0104] In Figure 2, as an example, the configured HARQ format is for one or each TB transmitted by the gNB to the UE.

[0105] The configured HARQ feedback format for the one or each TB comprises a concatenation of a first bit string, a second bit string and a third bit string, wherein the first bit string corresponds to / indicates a number of one or more CBGs in one TB that are received at the UE in error; the second bit string indicates indices of the one or more CBGs received in error; and the third bit string indicates a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits.

[0106] In the present disclosure, soft HARQ feedback refers to that the feedback comprises more than one bit / multiple bits, e.g., in comparison to the 1 bit hard HARQ.

[0107] Optionally, still at step S20: the gNB signals to the UE a lookup table or a lookup table index for determining the first bit string. This step is optional at the gNB since the UE may be configured to generate a lookup table. The lookup table index corresponds to for instance a selected BLER in calculating the probabilities of having different numbers of CBGs in error. Generation of a lookup table is performed in accordance with the present disclosure as described above.

[0108] At step S21 : the gNB transmits to the UE a TB, wherein the TB comprises M CBGs, wherein M is an integer greater than or equal to 1.

[0109] At step S22: the UE receives the TB transmitted from the gNB. The UE preferably determines which CBG(s) in the one received TB are received in error, details of which are not described here since they belong to basic knowledge of the skilled person in e.g., the field of error detection.

[0110] At step S23 : the UE determines the first bit string, i.e., Ci, based on the lookup table. The lookup table may be generated at the UE or transmitted from the gNB or indicated by the gNB based on a lookup table index. In all cases, one lookup table may correspond to one selected BLER applied in calculating the probabilities of having different numbers of CBGs in error. In all cases, preferably, the design of the lookup table follows the principle that more erroneous CBGs in one received TB correspond to a longer codeword.

[0111] At step S24: the UE determines the second bit string, i.e., C2, and the third bit string, i.e., C3. Implementation details for the UE to determine which CBGs in the received TB are in error and to determine a corresponding soft / multibit HARQ feedback for those CBGs in error are not discussed here since they are part of the techniques known to the skilled person.

[0112] Still At step S24: the UE therefore obtains a bit string F that is a concatenation of Ci, C2 and C3. Of course the order of concatenation of the first to third bit strings is not limited to the order of Cl followed by C2 by C3, wherein they can be concatenated in any order as configured between the gNB and the UE.

[0113] At step S25: the UE transmits to the gNB the concatenated bit string F as the HARQ feedback for the one received TB.

[0114] At step S26: the gNB receives the concatenated bit string F, wherein based on the received concatenated HARQ feedback, the gNB obtains Ci, C2 and C3, and determines to retransmit the CBGs that are received at the UE in error in the previous transmission, based on the soft HARQ feedback for each CBG in error.

[0115] Based on the above exemplary embodiments, it is proposed in accordance with the present disclosure further exemplary embodiments / enhancements to overhead reduction.

[0116] One consideration is that with occurrence of very low probability events, e.g. all the CBGs failing, the size of the feedback can exceed the legacy feedback size. While it is true that these events are extremely rare, e.g. for a previous example the probability is 4e-7, there might still be cases where they can become more probable. One scenario is when the link adaptation mechanisms are not converged yet or a radio link failure happens and the transmission of CBGs may happen with a biased modulation and coding scheme (MCS) index that will lead to a lot of failed CBGs.

