Coherent joint transmission device, method and apparatus

Abstract

Embodiments of the present disclosure disclose a device, method, and apparatus for coherent joint transmission. A terminal device may receive a QCL source configuration from a network device. The QCL source configuration may indicate at least two transmit configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of a tracking reference signal (TRS). The terminal device may perform QCL characteristic prediction for the received TRS based on the QCL source configuration.

Description

[Technical Field]

[0001] FIELD Embodiments of the present disclosure relate generally to the field of communications, and more particularly to devices, methods, apparatus, and computer-readable storage media for coherent joint transmission. [Background technology]

[0002] In New Radio (NR) systems, cooperative transmission schemes can be used for multi-transmit and receive point (TRP) operation. Cooperative transmission schemes can be divided into two types: coherent joint transmission (CJT) and non-coherent joint transmission (NCJT), which depend on the mapping relationship between layers of transmitted data and multiple TRPs.

[0003] In a physical downlink shared channel (PDSCH) transmission within a CJT from multiple TRPs, the channel characteristics at the receiver of the terminal device may vary according to the precoder used for joint precoding. In addition, different numbers of TRPs may be involved in different PDSCH transmission instances. Therefore, the terminal device needs to predict the channel characteristics for PDSCH reception based on a set of TRP-specific tracking reference signals (TRSs), which may pose some challenges to current systems. Summary of the Invention [Means for solving the problem]

[0004] Generally, exemplary embodiments of the present disclosure provide a coherent joint transmission device, method, apparatus, and computer-readable storage medium.

[0005] In a first aspect, a terminal device is provided, which may include one or more transceivers; and one or more processors communicatively coupled to the one or more transceivers, the one or more processors configured to: receive a quasi-co-location (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmit configuration indication (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of a tracking reference signal (TRS); and perform QCL property prediction for the received TRS based on the QCL source configuration.

[0006] In a second aspect, a network device is provided, the network device may include one or more transceivers; and one or more processors communicatively coupled to the one or more transceivers, the one or more processors configured to: cause the network device to receive results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and cause the terminal device to transmit a quasi-co-location (QCL) source configuration, the QCL source configuration indicating at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of a tracking reference signal (TRS) based on the results of the measurements on the set of CSI-RS.

[0007] In a third aspect, a method implemented in a terminal device is provided, which may include: receiving a quasi-co-location (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmit configuration indication (TCI) states that indicate a reference signal from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS); and performing a QCL performance prediction for the received TRS based on the QCL source configuration.

[0008] In a fourth aspect, a method implemented in a network device is provided. The method may include: receiving results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and transmitting a quasi-co-location (QCL) source configuration to the terminal device, the QCL source configuration indicating at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0009] In a fifth aspect, an apparatus is provided for a terminal device, which may include: means for receiving a quasi-co-location (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmit configuration indication (TCI) states that indicate a reference signal from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS); and means for performing a QCL performance prediction for the received TRS based on the QCL source configuration.

[0010] In a sixth aspect, an apparatus of a network device is provided, which may comprise: means for receiving results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and means for transmitting a quasi-co-location (QCL) source configuration to the terminal device, the QCL source configuration indicating at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0011] In a seventh aspect, a terminal device is provided, the terminal device may include at least one processor; and at least one memory including computer program code, the at least one memory and the computer program code configured, by the at least one processor, to cause the terminal device to: receive a quasi-co-located (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmit configuration indication (TCI) states indicating reference signals from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS), and perform QCL characteristic prediction for the received TRS based on the QCL source configuration.

[0012] In an eighth aspect, a network device is provided, the network device may include at least one processor and at least one memory including computer program code configured, by the at least one processor, to: receive results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and cause the terminal device to transmit a quasi-co-location (QCL) source configuration, the QCL source configuration indicating at least two transmission configuration indication (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of a tracking reference signal (TRS) based on the results of the measurements on the set of CSI-RS.

[0013] In a ninth aspect, there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus to perform a method according to at least the third or fourth aspect.

[0014] In a tenth aspect, a computer program is provided that includes instructions that, when executed by an apparatus, cause the apparatus to at least: receive a quasi-co-location (QCL) source configuration from a network device; the QCL source configuration indicates at least two transmit configuration indication (TCI) states that indicate a reference signal from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS); and perform a QCL characteristic prediction for the received TRS based on the QCL source configuration.

[0015] In an eleventh aspect, a computer program is provided that includes instructions that, when executed by an apparatus, cause the apparatus to at least: receive results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and cause the terminal device to transmit a quasi-co-location (QCL) source configuration, the QCL source configuration indicating at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0016] In a twelfth aspect, a terminal device is provided, comprising: a receiving circuit configured to receive a quasi-co-location (QCL) source configuration from a network device, the QCL source configuration exhibiting at least two transmit configuration indication (TCI) states indicating a reference signal from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS); and a prediction circuit configured to perform a QCL characteristic prediction for the received TRS based on the QCL source configuration.

[0017] In a thirteenth aspect, a network device is provided, comprising: a receiving circuit configured to receive results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device; and a transmitting circuit configured to transmit a quasi-co-location (QCL) source configuration to the terminal device, the QCL source configuration indicating at least two transmit configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0018] It should be understood that this summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become more readily apparent through the following description.

[0019] Several exemplary embodiments will now be described with reference to the accompanying drawings. [Brief explanation of the drawings]

[0020] [Figure 1] FIG. 1 illustrates an exemplary communication network environment in which exemplary embodiments of the present disclosure may be implemented. [Figure 2] 10A-10C illustrate an example signaling process for coherent joint transmission, in accordance with some embodiments of the present disclosure. [Figure 3A] FIG. 1 illustrates an example scenario for CJT using multiple TRPs, according to an embodiment of the present disclosure. [Figure 3B] FIG. 1 illustrates an example scenario for CJT using multiple TRPs, according to an embodiment of the present disclosure. [Figure 3C] FIG. 1 illustrates an example scenario for CJT using multiple TRPs, according to an embodiment of the present disclosure. [Figure 4]4 illustrates an example schematic diagram 400 of receiving a CJT TRS and a DMRS, according to an embodiment of the present disclosure. [Figure 5] 5 is a flowchart of an example method 500 implemented in a terminal device, according to some embodiments of the present disclosure. [Figure 6] 6 is a flowchart of an example method 600 implemented in a network device, according to some embodiments of the present disclosure. [Figure 7] 7 is a simplified block diagram of a device 700 suitable for implementing embodiments of the present disclosure. [Figure 8] 8 illustrates an example of a computer readable medium 800 in the form of a CD or DVD. DETAILED DESCRIPTION OF THE INVENTION

[0021] Throughout the drawings, the same or similar reference numbers represent the same or similar elements.

[0022] The principles of the present disclosure will now be described with reference to several exemplary embodiments. It should be understood that these embodiments are set forth merely for illustrative purposes to aid those skilled in the art in understanding and implementing the present disclosure, without suggesting any limitation on the scope of the present disclosure. The disclosure described herein can be implemented in various ways other than those described below.

[0023] In the following description and claims, unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this disclosure belongs.

[0024] In this disclosure, references to "one embodiment," "one embodiment," "exemplary embodiment," and the like indicate that the described embodiment may include a particular feature, structure, or characteristic, but not all embodiments necessarily include that feature, structure, or characteristic. Moreover, such phrases do not necessarily refer to the same embodiment. Furthermore, when a particular feature, structure, or characteristic is described in connection with one embodiment, it is believed to be within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments, whether or not explicitly described.

[0025] While the terms "first," "second," etc. may be used herein to describe various elements, it should be understood that these elements should not be limited by these terms. These terms are used only to distinguish one element from another. For example, a first element may be referred to as a second element, and similarly, a second element may be referred to as a first element, without departing from the scope of the exemplary embodiments. As used herein, the term "and / or" includes any and all combinations of one or more of the listed items.

[0026] The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly dictates otherwise. It should be further understood that the terms "comprise," "comprising," "have," "having," "include," and / or "including," when used herein, specify the presence of stated features, elements, and / or components, etc., but do not exclude the presence or addition of one or more other features, elements, components, and / or combinations thereof.

[0027] As used in this application, the term "circuitry" may refer to one or more or all of the following: (a) hardware-only circuit implementation (e.g., implementation using only analog and / or digital circuitry); (b) Combinations of hardware circuitry and software, such as (where applicable): (i) a combination of analog and / or digital hardware circuitry and software / firmware; (ii) any portion of a hardware processor with software (including digital signal processors, software, and memory that work together to cause a device such as a mobile phone or server to perform various functions); (c) A hardware circuit and / or processor, such as a microprocessor or portion of a microprocessor, that requires software (e.g., firmware) for operation but may not be present when software is not required for operation.

