EP4111716A1 - Method to flexibly adapt multiplexing of sidelink logical channels in sidelink groupcast - Google Patents

Abstract

Various communication systems may benefit from improved multiplexing of sidelink logical channels in sidelink groupcast. A method may comprise receiving at least one sidelink groupcast from at least one sidelink transmitter. The method may further include determining a distance to the at least one sidelink transmitter and determining one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The method may further include transmitting the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

Description

TITLE:

METHOD TO FLEXIBLY ADAPT MULTIPLEXING OF SIDELINK LOGICAL CHANNELS IN SIDELINK GROUPCAST

TECHNICAL FIELD:

Some example embodiments may generally relate to mobile or wireless telecommunication systems, such as Long Term Evolution (LTE), fifth generation (5G) radio access technology, new radio (NR) access technology, or other communications systems. For example, certain embodiments may relate to systems and/or methods for multiplexing sidelink logical channels having various maximum communication range values.

BACKGROUND:

Examples of mobile or wireless telecommunication systems may include the Universal Mobile Telecommunications System (UMTS) Terrestrial Radio Access Network (UTRAN), Long Term Evolution (LTE) Evolved UTRAN (E-UTRAN), LTE-Advanced (LTE-A), MulteFire, LTE-A Pro, and/or 5G radio access technology or NR access technology. 5G wireless systems refer to the next generation (NG) of radio systems and network architecture. A 5G system is mostly built on a 5G NR, but a 5G (or NG) network can also build on the E-UTRA radio. It is estimated that NR provides bitrates on the order of 10-20 Gbit/s or higher, and can support at least service categories such as enhanced mobile broadband (eMBB) and ultra-reliable low-latency-communication (URLLC) as well as massive machine type communication (mMTC). NR is expected to deliver extreme broadband and ultra-robust, low latency connectivity and massive networking to support the Internet of Things (IoT). With IoT and machine-to-machine (M2M) communication becoming more widespread, there will be a growing need for networks that meet the needs of lower power, low data rate, and long battery life. The next generation radio access network (NG-RAN) represents the RAN for 5G, which can provide both NR and LTE (and LTE-Advanced) radio accesses. It is noted that, in 5G, the nodes that can provide radio access functionality to a user equipment (i.e., similar to the Node B (NB) in UTRAN or the evolved NB (eNB) in LTE) may be named next-generation NB (gNB) when built on NR radio, and may be named next-generation eNB (NG-eNB) when built on E-UTRA radio.

SUMMARY:

In accordance with some embodiments, a method may include receiving at least one sidelink groupcast from at least one sidelink transmitter. The method may further include determining a distance to the at least one sidelink transmitter. The method may further include determining one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The method may further include transmitting the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

In accordance with certain embodiments, an apparatus may include means for receiving at least one sidelink groupcast from at least one sidelink transmitter. The apparatus may further include means for determining a distance to the at least one sidelink transmitter. The apparatus may further include means for determining one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The apparatus may further include means for transmitting the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

In accordance with various embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to at least receive at least one sidelink groupcast from at least one sidelink transmitter. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least determine a distance to the at least one sidelink transmitter. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least determine one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least transmit the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

In accordance with some embodiments, a non-transitory computer readable medium may be encoded with instructions that may, when executed in hardware, perform a method. The method may include receiving at least one sidelink groupcast from at least one sidelink transmitter. The method may further include determining a distance to the at least one sidelink transmitter. The method may further include determining one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The method may further include transmitting the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

In accordance with certain embodiments, a computer program product may perform a method. The method may include receiving at least one sidelink groupcast from at least one sidelink transmitter. The method may further include determining a distance to the at least one sidelink transmitter. The method may further include determining one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The method may further include transmitting the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence. In accordance with various embodiments, an apparatus may include circuitry configured to receive at least one sidelink groupcast from at least one sidelink transmitter. The circuitry may further be configured to determine a distance to the at least one sidelink transmitter. The circuitry may further be configured to determine one or more of at least one configured resource or ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter. The circuitry may further be configured to transmit the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence.

In accordance with some embodiments, a method may include transmitting at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The method may further include receiving at least one sidelink feedback from the at least one sidelink receiver. The method may further include determining at least one distance range to the at least one sidelink receiver associated with the at least one sidelink feedback. The method may further include adjusting at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

In accordance with certain embodiments, an apparatus may include means for transmitting at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The apparatus may further include means for receiving at least one sidelink feedback from the at least one sidelink receiver. The apparatus may further include means for determining at least one distance range to the at least one sidelink receiver associated with the at least one sidelink feedback. The apparatus may further include means for adjusting at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

In accordance with various embodiments, an apparatus may include at least one processor and at least one memory including computer program code. The at least one memory and the computer program code may be configured to, with the at least one processor, cause the apparatus to at least transmit at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least receive at least one sidelink feedback from the at least one sidelink receiver. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least determine at least one distance range to the at least one SL receiver associated with the at least one sidelink feedback. The at least one memory and the computer program code may be further configured to, with the at least one processor, cause the apparatus to at least adjust at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

In accordance with some embodiments, a non-transitory computer readable medium may be encoded with instructions that may, when executed in hardware, perform a method. The method may include transmitting at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The method may further include receiving at least one sidelink feedback from the at least one sidelink receiver. The method may further include determining at least one distance range to the at least one SL receiver associated with the at least one sidelink feedback. The method may further include adjusting at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

In accordance with certain embodiments, a computer program product may perform a method. The method may include transmitting at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The method may further include receiving at least one sidelink feedback from the at least one sidelink receiver. The method may further include determining at least one distance range to the at least one

SL receiver associated with the at least one sidelink feedback. The method may further include adjusting at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback. In accordance with various embodiments, an apparatus may include circuitry configured to transmit at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different MCRs. The circuitry may further be configured to receive at least one sidelink feedback from the at least one sidelink receiver. The circuitry may further be configured to determine at least one distance range to the at least one SL receiver associated with the at least one sidelink feedback. The circuitry may further be configured to adjust at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

BRIEF DESCRIPTION OF THE DRAWINGS:

For proper understanding of example embodiments, reference should be made to the accompanying drawings, wherein:

FIG. 1 illustrates an example of generating transport blocks. FIG. 2 illustrates an example of a plurality of sidelink transmitting and receiving entities. FIG. 3 illustrates an example of a signaling diagram according to certain embodiments. FIG. 4 illustrates an example of a flow diagram of a method performed by a sidelink transmitter according to certain embodiments.

FIG. 5 illustrates an example of a flow diagram of a method performed by a sidelink receiver according to certain embodiments.

FIG. 6 illustrates an example of various network devices according to certain embodiments.

FIG. 7 illustrates an example of a 5G network and system architecture according to certain embodiments.

