Transmission timing of an uplink transmission

Abstract

A method includes obtaining by a user device one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

Description

TRANSMISSION TIMING OF AN UPLINK TRANSMISSION TECHNICAL FIELD

[0001] This description relates to wireless communications.BACKGROUND

[0002] A communication system may be a facility that enables communication between two or more nodes or devices, such as fixed or mobile communication devices. Signals can be carried on wired or wireless carriers.

[0003] An example of a cellular communication system is an architecture that is being standardized by the 3rd Generation Partnership Project (3GPP). A recent development in this field is often referred to as the long-term evolution (LTE) of the Universal Mobile Telecommunications System (UMTS) radio-access technology. EUTRA (evolved UMTS Terrestrial Radio Access) is the air interface of 3GPP’s Long Term Evolution (LTE) upgrade path for mobile networks. In LTE, base stations or access points (APs), which are referred to as enhanced Node AP (eNBs), provide wireless access within a coverage area or cell. In LTE, mobile devices, or mobile stations are referred to as user equipments (UE). LTE has included a number of improvements or developments. Aspects of LTE are also continuing to improve.

[0004] 5G New Radio (NR) development is part of a continued mobile broadband evolution process to meet the requirements of 5G, similar to earlier evolution of 3G and 4G wireless networks. In addition, 5G is also targeted at the new emerging use cases in addition to mobile broadband. A goal of 5G is to provide significant improvement in wireless performance, which may include new levels of data rate, latency, reliability, and security. 5G NR may also scale to efficiently connect the massive Internet of Things (loT) and may offer new types of mission-critical services. For example, ultra-reliable and low-latency communications (URLLC) devices may require high reliability and very low latency. 6G and other networks are also being developed.SUMMARY

[0005] In some aspects, the techniques described herein relate to an apparatus including: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the information, atleast one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0006] In some aspects, the techniques described herein relate to an apparatus including: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0007] In some aspects, the techniques described herein relate to an apparatus including: means for receiving from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; means for selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and means for performing the uplink transmission based on the TT.

[0008] In some aspects, the techniques described herein relate to an apparatus including: means for transmitting to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and means for receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0009] In some aspects, the techniques described herein relate to a method including: receiving, by a user device from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0010] In some aspects, the techniques described herein relate to a method including: transmitting, by a network node to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; andreceiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0011] In some aspects, the techniques described herein relate to an apparatus including: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0012] In some aspects, the techniques described herein relate to an apparatus including: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0013] In some aspects, the techniques described herein relate to an apparatus including: means for obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; means for selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and means for performing the uplink transmission based on the TT.

[0014] In some aspects, the techniques described herein relate to an apparatus including: means for transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and means for receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0015] In some aspects, the techniques described herein relate to a method including: obtaining by a user device one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least onetransmission reception point (TRP) of a second TAG is to be determined; selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0016] In some aspects, the techniques described herein relate to a method including: transmitting, by a network node to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0017] Other example embodiments are provided or described for each of the example methods, including: means for performing any of the example methods; a non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform any of the example methods; and an apparatus including at least one processor, and at least one memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus at least to perform any of the example methods.

[0018] The details of one or more examples of embodiments are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.BRIEF DESCRIPTION OF THE DRAWINGS

[0019] FIG. 1 is a block diagram of a wireless network 130.

[0020] FIG. 2 is a flow chart illustrating operation of an apparatus (e.g., which may be a UE or user device, or other apparatus).

[0021] FIG. 3 is a flow chart illustrating operation of an apparatus (e.g., which may be a network node, a gNB, an eNB, or other apparatus).

[0022] FIG. 4 is a flow diagram illustrating an aspect of an example embodiment.

[0023] FIG. 5 is a flow chart illustrating operation of an apparatus (e.g., which may be a UE or user device, or other apparatus).

[0024] FIG. 6 is a flow chart illustrating operation of an apparatus (e.g., which may be a network node, a gNB, an eNB, or other apparatus).

[0025] FIG. 7 is a flow diagram illustrating an aspect of an example embodiment.

[0026] FIG. 8 illustrates an example deployment of multiple TRPs.

[0027] FIG. 9 is a block diagram of a wireless station or node (e.g., UE, user device, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 1300 according to an example embodiment.DETAILED DESCRIPTION

[0028] It shall be understood that although the terms “first,” “second,”..., etc., in front of noun(s) and the like may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another and they do not limit the order of the noun(s). For example, a first element could be termed a second element, and similarly, a second element could be termed a first element, without departing from the scope of example embodiments. As used herein, the term “and / or” includes any and all combinations of one or more of the listed terms.

[0029] As used herein, unless stated explicitly, performing a step “in response to A” does not indicate that the step is performed immediately after “A” occurs and one or more intervening steps may be included.

[0030] FIG. 1 is a block diagram of a wireless network 130. In the wireless network 130 of FIG. 1, user devices 131, 132, 133 and 135, which may also be referred to as mobile stations (MSs) or user equipment (UEs), may be connected (and in communication) with a base station (BS) 134, which may also be referred to as an access point (AP), an enhanced Node B (eNB), a gNB, or a RAN (radio access network) node.. BS (or AP) 134 provides wireless coverage within a cell 136, including to user devices (or UEs) 131, 132, 133 and 135. BS 134 is also connected to a core network 150 via a N2 or NG interface 151. Although only four user devices (or UEs) are shown as being connected or attached to one BS 134, any number of user devices and / or BS may be provided.

[0031] At least part of the functionalities of a BS (e.g., NG-RAN, gNB, access point (AP), base station (BS) or (e)Node B (eNB), RAN node) may also be carried out by any node, server or host which may be operably coupled to a transceiver, such as a remote radio head. For instance, some functionalities of a BS may be carried out, at least partly, in a central / centralized unit, CU and / or a distributed unit, DU. Thus, 5G networks architecture may be based on a so-called CU-DU split. The gNB-CU (central node) may control a plurality of spatially separated gNB-DUs, acting at least as transmit / receive (Tx / Rx) nodes. In some embodiments, however, the gNB-DUs (also called DU) may comprise e.g., a radio link control (RLC), medium access control (MAC) layer and a physical (PHY) layer, whereas thegNB-CU (also called a CU) may comprise the layers above RLC layer, such as a packet data convergence protocol (PDCP) layer, a radio resource control (RRC) and an internet protocol (IP) layer. Other functional splits are possible too.

