Patent Application
20230188293
The present disclosure relates generally to wireless communications, and, in particular embodiments, to a system and method for uplink and downlink in multi-point communications.
Wireless communication systems include long term evolution (LTE), LTE-A, LTE-A-beyond systems, 5G LTE, 5G New Radio (NR), etc. A modern wireless communication system may include a plurality of NodeBs (NBs), which may also be referred to as base stations, network nodes, communications controllers, cells or enhanced NBs (eNBs), and so on. A NodeB may include one or more network points or network nodes using different radio access technologies (RATs) such as high speed packet access (HSPA) NBs or WiFi access points. A NodeB may be associated with a single network point or multiple network points. A cell may include a single network point or multiple network points, and each network point may have a single antenna or multiple antennas. A network point may correspond to multiple cells operating in multiple component carriers. Generally each component carrier in carrier aggregation is a serving cell, either a primary cell (PCell) or a secondary cell (SCell).
A cell or NodeB may serve a number of users (also commonly referred to as User Equipment (UE), mobile stations, terminals, devices, and so forth) over a period of time. A communication channel from a base station to a UE is generally referred to as a downlink (DL) channel, and a transmission from the base station to the UE is a downlink transmission. A communication channel from a UE to a base station is generally referred to an uplink (UL) channel, and a transmission from the UE to the base station is an uplink transmission. The UE receives timing advance (TA) commands associated with the configured TA group (TAG) to adjust its uplink transmission timing to synchronize with the network for uplink transmission so that uplink transmissions from multiple UEs arrive at the base station at about the same time in a transmission time interval (TTI). Likewise, the UE needs to receive DL reference signals (RS) or synchronization signal (SS) blocks, also called SS/physical broadcast channel (PBCH) block (SSB) to acquire and maintain the DL synchronization, such as via maintaining a DL timing tracking loop, based on which the UE places its FFT window inside the cyclic prefix (CP) for its DL reception. In addition, both UL and DL signals/channels need to be associated with some other signals for deriving the signal/channel properties, such as delay spread, Doppler shift, etc.
The present disclosure is directed to methods and systems for wireless communications, and, in particular embodiments, to a system and method for uplink and downlink in multi-point communications. The methods and systems as described herein can be an applicable solution for multiple-transmission-reception-points (M-TRP) scenarios in LTE and 5G (new radio) systems.
In a first implementation, a method for wireless communication includes: receiving, by a user equipment (UE), first configuration information of a bandwidth part (BWP) in a carrier for a serving cell, the first configuration information comprising a first group of parameters and a first resource group (RG) on the BWP in the carrier for the serving cell; receiving, by the UE, second configuration information of the BWP in the carrier, the second configuration information comprising a second group of parameters and a second RG on the BWP in the carrier; and performing transmission or reception associated with the first RG based on the first group of parameters and performing transmission or reception associated with the second RG based on the second group of parameters.
In a second implementation, an electronic device includes: a non-transitory memory storage comprising instructions, and one or more hardware processors in communication with the memory storage, where the one or more hardware processors execute the instructions to perform operations including: receiving first configuration information of a bandwidth part (BWP) in a carrier for a serving cell, the first configuration information comprising a first group of parameters and a first resource group (RG) on the BWP in the carrier for the serving cell; receiving second configuration information of the BWP in the carrier, the second configuration information comprising a second group of parameters and a second RG on the BWP in the carrier; and performing transmission or reception associated with the first RG based on the first group of parameters and performing transmission or reception associated with the second RG based on the second group of parameters.
In a third implementation, a non-transitory computer-readable medium storing computer instructions for wireless communication, that when executed by one or more hardware processors, cause the one or more hardware processors to perform operations including: receiving, by a user equipment (UE), first configuration information of a bandwidth part (BWP) in a carrier for a serving cell, the first configuration information comprising a first group of parameters and a first resource group (RG) on the BWP in the carrier for the serving cell; receiving, by the UE, second configuration information of the BWP in the carrier, the second configuration information comprising a second group of parameters and a second RG on the BWP in the carrier; and performing transmission or reception associated with the first RG based on the first group of parameters and performing transmission or reception associated with the second RG based on the second group of parameters.
In a fourth implementation, a method for wireless communication includes: receiving, by a user equipment (UE), first configuration information of a bandwidth part (BWP) in a carrier for a serving cell, the first configuration information comprising a first group of parameters on the BWP in the carrier for the serving cell, the first group of parameters comprising a first physical cell identifier (PCI) of the serving cell; receiving, by the UE, second configuration information of the BWP in the carrier, the second configuration information comprising a second group of parameters on the BWP in the carrier, the second group of parameters comprising a second PCI; and performing transmission or reception based on the first group of parameters and performing transmission or reception based on the second group of parameters.
The previously described implementation is implementable using a computer-implemented method; a non-transitory, computer-readable medium storing computer-readable instructions to perform the computer-implemented method; and a computer-implemented system comprising a computer memory interoperably coupled with a hardware processor configured to perform the computer-implemented method and the instructions stored on the non-transitory, computer-readable medium.
The details of one or more implementations of the subject matter of this specification are set forth in the accompanying drawings and the description. Other features, aspects, and advantages of the subject matter will become apparent from the description, the drawings, and the claims.
For a more complete understanding of the present disclosure, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
In the figures, items in square brackets are optional, and dashed lines are for optional relations/transmissions.
In multiple-transmission-reception-points (M-TRP) communications, a UE, a transmission or a reception in a serving cell of a carrier or a bandwidth part (BWP, which may be seen as a portion of the carrier that the UE is currently operating on for the carrier) needs to adjust the transmission/reception timing and properties based on with which TRP the transmission/reception is. For example, if the uplink transmission timing for multiple TRPs over the carrier or BWP using the same TA of the TAG associated with the serving cell, it may cause inaccurate uplink timing of the UE in communication with a TRP not co-located (NCLed) with the serving cell of the UE, e.g., when the TRP is not synchronized with the serving cell, when the TRP and the serving cell have a non-ideal backhaul, and/or when the TRP is located far away from the serving cell, and a difference of propagation delays of the UE with the TRP and the serving cell cannot be neglected in adjusting uplink timing of the UE. The inaccurate uplink timing may negatively affect the UE's physical uplink control channel (PUCCH)/physical uplink shared channel (PUSCH) reliability, spectrum efficiency, and sounding accuracy for uplink/downlink multi-input multi-output (MIMO) channel state information (CSI) acquisition. Thus, the UE needs to be configured with separate TAGs for the serving cell and the NCLed TRP, and applies different TA when transmitting to different TRPs. Similarly, the UE's DL timing maintained via tracking loop should also be adjusted based on which TRP is transmitted to the UE. M-TRP allows the UE to receive from multiple TRPs on possibly overlapping time-frequency resources. Therefore, the UE may need to maintain multiple DL tracking loops, one for each NCLed TRP, and apply the associated FFT windows to receive DL transmissions from TRPs respectively. Consequently, the UL/DL signals/channels, or generally, radio resources, may need to be separated into groups, called resource groups (RGs), according to the NCLed TRPs.
Embodiments of the present disclosure provide example methods for M-TRP communications of a UE in a serving cell over a carrier/BWP of the serving cell, with separate RGs configured for different TRPs. Example methods described in some embodiments improve UL/DL transmission/reception qualities of the UE in the M-TRP communications. Some embodiments of the present disclosure also provide example methods for configuring the TRPs with separate RGs, and acquiring/obtaining/maintaining timings and association relationships of the separate TAGs by the UE. Details will be provided in the following.