[0117] In order to keep the overhead of proposed feedback scheme still practical for these rare cases, one or more of the following options can be utilized in accordance with the present disclosure:1. Threshold-based fallback to uncompressed mode: a (first) threshold of Ti can be configured via gNB to make the UE use the non-compressed scheme feedback mode. This threshold can indicate the maximum number of failed CBG before the UE should choose not to compress the HARQ feedback. For the example above with CBGs 3 and 1 failing, if gNB configures Ti=l, then the UE will use 12 bits for feedback instead of the 15 bits generated via the proposed method.2. Threshold-based fallback to legacy CBG mode: a (second) threshold of T2 can be configured via gNB to make the UE use the legacy M bits CBG based feedback, where instead of soft feedback, the UE reports a single bit feedback per CBG indicating if the transmission was successful or not. This is useful when most of the CBGs are in error or soft feedback values are lower than another (third) threshold T3 where high resolution soft feedback does not provide sufficient information compared to the ACK / NACK feedback. For the same example, if T2=l, then the report will be only 3 bits = 010 (CBG1&3 failed, CBG2 passed). Similarly if T3 = 1100 (soft feedback threshold), since both soft feedbacks for CBG 1&3 are lower that T3, the same 3-bit feedback will be sent.3. Threshold-based fallback to legacy TB mode: a (fourth) threshold of T4 can be configured via gNB to make the UE use the legacy single bit TB based feedback, where instead of soft feedback, the UE reports a single bit feedback per TB indicating if the transmission was successful or not. This is useful when soft feedback values are lower than the threshold T4 where high resolution soft feedback and per CBG report does notprovide sufficient information compared to a single-bit ACK / NACK for the TB-based feedback.4. Differential soft feedback reporting: the gNB may configure the UE to use a differential coding scheme when generating C3, where a reference soft feedback is inserted first and the soft feedback of the rest of the CBGs will only reflect the difference compared to the reference feedback. For instance, when CBG3 and CBG1 are in error with soft feedback of 1010 and 1011 respectively: C3 = [reference term] [difference compared to the reference] = 1010 [reference] 1 [1011 -1010 = 1] = 10101. This method is useful when the soft feedbacks of the CBGs are very similar, i.e., due to correlation in their physical channels, and it is expected that the individual feedbacks are around a reference point.

[0118] The configuration of the threshold(s) preferably happens in the first step (S20) in Figure 2 where the gNB signals the configurations. The values for the thresholds are based on implementation and gNB’s decision. The gNB may decide to have fixed values for all the UEs or different values for each UE.Fixed size feedback

[0119] Another consideration could be that the variable size of the HARQ feedback may not be favorable for Physical Uplink Control Channel (PUCCH) resource allocation point of view. Therefore, it is further introduced in accordance with the present disclosure another alternative where a fixed size HARQ feedback is achieved for simpler signaling methods. Of course, a fixed size HARQ will have less overhead reduction gain due to same size feedback restriction. In the following, a method is described in an example algorithm:Extension to multi-PDSCH

[0120] Extension to multi-PDSCH HARQ feedback report: the same logic introduced to a single PDSCH transmission (as shown in Figure 2) can be expanded for the cases where the gNB schedules multiple PDSCH transmissions and configures the UE to send a collective / cumulative HARQ feedback for all of them. The gNB configures the UE for the collective / cumulative HARQ feedback for multiple TBs and after transmission of the bundle of TBs, the UE calculates a compressed feedback Fi for TBi and in the end concatenates them into a single bit string F and reports it back to the gNB. Depending on the feedback, the gNB may retransmit the failed CBGs (if any) for the erroneous TBs.

[0121] Figure 3 schematically illustrates an example of a signaling diagram for a CBG based HARQ feedback procedure according to an example embodiment of the present disclosure.

[0122] At step S30: the gNB configures the UE with a format for a collective / cumulative HARQ feedback. The configured format for a collective HARQ feedback comprises a plurality of single HARQ feedbacks respectively for a plurality of TBs. Each single HARQ feedback comprises the first to third bit strings, i.e., Ci to C3, as described above, for instance according to Figure 2.

[0123] In the present disclosure, for distinguishing between single-PDSCH and multi- PDSCH feedback, the HARQ feedback for one TB is referred to as “single HARQ feedback”, whereas the HARQ feedback for a plurality of TBs is referred to as “collective / cumulative HARQ feedback”.

[0124] At step S31 : the gNB transmits to the UE a plurality of TBs (assuming N TBs), preferably each TB comprising a plurality of CBGs. In other words, at step S311, the gNB transmits to the UE a TBi preferably comprising a plurality of CBGs; at step S312, the gNB transmits to the UE a TB2 preferably comprising a plurality of CBGs; this procedure continues until at step S3 IN, the gNB transmits to the UE the last of the plurality of TBs, namely TBN preferably comprising a plurality of CBGs. Each TB may comprise the same or different number of CBGs.

[0125] At step S32 to step S34, the UE determines for each received TBi in the plurality of TBs a corresponding single HARQ feedback, wherein i is an interger and 1 < i < N . Therefore, step S32 to step S34 are repeated for all received TBs.