[0028] This definition of circuit applies to all uses of the term within this application, including any claims. As a further example, the term circuit, as used herein, also covers simply a hardware circuit or processor (or processors), or portions of a hardware circuit or processor and its (or their) accompanying software and / or firmware implementations. The term circuit also covers, for example, and where applicable to certain claim elements, baseband or processor integrated circuits for mobile devices, or similar integrated circuits within servers, cellular network devices, or other computing or network devices.

[0029] As used herein, the term "communication network" refers to a network conforming to any suitable communication standard, such as Long Term Evolution (LTE), LTE-Advanced (LTE-A), Wideband Code Division Multiple Access (WCDMA), High-Speed ​​Packet Access (HSPA), or Narrowband Internet of Things (NB-IoT). Furthermore, communications between terminal devices and network devices in a communication network may be performed according to any suitable generation communication protocol, including, but not limited to, third-generation (3G), fourth-generation (4G), 4.5G, fifth-generation (5G) communication protocols, sixth-generation (6G) communication protocols, and / or later protocols. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development of communications, there are naturally future types of communication technologies and systems in which the present disclosure may be embodied. The scope of the present disclosure should not be considered limited to only the above-mentioned systems.

[0030] As used herein, the term "network device" refers to a node in a communication network through which a terminal device accesses the network and receives services therefrom. Depending on the applied terminology and technology, a network device may refer to a base station (BS) or an access point (AP), e.g., a Node B (NodeB or NB), evolved Node B (eNodeB or eNB), NR NB (also referred to as gNB), remote radio unit (RRU), radio header (RH), remote radio head (RRH), repeater, femto, pico, or other low-power node.

[0031] The term "terminal device" refers to any end device that may be capable of wireless communication. By way of example and not limitation, a terminal device may also be referred to as a communication device, user equipment (UE), subscriber station (SS), portable subscriber station, mobile station (MS), or access terminal (AT). Terminal devices may include, but are not limited to, mobile phones, cellular phones, smartphones, voice over IP (VoIP) phones, wireless local loop phones, tablets, wearable terminal devices, personal digital assistants (PDAs), portable computers, desktop computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback equipment, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop embedded equipment (LEE), laptop mounted equipment (LME), USB dongles, smart devices, wireless customer premises equipment (CPE), Internet of Things (IoT) devices, watches or other wearables, head-mounted displays (HMD), vehicles, drones, medical devices and applications (e.g., remote surgery), industrial devices and applications (e.g., robots and / or other wireless devices operating in industrial and / or automated processing chain contexts), customer electronics devices, devices operating on commercial and / or industrial wireless networks, and the like. In the following description, the terms “terminal device,” “communications device,” “terminal,” “user equipment,” and “UE” may be used interchangeably.

[0032] In the current NR system, multi-TRP operation has been introduced to improve the performance of the communication system. Cooperative transmission schemes can be used for multi-TRP. Depending on the mapping relationship between the layers of transmitted data and multiple transmitting / receiving points (TRPs), multi-TRP cooperative transmission schemes can be divided into two types: coherent joint transmission (CJT) and non-coherent joint transmission (NCJT).

[0033] In CJT, data transmitted by multiple TRPs are jointly beamformed, and the precoding matrices (relative phases) applied to different TRPs are adjusted so that data within the same layer can be coherently combined at the terminal device receiving the transmitted data. In other words, the subarrays of multiple TRPs are modeled as higher-dimensional antenna port arrays to achieve higher beamforming gain. CJT schemes typically have relatively high requirements for synchronization and coordination among multiple TRPs. However, in practical NR deployment environments, the coordination performance among TRPs is easily affected by several non-ideal factors, such as frequency deviation.

[0034] Beamforming may also be referred to as spatial filtering, directional transmission, or directional reception. Beamforming is a signal processing technique that may be used in a transmitting device and / or a receiving device to shape or steer an antenna beam along a spatial path between the transmitting device and the receiving device. Beamforming may rely on antenna elements of an antenna array for signals propagating in a particular orientation.

[0035] As used herein, the term "beam" may refer to a communication resource. Different beams may be considered as different resources. A beam may also be represented as a spatial filter. A technique for forming a beam may be a beamforming technique or another technique. The beamforming technique may be, in particular, a digital beamforming technique, an analog beamforming technique, or a hybrid digital / analog beamforming technique. A communication device (including a terminal device and a network device) may communicate with another communication device through one or more beams. A beam may include one or more antenna ports and may be configured for a data channel, a control channel, or the like. One or more antenna ports forming a beam may also be considered as an antenna port set. A beam may be configured by a set of resources or a set of resources for measurement, and a beam may be represented, for example, by a reference signal and / or associated resources for the reference signal. A beam may also be represented by a reference cell identifier or a resource identifier.

[0036] In NR, a terminal device may be provided with a reference signal (RS) via quasi-co-location (QCL) source information and may configure a channel prediction filter and associated parameters based on the RS to receive data transmissions (e.g., DMRS and PDSCH transmissions of PDSCH).

[0037] Two antenna ports are said to be quasi-colocated if the characteristics of the channel over which the codes on one antenna port are conveyed can be inferred from the channel over which the codes on the other antenna port are conveyed.

[0038] PDSCH transmissions in the CJT from multiple TRPs are based on joint precoding across all antenna ports of the TRPs involved in the CJT. Decisions regarding the downlink precoder and rank can be made dynamically by a scheduler for each CJT PDSCH transmission based on channel state information (CSI) reports and hybrid automatic repeat request (HARQ) feedback (inner loop link adaptation) from the terminal devices. Thus, the precoder can change from one PDSCH transmission instant to another.

[0039] Similarly, the experienced signal characteristics due to the combined effect of the wireless channel and the applied precoder in the terminal device may also change according to the applied precoder. In addition, different numbers of TRPs may be involved in different PDSCH transmissions. Therefore, the terminal device needs to predict the channel characteristics for PDSCH reception based on a set of TRP-specific tracking reference signals (TRSs), which change from one PDSCH transmission to another.

[0040] Currently, the relationship between a QCL source RS and a target signal is one-to-one, and multiple QCL source RSs are not associated with a single target signal. Therefore, it poses a challenge to predict channel characteristics for PDSCH reception based on a set of TRP-specific tracking reference signals (TRSs) that change from time to time. Therefore, a solution to enable channel characteristic prediction is needed.

[0041] In an embodiment of the present disclosure, a QCL source configuration is utilized to inform a terminal device of valid QCL sources to facilitate QCL performance prediction in coherent joint transmission. Specifically, according to an embodiment of the present disclosure, a terminal device receives a quasi-colocated (QCL) source configuration from a network device, and the QCL source configuration indicates at least two transmit configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of a tracking reference signal (TRS). The terminal device then performs QCL performance prediction for the received TRS based on the QCL source configuration.

[0042] In this solution, the QCL source configuration is used to indicate the valid QCL resources using a TCI state that can reflect both changes in the QCL resources and changes in the precoder in the CJT transmission, so that the terminal device can learn the relationship between the QCL resources and their respective uplink transmissions in the CJT transmission. Thus, the terminal device can predict the channel characteristics for PDSCH reception based on a set of TRP-specific tracking reference signals (TRS).

[0043] As used herein, the term "quasi-co-location (QCL)" may define a relationship between two antenna ports (or reference signals) at a terminal device. Two antenna ports may be referred to as QCL if the characteristics (e.g., large-scale channel characteristics) of the channel through which a code on one antenna port is conveyed can be inferred from the channel through which a code on the other antenna port is conveyed. There are four types of QCL information corresponding to RSs, including types A, B, C, and D, and the QCL information may be used by a terminal device to facilitate CJT PDSCH transmission. For example, a terminal device may use the QCL information and channel condition prediction for CSI acquisition.

[0044] Hereinafter, for illustrative purposes, the principles and exemplary embodiments of the present disclosure for channel information prediction will be described below with reference to Figures 1 to 8. However, it should be noted that these embodiments are provided to enable those skilled in the art to understand the inventive concepts of the present disclosure and to implement the solutions as proposed herein, and are not intended to limit the scope of the present application in any way.

[0045] 1 illustrates an exemplary communication network environment 100 in which exemplary embodiments of the present disclosure may be implemented. The communication network environment 100, which may be part of a communication network, includes terminal devices and network devices.