In an example communication system, there are several operating modes. In a cellular operating mode, communications to and from the plurality of UEs 120 go through the base station no. In device to device communications mode, such as proximity services (ProSe) operating mode, direct communication between UEs 120 is possible. As used herein, the term “base station” refers to any component (or collection of components) configured to provide wireless access to a network. Base stations may also be commonly referred to as Node Bs, evolved Node Bs (eNBs), next generation (NG) Node Bs (gNBs), master eNBs (MeNBs), secondary eNBs (SeNBs), master gNBs (MgNBs), secondary gNBs (SgNBs), network controllers, control nodes, access nodes, access points, transmission points (TPs), transmission-reception points (TRPs), cells, carriers, macro cells, femtocells, pico cells, relays, customer premises equipment (CPE), the network side, the network, and so on. In the present disclosure, the terms “base station” and “TRP” are used interchangeably unless otherwise specified. As used herein, the term “UE” refers to any component (or collection of components) capable of establishing a wireless connection with a base station. UEs may also be commonly referred to as mobile stations, mobile devices, mobiles, terminals, user terminals, users, subscribers, stations, communication devices, CPEs, relays, Integrated Access and Backhaul (JAB) relays, and the like. It is noted that when relaying is used (based on relays, picos, CPEs, and so on), especially multi-hop relaying, the boundary between a controller and a node controlled by the controller may become blurry, and a dual node (e.g., either the controller or the node controlled by the controller) deployment where a first node that provides configuration or control information to a second node is considered to be the controller. Likewise, the concept of UL and DL transmissions can be extended as well.
A cell may include one or more bandwidth parts (BWPs) for UL or DL allocated for a UE. Each BWP may have its own BWP-specific numerology and configuration, such as the BWP's bandwidth. It is noted that not all BWPs need to be active at the same time for the UE. A cell may correspond to one carrier, and in some cases, multiple carriers. In some cases, one cell (a primary cell (PCell) or a secondary cell (SCell), for example) is a component carrier (a primary component carrier (PCC) or a secondary CC (SCC), for example). For some cells, each cell may include multiple carriers in UL, one carrier is referred to as an UL carrier or non-supplementary UL (non-SUL, or simply UL) carrier which has an associated DL, and other carriers are called supplementary UL (SUL) carriers which do not have an associated DL. A cell, or a carrier, may be configured with slot or subframe formats comprised of DL and UL symbols, and that cell or carrier is seen as operating in a time division duplexed (TDD) mode. In general, for unpaired spectrum, the cells or carriers are in TDD mode, and for paired spectrum, the cells or carrier are in a frequency division duplexed (FDD) mode. A transmission time interval (TTI) generally corresponds to a subframe (e.g., in LTE) or a slot (e.g., in NR). Access nodes may provide wireless access in accordance with one or more wireless communication protocols, e.g., long term evolution (LTE), LTE advanced (LTE-A), 5G, 5G LTE, 5G NR, future 5G NR releases, 6G, High Speed Packet Access (HSPA), Wi-Fi 802.11a/b/g/n/ac, etc. While it is understood that communication systems may employ multiple access nodes (or base stations) capable of communicating with a number of UEs, only one access node, and two UEs are illustrated in
Uplink timing may be controlled through timing advance (TA). TA is generally used to compensate for the propagation delay as signal travels between UEs and their serving network nodes, e.g., TRPs. Uplink timing of a UE may be measured by a TRP using an uplink signal or channel, e.g., PUSCH, PUCCH, PRACH or SRS, transmitted by the UE. A TA value may be determined and assigned to the UE based on the measurement. Timing advance commands may be transmitted, e.g., periodically, by the TRP, generally in a medium access control (MAC) command entity (CE). A timing advance command may include a TA value, based on which UE adjusts its uplink transmission timing to align with the timing at the network side. With proper TA values applied to UL transmissions from UEs in a cell, the UL transmissions of the UEs arrive at the base station at about the same time to facilitate detection and/or decoding of the UL transmissions from the multiple UEs.
Cells are grouped into different timing advance groups (TAGs). Cells having an uplink to which the same TA applies (e.g., cells hosted by the same transceiver) and using the same timing reference cell may be grouped in one TAG. Thus, cells grouped in the same TAG have the same TA. A cell may be assigned to a TAG via radio resource control (RRC) signaling. Thus, a cell is associated with a TAG. Each TAG may update its corresponding TA periodically. When receiving a TA command of a cell associate with a TAG, a UE adjusts its uplink transmission timing, e.g., for transmission of PUCCH, PUSCH, and/or SRS of the cell based on the received TA command of the associated TAG.
In 3GPP 5G NR Release 15 and 16 (R15/16), TAGs are cell based. In one carrier, there is only one serving cell, which is assigned with one TAG. In 3GPP R16, for M-TRP communications, a TRP not configured as a serving cell (e.g., the TRP1214) is configured with the same TAG of its co-channel cell (e.g., the TRP0212). Serving cell (PCell and/or SCell) is configured, in its IE ServingCellConfig, with a field tag-Id, which uniquely identifies a TAG. For all serving cells configured with the same tag-Id, they belong to the same TAG. The current framework of TA/TAG allows only a serving cell to be configured with a TA/TAG. In one carrier, there can be only one serving cell, and that cell is assigned with one TAG. With Rel-16 M-TRP design, for a TRP not co-located with a serving cell, Rel-16 does not have a separate TA for it and the UE applies the TA of the co-channel serving cell for this TRP. This works fine even for M-TRP scenarios provided that the multiple TRPs are not located far away from one another, are connected by fast backhaul, and are tightly synchronized. However, this has limited applications/deployment scenarios and needs to be enhanced.
When a UE is served by multiple TRPs in a serving cell associated with a TAG in a BWP over a carrier, the UE's uplink transmission timing for all the multiple TRPs in the BWP over the carrier is adjusted using the same TA of the TAG associated with the serving cell. Note that the multiple TRPs over the same carrier operate on the same BWP as specified in Rel-16. Using the same TA of a serving cell for communication with different TRPs may, in some cases, cause inaccurate uplink timing (uplink TA). This may negatively affect the UE's PUCCH/PUSCH reliability, spectrum efficiency, and sounding accuracy for uplink/downlink full multi-input multi-output (MIMO) channel state information (CSI) acquisition. Cyclic prefix (CP) may not be sufficient to cover the propagation delay differences, delay spread, and M-TRP sync inaccuracy.
Likewise, DL timing difference between the M-TRPs (especially inter-cell TRPs) may cause the CP or one FFT insufficient. How well the time/frequency synchronization between the M-TRPs may depend on the backhaul assumption. If ideal backhaul can be assumed, then likely the timing/frequency differences between the TRPs are negligible. Otherwise, non-negligible synchronization errors should be considered in the design. Regarding backhaul latency and coordination, generally, at least for inter-cell TRPs, ideal/fast backhaul cannot be assumed. Backhaul latency of a few milliseconds to a couple of tens of milliseconds and semi-static coordination should be considered in the design. Inter-TRP signal delay spread relative to the CP length should also be considered. Depending on the synchronization among the inter-cell TRPs and the relative distances of the TRPs to the UE, the possible assumptions are: The inter-cell signal delay spread is within the CP length but close to the CP length. Even though the inter-TRP signal delay spread is within the CP length, the arrive time difference from the TRPs may still be large.