DETAILED DESCRIPTION:

In vehicular communications, such as Long-Term Evolution vehicle-to-everything (LTE-V2X) and new radio vehicle-to-everything (NR-V2X), the maximum communication range (MCR) refers to a transmission range for communications for a group of user equipment (UE) with certain quality of service (QoS) requirements.

For example, in LTE-V2X 3GPP technical specification (TS) 36.213, sidelink transmission power control at a transmitter (TX) may consider the cellular link path loss to control the signal power received by a base station from the SL TX. This may mitigate any interference from the SL to uplink (UL), and any SL transmit power may be constrained by a maximum transmit power, which may be a function of the UE- measured channel busy radio (CBR) and transport block (TB) priority level. With respect to NR-V2X, the current open-loop power control at the physical sidelink feedback channel (PSFCH) TX may be based on the path loss value between PSFCH TX and its serving network node.

Third Generation Partnership Project (3GPP) Service and System Aspects Working Group 2 (SA2) introduced MCR as a QoS parameter of NR-V2X to improve reliability without affecting latency and resource efficiency. This is particularly relevant for groupcast functionality by allowing UE using sidelink communication to determine whether to send acknowledgement (ACK)/non-acknowledgement (NACK) responses based on whether the UE is within a required range, such as MCR. In this way, any UE outside of the MCR would not attempt to transmit NACKs, thereby reducing hybrid automatic repeat request (HARQ) retransmissions and conserving limited radio resources. Conversely, by receiving HARQ feedback, the sidelink TX is aware of the reception status of the sidelink RXs within the MCR, and HARQ retransmission can be applied to improve the reliability.

Transmission ranges of a sidelink radio bearer (SLRB) may be considered as a SLRB parameter, resulting in each SLRB associating with one or more alternative MCRs. Furthermore, the sidelink control information (SCI) payload may include location information of the transmitting UE. Thus, if a RX UE locates within the MCR may be determined according to a determination by a receiving (RX) UE of its own position, as well as any location information provided by the TX UE.

Logical channel prioritization (LCP) may also be considered with sidelink communications. For example, the medium access control (MAC) layer in the UE may select a destination and cast type associated with the highest SL logical channel (LCH) priority for a new transmission from all the SL LCHs that have data to be transmitted to the same destination using the same cast type. As a result, only data of the SL LCHs associated with the selected destination and cast type may be multiplexed into the MAC protocol data unit (PDU) for transmission. Furthermore, LCP may also be based on whether ACK/NACK functionality is enabled; for example, a HARQ-enabled packet may only contain the data from the SL LCHs with HARQ-enabled mode. The above- discussed framework supports an LCP procedure which is based, at least in part, on SL, which had be previously unsupported in the legacy Uu and PC5 procedures.

Several techniques have also been proposed for further developing LCP when selecting an MCR associated with a MAC TB. First, a TB could only contain data from one LCH or from the LCHs with the same MCR requirement. Alternatively, TBs could be generated without regard to the MCR but according to the normal LCP procedure, where the highest available MCR of the LCH multiplexed into the TB is ultimately selected, which may correspond with the current procedure agreed in the 3GPP radio access network (RAN) working groups.

In a further proposal, the SLRB configuration of a UE could include a range of MCRs which define various transmission ranges for SLRB mapping. As the first step, among all the SLRBs/LCHs that have data in the buffers to transmit, the SLRB/LCH with the highest priority level may be selected. Additionally, LCP may only multiplex logical channels having a similar range of MCRs in the associated SLRB configuration.

In certain embodiments, MAC multiplexing and TB generation may be performed transparently for MCR, and for a given destination, the highest corresponding MCR would be indicated to layer 1 (LI). With the above-mentioned proposals, the MCR may be a relevant parameter for SLRB in the LCP procedure.

After a SL TX UE is configured with a resource grant, either through a network- scheduled resource allocation mode or an autonomous-UE resource selection mode, the MAC layer at the SL TX UE may be notified of the amount of data that can be transmitted in the granted resource. Subsequently, the SL MAC layer may determine how to multiplex data from different SL LCHs based on the established LCP procedure transparently to MCR, and may deliver the generated MAC PDU to the physical layer (PHY).

In a SL groupcast scenario where HARQ feedback only includes a NACK being returned via the PSLCH, each SL LCH may carry data from the QoS flows with similar QoS requirements. Thus, the payload from the SL LCH may be configured with a range of parameters indicating to all receiving UE within the MCR that they are required to transmit NACKs only when unable to decode the physical sidelink shared channel (PSSCH). Multiplexing multiple SL LCHs with various MCR requirements may improve TX UE resource utilization compared with multiplexing the data from SL LCHs having an identical MCR. Lor example, when an assigned resource can accommodate more data than SL LCHs with the same MCR, the assigned resource may also be used to carry data from other SL LCHs, rather than wasting any unused resources. In addition, the SCI may only carry a single MCR via the PSCCH, which would leave open how the range parameter should be set in the SCI since multiple MCR requirements are each associated to a different SL LCH. The range parameter carried in the SCI may be set to a maximum MCR value observed among the multiplexed SL LCHs, ensuring that all relevant RX UEs provide relevant HARQ feedback.

However, such a technique may impair the spectral efficiency of SL data transfers in several ways. Lor example, as illustrated in LIG. 2, PSPCH power control may be performed to simplify MCR selection by open-loop power control being based on the path loss, or path attenuation, between the PSPCH TX UE and network node if PSPCH TX UE is within range. Specifically, the nominal power and alpha for PSPCH power control would be configured separately from the parameters used for PSCCH/PSSCH power control, which would not allow support of SL path loss-based PSPCH power control.

In the example illustrated by PIG. 2, the SL TX MAC layer multiplexes data from three different SL LCHs having MCR requirements of R1 < R2 < R3 (according to PIG. 1). When compared to the RXs located in close proximity to the SL TX, the RX(s) having the furthest distance from the SL TX (in PIG. 2, SL RX 3) may have a higher probability for data reception failure via PSSCH, while the remaining RXs (in PIG. 2, SL RXs 1, 2, and 4-6) may have successful data reception. Thus, if only NACKs are returned from the RXs to the TX (HARQ feedback option 1), SL RX 3 may send a NACK back to the SL TX upon failing to decode a transmission received from SL TX, which may trigger the SL TX to retransmit the same packet based on the current baseline scheme. This may result in two disadvantages, with the first disadvantage being that not all information needs to be retransmitted. For example, when a NACK from SL RX 3 is detected by the SL TX, the SL TX may retransmit the same data packet, as mentioned above by using the legacy mechanism. However, if that data packet only contains a small portion of the data from the SL LCH with an MCR value of R3, it would be inefficient to retransmit the entire data packet, since SL RX 3 is not required to successfully receive the data from the SL LCHs with MCR values of R1 and R2.

