Downlink (DL) precompensation and quasi-co-location (QCL) signaling for coherent joint transmission (CJT)

Abstract

A method, network node and wireless device (WD) for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission are disclosed. According to one aspect, a method in a network node comprises transmitting (S144) a first reference signal (RS) over a first transmit-receive point (TRP) and transmitting (S144) a second RS over a second TRP. The method comprises receiving (S146) time delay difference and / or frequency difference information between the TRPs. The method comprises transmitting (S148) a DL channel with delay pre-compensation and / or frequency pre-compensation on the first TRP and transmitting (S148) a DL channel without delay or frequency pre-compensation on the second TRP. The method comprises transmitting (S150) QCL information indicating whether the DL channel transmitted from the first TRP and the second TRP is pre-compensated. The method further comprises pre-compensating (S152) the DL transmission through the first TRP according to the received time delay difference or frequency difference.

Description

Technical Field

[0001] The present disclosure relates to wireless communications, and more particularly to downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission. Background Art

[0002] The 3rd Generation Partnership Project (3GPP) has developed and is developing standards for the 4th (4G) (also known as Long Term Evolution (LTE)) and 5th (5G) (also known as New Radio (NR)) wireless communication systems. Such systems provide, among other features, broadband communications between network nodes (such as base stations) and mobile wireless devices (WDs), as well as communications between network nodes and between WDs. The 6th (6G) wireless communication systems are also under development.

[0003] The next generation of mobile wireless communication systems (5G) or New Radio (NR) will support a different set of use cases and a different set of deployment scenarios. The latter include deployments at low frequencies (hundreds of MHz) (similar to today's LTE) and very high frequencies (millimetre waves at tens of GHz).

[0004] Similar to LTE, NR will use OFDM (Orthogonal Frequency Division Multiplexing) in the downlink (i.e., from the network node, gNB, eNB or base station to the wireless device (WD)). In the uplink (i.e., from the WD to the gNB), OFDM and Discrete Fourier Transform (DFT) Spread OFDM (DFT-S-OFDM) (also known as Single Carrier Frequency Division Multiple Access (SC-FDMA) in LTE) will be supported. Therefore, the basic NR physical resources can be viewed as follows Figure 1 The time-frequency grid shown in the example of FIG, wherein a resource block (RB) in a 14-symbol slot is shown. A resource block corresponds to 12 consecutive subcarriers in the frequency domain. Resource blocks are numbered in the frequency domain starting with 0 from one end of the system bandwidth. Each resource element corresponds to one OFDM subcarrier during one OFDM symbol interval.

[0005] Different subcarrier spacing values ​​are supported in NR. The supported subcarrier spacing values ​​(also called different parameter sets) are given by Δf=(15×2 μ )kHz, where μ is a non-negative integer and can be one of {0, 1, 2, 3, 4}. Δf=15kHz (e.g., μ=0) is the basic (or reference) subcarrier spacing also used in LTE. μ is also called a parameter set.

[0006] In the time domain, similar to LTE, downlink (DL) and uplink (UL) transmissions in NR are organized into equal-sized subframes of 1 ms each. A subframe is further divided into multiple slots of equal duration. The slot length depends on the subcarrier spacing or parameter set and is determined by For a normal cyclic prefix (CP), each slot includes 14 OFDM symbols.

[0007] Data scheduling in NR can be based on time slots. Figure 2 An example with a 14-symbol slot is shown in , where the first two symbols contain control channels (such as the Physical Downlink Control Channel (PDCCH)) and the remaining symbols contain data channels (such as the Physical Downlink Shared Channel (PDSCH)). For convenience, subframes are referenced throughout the following sections.

[0008] Downlink transmissions can be dynamically scheduled, i.e., in each time slot, the network node (gNB) transmits downlink control information (DCI) about which WD the data is to be transmitted to and on which resource blocks in the current downlink time slot the data is to be transmitted. In NR, this control signaling is usually transmitted in the first one or two OFDM symbols of each time slot. Control information is carried on the physical control channel (PDCCH) and data is carried on the physical downlink shared channel (PDSCH). The WD first detects and decodes the PDCCH, and if the PDCCH is successfully decoded, it then decodes the corresponding PDSCH based on the decoded control information in the PDCCH.

[0009] PDCCH can also be used to dynamically schedule uplink data transmission. Similar to the downlink, the WD first decodes the uplink grant in the PDCCH, and then transmits data through the physical uplink shared channel (PUSCH) based on the decoded control information in the uplink grant (such as modulation order, coding rate, uplink resource allocation, etc.).

[0010] Tracking Reference Signal (TRS)

[0011] Similar to LTE, a channel state information reference signal (CSI-RS) is introduced in NR for channel measurement in the downlink. CSI-RS is transmitted through antenna ports (physical or virtual antennas) on certain resource elements (REs), allowing WD to measure the downlink channel associated with the antenna port. For this purpose, CSI-RS is also called non-zero power (NZP) CSI-RS. The number of antenna ports or CSI-RS ports supported in NR is {1, 2, 4, 8, 12, 16, 24, 32}.

[0012] The Tracking Reference Signal (TRS) is a special NZP CSI-RS with one port and is used for time and frequency tracking in downlink. Figure 3An example of TRS resource configuration in a physical resource block (PRB) and 2 time slots is shown. In NR, a WD can be configured with one or more periodic TRSs, or one or more periodic TRSs and aperiodic TRSs. For a periodic TRS, it has a periodicity and a time slot offset. The periodicity can be 2 μ X p One of the time slots, where X p =10, 20, 40 or 80. One TRS occupies multiple RBs. When the NZP CSI-RS resource set contains "trs-info", the NZP CSI-RS resource set is used for TRS.

[0013] Quasi-co-location

[0014] Demodulation Reference Signal (DMRS) is used for coherent demodulation of PDSCH. PDSCH can be associated with one or more DMRS antenna ports or simply DMRS ports, each port is associated with a spatial layer or a multiple input multiple output (MIMO) layer. Multiple layers can be multiplexed in the same time and frequency resources, with different data carried in different layers. The DMRS port used for PDSCH transmission is indicated in the DCI that schedules PDSCH.

[0015] Several signals may be transmitted from different antenna ports. When measured at the WD receiver, these signals may have the same large-scale characteristics (e.g., in terms of Doppler shift / spread, average delay spread, or average delay). These antenna ports are then referred to as quasi-co-located (QCL). If the WD knows that two antenna ports (a first antenna port and a second antenna port) are QCL with respect to a certain channel characteristic (e.g., Doppler spread), the WD may obtain the channel characteristics of the first antenna port (e.g., DMRS) from the second antenna port (e.g., TRS). The reference signal associated with the second antenna port (e.g., TRS) is called the QCL source RS, and the reference signal associated with the first antenna port (e.g., DMRS) is called the QCL target RS. The types of QCL supported in NR are:

[0016] 'QCL-TypeA': {Doppler shift, Doppler spread, average delay, delay spread};

[0017] 'QCL-TypeB': {Doppler shift, Doppler spread};

[0018] 'QCL-TypeC': {Doppler shift, average delay}; and

[0019] 'QCL-TypeD': {spatial Rx parameters}.

[0020] The QCL relationship is specified by the transmission configuration indicator (TCI) state. One TCI state contains one or two source RSs and the associated QCL type. If two QCL types are configured, one is of the QCL type. The WD can be configured via radio resource control (RRC) signaling with a TCI state list. For PDSCH, one or two TCI states from the list can be activated for each of up to 8 TCI code points via a media access control (MAC) control element (CE) command. Up to 8 TCI states can be activated. One of the TCI code points is indicated in the DCI that schedules the PDSCH. The WD performs PDSCH reception according to the (one or more) TCI states indicated in the TCI code point.

[0021] Table 1 is a summary of possible source RS and target RS in NR. SSB refers to synchronization signal and broadcast channel block, and CSI-RS (BM) refers to CSI-RS used for beam management in frequency range 2 (FR2).

[0022] Table 1: Supported target and source RS in NR.

[0023]

[0024]

[0025] CSI framework in NR

[0026] In NR, a WD may be configured with one or more channel state information (CSI) report configurations for WD’s DLCSI feedback. The CSI report may include one or more of the following:

[0027] Channel rank indicator (RI);

[0028] Antenna precoding matrix indicator (PMI);

[0029] Channel Quality Indicator (CQI);

[0030] DL reference signal received power (RSRP) or signal to interference and noise ratio (SINR); and

[0031] • CSI Reference Signal (CSI-RS) Resource Indicator (CRI).

[0032] Each CSI reporting configuration is associated with a bandwidth part (BWP) and contains all necessary information required for CSI reporting, including:

[0033] CSI resource configuration for channel measurement;

[0034] Reporting type, i.e. aperiodic CSI (on PUSCH), periodic CSI (on PUCCH), or semi-persistent CSI (on PUCCH, and DCI activated on PUSCH); and

[0035] Report quantity, specifying the content to be reported, such as RI, PMI, CQI, RSRP, etc.

[0036] The WD may be configured with one or more CSI resource configurations for channel measurement. Each CSI resource configuration for channel measurement may contain one or more NZP CSI-RS resource sets. For each NZP CSI-RS resource set, it may also contain one or more NZP CSI-RS resources. NZP CSI-RS resources may be periodic, semi-persistent, or aperiodic.

[0037] Periodic CSI starts after having been configured by Radio Resource Control (RRC) and is reported on the PUCCH, the associated (one or more) NZP CSI-RS resources are also periodic.

[0038] For aperiodic CSI, reporting is on PUSCH and is activated by the CSI request bit field in the DCI. The associated (one or more) NZP CSI-RS resources can be periodic, semi-persistent or aperiodic. The link between the codepoint of the CSI request field and the CSI reporting configuration is via the aperiodic CSI trigger state. The WD is configured by higher layers with a list of aperiodic CSI trigger states, where each trigger state contains an associated CSI reporting configuration. The CSI request field is used to indicate one of the aperiodic CSI trigger states, and therefore indicates a CSI reporting configuration.

[0039] If there are more than one NZP CSI-RS resource set and / or more than one CSI-IM resource set associated with the CSI report configuration, only one NZP CSI-RS resource set is selected in the aperiodic CSI triggering state. Thus, each aperiodic CSI report is based on a single NZP CSI-RS resource set.

[0040] CQI and PMI can be reported per subband or wideband. In case of wideband CQI or PMI, the CQI or PMI is for the entire bandwidth configured for CSI reporting. In case of subband CQI or PMI, the CQI or PMI is reported for each subband. Depending on the size of the BWP, the subband size in NR can range from 4RB to 32RB, as shown in the following table.

[0041] Table 5.2.1.4-2: Configurable subband sizes

[0042] Bandwidth Part (PRB) Subband size (PRB) 24–72 4，8 73–144 8，16 145–275 16，32

[0043] PDSCH transmission from multiple TRPs

[0044] In NR 3GPP Technology Release 16 (3GPP Rel-16), non-coherent joint (NC-JT) PDSCH transmission from two transmission and reception points (TRPs) was introduced, where a subset of the MIMO layers of the PDCCH is transmitted from the first TRP to the WD, and the remaining layers of the PDSCH are transmitted from the second TRP in the same time and frequency resources. The different layers are separated and received at the WD by a MIMO-capable receiver.

[0045] Figure 4 An example is shown in which a PDSCH with two layers is scheduled, where the first layer is transmitted from TRP1 and the second layer is transmitted from TRP2. This is signaled in the corresponding DCI by indicating TCI code points associated with two TCI states (a first TCI state and a second TCI state) and DMRS ports x and y in two CDM groups, where DMRS port x in the first CDM group is associated with the first TCI state and DMRS port y in the second CDM group is associated with the second TCI state. The first TCI state may include tracking reference signal 1 (TRS1) as the QCL source RS, and the second TCI state may include TRS2 as the QCL source RS.

[0046] SFN PDSCH

[0047] In NR 3GPP Rel-17, enhanced single frequency network (SFN) based PDSCH is also introduced for more robust PDSCH reception, where PDSCH is transmitted simultaneously from two TRPs in the same time and frequency resources.