A TRP1214 is located in the coverage area of the serving cell 210 (with a certain distance from the TRP0212) and configured to cooperate with the TRP0212 to serve UEs in the serving cell 210 over the carrier, i.e., providing multi-TRP (m-TRP, or M-TRP) communications over the carrier. The TRP1214 is within the coverage range of the serving cell 210, assisting the serving cell 210, and not broadcasting the PCID/SSB for the cell 210, and may rely on the serving cell 210 for some functionalities (e.g., control plane functionalities), and thus it is considered as an intra-cell TRP of the cell 210. The TRP1214 may be referred to as an intra-cell TRP of the cell 210 and co-channeled (i.e., serving over the same carrier) with the TRP0212. The TRP1214 may not be co-located with the cell 210 and does not broadcast any PCID or SSB. However, in some deployment, e.g., at frequency range 2 (FR2), the TRP1214 may also broadcast the same PCID as the TRP0212 does, and transmit a SSB as a reference for timing/beam (e.g., the SSB can be used by a UE for timing synchronization and initial beam acquisition for communication with the TRP1214) but on a different SSB resource than the SSB transmitted by the TRP0212.
The wireless network 200 also includes a TRPn 222 associated with a cell 220, which may be a neighbor cell of the serving cell 210. As a neighbor cell instead of a serving cell, the TRPn 222 generally does not serve UEs that are served by the cell 210, but may cause interference to the UEs served by cell 210, and it is not configured as a serving cell for the UEs served by the cell 210. This is different from a serving cell transmitting RRC/MAC/PHY layer signals to a UE and maintaining a connection to the UE. TRPs 224 and 226 are located in the coverage area of the cell 220 and configured to cooperate with the TRPn 222 to serve UEs of the cell 220 over one or more carriers supported by the TRPn 222. The UE 202 may be served by both the TRP0212 and TRP1214 over the same carrier, or over different carriers. Each of the cells 210 and 220 has an associated physical cell identifier (PCID, or PCI) and a synchronization signal block (SSB), based on which UEs synchronize with the respective cell.
As used herein, a TRP being co-located with another TRP (or base station, or cell) indicates that the two TRPs are at the same location and share the same set of antennas, and may, in some cases, even share the same antenna configuration (e.g., the same analog antenna beamforming). A co-located relation between two TRPs may be known to the network side but not be revealed to a UE, i.e., transparent to the UE. In some cases, it may be useful for the UE to know whether two received signals are from the same transmitter (or TRP, or antenna) or not, and QCL assumptions between RS ports of the transmitters may be introduced and signaled to the UE. A TRP being co-channeled with another TRP (or base station, or cell) indicates that they operate on the same carrier in frequency. A standalone TRP transmits a SSB/PCID of a cell (the signal on the SSB is generated based on the PCID), and thus a UE can find it during a cell search/initial access procedure. The UE connects to the standalone TRP/cell after that. A non-standalone TRP does not transmit a SSB/PCID, and thus a UE cannot find it during a cell search/initial access procedure. The UE cannot connect to the non-standalone TRP directly. Instead, the UE first connects to a standalone TRP/cell, and then the standalone TRP/cell signals the UE with information about the non-standalone TRP, so that the UE may communicate with the non-standalone TRP.
In this example, the cell 210 is assigned to TAG0 associated with the carrier. The UE 202 may have established a connection with the cell 210 through a random access procedure, and receives a TA command of the TAG0 from the TRP0212. The TA value in the TA command is generally related to the distance between the TRP0212 and the UE 202. The UE 202 then transmits uplink signals/channels over the carrier to both the TRP0212 and TRP1214 according the TA command, i.e., the same TA value, if they are in the same TAG as in Rel-16, i.e., if they are configured with the same TAG according to Rel-16. However, in a case where the TRP0212 and TRP1214 are located far away from each other, e.g., with a distance greater than 300 m, with non-ideal backhaul (e.g., with a backhaul latency of 10˜20 ms or even longer, which may cause them not tightly synchronized with each other) between the TRPs 212 and 214, and the UE 202 is closer to the TRP1214 (e.g., with nearly no propagation delay) than to the TRP0212 (e.g., with a greater than 1 us propagation delay), uplink timing error may occur when the UE 202 communicates with the TRP1214 using the TA value of the TAG0, which is assigned based on the TRP0212. This is because the TA of the TAG0 is not well suited for TRP1214 in view of the distance between the TRP1214 and the TRP0212, between the TRP1214 and the UE 202, and between the TRP0212 and the UE 202. In this case, there is a large propagation delay difference between the TRP1214 and the UE 202, and between the TRP0212 and the UE 202. Cyclic prefix (CP) may help mitigate the propagation delay difference to some extent, however, for higher subcarrier spacing (SCS), e.g., greater than 15 kHz, CP is short as shown in the table 230 in
In some cases, the network may also configure the TRPn 222 to serve the UE 202 over the same carrier, without configuring it as a secondary cell (SCell) of the UE 202, e.g., in order to provide increased network capacity. The TRPn 222 is an inter-cell TRP, as opposed to an intra-cell TRP. However, the TRPn 222 may be transparent to the UE 202. In this case, with Rel-16 design, the UE 202 may still use the TA of the TAG0 for uplink transmission to the TRPn 222, and the FFT window acquired from TRP0212's RS/SSB for DL reception with the TRPn 222. However, if the TRPn 222 is located far away from the TRP0212, e.g., greater than 500 meters, and/or if the timing of the TRPn 222 is not tightly synchronized to the TRP0212, timing error occurs because the timing based on the TRP0212 is not well suited for TRPn 222 in view of the distance/timing differences between the TRPn 222 and the TRP0212, and between the TRPn 222 and the UE 202. It would also be desirous to configure a separate TAG, DL timing, and RG for the UE 202 to communicate with the TRPn 222 over the carrier. By doing so, more TRPs, including inter-cell TRPs, can be added to the serving TRP pool for the UE 202 and well utilized by the UE 202.
