WO2022086398A1

WO2022086398A1 - User equipment, radio network node and methods performed in a wireless communication network

Info

Publication number: WO2022086398A1
Application number: PCT/SE2021/051021
Authority: WO
Inventors: Min Wang
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2020-10-22
Filing date: 2021-10-18
Publication date: 2022-04-28

Abstract

Embodiments herein relate to, for example, a method performed by a UE (10) for handling communication over a sidelink in a wireless communication network. The UE (10), upon receiving an indication to reactivate or activate a sidelink configuration, performs one of the following: -flushing transmitted data, that are not confirmed received at another UE, ina HARQ buffer of a non-idle HARQ process; - sending a HARQ indication to a radio network node (12), wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or -sending the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration.

Description

USER EQUIPMENT, RADIO NETWORK NODE AND METHODS PERFORMED IN A WIRELESS COMMUNICATION NETWORK

TECHNICAL FIELD

Embodiments herein relate to a user equipment (UE), a radio network node and methods performed therein regarding wireless communication. Furthermore, a computer program product and a computer-readable storage medium are also provided herein. Especially, embodiments herein relate to handling or enabling communication, e.g. handling sidelink (SL) communication between UEs, in a wireless communication network.

BACKGROUND

In a typical wireless communication network, UEs, also known as wireless communication devices, mobile stations, stations (STA) and/or wireless devices, communicate via a Radio access Network (RAN) to one or more core networks (CN). The RAN covers a geographical area which is divided into service areas or cell areas, with each service area or cell area being served by network node such as an access node e.g. a Wi-Fi access point or a radio base station (RBS), which in some radio access technologies (RAT) may also be called, for example, a NodeB, an evolved NodeB (eNodeB) and a gNodeB (gNB). The service area or cell area is a geographical area where radio coverage is provided by the radio network node. The radio network node operates on radio frequencies to communicate over an air interface with the wireless devices within range of the access node. The radio network node communicates over a downlink (DL) to the wireless device and the wireless device communicates over an uplink (UL) to the access node.

A Universal Mobile Telecommunications System (UMTS) is a third generation telecommunication network, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High-Speed Packet Access (HSPA) for communication with user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for present and future generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some RANs, e.g. as in UMTS, several radio network nodes may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural radio network nodes connected thereto. The RNCs are typically connected to one or more core networks.

Specifications for the Evolved Packet System (EPS) have been completed within the 3^rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases, such as 5G and 6G networks. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long-Term Evolution (LTE) radio access network, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a 3GPP radio access technology wherein the radio network nodes are directly connected to the EPC core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio network nodes connected directly to one or more core networks.

With the emerging 5G technologies also known as new radio (NR), the use of very many transmit- and receive-antenna elements may utilize beamforming, such as transmitside and receive-side beamforming. Transmit-side beamforming means that the transmitter can amplify the transmitted signals in a selected direction or directions, while suppressing the transmitted signals in other directions. Similarly, on the receive-side, a receiver can amplify signals from a selected direction or directions, while suppressing unwanted signals from other directions.

Similar to LTE, NR uses Orthogonal Frequency Division Multiplexing (OFDM) in the downlink, i.e. from a network node, gNB, eNB, or base station, to a UE. The basic NR physical resource over an antenna port can thus be seen as a time-frequency grid as illustrated in Fig. 1 , where a resource block (RB) in a 14-symbol slot is shown. A resource block corresponds to 12 contiguous subcarriers in the frequency domain. Resource blocks are numbered in the frequency domain, starting with 0 from one end of the system bandwidth. Each resource element corresponds to one OFDM subcarrier during one OFDM symbol interval.

Different subcarrier spacing values are supported in NR. The supported subcarrier spacing values (also referred to as different numerologies) are given by Af=(15x2^Ap) kHz where p e (0,1 , 2, 3, 4). Af=15 kHz is the basic (or reference) subcarrier spacing that is also used in LTE. In the time domain, downlink and uplink transmissions in NR will be organized into equally-sized subframes of 1ms each similar to LTE. A subframe is further divided into multiple slots of equal duration. The slot length for subcarrier spacing Af=(15*2^A p) kHz is 1/2^A p ms. There is only one slot per subframe for Af= 15kHz and a slot consists of 14 OFDM symbols.

Downlink transmissions are dynamically scheduled, i.e., in each slot the gNB transmits downlink control information (DCI) about which UE data is to be transmitted to and which resource blocks in the current downlink slot the data is transmitted on. This control information is typically transmitted in the first one or two OFDM symbols in each slot in NR. The control information is carried on the Physical Downlink Control Channel (PDCCH) and data is carried on the Physical Downlink Shared Channel (PDSCH). A UE first detects and decodes PDCCH, and, if a PDCCH is decoded successfully, it then decodes the corresponding PDSCH based on the downlink assignment provided by decoded control information in the PDCCH.

In addition to PDCCH and PDSCH, there are also other channels and reference signals transmitted in the downlink, including synchronization signal block (SSB), channel state information reference signal (CSI-RS), etc.

Uplink data transmissions, carried on Physical Uplink Shared Channel (PUSCH), can also be dynamically scheduled by the gNB by transmitting a DCI. The DCI, which is transmitted in the DL region, always indicates a scheduling time offset so that the PUSCH is transmitted in a slot in the UL region.

Sidelink transmissions are direct communications between two UEs without signal relay through a base station. Sidelink transmissions over NR are specified for release (Rel.)-16 allowing direct communication between two UEs without going through a base station. These are enhancements of the PROximity-based SErvices (ProSe) specified for LTE. Four new enhancements are particularly introduced to NR sidelink transmissions as follows:

• Support for unicast and groupcast transmissions are added in NR sidelink. For unicast and groupcast, a physical sidelink feedback channel (PSFCH) is introduced for a receiver UE to reply the decoding status to a transmitter UE.

• Grant-free transmissions, which are adopted in NR uplink transmissions, are also provided in NR sidelink transmissions, to improve the latency performance.

• To alleviate resource collisions among different sidelink (SL) transmissions launched by different UEs, it enhances channel sensing and resource selection procedures, which also lead to a new design of a physical sidelink control channel (PSCCH).

• To achieve a high connection density, congestion control and thus the quality of service (QoS) management is supported in NR sidelink transmissions.

To enable the above enhancements, new physical channels and reference signals are introduced in NR, available in LTE before:

• Physical Sidelink Shared Channel (PSSCH), which is an SL version of PDSCH: The PSSCH is transmitted by a sidelink transmitter UE, which conveys sidelink transmission data, system information blocks (SIB) for radio resource control (RRC) configuration, and a part of the sidelink control information (SCI).

• PSFCH, which is an SL version of PLICCH: The PSFCH is transmitted by a sidelink receiver UE for unicast and groupcast, which conveys 1 bit information over 1 resource block (RB) for the hybrid automatic repeat request (HARQ) acknowledgement (ACK) and the negative ACK (NACK). In addition, channel state information (CSI) is carried in the medium access control (MAC) control element (CE) over the PSSCH instead of the PSFCH.

• PSCCH, which is an SL version of PDCCH: When the traffic to be sent to a receiver UE arrives at a transmitter UE, the transmitter UE should first send the PSCCH, which conveys a part of SCI, which is an SL version of DCI, to be decoded by any UE for the channel sensing purpose, including the reserved timefrequency resources for transmissions, demodulation reference signal (DMRS) pattern and antenna port, etc.

• Sidelink Primary/Secondary Synchronization Signal (S-PSS/S-SSS): Similar to downlink transmissions in NR, in sidelink transmissions, primary and secondary synchronization signals, called S-PSS and S-SSS, respectively, are supported. Through detecting the S-PSS and S-SSS, a UE is able to identify the sidelink synchronization identity (SSID) from the UE sending the S-PSS/S-SSS. Through detecting the S-PSS/S-SSS, the UE is therefore able to know the characteristics of the UE transmitting the S-PSS/S-SSS. A series of processes of acquiring timing and frequency synchronization together with SSIDs of UEs are called initial cell search. Note that the UE sending the S-PSS/S-SSS may not be necessarily involved in sidelink transmissions, and a node, e.g. UE/eNB/gNB, sending the S- PSS/S-SSS is called a synchronization source. There are 2 S-PSS sequences and 336 S-SSS sequences forming a total of 672 SSIDs in a cell. • Physical Sidelink Broadcast Channel (PSBCH): The PSBCH is transmitted along with the S-PSS/S-SSS as a synchronization signal/PSBCH block (SSB). The SSB has the same numerology as PSCCH/PSSCH on that carrier, and an SSB should be transmitted within the bandwidth of the configured bandwidth part (BWP). The PSBCH conveys information related to synchronization, such as the direct frame number (DFN), indication of the slot and symbol level time resources for sidelink transmissions, in-coverage indicator, etc. The SSB is transmitted periodically at every 160 ms.