[0032] According to an illustrative example, a radio access network (RAN) may be part of a mobile telecommunication system. A RAN may include one or more BSs or RAN nodes that implement a radio access technology, e.g., to allow one or more UEs to have access to a network or core network (CN). Thus, for example, the RAN (RAN nodes, such as BSs or gNBs) may reside between one or more user devices or UEs and a core network. According to an example embodiment, each RAN node (e.g., BS, eNB, gNB, CU / DU, ...) or BS may provide one or more wireless communication services for one or more UEs or user devices, e.g., to allow the UEs to have wireless access to a network, via the RAN node. Each RAN node or BS may perform or provide wireless communication services, e.g., such as allowing UEs or user devices to establish a wireless connection to the RAN node, and sending data to and / or receiving data from one or more of the UEs. For example, after establishing a connection to a UE, a RAN node or network node (e.g., BS, eNB, gNB, CU / DU, ...) may forward data to the UE that is received from a network or the core network, and / or forward data received from the UE to the network or core network. RAN nodes or network nodes (e.g., BS, eNB, gNB, CU / DU, ...) may perform a wide variety of other wireless functions or services, e.g., such as broadcasting control information (e.g., such as system information or on-demand system information) to UEs, paging UEs when there is data to be delivered to the UE, assisting in handover of a UE between cells, scheduling of resources for uplink data transmission from the UE(s) and downlink data transmission to UE(s), sending configuration information to configure one or more UEs, and the like. These are a few examples of one or more functions that a RAN node or BS may perform.

[0033] A user device or user node (user terminal, user equipment (UE), mobile terminal, handheld wireless device, etc.) may refer to a portable computing device that includes wireless mobile communication devices operating either with or without a subscriber identification module (SIM), including, but not limited to, the following types of devices: a mobile station (MS), a mobile phone, a cell phone, a smartphone, a personal digital assistant (PDA), a handset, a device using a wireless modem (alarm or measurement device, etc.), a laptop and / or touch screen computer, a tablet, a phablet, a game console, a notebook, a vehicle, a drone, a sensor, and a multimedia device, as examples, or any other wireless device. It should be appreciated that a user device may also be (or may include) a nearly exclusive uplink only device, of which an example is a camera or video camera loadingimages or video clips to a network. Also, a user node may include a user equipment (UE), a user device, a user terminal, a mobile terminal, a mobile station, a mobile node, a subscriber device, a subscriber node, a subscriber terminal, or other user node. For example, a user node may be used for wireless communications with one or more network nodes (e.g., gNB, eNB, BS, AP, CU, DU, CU / DU) and / or with one or more other user nodes, regardless of the technology or radio access technology (RAT).

[0034] In 5G (which may be referred to as New Radio (NR)) (as an illustrative example), core network 150 may be referred to 5G core network (5GC), which may include an access and mobility management function (AMF). For the example, the AMF may include the following functionalities (e.g., some of the AMF functionalities may be supported in a single instance of an AMF): termination of RAN control plane (CP) interface (N2), termination of non-access stratum (NAS) (or Nl), NAS ciphering and integrity protection, registration management, connection management, reachability management, mobility management, lawful intercept, and / or the like. The 5GC may also include a session management function (SMF) that may include one or more of the following functionalities (one or more of the SMF functionalities may be supported in a single instance of a SMF): session management (e.g. session establishment, modification and release, including tunnel maintenance between a user plane function (UPF) and BS 134), IP address allocation & management (including optional authorization), selection and control of UPF(s), configuration of traffic steering at a UPF to route traffic to proper destination, and / or the like. In UTE (as an illustrative example), core network 150 may be referred to as Evolved Packet Core (EPC), which may include a mobility management entity (MME) which may handle or assist with mobility / handover of user devices between BSs, one or more gateways that may forward data and control signals between the BSs and packet data networks or the Internet, and other control functions or blocks.

[0035] In addition, the techniques described herein may be applied to various types of user devices or data service types, or may apply to user devices that may have multiple applications running thereon that may be of different data service types. New Radio (5G) development may support a number of different applications or a number of different data service types, such as for example: machine type communications (MTC), enhanced machine type communication (eMTC), Internet of Things (loT), and / or narrowband loT user devices, enhanced mobile broadband (eMBB), and ultra-reliable and low-latency communications (URELC). Many of these new 5G (NR) - related applications may require generally higher performance than previous wireless networks.

[0036] loT may refer to an ever-growing group of objects that may have Internet or network connectivity, so that these objects may send information to and receive information from other network devices. For example, many sensor type applications or devices may monitor a physical condition or a status and may send a report to a server or other network device, e.g., when an event occurs. Machine Type Communications (MTC, or Machine to Machine communications) may, for example, be characterized by fully automatic data generation, exchange, processing and actuation among intelligent machines, with or without intervention of humans. Enhanced mobile broadband (eMBB) may support much higher data rates than currently available in LTE.

[0037] Ultra-reliable and low-latency communications (URLLC) is a new data service type, or new usage scenario, which may be supported for New Radio (5G) systems. This enables emerging new applications and services, such as industrial automations, autonomous driving, vehicular safety, e-health services, and so on. 3GPP targets in providing connectivity with reliability corresponding to block error rate (BLER) of 10"5and up to 1 ms U-Plane (user / data plane) latency, by way of illustrative example. Thus, for example, URLLC user devices / UEs may require a significantly lower block error rate than other types of user devices / UEs as well as low latency (with or without requirement for simultaneous high reliability). Thus, for example, a URLLC UE (or URLLC application on a UE) may require much shorter latency, as compared to an eMBB UE (or an eMBB application running on a UE).

[0038] The techniques described herein may be applied to a wide variety of wireless technologies or wireless networks, such as 5G (New Radio (NR)), cmWave, and / or mmWave band networks, loT, MTC, eMTC, eMBB, URLLC, 6G, etc., or any other wireless network or wireless technology. These example networks, technologies or data service types are provided only as illustrative examples.