Some embodiments of the present disclosure provide example methods for M-TRP communications of a UE in a serving cell over the same carrier/BWP of the serving cell, with separate RGs configured for multiple TRPs in the M-TRP communications. The example methods provide a solution to the problem discussed above with respect to
In some embodiments, in one carrier, there is one serving cell, but there are multiple TAGs, RGs, SSBs, and/or PCIDs configured for a UE. A serving TRP of the UE, e.g., TRP0212, may be associated with a TAG (or a co-channel TAG, e.g., TAG0) and a RG (or a co-channel RG, e.g., RG0), e.g., using RRC signaling as conventionally configured, if it is associated with the serving cell 210 of the UE, as discussed above. In what follows, a TA may be seen as a (an optional) parameter associated with a RG, so only RGs are described which also apply to TAG (unless otherwise specified). In an embodiment, a group of UL signals/channels form a UL RG and a group of DL signals/channels form a DL RG, i.e., the RGs are separate for UL and DL. In an embodiment, a group of UL/DL signals/channels form a RG, i.e., no separate RGs for UL and DL. In an embodiment, one UL RG is associated with one DL RG and vice versa. In an embodiment, one UL RG is associated with multiple DL RGs. In an embodiment, one DL RG is associated with multiple UL RGs. In an embodiment, a separate TAG is not configured but a separate RG is configured, and each RG is associated with a TA, which is an alternative approach to configure a separate TAG. In an embodiment, a separate TAG is not configured but a separate UL RG is configured, and each UL RG is associated with a TA. In an embodiment, a separate TAG is configured in parallel to a separate RG, and each TAG is associated with a RG. An intra-cell or inter-cell serving TRP not configured as a serving cell or not co-located with a serving cell of the UE, e.g., TRP1214, or TRPn 222, may be associated with a separate RG. For a serving TRP not transmitting a SSB, e.g., the TRP1214, a tracking reference signal (TRS), also referred to as a channel state information-reference signal (CSI-RS) for tracking, of such a serving TRP may be used to form a separate RG, even when there is already a co-channel RG associated with the serving cell, e.g., the cell 210. Uplink/DL signals of the UE that is quasi-co-located (QCLed) to the TRS are associated with the separate RG. Thus, the TRS may be used to form the separate RG. The TRP0212 may operate on more than one carrier, and the carriers not far away from each other in the frequency domain may belong to the same RG, i.e., RG0. TRP1214 may also operate on more than one carrier, each of which is co-channelled with one carrier on the TRP0212, and each of which has a TRS transmitted. All uplink/DL signals of the UE that is quasi co-located (QCLed) to these TRSs of the TRP1214 are associated with the separate RG. In general, TRSs transmitted from the same/co-located TRP on a same frequency band can be used to define a RG, and TRSs transmitted from non-co-located TRPs may be associated with different RGs. TRP/TRS-specific scrambling ID(s) may be needed for PUSCH and for demodulation reference signal (DMRS) of PUSCH communicated during the random access procedure, as well as TRP/TRS-specific scrambling ID(s) for DMRS of PDSCH, TRP/TRS-specific scrambling ID(s) for physical downlink shared channel (PDSCH), TRP/TRS-specific scrambling ID(s) for DMRS of physical downlink control channel (PDCCH), and TRP/TRS-specific scrambling ID(s) for PDCCH.
The quasi co-location (QCL) types corresponding to each DL RS (more specifically, the port(s) or antenna port(s) of the DL RS) are given by the higher layer parameter qcl-Type in QCL-Info and may take one of the following values: 1) ‘QCL-TypeA’: {Doppler shift, Doppler spread, average delay, delay spread}; 2) ‘QCL-TypeB’: {Doppler shift, Doppler spread}; 3) ‘QCL-TypeC’: {Doppler shift, average delay}; and 4) ‘QCL-TypeD’: {Spatial Rx parameter}. The QCL types may be configured/indicated in transmission configuration indication (TCI) states for a RS. The QCL assumptions are mainly used for DL RS, but can be generalized for UL RS if the association via pathloss RS and spatial relation are specified. The QCL assumption may be specified as: {RS1: QCL Type C to RS2}, {RS1: QCL Type C to RS2 and QCL Type D to RS3}. Then RS1 (destination RS) derives the properties specified according to the QCL types from the associated (i.e., source) RSs (e.g., RS2). Note that the source RS may be a SSB. Note also that the source RS and destination RS may be on the same carrier or different carriers (i.e., cross-carrier QCL).
For an inter-cell serving TRP, e.g., TRPn 222, a SSB of the inter-cell serving TRP may be configured to the UE but not as a SCell of the UE (i.e., the cell associated with the SSB of the inter-cell serving TRP is not one of the serving cells of the UE). A TRS of the inter-cell serving TRP may be used to form a separate RG, even when there is already a co-channel RG associated with the serving cell, e.g., the cell 210. TRP-specific scrambling ID(s) may be needed for PUSCH and for DMRS of PUSCH communicated during the random access procedure, as well as TRP/TRS-specific scrambling ID(s) for DMRS of PDSCH, TRP/TRS-specific scrambling ID(s) for PDSCH, TRP/TRS-specific scrambling ID(s) for DMRS of PDCCH, and TRP/TRS-specific scrambling ID(s) for PDCCH.
A PDCCH may be used to indicate, via an ID or quasi co-location (QCL) relation and/or a default relation, which serving TRP, e.g., the TRP1214 or the TRPn 222, that a UE needs to receive a PDSCH from or transmit a PUSCH to. Each TRP may be associated with an ID, such as a control resource set (CORESET) pool ID, so that, for example, a PDCCH received on a CORESET with a CORESET pool ID 0 indicates a PUSCH transmission to a TRP associated with the ID 0. In another example, a PDCCH received with a QCL relation/TCI state linking to a SSB or a TRS indicates a PUSCH transmission to a TRP associated with that SSB or TRS.
Taking
The UE 202 may receive scheduling information scheduling uplink transmission of the UE with a TRP on a carrier according to a RG associated with the TRP. In some embodiments, the UE 202 may receive first configuration information of the carrier of the serving cell 210 via a RRC configuration signaling. The first configuration information may include/indicate an association between a first group of uplink signals and channels to be transmitted on the carrier by the UE in the serving cell 210 and the RG0, and the RG0 is associated with a first TA value. That is, the first configuration information of the carrier indicates that transmission of the first group of uplink signals and channels by the UE is according to the first TA value of the RG0. The first configuration information may be transmitted by the TRP0212 to the UE 202. The UE 202 may also receive second configuration information of the carrier, which includes/indicates an association between a second group of uplink signals and channels to be transmitted on the carrier by the UE and the uplink RG1, and the RG1 is associated with a second TA value. That is, the second configuration information of the carrier indicates that transmission of the second group of uplink signals and channels by the UE is according to the second TA value of the RG1. The second configuration information may be transmitted by the TRP0212 or the TRP1214 to the UE 202. Similarly, the UE 202 may also receive third configuration information of the carrier, which includes/indicates an association of a third group of uplink signals and channels on the carrier with the uplink RG2, and the RG2 is associated with a third TA value. That is, the third configuration information of the carrier indicates that transmission of the third group of uplink signals and channels by the UE is according to the third TA value of the RG2. The third configuration information may be transmitted by the TRP0212 or the TRPn 222 to the UE 202. The first, second, and third configuration information of the carrier may be transmitted by the TRP0212 in one message or separate messages. The UE 202 may then transmit, to the TRP0212, a UL signal or a UL channel in the first group of UL signals and channels according to the first TA value. The UE 202 may transmit, to the TRP1214, a UL signal or a UL channel in the second group of UL signals and channels according to the second TA value. The UE 202 may transmit, to the TRPn 222, a UL signal or a UL channel in the third group of UL signals and channels according to the third TA value. The first, second and third groups of UL signals and channels may be configured with a same subcarrier spacing (SCS) within a same BWP. Both the second and the third groups may be configured, or only one of the groups may be configured.
The serving cell 210 is associated with a first PCID and a first SSB. A UL signal or channel in the first group of UL signals and channels may be quasi-co-located (QCLed) to the first SSB, or QCLed to a downlink/uplink reference signal that is QCLed to the first SSB, or is configured with a pathloss RS that is the first SSB or is QCLed to the first SSB, or is configured with a spatial relation RS that is the first SSB or is QCLed to the first SSB. In an embodiment, all UL signal or channel in the first group of UL signals and channels are associated with the first RG.