A second disadvantage arises by the power control not being optimized for the affected SL RX. As summarized above, open loop power control applied to the PSFCH may be based on the path loss between the PSFCH TX UE and network node. With the example of FIG. 2, SL RX 3 may not transmit NACK signals with enough power to be successfully received by the SL TX. Conversely, since PSFCH resources may be spatially reused by other links, if the PSFCH TX arbitrarily uses a high transmit power to ensure that feedback signals arrive at the SL TX with a reliable reception power, other PSFCH transmissions may experience significant interference as a result.

Furthermore, the SL TX would ideally consider MCR when determining the modulation and coding scheme (MCS). As range increases, the reliability of the TB should also be improved to satisfy any QoS parameters of the TB. However, if the maximum range is always selected without other considerations, the MCS with the lowest efficiency may always be selected regardless of whether the largest MCR has low QoS requirements or not.

Some embodiments described herein relate to multiplexing SL LCHs with different MCR values into the same TB, as shown in FIG. 1, where a TB is generated regardless of the MCR, and in accordance with the normal LCP procedure, the highest MCR among the MCRs of the multiplexed SL LCHs may be selected for being carried in the SCI. Specifically, various embodiments describe adapting the multiplexing of different SL LCHs with different MCR values, within the same TB for HARQ retransmission in a groupcast scenario where HARQ feedback option 1 is used. In addition, the adaptation may further trigger an adjustment on the LCP restriction procedure, which may apply for both the following initial transmission and retransmission.

Certain embodiments described herein may have various benefits and/or advantages to overcome the disadvantages described above. For example, some embodiments may reduce HARQ retransmissions, thereby saving limited radio resources. Thus, certain embodiments are directed to improvements in computer-related technology.

FIG. 3 illustrates an example of a signaling diagram showing communications between SL TX 330, SL RX 340, SL RX 350, and SL RX 360. SL TX 330, SL RX 340, SL RX 350, and SL RX 360 may be similar to UE 610, as illustrated in FIG. 6. In some embodiments, the behavior of SL RX 340 illustrated in FIG. 3 may correspond with SL RX 3 illustrated in FIG. 2.

At 301, SL TX 330 may multiplex, at the MAC layer, data from a plurality of SL LCHs into a single MAC PDU. In some embodiments, SL TX 330 may further provide an indication of the different MCRs of the multiplexed SL LCHs to a PHY of SL TX 330. In some embodiments, the LCP performed at the MAC layer may only multiplex the logical channels having MCR values within the configured delta-MCR-range into the same TB. Thus, all LCHs with MCRs within \MCR_selected +/- delta-MCR-range ] may be multiplexed into one TB, where MCR_selected may be the MCR of a selected LCH, e.g., the LCH with the highest priority level and having data to be transmitted. Thus, all LCHs with MCRs outside [MCR_selected +/- delta-MCR-range ] may be multiplexed into a separate TB. The value of delta-MCR-range may be configured by the network or pre- configured, and may change according to dynamics of the scenario, e.g., a group of faster cars may have a larger value of delta-MCR-range. After multiplexing, one or multiple of the different MCRs of the multiplexed SL LCHs may be indicated to the PHY of SL TX 330. At 303, the PHY of SL TX 330 may select at least one maximal MCR value from the plurality of MCRs of the different multiplexed SL LCHs, for example, as a parameter indicating ranges to be indicated in SCI. In some embodiments, the PHY may be configured multiple PSFCH resources/instances where one of the plurality of the configured PSFCH resources/instances may be used by each PSFCH TX (i.e., SL RX 340, SL RX 350, SL RX 360) to transmit a corresponding HARQ NACK signal. In some embodiments, the PSFCH resources/instances described above may also be configured by a network e.g., via dedicate signaling or broadcasted system information, or by pre configuration at a PSFCH TX and/or PSFCH RX. For example, SL TX 330 may not need to configure the PSFCH resources/instances at 303, as they will be configured by network or pre-configuration.

In various embodiments, the multiple PSFCH resources/instances may also be carried via SCI. For example, for multiple QoS flows/SL LCHs with different MCRs (Rl, R2, and R3) multiplexed into the same TB, three different PSFCH resources (e.g., in frequency, time, and/or code domain) may be configured for SL RX 340 (PSFCH TX) to send HARQ NACKs, where each of the resources implicitly corresponds to the distance range between SL TX 330 (PSFCH RX) and SL RX 340/350/360 (PSFCH TX). In some embodiments, if the PSFCH resources/instances are configured by network or pre-configuration, the multiple PSFCH resources/instances may not be carried via SCI, as the SL RXs may already be aware of these PSFCH resources/instances.

In a similar example, SL TX 330 (PSFCH RX) may also select and/or configure less than 3 PSFCH resources. As an illustration, if the difference between R1 and R2 is within a predetermined threshold, SL TX 330 (PSFCH RX) may configure two PSFCH resources: the first resource for the PSFCH TXs with a distance smaller than R2, and the second resource for the PSFCH TXs with a distance larger than R2 but smaller than R3.

In certain embodiments, SL TX 330 (PSFCH RX) may configure only one PSFCH resource/instance, but the PSFCH TXs may be either implicitly or explicitly configured/indicated to use a ranging sequence for the NACK signal, for example, a Zadoff-Chu sequence with zero-cyclic-shift. In this case, the SL TX may determine the distance from the PSFCH TX after receiving the feedback signal containing the ranging sequence, e.g., a Zadoff-Chu sequence with zero-cyclic-shift. In addition, a shifted version of the Zadoff-Chu sequence may be used, where the number of shifts may refer to a specific distance range between SL TX 330 (PSFCH RX) and SL RX 340/350/360 (PSFCH TX).

At 305, SL TX 330 (PSFCH RX) may have been configured with at least one table/policy, which may constrain the maximal SL transmit power as a function of the range parameter carried in the SCI, such as (range). As an example, the at least one table/policy may allow a higher maximal SL transmit power with a larger range value carried in the SCI. In addition, the same or different table(s)/policy(s) may be configured for PSCCH transmission and PSSCH transmission, respectively. Thus, an unnecessarily high transmit power may be avoided for a small range requirement, minimizing interference. Furthermore, the configuration of the at least one table/policy may be provided by a network entity, via UE-implementation, or pre-configured at a SL user equipment. In addition, the table/policy may also take account of other factors, such as CBR and packet priority. Thus, with these other factors, the table/policy may pose an additional constraint, where the transmit power may be a function of the range parameter. As a note, 301-305 may be performed in any order, or simultaneously.