[0126] At step S32: the UE receives the TBi and determines one or more CBGs included in the received TBi that are received in error. Therein, preferably the UE determines the number of CBGs that are received in error, the indices of the determined CBGs that are received in error, as well as the corresponding soft feedback for each determined CBG that is received in error. Implementation details for the UE to determine erroneous CBGs and soft feedbacks therefor are not discussed here since the skilled person shall apply techniques that they deem necessary for such error detection and determination.

[0127] At step S33 : the UE determines the first bit string, i.e., Ci, based on the lookup table. As described above, the UE may determine the lookup table, based on the design principle that longer bit strings / codewords correspond to lower probabilities of the number of CBGs in error. Alternatively or additionally, the gNB may generate the lookup table, for instance based on the same principle. Alternatively or additionally, the gNB may transmit the generated lookup tableto the UE, or transmit an index of the generated lookup table to the UE, wherein the index preferably corresponds to a selected BLER in calculating the probabilities of having different numbers of CBGs in error.

[0128] At step S34: the UE determines the second bit string C2 and the third bit string C3, based on the determined indices of the CBGs in error and the soft feedback determined therefor, respectively.

[0129] Consequently, after performing steps S32 to S34 repeatedly, the UE obtains for each TB, i.e., TBi, a corresponding concatenated HARQ feedback, Fi.

[0130] At step S35: the UE further concatenates the single HARQ feedbacks for all TBs, namely concatenates Fi, F2,.. . FN, SO as to obtain a cumulative HARQ feedback F.

[0131] At step S36: the UE transmits the cumulative HARQ feedback F to the gNB.

[0132] At step S37: the gNB receives the cumulative HARQ feedback F and determines to retransmit the CBGs that are previously received in error at the UE, based on the soft HARQ feedbacks (for indicated erroneous CBGs in all TBs) derived from the cumulative HARQ feedback.

[0133] At step S38: the gNB retransmits to the UE the CBGs that have been received in error at the UE, based on the received cumulative HARQ feedback. In other words, at step S381: the gNB initiates retransmission of the failed CBGs (i.e., the CBGs in error) in TBi. Similarly, at step S382: the gNB initiates retransmission of the failed CBGs in TB2. This step is repeated until at step S38N: the gNB initiates retransmission of the failed CBGs in TBN.Dynamic lookup table generation

[0134] Dynamic lookup table generation: One alternative to the fixed specified lookup tables is that the tables are generated on-fly and shared between the gNB and the UE. Therefore, the gNB operates based on the target BLER configured for the UE’s service and accordingly generates a static lookup table for specifying what each codeword represents in a HARQ feedback.

[0135] In summary, it is proposed in accordance with the present disclosure CBG based HARQ feedback with reduced overhead in providing the feedback.

[0136] The feedback in accordance with the present disclosure achieves efficient resource usage by being divided into three parts, indicating respectively the number of CBGs (in onereceived TB) in error, the indices of those erroneous CBGs and the HARQ feedback for those erroneous CBGs.

[0137] The feedback in accordance with the present disclosure further achieves reduced overhead in that the number of CBGs received in error is indicated with reduced / compressed bit string with reduced size / length of bits needed for the reporting. In particular, the bit string for reporting the number of CBGs received in error has a reduced / compressed size based on a lookup table / a coding scheme where a smaller number of CBGs in error (hence a more probable event) has a shorter codeword length. This leads to a reduced length / size of the reporting bit string in average.

[0138] The feedback in accordance with the present disclosure further ensures efficient resource scheduling at the network node for retransmissions for the erroneous CBGs in that the gNB is informed of the soft HARQ feedback for the erroneous CBGs with an appropriate / reduced / compressed reporting overhead of the HARQ feedback, which still ensures deriving of sufficient HARQ feedback information for the indicated erroneous CBGs.

[0139] The present disclosure further provides CBG based HARQ feedback methods that are more applicable to different error scenarios where excessive overheads in reporting the HARQ feedback for CBG(s) can be avoided.

[0140] It is noted that, although in the above-illustrated example embodiments (with reference to the figures), the messages communi cated / exchanged between the network components / elements may appear to have specific / explicit names, depending on various implementations (e.g., the underlining technologies), these messages may have different names and / or be communi cated / exchanged in different forms / formats, as can be understood and appreciated by the skilled person.

[0141] According to some example embodiments, there are also provided corresponding methods suitable to be carried out by the apparatuses (network elements / components) as described above, such as the UE, the CU, the DU, etc.