[0048] Figure 5 An example is shown in , where exactly the same PDSCH and its DMRS are transmitted from two TRPs. This is indicated to the WD by the RRC configuration of the two TCI states and the system frame number (SFN) PDSCH indicated in the DCI that schedules the PDSCH. The first TCI state may contain TRS1 as the QCL source RS, while the second TCI state may contain TRS2 as the QCL source RS. The DMRS is now associated with the two TCI states because the DMRS is transmitted from two TRPs.

[0049] In NC-JT based multi-TRP PDSCH, different layers or data are transmitted from different TRPs, so for each layer, it is transmitted from only one TRP. For SFN based multi-TRP PDSCH, the same data is transmitted from different TRPs. When the signals reach the WD, the corresponding signals from different TRPs may be combined constructively or destructively, depending on the relative phase between them. In order to mitigate possible signal cancellation issues, cyclic delay diversity (CDD) is typically used in implementations to introduce frequency-dependent phase shifts between the signals so that the relative phase between the signals varies over the scheduled bandwidth.

[0050] To further enhance multi-TRP PDSCH transmission, coherent joint transmission (CJT) of PDSCH from multiple TRPs will be studied and supported in NR 3GPP Rel-18, where the signals from multiple TRPs are coherently combined at the WD through appropriate joint antenna precoding at multiple TRPs. This is achieved through CSI feedback, in which the WD measures the channels associated with multiple TRPs and reports back to the joint precoder across multiple TRPs so that the precoded signals from multiple TRPs are phase aligned when they arrive at the WD.

[0051] However, there are many challenges in supporting CJT. First, the propagation delays between different TRPs and WDs can be very different. These large delay differences will lead to large frequency-selective composite channels, i.e., channel amplitude and phase vary rapidly across frequency. In existing NR CSI feedback, the precoding matrix for each subband is reported. As specified in 3GPP Technical Standard (TS) 38.214, the subband size can vary from 2RB to 32RB. Figure 6 The phase variation within a subband of different subband sizes is shown with a one microsecond (1us) delay difference between two TRPs. Even with a two resource block (RB) subband size, the phase variation exceeds 130 degrees. For constructive combination of two signals, their phase difference should be less than 90 degrees. Therefore, with the current subband size and per-subband CSI feedback, signals from multiple TRPs cannot be coherently combined with even a 1us delay difference.

[0052] Second, even if the same nominal transmit frequency can be used at multiple TRPs, there will be some actual transmit frequency difference between the multiple TRPs due to the stability of the local oscillator. In 3GPP RAN4, the maximum transmit frequency error of a base station is specified in 3GPP Technical Standard (TS) 38.104 and Figure 7For the most stringent + / -0.05ppm requirement, there will be some residual frequency errors. These frequency errors mean that the phase of the signal will change over time. Table 2 shows the phase change over a 5ms period for different nominal transmission frequencies at + / -0.05ppm. It can be seen that even at a carrier frequency of 1GHz, the phase may change by up to 180 degrees in a 5ms period. In other words, the time offset between the time the WD measures the CSI and the time the CSI is applied needs to be much less than 5ms. This is not practical in most cases.

[0053] Table 2: Phase variation due to frequency error (+ / -0.05ppm)

[0054] Summary of the invention

[0055] Some embodiments advantageously provide methods, network nodes, and wireless devices for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission.

[0056] CSI feedback for CJT with existing subband size is allowed, and CJT of PDSCH with practical CSI feedback delay is enabled.

[0057] According to one aspect, a network node configured to communicate with a wireless device WD is provided. The network node is configured for coherent joint transmission CJT of a downlink DL channel to the WD through a first transmission and reception point TRP and a second TRP in the same time and frequency resources. The network node includes a radio interface configured to: transmit a first reference signal RS to the WD through a first TRP, and transmit a second RS to the WD through a second TRP; receive information related to at least one of a time delay difference and a frequency difference between the first TRP and the second TRP at the WD from the WD, wherein the second TRP is a reference TRP; transmit a DL channel with at least one of delay pre-compensation and frequency pre-compensation to the WD through the first TRP and transmit a DL channel without delay and frequency pre-compensation to the WD through the second TRP; and transmit quasi-co-site QCL information indicating whether the DL channel transmitted from each of the first TRP and the second TRP is pre-compensated to the WD. The network node also includes a processing circuit that communicates with the radio interface and is configured to pre-compensate the downlink channel transmitted to the WD through the first TRP according to at least one of the received time delay difference and frequency difference.

[0058] According to this aspect, in some embodiments, the DL channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information is included in the DL control information DCI format of the scheduling DL channel. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the DL channel transmitted from the second TRP is included in the second transmission configuration indication TCI state, and the first TCI state and the second TCI state are indicated in the TCI code point of the TCI field in the downlink control information DCI. In some embodiments, the QCL information in the first TCI state includes both the average delay characteristic and the Doppler shift characteristic, while the QCL information in the second TCI state does not include any of the average delay characteristic and the Doppler shift characteristic. In some embodiments, the first TCI state and the second TCI state are indicated in one of an implicit and explicit manner. In some embodiments, only the first TCI state is indicated in the TCI code point in the DCI. In some embodiments, delay precompensation is performed by applying one of a time advance and a time delay to the DL channel. In some embodiments, frequency precompensation is performed by applying frequency correction to the DL channel. In some embodiments, the QCL information also indicates one of delay precompensation, frequency precompensation, both delay and frequency precompensation, and no precompensation. In some embodiments, at least one of delay precompensation and frequency precompensation is performed by applying phase rotation in each subcarrier of the DL channel or signal. In some embodiments, the radio interface is also configured to receive channel state information CSI feedback from the WD, the CSI feedback including a precoding matrix indicator PMI indicating a first precoding matrix of a DL channel from a first TRP, and indicating a second precoding matrix of a DL channel from a second TRP. In some embodiments, the first RS and the second RS are channel state information reference signals CSI-RS. In some embodiments, the first RS and the second RS are tracking reference signals TRS. In some embodiments, the time delay difference and the frequency difference are reported together with the channel state information CSI. In some embodiments, at least one of the time delay difference and the frequency difference is obtained by the network node based on uplink measurements of uplink reference signals.

[0059] According to another aspect, a method is provided in a network node configured to communicate with a wireless device WD, the network node being configured for coherent joint transmission (CJT) of a downlink DL channel to the WD through a first transmission and reception point (TRP) and a second TRP in the same time and frequency resources. The method includes: transmitting a first reference signal (RS) to the WD through a first TRP, and transmitting a second RS to the WD through a second TRP; receiving information related to at least one of a time delay difference and a frequency difference between the first TRP and the second TRP at the WD from the WD, wherein the second TRP is a reference TRP; transmitting a DL channel with at least one of delay pre-compensation and frequency pre-compensation to the WD through the first TRP and transmitting a DL channel without delay and frequency pre-compensation to the WD through the second TRP; transmitting to the WD quasi-co-site (QCL) information indicating whether the DL channel transmitted from each of the first TRP and the second TRP is pre-compensated; and pre-compensating the downlink channel transmitted to the WD through the first TRP according to at least one of the received time delay difference and frequency difference.

[0060] According to this aspect, in some embodiments, the DL channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information is included in the DL control information DCI format of the scheduling DL channel. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the DL channel transmitted from the second TRP is included in the second transmission configuration indication TCI state, and the first TCI state and the second TCI state are indicated in the TCI code point of the TCI field in the downlink control information DCI. In some embodiments, the QCL information in the first TCI state includes both the average delay characteristic and the Doppler shift characteristic, while the QCL information in the second TCI state does not include any of the average delay characteristic and the Doppler shift characteristic. In some embodiments, the first TCI state and the second TCI state are indicated in one of an implicit and explicit manner. In some embodiments, only the first TCI state is indicated in the TCI code point in the DCI. In some embodiments, delay precompensation is performed by applying one of a time advance and a time delay to the DL channel. In some embodiments, frequency precompensation is performed by applying frequency correction to the DL channel. In some embodiments, the QCL information also indicates one of delay precompensation, frequency precompensation, both delay and frequency precompensation, and no precompensation. In some embodiments, at least one of delay precompensation and frequency precompensation is performed by applying a phase rotation in each subcarrier of a DL channel or signal. In some embodiments, the method includes receiving channel state information CSI feedback from a WD, the CSI feedback including a precoding matrix indicator PMI indicating a first precoding matrix of a DL channel from a first TRP, and indicating a second precoding matrix of a DL channel from a second TRP. In some embodiments, the first RS and the second RS are channel state information reference signals CSI-RS. In some embodiments, the first RS and the second RS are tracking reference signals TRS. In some embodiments, the time delay difference and the frequency difference are reported together with the channel state information CSI. In some embodiments, at least one of the time delay difference and the frequency difference is obtained by a network node based on an uplink measurement of an uplink reference signal.

[0061] According to yet another aspect, there is provided a WD configured to communicate with a plurality of transmission reception points TRPs. The WD includes a radio interface configured to receive from a network node a configuration for reporting at least one of a delay difference and a frequency difference between a first TRP and a second TRP based on a first reference signal RS and a second RS, the first RS and the second RS being transmitted from the first TRP and the second TRP, respectively. The WD includes a processing circuit that communicates with the radio interface and is configured to estimate at least one of a delay difference and a frequency difference based on the first RS and the second RS. The radio interface is also configured to: report at least one of the estimated delay difference and the frequency difference to the network node; receive from the network node a downlink channel scheduled by a downlink control information DCI format and quasi-co-site QCL information about the downlink channel in the DCI, the downlink channel being transmitted through both the first TRP and the second TRP; and decode the downlink channel according to the QCL information.

[0062] According to this aspect, in some embodiments, the delay difference includes at least one of a timing difference and a propagation delay difference between the first TRP and the second TRP. In some embodiments, the frequency difference includes at least one of a downlink carrier frequency difference and a downlink Doppler frequency difference between the first TRP and the second TRP. In some embodiments, the downlink channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the downlink channel transmitted from the second TRP is included in the second TCI state, and at least one of the first TCI state and the second TCI state is indicated in the TCI code point of the TCI field in the DCI. In some embodiments, the QCL information in the first TCI state includes Doppler shift, Doppler spread, average delay and delay spread. In some embodiments, the QCL information in the second TCI state does not include at least one of Doppler shift and average delay. In some embodiments, only the first TCI state is indicated in the TCI field of the DCI, and the QCL information included in the first TCI state is applied to the physical downlink shared channel PDSCH. In some embodiments, the QCL information also indicates a QCL source reference signal. In some embodiments, decoding the DL channel according to the QCL information includes: deriving a channel characteristic indicated in the QCL information from an associated QCL source RS for a physical downlink shared channel PDSCH, and using the channel characteristic to perform channel estimation of the PDSCH. In some embodiments, each of the first RS and the second RS is a channel state information reference signal CSI-RS. In some embodiments, each of the first RS and the second RS is a tracking reference signal TRS.

[0063] According to another aspect, a method in a wireless device WD is provided, the wireless device WD being configured to communicate with a network node including a first transmission reception point TRP and a second TRP. The method includes: receiving from the network node a configuration for reporting at least one of a delay difference and a frequency difference between the first TRP and the second TRP based on a first reference signal RS and a second RS, the first RS and the second RS being transmitted from the first TRP and the second TRP respectively; estimating at least one of the delay difference and the frequency difference based on the first RS and the second RS; reporting at least one of the estimated delay difference and the frequency difference to the network node; receiving from the network node a downlink channel scheduled by a downlink control information DCI format and quasi-co-site QCL information about the downlink channel in the DCI, the downlink channel being transmitted through both the first TRP and the second TRP; and decoding the downlink channel according to the QCL information.