[0046] 1, communication network environment 100 may include a network device 110 and a terminal device 120. In some embodiments, network device 110 may include, but is not limited to, an NR NB (also referred to as a gNB), and terminal device 120 may include, but is not limited to, a user equipment (UE). Network device 110 may communicate with terminal device 120. In communication network environment 100, a link from network device 110 to terminal device 120 may be referred to as a downlink, while a link from terminal device 120 to network device 110 may be referred to as an uplink.

[0047] In the downlink, the network device 110 is a transmitting (TX) device (or transmitter), while the terminal device 120 is a receiving (RX) device (or receiver). In the uplink, the terminal device 120 is a transmitting TX device (or transmitter), while the first network device 110 is an RX device (or receiver). In some embodiments, the network device 110 and the terminal device 120 may communicate over a direct link / channel.

[0048] 1, the communication network environment 100 may support multi-TRP transmission. As illustrated in FIG. 1, the terminal device 120 may communicate with, for example, four TRPs, namely, TRPs 130-1, 130-2, 130-3, and 130-4 (collectively or individually referred to as TRPs 130). For purposes of illustration, TRP 130-1 may be referred to as the first TRP 130-1, TRP 130-2 may be referred to as the second TRP 130-2, TRP 130-3 may be referred to as the third TRP 130-3, and TRP 130-4 may be referred to as the fourth TRP 130-4.

[0049] Although four TRPs are shown in FIG. 1, it should be understood that the number of TRPs in the embodiments of the present disclosure is not limited to four, and any other number of TRPs may be used in the communication network environment 100.

[0050] In some embodiments, terminal device 120 may be served by multiple TRPs. The multiple TRPs may be associated with network device 110. For example, network device 110 may be associated with multiple TRPs to communicate with terminal device 120. For example, as shown in FIG. 1, network device 110 is associated with a first TRP 130-1, a second TRP 130-2, a third TRP 130-3, and a fourth TRP 130-4.

[0051] In some embodiments, some of the TRPs may be associated with a network device in a cell, and some of the TRPs may be associated with another network device in another cell. For example, network device 110 may be associated with first TRP 130-1 and second TRP 130-2, and another network device (not shown) may be associated with third TRP 130-3 and fourth TRP 130-4.

[0052] In some embodiments, a network device may be associated with multiple TRPs in different geographic locations to achieve better coverage. In alternative embodiments, a network device 110 may be associated with multiple TRPs distributed in the same geographic location to achieve relatively high communication speeds.

[0053] It should be understood that the number of terminal devices 120, the number of network devices 110, and the number of TRPSs 130 shown in communication network environment 100 in FIG. 1 are for illustrative purposes only, without any limitation on the scope of the present disclosure. In some exemplary embodiments, communication network environment 100 may include any number of terminal devices, any number of network devices, and / or any number of TRPs. Additionally, each network device 110 according to embodiments of the present disclosure may support any number of TRPs.

[0054] Furthermore, communications between devices in communication environment 100 may be implemented according to any suitable communications protocol, including, but not limited to, third generation (3G), fourth generation (4G), fifth generation (5G), sixth generation (6G), and the like cellular communications protocols, wireless local network communications protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and / or any other protocol now known or to be developed in the future. Further, the communications may utilize any suitable wireless communications technology, including, but not limited to: Code Division Multiple Access (CDMA), Frequency Division Multiple Access (FDMA), Time Division Multiple Access (TDMA), Frequency Division Duplex (FDD), Time Division Duplex (TDD), Multiple-Input Multiple-Output (MIMO), Orthogonal Frequency Division Multiple (OFDM), Discrete Fourier Transform spread OFDM (DFT-s-OFDM), and / or any other technology now known or to be developed in the future.

[0055] In some embodiments, the network device 110 transmits a QCL source configuration that indicates at least two transmission configuration indication (TCI) states from the network device. In some embodiments, the at least two TCI states indicate a reference signal from a valid QCL source for the CJT TRS. The terminal device 120 then performs a QCL performance prediction for the received TRS based on the QCL source configuration.

[0056] 2 illustrates an example signaling process 200 for coherent joint transmission according to some embodiments of the present disclosure. For purposes of discussion, process 200 will be described with reference to FIG. 1. Process 200 may involve network device 110 and terminal device 120 as shown in FIG. 1. More specifically, process 200 may involve terminal device 120, network device 110, and four TRPs 130-1 through 130-4 as illustrated in FIG. 1. In some embodiments, network device 110 may support multiple TRPs 130-1 through 130-4.

[0057] While only one terminal device 120 is shown in FIG. 2 , it should be understood that the network device 110 may communicate with two or more terminal devices. Similarly, while only one network device 110 is shown in FIG. 2 , there may be two or more network devices to support multiple TRPs, e.g., four TRPs. Additionally, while process 200 is described in conjunction with the communication network environment 100 of FIG. 1 , process 200 may be similarly applied to other communication network scenarios having similar QCL source configuration requirements. Furthermore, one or more operations in process 200 may be added, omitted, or modified, or the operations may also be performed in any suitable order without departing from the scope of the present disclosure.

[0058] In process 200, at 210, terminal device 120 may report capability information to network device 110. The capability information may indicate that terminal device 120 supports CJT TRS transmission and reception and CJT PDSCH transmission. Network device 110 may receive the capability information from terminal device 120 and configure terminal device 120 to perform CJT transmission and reception according to the capability information, which will be described in more detail below with respect to signaling process 200.

[0059] In some embodiments, at 222, network device 110 may transmit a CJT TRS resource configuration to terminal device 120 for configuration. CJT TRS resources include CSI-RS resources specifically designed for time-frequency tracking. In some embodiments, the CJT TRS resource configuration may include a periodic configuration, i.e., terminal device 120 may be configured with periodic TRS resources. For example, network device 110 associated with four TRPs 130-1 through 130-4 may be configured for terminal device 120 with multiple TRS resource sets, each having four periodic TRSs within a time slot.

[0060] In some embodiments, the network device 110 may transmit a CJT TRS resource configuration in a radio resource control (RRC) message. The TRS resource configuration may indicate one or more TRS resource sets, where each TRS resource set may include, for example, four periodic non-zero power channel state information reference signal (NZP CSI-RS) resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

[0061] In some embodiments, the network device 110 may transmit a TRS resource configuration in a downlink control information (DCI) message. The TRS resource configuration may indicate one or both of the identity of the NZP CSI-RS resource set or the identity of the NZP CSI-RS resources. For example, the TRS resource configuration may indicate the identity of the NZP CSI-RS resource set. In another example, the TRS resource configuration may indicate the identity of the NZP CSI-RS resources. As another example, the TRS resource configuration may indicate both the identity of the NZP CSI-RS resource set and the identity of the NZP CSI-RS resources.

[0062] In some embodiments, the CJT TRS resource configuration may include an aperiodic configuration, i.e., the terminal device 120 may be configured with aperiodic TRS resources. For example, for a network device 110 associated with four TRPs 130-1 through 130-4, multiple TRS resource sets, each having four aperiodic TRSs, may be configured for the terminal device 120. The network device 110 may transmit the aperiodic CJT TRS resource configuration following a TRP transmission configuration indication (TCI) state (described in more detail below). Alternatively, the network device 110 may transmit the aperiodic CJT TRS resource configuration without any TCI state.

[0063] In some embodiments, at 224, the network device 110 may transmit a TCI state configuration to the terminal device 120. The TCI state configuration indicates multiple possible TCI states for the terminal device, e.g., the TCI states of the TCI state configuration may correspond to multiple TRPs that the terminal device may support. The TCI states may be indicated by a medium access control (MAC) control element (CE) or DCI and may apply to CJT PDSCH reception at the terminal device 120.

[0064] Depending on the capabilities of the terminal device 120, one or more of the joint TCI states may be configured for the terminal device 120 to provide QCL information (e.g., QCL parameters) for reception of DMRS and PDSCH at the terminal device 120. In a scenario such as illustrated in FIG. 1, if the terminal device 120 can support four TRPs, the terminal device 120 may be configured with, for example, four TCI states.

[0065] In some embodiments, each TCI state in the TCI state configuration may indicate a reference signal from one valid QCL source. Thus, each TCI state may be associated with one TRS resource in the TRS resource configuration. Specifically, for N TRPs (N is an integer greater than 1), N TRS resources are configured for the terminal device 120, and each TRS may provide information related to the channel characteristics of the TRP. Thus, a TRP-specific QCL source RS may be provided by the TCI state and corresponding CSI-RS resource for each TRP-specific CSI-RS resource set for the purpose of CSI acquisition. For example, a QCL Type-A source RS may be provided for the TRS to acquire CSI acquisition and DMRS for PDSCH, and a QCL Type-D source RS may be provided for the TRS to acquire channel conditions and support beamforming.