[0142] It should nevertheless be noted that the apparatus (device) features described above correspond to respective method features that may however not be explicitly described, for reasons of conciseness. The disclosure of the present document is considered to extend also to such method features. In particular, the present disclosure is understood to relate to methods of operating the devices described above, and / or to providing and / or arranging respective elements of these devices.

[0143] Further, according to some further example embodiments, there is also provided a respective apparatus (e.g., implementing the UE, the CU, the DU, etc., as described above) that comprises at least one processing circuitry, and at least one memory for storing instructions to be executed by the processing circuitry, wherein the at least one memory and the instructions are configured to, with the at least one processing circuitry, cause the respective apparatus to at least perform the respective steps as described above.

[0144] Yet in some other example embodiments, there is provided a respective apparatus (e.g., implementing the UE, the CU, the DU, etc., as described above) that comprises respective means configured to at least perform the respective steps as described above.

[0145] It is to be noted that examples of embodiments of the disclosure are applicable to various different network configurations. In other words, the examples shown in the above described figures, which are used as a basis for the above discussed examples, are only illustrative and do not limit the present disclosure in any way. That is, additional further existing and proposed new functionalities available in a corresponding operating environment may be used in connection with examples of embodiments of the disclosure based on the principles defined.

[0146] It should also to be noted that the disclosed example embodiments can be implemented in many ways using hardware and / or software configurations. For example, the disclosed embodiments may be implemented using dedicated hardware and / or hardware in association with software executable thereon. The components and / or elements in the figures are examples only and do not limit the scope of use or functionality of any hardware, software in combination with hardware, firmware, embedded logic component, or a combination of two or more such components implementing particular embodiments of the present disclosure.

[0147] It should further be noted that the description and drawings merely illustrate the principles of the present disclosure. Those skilled in the art will be able to implement various arrangements that, although not explicitly described or shown herein, embody the principles of the present disclosure and are included within its spirit and scope. Furthermore, all examples and embodiment outlined in the present disclosure are principally intended expressly to be only for explanatory purposes to help the reader in understanding the principles of the proposed method. Furthermore, all statements herein providing principles, aspects, and embodiments of the present disclosure, as well as specific examples thereof, are intended to encompass equivalents thereof.List of abbreviations:BLER Block error rateCQI Channel quality indicatorMCS Modulation and coding scheme HARQ Hybrid automatic repeat requestACK AcknowledgementLDPC low density parity checkTB Transport blockCBG Code block group PDSCH Physical downlink shared channelPUCCH Physical uplink control channelUE User equipmentRRC Radio Resource Control

Claims

CLAIMS:

1. A User Equipment, UE, configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with a network node of a radio access network, comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the UE at least to: receive, from the network node, a Transport Block, TB, comprising a plurality of Code Block Groups, CBGs; and for the received TB: determine, among the plurality of received CBGs, one or more CBGs that are received in error; determine a first bit string corresponding to a number of the one or more CBGs received in error; determine a second bit string indicating indices of the one or more CBGs received in error; determine a third bit string relating to a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits; concatenate the first bit string, the second bit string and the third bit string; and transmit the concatenated bit string to the network node as HARQ feedback for the received TB, wherein the UE is further caused to: determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the received TB, the lookup table comprises a corresponding codeword in the form of a bit string.

2. The UE according to claim 1, wherein the UE is further caused to: calculate, for each possible number of CBGs in error in one TB, a corresponding error probability of having the each possible number of CBGs in error, based on following parameters: a selected target Block Error Rate, BLER, the number of CBGs in error and the total number of CBGs in the one TB; and determine for each calculated error probability, a corresponding codeword,wherein as the number of possible CBGs in error in the one TB increases, the corresponding error probability decreases and length of the corresponding codeword increases.

3. The UE according to claim 1 or 2, wherein: if the number of the one or more CBGs received in error is greater than a first threshold, the UE is caused to determine a soft HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, soft HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

4. The UE according to any one of claims 1 to 3, wherein: if the number of the one or more CBGs received in error is greater than a second threshold and / or if at least one CBG received in error has a soft HARQ feedback value lower than a third threshold, the UE is caused to determine a single bit HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, single bit HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

5. The UE according to any one of claims 1 to 4, wherein if at least one CBG received in error has a soft HARQ feedback value lower than a fourth threshold, the UE is caused to determine a single bit HARQ feedback for the received TB and transmit, to the network node, the single bit feedback as HARQ feedback for the received TB.

