Patent Application
20250168867
The present disclosure relates to direct communication between radio terminals (device-to-device (D2D) communication), in particular to the use of multiple carriers in direct communication.
The mode in which a radio terminal communicates directly with another radio terminal, without the need for an infrastructure network such as a base station, is commonly referred to as device-to-device
(D2D) communication. D2D communications can be integrated with or assisted by a cellular network. Proximity-based services (ProSe), specified in the Third Generation Partnership Project (3GPP (registered trademark)) Release 12 and beyond, provide a system architecture for D2D communications assisted by a cellular network.
In addition, cellular Vehicle-to-Everything (V2X) services, specified in 3GPP Release 14 and beyond, refer to ProSe and use D2D communications between radio terminals. D2D communications assisted by a cellular network can also be used for other applications and services (e.g., public safety applications) in addition to V2X services.
The interface between 3GPP radio terminals (i.e., User Equipments (UEs)) used in the control and user planes for D2D communication is called the PC5 interface (or reference point). D2D communication over the PC5 interface is referred to as sidelink communication. The PC5 interface can be based on the Evolved Universal Terrestrial Radio Access (E-UTRA) sidelink capability and can also be based on the 5G New Radio (NR) sidelink capability. D2D (or sidelink) communication over the E-UTRA-PC5 (or Long Term Evolution (LTE)-based PC5) interface is connectionless, i.e., broadcast mode at the Access Stratum (AS) layer. In contrast, sidelink communication over the NR PC5 interface supports unicast mode, groupcast mode, and broadcast mode at the AS layer.
Sidelink communication over the E-UTRA-PC5 interface is referred to, for example, as LTE sidelink communication. Sidelink communication over the NR PC5 interface is referred to, for example, as NR sidelink communication. The 3GPP specification specifies architectural enhancements to facilitate vehicular communications for cellular V2X services (see, for example, Non-Patent Literature 1, 2, and 3). LTE sidelink and NR sidelink communications play an important role in enabling cellular V2X communications. V2X communication over the E-UTRA-PC5 interface, or AS functionality using E-UTRA technology including LTE sidelink communication to enable V2X communication between UEs is referred to as V2X sidelink communication or LTE V2X sidelink communication. V2X communication over the NR PC5 interface, or AS functionality using NR technology including NR sidelink communication to enable V2X communication between UEs is referred to as NR V2X sidelink communication or simply NR sidelink communication.
3GPP Release 15 supports carrier aggregation (CA) and multicarrier operation for LTE sidelink communications (see Non-Patent Literature 1 and 4). For 3GPP Release 18, the 3GPP plans to discuss Sidelink Evolution. This includes support for carrier aggregation for NR sidelink communications and support for sidelink over unlicensed spectrum (see Non-Patent Literature 5).
Patent Literature 1, 2, and 3 disclose sidelink (SL) carrier aggregation, i.e., carrier aggregation for SL communications, and in particular, signaling between UEs and signaling between a UE and a radio access network (e.g., base station) for SL carrier aggregation.
Patent Literature 1 describes that a UE may send to a peer UE an SL carrier aggregation configuration related to the addition, release or modification of a secondary SL (see, for example, FIGS. 3, 4, 5, and 10 in Patent Literature 1). The SL carrier aggregation configuration may be related to the addition, release, or modification of a secondary SL and may include a set of carrier frequencies and deactivation timer information. The SL carrier aggregation configuration may include a reception (Rx) or transmission (Tx) indicator, a primary or secondary SL indicator, a type of carrier aggregation (e.g., data replication or data split), a V2X service type, a synchronization type, a primary SL index (or carrier index), a secondary SL index (or carrier index), SL Tx or Rx resource allocation information, and so on.
Patent Literature 1 describes that after PC5 carrier aggregation is configured, the UE may notify this to the base station (see, for example, FIG. 6 in Patent Literature 1). The notification message may include at least one of a set of carrier frequency information, a deactivation timer, and a peer UE identifier. For each SL component carrier, the notification message may further include a reception (Rx) or transmission (Tx) indicator, a primary or secondary SL indicator, a type of carrier aggregation (e.g., data replication or data split), a V2X service type, a synchronization type, a primary SL index (or carrier index), a secondary SL index (or carrier index), SL Tx or Rx resource allocation information, and so on.
Patent Literature 1 states that a UE may send a request for SL carrier aggregation configuration between the UE and a peer UE to the base station, and the base station may generate the configuration and provide it to the UE (see, for example, FIG. 9 in Patent Literature 1). Patent Literature 1 also states that the request message is optional and that the base station may provide the SL carrier aggregation configuration to the UE regardless of receipt of the request message from the UE.
Patent Literature 1 describes that UEs may exchange information about their respective SL carrier aggregation capability directly with each other prior to configuring SL carrier aggregation (see, for example, FIG. 13 in Patent Literature 1). The SL carrier aggregation capability includes one or both of the following: SL band combination information, SL and Uu band combination information. Uu is the air interface between the UE and the base station. The band combination information sent by the UE indicates the list of carriers and the bandwidth of each carrier on which the UE can operate simultaneously. The UE may indicate whether it supports both transmit (Tx) and receive (Rx) or only one of transmit (Tx) and receive (Rx) on each carrier.
Patent Literature 2 describes that a UE receives from a wireless wide area network (WAN) a Radio Resource Control (RRC) signal (e.g., RRC Connection Reconfiguration message) containing a command to add or release a component carrier of a V2X carrier aggregation (see, for example, FIGS. 2 and 3 of Patent Literature 2).