At 307, SL TX 330 (PSFCH RX) may configure SL transmit power P_SL, for example, where where may indicate the maximal SL transmit power derived from the baseline power control scheme (e.g., as described in 3GPP TS 36.213), and may indicate the range constraint from 305. Thus, if is smaller than the baseline power control (e.g., when there is a small range value), the SL transmit power may be controlled, and its introduced interference power may be lower. At 309, SL TX 330 (PSFCH RX) may transmit at least one sidelink groupcast to at least one of SL RX 340, SL RX 350, and SL RX 360, with the transmit power derived at 307.

At 311 , after receiving the SCI and the SL data, any of the SL RXs may read the location of SL TX 330 from the SCI, and/or the carried range parameter from its received SCI, as well. In addition, any of the SL RXs may also determine its own location ( e.g . by using its GPS position) and calculate its distance, d, from SL TX 330. If d is less or equal to the range received from the SCI, but the SL RX fails in decoding data received from the PSSCH, the SL RXs may transmit a NACK signal to SL TX 330 (PSFCH RX) via PSFCH. In an example, if multiple PSFCH resources/instances are configured for one SL groupcast with different MCR configurations from different QoS flows/SL LCHs, as described at 303 above, SL RX 340 (PSFCH TX) may select at least one particular resource/instance to sending at least one HARQ NACK by considering its distance to the SL TX. In another example, if only one resource/instance is configured for one SL groupcast, as mentioned in the second example of 303, SL RX 340 (PSFCH TX) may decide to use or select a ranging sequence by considering the distance between SL TX 330 (PSFCH RX) and SL RX 340 (PSFCH TX). Furthermore, the ranging sequence may be configured for SL RX 340 (PSFCH TX) to send its HARQ NACK to SL TX 330 via the configured resource/instance.

At 313, based on the SL RSRP (i.e., denoted by ) derived from the SCI/data reception, SL RX 340 (PSFCH TX) may calculate the maximal SL pathloss value as Accordingly, SL RX 340 (PSFCH TX) may set its transmit power for PSFCH as where may represent the maximal SL transmit power (as defined in 3GPP TS 36.101), and may represent the minimal reception power for successfully detecting the feedback signal at SL TX 330 (PSFCH RX). In this way, the transmit power of SL RX 340 (PSFCH TX) may be properly adjusted by SL RX 340 (PSFCH TX) in order to achieve an improved probability of being detectable by SL TX 330 (PSFCH RX). In some embodiments, where and where represents the agreed baseline power control scheme by considering the path loss between SL RX 340 (PSFCH TX) and SL TX 330 (PSFCH RX), the proposed PSFCH transmit power may be lower than the baseline scheme, which may reduce the mutual interference power of the other PSFCH TXs using the same PSFCH resource ( e.g ., other PSFCH TXs served by other neighboring cells), improving the successful detection probability of the feedback signals at other SL TXs.

At 315, SL RX 340 (PSFCH TX) may transmit at least one NACK to SL TX 330 (PSFCH RX) by using the PSFCH resource/instance and/or the ranging sequence determined at 311 if SL RX 340 (PSFCH TX) does not receive the SL groupcast transmission correctly. Additionally, the transmit power derived at 313 may be used for transmitting the feedback. At 317, after SL TX 330 (PSFCH RX) receives the NACK feedback signal(s) from SL RX 340, SL TX 330 may determine its distance(s) to the PSFCH TX(s) (e.g., SL RX 340) based on at least one PSFCH resource/instance or ranging sequence from which NACK is received. In some embodiments, if multiple PSFCH resources/instances are configured for PSFCH, as mentioned at 303, the determination may be performed by checking if each PSFCH resource/instance contains at least one NACK feedback. In various embodiments, if a ranging sequence is used by SL RX 340 for PSFCH transmission (e.g., as mentioned in the second example at 303), SL TX 330 may decide the distance ranges of SL RX 340 by using the ranging sequence. For example, if a Zadoff- Chu sequence with a zero-cyclic-shift is used, SL TX 330 may determine the distance of SL RX 340 based on the number of cyclic shifts detected by performing peak correlation of the received feedback sequence with a zero-cyclic-shifted sequence.

At 319, based on the computed distances of the SL RX 340, SL TX 330 may adjust its HARQ retransmission accordingly. In a first example embodiment, if SL TX 330 receives HARQ NACKs from SL RXs of all concerned ranges, such as if the HARQ NACKs are received from different PSFCH TXs that locate within ranges of Rl, R2, and R3, normal HARQ retransmission may be performed, in order to fulfill the QoS requirements of the different multiplexed SL LCHs.

In a second example embodiment, if HARQ NACKs are received only from PSFCH TX(s) within a certain range, e.g., with a distance between R2 and R3 from FIG. 2, the HARQ retransmission may contain only the data from the SL LCH corresponding to R3, in which a more robust MCS may be used, since there is less data to transmit. The reason to contain only data from SL LCH with MCR of R3 is that SL RX 3 in FIG. 2 is not required to receive the data from SL LCHs with MCR values of R1 and R2, and the data from SL LCHs with MCR of R1 and R2 have been successfully received by the intended SL RXs within the corresponding MCRs (e.g., SL RXs 1, 2, 4, and 5 in FIG. 2). Therefore, instead of performing retransmission of the old TB containing data from SL LCHs corresponding to R1, R2, and R3, a more robust MCS may be applied to carry only the information required to be retransmitted (i.e., the data from SL LCH corresponding to R3) and, therefore, the proposed scheme may improve reliability for retransmission of the unacknowledged data.

In some embodiments, the HARQ process ID and the new data indicator (NDI) of the retransmission may be set as the same values of the previous/initial transmission. In addition, a new information element (IE) may be used in the SCI to indicate that the retransmission uses a newly-constructed TB. This newly-constructed TB may contain only part of the data from the previous/initial transmission (e.g., only the data from the SL LCH with an MCR value of R3). Based on the HARQ process ID, the NDI, and the new IE, SL RX 340-360 may know if they have successfully received this data part. This may improve RX UE behavior by preventing other SL RXs (i.e., RXs 1, 2, and 4-6 in FIG. 2) from decoding this TB in the retransmission and sending NACK feedback since they know they have already successfully received this data part.

In various embodiments, by receiving the HARQ process ID, the NDI, and the new IE, the SL RX that failed in the previous SL reception (i.e., RX UE 3 in FIG. 2) may be aware that this is a retransmission by reading the un-toggled NDI; this retransmission is not the retransmission of the old TB, and it is a new TB containing only part of the data from the old TB by reading the new IE; and this retransmission refers to a specific HARQ process by reading the HARQ process ID. Thus, the SL RX (i.e., RX UE 3 in FIG. 2) may flush its buffer for that particular HARQ process, and it will not use the buffered soft bits to decode the received new TB from the retransmission.