A UL signal or channel in the second group of UL signals and channels may be QCLed to a TRS of the TRP1214, or to a downlink/uplink reference signal that is QCLed to the TRS of the TRP1214, or is configured with a pathloss RS that is the TRS or is QCLed to the TRS of the TRP1214. In an embodiment, all UL signal or channel in the second group of UL signals and channels are associated with the second TAG. In an embodiment of network deployment, a TRS of the TRP1214 may be “approximately” QCLed to the first SSB of the serving cell or a TRS of the first SSB, even though the TRP1214 is not co-located with the TRP0212 broadcasting the first SSB/PCID, which generally requires that the TRPs are not far away from each other, operate in frequency range 1 (FR1), and serve UEs that do not have high mobility. Still a separate TAG from the TAG for the first SSB/PCID may be beneficial. In an embodiment of network deployment, the TRP1214 may broadcast the first PCID on a SSB resource different from the first SSB transmitted by TRP0212, even though the TRP1214 is not co-located with the TRP broadcasting the first SSB/PCID. A separate RG from the RG for the first SSB/PCID may be configured for the TRP1214. The SSBs associated with the same PCID but occupy different SSB resources within one SSB burst in FR2 are distinguished via SSB index, and hence each SSB index may be used to define a separate RG if the SSBs with different SSB indexes are transmitted from non-co-located TRPs.
A UL signal or channel in the third group of UL signals and channels may be QCLed to a TRS of the TRPn 222, QCLed to a second SSB associated with a neighbor cell that has a second PCID different than the first PCID, e.g., the cell 220, or QCLed to a PCID of a cell other than serving cells of the UE 202, or QCLed to a downlink/uplink reference signal that is QCLed to the TRS of the TRPn 222 or the second SSB, or configured with a pathloss RS that is the TRS of the TRPn 222 or the second SSB, or that is QCLed to the TRS of the TRPn 222 or the second SSB. In an embodiment, all UL signal or channel in the third group of UL signals and channels are associated with the third RG.
As discussed above, the example methods associate serving TRPs, which are QCLed to a non-serving cell's SSB directly/indirectly, or which are not QCLed to a serving cell's SSB, or not co-located with a serving cell's TRP(s) transmitting the serving cell's SSB, with RGs separate from the serving cell's TAG, and a UE also needs to perform random access with the serving TRPs to obtain separate TAs. As used herein, a first RS may be QCLed to a second RS/SSB directly, for example, the UE is signaled with a QCL assumption for the first RS that refers to the second RS/SSB for a QCL type, e.g., the UE receives a QCL assumption indicating {the first RS: QCL Type C to the second RS}. A first RS may be QCLed to a second RS/SSB indirectly, for example, the UE is signaled with a QCL assumption for the first RS that refers to one or more RS/SSB, which are further referred to the second RS/SSB for QCL, via one or more QCL assumptions in a concatenated manner, e.g., the UE receives a QCL assumption indicating {the first RS: QCL Type C to a third RS}, {the third RS: QCL Type A to a fourth RS}, and {the fourth RS: QCL Type C to the second RS}. In other words, one QCL assumption defines a relationship/link between a source RS and a destination RS, and multiple QCL assumptions may define a chain of relationships/links that associate a RS, directly using one link or indirectly using multiple links, to another RS/SSB.
For example, a PDCCH DMRS may be configured/indicated as QCLed to the first SSB of the serving cell or a TRS of the non-serving cell, and an ID is configured for the PDCCH DMRS. Then the UE may receive the PDCCH DMRS with the configured ID, and the DMRS and ID are associated with the TRP of the non-serving cell. The QCL assumptions/relations associate or link all the involved RS, the channels associated with the RS, and IDs associated with the RS/channels, to the QCLed SSB (directly or indirectly via other UL/DL RS), and serve as an implicit way to group the signals/channels/IDs separately according to the TRPs into RGs.
A UE may receive a physical downlink control channel (PDCCH). The PDCCH may be associated with a control resource set (CORESET) with a first CORESET pool index, or has a DMRS that is configured to be QCLed to a SSB or a TRS QCLed to the SSB. The DL RS may be QCLed to the SSB, may be the SSB, or may be a CSI-RS QCLed to the SSB or the TRS, or may be a TRS QCLed to the SSB. If the SSB or TRS is associated with a serving cell of the UE, e.g., the cell 210 in
In some embodiments, the UE receives DL transmissions in an M-TRP deployment scenario. As noted above, many of the UL related operations depend on DL operations. The following deployment scenario related assumptions are considered. DL timing difference between the M-TRPs (especially inter-cell TRPs) may cause the CP or one FFT insufficient. How well the time/frequency synchronization between the M-TRPs is may depend on the backhaul assumption. If ideal backhaul can be assumed, then likely the timing/frequency differences between the TRPs are negligible. Otherwise, non-negligible synchronization errors should be considered in the design. Regarding backhaul latency and coordination, generally, at least for inter-cell TRPs, ideal/fast backhaul cannot be assumed. Backhaul latency of a few milliseconds to a couple of tens of milliseconds and semi-static coordination should be considered in the design. Inter-TRP signal delay spread relative to the CP length should also be considered. Depending on the synchronization among the inter-cell TRPs and the relative distances of the TRPs to the UE, the possible assumptions are: 1) The inter-cell signal delay spread is within the CP length but close to the CP length, i.e., even though the inter-TRP signal delay spread is within the CP length, the arrive time difference from the TRPs may still be large. The UE may still need to have the capability of supporting multiple tracking loops and FFT windows in DL in order to improve its signal reception performance. 2) The inter-cell signal delay spread is longer than the CP length, then multiple tracking loops and FFT windows are needed in this case. In some embodiments, multiple tracking loops and FFT windows are used on the same carrier on the same OFDM symbol for a UE to receive PDSCH/PDCCH from multi-TRPs. The standards may specify UE assumptions/behavior under multiple QCL/TCI states so that the UE can correctly use the tracking loop and FFT window to receive a PDCCH/PDSCH. The UE may maintain multiple FFT windows (i.e., DL fine timing synchronization), and apply the FFT windows on the same carrier on the same OFDM symbol based on the multiple TCI states for DL receptions from multiple TRPs, in which a first fine timing/first FFT window is associated with a first TCI state, a first PDCCH/PDSCH, and a first TRP, and a second fine timing/first FFT window is associated with a second TCI state, a second PDCCH/PDSCH, and a second TRP. On the other hand, only the minimum UE assumptions may be specified, such as “the UE assumes multiple QCL assumptions that respectively link to multiple SSBs (directly or indirectly through one or more RS) on the same carrier on the same OFDM symbol based on the multiple TCI states for DL receptions” or “the UE shall have capability to receive simultaneously transmissions associated with more than one RG, wherein each RG may be associated with a DL time and frequency synchronization”. Note that in the prior art, on the same time-frequency resources the QCL assumptions link to at most one SSB directly/indirectly, but here the QCL assumptions link to more than one SSB directly/indirectly to support more general M-TRP operations. The UE can link PDSCH/PDCCH as well as other transmissions/receptions to the inter-cell TRP via the QCL relation linking to the non-serving SSB, and hence the CORESET pool indexes may not need to be explicitly configured in this case. A CORESET configured with TCI state(s) including QCL to the serving SSB directly or indirectly is for the TRP associated with the serving SSB, i.e., effectively assigned with CORESETPoolIndex 0, and a CORESET configured with TCI state(s) including QCL to the non-serving SSB directly or indirectly is for the TRP associated with the non-serving SSB, i.e., effectively assigned with CORESETPoolIndex 1. In an embodiment, the CORESETPoolIndex is used to identify each RG. The UE does not expect a CORESET configured with TCI state(s) including QCL to both the serving SSB and the non-serving SSB, directly or indirectly. To support reception with multiple tracking loops and FFT windows, the UE needs to have the capability to receive inter-cell multi-TRP with delay spread comparable or longer than the CP length, which may require some duplicated hardware. This is in parallel to UL transmissions with the new UE behavior and capability to acquire, maintain, and apply multiple TAs. These capabilities are generally similar to UE CA capability but the aggregation of additional radio resources are on the same carrier, and can be used jointly with CA capabilities, i.e., a UE may support 5 component carriers (CCs), and on each CC it may support 2 TRPs, then the UE needs to have the capability to aggregate 10 PDSCH transmissions simultaneously. All DL signals/channels (PDSCH/PDCCH/DMRS/CSI-RS/CSI-IM/PTRS/etc.) should be QCLed to a TRS/SSB directly or indirectly, and similarly, all UL signals/channels (PUCCH/PUSCH/SRS/DMRS/PTRS/PRACH) should also be QCLed (or via spatial relation, via pathloss RS relation, etc.) to a TRS/SSB and belong to the TAG associated with that TRS/SSB.