Patent Literature 3 describes that a first wireless device receives a sidelink message containing sidelink capability information of a second wireless device from the second wireless device via a sidelink channel and transmits an uplink message containing the sidelink capability information to the base station (see, e.g., FIG. 25 in Patent Literature 3). The sidelink capability information of the second wireless device may indicate whether the second wireless device supports sidelink multiple carrier operation (e.g., sidelink carrier aggregation, sidelink multiple carriers, sidelink multi-carrier), a supported/operating sidelink (e.g., LTE, 5G, etc.), an available band, whether the second wireless device supports an unlicensed band (or unlicensed spectrum), and the like. The base station may determine configuration parameters for sidelink communication between the first and second wireless devices based on the sidelink capability information of the second wireless device, and send those configuration parameters to the first wireless device. The configuration parameters may be sent in an RRC message, a Medium Access Control (MAC) Control Element (CE), or a Physical Downlink Control Channel (PDCCH) transmission (e.g., Downlink Control Information (DCI)).
Patent Literature 3 describes that the first wireless device receives a sidelink message containing band combination information of the second wireless device from the second wireless device via a sidelink channel, and transmits an uplink message (e.g., an RRC message) containing the band combination information to the base station (see, for example, FIG. 26 of Patent Literature 3). The band combination information of the second wireless device may indicate one or more bands that are allowed to be used simultaneously for sidelink communication at the second wireless device. The band combination information of the second wireless device may indicate whether the second wireless device supports multiple sidelink carriers (e.g., multicarrier operation, sidelink carrier aggregation). For example, the base station may determine or assign resources corresponding to multiple carriers if the band combination information indicates that the second wireless device supports multiple sidelink carriers. The base station transmits configuration parameters for sidelink communication between the first and second wireless devices to the first wireless device. The configuration parameters may indicate a sidelink resource assignment. More specifically, the sidelink resource assignment may indicate a first sidelink radio resource in the first carrier and a second sidelink radio resource in the second carrier. The first wireless device may transmit a first transport block to the second wireless device on the first sidelink radio resource and a second transport block to the second wireless device on the second sidelink radio resource.
The inventor has studied carrier aggregation for D2D communication, including NR sidelink communication, and found various problems. Carrier aggregation on a D2D interface or sidelink interface (e.g., PC5 interface) between radio terminals can also be referred to as multicarrier operation.
One of these problems relates to UEs with limited transmission capabilities. In sidelink carrier aggregation, UEs are not necessarily able to transmit on multiple sidelink carriers simultaneously. In other words, UEs may not support transmission on multiple sidelink carriers in the same time slot. A UE with such limited transmission capability may be referred to as a limited Tx capability UE. When a UE can receive on multiple reception sidelink component carriers simultaneously, but cannot transmit on multiple transmission sidelink component carriers simultaneously, it is not clear how the UE transmits a hybrid automatic repeat request (HARQ) feedback on a Physical Sidelink Feedback Channel (PSFCH). Specifically, such a UE may receive multiple Physical Sidelink Shared Channels (PSSCHs) on multiple reception sidelink component carriers. In this case, it is not clear how this UE transmits multiple HARQ feedbacks regarding the PSSCH receptions on the multiple reception component carriers.
One of the objects that the example embodiments disclosed herein seek to achieve is to provide apparatuses, methods, and programs that contribute to solving at least one of a plurality of problems, including the above-described problems related to carrier aggregation on a D2D interface between radio terminals. It should be noted that this object is only one of the objects to be achieved by the example embodiments disclosed herein. Other objects or problems and novel features will become apparent from the following description and the accompanying drawings.
In a first aspect, a radio terminal includes at least one radio transceiver and at least one processor coupled to the at least one radio transceiver. The at least one processor is configured to receive a first sidelink transmission from a peer radio terminal on a first sidelink carrier and receive a second sidelink transmission from the peer radio terminal on a second sidelink carrier. The at least one processor is configured to transmit a first HARQ feedback for the first sidelink transmission and a second HARQ feedback for the second sidelink transmission using a plurality of PSFCH resources within an identical time slot in the first sidelink carrier.
In a second aspect, a method performed by a radio terminal includes the steps of:
In a third aspect, a radio terminal includes at least one radio transceiver and at least one processor coupled to the at least one radio transceiver. The at least one processor is configured to receive a first sidelink transmission from a peer radio terminal on a first sidelink carrier and receive a second sidelink transmission from the peer radio terminal on a second sidelink carrier. The at least one processor is configured to, if a first PSFCH transmission on the first sidelink carrier for HARQ feedback for the first sidelink transmission overlaps in time with a second PSFCH transmission on the second sidelink carrier for HARQ feedback for the second sidelink transmission, delay the second PSFCH transmission on the second sidelink carrier to a next or subsequent PSFCH transmission occasion.
In a fourth aspect, a method performed by a radio terminal includes the steps of:
In a fifth aspect, a radio terminal includes at least one radio transceiver and at least one processor coupled to the at least one radio transceiver. The at least one processor is configured to receive a first sidelink transmission from a peer radio terminal on a first sidelink carrier and receive a second sidelink transmission from the peer radio terminal on a second sidelink carrier. The at least one processor is configured to, if a first PSFCH transmission on the first sidelink carrier for HARQ feedback for the first sidelink transmission overlaps in time with a second PSFCH transmission on the second sidelink carrier for HARQ feedback for the second sidelink transmission, select whether to perform the first PSFCH transmission or the second PSFCH transmission.
In a sixth aspect, a method performed by a radio terminal includes the steps of:
In a seventh aspect, a program includes a set of instructions (software codes) that, when loaded into a computer, cause the computer to perform the method according to the second, fourth, or sixth aspect described above.
According to the aspects described above, it is possible to provide apparatuses, methods and programs that contribute to solving at least one of a plurality of problems related to carrier aggregation on a D2D interface between radio terminals.
Specific example embodiments will be described hereinafter in detail with reference to the drawings. The same or corresponding elements are denoted by the same symbols throughout the drawings, and duplicated explanations are omitted as necessary for the sake of clarity.
Each of the example embodiments described below may be used individually, or two or more of the example embodiments may be appropriately combined with one another. These example embodiments include novel features different from each other. Accordingly, these example embodiments contribute to attaining objects or solving problems different from one another and contribute to obtaining advantages different from one another.
The example embodiments presented below are primarily described for the 3GPP 5th generation mobile communication system (5G system). However, these example embodiments can be applied to other radio communication systems that support D2D communication technology similar to 3GPP NR sidelink communication.