• DMRS, phase tracking reference signal (PT-RS), channel state information reference signal (CSI-RS): These physical reference signals supported by NR downlink/uplink transmissions are also adopted by sidelink transmissions. Similarly, the PT-RS is only applicable for frequency range 2 (FR2) transmission.

Another new feature is the two-stage sidelink control information (SCI). This a version of the DCI for SL. Unlike the DCI, only part, such as a first stage, of the SCI is sent on the PSCCH. This part is used for channel sensing purposes, including the reserved time-frequency resources for transmissions, demodulation reference signal (DMRS) pattern and antenna port, etc., and can be read by all UEs while the remaining, such as a second stage, scheduling and control information, such as a 8-bits source identity (ID) and a 16-bits destination ID, New Data Indicator (NDI), redundancy version (RV) and HARQ process ID, is sent on the PSSCH to be decoded by the receiver UE.

Similar as for PRoSE in LTE, NR sidelink transmissions have the following two modes of resource allocations:

• Mode 1: Sidelink resources are scheduled by a gNB.

• Mode 2: The UE autonomously selects sidelink resources from a (pre-)configured sidelink resource pool(s) based on the channel sensing mechanism.

For the in-coverage UE, a gNB can be configured to adopt Mode 1 or Mode 2. For the out-of-coverage UE, only Mode 2 can be adopted.

As in LTE, scheduling over the sidelink in NR is done in different ways for Mode 1 and Mode 2.

Mode 1 supports the following two kinds of grants:

Dynamic grant: When the traffic to be sent over sidelink arrives at a transmitter UE, this UE should launch the four-message exchange procedure to request sidelink resources from a gNB, scheduling request (SR) on UL, grant, buffer status report (BSR) on UL, grant for data on SL sent to UE. During the resource request procedure, a gNB may allocate a sidelink radio network temporary identifier (SL-RNTI) to the transmitter UE. If this sidelink resource request is granted by a gNB, then the gNB indicates the resource allocation for the PSCCH and the PSSCH in the downlink control information (DCI) conveyed by PDCCH with cyclic redundancy check (CRC) scrambled with the SL-RNTI. When the transmitter UE receives the DCI, the transmitter UE can obtain the grant only if the scrambled CRC of DCI can be successfully solved by the assigned SL-RNTI. The transmitter UE then indicates the time-frequency resources and the transmission scheme of the allocated PSSCH in the PSCCH, and launches the PSCCH and the PSSCH on the allocated resources for sidelink transmissions. When a grant is obtained from the gNB, the transmitter UE can only transmit a single transport block (TB). As a result, this kind of grant is suitable for traffic with a loose latency requirement.

Configured grant: For the traffic with a strict latency requirement, performing the four-message exchange procedure to request sidelink resources may induce unacceptable latency. In this case, prior to the traffic arrival, the transmitter UE may perform the four-message exchange procedure and request a set of resources. If a grant can be obtained from the gNB, then the requested resources are reserved in a periodic manner. Upon traffic arriving at the transmitter UE, this UE can launch the PSCCH and the PSSCH on the upcoming resource occasion. In fact, this kind of grant is also known as grant-free transmissions.

In both dynamic grant and configured grant, a sidelink receiver UE cannot receive the DCI, since it is addressed to the transmitter UE, and therefore a receiver UE should perform blind decoding to identify the presence of PSCCH and find the resources for the PSSCH through the SCI.

When the transmitter UE launches the PSCCH, CRC is also inserted in the SCI without any scrambling.

In the Mode 2 resource allocation, when traffic arrives at the transmitter UE, this transmitter UE should autonomously select resources for the PSCCH and the PSSCH. To further minimize the latency of the feedback HARQ ACK/NACK transmissions and subsequently retransmissions, the transmitter UE may also reserve resources for PSCCH/PSSCH for retransmissions. To further enhance the probability of successful TB decoding at one shot and thus suppress the probability to perform retransmissions, the transmitter UE may repeat the TB transmission along with the initial TB transmission. This mechanism is also known as blind retransmission. As a result, when traffic arrives at the transmitter UE, then this transmitter UE should select resources for the following transmissions: 1) The PSSCH associated with the PSCCH for initial transmission and blind retransmissions.

2) The PSSCH associated with the PSCCH for retransmissions.

Since each transmitter UE in sidelink transmissions should autonomously select resources for above transmissions, how to prevent different transmitter UEs from selecting the same resources turns out to be a critical issue in Mode 2. A particular resource selection procedure is therefore imposed to Mode 2 based on channel sensing. The channel sensing algorithm involves measuring reference signal received power (RSRP) on different subchannels and requires knowledge of the different UEs power levels of DMRS on the PSSCH or the DMRS on the PSCCH depending on the configuration. This information is known only after receiver SCI launched by (all) other UEs. The sensing and selection algorithm is rather complex.

There are device to device (D2D) discovery procedures for detection of services and applications offered by other UEs in close proximity. This is part of LTE Rel 12 and Rel 13. The discovery procedure has two modes, mode A based on open announcements (broadcasts) and mode B, which is request/response. The discovery mechanism is controlled by the application layer, such as ProSe. The discovery message is sent on the Physical Sidelink Discovery Channel (PSDCH) which is not available in NR. Also, there is a specific resource pool for announcement and monitoring of discovery messages. The discovery procedure can be used to detect UEs supporting certain services or applications before initiating direct communication.

Sidelink configured grant (CG).

As described in clause 5.8.3 in TS 38.321 v 16.2.1 , there are two types of transmission without dynamic grant:

- configured grant Type 1 where a sidelink grant is provided by RRC, and stored as configured sidelink grant;

- configured grant Type 2 where a sidelink grant is provided by PDCCH, and stored or cleared as configured sidelink grant based on L1 signalling indicating configured sidelink grant activation or deactivation.

CG Type 1 and/or Type 2 are configured with a single BWP. Multiple configurations of up to 8 configured grants (including both Type 1 and Type 2, if configured) can be active simultaneously on the BWP.

RRC configures the following parameters when the configured grant Type 1 is configured, as specified in TS 38.331 [5] or TS 36.331 [21]:

- sl-ConfiglndexCG: the identifier of a configured grant for sidelink; - sl-CS-RNTI: Sidelink Configured Scheduling (SLCS)-RNTI for retransmission;

- sl-NrOfHARQ-Processes'. the number of HARQ processes for configured grant;

- sl-PeriodCG periodicity of the configured grant Type 1 ;

- sl-TimeOffsetCG-Typel’. Offset of a resource with respect to system frame number (SFN) = sl-TimeReferenceSFN-Type1 in time domain, referring to the number of logical slots that can be used for SL transmission;

- sl-TimeResourceCG-Type1'. time resource location of the configured grant Type 1 ;

- sl-CG-MaxTransNumList. the maximum number of times that a TB can be transmitted using the configured grant;

- sl-HARQ-ProclD-offset. offset of HARQ process for configured grant Type 1 ;

- sl-TimeReferenceSFN-Type1'. SFN used for determination of the offset of a resource in time domain. The UE uses the closest SFN with the indicated number preceding the reception of the sidelink configured grant configuration Type 1.

RRC configures the following parameters when the configured grant Type 2 is configured, as specified in TS 38.331 [5]:

- sl-ConfiglndexCG the identifier of a configured grant for sidelink;

- sl-CS-RNTI’. SLCS-RNTI for activation, deactivation, and retransmission;

- sl-NrOfHARQ-Processes'. the number of HARQ processes for configured grant;

- sl-PeriodCG periodicity of the configured grant Type 2;

- sl-HARQ-ProclD-offset. offset of HARQ process for configured grant Type 2.

Upon configuration of a configured grant Type 1 , the MAC entity shall for each configured sidelink grant:

1 > store the sidelink grant provided by RRC as a configured sidelink grant;

1 > initialise or re-initialise the configured sidelink grant to determine PSCCH duration(s) and PSSCH duration(s) according to sl-TimeOffsetCG-Type1 and sl- TimeResourceCG-Typel , and to reoccur with sl-periodCG for transmissions of multiple MAC protocol data units (PDU) according to clause 8.1.2 of TS 38.214 [7],

NOTE 1 : If the MAC entity is configured with multiple configured sidelink grants, collision among the configured sidelink grants may occur. How to handle the collision is left to UE implementation.