[0039] Timing advance (TA) technique is used to control uplink (UL) signal transmission timing. A TA determines an offset between a transmission timing of uplink transmission and a downlink (DL) reference timing. A network node, e.g., a gNB may measure the time difference between reception of an uplink channel or signaling, e.g., physical uplink shared channel (PUSCH) / physical uplink control channel (PUCCH) / sounding reference signal (SRS), and the subframe time and may send a timing advance command (TAC) indicating TA to the UE to adjust the uplink transmission to make it better aligned with the subframe timing at the network side. A timing advance group (TAG) may include one or more serving cells or transmission reception points (TRPs) with the same uplink TA and same downlinktiming reference cell that provides downlink reference timing for the UE to determine the uplink transmission timing.

[0040] A TRP may support reception of uplink channel and / or signal, such as for example, at least one of: a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), or an uplink reference signal such as for example, sounding reference signal (SRS). The TRP may also support transmission of downlink channel and / or signal, such as for example, at least one of a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), synchronization signal block (SSB), or a downlink reference signal such as for example, channel state information reference signal (CSI-RS). If a TRP does not support transmission of any downlink channel or signaling that can provide a downlink reference timing to UE, the TRP may be referred to as an uplink-only TRP. In example embodiments, an uplink-only TRP may not transmit PDCCH or PDSCH that provides downlink reference timing for UE, but under certain conditions may transmit signal like SSB. For a TAG with only UL-only TRPs, the UE will not be required to monitor any DL reference timing from this TAG. Instead, the UE may need to monitor and use DL reference timing associated with another TAG. A problem may arise when there are multiple TAGs associated with respective DL reference timings and therefore the UE may need to decide which DL reference timing to use for determining a transmission timing (TT) for the uplink transmission to the uplink-only TRP(s).

[0041] Example embodiments enable enhancement of the communication system performance by providing information of TAGs or TRPs to the UE. Based on the provided information a transmission timing (TT) for an uplink transmission to at least one TRP (or at least one uplink-only TRP) of a second TAG may be determined.

[0042] In an example, a UE may receive from a network node, information indicative of a first timing advance group (TAG). For example, the UE may receive from the network node a radio resource control (RRC) message that may include the information indicative of the first TAG. As another example, the network node may transmit a medium access control (MAC) control element (MAC-CE) to the UE that may include the information indicative of the first TAG. Based on the information indicative of the first TAG, the UE may determine a transmission timing (TT) for an uplink transmission to at least one TRP of a second TAG. The UE may select based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG. The UE may perform the uplink transmission based on the TT.

[0043] For example, the network node may provide to the UE by transmitting a message that includes information of association between the first TAG and the second TAG. For example, for an uplink transmission to a TRP of the second TAG, the UE may use downlink (DL) reference signal from the first TAG (e.g., at least one TRP of the first TAG). For example, the message may include an information element that may carry (indicate) the information. The message may be a RRC message, a MAC-CE, non-access stratum (NAS), and / or the like. The information of association may be used by the UE to determine the TT for the uplink transmission. The TT may be calculated based on a timing advance (TA) indicated by at least one TRP of the first TAG. The UE may receive TA from multiple TRPs and therefore, it is beneficial to determine the best candidate for calculation of the TT for the uplink transmission. Therefore, when example embodiments are implemented, the UE may be able to use the received information from the network to make a proper determination of which TAG to use for calculation of TT for uplink transmission to at least one TRP of the second TAG.

[0044] Therefore, example embodiments enable enhancement of the communication system performance when utilizing the provided information indicative of the first TAG. By utilizing the provide information, the UE may determine an appropriate TT for the uplink transmission.

[0045] FIG. 2 is a flow chart illustrating operation of an apparatus (e.g., which may be a UE or user device, or other apparatus). Operation 210 includes receiving, by a user device (e.g., a UE) from a network node (e.g., a gNB, a gNB-DU, a cell of a base station, an eNB, and / or the like), information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one TRP of a second TAG is to be determined. For example, the UE may receive from the network node a radio resource control (RRC) message that may include the information indicative of the first TAG. As another example, the network node may transmit a medium access control (MAC) control element (MAC-CE) to the UE that may include the information indicative of the first TAG. Operation 220 includes selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG. Operation 230 includes performing the uplink transmission based on the TT. For example, the uplink transmission may be performed to the at least one TRP of the second TAG.

[0046] FIG. 3 is a flow chart illustrating operation of an apparatus (e.g., which may be a network node, a gNB, an eNB, or other apparatus). Operation 310 includes transmitting, by anetwork node to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one TRP of a second TAG is to be determined. Operation 320 includes receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0047] With respect to the method described in FIG. 2, and FIG. 3, the information may further be indicative of the second TAG that may include the at least one TRP. As an example, the information may be indicative of association between the first TAG and the second TAG. For example, the association may include a mapping between the first TAG, and the second TAG. For example, the association may indicate to the UE to use the at least one downlink reference signal (of at least one TRP) of the first TAG to determine a TT for uplink transmission to at least one TRP of the second TAG. As another example, the association may include association between an identifier of the first TAG and an identifier of the second TAG.With respect to the method described in FIG. 2, and FIG. 3, the UE may determine the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG. For example, the TA may be determined based on a TAC received from a non-UL-only TRP, for example, from the at least one TRP of the first TAG.

[0048] With respect to the method described in FIG. 2, and FIG. 3, the uplink transmission may include at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0049] With respect to the method described in FIG. 2, and FIG. 3, the information may be received by the UE from the network node, as part of: a radio resource control (RRC) message, a medium access control (MAC) control element (MAC-CE), and / or the like.With respect to the method described in FIG. 2, and FIG. 3, the at least one TRP of the second TAG may support reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH), but does not support transmission of a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), downlink reference signals, and / or the like.

[0050] With respect to the method described in FIG. 2, and FIG. 3, the first TAG may include one or more TRPs.