6. The UE according to any one of claims 1 to 5, wherein the third bit string comprises a soft HARQ feedback for one CBG received in error as a reference soft HARQ feedback, wherein the third bit string further comprises, for each of the remaining CBGs received in error, a difference between a soft HARQ feedback for the each remaining CBG received in error and the reference soft HARQ feedback.

7. The UE according to any one of claims 1 to 6, wherein the UE is further caused to: receive, from the network node, a plurality of TBs, each TB comprising a plurality of CBGs; for each received TB, determine a corresponding HARQ feedback comprising a concatenated bit string; concatenate all HARQ feedbacks of the plurality of received TBs; andtransmit the concatenated HARQ feedbacks to the network node as cumulative HARQ feedback for the plurality of received TBs.

8. The UE according to any one of claims 1 to 7, wherein the UE is further caused to: generate the lookup table based on Hoffman coding.

9. The UE according to any one of claims 1 to 8, wherein the UE is further caused to: receive the lookup table or an index of the lookup table from the network node, wherein the index of the lookup table corresponds to a BLER selected for the UE.

10. The UE according to any one of claims 1 to 9, wherein the UE is further caused to: determine a fixed total size of the concatenated bit string; determine a first fixed size of the first bit string; determine a second size of the second bit string based on the first fixed size and the number of CBGs in error; and determine a third size of the third bit string based on the fixed total size, the first fixed size, the determined second size and the number of CBGs in error.

11. The UE according to claim 10, wherein the UE is further caused to downsample the soft HARQ feedbacks for all CBG received in error, to obtain the third bit string that has the determined third size.

12. The UE according to claim 10 or 11, wherein if the fixed total size is less than sum of the determined first fixed size and the determined second size, the UE is further caused to determine a single bit HARQ feedback for the received TB or for each received CBG as HARQ feedback for the received TB.

13. A network node of a radio access network, configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with a User Equipment, UE, the network node comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the network node least to:configure the UE with an HARQ feedback format for a Tansport Block, TB, comprising a plurality of Code Block Groups, CBGs, wherein the format comprises a concatenation of a first bit string, a second bit string and a third bit string, wherein: the first bit string corresponds to a number of one or more CBGs in one TB that are received at the UE in error, the second bit string indicates indices of the one or more CBGs received in error; and the third bit string indicates a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits, wherein the network node is further caused to configure the UE to determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the one TB, the lookup table comprises a corresponding codeword in the form of a bit string.

14. The network node according to claim 13, wherein the network node is further caused to: calculate, for each possible number of CBGs in error in one TB, a corresponding error probability of having the each possible number of CBGs in error, based on following parameters: a selected target Block Error Rate, BLER, the number of CBGs in error and the total number of CBGs in the one TB; and determine for each calculated error probability, a corresponding codeword, wherein as the number of possible CBGs in error in the one TB increases, the corresponding error probability decreases and length of the corresponding codeword increases.

15. The network node according to claim 13 or 14, wherein the network node is further caused to configure with UE with a first threshold, and configure the UE to: after receiving a TB, if the number of the one or more CBGs received in error is greater than the first threshold, determine a soft HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, soft HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

16. The network node according to any one of claims 13 to 15, wherein the network node is further caused to configure with UE with a second threshold and / or a third threshold, and configure the UE to: after receiving a TB, if the number of the one or more CBGs received in error is greater than the second threshold and / or if at least one received CBG in error has a soft HARQ feedback value lower than the third threshold, determine a single bit HARQ feedback for each of the plurality of CBGs in the received TB and transmit, to the network node, single bit HARQ feedbacks of all received CBGs as HARQ feedback for the received TB.

17. The network node according to any one of claims 13 to 16, wherein the network node is further caused to configure with UE with a fourth threshold, and configure the UE to: after receiving a TB, if at least one received CBG in error has a soft HARQ feedback value lower than a fourth threshold, determine a single bit HARQ feedback for the received TB and transmit, to the network node, the single bit feedback as HARQ feedback for the received TB.