After a sidelink grant is configured for a configured grant Type 1 , the MAC entity shall consider sequentially that the first slot of the S^th sidelink grant occurs in the logical slot for which: [(SFN x numberOfSLSIotsPerFrame) + logical slot number in the frame] = (sl-TimeReferenceSFN-Type1 x numberOfSLSIotsPerFrame + sl-TimeOffsetCGType1+ S x PeriodicitySL) modulo (1024 x numberOfSLSIotsPerFrame). refers to the

number of logical slots that can be used for SL transmsission in the frame and N refer to the number of slots that can be used for SL transmsission within 20ms, if configured, of TDD-UL-DL-ConfigCommon, as specified in TS 38.331 [5] and clause 8.1.7 of TS 38.214 [7].

After a sidelink grant is configured for a configured grant Type 2, the MAC entity shall consider sequentially that the first slot of S^th sidelink grant occurs in the logical slot for which:

[(SFN x numberOfSLSIotsPerFrame + logical slot number in the frame] = [(SFNstart time ^x numberOfSLSIotsPerFrame + slotstart time) + S x PeriodicitySL] modulo (1024 x numberOfSLSIotsPerFrame). where SFNstart time and slotstart time are the SFN and logical slot, respectively, of the first transmission opportunity of PSSCH where the configured sidelink grant was (re-)initialised.

When a configured sidelink grant is released by RRC, all the corresponding configurations shall be released and all corresponding sidelink grants shall be cleared. The MAC entity shall:

1 > if the configured sidelink grant confirmation has been triggered and not cancelled; and

1 > if the MAC entity has UL resources allocated for new transmission:

2> instruct the Multiplexing and Assembly procedure to generate a Sidelink Configured Grant Confirmation MAC CE as defined in clause 6.1.3.34;

2> cancel the triggered configured sidelink grant confirmation.

For a configured grant Type 2, the MAC entity shall clear the corresponding configured sidelink grant immediately after first transmission of Sidelink Configured Grant Confirmation MAC CE triggered by the configured sidelink grant deactivation.

SUMMARY

As highlighted and underlined below, in clause 5.22.1.1 in the TS 38.321 v 16.2.1, 1>else if a sidelink grant has been received on the PDCCH for the MAC entity's SLCS- RNTI:

2> if PDCCH contents indicate retransmission(s) for the identifed HARQ process ID that has been set for an activated configured sidelink grant identified by sl- ConfiglndexCG: 3> use the received sidelink grant to determine PSCCH duration(s) and PSSCH duration(s) for one or more retransmissions of a single MAC PDU according to clause 8.1.2 of TS 38.214 [7],

2>else if PDCCH contents indicate configured grant Type 2 deactivation for a configured sidelink grant:

3> clear the configured sidelink grant, if available;

3> trigger configured sidelink grant confirmation for the configured sidelink grant.

2>else if PDCCH contents indicate configured grant Type 2 activation for a configured sidelink grant:

3> trigger configured sidelink grant confirmation for the configured sidelink grant;

3> store the configured sidelink grant;

3> initialise or re-initialise the configured sidelink grant to determine the set of PSCCH durations and the set of PSSCH durations for transmissions of multiple MAC PDUs according to clause 8.1.2 of TS 38.214 |7],

Thus, upon reception of a DCI activation and reactivation command, the UE performs the below actions

1) trigger CG confirmation,

2) store the new CG grant,

3) initialize and re-initialize the resources for transmissions of a new TB (including the initial transmission and retransmissions) according to the new CG grant.

As part of developing embodiments herein, one or more problems were first identified for the above actions:

Issue 1 : the UE may have pending TBs in the HARQ processes containing TBs which are being transmitted and retransmitted using the old configured SL grant.

There may be one or multiple HARQ processes containing the TBs using the configured SL grant which needs to be reactivated. Those TBs are referred to as pending TBs. Those TBs may have same or different transport block size (TBS) as the new SL configured grant (CG) grant. In this case, it may be considered how shall the UE handle these pending TBs.

The similar issue is also observed in case the UE receives a Type 1 configured grant reconfiguration message. As shown in clause 5.8.3 in TS 38.321 v 16.2.1 ,

Upon configuration of a configured grant Type 1, the MAC entity shall for each configured sidelink grant:

1> store the sidelink grant provided by RRC as a configured sidelink grant;

1> initialise or re-initialise the configured sidelink grant to determine PSCCH duration(s) and PSSCH duration(s) according to sl-TimeOffsetCG-Type1 and sl-TimeResourceCG-Type1 , and to reoccur with sf-per/odCG for transmissions of multiple MAC PDUs according to clause 8.1.2 of TS 38.214.

As a summary, the above issue(s) may be addressed, i.e. , how to handle TBs, or actually transmitted data, in an efficient manner to improve performance in the wireless communication network.

An object of embodiments herein is, thus, to provide a mechanism that improves the performance in the wireless communication network.

According to an aspect, the object is achieved by providing a method performed by UE, such as a remote UE, or a device to device UE, for handling communication over a sidelink in a wireless communication network. The UE, upon receiving an indication to reactivate or activate a sidelink configuration, such as a sidelink configured grant (SLCG) configuration, performs one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send a HARQ indication to a radio network node, wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration. For example, the UE may decide to handle transmitted data, such as transport blocks, that are not confirmed received at another UE: by flushing the transmitted data in a HARQ buffer of a non-idle HARQ process; and/or by sending an indication to a radio network node, wherein the indication relates to the HARQ buffer or the non-idle HARQ process, for example, informing that there are pending transmitted data for further retransmissions at the UE, sending NACK; or by sending the data of the HARQs to a UE based on matching TBS of sidelink configuration compared with TBS of previous sidelink configuration.

According to another aspect, the object is achieved by providing a method performed by a radio network node, such as a radio base station, for handling communication over a sidelink between UEs in a wireless communication network. The radio network node transmits a configuration to a UE configuring the UE to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send an HARQ indication to the radio network node, wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration. The radio network node may thus transmit a configuration to the UE configuring the UE to, upon receiving an indication to reactivate or activate a sidelink configuration, such as a SLCG configuration, to handle transmitted data, such as transport blocks that are not confirmed received at another UE: by flushing the transmitted data in a HARQ buffer of a non-idle HARQ process; and/or by sending an indication to the radio network node, wherein the indication relates to the HARQ buffer or the non-idle HARQ process, for example, informing that there are pending transmitted data for further retransmissions at the UE, sending NACK; or by sending the data of the HARQs to a UE based on matching TBS of sidelink configuration compared with TBS of previous sidelink configuration.

According to still another aspect, the object is achieved by providing a UE, and a radio network node configured to perform the methods herein, respectively.

Thus, it is herein provided a UE for handling communication over a sidelink in a wireless communication network. The user equipment is configured to perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send a HARQ indication to a radio network node, wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration.

Furthermore, it is herein provided a radio network node for handling communication over a sidelink between UEs in a wireless communication network. The radio network node is configured to transmit a configuration to a UE configuring the UE to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send an HARQ indication to the radio network node, wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration.

It is furthermore provided herein a computer program product comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry out any of the methods above, as performed by the radio network node or the user equipment, respectively. It is additionally provided herein a computer- readable storage medium, having stored thereon a computer program product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the methods above, as performed by the radio network node or the user equipment, respectively.

Embodiments herein allow a reactivation or activation of a SL configuration in a resource efficient manner allowing the UE to handle transmitted data such as TBs in an efficient manner resulting in an improved performance of the wireless communication network.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments will now be described in more detail in relation to the enclosed drawings, in which:

Fig. 1 shows NR physical resource grid according to prior art;

Fig. 2 is a schematic overview depicting a wireless communication network according to embodiments herein;

Fig. 3 is a combined signalling scheme and flowchart according to embodiments herein;

Fig. 4 is a block diagram depicting a method in a UE according to embodiments herein;

Fig. 5 is a block diagram depicting a method in a radio network node according to embodiments herein;

Fig. 6 is a block diagram depicting a UE according to embodiments herein;

Fig. 7 is a block diagram depicting a radio network node according to embodiments herein;

Fig. 8 schematically illustrates a telecommunication network connected via an intermediate network to a host computer;

Fig. 9 is a generalized block diagram of a host computer communicating via a base station with a user equipment over a partially wireless connection; and

Figs. 10, 11 , 12, and 13 are flowcharts illustrating methods implemented in a communication system including a host computer, a base station and a user equipment.

DETAILED DESCRIPTION

Embodiments herein are described within the context of 3GPP NR radio technology (3GPP TS 38.300 V15.2.0 (2018-06)). It is understood that the problems and solutions described herein are equally applicable to wireless access networks and user- equipments (UEs) implementing other access technologies and standards. NR is used as an example technology where embodiments are suitable, and using NR in the description therefore is particularly useful for understanding the problem and solutions solving the problem. In particular, embodiments are applicable also to 3GPP LTE, or 3GPP LTE and NR integration, also denoted as non-standalone NR.