Additionally or alternatively, by receiving the HARQ process ID and the NDI, the SL RXs (i.e., RXs 1, 2, and 4-6 in FIG. 2) may know that they have successfully received this data, do not need to decode the data payload, and will not send NACK feedback irrespective of their instantaneous SL radio condition.

At 321, SL TX 330 may adapt the HARQ retransmission, which may result in a modification of the LCP procedure. For example, if SL TX 330 has experienced N consecutive retransmission events for the corresponding N initial transmissions based on its current LCP, as indicated in the second example at 319, and the value of N is larger or equal to a configured threshold, then SL TX 330 may modify its LCP restrictions so that the SL LCH with a specific MCR value (e.g., MCR of R3) is no longer multiplexed with the other SL LCHs (e.g., whose MCRs are R1 and R2) for the initial transmission.

In some embodiments, the modification of the LCP procedure at 321 may be valid for a certain configured period before falling back to the previous settings. Alternatively, it may also be valid until another event occurs. For example, if the SL channel condition (e.g., CBR) is improving, the modified LCP procedure may fall back to its previous settings, as the SL LCH with MCR of R3 may be better supported now, if it is multiplexed with the other SL LCHs (e.g., whose MCRs are R1 and R2).

FIG. 4 illustrates an example of a flow diagram of a method that may be performed by a SL TX, such as UE 610 illustrated in FIG. 6, according to certain embodiments. In an example, the SL TX may be configured by network and/or pre-configuration with multiple PSFCH resources in time-frequency-code domain corresponding with different MCRs. In certain embodiments, the code domain may correspond with a range sequence, as mentioned above. At 401, the SL TX may multiplex, at the MAC layer, data from a plurality of SL LCHs into a single MAC PDU. In some embodiments, the SL TX may further provide an indication of one or multiple MCR of the multiplexed SL LCHs to a PHY.

At 403, the SL TX may select at least one maximal MCR value from the plurality of SL LCHs, for example, as a parameter indicating ranges to be indicated in SCI. In some embodiments, the SL TX may configure multiple PSFCH resources/instances where one of the plurality of the configured PSFCH resources/instances may be used by each PSFCH TX to transmit a corresponding HARQ NACK signal.

In various embodiments, the multiple PSFCH resources/instances may also be carried/indicated via SCI. For example, for multiple QoS flows/SL LCHs with different MCRs ( R1 , R2, and R3) multiplexed into the same TB, three different PSFCH resources (in frequency, time, and/or code domain) may be configured for the PSFCH TXs to send HARQ NACKs, where each of the resources implicitly corresponds to one distance range between the SL TX and the PSFCH TX.

In a similar example, the SL TX may also select less than 3 PSFCH resources. As an illustration, if R1 and R2 are within a predetermined threshold, then the SL TX may configure two PSFCH resources: the first resource for the PSFCH TXs with a distance smaller than R1 or R2, and the second resource for the PSFCH TXs with a distance larger than R1 or R2 but smaller than R3.

In certain embodiments, the SL TX may configure only one PSFCH resource/instance, but the SL TX may either implicitly or explicitly indicate that the PSFCH TXs should use a ranging sequence for the NACK signal, for example, a Zadoff-Chu sequence with zero-cyclic-shift. In addition, the approach of using a ranging sequence for feedback signal may also be configured by the network or pre-configured at a PSFCH TX.

At 405, the SL TX may configure at least one table/policy at the UE, which may constrain the maximal SL transmit power as a function of the range parameter carried in the SCI, such as (range). As an example, the at least one table/policy may allow a higher maximal SL transmit power with a larger range value. Thus, an unnecessarily high transmit power may be avoided for a small range requirement, minimizing interference. In addition, as mentioned before, the table/policy for constraining the maximal SL transmit power may also take the priority of the transmitted packet and/or CBR into account. Furthermore, the configuration of the at least one table/policy may be provided by a network entity, via UE-implementation, or pre-configured at the SL TX. As a note, 401-405 may be performed in any order, or simultaneously.

At 407, the SL TX may configure SL transmit power P_SL, for example, where P ·’ where R may indicate the maximal SL transmit power derived from the baseline power control scheme ( e.g ., as described in 3GPP TS 36.213), and (range) may indicate the range constraint from 405. Thus, if (range) is smaller than the baseline power control (e.g., when there is a small range value), the SL transmit power may be controlled, and its introduced interference power is lower.

At 409, the SL TX may transmit at least one sidelink groupcast to at least one SL RX. At 411, the SL TX may receive at least one NACK from an SL RX. At 413, after the SL TX receives the NACK feedback signal(s) from the SL RX(s), the SL TX may determine its distance to the SL RX(s) sending the NACK. In some embodiments, if multiple PSFCH resources/instances are configured for PSFCH, as mentioned at 403, the determination may be performed by checking if each PSFCH resource/instance contains at least one NACK feedback. In various embodiments, if a ranging sequence is used by the PSFCH SL TX for PSFCH transmission (as mentioned in the second example at 403), the SL TX may decide the distance ranges of the SL RX by using the ranging sequence. For example, if a Zadoff-Chu sequence is used, the SL TX may determine the distance of the SL RX based on the number of cyclic shifts detected by performing peak correlation of the received feedback sequence with a zero-cyclic- shifted sequence.

At 415, based on the computed distances of the SL RX, the SL TX may adjust its HARQ retransmission accordingly. In some embodiments, if the SL TX receives HARQ NACKs from the SL RXs in all ranges, normal HARQ retransmission may be performed.

In certain embodiments, if HARQ NACKs are received only from PSFCH TX(s) within a certain range, e.g., with a distance between R2 and R3 from FIG. 2, the HARQ retransmission may contain only the data from the SL LCH corresponding to R3, in which a more robust MCS may be used, since there is less data to transmit. The reason to contain only data from SL LCH with MCR of R3 is that SL RX 3 in FIG. 2 is not required to receive the data from SL LCHs with MCR values of R1 and R2, and the data from SL LCHs with MCR of R1 and R2 have been successfully received by the intended SL RXs within the corresponding MCRs. Therefore, instead of performing retransmission of the old TB containing data from SL LCHs corresponding to Rl, R2, and R3, a more robust MCS can be applied to carry only the information required to be retransmitted (i.e., the data from SL LCH corresponding to R3) and, therefore, the proposed scheme may improve reliability for retransmission of the unacknowledged data.

In some embodiments, the HARQ process ID and the new data indicator (NDI) of the retransmission may be set as the same values of the previous/initial transmission. In addition, a new information element (IE) may be used in the SCI to indicate that the retransmission uses a newly-constructed TB. This newly-constmcted TB may contain only part of the data from the previous/initial transmission. Based on the HARQ process ID, the NDI, and the new IE, the SL RXs may know if they have successfully received this data part. This may improve RX UE behavior by preventing other SL RXs (i.e., RXs 1, 2, and 4-6 in FIG. 2) from decoding this TB of the retransmission and sending NACK feedback since they know they have already successfully received this data part.