[0064] According to this aspect, in some embodiments, the delay difference includes at least one of a timing difference and a propagation delay difference between the first TRP and the second TRP. In some embodiments, the frequency difference includes at least one of a downlink carrier frequency difference and a downlink Doppler frequency difference between the first TRP and the second TRP. In some embodiments, the downlink channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the downlink channel transmitted from the second TRP is included in the second TCI state, and at least one of the first TCI state and the second TCI state is indicated in the TCI code point of the TCI field in the DCI. In some embodiments, the QCL information in the first TCI state includes Doppler shift, Doppler spread, average delay and delay spread. In some embodiments, the QCL information in the second TCI state does not include at least one of Doppler shift and average delay. In some embodiments, only the first TCI state is indicated in the TCI field of the DCI, and the QCL information included in the first TCI state is applied to the physical downlink shared channel PDSCH. In some embodiments, the QCL information also indicates a QCL source reference signal. In some embodiments, decoding the DL channel according to the QCL information includes: deriving a channel characteristic indicated in the QCL information from an associated QCL source RS for a physical downlink shared channel PDSCH, and using the channel characteristic to perform channel estimation of the PDSCH. In some embodiments, each of the first RS and the second RS is a channel state information reference signal CSI-RS. In some embodiments, each of the first RS and the second RS is a tracking reference signal TRS. BRIEF DESCRIPTION OF THE DRAWINGS

[0065] A more complete understanding of the present embodiments and the attendant advantages and features thereof will be more readily appreciated by reference to the following detailed description when considered in conjunction with the accompanying drawings, in which:

[0066] Figure 1 It is a graph of NR physical resources;

[0067] Figure 2 It is a diagram of the NR time domain structure;

[0068] Figure 3 is an example of a resource element;

[0069] Figure 4 is an example of incoherent joint transmission;

[0070] Figure 5 is an example of transmitting PDSCH from two TRPs;

[0071] Figure 6 is a table of phase changes for each subband size;

[0072] Figure 7 It is a table of transmission frequency accuracy;

[0073] Figure 8 is a schematic diagram illustrating an example network architecture of a communication system connected to a host computer via an intermediate network according to principles of the present disclosure;

[0074] Fig. 9 is a block diagram of a host computer communicating with a wireless device via a network node over an at least partially wireless connection according to some embodiments of the present disclosure;

[0075] Fig.10 is a flow chart illustrating an example method for executing a client application at a wireless device implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0076] Fig.11 is a flow chart illustrating an example method for receiving user data at a wireless device implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0077] Fig.12 is a flow chart illustrating an example method implemented in a communication system including a host computer, a network node, and a wireless device for receiving user data from a wireless device at a host computer according to some embodiments of the present disclosure;

[0078] Fig.13is a flow chart illustrating an example method for receiving user data at a host computer implemented in a communication system including a host computer, a network node, and a wireless device according to some embodiments of the present disclosure;

[0079] Fig.14 is a flow chart of an example process for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling in a network node for coherent joint transmission;

[0080] Fig.15 is a flow chart of an example process for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission in a wireless device;

[0081] Fig.16 is a flow chart of an example process for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling in a network node for coherent joint transmission;

[0082] Fig.17 is a flow chart of an example process for downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission in a wireless device;

[0083] Fig.18 is an example of coherent joint transmission (CJT) from two TRPs;

[0084] Fig.19 is an example of CSI measurement and feedback for CJT from two TRPs;

[0085] Fig. 20 is an example of delayed compensation;

[0086] Fig.21 is another example of CSI measurement and feedback for CJT from two TRPs; and

[0087] Fig. 22 is an example of an implicit indication of delay and / or frequency compensation. DETAILED DESCRIPTION

[0088] Before describing the example embodiments in detail, it is noted that the embodiments reside primarily in a combination of device components and processing steps related to downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission. Therefore, in the accompanying drawings, components have been represented by conventional symbols where appropriate, and only those specific details relevant to understanding the embodiments are shown so as not to obscure the disclosure with details that will be readily apparent to those skilled in the art having the benefit of the description herein. Throughout this description, like numbers refer to like elements.

[0089] As used herein, relational terms such as "first" and "second", "top" and "bottom", etc., may be used only to distinguish one entity or element from another entity or element, without necessarily requiring or implying any physical or logical relationship or order between such entities or elements. The terms used herein are for the purpose of describing specific embodiments only and are not intended to limit the concepts described herein. As used herein, the singular forms "a", "an", and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprise, comprising, include, and / or including", when used herein, specify the presence of the described features, wholes, steps, operations, elements, and / or components, but do not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or groups thereof.

[0090] In the embodiments described herein, the connection terms "in communication with" and the like may be used to indicate electrical communication or data communication, which may be achieved, for example, by physical contact, induction, electromagnetic radiation, radio signaling, infrared signaling, or optical signaling. Those skilled in the art will appreciate that multiple components may interoperate, and modifications and variations in achieving electrical and data communications are possible.

[0091] In some embodiments described herein, the terms "coupled," "connected," and the like may be used herein to indicate a connection (although not necessarily a direct one), and may include wired and / or wireless connections.

[0092] The term "network node" used herein may be any kind of network node included in a radio network, which may also include any of the following items: a base station (BS), a radio base station, a base transceiver station (BTS), a base station controller (BSC), a radio network controller (RNC), a gNode B (gNB), an evolved Node B (eNB or eNodeB), a Node B, an MSR radio node such as a multi-standard radio (MSR) BS, a multi-cell / multicast coordination entity (MCE), an integrated access and backhaul (IAB) node, a relay node, a donor node controlling a relay, a radio access point (AP), a transmission point, a transmission node, a remote radio unit (RRU) remote radio head (RRH), a core network node (e.g., a mobile management entity (MME), a self-organizing network (SON) node, a coordination node, a positioning node, an MDT node, etc.), an external node (e.g., a third-party node, a node outside the current network), a node in a distributed antenna system (DAS), a spectrum access system (SAS) node, an element management system (EMS), etc. The network node may also include a test device. As used herein, the term "radio node" may also be used to refer to a wireless device (WD), such as a wireless device (WD) or a radio network node.

[0093] In some embodiments, non-limiting terms wireless device (WD) or user equipment (UE) are used interchangeably. WD herein can be any type of wireless device capable of communicating with a network node or another WD via a radio signal, such as a wireless device (WD). WD can also be a radio communication device, a target device, a device to device (D2D) WD, a machine type WD, or a WD capable of machine-to-machine communication (M2M), a low-cost and / or low-complexity WD, a sensor equipped with a WD, a tablet, a mobile terminal, a smart phone, a laptop embedded device (LEE), a laptop mounted device (LME), a USB dongle, a customer premises equipment (Customer Premises Equipment) (CPE), an Internet of Things (IoT) device, or a narrowband IoT (NB-IOT) device, etc.

[0094] Furthermore, in some embodiments, the generic term "radio network node" is used. It may be any kind of radio network node, which may include any of the following: base station, radio base station, base transceiver station, base station controller, network controller, RNC, evolved Node B (eNB), Node B, gNB, multi-cell / multicast coordination entity (MCE), IAB node, relay node, access point, radio access point, remote radio unit (RRU), remote radio head (RRH).

[0095] Note that although terminology from one particular wireless system such as, for example, 3GPP LTE and / or New Radio (NR) may be used in this disclosure, this should not be viewed as limiting the scope of the present disclosure to only the aforementioned systems. Other wireless systems including, but not limited to, Wideband Code Division Multiple Access (WCDMA), Worldwide Interoperability for Microwave Access (WiMax), Ultra Mobile Broadband (UMB), and Global System for Mobile Communications (GSM) may also benefit from applying the ideas encompassed within this disclosure.

[0096] Further note that the functions described herein as being performed by a wireless device or network node may be distributed across multiple wireless devices and / or network nodes. In other words, it is contemplated that the functions of the network nodes and wireless devices described herein are not limited to being performed by a single physical device and may in fact be distributed across several physical devices.

[0097] Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present disclosure belongs. It will be further understood that, unless expressly defined as such herein, the terms used herein should be interpreted as having a meaning consistent with their meaning in the context of the relevant art and this specification, and will not be interpreted in an idealized or overly formal sense.

[0098] Some embodiments provide downlink (DL) pre-compensation and quasi-co-location (QCL) signaling for coherent joint transmission.

[0099] Referring again to the drawings, wherein like elements are referred to by like reference numerals, Figure 81 shows a schematic diagram of a communication system 10 according to an embodiment, such as a 3GPP type cellular network that can support standards such as LTE and / or NR (5G), including an access network 12 such as a radio access network and a core network 14. The access network 12 includes a plurality of network nodes 16a, 16b, 16c (collectively referred to as network nodes 16) (such as NBs, eNBs, gNBs or other types of wireless access points), each of which defines a corresponding coverage area 18a, 18b, 18c (collectively referred to as coverage area 18). Each network node 16a, 16b, 16c is connectable to the core network 14 via a wired or wireless connection 20. A first wireless device (WD) 22a located in the coverage area 18a is configured to be wirelessly connected to the corresponding network node 16a, or to be paged by the corresponding network node 16a. A second WD 22b in the coverage area 18b is wirelessly connectable to the corresponding network node 16b. Although multiple WDs 22a, 22b (collectively referred to as wireless devices 22) are shown in this example, the disclosed embodiments are equally applicable to situations where only a single WD is in the coverage area or a single WD is connecting to a corresponding network node 16. Note that although only two WDs 22 and three network nodes 16 are shown for convenience, the communication system may include more WDs 22 and network nodes 16.

[0100] Furthermore, it is contemplated that the WD 22 may communicate with more than one network node 16 and more than one type of network node 16 simultaneously, and / or be configured to communicate with them alone. For example, the WD 22 may have dual connectivity with a network node 16 that supports LTE and the same or different network node 16 that supports NR. As an example, the WD 22 may communicate with an eNB of LTE / E-UTRAN and a gNB of NR / NG-RAN.

[0101] The communication system 10 itself may be connected to a host computer 24, which may be embodied in hardware and / or software as a stand-alone server, a cloud-implemented server, a distributed server, or as processing resources in a server farm. The host computer 24 may be under the ownership or control of a service provider, or may be operated by or on behalf of the service provider. The connections 26, 28 between the communication system 10 and the host computer 24 may extend directly from the core network 14 to the host computer 24, or may extend via an optional intermediate network 30. The intermediate network 30 may be a public network, a private network, or a combination of one or more of a managed network. The intermediate network 30, if any, may be a backbone network or the Internet. In some embodiments, the intermediate network 30 may include two or more subnetworks (not shown).

[0102] Figure 8 The communication system as a whole can realize the connectivity between one of the connected WD 22a, 22b and the host computer 24. This connectivity can be described as an over-the-top (OTT) connection. The host computer 24 and the connected WD 22a, 22b are configured to use the access network 12, the core network 14, any intermediate network 30 and possible additional infrastructure (not shown) as intermediaries to transfer data and / or signaling via the OTT connection. The OTT connection can be transparent in the sense that at least some of the participating communication devices through which the OTT connection passes do not know the routes of the uplink and downlink communications. For example, the past routes of the incoming downlink communications may not or need not be notified to the network node 16, and the downlink communications have data to be forwarded (e.g., handed over) to the connected WD 22a originating from the host computer 24. Similarly, the network node 16 does not need to know the future routes of the outgoing uplink communications originating from the WD 22a toward the host computer 24.

[0103] The network node 16 is configured to include a precoding unit 32, which can be configured to apply one of delay and frequency precompensation to the downlink signal. The precoding unit 32 can be configured to precompensate the downlink channel transmitted to the WD (22) through the first TRP according to at least one of the received time delay difference and frequency difference. The WD 22 is configured to include a precompensation unit 34, which can be configured to precompensate one of the delay difference and frequency difference between multiple transmission reception points TRP for the physical downlink shared channel PDSCH. The precompensation unit 34 can be configured to estimate at least one of the delay difference and the frequency difference based on the first RS and the second RS.