Embodiments herein relate to wireless communication networks in general. Fig. 2 is a schematic overview depicting a wireless communication network 1. The wireless communication network 1 comprises one or more RANs and one or more CNs. The wireless communication network 1 may use one or a number of different technologies, such as Wi-Fi, Long Term Evolution (LTE), LTE-Advanced, Fifth Generation (5G), Wideband Code Division Multiple Access (WCDMA), Global System for Mobile communications/enhanced Data rate for GSM Evolution (GSM/EDGE), Worldwide Interoperability for Microwave Access (WiMax), or Ultra Mobile Broadband (UMB), just to mention a few possible implementations. Embodiments herein relate to recent technology trends that are of particular interest in a 5G context, however, embodiments are also applicable in further development of the existing wireless communication systems such as e.g. WCDMA and LTE.

In the wireless communication network 1 , wireless devices e.g. a first UE 10 also denoted as a transmitter UE 10 or just the UE, such as a mobile station, a non-access point (non-AP) STA, a STA, a user equipment and/or a wireless terminal, communicate via one or more Access Networks (AN), e.g. RAN, to one or more core networks (CN). It should be understood by the skilled in the art that “UE” is a non-limiting term which means any terminal, wireless communication terminal, user equipment, Machine Type Communication (MTC) device, Device to Device (D2D) terminal, or node e.g. smart phone, laptop, mobile phone, sensor, relay, mobile tablets or even a small base station capable of communicating using radio communication with a network node within an area served by the network node.

The wireless communication network 1 comprises a radio network node 12 providing radio coverage over a geographical area, a first service area 11, of a radio access technology (RAT), such as LTE, Wi-Fi, WiMAX or similar. The radio network node 12 may be a transmission and reception point e.g. a radio network node such as a Wireless Local Area Network (WLAN) access point or an Access Point Station (AP STA), an access node, an access controller, a base station, e.g. a radio base station such as a NodeB, an evolved Node B (eNB, eNode B), a gNodeB (gNB), a base transceiver station, a radio remote unit, an Access Point Base Station, a base station router, a transmission arrangement of a radio base station, a stand-alone access point or any other network unit or node capable of communicating with a UE within the area served by the radio network node 12 depending e.g. on the radio access technology and terminology used. The radio network node 12 may alternatively or additionally be a controller node or a packet processing node such as a radio controller node or similar. It should be noted that a service area may be denoted as cell, beam, beam group, or similar, to define an area of radio coverage.

The radio network node 12 may be referred to as a serving network node wherein the first service area may be referred to as a serving cell or primary cell, and the serving network node communicates with the UEs in form of DL transmissions to the UEs and UL transmissions from the UEs. The wireless communication network 1 further comprises a second UE 13, also referred to as a receiver UE, communicating with the radio network node and the first UE 10. The second UE 13 may, for example, communicate with the first UE 10.

Embodiments herein relate to communication over a path between the first and second UE using resources configured by the radio network node 12, also denoted as a sidelink. The embodiments are described in the context of NR, i.e. , the UEs are deployed in a same or different NR cells. The embodiments are also applicable to other scenarios including UE to network relay or UE to UE relay where the link between first UE and second UE may be based on LTE sidelink or NR sidelink. The connection between the first UE and the second UE is also not limited to a sidelink, and any short-range communication technology such as Wi-Fi is equally applicable. In the below embodiments, any grant issued by the radio network node 12 is for a sidelink transmission between two UEs.

Note that, in a general scenario, the term “radio network node” can be substituted with “transmission point”. Distinction between the transmission points (TPs) may typically be based on cell reference signals (CRS) or different synchronization signals transmitted. Several TPs may be logically connected to the same radio network node, but, if they are geographically separated or are pointing in different propagation directions, the TPs may be subject to the same mobility issues as different radio network nodes. In subsequent sections, the terms “radio network node” and “TP” can be thought of as interchangeable.

The embodiments are described in the context of NR, i.e., the first UE 10 performs NR sidelink transmission to the second UE 13. The embodiments are also applicable to UEs performing for example LTE sidelink transmissions. In the below embodiments, a non-idle HARQ process is defined as a HARQ process whose associated MAC protocol data unit (PDU) has been submitted to lower layers for transmission but for which successful reception acknowledgment has not been received yet from the receiver. A non-idle HARQ process may be also referred as to a pending HARQ process. The below embodiments are not limited by terms. Any similar term is equally applicable.

In the below embodiments, the term “a signaling to reactivation/reactivation signaling” is used to represent the signaling which is used by the radio network node to reactivate/reconfigure a SL configured grant (CG) configuration. The signaling is different for different types of CG configuration. In case of Type 1 SL CG, the radio network node uses a RRC signaling to reactivate/reconfigure a Type 1 SL CG configuration. In case of Type 2 SL CG, the radio network node uses a DCI signaling to reactivate/reconfigure a Type 2 SL CG configuration.

Embodiments herein enable one or more of the following advantages: a configuration with a high flexibility of handling configured resources, and/or also where configured resources are efficiently used considering service QoS requirements; QoS requirements of different services that share the same configured resource may be achieved and/or a reduced latency since the UE 10 may not have TBs in its buffer without knowing what to do.

Thus, in case a UE such as the first UE 10, referred hereafter as the UE 10, receives a signaling to reactivate a SL CG configuration, the UE 10 takes at least one of below options to handle each non-idle HARQ process which includes TBs.

Option 1 : The UE 10 may immediately flush the HARQ buffer of HARQ processes containing TBs which are being transmitted/retransmitted using the old configured SL grant, regardless if the new grant provides the same TBS as the old configured SL grant.

Option 2: The UE 10 may send a HARQ indication to the radio network node 12, informing that there are pending HARQ processes which need to be scheduled for further retransmissions. The HARQ indication may be a NACK or information defining which TBs to be retransmitted. After sending such indication, the UE 10 may start a timer. After the timer is expired, if the UE 10 doesn’t receive any dynamic grant for the pending HARQ processes, the UE 10 may flush the HARQ buffer of the pending HARQ processes. In this option, the UE 10 will not check if the new grant provides the same TBS as the old configured SL grant. For Option 1 , the TBs which are pending are cleared immediately. Those corresponding HARQ processes will be released and ready for new transmissions. In addition, the UE 10 may also immediately trigger upper layer retransmissions, e.g., radio link control (RLC), or Packet Data Convergence Protocol (PDCP).

For Option 2, the UE 10 may send the HARQ indication to the radio network node 12 via at least one of the below signalling alternatives:

• Dedicated RRC signalling. For example, the UE 10 may use assistance information or the sidelink UE information procedure to carry such HARQ indication. Alternatively, a new RRC signalling message may be defined.

• MAC control element (CE). A new MAC CE may be defined accordingly.

• Physical uplink control channel (PUCCH) signalling. The UE may use specific PUCCH resources to send signalling.

• Physical random access channel (PRACH) signalling. The UE 10 may use specific PRACH preambles or PRACH resources, e.g., RACH occasions (RO), to send signalling.

For any of the above signalling alternatives, the signalling may include at least one of the below information elements (IE):

• Indices of the HARQ processes containing TBs which are being transmitted or retransmitted using the SL grant which needs to be reactivated corresponding to the received SL CG reactivation signalling.

• TBS of those pending TBs.

• Logical channels (LCH) and/or logical channel groups (LCG) associated with those pending TBs.

• Services or traffic types associated with those pending TBs.

• Remaining packet delay budgets of those pending TBs.

For PUCCH signaling, it may be sufficient for the UE 10 to transmit negative HARQ acknowledgement for each pending HARQ process, this would trigger the radio network node 12 to schedule new grants for retransmissions. Alternatively, the UE 10 may trigger an SR for pending TBs.

For Option 2, a new timer may be defined for each non-idle HARQ process. The timer is started after the UE 10 has sent the signaling to the radio network node 12. While the timer is running, the UE 10 does not flush the HARQ buffer of the pending HARQ processes. While the timer is running, if the UE 10 receives a dynamic grant for a pending HARQ process, the UE 10 may use the grant to retransmit the TB. Meanwhile, the timer is stopped. If the time is expired, while the UE 10 has not received any dynamic grant for a pending HARQ process, the UE 10 may flush the HARQ buffer of the pending HARQ process.

The duration/value of this timer may be equal to the remaining packet delay budget, after which the transmission is not valid anymore, or the value can be also equal to the remaining PDB minus a delta. The delta can be decided by the radio network node 12, preconfigured/hardcoded into the specification, or decided autonomously by the UE 10. Alternatively, the duration of the timer can be decided by the radio network node, decided autonomously by the UE 10 or hardcoded in the specification. The duration of the timer may also be linked to a certain PDB, QoS profile, application or service. Again, the mapping between the duration of the timer and the PDB/QoS profile/service/application, may be hardcoded in the specification or decided by the radio network node 12. Alternatively, the value of the timer may be in absolute time units, e.g., ms, or in multiples of the CG periodicity.