In various embodiments, by receiving the HARQ process ID, the NDI, and the new IE, the SL RX that failed in the previous SL reception (i.e., RX UE 3 in FIG. 2) will be aware that this is a retransmission by reading the un-toggled NDI; this retransmission is not the retransmission of the old TB, and it is a new TB containing only part of the data from the old TB by reading the new IE; and this retransmission refers to a specific HARQ process by reading the HARQ process ID. Thus, the SL RX flushes its buffer for that particular HARQ process, and it will not use the buffered soft bits to decode the received new TB.

Additionally or alternatively, by receiving the HARQ process ID and the NDI, the SL RXs (i.e., RXs 1, 2, and 4-6 in FIG. 2) know that they have successfully received this data, and they will not send NACK feedback irrespective of their instantaneous SL radio condition.

At 417, the SL TX may adapt of the HARQ retransmission, which may result in a modification of the LCP procedure. For example, if the SL TX has experienced N consecutive retransmission events for the corresponding N initial transmissions based on its current LCP, as indicated in the second example at 415, and the value of N is larger or equal to a configured threshold, then SL TX may modify its LCP restrictions so that the SL LCH with a specific MCR value ( e.g ., MCR of R3) is no longer multiplexed with the other SL LCHs (e.g., whose MCRs are R1 and R2).

In some embodiments, the modification of the LCP procedure from 417 may be valid for a certain configured period before falling back to the previous settings. Alternatively, it may also be valid until another event occurs. For example, if the SL channel condition (e.g., CBR) is improving, the modified LCP procedure may fall back to its previous settings, as the SL LCH with MCR of R3 may be better supported now, if it is multiplexed with the other SL LCHs.

FIG. 5 illustrates an example of a flow diagram of a method that may be performed by a SL RX, such as UE 610 illustrated in FIG. 6, according to certain embodiments. In an example, the SL RX may be configured by network and/or pre-configuration with multiple PSFCH resources in time-frequency-code domain corresponding with different MCRs. In certain embodiments, the code domain may correspond with a range sequence, as mentioned above. At 501, the SL RX may receive at least one sidelink groupcast from a SL TX, which may be similar to UE 610 illustrated in FIG. 6, including at least one transport block.

In various embodiments, multiple PSFCH resources/instances may also be received or configured via SCI. For example, for multiple QoS flows/SL LCHs with different MCRs ( R1 , R2, and R3) multiplexed into the same TB, three different PSFCH resources (e.g., in frequency, time, and/or code domain) may be configured for the SL RX to send HARQ NACKs, where each of the resources implicitly corresponds to the distance range between the SL TX 330 (PSFCH RX) and SL RX (PSFCH TX). Alternatively, the configuration of the mentioned multiple PSFCH resources/instances may also be configured either by network, e.g., via dedicate signalling or broadcasted system information, or by pre configuration.

In a similar example, if the difference between R1 and R2 is within a predetermined threshold, the SL TX (PSFCH RX) may receive two PSFCH resources: the first resource for the PSFCH TXs with a distance smaller than R2, and the second resource for the PSFCH TXs with a distance larger than R2 but smaller than R3.

At 503, after receiving the SCI and the SL data, the SL RX may read the location of the SL TX, and/or the carried range parameter from its received SCI. In addition, the SL RX may also determine its own location and distance, d, from the SL TX. If d is less than the required range, but the SL RX fails in decoding data received from the PSSCH, the SL RX may transmit a NACK signal to the SL TX via PSFCH. In an example, if multiple PSFCH resources/instances are configured for one SL groupcast with different MCR configurations from different QoS flows/SL LCHs, as described at 303 above, the PSFCH SL TX may select at least one particular resource/instance to sending at least one HARQ NACK by considering its distance to the SL TX. In another example, if only one PSFCH resource/instance is configured for one SL groupcast, as mentioned in the second example of 303, the SL RX may select a ranging sequence by considering the distance between the SL TX and the SL RX. Furthermore, the ranging sequence may be configured for the PSFCH TX to send its HARQ NACK to the SL TX via the configured resource/instance.

At 505, based on the SL RSRP (i.e., denoted by ) derived from the SCI/data reception, the SL RX may calculate the maximal SL pathloss value as Accordingly, the PSFCH TX may set its transmit power for may represent the maximal SL transmit power ( e.g ., as defined in 3GPP TS 36.101), and may represent the minimal reception power for successfully detecting the feedback signal at the SL TX. In this way, the transmit power of the PSFCH TX may be properly adjusted in order to achieve an improved probability of being detectable by the SL TX. Additionally, the SL RX may transmit the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of at least one configured resource or ranging sequence. In some embodiments, where and where represents the agreed baseline power control scheme by considering the path loss between PSFCH TX UE and network entity, the proposed PSFCH transmit power may be lower than the baseline scheme, which may reduce the mutual interference power to the other PSFCH TXs using the same PSFCH resource (e.g., other PSFCH TXs served by other neighboring cells), improving the successful detection probability of the feedback signals at other SL TXs. At 507, the SL RX may transmit at least one NACK to the SL TX by using the determined PSFCH resource/instance/sequence and the derived transmit power.

At 509, at least one adapted retransmission may be received from the SL TX, for example, at least one TB may be received including all or only part of the previously received TB. While the proposed techniques described herein are illustrated with sidelink groupcasts/multicasts as examples, the proposed techniques may also be applied for groupcast/multicast communications via a Uu interface. For example, the SL TX in the above examples may be replaced by a network node, such as an eNB or gNB, while SL RXs in the above examples of the multicast/groupcast communication may be similar to a group of UEs in a specific area.

Furthermore, the proposed techniques described herein may not only be applicable for HARQ feedback option 1 (i.e., NACKs are only returned via PSFCH to SL Tx), but may also be applicable for HARQ feedback option 2 (i.e., each intended SL RX transmits its feedback, either ACK or NACK, to the SL TX with a dedicate PSFCH resource). For example, in HARQ feedback option 2, the upper layers ( e.g ., application layer, V2X layer, and/or RRC layer) at the SL TX may indicate to the lower layers (e.g., MAC and/or PHY) the distance between each intended SL RX and the SL TX, or the set of the intended SL RXs inside a considered range. Thus, upon the reception of the HARQ feedback signals, the SL TX may be able to derive the corresponding distance range(s), where the previous groupcast/multicast transmission failed. As a result, the SL TX may adjust its retransmission procedure (e.g., carrying only the unacknowledged data/SL LCH) and/or the LCP restriction by using the proposed techniques. FIG. 6 illustrates an example of a system according to certain embodiments. In one embodiment, a system may include multiple devices, such as, for example, UE 610 and NE 620.