As used in this specification, “if” can be interpreted to mean “when”, “at or around the time”, “after”, “upon”, “in response to determining”, “in accordance with a determination”, or “in response to detecting”, depending on the context. These expressions can be interpreted to mean the same thing, depending on the context.
First, the configuration and operation of a plurality of network elements common to a plurality of example embodiments are described.
A radio access network (RAN) node (e.g., gNB) 2 manages a cell 21 and is capable of performing cellular communications (101 and 102) with a plurality of radio terminals (UEs) 1, including UEs 1A and 1B, using a cellular communication technology (i.e., NR radio access network). The cellular communication 101 uses an air interface (e.g., Uu interface) between the RAN node 2 and the UE 1A. Similarly, the cellular communication 102 uses an air interface (e.g., Uu interface) between the RAN node 2 and the UE 1B. The example in
Each of the UEs 1A and 1B has at least one radio transceiver and is configured to perform cellular communication (101 or 102) with the RAN node 2 and to perform D2D communication (i.e., sidelink communication) on a direct inter-UE interface (i.e., NR PC5 interface or NR sidelink) 103. The sidelink communication includes unicast mode communication (sidelink unicast) and may further include one or both of groupcast mode communication and broadcast mode communication.
The interface between 3GPP radio terminals (i.e., UEs) used in the control and user planes for D2D communication is called the PC5 interface (or reference point). D2D communication over the PC5 interface is referred to as sidelink communication. The PC5 interface can be based on the E-UTRA sidelink capability and can also be based on the 5G NR sidelink capability. D2D (or sidelink) communication over the E-UTRA-PC5 (or LTE-based PC5) interface is connectionless, i.e., broadcast mode at the AS layer. In contrast, sidelink communication over the NR PC5 interface supports unicast mode, groupcast mode, and broadcast mode at the AS layer.
In some implementations, the sidelink communication between the UEs 1A and 1B may be used for cellular V2X services and V2X communication. In other words, the UEs 1A and 1B and the RAN node 2 shown in
In the following description, when describing matters common to multiple UEs, including the UEs 1A and 1B, it will be referred to simply as UE 1 with the reference sign 1.
The V1 reference point is a reference point between a V2X application (e.g., V2X application 11A or V2X application 11B) in a UE 1 (e.g., UE 1A or UE 1B) and a V2X application in a V2X application server 61. The V2X application server 61 is located in a data network (DN) 50.
The V5 reference point is a reference point between V2X applications of two UEs 1 (e.g., UE 1A and UE 1B). The PC5 reference point is a reference point between UEs (e.g., UE 1A and UE 1B) and includes the NR based PC5. The Uu reference point is a reference point between a UE (e.g., UE 1A) and an NG-RAN 20. Although not shown in
The N1 reference point is a reference point between a UE 1 (e.g., UE 1A) and an Access and Mobility management Function (AMF) 41 in a 5G Core Network (5GC) 40. The N1 reference point can be used to send V2X policies and parameters from the AMF 41 to the UE 1, and to send the V2X capability and PC5 capability of the UE 1 for V2X communication from the UE 1 to the AMF 41. The N2 reference point is a reference point between the NG-RAN 20 and the AMF 41. The N2 reference point may be used to send V2X policies and parameters from the AMF 41 to the NG-RAN 20. The AMF 41 is one of the network function nodes in the control plane of the 5GC 40. The AMF 41 terminates a single signalling connection (i.e., N1 NAS signalling connection) with the UE 1 (e.g., UE 1A) and provides registration, connection management, and mobility management. The AMF 41 provides network function (NF) services on a service-based interface (i.e., Namf interface) to NF consumers (e.g., Session Management Function (SMF) 42). The NF services provided by the AMF 41 include a communication service (Namf_Communication). The communication service allows an NF consumer (e.g., SMF 42) to communicate with the UE 1 or the NG-RAN 20 through the AMF 41.
The N3 reference point is a reference point between the NG-RAN 20 and a User Plane Function (UPF) 43 in the 5GC. The N6 reference point is a reference point between the UPF 43 and the DN 50. The UPF 43 is one of the network function nodes in the user plane of the 5GC 40. The UPF 43 processes and forwards user data. The functionality of the UPF 43 is controlled by the SMF 42 through the N4 reference point. The UPF 43 may include multiple UPFs connected through N9 reference points. For example, to enable the V2X application 11B in the UE 1A to communicate with the V2X application in the V2X application server 61, the UE 1A uses a path, association, session, or connection through the Uu, N3, and N6 reference points.
The 5G system shown in
The PC5 interface 103 supports the PC5 Signaling (PC5-S) protocol. As shown in
There is a one-to-one correspondence between the PC5 unicast link and the PC5-RRC connection. The PC5-RRC connection is a logical connection between two UEs 1 for a pair of a Source Layer-2 ID and a Destination Layer-2 ID. The PC5-RRC connection is considered to be established after the corresponding PC5 unicast link is established. In other words, the PC5-RRC connection is established in response to the establishment of its corresponding PC5 unicast link. Specifically, when the transmission of a PC5-S message to a specific destination is requested by the upper layers of a sidelink signalling radio bearer (SL SRB), the UE 1 (RRC layer) establishes a PDCP entity, an RLC entity, and an SCCH of the SL SRB for the PC5-S message, based on a predefined SCCH configuration, and then considers a PC5-RRC connection to be established for the destination. Alternatively, when the establishment of a PC5-RRC connection for a specific destination is indicated by the upper layers, the UE 1 (RRC layer) establishes a PDCP entity, an RLC entity, and an SCCH of the SL SRB for PC5-RRC messages for this destination, based on a predefined SCCH configuration, and then considers this PC5-RRC connection to be established.
NR sidelink communication on the NR PC5 interface 103 supports two resource allocation modes, i.e., mode 1 and mode 2.
In resource allocation mode 1, the RAN node 2 (e.g., gNB) performs resource allocation. For example, the RAN node 2 allocates or schedules SL radio resources to the UE I using the NR Uu interface 101. Resource allocation by mode 1 includes a dynamic grant and a configured grant.