Option 3: The UE 10 may use a new grant, i.e. the CG configuration, to retransmit the pending TBs. The UE 10 may check if the new grant is able to provide the same TBS as the old grant. If the answer is yes, the UE 10 may just use the new grant to retransmit pending TBs using the same TBS. If the answer is no, the UE 10 may perform ratematching for pending TBs to fit the new size.

In this option, the UE 10 may apply at least one of the below alternatives to handle the counters, for counting the number of transmissions, including initial transmission and retransmissions, of each TB, for every pending HARQ process:

Alternative 1: The UE 10 may reset the counter to zero; in this case, the UE 10 may retransmit the pending TB up to the maximum number of transmissions configured in the new grant.

Alternative 2: The UE 10 may keep the counter value unchanged; in this case, the UE 10 may retransmit the pending TB up to the remaining number of transmissions, i.e., the maximum number of transmissions configured in the new grant minus the counter value.

For any of the above options, for the UE 10, which option is applied may be configured by the radio network node 12 or a controlling UE via at least one of the below signaling alternatives:

• RRC signaling

• MAC CE

• L1 signaling such as DCI on PDCCH, SCI • Control PDlls of a protocol layer such as SDAP, PDCP, RLC or adaptation layer (e.g., in a relay scenario)

Alternatively, which option is applied by the UE 10 may be captured in standard specifications in a hard-coded fashion. Alternatively, which option is applied by the UE 10 may be specified in pre-configuration.

In case the UE 10 receives a signaling to reactivate a SL CG configuration, the UE 10 may reset the counter of each pending HARQ process for counting number of transmissions, including both initial transmission and retransmissions, of each TB to be zero.

The reactivation signalling may comprise a HARQ process ID field. In this case, the UE 10 may only flush the HARQ buffer of the indicated HARQ process, and may reset the counter of each pending HARQ process for counting number of transmissions, including both initial transmission and retransmissions, of each TB to be zero.

The UE 10 may perform first Option 1 and then Option 2. This means that the UE 10, in case the UE 10 receives a signalling to reactivate a SL CG configuration, first flushes the HARQ buffer of HARQ processes containing TBs which are being transmitted/retransmitted using the configured SL grant. After doing it, the UE may send a flush indication to the radio network node 12 for informing that the buffer of certain HARQ processes have been flushed. Thus, the flush indication to the radio network node 12 may just be for information and not to require new grants to (re)transmit the remaining TBs.

For any of above embodiments, in addition to the proposed UE actions on how to handle the HARQ process, the UE 10 may also perform an additional action to set the new data indicator (NDI) bits to zero for all HARQ processes, optionally, all non-idle HARQ processes, in a CG configuration when the UE receives a reactivation signalling for the CG configuration.

For any of the above embodiments, the embodiment is applicable to both Type 1 Configured grant reactivation/reconfiguration, and Type 2 configured grant reactivation.

Fig. 3 is a combined flowchart and signalling scheme according to embodiments herein. The actions may be performed in any suitable order.

Action 301. The first UE 10 communicates with the second UE 13 using a SL configuration, wherein resources are used according to, for example, a first SLCG. The first UE 10 has sent a number of packets or TBs to the second UE 13 and has one or more active HARQ processes, awaiting confirmation or non-confirmation, for one or more transmitted packets or TBs. The HARQ process may thus be referred to a non-idle HARQ process or a pending HARQ process.

Action 302. The radio network node 12 may transmit an indication of a reactivation of a CG configuration. The signaling from the radio network node 12 is different for different types of CG configuration. In case of Type 1 SL CG, the radio network node 12 may use a RRC signaling to reactivate/reconfigure a Type 1 SL CG configuration. In case of Type 2 SL CG, the radio network node 12 may use a DCI signaling to reactivate/reconfigure a Type 2 SL CG configuration.

Action 303. The first UE 10 then performs, upon receiving the indication, the one or more of the following:

Action 303a. The first UE 10 flushes all packets or TBs in one or more non inactive HARQ buffers.

Action 303b1. The first UE 10 may, alternatively or additionally, send indication to the radio network node 12 relating to a HARQ buffer or a HARQ process at the UE 10.

Action 303b2. The radio network node 12 may in some embodiments, for example, in case the indication is NACK or data stating that the UE has TBs in one or more HARQ buffers, transmit a grant for the UE to retransmit the TBs.

Action 303b3. The first UE 10 may then retransmit the buffered TBs using the resources of the grant/the SLCG.

Action 303c. The first UE 10 may, alternatively or additionally, compare TBS of the SLCG configuration, and based on that either send the TBs using the received SLCG configuration, or send the TBs using rate matching, i.e. adapting buffered TBs to the new SLCG configuration.

The method actions performed by the UE 10 for handling communication over the sidelink in the wireless communication network according to embodiments will now be described with reference to a flowchart depicted in Fig. 4. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes.

Action 401. The UE 10 may communicate with the second UE 13 wherein one or more TBs are buffered in HARQ buffers not yet confirmed received nor not received, also referred to as transmitted data. Thus, the UE 10 have one or more non-idle HARQ processes. Action 402. The UE 10 may receive an indication to reactivate or activate a sidelink configuration. The sidelink configuration may be a sidelink configured grant (SLCG) configuration.

Action 403. The UE 10, upon receiving the indication to reactivate or activate the sidelink configuration, performs one of the following:

Action 40310. The UE 10 flushes the transmitted data, that are not confirmed received at another UE, in the HARQ buffer of a non-idle HARQ process.

Action 40320. The UE 10 sends the HARQ indication to the radio network node 12, wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data. The HARQ indication may indicate that there are pending transmitted data for further retransmissions at the UE for one or multiple HARQ processes. The HARQ indication may be a NACK.

Action 40321. The UE 10 may initiate a timer upon sending the HARQ indication.

Action 40322. The UE 10 may receive a grant from the radio network node 12.

Action 40323. The UE 10 may then retransmit the transmitted data, that are not confirmed received at the other UE, using resources of the grant.

Action 40324. The UE 10 may, after the timer is expired and the UE has not received any dynamic grant for pending HARQ processes, then flush the transmitted data in the HARQ buffer of the pending HARQ processes.

Action 40330. The UE 10 sends the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size (TBS) of the sidelink configuration with TBS of previous sidelink configuration. The UE 10 may send the transmitted data based on the matching of the TBSs by comparing TBS of the sidelink configuration with TBS of previous sidelink configuration, and based on that, either send the transmitted data using the sidelink configuration, or send the transmitted data adapting buffered transport blocks to the sidelink configuration.

Thus, the UE 10 may, upon receiving a signaling to reactivate a sidelink configuration, such as a SLCG configuration, perform one or more of the following: flushing the transmitted data in a HARQ buffer of a non-idle HARQ process; and/or sending an indication to the radio network node, wherein the indication relates to the HARQ buffer or HARQ process for example informing that there are pending transmitted data for further retransmissions at the UE, or sending the data to a UE based on matching TBS of sidelink configuration compared with previous sidelink configuration.

The method actions performed by the radio network node for handling communication over the sidelink between UEs communicating in the wireless communication network according to embodiments of the present disclosure will now be described with reference to a flowchart depicted in Fig. 5. The actions do not have to be taken in the order stated below, but may be taken in any suitable order. Actions performed in some embodiments are marked with dashed boxes.

Action 501. The radio network node 12 may transmit a configuration to a UE configuring the UE to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send an HARQ indication to the radio network node 12, wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size, TBS, of the received sidelink configuration with TBS of previous sidelink configuration. Hence, the radio network node 12 may configure the UE 10 to, upon receiving a signaling to reactivate a sidelink configuration, such as a SLCG configuration, decide to handle transmitted data, such as transport blocks that are not confirmed received at another UE, by flushing the transmitted data in a HARQ buffer of a non-idle HARQ process; and/or sending an indication to the radio network node, wherein the indication relates to the HARQ buffer or HARQ process for example informing that there are pending transmitted data for further retransmissions at the UE, or sending NACK; or by sending the data of the HARQs to the other UE based on matching TBS of sidelink configuration compared with previous sidelink configuration.

Action 502. The radio network node 12 may transmit to the UE 10, the indication to reactivate or activate the sidelink configuration at the UE such as an indication to reactivate SLCG configuration at the UE 10. Thus, the sidelink configuration may be a sidelink configured grant configuration.

Action 503. The radio network node 12 may then receive the HARQ indication from the UE 10, wherein the HARQ indication relates to the HARQ buffer or HARQ process, for example, informing that there are pending transmitted data for further retransmissions at the UE 10 for one or multiple HARQ processes. The HARQ indication may be a NACK.