UE 610 may include one or more of a mobile device, such as a mobile phone, smart phone, personal digital assistant (PDA), tablet, or portable media player, digital camera, pocket video camera, video game console, navigation unit, such as a global positioning system (GPS) device, desktop or laptop computer, single-location device, such as a sensor or smart meter, or any combination thereof.

NE 620 may be one or more of a base station, such as an evolved node B (eNB) or next generation node B (gNB), a next generation radio access network (NG RAN), a serving gateway, a server, and/or any other access node or combination thereof.

One or more of these devices may include at least one processor, respectively indicated as 611 and 621. At least one memory may be provided in one or more of devices indicated at 612 and 622. The memory may be fixed or removable. The memory may include computer program instructions or computer code contained therein. Processors 611 and 621 and memory 612 and 622 or a subset thereof, may be configured to provide means corresponding to the various blocks of FIGS. 3-5. Although not shown, the devices may also include positioning hardware, such as global positioning system (GPS) or micro electrical mechanical system (MEMS) hardware, which may be used to determine a location of the device. Other sensors are also permitted and may be included to determine location, elevation, orientation, and so forth, such as barometers, compasses, and the like.

As shown in FIG. 6, transceivers 613 and 623 may be provided, and one or more devices may also include at least one antenna, respectively illustrated as 614 and 624. The device may have many antennas, such as an array of antennas configured for multiple input multiple output (MIMO) communications, or multiple antennas for multiple radio access technologies. Other configurations of these devices, for example, may be provided. Transceivers 613 and 623 may be a transmitter, a receiver, or both a transmitter and a receiver, or a unit or device that may be configured both for transmission and reception.

Processors 611 and 621 may be embodied by any computational or data processing device, such as a central processing unit (CPU), application specific integrated circuit (ASIC), or comparable device. The processors may be implemented as a single controller, or a plurality of controllers or processors.

Memory 612 and 622 may independently be any suitable storage device, such as a non- transitory computer-readable medium. A hard disk drive (HDD), random access memory (RAM), flash memory, or other suitable memory may be used. The memories may be combined on a single integrated circuit as the processor, or may be separate from the one or more processors. Furthermore, the computer program instructions stored in the memory and which may be processed by the processors may be any suitable form of computer program code, for example, a compiled or interpreted computer program written in any suitable programming language. Memory may be removable or non-removable.

The memory and the computer program instructions may be configured, with the processor for the particular device, to cause a hardware apparatus such as user equipment to perform any of the processes described below (see, for example, FIGS. 3- 5). Therefore, in certain embodiments, a non-transitory computer-readable medium may be encoded with computer instructions that, when executed in hardware, perform a process such as one of the processes described herein. Alternatively, certain embodiments may be performed entirely in hardware.

In certain embodiments, an apparatus may include circuitry configured to perform any of the processes or functions illustrated in FIGS. 3-5. For example, circuitry may be hardware-only circuit implementations, such as analog and/or digital circuitry. In another example, circuitry may be a combination of hardware circuits and software, such as a combination of analog and/or digital hardware circuit(s) with software or firmware, and/or any portions of hardware processor(s) with software (including digital signal processor(s)), software, and at least one memory that work together to cause an apparatus to perform various processes or functions. In yet another example, circuitry may be hardware circuit(s) and or processor(s), such as a microprocessor(s) or a portion of a microprocessor(s), that include software, such as firmware for operation. Software in circuitry may not be present when it is not needed for the operation of the hardware.

FIG. 7 illustrates an example of a 5G network and system architecture according to certain embodiments. Shown are multiple network functions that may be implemented as software operating as part of a network device or dedicated hardware, as a network device itself or dedicated hardware, or as a virtual function operating as a network device or dedicated hardware. The NE and UE illustrated in FIG. 7 may be similar to UE 610 and NE 620, respectively. The UPF may provide services such as intra-RAT and inter-RAT mobility, routing and forwarding of data packets, inspection of packets, user plane QoS processing, buffering of downlink packets, and/or triggering of downlink data notifications. The AF may primarily interface with the core network to facilitate application usage of traffic routing and interact with the policy framework.

The features, structures, or characteristics of example embodiments described throughout this specification may be combined in any suitable manner in one or more example embodiments. For example, the usage of the phrases “certain embodiments,” “some embodiments,” or other similar language, throughout this specification refers to the fact that a particular feature, stmcture, or characteristic described in connection with an embodiment may be included in at least one embodiment. Thus, appearances of the phrases “in certain embodiments,” “in some embodiments,” “in other embodiments,” or other similar language, throughout this specification do not necessarily all refer to the same group of embodiments, and the described features, structures, or characteristics may be combined in any suitable manner in one or more example embodiments. Additionally, if desired, the different functions or procedures discussed below may be performed in a different order and/or concurrently with each other. Furthermore, if desired, one or more of the described functions or procedures maybe optional or maybe combined. As such, the following description should be considered as illustrative of the principles and teachings of certain example embodiments, and not in limitation thereof.

It will be readily understood that the components of certain example embodiments, as generally described and illustrated in the figures herein, may be arranged and designed in a wide variety of different configurations. Thus, the following detailed description of some example embodiments of systems, methods, apparatuses, and computer program products for multiplexing of sidelink logical channels is not intended to limit the scope of certain embodiments, but is instead representative of selected example embodiments.

One having ordinary skill in the art will readily understand that the example embodiments as discussed above may be practiced with procedures in a different order, and/or with hardware elements in configurations which are different than those which are disclosed. Therefore, although some embodiments have been described based upon these example embodiments, it would be apparent to those of skill in the art that certain modifications, variations, and alternative constructions would be apparent, while remaining within the spirit and scope of example embodiments.

Partial Glossary

3GPP Third Generation Partnership Project

5G Fifth Generation

ACK Acknowledgement

ASIC Application Specific Integrated Circuit

BS Base Station

CBR Channel Busy Ratio

CPU Central Processing Unit

DL Downlink eMBB Enhanced Mobile Broadband eNB Evolved Node B

EPS Evolved Packet System

E-UTRAN Evolved Universal Mobile Telecommunications System Terrestrial

Radio Access Network gNB Next Generation Node B

GPS Global Positioning System

HARQ Hybrid Automatic Repeat Request

HDD Hard Disk Drive IEEE Institute of Electrical and Electronics Engineers

IoT Internet of Things

LI Layer 1

LCH Logical Channel LCP Logical Channel Prioritization LTE Long-Term Evolution

LTE-V2X Long-Term Evolution Vehicle-to-Everything

M2M Machine -to-Machine

MAC Medium Access Control

MCR Maximum Communication Range MCS Modulation and Coding Scheme

MEMS Micro Electrical Mechanical System MIMO Multiple Input Multiple Output MME Mobility Management Entity mMTC massive Machine Type Communication NACK N on- Acknowledgement NAS Non-Access Stratum NDI New Data Indicator NE Network Entity NG Next Generation NG-RAN Next Generation Radio Access Network NR New Radio NR-U New Radio Unlicensed NR-V2X New Radio Vehicle -to-Everything PDA Personal Digital Assistance PDU Protocol Data Unit PSCCH Physical Sidelink Control Channel PSFCH Physical Sidelink Feedback Channel PSSCH Physical Sidelink Shared Channel QoS Quality of Service RAM Random Access Memory RAN Radio Access Network RRC Radio Resource Control RX Receiver SA Service and System Aspects Working Group SCI Sidelink Control Information SL Sidelink