[0104] According to the embodiment, reference will now be made to Fig. 9An example implementation of the WD 22, network node 16, and host computer 24 discussed in the previous paragraphs is described. In the communication system 10, the host computer 24 includes hardware (HW) 38, which includes a communication interface 40, which is configured to establish and maintain a wired or wireless connection for the interface with different communication devices of the communication system 10. The host computer 24 also includes a processing circuit 42, which may have storage and / or processing capabilities. The processing circuit 42 may include a processor 44 and a memory 46. In particular, in addition to or in place of a processor and a memory such as a central processing unit, the processing circuit 42 may also include an integrated circuit for processing and / or control, for example, one or more processors and / or processor cores and / or FPGAs (field programmable gate arrays) and / or ASICs (application-specific integrated circuits) suitable for executing instructions. The processor 44 may be configured to access (e.g., write to and / or read from) a memory 46, which may include any kind of volatile and / or non-volatile memory, such as cache and / or buffer memory and / or RAM (random access memory) and / or ROM (read only memory) and / or optical memory and / or EPROM (erasable programmable read-only memory).

[0105] Processing circuit 42 may be configured to control any of the methods and / or processes described herein, and / or to cause such methods and / or processes to be performed, for example, by host computer 24. Processor 44 corresponds to one or more processors 44 for performing the functions of host computer 24 described herein. Host computer 24 includes memory 46, which is configured to store data, programmatic software code, and / or other information described herein. In some embodiments, software 48 and / or host application 50 may include instructions that, when executed by processor 44 and / or processing circuit 42, cause processor 44 and / or processing circuit 42 to perform the processes described herein with respect to host computer 24. The instructions may be software associated with host computer 24.

[0106] The software 48 may be executable by the processing circuit 42. The software 48 includes a host application 50. The host application 50 may be operable to provide services to a remote user (such as a WD 22 connected via an OTT connection 52 terminated at the WD 22 and the host computer 24). When providing services to the remote user, the host application 50 may provide user data transmitted using the OTT connection 52. "User data" may be data and information described herein as implementing the functionality. In one embodiment, the host computer 24 may be configured to provide control and functionality to a service provider, and may be operated by or on behalf of the service provider. The processing circuit 42 of the host computer 24 may enable the host computer 24 to observe, monitor, control, transmit and / or receive from the network node 16 and / or the wireless device 22 to the network node 16 and / or the wireless device 22.

[0107] The communication system 10 also includes a network node 16, which is arranged in the communication system 10 and includes hardware 58, which enables it to communicate with the host computer 24 and the WD 22. The hardware 58 may include a communication interface 60 for establishing and maintaining a wired or wireless connection to the interface of different communication devices of the communication system 10, and a radio interface 62 for establishing and maintaining a wireless connection 64 with the WD 22 located in the coverage area 18 served by the network node 16. The radio interface 62 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers. The communication interface 60 may be configured to facilitate a connection 66 to the host computer 24. The connection 66 may be direct, or it may pass through the core network 14 of the communication system 10 and / or through one or more intermediate networks 30 external to the communication system 10.

[0108] In the illustrated embodiment, the hardware 58 of the network node 16 also includes a processing circuit 68. The processing circuit 68 may include a processor 70 and a memory 72. In particular, in addition to or in place of a processor such as a central processing unit and a memory, the processing circuit 68 may also include an integrated circuit for processing and / or control, such as one or more processors and / or processor cores and / or an FPGA (field programmable gate array) and / or an ASIC (application-specific integrated circuit) adapted to execute instructions. The processor 70 may be configured to access the memory 72 (e.g., write to the memory 72 and / or read from the memory 72), and the memory 72 may include any kind of volatile and / or non-volatile memory, such as a cache and / or buffer memory and / or a RAM (random access memory) and / or a ROM (read-only memory) and / or an optical memory and / or an EPROM (erasable programmable read-only memory).

[0109] Therefore, the network node 16 also has software 74, which is stored internally, for example, in the memory 72, or stored in an external memory (e.g., a database, a storage array, a network storage device, etc.) accessible by the network node 16 via an external connection. The software 74 is executable by the processing circuit 68. The processing circuit 68 can be configured to control any of the methods and / or processes described herein, and / or cause such methods and / or processes to be performed, for example, by the network node 16. The processor 70 corresponds to one or more processors 70 for performing the network node 16 functions described herein. The memory 72 is configured to store data, programmed software code, and / or other information described herein. In some embodiments, the software 74 may include instructions that, when executed by the processor 70 and / or the processing circuit 68, cause the processor 70 and / or the processing circuit 68 to perform the processes described herein with respect to the network node 16. For example, the processing circuit 68 of the network node 16 may include a precoding unit 32, which may be configured to apply one of delay and frequency precompensation to the downlink signal. The precoding unit 32 may be configured to pre-compensate a downlink channel transmitted to the WD (22) via the first TRP based on at least one of the received time delay difference and the frequency difference.

[0110] The communication system 10 also includes the already mentioned WD 22. The WD 22 may have hardware 80, which may include a radio interface 82 configured to establish and maintain a wireless connection 64 with a network node 16 serving the coverage area 18 in which the WD 22 is currently located. The radio interface 82 may be formed as or may include, for example, one or more RF transmitters, one or more RF receivers, and / or one or more RF transceivers.

[0111] The hardware 80 of the WD 22 also includes a processing circuit 84. The processing circuit 84 may include a processor 86 and a memory 88. In particular, in addition to or in place of a processor and a memory such as a central processing unit, the processing circuit 84 may include an integrated circuit for processing and / or control, such as one or more processors and / or processor cores and / or an FPGA (field programmable gate array) and / or an ASIC (application-specific integrated circuit) suitable for executing instructions. The processor 86 may be configured to access the memory 88 (e.g., write to the memory 88 and / or read from the memory 88), and the memory 88 may include any kind of volatile and / or non-volatile memory, such as a cache and / or buffer memory and / or a RAM (random access memory) and / or a ROM (read-only memory) and / or an optical memory and / or an EPROM (erasable programmable read-only memory).

[0112] Therefore, WD 22 may also include software 90 stored in, for example, a memory 88 at WD 22 or stored in an external memory (e.g., a database, a storage array, a network storage device, etc.) accessible by WD 22. Software 90 may be executable by processing circuit 84. Software 90 may include client application 92. Client application 92 may be operable to provide services to human or non-human users via WD 22 under the support of host computer 24. In host computer 24, the executed host application 50 may communicate with the executed client application 92 via an OTT connection 52 terminated at WD 22 and host computer 24. When providing services to users, client application 92 may receive request data from host application 50 and provide user data in response to the request data. OTT connection 52 may transmit both request data and user data. Client application 92 may interact with the user to generate the user data it provides.

[0113] The processing circuit 84 may be configured to control any method and / or process described herein and / or to cause such a method and / or process to be performed, for example, by the WD 22. The processor 86 corresponds to one or more processors 86 for performing the WD 22 functions described herein. The WD 22 includes a memory 88 configured to store data, programming software code, and / or other information described herein. In some embodiments, the software 90 and / or the client application 92 may include instructions that, when executed by the processor 86 and / or the processing circuit 84, cause the processor 86 and / or the processing circuit 84 to perform the process described herein with respect to the WD 22. For example, the processing circuit 84 of the wireless device 22 may include a pre-compensation unit 34, which may be configured to pre-compensate one of the delay difference and the frequency difference between multiple transmission reception points TRP for the physical downlink shared channel PDSCH. The pre-compensation unit 34 may be configured to estimate at least one of the delay difference and the frequency difference based on the first RS and the second RS.

[0114] In some embodiments, the internal workings of network node 16, WD 22, and host computer 24 may be as follows: Fig. 9 As shown in , and independently, the surrounding network topology can be Figure 8 network topology.

[0115] exist Fig. 9, the OTT connection 52 has been abstractly drawn to illustrate communications between the host computer 24 and the wireless device 22 via the network node 16, without explicit reference to any intermediary devices and the precise routing of messages via these devices. The network infrastructure may determine the routing, which may be configured to be hidden from the WD 22 or the service provider operating the host computer 24, or both. When the OTT connection 52 is active, the network infrastructure may further make decisions by which it dynamically changes the routing (e.g., based on reconfiguration of the network or load balancing considerations).

[0116] The wireless connection 64 between the WD 22 and the network node 16 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improves the performance of the OTT service provided to the WD 22 using the OTT connection 52, where the wireless connection 64 may form the last leg. More specifically, the teachings of some of these embodiments may improve data rates, latency, and / or power consumption, and thereby provide benefits such as reduced user waiting time, relaxed restrictions on file size, better responsiveness, extended battery life, and the like.

[0117] In some embodiments, a measurement process may be provided for the purpose of monitoring the data rate, latency, and other factors improved by one or more embodiments. There may further be optional network functionality for reconfiguring the OTT connection 52 between the host computer 24 and the WD 22 in response to changes in the measurement results. The measurement process and / or network functionality for reconfiguring the OTT connection 52 may be implemented with the software 48 of the host computer 24, or with the software 90 of the WD 22, or with both. In an embodiment, a sensor (not shown) may be deployed in or associated with a communication device through which the OTT connection 52 passes; the sensor may participate in the measurement process by supplying the values ​​of the monitored quantities exemplified above, or supplying the values ​​of other physical quantities from which the software 48, 90 can calculate or estimate the monitored quantities. The reconfiguration of the OTT connection 52 may include message formats, retransmission settings, preferred routes, etc.; the reconfiguration does not need to affect the network node 16, and it may be unknown or imperceptible to the network node 16. Some such processes and functionalities may be known and practiced in the art. In some embodiments, the measurements may involve proprietary WD signaling that facilitates the host computer 24's measurements of throughput, propagation time, latency, etc. In some embodiments, the measurements may be achieved because the software 48, 90 uses the OTT connection 52 to cause messages (particularly empty or "dummy" messages) to be transmitted while it monitors propagation time, errors, etc.

[0118] Thus, in some embodiments, the host computer 24 includes processing circuitry 42 configured to provide user data and a communication interface 40 configured to forward the user data to a cellular network for transmission to the WD 22. In some embodiments, the cellular network also includes a network node 16 having a radio interface 62. In some embodiments, the network node 16 is configured and / or the processing circuitry 68 of the network node 16 is configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / ending transmissions to the WD 22 and / or preparing / terminating / maintaining / supporting / ending reception of transmissions from the WD 22.

[0119] In some embodiments, host computer 24 includes processing circuitry 42 and communication interface 40 configured to receive user data originating from transmissions from WD 22 to network node 16. In some embodiments, WD 22 is configured to and / or includes a radio interface 82 and / or processing circuitry 84 configured to perform the functions and / or methods described herein for preparing / initiating / maintaining / supporting / ending transmissions to network node 16 and / or preparing / terminating / maintaining / supporting / ending reception of transmissions from network node 16.

[0120] Although Figure 8 and Fig. 9 Various "units" such as pre-coding unit 32 and pre-compensation unit 34 are shown as being within respective processors, but it is contemplated that these units may be implemented such that a portion of the unit is stored in a corresponding memory within the processing circuit. In other words, these units may be implemented within the processing circuit in hardware or a combination of hardware and software.

[0121] Fig.10 is a diagram showing a communication system (such as, for example, Figure 8 and Fig. 9 Flowchart of an example method implemented in a communication system of FIG. 1 . The communication system may include a host computer 24, a network node 16, and a WD 22, which may be reference Fig. 9Those host computers, network nodes, and WDs described herein. In a first step of the method, host computer 24 provides user data (box S100). In an optional sub-step of the first step, host computer 24 provides user data by executing a host application (such as, for example, host application 50) (box S102). In a second step, host computer 24 initiates a transmission to WD 22 carrying user data (box S104). In an optional third step, in accordance with the teachings of the embodiments described throughout this disclosure, network node 16 transmits user data carried in the transmission initiated by host computer 24 to WD 22 (box S106). In an optional fourth step, WD 22 executes a client application (such as, for example, client application 92) associated with the host application 50 executed by host computer 24 (box S108).

[0122] Fig.11 is a diagram showing a communication system (such as, for example, Figure 8 Flowchart of an example method implemented in a communication system of FIG. 1 . The communication system may include a host computer 24, a network node 16, and a WD 22, which may be reference Figure 8 and Fig. 9 1 and 2. In the first step of the method, host computer 24 provides user data (block S110). In an optional substep (not shown), host computer 24 provides user data by executing a host application (such as, for example, host application 50). In a second step, host computer 24 initiates a transmission to WD 22 carrying user data (block S112). According to the teachings of the embodiments described throughout this disclosure, the transmission can be transmitted via network node 16. In an optional third step, WD 22 receives the user data carried in the transmission (block S114).