In the case of a dynamic grant, the UE 1 should request resources from the RAN node 2 for the transmission of every single transport block. Specifically, the UE 1 sends a MAC Control Element (CE) (i.e., Sidelink BSR MAC CE) indicating a Sidelink Buffer Status Report (BSR) to the RAN node 2 via an Uplink Shared Channel (UL-SCH) and a Physical Uplink Shared Channel (PUSCH), and the RAN node 2 sends Downlink Control Information (DCI) indicating a dynamic sidelink grant to the UE 1 via a Physical Downlink Control Channel (PDCCH). A dynamic sidelink grant provides allocation of resources for the transmission (and retransmission) of a single transport block. When sidelink carrier aggregation, described below, is configured, a dynamic sidelink grant may provide an allocation of resources for one transport block per sidelink (component) carrier.
In the case of a configured grant, the RAN node 2 allows periodic sidelink resources to the UE 1, which are semi-statically configured by the RRC. Specifically, the UE 1 can send UE assistance information about a sidelink communication traffic pattern to the RAN node 2. Such UE assistance information, or sidelink traffic pattern information sent in UE assistance information, may be referred to as configured grant assistance information. The sidelink traffic pattern information (or configured grant assistance information) may include, for example, the maximum transport block size based on an observed traffic pattern; an estimated timing of packet arrival on a sidelink logical channel; and an estimated data arrival cycle on a sidelink logical channel. The UE 1 sends UE assistance information, including sidelink traffic pattern information, using an RRC message (e.g., UEassistanceinformation message). The RAN node 2 may consider the sidelink traffic pattern information received from the UE 1 and generate a configured grant. The RAN node 2 transmits a configured grant to the UE 1 using an RRC message (e.g., RRCReconfiguration message). A configured grant indicates an allocation of time and frequency resources and the cycle of that resource allocation. There are two types of configured grant for mode 1. In configured grant type 1, a configured grant can be configured or released to the UE 1 by RRC signaling and can be used immediately. In the case of configured grant type 2, the RAN node 2 configures a configured grant to the UE 1 via RRC signaling and activates or deactivates this configured grant via DCI signaling. The UE 1 can only use the periodic resources allocated by the configured grant after it has been activated by the RAN node 2 and only until it is deactivated.
On the other hand, in resource allocation mode 2, the UE 1 autonomously selects resources based on sensing by the UE 1. The sensing is performed in a preconfigured resource pool. If resources are not being used by other UEs for high priority traffic, the UE 1 can select these resources for sidelink transmission and retransmission. The UE 1 is allowed to transmit and retransmit on the selected resources a certain number of times until a resource reselection reason is triggered.
The UEs 1A and 1B support carrier aggregation (CA) on the NR PC5 interface (or NR sidelink) 103. In other words, the UEs 1A and 1B support NR sidelink carrier aggregation, i.e., carrier aggregation for NR sidelink communication. Sidelink carrier aggregation can also be referred to as multicarrier operation. Sidelink carrier aggregation allows the UEs 1A and 1B to communicate with each other on multiple sidelink carriers. Similar to the terminology used for the Uu interface, multiple sidelink carriers used in sidelink carrier aggregation can be referred to as component carriers. In one example, one or more of the multiple sidelink carriers may belong to a licensed spectrum (or licensed band) licensed to the RAN node 2 (or NG-RAN 20) or its operator, while the other one or more may belong to an unlicensed spectrum. The unlicensed spectrum may be ITS spectrum for intelligent transportation systems (ITS).
The UE 1A and the UE 1B support sidelink carrier aggregation in unicast transmissions. The UE 1A and the UE 1B may support sidelink carrier aggregation in groupcast transmissions. The UE 1A and the UE 1B may support sidelink carrier aggregation in broadcast transmissions.
In sidelink carrier aggregation, one or both of the UEs 1A and 1B may not necessarily be able to transmit on multiple sidelink carriers simultaneously. In other words, one or both of the UEs 1A and 1B may not support transmission on multiple sidelink carriers in the same time slot. A UE with such limited transmission capabilities may be referred to as a limited Tx capability UE. For example, the limited Tx capability may be due to the fact that the number of transmission chains in the UE 1 is less than the number of configured transmit sidelink carriers. Alternatively, the limited Tx capability may be due to the UE 1 not supporting a band combination of configured transmit sidelink carriers. Alternatively, the limited Tx capability may be due to the time required to switch between transmission chains in the UE 1. Alternatively, the limited Tx capability may be due to the inability of the UE 1 to meet radio frequency (RF) requirements such as power spectral density (PSD) imbalance.
Similarly, in sidelink carrier aggregation, one or both of the UEs 1A and 1B may not necessarily be able to receive on multiple sidelink carriers simultaneously. In other words, one or both of the UEs 1A and 1B may not support receiving on multiple sidelink carriers in the same time slot. A UE with such limited receive capabilities may be referred to as a limited Rx capability UE.
The Physical Layer 620 supports multiple sidelink carriers. If the UE supports transmission on multiple sidelink carriers in the same time slot, the physical layer 620 can transmit a transport block (or MAC Protocol Data Unit (PDU)) on each sidelink carrier in the same time slot. The physical layer 620 offers transport channels to the MAC sublayer 601.
The MAC sublayer 601 provides a single MAC entity for transmission and reception on multiple sidelink carriers. The MAC entity provides a hybrid automatic repeat request (HARQ) entity per sidelink carrier. A single HARQ entity maintains multiple HARQ processes, allowing transmissions to continue on the corresponding sidelink carrier while waiting for HARQ feedback on the success or failure of previous transmissions.