Action 504. The radio network node 12 may transmit a grant to the UE 10.

Action 505. The radio network node 12 may receive the transmitted data, that are not confirmed received at the other UE, on resources of the grant.

Fig. 6 is a block diagram depicting the first UE 10 for handling communication over the sidelink in the wireless communication network according to embodiments herein.

The UE 10 may comprise processing circuitry 601 , e.g. one or more processors, configured to perform the methods herein.

The UE 10 may comprise a receiving unit 602, e.g. a receiver or a transceiver. The UE 10, the processing circuitry 601 , and/or the receiving unit 602 may be configured to receive an indication to reactivate activate the sidelink configuration, such as a SLCG configuration.

The UE 10 may comprise a determining unit 603. The UE 10, the processing circuitry 601, and/or the determining unit 603 is configured to, upon receiving the indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send a HARQ indication to the radio network node 12, wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration.

Thus, the UE 10, the processing circuitry 601, and/or the determining unit 603 may be configured to decide, upon receiving the indication to reactivate the CG configuration, to handle transmitted data, such as transport blocks that are not confirmed received at another UE, by flushing the transmitted data in a HARQ buffer of a non-idle HARQ process and/or by sending the HARQ indication to the radio network node, wherein the HARQ indication relates to the HARQ buffer or HARQ process for example informing that there are pending transmitted data for further retransmissions at the UE, or sending NACK; or by sending the data of the HARQs to the other UE based on matching TBS of sidelink configuration compared with previous sidelink configuration. The HARQ indication may indicate that there are pending transmitted data for further retransmissions at the UE for one or multiple HARQ processes. The HARQ indication may be a NACK.

The UE 10, the processing circuitry 601, and/or the determining unit 603 may be configured to send the transmitted data based on the matching of the TBSs by comparing TBS of the sidelink configuration with TBS of previous sidelink configuration and based on that either configured to send the transmitted data using the sidelink configuration, or to send the transmitted data adapting buffered transport blocks to the sidelink configuration.

The UE 10, the processing circuitry 601, and/or the determining unit 603 may be configured to initiate the timer upon sending the HARQ indication and after the timer is expired, if the UE does not receive any dynamic grant for pending HARQ processes, configured to flush the transmitted data in the HARQ buffer of the pending HARQ processes.

The UE 10, the processing circuitry 601, and/or the receiving unit 602 may be configured to receive the grant from the radio network node 12.

The UE 10, the processing circuitry 601 , and/or the determining unit 603 may be configured to retransmit the transmitted data, that are not confirmed received at the other UE, using resources of the grant.

The UE 10 further comprises a memory 606. The memory comprises one or more units to be used to store data on, such as indications, SLCG, requests, configuration, strengths or qualities, UL grants, indications, requests, commands, timers, applications to perform the methods disclosed herein when being executed, and similar. Thus, the UE may comprise the processing circuitry and the memory, said memory comprising instructions executable by said processing circuitry whereby said UE 10 is operative to perform the methods herein. The UE 10 comprises a communication interface 609 comprising e.g. one or more antennas.

The methods according to the embodiments described herein for the UE 10 are respectively implemented by means of e.g. a computer program product 607 or a computer program, comprising instructions, i.e. , software code portions, which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the UE 10. The computer program product 607 may be stored on a computer-readable storage medium 608, e.g. a universal serial bus (USB) stick, a disc, or similar. The computer-readable storage medium 608, having stored thereon the computer program product, may comprise the instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the UE 10. In some embodiments, the computer-readable storage medium may be a non-transitory or a transitory computer- readable storage medium.

Fig. 7 is a block diagram depicting the radio network node 12, in two embodiments, for handling communication over the sidelink between UEs in the wireless communication network.

The radio network node 12 may comprise processing circuitry 701 , e.g. one or more processors, configured to perform the methods herein.

The radio network node 12 may comprise a transmitting unit 702, e.g. a transmitter or a transceiver. The radio network node 12, the processing circuitry 701 and/or the transmitting unit 702 is configured to transmit the configuration to the UE 10 configuring the UE 10 to, upon receiving the indication to reactivate or activate the sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a HARQ buffer of a non-idle HARQ process; send an HARQ indication to the radio network node 12, wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching TBS of the sidelink configuration with TBS of previous sidelink configuration.

Thus, the radio network node 12, the processing circuitry 701 and/or the transmitting unit 702 may be configured to configure the first UE 10 to, upon receiving a signaling to reactivate a sidelink configuration, such as a SLCG configuration, decide to handle transmitted data, such as transport blocks that are not confirmed received at another UE, by flushing the transmitted data in a HARQ buffer of a non-idle HARQ process, and/or sending an indication to the radio network node 12, wherein the indication relates to the HARQ buffer or HARQ process for example informing that there are pending transmitted data for further retransmissions at the UE, or sending NACK; or by sending the data of the HARQs to the other UE based on matching TBS of sidelink configuration compared with previous sidelink configuration.

The radio network node 12, the processing circuitry 701 and/or the transmitting unit 702 may be configured to transmit the indication to reactivate or activate the sidelink configuration at the UE for example a SLCG configuration.

The radio network node 12 may comprise a receiving unit 703, e.g. a receiver or a transceiver. The radio network node 12, the processing circuitry 701 and/or the receiving unit 702 may be configured to receive the HARQ indication from the UE 10, wherein the HARQ indication relates to the HARQ buffer or HARQ process. The HARQ indication may indicate that there are pending transmitted data for further retransmissions at the UE for one or multiple HARQ processes. The HARQ indication may be a NACK.

The radio network node 12, the processing circuitry 701 and/or the transmitting unit 702 may be configured to transmit the grant to the UE 10. The radio network node 12, the processing circuitry 701 and/or the receiving unit 702 may be configured to then receive the transmitted data, which are not confirmed received at the other UE, on resources of the grant.

The radio network node 12 further comprises a memory 705. The memory comprises one or more units to be used to store data on, such as indications, configurations, strengths or qualities, grants, scheduling information, timers, applications to perform the methods disclosed herein when being executed, and similar. The radio network node 12 comprises a communication interface 708 comprising e.g. transmitter, receiver, transceiver and/or one or more antennas.

The methods according to the embodiments described herein for radio network node 12 are respectively implemented by means of e.g. a computer program product 706 or a computer program product, comprising instructions, i.e., software code portions, which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the radio network node 12. The computer program product 706 may be stored on a computer-readable storage medium 707, e.g. a USB stick, a disc or similar. The computer-readable storage medium 707, having stored thereon the computer program product, may comprise the instructions which, when executed on at least one processor, cause the at least one processor to carry out the actions described herein, as performed by the radio network node 12. In some embodiments, the computer-readable storage medium may be a non-transitory or transitory computer-readable storage medium.

In some embodiments a more general term “radio network node” is used and it can correspond to any type of radio network node or any network node, which communicates with a wireless device and/or with another network node. Examples of network nodes are NodeB, Master eNB, Secondary eNB, a network node belonging to Master cell group (MCG) or Secondary Cell Group (SCG), base station (BS), multistandard radio (MSR) radio node such as MSR BS, eNodeB, network controller, radio network controller (RNC), base station controller (BSC), relay, donor node controlling relay, base transceiver station (BTS), access point (AP), transmission points, transmission nodes, Remote Radio Unit (RRU), Remote Radio Head (RRH), nodes in distributed antenna system (DAS), core network node e.g. Mobility Switching Centre (MSC), Mobile Management Entity (MME) etc., Operation and Maintenance (O&M), Operation Support System (OSS), Self-Organizing Network (SON), positioning node e.g. Evolved Serving Mobile Location Centre (E-SMLC), Minimizing Drive Test (MDT), etc.

In some embodiments, the non-limiting term wireless device or user equipment (UE) is used and it refers to any type of wireless device communicating with a network node and/or with another UE in a cellular or mobile communication system. Examples of UE are target device, device-to-device (D2D) UE, proximity capable UE (aka ProSe UE), machine type UE or UE capable of machine to machine (M2M) communication, PDA, PAD, Tablet, mobile terminals, smart phone, laptop embedded equipped (LEE), laptop mounted equipment (LME), USB dongles etc.

The embodiments are described for 5G. However the embodiments are applicable to any RAT or multi-RAT systems, where the UE receives and/or transmit signals (e.g. data) e.g. LTE, LTE FDD/TDD, WCDMA/HSPA, GSM/GERAN, Wi Fi, WLAN, CDMA2000 etc.

As will be readily understood by those familiar with communications design, functions means or modules may be implemented using digital logic and/or one or more microcontrollers, microprocessors, or other digital hardware. In some embodiments, several or all of the various functions may be implemented together, such as in a single application-specific integrated circuit (ASIC), or in two or more separate devices with appropriate hardware and/or software interfaces between them. Several of the functions may be implemented on a processor shared with other functional components of a wireless device or network node, for example.