SLRB Sidelink Radio Bearer

TB Transport Block

TS Technical Specification TX Transmission UE User Equipment UL Uplink

UMTS Universal Mobile Telecommunications Service URLLC Ultra-Reliable and Low-Latency Communication UTRAN Universal Mobile Telecommunications Service Terrestrial Radio

Access Network

WLAN Wireless Local Area Network

Claims

CLAIMS:

1. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: receive (501) at least one sidelink groupcast from at least one side link transmitter; determine (503) a distance to the at least one sidelink transmitter; determine (505) one or more of at least one configured resource or at least one ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter; and transmit (507) the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of the configured resource and ranging sequence.

2. The apparatus of claim 1 , wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: receive (509) at least one retransmission from the at least one sidelink transmitter, wherein at least one of a new information element, new data indication, and sidelink hybrid automatic repeat request process identifier carried in one sidelink control information is configured to determine if the received retransmission associated with the sidelink control information corresponds to at least one previous reception and comprises a newly-constructed transport block.

3. The apparatus of any preceding claim, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: calculate at least one maximal sidelink path loss value configured to set the transmit power for transmitting the at least one sidelink feedback.

4. The apparatus of any preceding claim, wherein determining the distance to the at least one sidelink transmitter is based on at least one location of the at least one sidelink transmitter received from the sidelink control information.

5. The apparatus of any preceding claim, wherein the one or more of the at least one configured resource, at least one configured instance, and the at least one configured ranging sequence are configured to cause the apparatus to select transmitting sidelink feedback based on the determined distance to the at least one sidelink transmitter.

6. The apparatus of any preceding claim, wherein the one or more of at least one configured resource, at least one configured instance, and at least one configured ranging sequence are configured to cause the apparatus to select at least one non acknowledgement for transmitting based on the distance to the at least one sidelink transmitter.

7. An apparatus, comprising: at least one processor; and at least one memory including computer program code, wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the apparatus at least to: transmit (409) at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different maximum communication ranges; receive (411) at least one sidelink feedback from the at least one sidelink receiver; determine (413) at least one distance range to the at least one sidelink receiver associated with the at least one sidelink feedback; and adjust (415) at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

8. The apparatus of claim 7, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: receive (403) at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different maximum communication ranges.

9. The apparatus of any of claims 7 or 8, wherein the adjustment of the at least one retransmission further comprises the transmission of at least one new information element in the sidelink control information, wherein the new information element is configured to indicate the transport block associated with the sidelink control information corresponding to at least one previous transmission and comprises a newly- constructed transport block.

10. The apparatus of any of claims 7-9, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: configure at least one policy configured to constrain at least one maximal sidelink transmit power as a function of a range parameter associated with the sidelink control information.

11. The apparatus of any of claims 7-10, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: configure (405) at least one sidelink transmit power.

12. The apparatus of any of claims 7-11, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: after receiving at least one sidelink feedback signal from the at least one sidelink receiver, determine at least one distance range to the at least one sidelink receiver associated with the sidelink feedback.

13. The apparatus of any of claims 7-12, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: adjust at least one retransmission based on the computed at least one distance range to the at least one sidelink receiver that sent the sidelink feedback, wherein the retransmitted packet comprises at least a part of the data from a previous transmission not successfully received by the sidelink receivers and is successfully received in the computed at least one distance range.

14. The apparatus of any of claims 7-13, wherein adaptation of at least one logical channel prioritization is triggered if a configured number of adaptive retransmissions occur consecutively.

15. The apparatus of any of claims 7-14, wherein at least one logical channel prioritization restriction is configured to revert to at least one previous restriction.

16. The apparatus of any of claims 7-15, wherein at least one fallback to the at least one previous restriction is associated with one or more of a configured number of transmissions and at least one system condition change.

17. The apparatus of any of claims 7-16, wherein the at least one memory and the computer program code are further configured to, with the at least one processor, cause the apparatus at least to: multiplex one or more logical channels based upon the maximum communication range of the selected logical channel with a highest priority level and a configured offset value.

18. The apparatus of any of claims 7-17, wherein the retransmission comprises only part of the data from a previous transmission.

19. A method, comprising : receiving (501) at least one sidelink groupcast from at least one sidelink transmitter; determining (503) a distance to the at least one sidelink transmitter; determining (505) one or more of at least one configured resource or at least one ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter; and transmitting (507) the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of the configured resource and ranging sequence.

20. A method, comprising: transmitting (409) at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different maximum communication ranges; receiving (411) at least one sidelink feedback from the at least one sidelink receiver; determining (413) at least one distance range to the at least one sidelink receiver associated with the at least one sidelink feedback; and adjusting (415) at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

21. An apparatus, comprising: means for receiving (501) at least one sidelink groupcast from at least one sidelink transmitter; means for determining (503) a distance to the at least one sidelink transmitter; means for determining (505) one or more of at least one configured resource or at least one ranging sequence to transmit at least one sidelink feedback based upon the determined distance to the at least one sidelink transmitter; and means for transmitting (507) the at least one sidelink feedback to the at least one sidelink transmitter based upon the determined one or more of the configured resource and ranging sequence.

22. An apparatus, comprising: means for transmitting (409) at least one sidelink groupcast to at least one sidelink receiver, wherein the one sidelink groupcast transmission comprises using at least one configuration of sidelink feedback channel resources or ranging sequences corresponding to a plurality of different maximum communication ranges; means for receiving (411) at least one sidelink feedback from the at least one sidelink receiver; means for determining (413) at least one distance range to the at least one sidelink receiver associated with the at least one sidelink feedback; and means for adjusting (415) at least one retransmission based on the determined at least one distance range to the sidelink receiver associated with sidelink feedback.

23. A non- transitory computer-readable medium comprising program instmctions stored thereon for performing the method according to any of claims 19- 20.

24. An apparatus comprising circuitry configured to cause the apparatus to perform the method according to any of claims 19-20.

25. A computer program product encoded with instmctions for performing the method according to any of claims 19-20.