18. The network node according to any one of claims 13 to 17, wherein the third bit string comprises a soft HARQ feedback for one CBG received in error as a reference soft HARQ feedback, wherein the third bit string further comprises, for each of the remaining CBGs received in error, a difference between a soft HARQ feedback for the each remaining CBG received in error and the reference soft HARQ feedback.

19. The network node according to any one of claims 13 to 18, wherein the network node is further caused to: transmit, to the UE, a plurality of TBs, each TB comprising a plurality of CBGs; for each transmitted TB, configure the UE with said HARQ feedback format comprising a concatenated bit string; and for said plurality of TBs, configure the UE with a cumulative HARQ feedback format comprising a concatenation of all HARQ feedbacks of the plurality of received TBs.

20. The network node according to any one of claims 13 to 19, wherein the network node is further caused to:generate the lookup table based on Hoffman coding.

21. The network node according to any one of claims 13 to 20, wherein the network node is further caused to: transmit to the UE the lookup table or an index of the lookup table, wherein the index of the lookup table corresponds to a BLER selected for the UE.

22. The network node according to any one of claims 13 to 21, wherein the network node is further caused to: configure the UE to generate the lookup table.

23. The network node according to any one of claims 13 to 22, wherein the network node is further caused to receive from the UE an HARQ feedback for one or more transmitted TBs, and determine the CBGs that are received at the UE in error and retransmit the determined CBGs in error.

24. The network node according to any one of claims 13 to 23, wherein the network node is further caused to: configure the UE with a fixed total size of the concatenated bit string and a first fixed size of the first bit string; configure the UE to determine a second size of the second bit string based on the first fixed size and the number of CBGs in error; and configure the UE to determine a third size of the third bit string based on the fixed total size, the first fixed size, the determined second size and the number of CBGs in error, wherein the network node is further caused to configure the UE to downsample the soft HARQ feedbacks for all CBG received in error, to obtain the third bit string that has the determined third size.

25. The network node according to claim 24, wherein, after receiving from the UE an HARQ feedback for one TB, the network node is further caused to: determine the number of CBGs received at the UE in error based on the first bit string included in the HARQ feedback;determine the second bit string based on the determined number of CBGs in error and the number of CBGs in the one TB; and determine the third bit string based on the first bit string, the second bit string and the fixed total size of the HARQ feedback of the one TB.

26. A system, comprising: a user equipment, UE, according to any one of claims 1 to 12, and a network node according to any one of claims 13 to 25, wherein the UE and the network node are configured to support a Hybrid Automatic Repeat Request, HARQ, process when communicating with each other.

27. A method of a User Equipment, UE, that supports a Hybrid Automatic Repeat Request, HARQ, process when communicating with a network node of a radio access network, the method comprising: receiving, from the network node, a Transport Block, TB, comprising a plurality of Code Block Groups, CBGs; and for the received TB: determining, among the plurality of received CBGs, one or more CBGs that are received in error; determining a first bit string corresponding to a number of the one or more CBGs received in error; determining a second bit string indicating indices of the one or more CBGs received in error; determining a third bit string relating to a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits; concatenating the first bit string, the second bit string and the third bit string; and transmitting the concatenated bit string to the network node as HARQ feedback for the received TB, wherein the method further comprises: determining the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the received TB, the lookup table comprises a corresponding codeword in the form of a bit string.

28. A method of a network node that supports a Hybrid Automatic Repeat Request, HARQ, process when communicating with a User Equipment, UE, the method comprising: configuring the UE with an HARQ feedback format for a Tansport Block, TB, comprising a plurality of Code Block Groups, CBGs, wherein the format comprises a concatenation of a first bit string, a second bit string and a third bit string, wherein: the first bit string corresponds to a number of one or more CBGs in one TB that are received at the UE in error, the second bit string indicates indices of the one or more CBGs received in error; and the third bit string indicates a soft HARQ feedback for each CBG received in error, wherein the soft HARQ feedback for each CBG received in error comprises multiple bits, wherein the method further comprises configuring the UE to determine the first bit string based on a lookup table, wherein for each possible number of CBGs in error in the one TB, the lookup table comprises a corresponding codeword in the form of a bit string.

29. A computer program comprising instructions for causing an apparatus to perform the method according to claim 27 or claim 28.

30. A memory storing computer readable instructions for causing an apparatus to perform the method according to claim 27 or claim 28.

Images