[0066] In some embodiments, the QCL Source RS Type associated with a TRS resource may include the following format and parameters: - "Type A": {Doppler shift, Doppler spread, average delay, delay spread} - "Type B": {Doppler shift, Doppler spread} - "Type C": {Doppler shift, average delay} -"Type D": {Spatial Rx parameters}

[0067] It should be understood that these examples of QCL source RS types associated with TRS resources as described above are for illustrative purposes only, and that QCL source RS types associated with TRS resources may include other formats and / or parameters as technology develops.

[0068] In some embodiments, at 226, the network device 110 may transmit the CSI-RS resource configuration to the terminal device 120. The terminal device 120 may perform measurements on the CSI-RS and report results of the measurements on the set of CSI-RS to the network device 110, as shown at 230 of the signaling process 200.

[0069] At 240, the network device 110 may determine one or more CJT parameters for the CJT transmission based on results of the received measurements. In some embodiments, the one or more CJT parameters may include one or more of: a precoder for the CJT, a rank, or a modulation and coding scheme (MCS) for the CJT. It should be understood that these parameters are merely a few examples given for illustrative purposes only, and that the network device 110 may determine other parameters related to the CJT at 240.

[0070] In some embodiments, the network device 110 may transmit a transmission mode configuration to the terminal device 120, as shown at 242. In some embodiments, the transmission mode configuration may indicate a group of possible transmission modes including one or more of: a CJT mode, a non-coherent joint transmission (NCJT) mode, or a dynamic point selection mode. The terminal device 120 may be indicated a transmission mode and may transmit according to the selection of the transmission mode indicated by the network device 110.

[0071] In some embodiments, following transmission of the transmission mode configuration, the network device 110 may transmit a transmission mode indication to the terminal device 120, which may trigger the CJT mode. Specifically, the transmission mode indication is transmitted to the terminal device 120 when two or more QCL sources are enabled, and the transmission mode indication may indicate the type of joint transmission, i.e., whether the joint transmission type is CJT mode or NCJT mode. If it is CJT mode, a solution as described herein is performed; otherwise, a legacy solution may be applied.

[0072] At 244, the network device 110 transmits a QCL source configuration to the terminal device 120 based on the results of the measurements on the set of CSI-RS. The QCL source configuration may indicate at least two TCI states that indicate reference signals from valid QCL sources for the CJT of the TRS.

[0073] In some embodiments, the QCL source configuration may be indicated by a bitmap. In some embodiments, one bit in the bitmap is associated with one of multiple possible TCI states. The number of bits in the bitmap may be determined according to the number of multiple possible TCI states. For example, if there are four possible TCI states, a bitmap having a size of 4 is needed, with each bit corresponding to one TCI state and used to indicate whether the TCI state is activated and whether the associated QCL source is enabled. In some embodiments, the number of bits in the bitmap may be determined according to the number of multiple possible TRPs. For example, if there are four possible TRPs, a bitmap having a size of 4 is needed, with each bit corresponding to one TRP and used to indicate whether the TRP is a enabled QCL source.

[0074] In an alternative embodiment, a transmission mode indication may be transmitted to terminal device 120 following QCL source configuration when two or more QCL sources are enabled. In such a case, the transmission mode indication may indicate the type of joint transmission, i.e., whether the joint transmission type is CJT mode or NCJT mode.

[0075] A description of the QCL source configuration will now be provided in detail with reference to Figures 3A-3C, which illustrate an example scenario of multiple TRPs in a CJT according to an embodiment of the present disclosure. For purposes of clarity, the network devices associated with the four TRPs are not shown in Figures 3A-3C.

[0076] 3A, four TRPs are used in the CJT, and each TRP transmits a TRS to terminal device 120. Thus, a bitmap indicating the QCL source configuration may have four bits, which in this example may be, for example, "1111." The bitmap indicates that all four TCI states are configured for CJT transmission, and therefore all four TRPs associated with the four TCI states are valid QCL sources.

[0077] For example, the QCL source configuration may indicate, for example, a first TCI state corresponding to the first TRP 130-1, a second TCI state corresponding to the second TRP 130-2, a third TCI state corresponding to the third TRP 130-3, and a fourth TCI state corresponding to the fourth TRP 130-4. The indicated TCI states may include or indicate information about the reference signal from each enabled QCL source. For example, the first TCI state may indicate the reference signal from the first TRP 130-1, the second TCI state may indicate the reference signal from TRP 130-2, the third TCI state may indicate the reference signal from TRP 130-3, and the fourth TCI state may indicate the reference signal from TRP 130-4.

[0078] In some embodiments, each indicated reference signal from each valid source is provided with a TRP-specific TRS resource or resource set for purposes of CSI acquisition. For example, a QCL Type-A source RS may be provided for TRS to acquire CSI acquisition and DMRS for PDSCH, and a QCL Type-D source RS may be provided for another TRS to acquire channel conditions and support beamforming.

[0079] 3B, at different transmission times, three TRPs are used within the CJT to transmit TRSs to the terminal device 120. Thus, the bitmap indicating the QCL source configuration may be, for example, "1101," indicating that the illustrated three TRPs are valid QCL sources.

[0080] Specifically, the QCL source configuration may exhibit three TCI states, e.g., a first TCI state corresponding to the first TRP 130-1, a second TCI state corresponding to the second TRP 130-2, and a fourth TCI state corresponding to the fourth TRP 130-4. The exhibited TCI states may also indicate reference signals from the respective enabled sources. For example, the first TCI state may indicate a reference signal from the first TRP 130-1, the second TCI state may indicate a reference signal from the second TRP 130-2, and the fourth TCI state may indicate a reference signal from the fourth TRP 130-4.

[0081] Similarly, an indicated reference signal from each valid source is provided for each set of TRP-specific TRS for purposes of CSI acquisition by terminal device 110. For example, QCL Type A source RS may be provided for TRS to acquire CSI acquisition and DMRS for PDSCH, and QCL Type D source RS may be provided for another TRS to acquire channel conditions and support beamforming.

[0082] 3C, at a further transmission point in time, two TRPs are used within the CJT to transmit a TRS to the terminal device 120. Thus, the bitmap indicating the QCL source configuration may be, for example, "1001," indicating that two TRPs, namely, the first TRP 130-1 and the fourth TRP 130-4, are valid QCL sources.

[0083] Specifically, the QCL source configuration may exhibit two TCI states, e.g., a first TCI state corresponding to the first TRP 130-1 and a fourth TCI state corresponding to the fourth TRP 130-4. The exhibited TCI states may also indicate reference signals from the respective enabled sources. For example, the first TCI state may indicate a reference signal from the first TRP 130-1, and the fourth TCI state may indicate a reference signal from the fourth TRP 130-4.

[0084] Similarly, indicated reference signals from two respective valid sources are provided for each set of TRP-specific TRSs for purposes of CSI acquisition by terminal device 110. For example, QCL Type A source RSs may be provided for TRSs to acquire CSI acquisition and DMRS for PDSCH, and QCL Type D source RSs may be provided for other TRSs to acquire channel conditions and support beamforming.

[0085] Because all four TRPs are valid QCL sources for transmitting TRS as shown in FIG. 3A, the scenario shown in FIG. 3A may also be used in the initial configuration stage to configure terminal device 120 with a TRS resource configuration. In addition, when used in the initial configuration stage, the four TRPs may also transmit CSI-RS (not shown in FIG. 3A) to terminal device 120 for CSI acquisition. In addition, it should be understood that other signals and configurations communicated between TRPs and network device 120 may also be possible according to specific applications and requirements. These signals and configurations communicated between TRPs and network device 120 are not described in detail in FIG. 3A for the sake of simplicity.

[0086] In some embodiments, the network device 110 may activate an enabled QCL source either through a medium access control (MAC) control element (CE) or a DCI message. For example, the activation may be implemented by one or more code points. For example, a DCI message may configure a code point corresponding to a QCL source. Thus, by configuring a code point, the corresponding QCL source may be activated or deactivated.

[0087] In some embodiments, the bit width of the code points in the DCI may be configurable. For example, a code point of "00" may activate the second and fourth QCL sources, and a code point of "01" may activate the third and fourth QCL sources. A MAC CE may be used to activate valid sources in a manner similar to that described with respect to the DCI. For purposes of brevity, repeated descriptions will not be described in detail.