[0051] FIG. 4 is a flow diagram illustrating an aspect of an example embodiment. At step 1, the network node may configure the UE with multi-TRP configurations, and / or time division multiplexing (TDM) configuration for one or more TAGs, e.g., TAG1 to TAG3. For example, the UE may receive configuration of the one or more TAGs via RRC messages,system information broadcast, and / or the like. At step 2, the network node may send to the UE information indicative of a first TAG. For example, the information may indicate to the UE to use TAG1 for determining the TT for uplink transmission to at least one TRP of TAG3 (e.g., TRP3 in TAG3). At step 3, the TRP1 of TAG1 may transmit TA information, e.g., TAI. At step 4, TRP2 of TAG2 may transmit information of TA2 and TA3. In this example, TA2 and TA3 are for TAG2 and TAG3, respectively. At step 5, the TRP1 of TAG1 may transmit downlink (DL) reference signals to the UE. At step 6, the UE may estimate DL reference timing (RT) for TAG1. At step 7, the TRP2 of TAG2 may transmit to the UE DL reference signals. At step 8, the UE may estimate DL reference timing (RT) for TAG2. At step 9, the UE may compute uplink TT for TAG1 based on the DL reference timing for TAG1 and TAI. At step 10, the UE may perform an uplink transmission to TRP1 of TAG1. For example, the UE may transmit a PUSCH based on the uplink TT for TAG1. At step 11, the UE may compute uplink TT for TAG2 based on the DL reference timing for TAG2 and TA2. At step 12, the UE may perform an uplink transmission to TRP2 of TAG2. For example, the UE may transmit a PUSCH based on the uplink TT for TAG2. At step 13, the UE may compute uplink TT for TAG3 based on the DL reference timing for TAG1 and TA3. At step 14, the UE may perform an uplink transmission to TRP3 of TAG3 (e.g., an UL-only TRP). For example, the UE may transmit a PUSCH based on the uplink TT for TAG3.

[0052] Additionally or alternatively, example embodiments enable enhancement of the communication system performance by enabling the UE to obtain one or more rules for selecting TAGs or TRPs. The UE may obtain the one or more rules based on preconfigured information or receive the one or more rules from the network, e.g., the network node. Based on the one or more rules, the UE may select a TAG or a TRP based on which the transmission timing (TT) for the uplink transmission to at least one TRP (or at least one uplink-only TRP) of a second TAG may be determined.

[0053] In an example, a UE may obtain one or more rules for selecting a first timing advance group (TAG). The obtaining may include obtaining (e.g., fetching from memory, decoding instructions, receiving from upper layers of a protocol stack, and / or the like) the one or more rules based on configured or preconfigured information. Alternatively, the obtaining may include receiving by the UE from the network, e.g., the network node, a gNB, a base station, a cell of a base station, a TRP of the base station, an eNB, and / or the like. For example, the network node may transmit a medium access control (MAC) control element (MAC-CE) to the UE that may include the one or more rules for selecting the first TAG. For example, the first TAG may be employed by the UE for determining a transmission timing(TT) for an uplink transmission to at least one TRP of a second TAG. The UE may select, based on the one or more rules, at least one downlink reference signal associated with the first TAG. The UE (e.g., based on the one or more rules, at least one downlink reference signal associated with the first TAG, and / or the like) may determine the TT for the uplink transmission to the at least one TRP of the second TAG. The UE may perform the uplink transmission (to the at least one TRP of the second TAG) based on the TT.

[0054] Therefore, when example embodiments are implemented, the UE may be able to use the obtained one or more rules to make a proper determination of which TAG to use for calculation of TT for uplink transmission to at least one TRP of the second TAG.

[0055] FIG. 5 is a flow chart illustrating operation of an apparatus (e.g., which may be a UE or user device, or other apparatus). Operation 510 includes obtaining by a user device one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one TRP of a second TAG is to be determined. The obtaining may include obtaining the one or more rules based on configured or preconfigured information. The obtaining may include fetching from memory, decoding instructions, receiving from upper layers of a protocol stack, and / or the like. Alternatively, the obtaining may include receiving by the UE from the network, e.g., the network node, a gNB, a base station, a cell of a base station, a TRP of the base station, an eNB, a core network node, and / or the like. For example, the network node may transmit a MAC-CE, a RRC message, a non-access stratum (NAS) message to the UE that may include the one or more rules for selecting the first TAG. For example, the selecting may include determining, selecting, or choosing a first TAG and / or at least one TRP associated with the first TAG. The selecting may also include determining an association between the first TAG and the second TAG. Operation 520 includes selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG. Operation 530 includes performing the uplink transmission based on the TT.

[0056] FIG. 6 is a flow chart illustrating operation of an apparatus (e.g., which may be a network node, a gNB, an eNB, or other apparatus). Operation 610 includes transmitting, by a network node to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one TRP of a second TAG is to be determined. Operation 620 includes receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0057] With respect to the method described in FIG. 5, and FIG. 6, the one or more rules may be employed to determine an association between the first TAG and the second TAG.

[0058] With respect to the method described in FIG. 5, and FIG. 6, the one or more rules may indicate at least one of the following: selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to (e.g., before or after) an identifier of the second TAG in the list; selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG may be less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG may be larger than an identifier value of the second TAG; selecting from the list, a first occurrence of the first TAG that may include one or more TRPs that support transmission of a downlink reference signal; selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG; selecting, if the first TAG associated with the second TAG does not include any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and includes at least one TRP that supports transmission of a downlink reference signal; selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; selecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals, and / or the like.

[0059] With respect to the method described in FIG. 5, and FIG. 6, the one or more rules may indicate at least one of: selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG, selecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG, and / or the like.

[0060] With respect to the method described in FIG. 5, and FIG. 6, the TT for the uplink transmission to the at least one TRP of the second TAG may be determined based on at least one of the following: calculating an average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; calculating a weighted average of downlink reference timings of the plurality of downlink reference signalsof the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; calculating a linear combination of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs, and / or the like.

[0061] With respect to the method described in FIG. 5, and FIG. 6, the UE may indicate at least one of the selected first TAG, or a downlink reference timing of the selected first TAG to the network, e.g., the network node.

[0062] With respect to the method described in FIG. 5, and FIG. 6, the UE may determine the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG. The uplink transmission may include at least one of: a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), and / or the like.

[0063] With respect to the method described in FIG. 5, and FIG. 6, wherein: the one or more rules may be preconfigured in the user device. As another example, the one or more rules may be received as part of: a radio resource control (RRC) message, a medium access control (MAC) control element (MAC-CE), and / or the like.With respect to the method described in FIG. 5, and FIG. 6, the at least one of TRP of the second TAG may support reception of at least one of: a physical uplink control channel (PUCCH), a physical uplink shared channel (PUSCH), and / or the like, but does not support transmission of a physical downlink control channel (PDCCH), a physical downlink shared channel (PDSCH), and / or the like.