The UE 504 may receive a TRS1 or SSB1 from the TRP1506, and also receive configuration information of a separate RG from the TRP1506 (step 518). The SSB1 may be transmitted on the carrier or on a different carrier (similar to the above scellWithoutSSB description for the TRP0502), and the TRS1 may be transmitted on the carrier or on a different carrier (similar to the above description for the TRP1506 without transmitting a TRS on the carrier), and other signals/channels may be QCLed to the SSB1 and/or TRS1.
The UE 504 may monitor CSI-RSs (CSI-RS1) with a CSI-RS ID (CSI-RS ID1) from the TRP1506. The CSI-RS1 may be scrambled using the CSI-RS ID1. The UE 504 receives a PDCCH order (DCI1 PDCCH order) associated with a CORESET pool (Coreset pool 1) (step 520). The PDCCH may have an associated DMRS and indicate a PDSCH with an associated DMRS, which are transmitted based on the Coreset pool 1 and using a scrambling ID1 of the TR 506 (scramblingID1). PUSCH may have an associated DMRS. At step 522, the PUSCH is scrambled using a PUSCH scrambling ID (PUSCH scramblingID1), and the DMRS is scrambled using a PUSCH DMRS scrambling ID (PUSCH DMRS scramblingID1). At step 524, the UE 504 may transmit to the TR1506, one or more PUCCHs (scrambled using the PUCCH scramblingID1), PUSCHs (scrambled using the PUSCH scramblingID1) with associated DMRS (scrambled using the PUSCH DMRS scramblingID1), and/or SRS (scrambled using a SRS ID1). In general, the RG0 parameters (e.g., IDs, timings) and RSs (e.g., TRS, CSI-RS, DMRS) and channels (e.g., PDSCH, PUSCH, etc.) are used to communicate with TRP0502, and the RG1 parameters (e.g., IDs, timings) and RSs (e.g., TRS, CSI-RS, DMRS) and channels (e.g., PDSCH, PUSCH, etc.) are used to communicate with TRP1506.
The PUSCH scramblingID may be called dataScramblingIdentityPUSCH, and for the M-TRPs they may be called dataScramblingIdentityPUSCH and dataScramblingIdentityPUSCH2 (or AdditionaldataScramblingIdentityPUSCH). In addition, if a higher layer signaling index per CORESET is configured such as CORESETPoolIndex is configured, dataScramblingIdentityPUSCH is associated with a higher layer signaling index per CORESET and is applied to the PUSCH scheduled with a DCI detected on a CORESET with the same higher layer index, e.g., dataScramblingIdentityPUSCH is associated with CORESETPoolIndex being o (or no explicit index), and AdditionaldataScramblingIdentityPUSCH is associated with CORESETPoolIndex being 1. The DMRS for the PUSCH may be done likewise, which generally have another set of scrambling identities and now need to be increased for M-TRP PUSCH DMRS.
Table 1 below shows numbers of PCID per carrier, for existing 3GPP standards (Releases) and new embodiments. For all existing configurations, at most 1 PCID/RG/TAG configuration can be allowed for a carrier, even if multiple TRPs may be on the carrier. With the embodiment designs, more than 1 PCID/RG/TAG configuration may be allowed for a carrier.
Different from the scenario 1 of
DMRS (e.g., DMRS 820) is used for modulation/demodulation of the DCI0812 and the PDSCH0814. The DMRS 820 may be QCLed to a TRS 822 of the TRP0802. The TRS 822 of the TRP0802 may be QCLed to a SSB 824 associated with the serving cell (the TRP0802). A CSI-RS 826 of the TRP0802 may be QCLed to the SSB 824. DMRS (e.g., DMRS 828) is used for modulation/demodulation of the DCI1816 and the PDSCH1818 of the TRP1806. The DMRS 828 may be QCLed to a TRS 830 of the TRP1806. The TRP1806 not configured as a serving cell of the UE 804 does not have an associated SSB. The TRP1806 may send CSI-RS 832 to the UE 804, base on which the UE 804 may estimate PL between the UE 804 and the TRP1806, and send a RACH preamble (e.g., non-contention based) in a random access procedure to the TRP1806 based on the estimated PL. The CSI-RS 832 may be QCLed to the TRS 830. In this example, the PL is based on the CSI-RS of the TRP1806, and the RACH to the TRP1806 is based on the PL. However, other steps of the random access procedure are performed between the UE 804 and the TRP0802 based on the TRP0802 and a PCID associated with the SSB 824 (this is similar to what is specified in R16). In an embodiment, the TRS 830 is not QCLed to SSB 824 or TRS 822, but the UE 804 needs to search the TRS 830 similar to a discovery signal (DS) within a search time window.
Each of the TRP01002 and the TRP11006 may send a PDCCH order instructing the UE 1004 to initiate a random access procedure. In this example, a PDCCH order is linked to a TRP. That is, The PDCCH order itself implies that the UE 1004 initiate a random access procedure to the TRP linked with the PDCCH order. The TRP01002 and the TRP11006 transmit their respective DCI scheduling their respective PDSCHs. For example, as shown, the TRP01002 transmits DCI (e.g., DCI01012) to the UE 1004 scheduling a PDSCH (e.g., PDSCH01014) from the TRP01002. The TRP11006 transmits DCI (e.g., DCI11016) to the UE 1004 scheduling a PDSCH (e.g., PDSCH11018) from the TRP11006. In this example, both the TRP01002 sends DCI to the UE 1004 (i.e., M-DCI). DMRS (e.g., DMRS 1020) is used for modulation/demodulation of the DCI01012 and the PDSCH01014. The DMRS 1020 may be QCLed to a TRS 1022 of the TRP01002. The TRS 1022 of the TRP01002 may be QCLed to the SSB 1024 associated with the serving cell (the TRP01002). A CSI-RS 1026 may be QCLed to the SSB 1024. DMRS (e.g., DMRS 1028) is used for modulation/demodulation of the DCI11016 and the PDSCH11018 of the TRP11006. The DMRS 1028 may be QCLed to a TRS 1030 of the TRP11006. The TRS 1030 of the TRP11006 may be QCLed to the SSB 1032 associated with the TRP11006.