[0088] Referring back to FIG. 2 , at 246, a valid TRP may transmit a CJT TRS. The CJT TRS is associated with the indicated TCI state. At 250 of signaling process 200, terminal device 120 performs a QCL characteristic prediction for the received TRS based on the QCL source configuration. In some embodiments, the QCL characteristic prediction includes a prediction for one or more of: Doppler shift, Doppler spread, mean delay, delay spread, or spatial reception parameters. The QCL characteristic prediction may be used by terminal device 120 to set a channel prediction filter used for DMRS and PDSCH detection and reception.

[0089] At 260, network device 110 may transmit a schedule command for PDSCH transmission and transmit the DMRS and the scheduled PDSCH. Accordingly, terminal device 120 may receive a schedule command for PDSCH transmission and receive the DMRS and the scheduled PDSCH based on the QCL performance prediction.

[0090] In some embodiments, the scheduled CJT PDSCH and a demodulation reference signal (DMRS) associated with the scheduled CJT PDSCH may be received at the antenna port of the received TRS. For example, the CJT TRS may be transmitted using the same precoder as the DMRS associated with the layer of the scheduled PDSCH. That is, the CJT TRS has the antenna weight as the first layer of the PDSCH or the DMRS of the first layer of the scheduled PDSCH. Thus, the terminal device 120 may receive the DMRS and the scheduled CJT PDSCH associated with the DMRS at the antenna port of the received CJT TRS.

[0091] In some embodiments, when a PDSCH is scheduled within a DCI, it may determine the association of a TRS with a DMRS associated with the PDSCH. It is known that the DMRS is for demodulating the PDSCH, and therefore, it may be known from the DCI that schedules the PDSCH which DMRS is associated with the scheduled PDSCH. The most recent TRS received up to a predetermined number of time slots before the transmission of the scheduled CJT PDSCH may be determined as the associated TRS. In such a manner, the most recent TRS may be associated with the DMRS. In this embodiment, the TRS does not require explicit signaling (e.g., a separate DCI) to trigger, and therefore, the association may be defined in an implicit manner.

[0092] Alternatively, a separate trigger signaling (e.g., DCI) may be used to trigger the TRS. In such a case, for a scheduled PDSCH, the associated TRS may include the TRS that is last triggered by the TRS triggering indication and that is received up to a predefined number of time slots before the transmission of the scheduled CJT PDSCH. In this manner, the TRS may also be associated with the DMRS. In this solution, a separate trigger signaling is used to trigger the TRS, and thus this association is defined in an explicit manner.

[0093] It should be understood that by transmitting the TRS a predetermined number of time slots before transmitting the scheduled CJT PDSCH, the network device 110 may have a period of time to prepare for transmission to ensure accuracy of the transmission. Additionally, it should also be understood that any other scheme for determining the association of a CJT TRS with a DMRS may also be used herein.

[0094] For example, FIG. 4 illustrates an example schematic diagram 400 of receiving CJT TRS and DMRS according to an embodiment of the present disclosure. As shown in FIG. 4, three TRP-specific TRSs are used in CJT transmission. For example, the first TRP 130-1 transmits TRS#1, the second TRP 130-2 transmits TRS#2, and the fourth TRP 130-4 transmits TRP#4. The three CJT TRSs are received at corresponding antenna ports and measured by the terminal device at 440. QCL characteristics may be predicted based on measurements for the TRSs from the three valid TRPs. The terminal device 120 may further receive the DMRS of the PDSCH and the scheduled PDSCH associated with the DMRS at the antenna port of the received TRS (450), for example, using the same precoder also used by the terminal device 120 to receive the TRS.

[0095] Although three TRP-specific TRSs are shown in Figure 4, it should be understood that there may be other numbers of TRP-specific TRSs at different times. However, the operation is similar, but the number of valid TRPs is different. For the sake of brevity, detailed descriptions will not be provided in detail herein.

[0096] Advantageously, by receiving a QCL source configuration indicating at least two TCI states, the terminal device can learn a reference signal from a valid source for the CJT of the TRS, and the terminal device 120 can then perform QCL performance prediction based on the QCL source configuration. Thus, the CJT DMRS and CJT PDSCH can be received based on the prediction, and thus transmission performance and efficiency can be significantly improved.

[0097] 5 illustrates a flowchart of an example method 500 implemented in a terminal device (e.g., terminal device 120) according to some embodiments of the present disclosure. For purposes of discussion, method 500 will be described from the perspective of terminal device 120 with reference to FIG.

[0098] At 520, the terminal device 120 receives a quasi-co-location (QCL) source configuration from the network device, the QCL source configuration indicating at least two transmission configuration indication (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS).

[0099] In some embodiments, the QCL source configuration may be indicated by a bitmap, with one bit in the bitmap being associated with one of multiple possible TCI states.

[0100] At 540, terminal device 120 performs a QCL characteristic prediction for the received TRS based on the QCL source configuration. In some embodiments, the QCL characteristic prediction may include a prediction for one or more of: a Doppler shift, a Doppler spread, a mean delay, a delay spread, or spatial reception parameters.

[0101] In some embodiments, the terminal device 120 may receive a TRS resource configuration for QCL performance prediction of the CJT.

[0102] In some embodiments, the TRS resource configuration may be received in a radio resource control (RRC) message and may indicate one or more TRS resource sets, where each TRS resource set may include four periodic non-zero power channel state information reference signal (NZP CSI-RS) resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

[0103] In some embodiments, the TRS resource configuration may be received in a downlink control information (DCI) message and may indicate one or both of the identity of the NZP CSI-RS resource set or the identity of the NZP CSI-RS resource.

[0104] In some embodiments, the terminal device 120 may further transmit capability information to the network device, where the capability information may indicate that the terminal device supports CJT TRS transmission and CJT physical downlink shared channel (PDSCH) transmission.

[0105] In some embodiments, terminal device 120 may further receive a TCI state configuration indicating multiple possible TCI states for the terminal device, and each TCI state in the TCI state configuration may be associated with one TRS resource in the TRS resource configuration.

[0106] In some embodiments, terminal device 120 may further receive CSI-RS from the network device, perform measurements on the CSI-RS, and report results of the measurements to the network device.

[0107] In some embodiments, the terminal device 120 may further receive a transmission mode configuration from the network device, where the transmission mode configuration may indicate a group of transmission modes including one or more of: a CJT mode, a non-coherent joint transmission, an NCJT, mode, or a dynamic point selection mode.

[0108] In some embodiments, the terminal device 120 may further receive a transmission mode indication from the network device, which may trigger the CJT mode.

[0109] In some embodiments, the terminal device 120 may further receive, at the antenna port of the received TRS, a demodulation reference signal (DMRS) and a scheduled CJT PDSCH associated with the DMRS.

[0110] In some embodiments, the received TRS may include the most recent TRS received up to a predetermined number of time slots before the scheduled CJT PDSCH transmission.

[0111] In some embodiments, the received TRS may include a TRS that is last triggered by a TRS triggering indication and that is received up to a predetermined number of time slots before the transmission of the scheduled CJT PDSCH, and / or the TRS triggering indication may be separate from the schedule command for scheduling the CJT PDSCH.

[0112] In some embodiments, terminal device 120 may further receive a schedule command for PDSCH transmission and receive DMRS and PDSCH based on the QCL performance prediction.

[0113] Advantageously, by receiving a QCL source configuration that indicates at least two TCI states that indicate reference signals from valid sources for the CJT of the TRS, the terminal device 120 can make QCL characteristic predictions based on the QCL source configuration, and thus, transmission efficiency can be significantly improved.

[0114] 6 illustrates a flowchart of an example method 600 implemented in a network device (e.g., a network device 110 that may be associated with multiple TRPs for a CJT) in accordance with some embodiments of the present disclosure. For purposes of discussion, the method 600 will be described from the perspective of the network device 110 with reference to FIG. 1.

[0115] At 620, the network device 130 receives results of measurements on a set of channel state information reference signals (CSI-RS) from the terminal device.

[0116] At 640, the network device 110 transmits a quasi-co-location (QCL) source configuration to the terminal device. The QCL source configuration may indicate at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on results of measurements on the set of CSI-RS.

[0117] In some embodiments, the QCL source configuration may be indicated by a bitmap, where one bit in the bitmap may be associated with one of multiple possible TCI states.

[0118] In some embodiments, the network device 110 may further transmit a TRS resource configuration to the terminal device for QCL characteristic prediction of the CJT.

[0119] In some embodiments, the QCL characteristic prediction may include predictions for one or more of: Doppler shift, Doppler spread, mean delay, delay spread, or spatial reception parameters.