[0123] Fig.12 is a diagram showing a communication system (such as, for example, Figure 8 Flowchart of an example method implemented in a communication system of FIG. 1 . The communication system may include a host computer 24, a network node 16, and a WD 22, which may be reference Figure 8 and Fig. 9Those host computers, network nodes, and WDs described herein. In an optional first step of the method, WD 22 receives input data provided by host computer 24 (box S116). In an optional sub-step of the first step, WD 22 executes client application 92, which provides user data (box S118) as a reaction to the received input data provided by host computer 24. Additionally or alternatively, in an optional second step, WD 22 provides user data (box S120). In an optional sub-step of the second step, WD 22 provides user data (box S122) by executing a client application (such as, for example, client application 92). When providing user data, the executed client application 92 may further consider user input received from the user. Regardless of the specific manner in which the user data is provided, in an optional third sub-step, WD 22 may initiate transmission of user data to host computer 24 (box S124). In a fourth step of the method, host computer 24 receives user data transmitted from WD 22 (block S126 ) in accordance with the teachings of the embodiments described throughout this disclosure.

[0124] Fig.13 is a diagram showing a communication system (such as, for example, Figure 8 Flowchart of an example method implemented in a communication system of FIG. 1 . The communication system may include a host computer 24, a network node 16, and a WD 22, which may be reference Figure 8 and Fig. 9 In an optional first step of the method, network node 16 receives user data from WD 22 in accordance with the teachings of the embodiments described throughout this disclosure (block S128). In an optional second step, network node 16 initiates transmission of the received user data to host computer 24 (block S130). In a third step, host computer 24 receives user data carried in the transmission initiated by network node 16 (block S132).

[0125] Fig.14Flowchart of an example process of downlink (DL) precompensation and quasi co-location (QCL) signaling for coherent joint transmission in a network node 16. One or more blocks described herein may be performed by one or more elements of the network node 16, such as by one or more of the processing circuit 68 (including the precoding unit 32), the processor 70, the radio interface 62, and / or the communication interface 60. The network node 16 is configured to receive a precoder matrix indicator PMI from the WD by subband, such as via the processing circuit 68 and / or the processor 70 and / or the radio interface 62 and / or the communication interface 60, which indicates the joint antenna precoder of multiple transmission reception points TRP (box S134). The process also includes applying one of delay and frequency precompensation to the downlink signal (box S136). The process also includes applying antenna precoding to the precompensated downlink signal at each subband based on the indicated joint antenna precoder (box S138).

[0126] In some embodiments, one of the delay and frequency precompensation is based at least in part on a time delay between TRPs. In some embodiments, applying one of the delay and frequency precompensation includes applying one of the delay and frequency precompensation to multiple TRPs. In some embodiments, the method further includes transmitting quasi-co-located QCL information to the WD. In some embodiments, the method includes linking a first TRP to a first transmission configuration indicator TCI state and associating a set of remaining TCI states with other TRPs.

[0127] Fig.15 is a flow chart of an example process in the wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of the wireless device 22, such as by one or more of the processing circuit 84 (including the pre-compensation unit 34), the processor 86, the radio interface 82, and / or the communication interface 60. The wireless device 22 is configured, such as via the processing circuit 84 and / or the processor 86 and / or the radio interface 82, to pre-compensate one of the delay difference and the frequency difference between the multiple transmission reception points TRP for the physical downlink shared channel PDSCH (block S140); and apply a set of in-phase coefficients to the PDSCH of the TRP (block S142).

[0128] In some embodiments, one of the delay difference and the frequency difference is determined based at least in part on measurements at WD 22. In some embodiments, one of the delay difference and the frequency difference is determined based at least in part on measurements at network node 16. In some embodiments, one of the delay difference and the frequency difference is based at least in part on a reference signal associated with a reference TRP. In some embodiments, the method further comprises determining a set of channel characteristics based at least in part on a quasi co-location type. In some embodiments, the method further comprises transmitting a co-phase coefficient to network node 16.

[0129] Fig.16 is a flow chart of another example process for downlink (DL) precompensation and quasi co-location (QCL) signaling for coherent joint transmission in the network node 16. One or more blocks described herein may be performed by one or more elements of the network node 16, such as by one or more of the processing circuitry 68 (including the precoding unit 32), the processor 70, the radio interface 62, and / or the communication interface 60. The network node 16 is configured, such as via the processing circuit 68 and / or the processor 70 and / or the radio interface 62 and / or the communication interface 60, to transmit a first reference signal RS to the WD 22 through a first TRP and to transmit a second RS to the WD 22 through a second TRP (box S144); receive information related to at least one of a time delay difference and a frequency difference between the first TRP and the second TRP at the WD 22 from the WD 22, wherein the second TRP is a reference TRP (box S146); transmit a DL channel with at least one of delay pre-compensation and frequency pre-compensation to the WD 22 through the first TRP and transmit a DL channel without delay and frequency pre-compensation to the WD 22 through the second TRP (box S148); transmit quasi-co-site QCL information indicating whether the DL channel transmitted from each of the first TRP and the second TRP is pre-compensated to the WD 22 (box S150); and pre-compensate a downlink channel transmitted to the WD 22 through the first TRP based on at least one of the received time delay difference and frequency difference (box S152).

[0130] In some embodiments, the DL channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information is included in the DL control information DCI format of the scheduling DL channel. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the DL channel transmitted from the second TRP is included in the second transmission configuration indication TCI state, and the first TCI state and the second TCI state are indicated in the TCI code point of the TCI field in the downlink control information DCI. In some embodiments, the QCL information in the first TCI state includes both the average delay characteristic and the Doppler shift characteristic, while the QCL information in the second TCI state does not include any of the average delay characteristic and the Doppler shift characteristic. In some embodiments, the first TCI state and the second TCI state are indicated either implicitly or explicitly. In some embodiments, only the first TCI state is indicated in the TCI code point in the DCI. In some embodiments, delay precompensation is performed by applying one of time advance and time delay to the DL channel. In some embodiments, frequency precompensation is performed by applying frequency correction to the DL channel. In some embodiments, the QCL information also indicates one of delay precompensation, frequency precompensation, both delay and frequency precompensation, and no precompensation. In some embodiments, at least one of delay precompensation and frequency precompensation is performed by applying a phase rotation in each subcarrier of a DL channel or signal. In some embodiments, the method includes receiving channel state information CSI feedback from WD 22, the CSI feedback including a precoding matrix indicator PMI indicating a first precoding matrix of a DL channel from a first TRP and indicating a second precoding matrix of a DL channel from a second TRP. In some embodiments, the first RS and the second RS are channel state information reference signals CSI-RS. In some embodiments, the first RS and the second RS are tracking reference signals TRS. In some embodiments, the time delay difference and the frequency difference are reported together with the channel state information CSI. In some embodiments, at least one of the time delay difference and the frequency difference is obtained by the network node 16 based on uplink measurements of uplink reference signals.

[0131] Fig.17is a flow chart of another example process in the wireless device 22 according to some embodiments of the present disclosure. One or more blocks described herein may be performed by one or more elements of the wireless device 22, such as by one or more of the processing circuit 84 (including the precompensation unit 34), the processor 86, the radio interface 82, and / or the communication interface 60. The wireless device 22 is configured, such as via the processing circuit 84 and / or the processor 86 and / or the radio interface 82, to receive from the network node 16 a configuration for reporting at least one of a delay difference and a frequency difference between a first TRP and a second TRP based on a first reference signal RS and a second RS, the first RS and the second RS being transmitted from the first TRP and the second TRP, respectively (box S154); estimating at least one of a delay difference and a frequency difference based on the first RS and the second RS (box S156); reporting at least one of the estimated delay difference and the frequency difference to the network node 16 (box S158); receiving from the network node 16 a downlink channel scheduled by a downlink control information DCI format and quasi-co-site QCL information about the downlink channel in the DCI, the downlink channel being transmitted through both the first TRP and the second TRP (box S160); and decoding the downlink channel according to the QCL information (box S162).

[0132] In some embodiments, the delay difference includes at least one of a timing difference and a propagation delay difference between the first TRP and the second TRP. In some embodiments, the frequency difference includes at least one of a downlink carrier frequency difference and a downlink Doppler frequency difference between the first TRP and the second TRP. In some embodiments, the downlink channel is a physical downlink shared channel PDSCH. In some embodiments, the QCL information of the DL channel transmitted from the first TRP is included in the first transmission configuration indication TCI state, and the QCL information of the downlink channel transmitted from the second TRP is included in the second TCI state, and at least one of the first TCI state and the second TCI state is indicated in the TCI code point of the TCI field in the DCI. In some embodiments, the QCL information in the first TCI state includes Doppler shift, Doppler spread, average delay and delay spread. In some embodiments, the QCL information in the second TCI state does not include at least one of Doppler shift and average delay. In some embodiments, only the first TCI state is indicated in the TCI field of the DCI, and the QCL information included in the first TCI state is applied to the physical downlink shared channel PDSCH. In some embodiments, the QCL information also indicates a QCL source reference signal. In some embodiments, decoding the DL channel according to the QCL information includes: deriving a channel characteristic indicated in the QCL information from an associated QCL source RS for a physical downlink shared channel PDSCH, and using the channel characteristic to perform channel estimation of the PDSCH. In some embodiments, each of the first RS and the second RS is a channel state information reference signal CSI-RS. In some embodiments, each of the first RS and the second RS is a tracking reference signal TRS.

[0133] Having described the general process flow of the arrangements of the present disclosure, and having provided examples of hardware and software arrangements for implementing the processes and functions of the present disclosure, the following section provides details and examples of arrangements for downlink (DL) pre-compensation and quasi-co-site (QCL) signaling for coherent joint transmission.

[0134] Coherent Joint Transmission

[0135] Fig.18 An example of transmission of a signal s(t) from two TRPs is shown. s(t) is multiplied by two in-phase coefficients w1 and w2 at the two TRPs before being transmitted to WD 22. The effective propagation channels from the two TRPs to WD 22 (including the transmitter and receiver circuits and antenna patterns associated with the two TRPs) are denoted by h1 and h2, respectively. f1 and f2 are the transmission frequencies, and and is the random initial phase at the two TRPs. τ is the difference in propagation delay (including possible timing offset) between the two TRPs.

[0136] The composite signal at WD 22 can be expressed as

[0137]

[0138] For narrowband signals and when the delay τ is small, the signal envelope does not change much, that is, s(t-τ) is s(t). Therefore:

[0139]

[0140] or

[0141]

[0142] To coherently combine the signals from the two TRPs, the following in-phase coefficients can be used:

[0143]

[0144]

[0145] Where ∠(x) refers to the angle of the complex variable x. When the in-phase coefficients in equations 4a-4b above are applied, the resulting composite signal is:

[0146]

[0147] Alternatively, the in-phase coefficient may be as follows:

[0148] W1 = 1 (Equation 6a)

[0149]

[0150] When the in-phase coefficients in equations 6a-6b above are applied, the resulting composite signal is:

[0151]

[0152] Note that the only difference between Equation 5 and Equation 7 is the phase factor Phase Factor Will be removed at the WD receiver and have no impact on receiver performance.

[0153] Note that the above also applies when multiple antenna ports are deployed in each TRP. In this case, additional precoding or beamforming can be applied to s(t), where s(t) is the data associated with the MIMO layer of DMRS or PDSCH. The signal received from TRP1 will become Where H1 is the N1 by M channel matrix, V1 is the N1 by 1 precoding vector associated with the corresponding MIMO layer, N1 is the number of antenna ports deployed at TRP, and M is the number of receive antennas at WD 22. Similarly, the signal received from TRP2 will become Where H2 is the N2 times M channel matrix, V2 is the N2 times 1 precoding vector associated with the corresponding MIMO layer, and N2 is the number of antenna ports deployed at TRP2. For CJT, it is foreseeable that {V1, V2} and the co-phase coefficients {w1, W2} are reported by WD22 as part of the precoding matrix indicator (PMI) in the CSI.