The MAC sublayer 601 offers logical channels to the RLC sublayer 602. The MAC sublayer 601 provides a mapping between logical channels and transport channels, and multiplexes MAC Service Data Units (SDUs) belonging to the same or to different logical channels. Transport channels used in the NR sidelink include a Sidelink Shared Channel (SL-SCH) and a Sidelink Broadcast Channel (SL-BCH). Logical channels used in the NR sidelink include a Sidelink Control Channel (SCCH), a Sidelink Traffic Channel (STCH), and a Sidelink Broadcast Control Channel (SBCCH). SCCH is a control channel and is mapped to SL-SCH. STCH is a traffic channel and is mapped to SL-SCH in a similar way to SCCH. SBCCH is a control channel and is mapped to SL-BCH.
The MAC sublayer 601 provides scheduling for the NR sidelink. This scheduling includes priority handling among multiple logical channels through logical channel prioritization.
If the UE supports transmission on multiple sidelink carriers in the same time slot and has a grant on each of the multiple sidelink carriers, the MAC sublayer provides multiple transport blocks (MAC PDUs) to the physical layer 620 through multiple transport channels (i.e., SL-SCHs), each associated with a respective one of the multiple sidelink carriers, in order to transmit on the multiple sidelink carriers in the same time slot. Each grant may be a dynamic grant or a configured grant in resource allocation mode 1. Alternatively, if the MAC entity is configured with sidelink resource allocation mode 2 to transmit using a resource pool, the MAC entity may generate a sidelink grant selected based on random selection or sensing in the resource pool.
The RLC sublayer 602 offers RLC channels to the PDCP sublayer 603. The RLC sublayer 602 supports three transmission modes, Acknowledged Mode (AM), Unacknowledged Mode (UM), and Transparent Mode (TM). In AM and UM, the RLC sublayer 602 provides segmentation of RLC SDUs. In AM, the RLC sublayer 602 provides ARQ (i.e., retransmission of RLC SDUs or RLC SDU segments).
The PDCP sublayer 603 offers Data Radio Bearers (DRBs) to the SDAP sublayer 604. The PDCP sublayer 603 receives user plane data of DRBs from the SDAP sublayer 604 and provides header compression, integrity protection, and ciphering, for example.
In addition, the PDCP sublayer 603 offers Signalling Radio Bearers (SRBs) to upper layers (i.e., PC5-S layer, PC5-RRC layer). The PDCP sublayer 603 receives control plane data (i.e., PC5-S and PC5-RRC messages) of SRBs from the PC5-S layer and the PC5-RRC layer and provides integrity protection and ciphering, for example.
The SDAP sublayer 604 provides Quality of Service (Qos) flow handling. A QoS flow may be an Internet Protocol (IP) flow, i.e., IP packets. Alternatively, a QoS flow may be a non-IP flow, i.e., non-IP packets. The SDAP sublayer 604 provides a mapping between Qos flows and SL DRBs. There is one SDAP entity per destination for one of unicast, groupcast, and broadcast associated with that destination.
HARQ feedback is used for unicast and groupcast communications and is transmitted on a Physical Sidelink Feedback Channel (PSFCH). A receiving UE (e.g., UE 1B) receives a unicast or groupcast from a transmitting UE (e.g., UE 1A) on a Physical Sidelink Shared Channel (PSSCH) and transmits HARQ feedback for the reception of this PSSCH on a PSFCH.
In a resource pool, a set of Physical Resource Blocks (PRBs) contained in available PSFCH symbols for a PSFCH is represented by a bitmap. For a single PSFCH transmission, one PRB in a PSFCH symbol is used to transmit a cyclic shift code (specifically, a Zadoff-Chu sequence). Code division multiplexing (CDM) with a cyclic shift code (i.e., Zadoff-Chu sequence) is used to distinguish between ACK feedback and NACK feedback. In addition, CDM is used to multiplex multiple PSFCH transmissions from multiple receiving UEs into a single PRB. That is, each PSFCH is mapped to a time resource (i.e., a PSFCH symbol), a frequency resource (i.e., a PRB), and a code resource (i.e., a Zadoff-Chu sequence) in a slot.
A receiving UE (e.g., UE 1B) performs a Physical Sidelink Feedback Channel (PSFCH) transmission in response to a PSSCH received a few slots earlier. How many slots later a UE that has received a PSSCH transmission in a given slot can transmit HARQ feedback for that PSSCH transmission in a PSFCH symbol depends on the period of the PSFCH symbols, and also on the minimum time gap between the slot with the PSSCH transmission and the slot containing the HARQ feedback. Within a resource block, resources for PSFCH are configured periodically, for example, in cycles of 1, 2, or 4 slots. In other words, within a resource pool, there is a slot with a PSFCH every 1, 2, or 4 slots. In addition, for each resource pool, a minimum number of slots (i.e., minimum time gap) is configured between the slot with the PSSCH transmission and the slot containing the PSFCH for HARQ feedback for that PSSCH transmission. For example, the minimum time gap is 2 or 3.
Specifically, a sidelink resource pool configuration may include PSFCH-related configurations (e.g., SL-PSFCH-Config), including a configuration of the PRBs to be used for PSFCH transmission and reception (e.g., sl-PSFCH-RB-Set), a configuration of the PSFCH period (e.g., sl-PSFCH-Period), and a configuration of the minimum time gap (e.g., sl-MinTimeGapPSFCH). The sidelink resource pool configuration (e.g., SL-BWP-PoolConfigCommon) can be included in a sidelink common configuration (e.g., SL-ConfigCommon) that is broadcast in the system information (e.g., System Information Block 12 (SIB12)). Alternatively, the sidelink resource pool configuration (e.g., SL-BWP-PoolConfig) can be included in a sidelink configuration (e.g., SL-BWP-PoolConfig in sl-ConfigDedicatedNR) that is sent in a UE-specific RRC message (e.g., RRCReconfiguration message). Alternatively, the sidelink resource pool configuration (e.g., SL-BWP-PoolConfigCommon) can be included in a sidelink configuration (e.g., SL-BWP-PoolConfig in SL-PreconfigurationNR) that is preconfigured in the UE.