[0064] FIG. 7 is a flow diagram illustrating an aspect of an example embodiment. At step 1, the network node may configure the UE with multi-TRP configurations, and / or time division multiplexing (TDM) configuration for one or more TAGs, e.g., TAG1 to TAG3. For example, the UE may receive configuration of the one or more TAGs via RRC messages, system information broadcast, and / or the like. At step 2, the UE may obtain one or more rules for selecting a first TAG based on which a transmission timing (TT) for an uplink transmission to at least one TRP of TAG3 (e.g., an UL-only TRP) is to be determined. For example, the obtaining may include obtaining from preconfigured one or more rules or receiving the one or more rules from the network node, e.g., as part of RRC messages and / or MAC-CE. At step 3, the TRP1 of TAG1 may transmit TA information, e.g., TAI. At step 4, TRP2 of TAG2 may transmit information of TA2 and TA3. In this example, TA2 and TA3 are for TAG2 and TAG3, respectively. At step 5, the TRP1 of TAG1 may transmit downlink (DL) reference signals to the UE. At step 6, the UE may estimate DL reference timing (RT) forTAG1. At step 7, the TRP2 of TAG2 may transmit to the UE DL reference signals. At step 8, the UE may estimate DL reference timing (RT) for TAG2. At step 9, the UE may compute uplink TT for TAG1 based on the DL reference timing for TAG1 and TAI. At step 10, the UE may perform an uplink transmission to TRP1 of TAG1. For example, the UE may transmit a PUSCH based on the uplink TT for TAG1. At step 11, the UE may compute uplink TT for TAG2 based on the DL reference timing for TAG2 and TA2. At step 11, the UE may perform an uplink transmission to TRP2 of TAG2. For example, the UE may transmit a PUSCH based on the uplink TT for TAG2. In this example, the one or more rules specify to use the DL RT from the TAG of which a TRP sends the TA for TAG3, i.e., TAG2 in this example as TPR2 sends TA3 for TAG3. At step 13, the UE may compute uplink TT for TAG3 based on the DL reference timing for TAG2 and TA3. At step 14, the UE may perform an uplink transmission to TRP3 of TAG3 (e.g., an UL-only TRP). For example, the UE may transmit a PUSCH based on the uplink TT for TAG3.

[0065] FIG. 8 illustrates an example deployment of multiple TRPs. With respect to example embodiments described in FIGs. 2-7, an example deployment as depicted in FIG. 8 illustrates that a UE may be served in either downlink or uplink by N>2 TRPs where only M>1 out of the N TRPs may support transmission of PDCCH, which can provide DL reference timing in this example, to the UE with the constraint of M<N. As shown in the figure, N=6 and M=3 . There may be some TRPs out of the N TRPs that may be UL-only TRPs that may not support downlink transmissions. As shown in the figure, there are two UL-only TRPs.

[0066] With respect to the deployment depicted in FIG. 8, the network may explicitly inform the UE for example that for an uplink transmission to a TRP of TAG3 the UE may use the DL reference timing monitored for TAG1 (or TAG2). In such scenario, it may be up to network implementation to decide or determine such TAG association. In an example, the network may decide the TAG association based on a geographical location of the TRP (of TAG3, TAG1 or TAG2). For example, the network may compute a mean location for each TAG by averaging the geographical location (e.g., coordinate measures, distance, and / or the like) of each TRP in the corresponding TAG, and then associate to a TAG without any DL transmission a TAG with DL transmissions for which a mean geographical location is the closest to the mean geographical location of the TAG without any DL transmission.

[0067] With respect to the deployment depicted in FIG. 8, the network may use the estimated timing offset for the UE to determine a location information of the UE. The network may use the location information of the UE to determine the best TAG with DL transmissionfor each TAG without DL transmission. As an example, if the UE sends a RACH to each TRP, the network may use triangularization or other positioning methods to determine the location information of the UE.

[0068] As another example with respect to the deployment depicted in FIG. 8, the network may monitor a correlation between timing advance commands (TACs) between each TAG with DL transmission and each TAG without DL transmission. When the TAC for one TAG with DL transmission is well correlated with the TAC for a TAG without DL transmission, then the reference signals for the TAG with DL transmission may be used as reference timing signal for the TAG without DL transmission.

[0069] With respect to the method described in FIG. 5 - FIG. 7, and the deployment depicted in FIG. 8, the UE may obtain the one or more rules for selecting a first TAG based on which the TT for uplink transmission to an UL-only TRP of the second TAG may be determined. In the following, a TAG with DL transmission may be denoted by a type A TAG and a TAG without DL transmission may be denoted by a type B TAG. In an example, the information about the TAG association (e.g., association between the first TAG and the second TAG ) may be encoded in corresponding TAG identifiers (TAG IDs). For example, the one or more rules may state that for a TAG without DL transmission, a TAG with DL transmission whose ID is before (or after) the TAG without DL transmission may be used for setting the DL reference timing for the UL transmission toward the TAG without DL transmission. For example, with respect to the deployment in FIG. 8, assuming that two bits are used for the TAG ID and assuming to use the TAG with DL transmission whose ID is before the TAG without DL transmission, we may have the following examples. Example 1: If TAG1: 00, TAG3: 01, and TAG2: 10, then the UE may use the DL reference timing monitored for TAG1 for the UL transmission toward TAG3. Example 2: If TAG1: 00, TAG2: 01, and TAG3: 10, then the UE may use the DL reference timing monitored for TAG2 for the UL transmission toward TAG3.

[0070] As another example, the list of TAGs may be constructed such that if a given TAG n is a type B TAG, the UE may search the type A TAG with largest index m such that m < n, or with smallest index m such that m > n. As another example, the list of TAGs may be constructed or built such that at least the first entry on the list contains a type A TAG and the UE may use the first TAG as a DL reference timing for any type B TAG.

[0071] In another embodiment, the TAG association may depend on the TRP that sends a TAC to the UE. For example, for a TAG without any DL transmission, the UE may use theDL reference timing of a TAG associated to the TRP that sends the TAC for the TAG without DL transmission.