The SSB 1032 may be configured to associate with the TAG1, but not configured as a SCell of the UE 1004. The TRS 1030 may be QCLed to the SSB 1032. The TRP11006 may send a CSI-RS 1034 to the UE 1004, base on which the UE 1004 may estimate PL between the UE 1004 and the TRP11006, and send a RACH preamble (e.g., non-contention based) in a random access procedure to the TRP11006 based on the estimated PL. The CSI-RS 1034 may be QCLed to the TRS 1030 or the SSB 1032. In this example, the PL is based on the CSI-RS of the TRP11006, and the RACH to the TRP11006 is based on the PL. However, other steps of the random access procedure (e.g., RAR) are performed between the UE 1004 and the TRP01002 based on the TRP01002 and a PCID associated with the SSB 1024 (this is similar to what is specified in R16). The scrambling IDs used with TRP11006 may be based on the associated non-serving SSB 1032, or may be configured for one or more of signals/channels for transmissions with the TRP11006.
In some embodiments, examples of M-TRP PUCCH enhancement are described. In URLLC, to meet 1E-5 BLER requirement for data transmission, PUCCH reliability needs to be at least the same or better (i.e., lower) than 1E-5 BLER, preferably an order of magnitude better. In Rel-16, separate and/or joint A/N feedback in PUCCH is supported. For separate A/N, TDMed long and/or short PUCCH is supported, and each PUCCH resource may be associated with a higher layer index per CORESET. For joint A/N, joint semi-static HARQ-ACK codebook can be used and A/N bits are concatenated in a certain order. Switching between separate and joint A/N feedback is supported via RRC configuration. In one embodiment, above enhancement of PUCCH with ACK/NACK to PUCCH with CSI is extended, including: 1) Allow separate and/or joint CSI feedback in PUCCH; 2) Distinguish URLLC-oriented CSI reporting vs non-URLLC-oriented CSI reporting, in terms the contents, format, repetition, collision handling, etc., an explicit bit may be used to signal the UE that a CSI is associated with higher priority so other transmission is dropped when colliding with the PUCCH carrying the CSI with higher priority; 3) TDM of M-TRP PUCCH, and PUCCH repetition in time domain (UE transmitting the same PUCCH multiple times to the same TRP) and spatial domain (UE transmitting the same PUCCH multiple times to multiple TRPs, respectively). In one embodiment, one PDCCH/PDSCH transmission followed by multiple (i.e., repetition) PUCCH A/N feedback can be allowed. The UE may perform repeated A/N transmissions to one of the TRPs or both TRPs. This may be useful if the reliability of ACK/NACK feedback cannot reach the target BLER. In one embodiment, soft combining/joint reception at the network side can be allowed. Whether it is feasible to perform soft combining/joint reception by multiple TRPs may depend on backhaul assumptions between the TRPs. However, for the same TRP, soft combining of repeated PUCCH transmission is always feasible.
In some embodiments, examples of M-TRP PUSCH enhancement are described. In an embodiment, TDM of M-TRP PUSCH is supported. PUSCH repetition in time domain (repeated for the same TRP) and spatial domain (repeated for multiple TRPs) can be supported. The repetition should be for same TB, but the same or different RVs may be used for the multiple PUSCHs. In an embodiment, single-DCI and multi-DCI to schedule PUSCH are supported, similar to single-DCI and multi-DCI to schedule PDSCH. In an embodiment, the network and UE distinguish URLLC-oriented PUSCH vs non-URLLC-oriented PUSCH, in terms of the contents, format, repetition, collision handling, etc. An explicit bit may be used to signal the UE that a PUSCH is associated with higher priority so other transmission is dropped when colliding with the PUSCH with higher priority. The PUSCH may carry URLLC UL data, URLLC related A/N feedback, and/or URLLC related CSI report.
In some embodiments, examples of M-TRP PDCCH enhancement are described. In an embodiment, PDCCH repetition in time domain (repeated by the same TRP) and spatial domain (repeated by multiple TRPs) are supported. For example, DCI1 may be sent from TRP1, and DCI1 could be an S-DCI to schedule PUSCHs/PDSCHs jointly for TRP1 and TRP2, or one of the M-DCIs to schedule PUSCH/PDSCH only for TRP1. DCI1 may be repeated in a later OFDM symbol, sent by TRP1, TRP2, or even both. The PDCCH repetition can be useful for higher reliability. However, one issue needs to be resolved. When the UE receives multiple PDCCH transmissions, each schedules a PDSCH (or a PUSCH). The UE may not understand that these PDCCH transmissions are actually the repetition and they should lead to only one PDSCH (or only one PUSCH). The UE may incorrectly assume it is scheduled for two PDSCH transmissions (or two PUSCH transmissions) at the same time and decide to drop one or both of the transmissions. This is an example showing that PDCCH repetitions have to be explicitly signaled to the UE. Otherwise, UE assumptions should be standardized so that the UE assumes PDCCH repetition based on identical resource allocation in the multiple DCIs. The explicit signaling may be a field in the DCI as a flag, and DCIs with the same flag are assumed to schedule the same PDSCH or PUSCH. Embodiments also include cross-TRP (TRP1 DCI to schedule TRP2 PDSCH/PUSCH or vice versa) scheduling, joint DCI (S-DCI to schedule for both TRPs) sent from either TRP, or joint transmission of the same DCI (for one or separate PDSCH/PUSCH transmissions in one or both TRPs). To support these enhancements, the QCL/TCI states and CORESET pool indexes should be enhanced to ensure that the transmissions are correctly associated with the intended TRP(s).
The DL operations under HST-SFN deployment scenario relies on Rel-16 eMIMO multi-TRP based URLLC Scheme 1c with a single DCI. The agreement regarding Scheme 1c is as follows:
To facilitate further down-selection for one or more schemes in RAN1 #96bis, schemes for multi-TRP based URLLC, scheduled by single DCI at least, are clarified as following:
Scheme 1 (SDM): n (n<=Ns) TCI states within the single slot, with overlapped time and frequency resource allocation
Scheme 1c: One transmission occasion is one layer of the same TB with one DMRS port associated with multiple TCI state indices, or one layer of the same TB with multiple DMRS ports associated with multiple TCI state indices one by one.
Based on Scheme 1c, the Rel-17 HST-SFN may operate according to the following manner:
Network Configuration
Multiple TRPs are connected with ideal backhaul with the same cell ID to serve UEs on HST.
SSB Configuration
In principle, some TRPs may not need to transmit SSB and transmission of TRP-specific TRS may be sufficient for data transmissions, but since the distances between the TRPs are usually a few hundred meters, it may be desirable to have all TRPs transmit SSBs to cover the entire range. So generally, each TRP can transmit a SSB associated with the common cell ID. The SSB may be the same for some or all TRPs (i.e., SFN for SSB) or TRP-specific SSBs; however, as the SSBs are transmitted directionally along the HST directions, i.e., with different beams, generally the SSBs should be TRP-specific SSBs.
TRS Configuration
There may be two options for TRS pre-compensation for Doppler shifts:
Option 1 TRS design: no or little pre-compensation for Doppler shifts, with TRP-specific TRS
For this option, the TRPs are synchronized, and they transmit in a synchronized fashion without pre-compensation for Doppler shifts. Then UE sees different Doppler shifts for different TRSs, i.e., the TRS are TRP-specific. Based on the TRS, a UE can estimate TRP-specific Doppler shift. Note that different TRPs have significantly different Doppler shifts for HST.
Each TRP-specific TRS can be QCLed (Type A, and for FR2, also Type D) to the corresponding TRP-specific SSB.