Alternatively, several of the functional elements of the processing means discussed may be provided through the use of dedicated hardware, while others are provided with hardware for executing software, in association with the appropriate software or firmware. Thus, the term “processor” or “controller” as used herein does not exclusively refer to hardware capable of executing software and may implicitly include, without limitation, digital signal processor (DSP) hardware, read-only memory (ROM) for storing software, random-access memory for storing software and/or program or application data, and non-volatile memory. Other hardware, conventional and/or custom, may also be included. Designers of communications devices will appreciate the cost, performance, and maintenance trade-offs inherent in these design choices. With reference to Fig 8, in accordance with an embodiment, a communication system includes a telecommunication network 3210, such as a 3GPP-type cellular network, which comprises an access network 3211, such as a radio access network, and a core network 3214. The access network 3211 comprises a plurality of base stations 3212a, 3212b, 3212c, such as NBs, eNBs, gNBs or other types of wireless access points being examples of the radio network node 12 herein, each defining a corresponding coverage area 3213a, 3213b, 3213c. Each base station 3212a, 3212b, 3212c is connectable to the core network 3214 over a wired or wireless connection 3215. A first user equipment (UE) 3291, being an example of the UE 10 and relay UE 13, located in coverage area 3213c is configured to wirelessly connect to, or be paged by, the corresponding base station 3212c. A second UE 3292 in coverage area 3213a is wirelessly connectable to the corresponding base station 3212a. While a plurality of UEs 3291 , 3292 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 3212.

The telecommunication network 3210 is itself connected to a host computer 3230, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 3230 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. The connections 3221, 3222 between the telecommunication network 3210 and the host computer 3230 may extend directly from the core network 3214 to the host computer 3230 or may go via an optional intermediate network 3220. The intermediate network 3220 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 3220, if any, may be a backbone network or the Internet; in particular, the intermediate network 3220 may comprise two or more sub-networks (not shown).

The communication system of Fig. 8 as a whole enables connectivity between one of the connected UEs 3291 , 3292 and the host computer 3230. The connectivity may be described as an over-the-top (OTT) connection 3250. The host computer 3230 and the connected UEs 3291, 3292 are configured to communicate data and/or signaling via the OTT connection 3250, using the access network 3211 , the core network 3214, any intermediate network 3220 and possible further infrastructure (not shown) as intermediaries. The OTT connection 3250 may be transparent in the sense that the participating communication devices through which the OTT connection 3250 passes are unaware of routing of uplink and downlink communications. For example, a base station 3212 may not or need not be informed about the past routing of an incoming downlink communication with data originating from a host computer 3230 to be forwarded (e.g., handed over) to a connected UE 3291. Similarly, the base station 3212 need not be aware of the future routing of an outgoing uplink communication originating from the UE 3291 towards the host computer 3230.

Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Fig. 9. In a communication system 3300, a host computer 3310 comprises hardware 3315 including a communication interface 3316 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 3300. The host computer 3310 further comprises processing circuitry 3318, which may have storage and/or processing capabilities. In particular, the processing circuitry 3318 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 3310 further comprises software 3311, which is stored in or accessible by the host computer 3310 and executable by the processing circuitry 3318. The software 3311 includes a host application 3312. The host application 3312 may be operable to provide a service to a remote user, such as a UE 3330 connecting via an OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the remote user, the host application 3312 may provide user data which is transmitted using the OTT connection 3350.

The communication system 3300 further includes a base station 3320 provided in a telecommunication system and comprising hardware 3325 enabling it to communicate with the host computer 3310 and with the UE 3330. The hardware 3325 may include a communication interface 3326 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 3300, as well as a radio interface 3327 for setting up and maintaining at least a wireless connection 3370 with a UE 3330 located in a coverage area (not shown in Fig.9) served by the base station 3320. The communication interface 3326 may be configured to facilitate a connection 3360 to the host computer 3310. The connection 3360 may be direct or it may pass through a core network (not shown in Fig.9) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 3325 of the base station 3320 further includes processing circuitry 3328, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 3320 further has software 3321 stored internally or accessible via an external connection.

The communication system 3300 further includes the UE 3330 already referred to. Its hardware 3335 may include a radio interface 3337 configured to set up and maintain a wireless connection 3370 with a base station serving a coverage area in which the UE 3330 is currently located. The hardware 3335 of the UE 3330 further includes processing circuitry 3338, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 3330 further comprises software 3331 , which is stored in or accessible by the UE 3330 and executable by the processing circuitry 3338. The software 3331 includes a client application 3332. The client application 3332 may be operable to provide a service to a human or non-human user via the UE 3330, with the support of the host computer 3310. In the host computer 3310, an executing host application 3312 may communicate with the executing client application 3332 via the OTT connection 3350 terminating at the UE 3330 and the host computer 3310. In providing the service to the user, the client application 3332 may receive request data from the host application 3312 and provide user data in response to the request data. The OTT connection 3350 may transfer both the request data and the user data. The client application 3332 may interact with the user to generate the user data that it provides.

It is noted that the host computer 3310, base station 3320 and UE 3330 illustrated in Fig. 9 may be identical to the host computer 3230, one of the base stations 3212a, 3212b, 3212c and one of the UEs 3291, 3292 of Fig. 8, respectively. This is to say, the inner workings of these entities may be as shown in Fig. 9 and independently, the surrounding network topology may be that of Fig. 8.

In Fig. 9, the OTT connection 3350 has been drawn abstractly to illustrate the communication between the host computer 3310 and the user equipment 3330 via the base station 3320, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 3330 or from the service provider operating the host computer 3310, or both. While the OTT connection 3350 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

The wireless connection 3370 between the UE 3330 and the base station 3320 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 3330 using the OTT connection 3350, in which the wireless connection 3370 forms the last segment. More precisely, the teachings of these embodiments may improve the performance since transmitted data or TBs are handled more efficiently and thereby provide benefits such as reduced user waiting time, and better responsiveness.

A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 3350 between the host computer 3310 and UE 3330, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 3350 may be implemented in the software 3311 of the host computer 3310 or in the software 3331 of the UE 3330, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 3350 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which software 3311, 3331 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 3350 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 3320, and it may be unknown or imperceptible to the base station 3320. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer’s 3310 measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 3311 , 3331 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 3350 while it monitors propagation times, errors etc.

Fig. 10 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 8 and 9. For simplicity of the present disclosure, only drawing references to Fig. 10 will be included in this section. In a first step 3410 of the method, the host computer provides user data. In an optional substep 3411 of the first step 3410, the host computer provides the user data by executing a host application. In a second step 3420, the host computer initiates a transmission carrying the user data to the UE. In an optional third step 3430, the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional fourth step 3440, the UE executes a client application associated with the host application executed by the host computer.

Fig. 11 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 8 and 9. For simplicity of the present disclosure, only drawing references to Fig. 11 will be included in this section. In a first step 3510 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In a second step 3520, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In an optional third step 3530, the UE receives the user data carried in the transmission.

Fig. 12 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 8 and 9. For simplicity of the present disclosure, only drawing references to Fig. 12 will be included in this section. In an optional first step 3610 of the method, the UE receives input data provided by the host computer. Additionally or alternatively, in an optional second step 3620, the UE provides user data. In an optional substep 3621 of the second step 3620, the UE provides the user data by executing a client application. In a further optional substep 3611 of the first step 3610, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in an optional third substep 3630, transmission of the user data to the host computer. In a fourth step 3640 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

Fig. 13 is a flowchart illustrating a method implemented in a communication system, in accordance with one embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Figs. 8 and 9. For simplicity of the present disclosure, only drawing references to Fig. 13 will be included in this section. In an optional first step 3710 of the method, in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In an optional second step 3720, the base station initiates transmission of the received user data to the host computer. In a third step 3730, the host computer receives the user data carried in the transmission initiated by the base station.

It will be appreciated that the foregoing description and the accompanying drawings represent non-limiting examples of the methods and apparatus taught herein. As such, the apparatus and techniques taught herein are not limited by the foregoing description and accompanying drawings. Instead, the embodiments herein are limited only by the following claims and their legal equivalents.