[0154] Delay and frequency precompensation

[0155] It can be observed from Equation 4b and Equation 6b that in the case of a propagation delay difference between two TRPs, the desired in-phase coefficients are frequency dependent, i.e., different sets of in-phase coefficients are required at different frequencies. In the case of a frequency difference between two TRPs, the in-phase coefficients are also time dependent, i.e., different sets of in-phase coefficients are required at different times. Therefore, if both the propagation delay and the frequency of the two TRPs are different, the desired in-phase coefficients are both frequency and time dependent.

[0156] It is foreseeable that for CSI feedback in CJT on two TRPs, a CSI-RS resource set containing two CSI-RS resources may be configured and sent to WD 22, one CSI-RS resource for each TRP, such as Fig.19 As shown. WD 22 may be configured to measure CSI based on two CSI-RS resources and report CSI to network node 16 via one or both TRPs. CSI may include one or more of the following: precoding matrix indicator (PMI), rank indicator (RI), one or more channel quality indicators (CQI), and CSI-RS resource indicator (CRI). CSI may be reported per CSI subband. Co-phase coefficients w1 and w2 may be measured and reported as part of PMI or as separate parameters.

[0157] In order to maintain the existing CSI subband size for CSI feedback, in some embodiments, the delay difference between the TRPs is pre-compensated so that the signals from the two TRPs arrive at WD 22 simultaneously. This can be achieved by applying a time advance τ to s(t) at TRP2, or a time delay τ to s(t) at TRP1, or a time advance τ / 2 to s(t) at TRP2 and a time delay τ / 2 to s(t) at TRP1. In an OFDM system, delay pre-compensation can be achieved by applying a phase rotation to the signal to be sent in each subcarrier. Fig. 20An example is shown in FIG. 1 , where the signal s(n) to be transmitted on the nth subcarrier is multiplied by s(n) before being transmitted from TRP2. And f n is the transmission frequency of the nth subcarrier.

[0158] With delay pre-compensation, the frequency-dependent phase terms in the desired in-phase coefficients w1 and w2 can be eliminated, and the existing CSI / PMI subband size can be used for CSI feedback.

[0159] The delay difference between TRPs (e.g., τ=τ2-τ1) may be reported by WD 22 based on a DL signal such as a TRS, CSI-RS, or DMRS. WD 22 may alternatively report the delay difference of each TRP relative to a common time reference at WD 22, e.g., τ1 and τ2. For example, consider two CSI-RS in a time slot corresponding to two TRPs, where CSI-RS#1 starts at the 4th symbol within the time slot and CSI-RS#2 starts at the 8th symbol within the time slot. The actual arrival time of CSI-RS#1 or CSI-RS#2 may be earlier or later than the expected symbol start time of WD 22. Then, when calculating the delay difference of the corresponding TRPs, the expected start time of the corresponding CSI-RS within the time slot is used as the common time reference. In another embodiment, the network node 16 may measure the time difference between TRPs based on an UL signal (such as SRS, DMRS) transmitted by WD 22. See. Fig.21 .

[0160] In another embodiment, in order to enable CJT with actual w1 and w2 feedback delays in the presence of transmit frequency differences between TRPs, frequency pre-compensation may be applied at the TRPs so that the transmit frequencies from all TRPs are the same at WD 22. This may be accomplished by applying frequency correction at each TRP except for a reference TRP (e.g., TRP#1 in the above example) so that the frequencies from all TRPs are aligned with the frequency of the reference TRP. With frequency pre-compensation, the time-correlated components in the in-phase coefficients w1 and w2 may be eliminated, and the in-phase coefficients measured once may be applied at a later time if the channel remains unchanged during that time period.

[0161] The frequency difference between TRPs may be measured and reported based on a TRP-specific reference signal such as a TRS by WD 22. Alternatively, the frequency difference between TRPs may be measured by a network node-based UL signal such as a sounding reference signal (SRS) or DMRS received at the TRP.

[0162] In some embodiments, delay and / or frequency precompensation may be applied to both CSI-RS and PDSCH, including associated DMRS. Since the delay difference may be different for different WDs, and different WDs may also experience different Doppler shifts, delay and frequency precompensation of CSI-RS is beneficial to WD 22-specific CSI-RS (such as aperiodic CSI-RS).

[0163] In some embodiments, delay and frequency precompensation are applied to PDSCH and associated DMRS, while only frequency precompensation is applied to CSI-RS. In this case, the delay dependent component may be removed at WD 22 before calculating CSI. Fig. 20 An example is shown in FIG. 1 , where the channels associated with CSI-RS#1 and CSI-RS#2 are and CSI calculation can be based on H1 and H2 only, and does not use and Because they will be pre-compensated for PDSCH and DMRS. When WD 22 removes the delay related components τ1 and τ2, these components or equivalent parameters can be reported by WD 22 together with CSI for delay pre-compensation of PDSCH and DMRS. The benefit of this embodiment is that the delay or delay difference between TRPs can be reported together with CSI, and no separate measurement and feedback for the delay / delay difference is required.

[0164] QCL signaling with precompensation

[0165] Whether delay and / or frequency precompensation is applied to CSI-RS, PDSCH, and DMRS should be signaled to WD22 so that appropriate actions can be taken. For example, if PDSCH and associated DMRS are delay precompensated, but the associated QCL source RS is not delay precompensated, WD 22 cannot derive the average delay of DMRS based on QCL source RS. Similarly, if PDSCH and associated DMRS are frequency precompensated, but the associated QCL source RS is not frequency precompensated, WD 22 cannot derive the frequency shift of DMRS based on QCL source RS.

[0166] In order to signal the network that delay and frequency pre-compensation has been performed, in some embodiments, a new QCL type may be introduced so that the average delay and / or frequency offset is not included in the new QCL type. For example, QCL-TypeX for {Doppler spread, delay spread} may be introduced to indicate the QCL relationship between the delay and frequency pre-compensated PDSCH and the TRS as the QCL source RS. In another example, QCL-TypeY for {average delay, delay spread, Doppler spread} may be introduced to indicate the QCL relationship between the frequency pre-compensated CSI-RS and the TRS as the QCL source RS. In this case, when pre-compensation has been applied to the PDSCH or CSI-RS, a TCI state with one of the new QCL types may be indicated to the PDSCH or CSI-RS resource.

[0167] 'QCL-TypeX': {Doppler spread, delay spread}; and / or

[0168] 'QCL-TypeY': {Doppler spread, delay spread, average delay}.

[0169] In some embodiments, delay and / or frequency precompensation may be implicitly indicated. For example, one of a plurality of TRPs may be used as a reference TRP, and the delays and frequency offsets of the other TRPs relative to the reference TRP are measured and precompensated. In this case, the reference TRP is not precompensated. In some embodiments, the reference TRP is always associated with the first TCI state activated for the TCI code point in the DCI. When the TCI code point is indicated to WD 22 in the DCI scheduling the PDSCH, in some embodiments, WD 22 may assume that a portion of the PDSCH transmitted from the TRP associated with the first TCI state indicated in the TCI code point is not precompensated, while the remainder of the same PDSCH transmitted from the remaining TRPs is precompensated.

[0170] Fig. 22 An example is shown in FIG, where the first TCI state (TCI state #x) is the reference TCI state and the associated PDSCH / DMRS is not pre-compensated, while the PDSCH / DMRS associated with the other two TCI states #y and #z are pre-compensated. WD22 can derive the average delay and Doppler shift based only on the RS specified in TCI state #x.

[0171] In some embodiments, the reference TRP is associated with a TCI state with a lower TCI state ID among the TCI states activated for the TCI code point in the DCI. When the TCI code point is indicated to WD 22 in the DCI that schedules the PDSCH, in some embodiments, WD 22 assumes that a portion of the PDSCH transmitted from the TRP associated with the TCI state with a lower TCI state ID among the TCI states indicated in the TCI code point is not pre-compensated, while the remaining portion of the same PDSCH transmitted from the remaining TRP is pre-compensated.

[0172] In some embodiments, the reference TRP is associated with a TCI state having a higher TCI state ID among the TCI states activated for the TCI code point, and in some embodiments, WD 22 assumes that a portion of the PDSCH transmitted from the TRP associated with the TCI state having a higher TCI state ID among the TCI states indicated in the TCI code point is not pre-compensated, while the remaining portion of the same PDSCH transmitted from the remaining TRPs is pre-compensated.

[0173] In the case of multiple aperiodic CSI-RS resources in a CSI-RS resource set configured for CJT CSI measurement and reporting, in some embodiments, the first CSI-RS resource is a reference CSI-RS resource and is not precompensated, while the remaining CSI-RS resources in the resource set are precompensated and thus derive {Doppler spread, delay spread} characteristics only from the corresponding QCL source RS. Whether precompensation is applied to the CSI-RS can be explicitly configured in the associated aperiodic CSI triggering state, or implicitly indicated when the CJT CSI is triggered.

[0174] In some scenarios, the TRPs involved in the CJT of WD 22 may be different at different times due to movement of WD 22 and / or channel changes. Typically, the TCI state associated with the TRP transmitting the PDSCH may be indicated to WD 22 for determining channel filter parameters. For example, in the case of 4 TRPs, in a scheduling cluster where CSI is measured and fed back, for a CJT PDSCH transmission that includes transmissions from a single TRP, 15 TCI code points may be required to signal different combinations of TRPs. For implicit signaling and to support all possible combinations, 32 TCI code points may be required.

[0175] With delay and frequency pre-compensation, the average delay and frequency from different TRPs are almost the same. In addition, in a homogeneous network with uniformly distributed TRPs, the difference in delay and Doppler spread between TRPs is also small. Therefore, in some embodiments, the TCI code point may contain only the TCI state associated with the reference TRP. Therefore, from the perspective of the WD receiver, CJT-based PDSCH from multiple TRPs is the same as PDSCH transmission from a single TRP.

[0176] In some embodiments, for CJT-based PDSCH, a TCI codepoint containing TCI states associated with all TRPs is configured for CJT, regardless of the actual TRP transmitting the PDSCH. For example, when 4 TRPs are in a cluster of potential CJTs, the following TCI codepoints may be activated for implicit signaling:

[0177] TCI status {a, b, c, d};

[0178] TCI status {b, c, d, a};

[0179] TCI status {c, d, a, b}; and / or

[0180] TCI status {d, a, b, c}.

[0181] Among them, TCI states a, b, c and d are associated with the first to fourth TRPs respectively.

[0182] For CSI-RS, when delay and frequency pre-compensation is applied, one of the CSI-RS resources in the CSI-RS resource set can be a reference CSI-RS resource and is not pre-compensated. Other CSI-RS resources can be pre-compensated so that their delays and transmission frequencies are aligned with the reference CSI-RS resources. The reference CSI-RS resource can be configured with a QCL typeA source RS, while other CSI-RS resources are configured with a QCL typex (i.e., {Doppler spread, delay spread}) RS. In addition, the QCL RS for the reference CSI-RS resource can be configured as a QCL type C (i.e., {Doppler shift, average delay}) RS for other CSI-RS resources.

[0183] Alternatively, the reference CSI-RS resource may be implicitly indicated. For example, when CJT-based CSI feedback is configured, the first CSI-RS resource in the SRS resource set may be a reference CSI-RS resource.

[0184] Although the above discussion focuses on PDSCH or CSI-RS, the same idea can be applied to other DL signals.

[0185] In addition, TRP can be associated with CSI-RS resources in a CSI-RS resource set, TCI status, DL reference signals such as TRS, etc.

[0186] Some embodiments may include one or more of the following.