[0120] In some embodiments, the TRS resource configuration may be transmitted in a radio resource control (RRC) message and may indicate one or more TRS resource sets, where each TRS resource set may include four periodic non-zero power channel state information reference signal (NZP CSI-RS) resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

[0121] In some embodiments, the TRS resource configuration may be transmitted within a downlink control information (DCI) message and may indicate one or both of the identity of the NZP CSI-RS resource set or the identity of the NZP CSI-RS resource.

[0122] In some embodiments, the network device 110 may further receive capability information from the terminal device, where the capability information may indicate that the terminal device supports CJT TRS transmissions and CJT physical downlink shared channel (PDSCH) transmissions.

[0123] In some embodiments, the network device 110 may further transmit a TCI state configuration indicating multiple possible TCI states for the terminal device, and each TCI state in the TCI state configuration may be associated with one TRS resource in the TRS resource configuration.

[0124] In some embodiments, the network device 110 may further transmit the CSI-RS to the terminal device.

[0125] In some embodiments, the network device 110 may further determine one or more CJT parameters based on results of the received measurements, and the one or more CJT parameters may include one or more of: a precoder for the CJT, a rank, or a modulation and coding scheme (MCS) for the CJT.

[0126] In some embodiments, the network device 110 may further transmit a transmission mode configuration to the terminal device, where the transmission mode configuration may indicate a group of transmission modes including one or more of: a CJT mode, a non-coherent joint transmission (NCJT) mode, or a dynamic point selection mode.

[0127] In some embodiments, the network device 110 may transmit a transmission mode indication to the terminal device, and the transmission mode indication may trigger the CJT mode.

[0128] In some embodiments, the network device 110 may further transmit, on the antenna port of the transmitted TRS, a demodulation reference signal (DMRS) and a scheduled CJT PDSCH associated with the DMRS.

[0129] In some embodiments, the transmitted TRS may include the most recent TRS transmitted up to a predetermined number of time slots before the scheduled CJT PDSCH transmission.

[0130] In some embodiments, the transmitted TRS may include a TRS that is last triggered by a TRS triggering indication and transmitted up to a predetermined number of time slots before the transmission of the scheduled CJT PDSCH, and the schedule command may be separated from the DCI that triggers the TRS.

[0131] In some embodiments, the network device 110 may further transmit a schedule command for the PDSCH transmission and transmit the DMRS and PDSCH based on the QCL performance prediction.

[0132] In some embodiments, the network device 110 may further activate an available QCL source either by a medium access control (MAC) control element (CE) or a DCI message.

[0133] Advantageously, with a QCL source configuration exhibiting at least two TCI states that indicate a reference signal from a valid source for CJT of the TRS, the terminal device 120 performs QCL characteristic prediction based on the QCL source configuration, and thus transmission efficiency can be significantly improved.

[0134] In some embodiments, an apparatus capable of performing any of the operations of method 500 (e.g., terminal device 120) may include means for performing each step of method 500. The means may be implemented in any suitable form. For example, the means may be implemented in a circuit or a software module.

[0135] In some embodiments, an apparatus includes means for receiving a quasi-colocated (QCL) source configuration from a network device. The QCL source configuration indicates at least two transmit configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS). The apparatus further includes means for performing a QCL performance prediction for the received TRS based on the QCL source configuration.

[0136] In some embodiments, the QCL source configuration may be indicated by a bitmap, with one bit in the bitmap being associated with one of multiple possible TCI states.

[0137] In some embodiments, the QCL characteristic prediction may include predictions for one or more of: Doppler shift, Doppler spread, mean delay, delay spread, or spatial reception parameters.

[0138] In some embodiments, the apparatus may include means for receiving a TRS resource configuration for QCL performance prediction of the CJT.

[0139] In some embodiments, the TRS resource configuration may be received in a radio resource control (RRC) message and may indicate one or more TRS resource sets, where each TRS resource set may include four periodic non-zero power channel state information reference signal (NZP CSI-RS) resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

[0140] In some embodiments, the TRS resource configuration may be received in a downlink control information (DCI) message and indicates one or both of the identity of the NZP CSI-RS resource set or the identity of the NZP CSI-RS resource.

[0141] In some embodiments, the apparatus may further include means for transmitting capability information to the network device, where the capability information may indicate that the terminal device supports CJT TRS transmission and CJT Physical Downlink Shared Channel (PDSCH) transmission.

[0142] In some embodiments, the apparatus may further include means for receiving a TCI state configuration indicating a plurality of possible TCI states for the terminal device, wherein each TCI state in the TCI state configuration may be associated with one TRS resource in the TRS resource configuration.

[0143] In some embodiments, the apparatus may further include means for receiving a CSI-RS from a network device, means for performing measurements on the CSI-RS, and means for reporting results of the measurements to the network device.

[0144] In some embodiments, the apparatus may further include means for receiving a transmission mode configuration from the network device, wherein the transmission mode configuration may indicate a group of transmission modes including one or more of: a CJT mode, a non-coherent joint transmission (NCJT) mode, or a dynamic point selection mode.

[0145] In some embodiments, the apparatus may further include means for receiving a transmission mode indication from the network device, the transmission mode indication may trigger the CJT mode.

[0146] In some embodiments, the apparatus may further include means for receiving, at an antenna port of the received TRS, a demodulation reference signal (DMRS) and a scheduled CJT PDSCH associated with the DMRS.

[0147] In some embodiments, the received TRS may include the most recent TRS received up to a predetermined number of time slots before the scheduled CJT PDSCH transmission.

[0148] In some embodiments, the received TRS may include a TRS that is last triggered by a TRS triggering indication and that is received up to a predetermined number of time slots before the transmission of the scheduled CJT PDSCH, and / or the TRS triggering indication may be separate from the schedule command for scheduling the CJT PDSCH.

[0149] In some embodiments, the apparatus may further include means for receiving a schedule command for a PDSCH transmission and for receiving the DMRS and the PDSCH based on the QCL characteristic prediction.

[0150] Advantageously, by receiving a QCL source configuration that indicates at least two TCI states that indicate reference signals from valid sources for the CJT of the TRS, the terminal device 120 can make QCL characteristic predictions based on the QCL source configuration, and thus, transmission efficiency can be significantly improved.

[0151] In some embodiments, an apparatus capable of performing any of method 600 (e.g., network device 110 associated with multiple TRPs for CJT) may include means for performing each step of method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuit or a software module.

[0152] In some embodiments, the apparatus may include means for receiving results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device. The apparatus may further include means for transmitting a quasi-co-location (QCL) source configuration to the terminal device. The QCL source configuration may indicate at least two transmission configuration indication (TCI) states that indicate reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0153] In some embodiments, the QCL source configuration may be indicated by a bitmap, with one bit in the bitmap being associated with one of multiple possible TCI states.

[0154] In some embodiments, the apparatus may further include means for transmitting a TRS resource configuration to a terminal device for QCL characteristic prediction of the CJT.

[0155] In some embodiments, the QCL characteristic prediction may include predictions for one or more of: Doppler shift, Doppler spread, mean delay, delay spread, or spatial reception parameters.

[0156] In some embodiments, the TRS resource configuration may be transmitted in a radio resource control (RRC) message and may indicate one or more TRS resource sets, where each TRS resource set may include four periodic non-zero power channel state information reference signal (NZP CSI-RS) resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

[0157] In some embodiments, the TRS resource configuration may be transmitted within a downlink control information (DCI) message and may indicate one or both of the identity of the NZP CSI-RS resource set or the identity of the NZP CSI-RS resource.

[0158] In some embodiments, the apparatus may further include means for receiving capability information from the terminal device, where the capability information may indicate that the terminal device supports CJT TRS transmission and CJT physical downlink shared channel, PDSCH, transmission.

[0159] In some embodiments, the apparatus may further include means for transmitting a TCI state configuration indicating a plurality of possible TCI states for the terminal device, wherein each TCI state in the TCI state configuration may be associated with one TRS resource in the TRS resource configuration.

[0160] In some embodiments, the apparatus may further include means for transmitting the CSI-RS to the terminal device.

[0161] In some embodiments, the apparatus may further include means for determining one or more CJT parameters based on results of the received measurements, and the one or more CJT parameters may include one or more of: a precoder for the CJT, a rank, or a modulation and coding scheme for the CJT, MCS.

[0162] In some embodiments, the apparatus may further include means for transmitting a transmission mode configuration to the terminal device, wherein the transmission mode configuration may indicate a group of transmission modes including one or more of: a CJT mode, a non-coherent joint transmission (NCJT) mode, or a dynamic point selection mode.

[0163] In some embodiments, the apparatus may further include means for transmitting a transmission mode indication to a terminal device, the transmission mode indication may trigger the CJT mode.