The receiving UE transmits a PSFCH in the first slot that contains a PSFCH resource and is at least the number of slots later than the last slot of the PSFCH reception as specified in the minimum time gap configuration (e.g., sl-MinTimeGapPSFCH) of the resource pool. Accordingly, if the PSFCH period is four slots, HARQ feedback for PSSCH transmissions in four PSSCH slots can be transmitted in multiple PRBs within a single PSFCH symbol in a single slot.
This example embodiment provides improvements related to carrier aggregation in the NR sidelink. Specifically, this example embodiment relates to the transmission of multiple HARQ feedbacks about multiple PSSCH receptions on multiple sidelink carriers. The configuration and operation of a radio communication system and network elements (or apparatuses, nodes, devices, or network functions) in this example embodiment may be the same as in the examples described with reference to
In step 701, the UE 1B receives a first sidelink transmission (i.e., PSSCH) from the peer UE 1A on the first sidelink carrier and a second sidelink transmission (i.e., PSSCH) from the peer UE 1A on the second sidelink carrier. The first sidelink transmission may be transmitted in the same time slot (i.e., slot or subframe) as the second sidelink transmission or in a different time slot. These sidelink transmissions can be unicast or groupcast. The first sidelink carrier may belong to a licensed spectrum and the second sidelink carrier may belong to an unlicensed spectrum. The unlicensed spectrum can be ITS spectrum.
In step 702, the UE 1B transmits a first HARQ feedback for the first sidelink transmission and a second HARQ feedback for the second sidelink transmission using multiple PSFCH resources in the same time slot of the first sidelink carrier. In other words, the second HARQ feedback for the second sidelink transmission is transmitted on a PSFCH symbol on the first sidelink carrier that is different from the second sidelink carrier on which the second sidelink transmission was performed.
To support this cross-carrier HARQ feedback, the structure of a slot in which a Physical Sidelink Control Chanel (PSCCH), a PSSCH, and a PSFCH are transmitted may be extended or improved. In particular, the PSSCH resource for the first HARQ feedback and the PSSCH resource for the second HARQ feedback may be located in different symbols, different resource blocks, or different symbols and different resource blocks in the same time slot.
The UE 1B may determine multiple PSFCH resources for the first and second HARQ feedbacks based on a resource pool configuration of the first sidelink carrier. The resource pool configuration of the first sidelink carrier may indicate the arrangement of multiple PSFCH symbols to be used for the first HARQ feedback for a sidelink transmission on the first sidelink carrier and the arrangement of multiple PSFCH symbols to be used for the second HARQ feedback for a sidelink transmission on the second sidelink carrier.
In some implementations, a PSFCH configuration (e.g., SL-PSFCH-Config) included in the resource pool configuration of the first sidelink carrier may include a configuration of the PRBs to be used for PSFCH transmission and reception for the first HARQ feedback (e.g., sl-PSFCH-RB-Set) and a configuration of its PSFCH period (e.g., sl-PSFCH-Period). In addition, the PSFCH configuration may include a configuration of the PRBs to be used for PSFCH transmission and reception for the second HARQ feedback (e.g., sl-PSFCH-RB-Set-secondarycarrier) and a configuration of its PSFCH period (e.g., sl-PSFCH-Period-secondarycarrier). A minimum time gap configuration (e.g., sl-MinTimeGapPSFCH) may be common to the first and second HARQ feedbacks. Alternatively, the PSFCH configuration may include a minimum time gap configuration (e.g., sl-MinTimeGapPSFCH-secondarycarrier) for the second HARQ feedback in addition to a minimum time gap configuration (e.g., sl-MinTimeGapPSFCH) for the first HARQ feedback. In an example, the PSFCH period (e.g., 12) for the second HARQ feedback may be an integer multiple of the PSFCH period (e.g., 4) for the first HARQ feedback.
The resource pool configuration of the first sidelink carrier may be preconfigured in a non-volatile memory of a Mobile Equipment (ME), or in a Universal Subscriber Identity Module (USIM), of the UE 1B. The UE 1B may receive the resource pool configuration from a core network node (e.g., AMF 41, PCF 44) via the N1 reference point between the AMF 41 and the UE 1B. Alternatively, the UE 1A may receive the resource pool configuration from the V2X application server 61 via the V1 reference point between the UE 1B and the V2X application server 61.
When the UE 1B is within the coverage of the NG-RAN 20 (e.g., RAN node 2), the UE 1B may receive the resource pool configuration of the first sidelink carrier from the NG-RAN 20 (e.g., RAN node 2).
The operation of the UE 1 described with reference to
This example embodiment provides improvements related to carrier aggregation in the NR sidelink. Specifically, this example embodiment relates to the transmission of multiple HARQ feedbacks about multiple PSSCH receptions on multiple sidelink carriers. The configuration and operation of a radio communication system and network elements (or apparatuses, nodes, devices, or network functions) in this example embodiment may be the same as in the examples described with reference to
Step 801 is similar to step 701 in
In step 802, if a first PSFCH transmission on the first sidelink carrier for a HARQ feedback for the first sidelink transmission overlaps in time with a second PSFCH transmission on the second sidelink carrier for a HARQ feedback for the second sidelink transmission, the UE 1B delays the second PSFCH transmission on the second sidelink carrier to the next or subsequent PSFCH transmission occasion. For example, if the second PSFCH transmission on the second sidelink carrier is in the same slot as the first PSFCH transmission on the first sidelink carrier, the UE 1B may delay the second PSFCH transmission on the second sidelink carrier to the next or subsequent PSFCH transmission occasion.
The amount by which the second PSFCH transmission is delayed may be predefined in the 3GPP specification. A configuration indicating the amount by which the second PSFCH transmission is delayed may be preconfigured in a non-volatile memory of a Mobile Equipment (ME), or in a Universal Subscriber Identity Module (USIM), of the UE 1B. The UE 1B may receive this configuration from a core network node (e.g., AMF 41, PCF 44) via the NI reference point between the AMF 41 and the UE 1B. The UE 1A may receive the resource pool configuration from the V2X application server 61 via the V1 reference point between the UE 1B and the V2X application server 61. When the UE 1B is within the coverage of the NG-RAN 20 (e.g., RAN node 2), the UE 1B may receive the configuration indicating the amount by which the second PSFCH transmission is delayed from the NG-RAN 20 (e.g., RAN node 2).