[0072] With respect to the deployment in FIG. 8, TRP1 may send TAI for TAG1, while TRP5 may send TA2 and TA3 for TAG2 and TAG3, respectively. In this example, the UE may use the DL reference timing of TAG2 for the UL transmission to the UL-only TRP of TAG3.In an example with respect to the deployment illustrated in FIG. 8, the UE may be specified or configured to determine / select which DL reference timing to use for TAG3. The UE may be configured / indicated to provide an indication (e.g., to the network node) indicative of the selected DL reference timing and / or of which TAG, e.g., between TAG1 and TAG2. In such cases, one TAG may be associated with multiple TAGs, e.g., TAG3 may be associated to both TAG1 and TAG2. The determination / selection may be based on one or more of the following: at least partially up to the UE implementation, select the TAG for which the TA value is the smallest (or the largest), or select the TAG that correspond to lower or larger time offset value. For example, the time offset value may be employed as an offset between the DL reference timing and the actual UL transmission timing, which for example may be given by (NTA +NTA offset) * Tc. In another example, the UE may be specified or configured to use or to determine to use at least two DL reference timings for TAG3; if the UE is doing such determination, the UE may be configured / indicated to provide an indication (to the network node) indicative of the UE using, e.g., two DL reference timings and more specifically considering both TAG1 and TAG2. For example, the UE may use the two DL reference timings by calculating a timing using a function (such as average, or any other function which may be specified or configured) based on the DL reference timings corresponding to TAG1 and TAG2. As another example, the UE may be specified or configured to determine / select a DL reference timing to use for TAG3 depending on whether a TRP corresponding to TAG1 or TAG2 is (dynamically) muted or activated. If the TRP corresponding to TAG1 is muted, the UE may then use DL reference timing corresponding to TAG2.

[0073] FIG. 9 is a block diagram of a wireless station or node (e.g., UE, user device, AP, BS, eNB, gNB, RAN node, network node, TRP, or other node) 1300 according to an example embodiment. The wireless station 1300 may include, for example, one or more (e.g., two as shown in FIG. 9) RF (radio frequency) or wireless transceivers 1302 A, 1302B, where each wireless transceiver includes a transmitter to transmit signals and a receiver to receive signals. The wireless station also includes a processor 1304 or control unit / entity (controller1308) to execute instructions or software and control transmission and receptions of signals, and a memory 1306 to store data and / or instructions.

[0074] Processor 1304 may also make decisions or determinations, generate frames, packets or messages for transmission, decode received frames or messages for further processing, and other tasks or functions described herein. Processor 1304, which may be a baseband processor, for example, may generate messages, packets, frames or other signals for transmission via wireless transceiver 1302 (1302A or 1302B). Processor 1304 may control transmission of signals or messages over a wireless network, and may control the reception of signals or messages, etc., via a wireless network (e.g., after being down-converted by wireless transceiver 1302, for example). Processor 1304 may be programmable and capable of executing software or other instructions stored in memory or on other computer media to perform the various tasks and functions described above, such as one or more of the tasks or methods described above. Processor 1304 may be (or may include), for example, hardware, programmable logic, a programmable processor that executes software or firmware, and / or any combination of these. Using other terminology, processor 1304 and transceiver 1302 together may be considered as a wireless transmitter / receiver system, for example.

[0075] In addition, referring to FIG. 9, a controller 1308 (or processor 1304) may execute software and instructions, and may provide overall control for the station 1300, and may provide control for other systems not shown in FIG. 9, such as controlling input / output devices (e.g., display, keypad), and / or may execute software for one or more applications that may be provided on wireless station 1300, such as, for example, an email program, audio / video applications, a word processor, a Voice over IP application, or other application or software.

[0076] In addition, a storage medium may be provided that includes stored instructions, which when executed by a controller or processor may result in the processor 1304, or other controller or processor, performing one or more of the functions or tasks described above.

[0077] According to another example embodiment, RF or wireless transceiver(s) 1302A / 1302B may receive signals or data and / or transmit or send signals or data. Processor 1304 (and possibly transceivers 1302A / 1302B) may control the RF or wireless transceiver 1302 A or 1302B to receive, send, broadcast or transmit signals or data.

[0078] Example embodiments are provided or described for each of the example methods, including: An apparatus (e.g., 1300, FIG. 9) including means (e.g., processor 1304, RF transceivers 1302A and / or 1302B, and / or memory 1306, in FIG. 9) for carrying out any ofthe methods; a non-transitory computer-readable storage medium (e.g., memory 1306, FIG.9) comprising instructions stored thereon that, when executed by at least one processor (processor 1304, FIG. 9), are configured to cause a computing system (e.g., 1300, FIG. 9) to perform any of the example methods; and an apparatus (e.g., 1300, FIG. 9) including at least one processor (e.g., processor 1304, FIG. 9), and at least one memory (e.g., memory 1306, FIG. 9) including computer program code, the at least one memory (1306) and the computer program code configured to, with the at least one processor (1304), cause the apparatus (e.g., 1300) at least to perform any of the example methods.

[0079] Embodiments of the various techniques described herein may be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. Embodiments may be implemented as a computer program product, i.e., a computer program tangibly embodied in an information carrier, e.g., in a machine-readable storage device or in a propagated signal, for execution by, or to control the operation of, a data processing apparatus, e.g., a programmable processor, a computer, or multiple computers. Embodiments may also be provided on a computer-readable medium or computer-readable storage medium, which may be a non-transitory medium. Embodiments of the various techniques may also include embodiments provided via transitory signals or media, and / or programs and / or software embodiments that are downloadable via the Internet or other network(s), either wired networks and / or wireless networks. In addition, embodiments may be provided via machine type communications (MTC), and also via an Internet of Things (IOT).

[0080] As used in this application, the term “circuitry” or “circuit” refers to all of the following: (a) hardware-only circuit implementations, such as implementations in only analog and / or digital circuitry, and (b) combinations of circuits and soft-ware (and / or firmware), such as (as applicable): (i) a combination of processor(s) or (ii) portions of processor(s) / software including digital signal processor(s), software, and memory(ies) that work together to cause an apparatus to perform various functions, and (c) circuits, such as a microprocessor(s) or a portion of a microprocessor(s), that require software or firmware for operation, even if the software or firmware is not physically present. This definition of “circuitry” applies to all uses of this term in this application. As a further example, as used in this application, the term “circuitry” would also cover an implementation of merely a processor (or multiple processors) or a portion of a processor and its (or their) accompanying software and / or firmware. The term “circuitry” would also cover, for example and if applicable to the particular element, a baseband integrated circuit or applications processorintegrated circuit for a mobile phone or a similar integrated circuit in a server, a cellular network device, or another network device.