[0164] In some embodiments, the apparatus may further include means for transmitting, at the antenna port of the transmitted TRS, a demodulation reference signal (DMRS) and a scheduled CJT PDSCH associated with the DMRS.

[0165] In some embodiments, the transmitted TRS may include the most recent TRS transmitted up to a predetermined number of time slots before the scheduled CJT PDSCH transmission.

[0166] In some embodiments, the transmitted TRS may include a TRS that is last triggered by a TRS triggering indication and transmitted up to a predetermined number of time slots before the transmission of the scheduled CJT PDSCH, and the schedule command may be separated from the DCI that triggers the TRS.

[0167] In some embodiments, the apparatus may further include means for transmitting a schedule command for the PDSCH transmission and for transmitting the DMRS and the PDSCH based on the QCL performance prediction.

[0168] In some embodiments, the apparatus may further include means for activating the valid QCL source by either a Medium Access Control (MAC) Control Element (CE) or a DCI message.

[0169] It should be understood that, for the purpose of brevity, the operations in the network device have been briefly described hereinabove. These operations on the network side may correspond to those on the terminal device side. Therefore, for detailed operations regarding some of the operations or features in FIG. 6, reference may be made to the contents described above for the terminal device with reference to FIG. 2 and FIG. 5.

[0170] Advantageously, with a QCL source configuration exhibiting at least two TCI states that indicate a reference signal from a valid source for CJT of the TRS, the terminal device 120 can perform QCL characteristic prediction based on the QCL source configuration, and thus transmission efficiency can be significantly improved.

[0171] In some embodiments, an apparatus capable of performing method 500 (e.g., terminal device 120) may comprise means for performing each step of method 500. The means may be implemented in any suitable form. For example, the means may be implemented as a circuit or a software module.

[0172] In some embodiments, the apparatus may further comprise means for performing steps in some embodiments of method 500. In some embodiments, the means may comprise at least one processor; and at least one memory containing computer program code, the at least one memory and the computer program code configured to cause execution of the apparatus by the at least one processor.

[0173] In some embodiments, an apparatus for performing method 500 comprises: means for receiving a quasi-co-location (QCL) source configuration from a network device. The QCL source configuration indicates at least two transmit configuration indication (TCI) states that indicate a reference signal from a valid QCL source for coherent joint transmission (CJT) of a tracking reference signal (TRS). The apparatus may further include means for performing a QCL performance prediction for the received TRS based on the QCL source configuration.

[0174] In some embodiments, an apparatus capable of performing method 600 (e.g., network device 110) may comprise means for performing each step of method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuit or a software module.

[0175] In some embodiments, the apparatus may further comprise means for performing steps in some embodiments of method 600. In some embodiments, the means may comprise at least one processor; and at least one memory containing computer program code, the at least one memory and the computer program code configured to cause execution of the apparatus by the at least one processor.

[0176] In some embodiments, an apparatus for performing method 600 comprises: means for receiving results of measurements on a set of channel state information reference signals (CSI-RS) from a terminal device. The apparatus may further include means for transmitting a quasi-co-location (QCL) source configuration to the terminal device. The QCL source configuration may indicate at least two transmission configuration indication (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on the results of the measurements on the set of CSI-RS.

[0177] 7 is a simplified block diagram of a device 700 suitable for implementing an embodiment of the present disclosure. The device 700 may be provided to implement a communication device, for example, the terminal device 120 as shown in FIG. 1. As shown, the device 700 includes one or more processors 710, one or more memories 740 coupled to the processors 710, and one or more transmitters and / or receivers (TX / RX) 740 that may be coupled to the processors 710.

[0178] The TX / RX 740 is for bidirectional communication. The TX / RX 740 may have at least one antenna to facilitate communication. The communication interface may represent any interface necessary for communication with other network elements. The communication interface may be a hardware or software-based interface. For example, the communication interface may be one or more transceivers. The one or more transceivers may be coupled to one or more antennas or antenna ports for wirelessly transmitting and / or receiving communication signals. The antennas or antenna ports may be of the same or different types. The antennas or antenna ports may be located at different locations on the device. The one or more transceivers may enable the device to communicate with other devices, which may be wired and / or wireless. The transceivers may support one or more wireless technologies. For example, the one or more transceivers may include a cellular subsystem, a WLAN subsystem, and / or a Bluetooth™ subsystem. The one or more transceivers may include a processor, controller, radio, socket, plug, buffer, or similar circuitry to form one or more communication channels to one or more radio frequency units.

[0179] The processor 710 may be of any type suitable for a local technology network, and may include, by way of non-limiting example, one or more of: a general-purpose computer, a special-purpose computer, a microprocessor, a digital signal processor (DSP), and a processor based on a multi-core processor architecture. The device 700 may have multiple processors, such as application-specific integrated circuit chips that are time-slaved to a clock that synchronizes the main processor.

[0180] The memory 720 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, read-only memory (ROM) 724, electrically programmable read-only memory (EPROM), flash memory, hard disks, compact disks (CDs), digital video disks (DVDs), and other magnetic and / or optical storage. Examples of volatile memory include, but are not limited to, random access memory (RAM) 722 and other volatile memory that does not persist through power-off periods.

[0181] The computer program 730 may include computer-executable instructions that are executed by the associated processor 710. The program 730 may be stored in ROM 724. The processor 710 may perform any suitable actions and processes by loading the program 730 into RAM 722.

[0182] The embodiments of the present disclosure may be implemented using a program such that the device 700 may perform any of the processes of the present disclosure, such as those discussed with reference to Figures 1 to 6. The embodiments of the present disclosure may also be implemented by hardware or a combination of software and hardware.

[0183] In some embodiments, the program 730 may be tangibly contained in a computer-readable medium, which may be included in the device 700 (such as memory 720) or other storage device accessible by the device 700. The device 700 may load the program 730 from the computer-readable medium into RAM 722 for execution. The computer-readable medium may include any type of tangible non-volatile storage, such as ROM, EPROM, flash memory, hard disk, CD, DVD, and the like. Figure 8 shows an example of a computer-readable medium 800 in the form of a CD or DVD. The computer-readable medium has the program 730 stored thereon.

[0184] In general, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic, or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software that may be executed by a controller, microprocessor, or other computing device. While various aspects of the embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other graphical representations, it should be understood that the blocks, apparatus, systems, techniques, or methods described herein may be implemented in, by way of non-limiting example, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing device, or some combination thereof.

[0185] The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, that execute within a device on a desired real or virtual processor to perform process signaling 200, method 500, or 600, as described above with reference to FIGS. 1 through 6. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or divided among program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within local or distributed devices. In distributed devices, program modules may be located in both local and remote storage media.

[0186] Program code for carrying out the methods of the present disclosure may be written in any combination of one or more programming languages. These program codes may be provided to a processor or controller of a general-purpose computer, a special-purpose computer, or other programmable data processing apparatus such that, when executed by the processor or controller, the program code causes the functions / acts specified in the flowcharts and / or block diagrams to be performed. The program code may execute entirely on the machine, partially on the machine, as a stand-alone software package, partially on the machine and partially on a remote machine, or entirely on a remote machine or server.

[0187] In the context of the present disclosure, computer program code or associated data may be carried by any suitable carrier to enable a device, apparatus, or processor to perform the various processes and operations as described above. Examples of carriers include signals, computer-readable media, and the like.

[0188] The computer-readable medium may be a computer-readable signal medium or a computer-readable storage medium. The computer-readable medium may include, but is not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of computer-readable storage media include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or flash memory), an optical fiber, a portable compact disk read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. The term "non-transitory" as used herein refers to the medium itself (i.e., tangible, not a signal), as opposed to a limitation on data storage permanence (e.g., RAM or ROM).

[0189] Furthermore, although operations are depicted in a particular order, this should not be understood as requiring such operations to be performed in the particular order or sequential order shown, or that all illustrated operations be performed to achieve desirable results. In certain situations, multitasking and parallel processing may be advantageous. Similarly, while some specific implementation details are included in the above description, these should not be construed as limitations on the scope of the disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable subcombination.

[0190] Although the present disclosure has been described in language specific to structural features and / or methodological acts, it is to be understood that the present disclosure as defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A terminal device, one or more transceivers; one or more processors communicatively coupled to the one or more transceivers; and one or more processors in a terminal device, receiving a quasi-colocation (QCL) source configuration from the network device, the QCL source configuration indicating at least two transmission configuration indications (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS); Based on the QCL source configuration, a QCL characteristic prediction is made for the received TRS. A terminal device configured to:

2. 2. The terminal device of claim 1, wherein the QCL source configuration is indicated by a bitmap, with one bit in the bitmap being associated with one of a plurality of possible TCI states.