[0187] A method for coherent joint transmission of PDSCH from multiple TRPs to WD 22 in WD 22 is disclosed. The method may include one or more of the following:

[0188] Pre-compensate for the delay and / or frequency difference between TRPs of the PDSCH before applying a set of in-phase coefficients to the PDSCH across TRPs;

[0189] • Delay and / or frequency difference is measured and reported by the WD 22 based on the DL reference signal, or measured by the network node 16 based on the UL signal based on the TRP:

[0190] o A reference TRP (or reference signal) among a plurality of TRPs (or reference signals) may be explicitly or implicitly indicated to WD22, and the delay and / or frequency difference is relative to the reference TRP (or reference signal);

[0191] The in-phase coefficients are measured and reported by WD 22 based on multiple CSI-RS resources, one for each TRP;

[0192] o The in-phase coefficient can be part of the CSI feedback;

[0193] o Pre-compensation may also be applied to CSI-RS resources; and / or

[0194] · By introducing one or more new QCL types to explicitly or implicitly indicate to the WD 22 the TRP or associated DL reference signal for which the PDSCH or CSI-RS resource is pre-compensated, so that the WD 22 does not derive certain channel characteristics based on the QCL source RS for PDSCH or CSI-RS reception.

[0195] A method for coherent joint transmission of DL signals from multiple TRPs to WD 22 in a network node 16 may include one or more of the following:

[0196] Obtaining a delay and / or frequency difference between each of the plurality of TRPs and a reference TRP that is one of the plurality of TRPs;

[0197] Obtain CSI feedback from WD 22, where the CSI includes a PMI for each subband indicating a joint antenna precoder across multiple TRPs, and the precoder includes a set of co-phase coefficients, one per TRP;

[0198] Applying delay and / or frequency pre-compensation to the DL signal before applying antenna precoding to the signal in each sub-band;

[0199] o wherein delay precompensation is applying a time delay or a time advance (or equivalently, a phase shift at each subcarrier in the frequency domain) at each of a plurality of TRPs based on the obtained delay difference so that the DL signals from the TRPs arrive at the WD 22 simultaneously;

[0200] o wherein frequency precompensation is applying a frequency correction at each of a plurality of TRPs based on the obtained frequency difference so that DL signals from the TRPs arrive at the WD 22 at the same frequency;

[0201] Applying antenna precoding to the pre-compensated DL signal at multiple TRPs per subband;

[0202] Explicitly signaling QCL information for pre-compensated DL signals with one or more new QCL types without including average delay and / or Doppler / frequency shift;

[0203] Implicitly signaling the QCL information for the pre-compensated DL signal:

[0204] o linking the reference TRP that is not pre-compensated to the first TCI state activated in each TCI codepoint;

[0205] o For the rest of the TCI states TRP is associated, PDSCH is pre-compensated (UE) on TPR.

[0206] A method of receiving DL signals from multiple TRPs may include one or more of the following:

[0207] receiving a configuration for CSI feedback for coherent joint transmission, wherein the configuration includes a plurality of CSI-RS resources, one for each TRP, and wherein a Doppler shift and an average time delay for all CSI-RS resources indicate a common QCL source reference signal;

[0208] Receive a request for CSI feedback based on the configuration;

[0209] Calculating CSI according to the configuration, wherein the CSI includes a PMI for each subband indicating a joint antenna precoder across multiple TRPs, the joint antenna precoder including a set of common phase coefficients between the TRPs;

[0210] · receiving a DCI format for scheduling a PDSCH, wherein the DCI format indicates a plurality of TCI states; and / or

[0211] · PDSCH is received according to the TCI state, where only one TCI state is used to derive the "Doppler shift" and "average delay" of PDSCH reception.

[0212] Some embodiments may include one or more of the following:

[0213] Embodiment A1. A network node configured to communicate with a wireless device WD, the network node being configured to and / or comprising a radio interface and / or comprising a processing circuit configured to:

[0214] Receiving a precoder matrix indicator PMI for each subband from the WD, which indicates a joint antenna precoder for multiple transmission reception points TRP;

[0215] applying one of delay and frequency pre-compensation to the downlink signal; and

[0216] Antenna precoding is applied to the precompensated downlink signal in each subband based on the indicated joint antenna precoder.

[0217] Embodiment A2. The network node of embodiment A1, wherein one of delay and frequency precompensation is based at least in part on a time delay between TRPs.

[0218] Embodiment A3. A network node of any of embodiments A1 and A2, wherein applying one of delay and frequency precompensation comprises applying one of delay and frequency precompensation to multiple TRPs.

[0219] Embodiment A4. The network node of any of Embodiments A1-A3, wherein the network node, the radio interface, and / or the processing circuitry is further configured to transmit quasi-co-located QCL information to the WD.

[0220] Embodiment A5. A network node of any embodiment of Embodiments A1-A4, wherein the network node, the radio interface and / or the processing circuit are further configured to link a first TRP to a first transmission configuration indicator TCI state and associate a set of remaining TCI states with other TRPs.

[0221] Embodiment B1. A method implemented in a network node configured to communicate with a wireless device WD, the method comprising:

[0222] Receiving a precoder matrix indicator PMI for each subband from the WD, the indicator indicating a joint antenna precoder for multiple transmission reception points TRP;

[0223] applying one of delay and frequency pre-compensation to the downlink signal; and

[0224] Antenna precoding is applied to the precompensated downlink signal in each subband based on the indicated joint antenna precoder.

[0225] Embodiment B2. The method of embodiment B1, wherein one of the delay and frequency precompensation is based at least in part on a time delay between TRPs.

[0226] Embodiment B3. The method of any of embodiments B1 and B2, wherein applying one of delay and frequency precompensation comprises applying one of delay and frequency precompensation to multiple TRPs.

[0227] Embodiment B4. The method of any of Embodiments B1-B3, further comprising transmitting quasi co-sited QCL information to the WD.

[0228] Embodiment B5. The method of any embodiment of embodiments B1-B4, the method also including linking a first TRP to a first transmission configuration indicator TCI state, and associating a set of remaining TCI states with other TRPs.

[0229] Embodiment C1. A wireless device (WD) configured to communicate with a network node, the WD configured to and / or comprising a radio interface and / or processing circuitry configured to:

[0230] pre-compensating one of a delay difference and a frequency difference between a plurality of transmission reception points TRP of a physical downlink shared channel PDSCH; and

[0231] A set of in-phase coefficients are applied to the PDSCH of TRP.

[0232] Embodiment C2. The WD of Embodiment C1, wherein one of the delay difference and the frequency difference is determined based at least in part on measurements at the WD.

[0233] Embodiment C3. The WD of Embodiment C1, wherein one of the delay difference and the frequency difference is determined based at least in part on measurements at a network node.

[0234] Embodiment C4. The WD of any of Embodiments C1-C3, wherein one of the delay difference and the frequency difference is based at least in part on a reference signal associated with a reference TRP.

[0235] Embodiment C5. The WD of any of Embodiments C1-C4, wherein the WD, the radio interface, and / or the processing circuitry is further configured to determine a set of channel characteristics based at least in part on the quasi co-location type.

[0236] Embodiment C6. The WD of any of Embodiments C1-C5, wherein the WD, the radio interface, and / or the processing circuitry is further configured to transmit the in-phase coefficient to a network node.

[0237] Embodiment D1. A method implemented in a wireless device (WD) configured to communicate with a network node, the method comprising:

[0238] pre-compensating one of a delay difference and a frequency difference between a plurality of transmission reception points TRP of a physical downlink shared channel PDSCH; and

[0239] A set of in-phase coefficients are applied to the PDSCH of TRP.

[0240] Embodiment D2. The method of Embodiment D1, wherein one of the delay difference and the frequency difference is determined based at least in part on measurements at the WD.

[0241] Embodiment D3. The method of Embodiment D1, wherein one of the delay difference and the frequency difference is determined based at least in part on measurements at a network node.

[0242] Embodiment D4. The method of any of embodiments D1-D3, wherein one of the delay difference and the frequency difference is based at least in part on a reference signal associated with a reference TRP.

[0243] Embodiment D5. The method of any of Embodiments D1-D4, further comprising determining a set of channel characteristics based at least in part on the quasi co-location type.

[0244] Embodiment D6. The method of any of embodiments D1-D5, further comprising transmitting an in-phase coefficient to a network node.

[0245] As will be appreciated by those skilled in the art, the concepts described herein may be embodied as methods, data processing systems, computer program products, and / or computer storage media storing executable computer programs. Thus, the concepts described herein may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware aspects, all of which are collectively referred to herein as "circuits" or "modules". Any process, step, action, and / or functionality described herein may be performed and / or associated with a corresponding module, which may be implemented in software and / or firmware and / or hardware. In addition, the present disclosure may take the form of a computer program product on a tangible computer-usable storage medium having a computer program code embodied in the medium that may be executed by a computer. Any suitable tangible computer-readable medium may be utilized, including a hard disk, a CD-ROM, an electronic storage device, an optical storage device, or a magnetic storage device.

[0246] Some embodiments are described herein with reference to flowchart illustrations and / or block diagrams of methods, systems, and computer program products. It will be understood that each frame of the flowchart illustration and / or block diagram and the combination of frames in the flowchart illustration and / or block diagram can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer (thereby creating a special-purpose computer), a special-purpose computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device create a component for implementing the function / action specified in one or more flowcharts and / or block diagram frames.

[0247] These computer program instructions may also be stored in a computer-readable memory or storage medium, which can direct a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture including instruction components, which implement the functions / actions specified in one or more flowcharts and / or block diagrams.

[0248] The computer program instructions may also be loaded onto a computer or other programmable data processing device to cause a series of operable steps to be performed on the computer or other programmable device to produce a computer-implemented process, so that the instructions executed on the computer or other programmable device provide steps for implementing the functions / actions specified in one or more flowcharts and / or block diagram blocks.

[0249] It is to be understood that the functions / actions indicated in the blocks may not occur in the order indicated in the operational diagrams. For example, two blocks shown in succession may actually be executed substantially concurrently, or the blocks may sometimes be executed in the reverse order, depending on the functionality / actions involved. Although some of the diagrams in the figures include arrows on communication paths to illustrate the primary direction of communication, it is to be understood that communication may occur in the opposite direction of the arrows depicted.

[0250] Computer program code for carrying out operations of the concepts described herein may be used in languages ​​such as Python, The computer program code for performing the operations of the present disclosure may be written in an object-oriented programming language such as C++ or C++. However, the computer program code for performing the operations of the present disclosure may also be written in a conventional procedural programming language such as the "C" programming language. The program code may be executed entirely on the user's computer, partially on the user's computer, as an independent software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer. In the latter scenario, the remote computer may be connected to the user's computer via a local area network (LAN) or a wide area network (WAN), or a connection may be established with an external computer (e.g., by using the Internet of an Internet Service Provider).

[0251] In conjunction with the above description and the accompanying drawings, many different embodiments have been disclosed herein. It will be understood that it would be overly repetitive and confusing to literally describe and illustrate every combination and subcombination of these embodiments. Thus, all embodiments can be combined in any manner and / or combination, and this specification including the accompanying drawings should be interpreted as constituting a complete written description of all combinations and subcombinations of the embodiments described herein and the manner and process of making and using them, and should support claims to any such combination or subcombination.

[0252] Those skilled in the art will appreciate that the embodiments described herein are not limited to what has been specifically shown and described herein above. In addition, unless otherwise mentioned above, it should be noted that all drawings are not to scale. Various modifications and variations are possible in view of the above teachings without departing from the scope of the appended claims.

Claims

1. A network node (16) configured to communicate with a wireless device WD (22), the network node (16) being configured for coherent joint transmission (CJT) of a downlink (DL) channel to the WD (22) via a first transmission and reception point (TRP) and a second TRP in the same time and frequency resources, the network node (16) comprising: A radio interface (62), the radio interface (62) being configured to: transmitting a first reference signal RS to the WD (22) through the first TRP, and transmitting a second RS to the WD (22) through the second TRP; receiving, from the WD (22), information at the WD (22) related to at least one of a time delay difference and a frequency difference between the first TRP and the second TRP, wherein the second TRP is a reference TRP; transmitting the DL channel with at least one of delay pre-compensation and frequency pre-compensation to the WD (22) through the first TRP and transmitting the DL channel without delay and frequency pre-compensation to the WD (22) through the second TRP; and transmitting to the WD (22) quasi co-located QCL information indicating whether the DL channel transmitted from each of the first TRP and the second TRP is pre-compensated; and A processing circuit (68) that communicates with the radio interface (62) and is configured to pre-compensate the downlink channel transmitted to the WD (22) via the first TRP based on at least one of the received time delay difference and frequency difference.