[0081] The computer program may be in source code form, object code form, or in some intermediate form, and it may be stored in some sort of carrier, distribution medium, or computer-readable medium, which may be any entity or device capable of carrying the program. Such carriers include a record medium, computer memory, read-only memory, photoelectrical and / or electrical carrier signal, telecommunications signal, and software distribution package, for example. Depending on the processing power needed, the computer program may be executed in a single electronic digital computer, or it may be distributed amongst a number of computers.

[0082] Furthermore, embodiments of the various techniques described herein may use a cyber-physical system (CPS) (a system of collaborating computational elements controlling physical entities). CPS may enable the embodiment and exploitation of massive amounts of interconnected ICT devices (sensors, actuators, processors microcontrollers, ...) embedded in physical objects at different locations. Mobile cyber physical systems, in which the physical system in question has inherent mobility, are a subcategory of cyber-physical systems.Examples of mobile physical systems include mobile robotics and electronics transported by humans or animals. The rise in popularity of smartphones has increased interest in the area of mobile cyber-physical systems. Therefore, various embodiments of techniques described herein may be provided via one or more of these technologies.

[0083] A computer program, such as the computer program(s) described above, can be written in any form of programming language, including compiled or interpreted languages, and can be deployed in any form, including as a standalone program or as a module, component, subroutine, or other unit or part of it suitable for use in a computing environment. A computer program can be deployed to be executed on one computer or on multiple computers at one site or distributed across multiple sites and interconnected by a communication network.

[0084] Method steps may be performed by one or more programmable processors executing a computer program or computer program portions to perform functions by operating on input data and generating output. Method steps also may be performed by, and an apparatus may be implemented as, special purpose logic circuitry, e.g., an FPGA (field programmable gate array) or an ASIC (application specific integrated circuit).

[0085] Processors suitable for the execution of a computer program include, by way of example, both general and special purpose microprocessors, and any one or more processorsof any kind of digital computer, chip or chipset. Generally, a processor will receive instructions and data from a read-only memory or a random access memory or both.Elements of a computer may include at least one processor for executing instructions and one or more memory devices for storing instructions and data. Generally, a computer also may include, or be operatively coupled to receive data from or transfer data to, or both, one or more mass storage devices for storing data, e.g., magnetic, magnetooptical disks, or optical disks. Information carriers suitable for embodying computer program instructions and data include all forms of non-volatile memory, including by way of example semiconductor memory devices, e.g., EPROM, EEPROM, and flash memory devices; magnetic disks, e.g., internal hard disks or removable disks; magneto-optical disks; and CD-ROM and DVD-ROM disks. The processor and the memory may be supplemented by, or incorporated in, special purpose logic circuitry.

[0086] To provide for interaction with a user, embodiments may be implemented on a computer having a display device, e.g., a cathode ray tube (CRT) or liquid crystal display (LCD) monitor, for displaying information to the user and a user interface, such as a keyboard and a pointing device, e.g., a mouse or a trackball, by which the user can provide input to the computer. Other kinds of devices can be used to provide for interaction with a user as well; for example, feedback provided to the user can be any form of sensory feedback, e.g., visual feedback, auditory feedback, or tactile feedback; and input from the user can be received in any form, including acoustic, speech, or tactile input.

[0087] Embodiments may be implemented in a computing system that includes a backend component, e.g., as a data server, or that includes a middleware component, e.g., an application server, or that includes a frontend component, e.g., a client computer having a graphical user interface or a Web browser through which a user can interact with an embodiment, or any combination of such backend, middleware, or frontend components. Components may be interconnected by any form or medium of digital data communication, e.g., a communication network. Examples of communication networks include a local area network (LAN) and a wide area network (WAN), e.g., the Internet.

[0088] While certain features of the described embodiments have been illustrated as described herein, many modifications, substitutions, changes and equivalents will now occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the various embodiments.

[0089] Some examples will be described:

[0090] Example 1. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: receiving from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0091] Example 2. The apparatus of Example 1, wherein the information is further indicative of the second TAG comprising the at least one TRP.

[0092] Example 3. The apparatus of Example 1 or 2, wherein the information is further indicative of association between the first TAG and the second TAG.

[0093] Example 4. The apparatus of Example 3, wherein the association comprises association between an identifier of the first TAG and an identifier of the second TAG.

[0094] Example 5. The apparatus of any of Examples 1 to 4, wherein the apparatus is further caused to perform determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

[0095] Example 6. The apparatus of any of Examples 1 to 5, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0096] Example 7. The apparatus of any of Examples 1 to 6, wherein the information is received as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0097] Example 8. The apparatus of any of Examples 1 to 7, wherein the at least one TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0098] Example 9. The apparatus of any of Examples 1 to 8, wherein the first TAG comprises one or more TRPs.

[0099] Example 10. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplinktransmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0100] Example 11. The apparatus of Example 10, wherein the information is further indicative of the second TAG comprising the at least one TRP.

[0101] Example 12. The apparatus of Example 10 or 11, wherein the information is further indicative of association between the first TAG and the second TAG.

[0102] Example 13. The apparatus of Example 12, wherein the association comprises association between an identifier of the first TAG and an identifier of the second TAG.

[0103] Example 14. The apparatus of any of Examples 10 to 13, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0104] Example 15. The apparatus of any of Examples 10 to 14, wherein the information is transmitted as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0105] Example 16. The apparatus of any of Examples 10 to 15, wherein the at least one TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0106] Example 17. The apparatus of any of Examples 10 to 16, wherein the first TAG comprises one or more TRPs.

[0107] Example 18. An apparatus comprising: means for receiving from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; means for selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and means for performing the uplink transmission based on the TT.

[0108] Example 19. An apparatus comprising: means for transmitting to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and means for receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0109] Example 20. A method comprising: receiving, by a user device from a network node, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the information, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0110] Example 21. The method of Example 20, wherein the information is further indicative of the second TAG comprising the at least one TRP.