Option 2 TRS design: with pre-compensation for Doppler shifts, and SFN for TRS from different TRPs
For this option, the TRPs are synchronized, and they transmit in a synchronized fashion with sufficient pre-compensation for Doppler shifts. Then UE sees nearly the same Doppler shifts for different TRSs, and therefore the TRSs can form a SFN. Based on the TRS, a UE can estimate residual Doppler shift if needed.
The TRS can be QCLed to one or more of the SSBs.
PDSCH DMRS Configuration
Multiple TRPs transmit the same PDSCH (and possibly PDCCH) on the same time-frequency resources, forming a SFN essentially based on Scheme 1c.
Note that each TRP can transmit all layers (say L layers), i.e., all TRPs (say n TRPs) transmit all L layers of the same TB/codeword. This is a straightforward generalization of the one layer in Rel-16 Scheme 1c. Note also that the SFN is possible thanks to the ideal backhaul among the TRPs.
There are two options for the DMRS for PDSCH:
Option A: SFN DMRS port(s) for all TRPs
For this option, the UE receives L DMRS ports, and each DMRS port corresponds to a layer from all TRPs. In other words, each DMRS port is formed by the SFN of all TRPs. The DMRS port needs to be simultaneously QCLed to the TRSs:
Option A-1: SFN DMRS port(s) QCLed to TRP-specific TRS
The SFN DMRS needs to be associated with multiple TCI state indices, each TCI state index specifies a QCL relation to the TRP-specific TRS of a TRP. QCL type A (Doppler shift, Doppler spread, average delay, delay spread) should be specified in the TCI state.
An example of the QCL configuration for the DMRS port(s) is:
TCI state 1: QCL A, TRS 1 (for TRP 1)
TCI state 2: QCL A, TRS 2 (for TRP 2)
. . .
TCI state n: QCL A, TRS n (for TRP n)
Option A-2: SFN DMRS port(s) QCLed to SFN TRS
The SFN DMRS can be associated with one TCI state index, which specifies a QCL relation to the SFN TRS of TRPs. QCL type A (Doppler shift, Doppler spread, average delay, delay spread) should be specified in the TCI state.
An example of the QCL configuration for the DMRS port(s) is:
TCI state: QCL A, TRS (for all TRPs)
Option B: TRP-specific DMRS ports
For this option, the UE receives nxL DMRS ports. The nxL ports can form L sets, each set containing n ports associated with a same layer from the n TRPs. The nxL ports can also form n groups, each group containing L ports associated with a same TRP for the L layers (a group could be a CDM group). Likely the L ports for the same TRP can be a CDM group, but ports for different TRPs should be orthogonalized in time/frequency/sequence domain. This option works only with Option 1 TRS design with TRP-specific TRSs.
Note that though the WID does not list Option B as an example, it is not precluded.
An example of the QCL configuration for the DMRS ports is:
1st group of L DMRS ports: TCI state 1: QCL A, TRS 1 (for TRP 1)
2nd group of L DMRS ports: TCI state 2: QCL A, TRS 2 (for TRP 2)
. . .
nth group of L DMRS ports: TCI state n: QCL A, TRS n (for TRP n)
From the above description, the following issues may need to be addressed in Rel-17:
Decision on supporting TRS/DMRS options, e.g., Option A (Option A-1 and Option A-2) and/or Option B.
Option A has a lower DMRS overhead but the channel estimation on the DMRS with a composite channel from all TRPs may be more complicated and less accurate than Option B. Especially Option A-1 channel estimation may be challenging. The tradeoff should be studied in Rel-17 and an agreement is needed which one or both should be supported.
Specify UE Behavior/Assumption
For either options, UE assumption and minimum UE behavior (if any) need to be specified. For example, for Option A, the UE needs to assume the channel on a DMRS port is a composite channel, a superposition of individual channels associated with the TRSs. For Option B, the UE needs to assume the channel for PDSCH is a composite channel, a superposition of individual channels associated with the corresponding n DMRS ports.
In order for the network to apply Doppler shift pre-compensation value for each TRP before transmitting the SFN PDSCH, the UE may need to transmit SRS to each TRP, and the SRS may be based on the Doppler shift the UE experiences for that TRP in DL. This may require the UL signal and DL signal to be associated, e.g., with respect to the Doppler shift. This can be fit into the generic QCL framework, i.e., the UL/DL signals can be defined as QCLed. In addition, defining the UL/DL signal relation as QCL has a significant advantage, as the QCL/TCI information can be signaled to a UE in a dynamic fashion via DCI, which offers much higher flexibility in a dynamic network deployment scenario (such as a HST) than using RRC/MAC based signaling framework.
Embodiments of the present disclosure may be implemented as computer-implemented methods. The embodiments may be performed by a processing system.
In some embodiments, the processing system 1100 is included in a network device that is accessing, or part otherwise of, a telecommunications network. In one example, the processing system 1100 is in a network-side device in a wireless or wireline telecommunications network, such as a base station, a relay station, a scheduler, a controller, a gateway, a router, an applications server, or any other device in the telecommunications network. In other embodiments, the processing system 1100 is in a user-side device accessing a wireless or wireline telecommunications network, such as a mobile station, a user equipment (UE), a personal computer (PC), a tablet, a wearable communications device (e.g., a smartwatch, etc.), or any other device adapted to access a telecommunications network.
In some embodiments, one or more of the interfaces 1110, 1112, 1114 connects the processing system 1100 to a transceiver adapted to transmit and receive signaling over the telecommunications network.
The transceiver 1200 may transmit and receive signaling over any type of communications medium. In some embodiments, the transceiver 1200 transmits and receives signaling over a wireless medium. For example, the transceiver 1200 may be a wireless transceiver adapted to communicate in accordance with a wireless telecommunications protocol, such as a cellular protocol (e.g., long-term evolution (LTE), etc.), a wireless local area network (WLAN) protocol (e.g., Wi-Fi, etc.), or any other type of wireless protocol (e.g., Bluetooth, near field communication (NFC), etc.). In such embodiments, the network-side interface 1202 comprises one or more antenna/radiating elements. For example, the network-side interface 1202 may include a single antenna, multiple separate antennas, or a multi-antenna array configured for multi-layer communication, e.g., single input multiple output (SIMO), multiple input single output (MISO), multiple input multiple output (MIMO), etc. In other embodiments, the transceiver 1200 transmits and receives signaling over a wireline medium, e.g., twisted-pair cable, coaxial cable, optical fiber, etc. Specific processing systems and/or transceivers may utilize all of the components shown, or only a subset of the components, and levels of integration may vary from device to device.
While this disclosure has been described with reference to illustrative embodiments, this description is not intended to be construed in a limiting sense. Various modifications and combinations of the illustrative embodiments, as well as other embodiments of the disclosure, will be apparent to persons skilled in the art upon reference to the description. It is therefore intended that the appended claims encompass any such modifications or embodiments.
This application is a continuation of International Application No. PCT/US2021/045053, filed on Aug. 6, 2020, and entitled “System and Method for Uplink and Downlink in Multi-Point Communications,” which claims the benefit of U.S. Provisional Application No. 63/062,335, filed on Aug. 6, 2020, and entitled “System and Method for Uplink and Downlink in Multi-Point Communications.” Applications of which are hereby incorporated by reference in their entireties.
| Number | Date | Country | |
|---|---|---|---|
| 63062335 | Aug 2020 | US |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/US2021/045053 | Aug 2021 | US |
| Child | 18164293 | US |