2. The network node (16) according to claim 1, wherein: The DL channel is the Physical Downlink Shared Channel PDSCH.

3. The network node (16) according to any one of claims 1 and 2, wherein: The QCL information is included in a DL control information DCI format that schedules the DL channel.

4. The network node (16) according to claim 3, wherein: The QCL information of the DL channel transmitted from the first TRP is included in a first transmission configuration indicating a TCI state, and the QCL information of the DL channel transmitted from the second TRP is included in a second transmission configuration indicating a TCI state, and the first TCI state and the second TCI state are indicated in the TCI code point of the TCI field in the downlink control information DCI.

5. The network node (16) according to claim 4, wherein: The QCL information in the first TCI state includes both an average delay characteristic and a Doppler shift characteristic, whereas the QCL information in the second TCI state does not include any one of the average delay characteristic and the Doppler shift characteristic.

6. The network node (16) according to any one of claims 4 and 5, wherein: The first TCI state and the second TCI state are indicated in one of an implicit and an explicit manner.

7. The network node (16) according to any one of claims 4 and 5, wherein: Only the first TCI state is indicated in the TCI code point in the DCI.

8. The network node (16) according to any one of claims 1 to 7, wherein: The delay precompensation is performed by applying one of a time advance and a time delay to the DL channel.

9. The network node (16) according to any one of claims 1 to 8, wherein: The frequency pre-compensation is performed by applying a frequency correction to the DL channel.

10. The network node (16) according to any one of claims 1 to 9, wherein: The QCL information also indicates one of delay pre-compensation, frequency pre-compensation, both delay and frequency pre-compensation, and no pre-compensation.

11. The network node (16) according to any one of claims 1 to 10, wherein: At least one of the delay pre-compensation and the frequency pre-compensation is performed by applying a phase rotation in each sub-carrier of the DL channel or signal.

12. The network node (16) according to any one of claims 1 to 11, wherein: The radio interface (62) is also configured to receive channel state information CSI feedback from the WD (22), the CSI feedback comprising a precoding matrix indicator PMI, the PMI indicating a first precoding matrix of the DL channel from the first TRP and indicating a second precoding matrix of the DL channel from the second TRP.

13. The network node (16) according to any one of claims 1 to 12, wherein: The first RS and the second RS are channel state information reference signals CSI-RS.

14. The network node (16) according to any one of claims 1 to 12, wherein: The first RS and the second RS are tracking reference signals TRS.

15. The network node (16) according to any one of claims 1 to 14, wherein: The time delay difference and the frequency difference are reported together with channel state information CSI.

16. The network node (16) according to any one of claims 1 to 15, wherein: At least one of the time delay difference and the frequency difference is obtained by the network node (16) based at least in part on uplink measurements of uplink reference signals.

17. A method in a network node (16) configured to communicate with a wireless device WD (22), the network node (16) being configured for coherent joint transmission (CJT) of a downlink (DL) channel to the WD (22) via a first transmission and reception point (TRP) and a second TRP in the same time and frequency resources, the method comprising: transmitting (S144) a first reference signal RS to the WD (22) through the first TRP and transmitting (S144) a second RS to the WD (22) through the second TRP; receiving (S146) from the WD (22) information at the WD (22) related to at least one of a time delay difference and a frequency difference between the first TRP and the second TRP, wherein the second TRP is a reference TRP; transmitting (S148) the DL channel with at least one of delay pre-compensation and frequency pre-compensation to the WD (22) through the first TRP and transmitting (S148) the DL channel without delay and frequency pre-compensation to the WD (22) through the second TRP; transmitting (S150) to the WD (22) quasi co-located QCL information indicating whether the DL channel transmitted from each of the first TRP and the second TRP is pre-compensated; and Based on at least one of the received time delay difference and frequency difference, pre-compensation (S152) is performed on the downlink channel transmitted to the WD (22) through the first TRP.

18. The method according to claim 17, wherein: The DL channel is the Physical Downlink Shared Channel PDSCH.

19. The method according to any one of claims 17 and 18, wherein: The QCL information is included in a DL control information DCI format that schedules the DL channel.

20. The method according to claim 19, wherein: The QCL information of the DL channel transmitted from the first TRP is included in a first transmission configuration indicating a TCI state, and the QCL information of the DL channel transmitted from the second TRP is included in a second transmission configuration indicating a TCI state, and the first TCI state and the second TCI state are indicated in the TCI code point of the TCI field in the downlink control information DCI.

21. The method according to claim 20, wherein: The QCL information in the first TCI state includes both an average delay characteristic and a Doppler shift characteristic, whereas the QCL information in the second TCI state does not include any one of the average delay characteristic and the Doppler shift characteristic.

22. The method according to any one of claims 20 and 21, wherein: The first TCI state and the second TCI state are indicated in one of an implicit and an explicit manner.

23. The method according to any one of claims 20 and 21, wherein: Only the first TCI state is indicated in the TCI code point in the DCI.

24. The method according to any one of claims 17 to 23, wherein: The delay precompensation is performed by applying one of a time advance and a time delay to the DL channel.

25. The method according to any one of claims 17 to 24, wherein: The frequency pre-compensation is performed by applying a frequency correction to the DL channel.

26. The method according to any one of claims 17 to 25, wherein: The QCL information also indicates one of delay pre-compensation, frequency pre-compensation, both delay and frequency pre-compensation, and no pre-compensation.

27. The method according to any one of claims 17 to 26, wherein: The at least one of the delay precompensation and the frequency precompensation is performed by applying a phase rotation in each subcarrier of the DL channel or signal.

28. The method according to any one of claims 17-27 further includes receiving channel state information CSI feedback from the WD (22), the CSI feedback including a precoding matrix indicator PMI, the PMI indicating a first precoding matrix of the DL channel from the first TRP and indicating a second precoding matrix of the DL channel from the second TRP.

29. The method according to any one of claims 17 to 28, wherein: The first RS and the second RS are channel state information reference signals CSI-RS.

30. The method according to any one of claims 17 to 28, wherein: The first RS and the second RS are tracking reference signals TRS.

31. The method according to any one of claims 17 to 30, wherein: The time delay difference and the frequency difference are reported together with channel state information CSI.

32. The method according to any one of claims 17 to 31, wherein: At least one of the time delay difference and the frequency difference is obtained by the network node (16) based at least in part on uplink measurements of uplink reference signals.

33. A wireless device WD (22) configured to communicate with a plurality of transmission reception points TRP at a network node, the WD (22) comprising: a radio interface (82) configured to receive, from the network node (16), a configuration for reporting at least one of a delay difference and a frequency difference between a first TRP and a second TRP based at least in part on a first reference signal RS and a second RS, the first RS and the second RS being transmitted from the first TRP and the second TRP, respectively; as well as a processing circuit (84) in communication with the radio interface (82) and configured to estimate at least one of the delay difference and the frequency difference based at least in part on the first RS and the second RS; The radio interface (82) is further configured to: reporting at least one of the estimated delay difference and the estimated frequency difference to the network node (16); receiving from the network node (16) a downlink channel scheduled by a downlink control information DCI format and quasi-co-located QCL information about the downlink channel in the DCI, the downlink channel being transmitted through both the first TRP and the second TRP; and The downlink channel is decoded according to the QCL information.

34. The WD (22) according to claim 33, wherein: The delay difference includes at least one of a timing difference and a propagation delay difference between the first TRP and the second TRP.

35. The WD (22) according to claim 33, wherein: The frequency difference includes at least one of a downlink carrier frequency difference and a downlink Doppler frequency difference between the first TRP and the second TRP.

36. The WD (22) according to any one of claims 33 to 35, wherein The downlink channel is a physical downlink shared channel PDSCH.

37. The WD (22) according to any one of claims 33 to 36, wherein The QCL information of the DL channel transmitted from the first TRP is included in a first transmission configuration indicating a TCI state, and the QCL information of the downlink channel transmitted from the second TRP is included in a second TCI state, and at least one of the first TCI state and the second TCI state is indicated in a TCI code point of the TCI field in the DCI.

38. The WD (22) according to claim 37, wherein The QCL information in the first TCI state includes Doppler shift, Doppler spread, average delay and delay spread.

39. The WD (22) according to any one of claims 37 and 38, wherein The QCL information in the second TCI state does not include at least one of a Doppler shift and an average delay.

40. The WD (22) according to any one of claims 37-39, wherein Only the first TCI state is indicated in the TCI field of the DCI, and QCL information included in the first TCI state is applied to a physical downlink shared channel PDSCH.

41. The WD (22) according to any one of claims 33 to 40, wherein The QCL information also indicates a QCL source reference signal.

42. The WD (22) according to any one of claims 33 to 41, wherein Decoding the DL channel according to the QCL information includes deriving channel characteristics indicated in the QCL information from an associated QCL source RS for a physical downlink shared channel (PDSCH), and performing channel estimation of the PDSCH using the channel characteristics.

43. The WD (22) according to any one of claims 33 to 42, wherein Each of the first RS and the second RS is a channel state information reference signal CSI-RS.

44. The WD (22) according to any one of claims 33-42, wherein Each of the first RS and the second RS is a tracking reference signal TRS.

45. A method in a wireless device WD (22), the wireless device WD (22) being configured to communicate with a network node (16) comprising a first transmission reception point TRP and a second TRP, the method comprising: receiving (S154) from the network node (16) a configuration for reporting at least one of a delay difference and a frequency difference between the first TRP and the second TRP based at least in part on a first reference signal RS and a second RS, the first RS and the second RS being transmitted from the first TRP and the second TRP, respectively; estimating (S156) at least one of the delay difference and the frequency difference based at least in part on the first RS and the second RS; reporting (S158) at least one of the estimated delay difference and the estimated frequency difference to the network node (16); receiving (S160) from the network node (16) a downlink channel scheduled by a downlink control information DCI format and quasi-co-located QCL information about the downlink channel in the DCI, the downlink channel being transmitted through both the first TRP and the second TRP; and The downlink channel is decoded according to the QCL information (S162).

46. ​​The method of claim 45, wherein: The delay difference includes at least one of a timing difference and a propagation delay difference between the first TRP and the second TRP.

47. The method of claim 45, wherein: The frequency difference includes at least one of a downlink carrier frequency difference and a downlink Doppler frequency difference between the first TRP and the second TRP.

48. The method according to any one of claims 45 to 47, wherein: The downlink channel is a physical downlink shared channel PDSCH.

49. The method according to any one of claims 45 to 48, wherein: The QCL information of the DL channel transmitted from the first TRP is included in a first transmission configuration indicating a TCI state, and the QCL information of the downlink channel transmitted from the second TRP is included in a second TCI state, and at least one of the first TCI state and the second TCI state is indicated in a TCI code point of the TCI field in the DCI.

50. The method of claim 49, wherein: The QCL information in the first TCI state includes Doppler shift, Doppler spread, average delay and delay spread.

51. The method according to any one of claims 49 and 50, wherein: The QCL information in the second TCI state does not include at least one of a Doppler shift and an average delay.

52. The method according to any one of claims 49 to 51, wherein: Only the first TCI state is indicated in the TCI field of the DCI, and QCL information included in the first TCI state is applied to a physical downlink shared channel PDSCH.

53. The method according to any one of claims 33 to 52, wherein: The QCL information also indicates a QCL source reference signal.

54. The method according to any one of claims 33 to 53, wherein: Decoding the DL channel according to the QCL information includes deriving channel characteristics indicated in the QCL information from an associated QCL source RS for the physical downlink shared channel PDSCH, and using the channel characteristics to perform channel estimation of the PDSCH.

55. The method according to any one of claims 33 to 54, wherein: Each of the first RS and the second RS is a channel state information reference signal CSI-RS.

56. The method according to any one of claims 33 to 54, wherein: Each of the first RS and the second RS is a tracking reference signal TRS.

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