The operation of the UE 1 described with reference to
This example embodiment provides improvements related to carrier aggregation in the NR sidelink. Specifically, this example embodiment relates to the transmission of multiple HARQ feedbacks about multiple PSSCH receptions on multiple sidelink carriers. The configuration and operation of a radio communication system and network elements (or apparatuses, nodes, devices, or network functions) in this example embodiment may be the same as in the examples described with reference to
Step 901 is similar to step 701 in
In step 902, if a first PSFCH transmission on the first sidelink carrier for a HARQ feedback for the first sidelink transmission overlaps in time with a second PSFCH transmission on the second sidelink carrier for a HARQ feedback for the second sidelink transmission, the UE 1B selects whether to perform the first PSFCH transmission or the second PSFCH transmission.
In a first implementation, the UE 1B may select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a priority of the first sidelink transmission (PSSCH transmission) and a priority of the second sidelink transmission (PSSCH transmission). Specifically, the UE IB may choose to perform a PSFCH transmission with respect to a higher priority sidelink transmission (PSSCH transmission). The priority of the PSSCH transmission may be based on the priority of the transport block, in particular the priority of the logical channel contained in the transport block.
In a second implementation, the UE 1B may select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a Channel Busy Ratio (CBR) of the first sidelink carrier and a CBR of the second sidelink carrier. Specifically, the UE 1B may choose to perform a PSFCH transmission on a sidelink carrier with a lower CBR.
In a third implementation, the UE 1B may select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a Sidelink Reference Signal Received Power (SL-RSRP) of the first sidelink carrier and an SL-RSRP of the second sidelink carrier. Specifically, the UE 1B may choose to perform a PSFCH transmission on a sidelink carrier with a better SL-RSRP.
In a fourth implementation, the UE 1B may choose to perform a PSFCH transmission on a predetermined one of the sidelink carriers. For example, the UE 1B may always choose to perform the first PSFCH transmission on the first sidelink carrier and not perform the second PSFCH transmission on the second sidelink carrier.
The operation of the UE 1 described with reference to
The RAN node 2 may create a resource pool configuration of a first sidelink carrier such that the arrangement of periodic slots containing PSFCH symbols in the resource pool of the first sidelink carrier does not overlap, in whole or at least in part, with the arrangement of periodic slots containing PSFCH symbols in a resource pool of a second sidelink carrier. The RAN node 2 may provide the UE 1 with the resource pool configuration of the first sidelink carrier created in this way. This helps to reduce or eliminate the situation where a second PSFCH transmission on the second sidelink carrier overlaps in time with a first PSFCH transmission on the first sidelink carrier.
Examples of configurations of the UE 1, the RAN node 2, core network nodes such as the AMF 41, and the V2X application server 61 according to the plurality of example embodiments described above are provided below.
The baseband processor 1103 performs digital baseband signal processing (data-plane processing) and control-plane processing for wireless communication. The digital baseband signal processing includes (a) data compression/decompression, (b) data segmentation/concatenation, (c) transmission format (transmission frame) composition/decomposition, (d) channel encoding/decoding, (e) modulation (i.e., symbol mapping)/demodulation, and (f) Inverse Fast Fourier Transform (IFFT) generation of OFDM symbol data (baseband OFDM signal). On the other hand, the control-plane processing includes communication management of layer 1 (e. g., transmission power control), layer 2 (e.g., radio resource management, and hybrid automatic repeat request (HARQ) processing), and layer 3 (e.g., signaling regarding attach, mobility, and call management).
For example, the digital baseband signal processing performed by the baseband processor 1103 may include signal processing in the Service Data Adaptation Protocol (SDAP) layer, Packet Data Convergence Protocol (PDCP) layer, Radio Link Control (RLC) layer, Medium Access Control (MAC) layer, and Physical (PHY) layer. The control-plane processing performed by the baseband processor 1103 may include processing of Non-Access Stratum (NAS) protocols, Radio Resource Control (RRC) protocols, MAC Control Elements (CEs), and Downlink Control Information (DCIs). The control-plane processing may include processing of PC5-S signaling and PC5-RRC signaling.
The baseband processor 1103 may perform Multiple Input Multiple Output (MIMO) encoding and precoding for beamforming.
The baseband processor 1103 may include a modem processor (e.g., Digital Signal Processor (DSP)) that performs the digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) that performs the control-plane processing. In this case, the protocol stack processor performing the control-plane processing may be integrated with an application processor 1104 described later.
The application processor 1104 may also be referred to as a CPU, an MPU, a microprocessor, or a processor core. The application processor 1104 may include a plurality of processors (processor cores). The application processor 1104 loads a system software program (Operating System (OS)) and various application programs (e.g., a voice call application, a web browser, a mailer, a camera operation application, a music player application) from a memory 1106 or from another memory (not shown) and executes these programs, thereby providing various functions of the UE 1.
In some implementations, as represented by the dashed line (1105) in
The memory 1106 is a volatile memory or a non-volatile memory, or a combination thereof. The memory 1106 may include a plurality of physically independent memory devices. The volatile memory is, for example, Static Random Access Memory (SRAM), Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory may be a Mask Read Only Memory (MROM), an Electrically Erasable Programmable ROM (EEPROM), a flash memory, a hard disk drive, or any combination thereof. The memory 1106 may include, for example, an external memory device that can be accessed by the baseband processor 1103, the application processor 1104, or the SoC 1105. The memory 1106 may include an internal memory device that is integrated into the baseband processor 1103, the application processor 1104, or the SoC 1105. Further, the memory 1106 may include a memory in a Universal Integrated Circuit Card (UICC).
The memory 1106 may store one or more software modules (computer programs) 1107 including instructions and data for processing by the UE 1 described in the above example embodiments. In some implementations, the baseband processor 1103 or the application processor 1104 may load the software module(s) 1107 from the memory 1106 and execute the loaded software module(s) 1107, thereby performing the processing of the UE 1 described in the above example embodiments with reference to the drawings.