3. 3. The terminal device according to claim 1 or 2, wherein the QCL characteristic prediction comprises a prediction for one or more of the following: Doppler shift, Doppler spread, mean delay, delay spread, or spatial reception parameters.

4. The terminal device according to claim 1 , wherein the terminal device is further configured to receive a TRS resource configuration for QCL characteristic prediction of the CJT.

5. 5. The terminal device of claim 4, wherein the TRS resource configuration is received in a radio resource control, RRC, message and indicates one or more TRS resource sets, each TRS resource set including four periodic non-zero power channel state information reference signal, NZP CSI-RS, resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

6. 5. The terminal device of claim 4, wherein the TRS resource configuration is received in a downlink control information, DCI, message, and indicates one or both of an identity of an NZP CSI-RS resource set or an identity of an NZP CSI-RS resource.

7. A terminal device according to any one of claims 1 to 6, wherein the terminal device is further configured to transmit capability information to the network device, the capability information indicating that the terminal device supports CJT TRS transmission and CJT physical downlink shared channel, PDSCH, transmission.

8. The terminal device is further configured to receive a TCI state configuration indicating a plurality of possible TCI states for the terminal device; 8. The terminal device according to claim 1, wherein each TCI state in the TCI state configuration is associated with one TRS resource in the TRS resource configuration.

9. The terminal device is receiving a CSI-RS from a network device; performing measurements on the CSI-RS; and Reports the results of measurements to network devices The terminal device according to claim 1 , further comprising:

10. 10. The terminal device of claim 1, wherein the terminal device is further configured to receive a transmission mode configuration from the network device, the transmission mode configuration indicating a group of transmission modes including one or more of a CJT mode, a non-coherent joint transmission, an NCJT, mode, or a dynamic point selection mode.

11. The terminal device of claim 10, wherein the terminal device is further configured to receive a transmission mode indication from the network device, the transmission mode indication triggering the CJT mode.

12. 12. The terminal device according to claim 1, wherein the terminal device is further configured to receive a scheduled CJT PDSCH associated with a demodulation reference signal, a DMRS, and a DRMS ​​at the antenna port of the received TRS.

13. 13. The terminal device of claim 12, wherein the received TRS includes the most recent TRS received up to a predetermined number of time slots before a scheduled CJT PDSCH transmission.

14. The received TRS includes the TRS last triggered by the TRS triggering indication and received at most a predetermined number of time slots before the scheduled CJT PDSCH transmission; and / or The terminal device of claim 12 , wherein the TRS trigger indication is separated from a schedule command for scheduling the CJT PDSCH.

15. The terminal device is receiving a schedule command for PDSCH transmission; and Receiving DMRS and PDSCH based on QCL characteristic prediction 15. The terminal device according to claim 1, further comprising:

16. 1. A network device, comprising: one or more transceivers; one or more processors communicatively coupled to the one or more transceivers; and one or more processors configured to configure the network device to: receiving, from a terminal device, results of measurements on a set of channel state information reference signals, CSI-RS; causing the terminal device to transmit a quasi-co-location (QCL) source configuration, the QCL source configuration indicating at least two transmission configuration indications (TCI) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on results of measurements on a set of CSI-RSs; Network devices.

17. 17. The network device of claim 16, wherein the QCL source configuration is indicated by a bitmap, with one bit in the bitmap being associated with one of a plurality of possible TCI states.

18. The network device according to claim 16 or 17, further configured to send a TRS resource configuration to a terminal device for QCL characteristic prediction of the CJT.

19. 20. The network device of claim 18, wherein the QCL characteristic prediction includes a prediction for one or more of a Doppler shift, a Doppler spread, a mean delay, a delay spread, or a spatial reception parameter.

20. 20. The network device of claim 19, wherein the TRS resource configuration is transmitted in a radio resource control, RRC, message and indicates one or more TRS resource sets, each TRS resource set including four periodic non-zero power channel state information reference signal, NZP CSI-RS, resources in two consecutive time slots, with two periodic NZP CSI-RS resources in each time slot.

21. 20. The network device of claim 19, wherein the TRS resource configuration is transmitted in a downlink control information, DCI, message and indicates one or both of an identity of an NZP CSI-RS resource set or an identity of an NZP CSI-RS resource.

22. 22. The network device of claim 16, further configured to receive capability information from the terminal device, the capability information indicating that the terminal device supports CJT TRS transmission and CJT physical downlink shared channel, PDSCH, transmission.

23. The network device is further configured to transmit a TCI state configuration indicating a plurality of possible TCI states for the terminal device; 23. The network device of claim 16, wherein each TCI state in the TCI state configuration is associated with one TRS resource in the TRS resource configuration.

24. The network device according to any one of claims 16 to 23, wherein the network device is further configured to transmit a CSI-RS to a terminal device.

25. The network device and further determining one or more CJT parameters based on results of the received measurements; 25. The network device of claim 24, wherein the one or more CJT parameters include one or more of a precoder for the CJT, a rank, or a modulation and coding scheme for the CJT, an MCS.

26. 26. The network device of claim 16, wherein the network device is further configured to send a transmission mode configuration to the terminal device, the transmission mode configuration indicating a group of transmission modes including one or more of a CJT mode, a non-coherent joint transmission, an NCJT, mode, or a dynamic point selection mode.

27. 27. The network device of claim 26, wherein the network device is further configured to send a transmission mode indication to the terminal device, the transmission mode indication triggering the CJT mode.

28. 28. The network device of claim 16, wherein the network device is further configured to transmit a demodulation reference signal, a DMRS, and a scheduled CJT PDSCH associated with the DMRS on the antenna port of the transmitted TRS.

29. 30. The network device of claim 28, wherein the transmitted TRS includes a most recent TRS transmitted up to a predetermined number of time slots before a scheduled CJT PDSCH transmission.

30. The transmitted TRS includes the TRS last triggered by the TRS triggering indication and transmitted at most a predetermined number of time slots before the scheduled CJT PDSCH transmission; 30. The network device of claim 28, wherein the schedule command is separate from the DCI that triggers the TRS.

31. The network device Transmitting a schedule command for PDSCH transmission; and Transmitting DMRS and PDSCH based on predicted QCL characteristics 31. The network device of any one of claims 16 to 30, further configured to:

32. 32. The network device of claim 16, wherein the network device is further configured to activate a valid QCL source by any of a Medium Access Control, MAC, Control Element, CE, or DCI message.

33. 1. A method in a terminal device, comprising: receiving a quasi-colocation (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmission configuration indications (TCI) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS); Predicting QCL characteristics for received TRS based on QCL source configuration A method comprising:

34. 1. A method in a network device, comprising: receiving, from a terminal device, results of measurements on a set of channel state information reference signals, CSI-RS; transmitting a quasi-colocation (QCL) source configuration to a terminal device, the QCL source configuration indicating at least two transmission configuration indications (TCI) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on results of measurements on a set of CSI-RS; A method comprising:

35. An apparatus for a terminal device, comprising: means for receiving a quasi-colocation (QCL) source configuration from a network device, the QCL source configuration indicating at least two transmission configuration indications (TCI) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS); means for performing a QCL characteristic prediction for the received TRS based on the QCL source configuration; An apparatus comprising:

36. A network device apparatus, means for receiving results of measurements on a set of channel state information reference signals, CSI-RS, from a terminal device; and An apparatus comprising: means for transmitting a quasi-colocation (QCL) source configuration to a terminal device, the QCL source configuration indicating at least two transmission configuration indications (TCI) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on results of measurements on a set of CSI-RS.

37. A terminal device, at least one processor; at least one memory containing computer program code; and at least one memory and computer program code configured to cause the terminal device to: receiving a quasi-colocation (QCL) source configuration from the network device, the QCL source configuration indicating at least two transmission configuration indications (TCI) states indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS); Based on the QCL source configuration, a QCL characteristic prediction is made for the received TRS. A terminal device configured to:

38. 1. A network device, comprising: at least one processor; at least one memory containing computer program code; and at least one memory and computer program code configured to cause the terminal device to: receiving, from a terminal device, results of measurements on a set of channel state information reference signals, CSI-RS; and causing the terminal device to transmit a quasi-colocation (QCL) source configuration, the QCL source configuration indicating at least two transmission configuration indications (TCIs) indicating reference signals from valid QCL sources for coherent joint transmission (CJT) of tracking reference signals (TRS) based on results of measurements on a set of CSI-RSs. A network device that is configured to:

39. A non-transitory computer readable medium containing program instructions for causing an apparatus to perform at least the method of claim 34 or 35.

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