ABBREVIATIONS

5G Fifth Generation

ACK Acknowledgment

AMF Access and Mobility Management Function

BWP Bandwidth Part

CE Control element

CP Cyclic Prefix

CSI-RS Channel State Information Reference Signal

DCI Downlink Control Information

DFN Direct Frame Number

DMRS Demodulation Reference Signal gNB gNodeB

HARQ Hybrid Automatic Repeat Request

IE Information Element

LTE Long Term Evolution

MAC Media Access Control MCS Modulation and Coding Scheme

NACK Negative Acknowledgement

NDI New Data Indicator

NR New Radio

OFDM Orthogonal Frequency-Division Multiplexing

PDCCH Physical Downlink Control Channel

PDCP Packet Data Convergence Protocol

PDSCH Physical Downlink Shared Channel

ProSe Proximity-based Services

PSBCH Physical Sidelink Broadcast Channel

PSCCH Physical Sidelink Common Control Channel

PSFCH Physical Sidelink Feedback Channel

PT-RS Tracking Reference Signal

PLICCH Physical Uplink Control Channel

PUSCH Physical Uplink Shared Channel

QoS Quality of Service

RAN Radio Access Network

RB Resource Block

RLC Radio Link Control

RLF Radio Link Failure

RLM Radio Link Monitoring

RNTI Radio Network Temporary Identifier

RRC Radio Resource Control

RSRP Reference Signal Received Power

RSRQ Reference Signal Received Quality

RSSI Received Signal Strength Indicator

RV Redundancy Version

SCI Sidelink Control Information

SCS Sub-Carrier Spacing

SI System Information

SL SideLink

SMF Session Management Function

S-PSS Sidelink Primary Synchronization Signal

SSB Synchronization Signal Block SSID Sidelink Synchronization Identity

S-SSS Sidelink Secondary Synchronization Signal

UCI Uplink Control Information

UE User Equipment

UPF User Plane Function

References

[1] 3GPP TS 23.501, V16.5.0

[2] 3GPP TS 38.321 V16.0.0

[3] 3GPP TR 23.752 V0.3.0

[4] 3GPP TS 23.501 V16.5.0: “System Architecture for the 5G System; Stage

2”.

[5] 3GPP TS 23.287 V16.3.0: “Architecture enhancements for 5G System (5GS) to support Vehicle-to-Everything (V2X) services”.

[6] 3GPP TS 23.303 V16.0.0: “Proximity-based services (ProSe); Stage 2”.

[7] RP-193253 “New SID: Study on NR sidelink relay”.

[8] 3GPP TS 23.502 V16.5.0, “Procedures for the 5G System (5GS); Stage 2”.

[9] 3GPP TS 38.314 V16.0.0, “NR, Layer 2 measurements”.

[10] R2-2008266, “Summary of [AT111 -e][605][Relay] L2 Relay Mechanism” MediaTek Inc., RAN2#111-e.

[11] TS 38.340 V 16.1.0, “Backhaul Adaptation Protocol (BAP) specification”.

Claims

1. A method performed by a user equipment, UE, for handling communication over a sidelink in a wireless communication network, the method comprising, upon receiving (402) an indication to reactivate or activate a sidelink configuration, performing (403) one of the following: flushing (40310) transmitted data, that are not confirmed received at another UE, in a hybrid automatic repeat request, HARQ, buffer of a nonidle HARQ process; sending (40320) a HARQ indication to a radio network node (12), wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or sending (40330) the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size, TBS, of the sidelink configuration with TBS of previous sidelink configuration.

2. The method according to claim 1 , wherein the HARQ indication indicates that there are pending transmitted data for further retransmissions at the UE for one or multiple HARQ processes.

3. The method according to claim 1 , wherein the HARQ indication is a negativeacknowledgement, NACK.

4. The method according to any of the claims 1-3, further comprising initiating (40321) a timer upon sending the HARQ indication, and after the timer is expired, if the UE does not receive any dynamic grant for pending HARQ processes, flushing (40324) the transmitted data in the HARQ buffer of the pending HARQ processes.

5. The method according to any of the claims 1-4, further comprising receiving (40322) a grant from the radio network node (12); and retransmitting (40323) the transmitted data, that are not confirmed received at the other UE, using resources of the grant. The method according to any of the claims 1-5, wherein sending (40330) the transmitted data based on the matching of the TBSs comprises comparing TBS of the sidelink configuration with TBS of previous sidelink configuration and, based on that, either sending the transmitted data using the sidelink configuration, or sending the transmitted data adapting buffered transport blocks to the sidelink configuration. The method according to any of the claims 1-6, wherein the sidelink configuration is a sidelink configured grant configuration. A method performed by a radio network node (12) for handling communication over a sidelink between user equipments, UE, in a wireless communication network, the method comprising: transmitting (501) a configuration to a UE (10) configuring the UE (10) to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a hybrid automatic repeat request, HARQ, buffer of a non-idle HARQ process; send an HARQ indication to the radio network node (12), wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size, TBS, of the sidelink configuration with TBS of previous sidelink configuration. The method according to claim 8, comprising transmitting (502), to the UE (10), the indication to reactivate or activate the sidelink configuration at the UE (10); and receiving (503) the HARQ indication from the UE (10), wherein the HARQ indication relates to the HARQ buffer or HARQ process. The method according to claim 9, wherein the HARQ indication indicates that there are pending transmitted data for further retransmissions at the UE (10) for one or multiple HARQ processes.

11. The method according to claim 9, wherein the HARQ indication is a negativeacknowledgement, NACK.

12. The method according to any of the claims 9-11, further comprising transmitting (504) a grant to the UE (10); and receiving (505) the transmitted data, that are not confirmed received at the other UE, on resources of the grant.

13. The method according to any of the claims 8-12, wherein the sidelink configuration is a sidelink configured grant configuration.

14. A user equipment, UE, (10) for handling communication over a sidelink in a wireless communication network, wherein the UE (10) is configured to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a hybrid automatic repeat request, HARQ, buffer of a non-idle HARQ process; send a HARQ indication to a radio network node (12), wherein the HARQ indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size, TBS, of the sidelink configuration with TBS of previous sidelink configuration.

15. The UE according to claim 14, wherein the HARQ indication indicates that there are pending transmitted data for further retransmissions at the UE for one or multiple HARQ processes.

16. The UE according to claim 14, wherein the HARQ indication is a negativeacknowledgement, NACK.

17. The UE according to any of the claims 14-16, wherein the UE is configured to initiate a timer upon sending the HARQ indication; and after the timer is expired, if the UE doesn’t receive any dynamic grant for pending HARQ processes, configure to flush the transmitted data in the HARQ buffer of the pending HARQ processes. The UE according to any of the claims 14-17, wherein the UE is further configured to receive a grant from the radio network node (12); and retransmit the transmitted data, that are not confirmed received at the other UE, using resources of the grant. The UE according to any of the claims 14-18, wherein the UE is configured to send the transmitted data based on the matching of the TBSs by comparing TBS of the sidelink configuration with TBS of previous sidelink configuration and, based on that, either send the transmitted data using the sidelink configuration, or to send the transmitted data adapting buffered transport blocks to the sidelink configuration. The UE according to any of the claims 14-19, wherein the sidelink configuration is a sidelink configured grant configuration. A radio network node (12) for handling communication over a sidelink between user equipments, UE, in a wireless communication network, wherein the radio network node (12) is configured to: transmit a configuration to a UE (10) configuring the UE (10) to, upon receiving an indication to reactivate or activate a sidelink configuration, perform one of the following: flush transmitted data, that are not confirmed received at another UE, in a hybrid automatic repeat request, HARQ, buffer of a non-idle HARQ process; send an HARQ indication to the radio network node (12), wherein the indication relates to the HARQ buffer or the non-idle HARQ process of the transmitted data; or send the transmitted data of the HARQ buffer or the non-idle HARQ process to the other UE based on matching transport block size, TBS, of the sidelink configuration with TBS of previous sidelink configuration. The radio network node (12) according to claim 21, wherein the radio network node is configured to transmit, to the UE (10), the indication to reactivate or activate the sidelink configuration at the UE; and receive the HARQ indication from the UE (10), wherein the HARQ indication relates to the HARQ buffer or HARQ process. The radio network node (12) according to claim 22, wherein the HARQ indication indicates that there are pending transmitted data for further retransmissions at the UE (10) for one or multiple HARQ processes. The radio network node (12) according to claim 22, wherein the HARQ indication is a negative-acknowledgement, NACK. The radio network node (12) according to any of the claims 22-24, wherein the radio network node (12) is further configured to transmit a grant to the UE (10); and receive the transmitted data, that are not confirmed received at the other UE, on resources of the grant. The radio network node (12) according to any of the claims 22-25, wherein the sidelink configuration is a sidelink configured grant configuration. A computer program product comprising instructions, which, when executed on at least one processor, cause the at least one processor to carry the method according to any of the claims 1-13, as performed by the radio network node (12) and the UE (10), respectively. A computer-readable storage medium, having stored thereon a computer program product comprising instructions which, when executed on at least one processor, cause the at least one processor to carry out the method according to any of the claims 1-13, as performed by the radio network node (12) and the UE (10), respectively.