The control-plane processing and operations performed by the UE 1 described in the above example embodiments can be achieved by elements other than the RF transceiver 1101 and the antenna array 1102, i.e., achieved by the memory 1106, which stores the software module(s) 1107, and one or both of the baseband processor 1103 and the application processor 1104.
The network interface 1103 is used to communicate with network nodes (e.g., other RAN nodes, and control and transfer nodes in the core network). The network interface 1103 may include, for example, a Network Interface Card (NIC) that complies with the IEEE 802.3 series.
The processor 1104 performs digital baseband signal processing (data-plane processing) and control-plane processing for wireless communication. The processor 1104 may include a plurality of processors. For example, the processor 1104 may include a modem processor (e.g., Digital Signal Processor (DSP)) for performing the digital baseband signal processing and a protocol stack processor (e.g., Central Processing Unit (CPU) or Micro Processing Unit (MPU)) for performing the control-plane processing. The processor 1104 may include a digital beamformer module for beamforming. The digital beamformer module may include a Multiple Input Multiple Output (MIMO) encoder and precoder.
The memory 1105 consists of a combination of a volatile memory and a non-volatile memory. The volatile memory is, for example, a Static Random Access Memory (SRAM), a Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory may be a Mask Read Only Memory (MROM), an Electrically Erasable Programmable ROM (EEPROM), a flash memory, or a hard disk drive, or any combination thereof. The memory 1105 may include a storage located away from the processor 1104. In this case, the processor 1104 may access the memory 1105 through the network interface 1103 or another I/O interface.
The memory 1105 may store one or more software modules (computer programs) 1106 including instructions and data for performing processing by the RAN node 2 described in the above example embodiments. In some implementations, the processor 1104 may be configured to load and execute the software module(s) 1106 from the memory 1105, thereby performing the processing of the RAN node 2 described in the above example embodiments.
If the RAN node 2 is a Central Unit (CU) (e.g., gNB-CU) or a CU Control Plane Unit (CU-CP) (e.g., gNB-CU-CP), the RAN node 2 does not need to include the RF transceiver 1101 (and antenna array 1102).
The processor 1202 may be, for example, a microprocessor, a Micro Processing Unit (MPU), or a Central Processing Unit (CPU). The processor 1202 may include a plurality of processors.
The memory 1203 consists of a combination of a volatile memory and a non-volatile memory. The memory 1203 may include multiple physically independent memory devices. The volatile memory is, for example, a Static Random Access Memory (SRAM), a Dynamic RAM (DRAM), or a combination thereof. The non-volatile memory may be a Mask Read Only Memory (MROM), an Electrically Erasable Programmable ROM (EEPROM), a flash memory, or a hard disk drive, or any combination thereof. The memory 1203 may include a storage located away from the processor 1202. In this case, the processor 1202 may access the memory 1203 through the network interface 1201 or another I/O interface.
The memory 1203 may store one or more software modules (computer programs) 1204 including instructions and data for performing processing by the AMF 41 described in the above example embodiments. In some implementations, the processor 1202 may be configured to load and execute the software module(s) 1204 from the memory 1203, thereby performing the processing of the AMF 41 described in the above example embodiments.
As described using
The example embodiments described above are merely examples of applications of the technical ideas of the inventor. These technical ideas are not limited to the above-described example embodiments, and various modifications may be made thereto.
For example, the whole or part of the example embodiments disclosed above can be described as, but not limited to, the following supplementary notes.
A radio terminal comprising:
The radio terminal according to Supplementary Note 1, wherein the plurality of PSFCH resources is located in different symbols, different resource blocks, or different symbols and different resource blocks within the identical time slot.
The radio terminal according to Supplementary Note 1 or 2, wherein the at least one processor is configured to determine the plurality of PSFCH resources based on a resource pool configuration of the first sidelink carrier, wherein
The radio terminal according to Supplementary Note 3, wherein the resource pool configuration of the first sidelink carrier is preconfigured in a non-volatile memory of a Mobile Equipment (ME), or in a Universal Subscriber Identity Module (USIM), of the radio terminal.
The radio terminal according to Supplementary Note 3, wherein the at least one processor is configured to receive the resource pool configuration of the first sidelink carrier from a radio access network.
The radio terminal according to any one of Supplementary Notes 1 to 5, wherein the reception of the first sidelink transmission is performed in a same time slot as the reception of the second sidelink transmission.
A method performed by a radio terminal, the method comprising:
A program for causing a computer to perform a method for a radio terminal, the method comprising:
A radio terminal comprising:
The radio terminal according to Supplementary Note 9, wherein the reception of the first sidelink transmission is performed in a same time slot as the reception of the second sidelink transmission.
A method performed by a radio terminal, the method comprising:
A program for causing a computer to perform a method for a radio terminal, the method comprising:
A radio terminal comprising:
The radio terminal according to Supplementary Note 13, wherein the at least one processor is configured to select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a priority of the first sidelink transmission and a priority of the second sidelink transmission.
The radio terminal according to Supplementary Note 13, wherein the at least one processor is configured to select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a Channel Busy Ratio (CBR) of the first sidelink carrier and a CBR of the second sidelink carrier.
The radio terminal according to Supplementary Note 13, wherein the at least one processor is configured to select whether to perform the first PSFCH transmission or the second PSFCH transmission based on a Sidelink Reference Signal Received Power (SL-RSRP) of the first sidelink carrier and an SL-RSRP of the second sidelink carrier.
The radio terminal according to any one of Supplementary Notes 13 to 16, wherein the reception of the first sidelink transmission is performed in a same time slot as the reception of the second sidelink transmission.
A method performed by a radio terminal, the method comprising:
A program for causing a computer to perform a method for a radio terminal, the method comprising:
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2022-038089, filed on Mar. 11, 2022, the disclosure of which is incorporated herein in its entirety by reference.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2022-038089 | Mar 2022 | JP | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2023/004130 | 2/8/2023 | WO |