[0111] Example 22. The method of Example 20 or 21, wherein the information is further indicative of association between the first TAG and the second TAG.

[0112] Example 23. The method of Example 22, wherein the association comprises association between an identifier of the first TAG and an identifier of the second TAG.

[0113] Example 24. The method of any of Examples 20 to 23, further comprising determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

[0114] Example 25. The method of any of Examples 20 to 24, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0115] Example 26. The method of any of Examples 20 to 25, wherein the information is received as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0116] Example 27. The method of any of Examples 20 to 26, wherein the at least one TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0117] Example 28. The method of any of Examples 20 to 27, wherein the first TAG comprises one or more TRPs.

[0118] Example 29. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of Examples 20 to 28.

[0119] Example 30. A computer program comprising instructions stored thereon for performing a method of any of Examples 20 to 28.

[0120] Example 31. A method comprising: transmitting, by a network node to a user device, information indicative of a first timing advance group (TAG), based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the information.

[0121] Example 32. The method of Example 31, wherein the information is further indicative of the second TAG comprising the at least one TRP.

[0122] Example 33. The method of Example 31 or 32, wherein the information is further indicative of association between the first TAG and the second TAG.

[0123] Example 34. The method of Example 33, wherein the association comprises association between an identifier of the first TAG and an identifier of the second TAG.

[0124] Example 35. The method of any of Examples 31 to 34, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0125] Example 36. The method of any of Examples 31 to 35, wherein the information is transmitted as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0126] Example 37. The method of any of Examples 31 to 36, wherein the at least one TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0127] Example 38. The method of any of Examples 31 to 37, wherein the first TAG comprises one or more TRPs.

[0128] Example 39. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of Examples 31 to 38.

[0129] Example 40. A computer program comprising instructions stored thereon for performing a method of any of Examples 31 to 38.

[0130] Example 41. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting,based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0131] Example 42. The apparatus of Example 41, wherein the one or more rules determines an association between the first TAG and the second TAG.

[0132] Example 43. The apparatus of Example 41 or 42, wherein the one or more rules indicates at least one of: selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list; selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG; selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal; selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG; selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal; selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; or selecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

[0133] Example 44. The apparatus of any of Examples 41 to 43, wherein the one or more rules indicates at least one of: selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; or selecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

[0134] Example 45. The apparatus of Example 44, wherein the TT for the uplink transmission to the at least one TRP of the second TAG is determined based on at least one of: calculating an average of downlink reference timings of the plurality of downlinkreference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; calculating a weighted average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; or calculating a linear combination of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs.

[0135] Example 46. The apparatus of any of Examples 41 to 45, wherein the apparatus is further caused to perform indicating at least one of the selected first TAG, or a downlink reference timing of the selected first TAG to a network node.

[0136] Example 47. The apparatus of any of Examples 41 to 46, wherein the apparatus is further caused to perform determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

[0137] Example 48. The apparatus of any of Examples 41 to 47, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0138] Example 49. The apparatus of any of Examples 41 to 48, wherein: the one or more rules is preconfigured in the apparatus; or the one or more rules is received as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0139] Example 50. The apparatus of any of Examples 41 to 49, wherein the at least one of TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0140] Example 51. An apparatus comprising: at least one processor; and at least one memory storing instructions that, when executed by the at least one processor, cause the apparatus at least to perform: transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0141] Example 52. The apparatus of Example 51, wherein the one or more rules determines an association between the first TAG and the second TAG.

[0142] Example 53. The apparatus of Example 51 or 52, wherein the one or more rules indicates at least one of: selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list; selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG; selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal; selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG; selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal; selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; or selecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

[0143] Example 54. The apparatus of any of Examples 51 to 53, wherein the one or more rules indicates at least one of: selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; or selecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

[0144] Example 55. The apparatus of any of Examples 51 to 54, wherein the apparatus is further caused to perform: receiving from the user device an indication of at least one of the selected first TAG, or a downlink reference timing of the selected first TAG.

[0145] Example 56. The apparatus of any of Examples 51 to 55, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0146] Example 57. The apparatus of any of Examples 51 to 56, wherein the one or more rules is transmitted as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0147] Example 58. The apparatus of any of Examples 51 to 57, wherein the at least one of TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0148] Example 59. An apparatus comprising: means for obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; means for selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and means for performing the uplink transmission based on the TT.

[0149] Example 60. An apparatus comprising: means for transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and means for receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0150] Example 61. A method comprising: obtaining by a user device one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; and performing the uplink transmission based on the TT.

[0151] Example 62. The method of Example 61, wherein the one or more rules determines an association between the first TAG and the second TAG.

[0152] Example 63. The method of Example 61 or 62, wherein the one or more rules indicates at least one of: selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list; selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the firstTAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG; selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal; selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG; selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal; selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; or selecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

[0153] Example 64. The method of any of Examples 61 to 63, wherein the one or more rules indicates at least one of: selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; or selecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

[0154] Example 65. The method of Example 64, wherein the TT for the uplink transmission to the at least one TRP of the second TAG is determined based on at least one of: calculating an average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; calculating a weighted average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; or calculating a linear combination of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs.

[0155] Example 66. The method of any of Examples 61 to 65, further comprising: indicating at least one of the selected first TAG, or a downlink reference timing of the selected first TAG to a network node.

[0156] Example 67. The method of any of Examples 61 to 66, further comprising determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

[0157] Example 68. The method of any of Examples 61 to 67, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0158] Example 69. The method of any of Examples 61 to 68, wherein: the one or more rules is preconfigured in the user device; or the one or more rules is received as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0159] Example 70. The method of any of Examples 61 to 69, wherein the at least one of TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0160] Example 71. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of Examples 61 to 70.

[0161] Example 72. A computer program comprising instructions stored thereon for performing a method of any of Examples 61 to 70.

[0162] Example 73. A method comprising: transmitting, by a network node to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

[0163] Example 74. The method of Example 73, wherein the one or more rules determines an association between the first TAG and the second TAG.

[0164] Example 75. The method of Example 73 or 74, wherein the one or more rules indicates at least one of: selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list; selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of thefirst TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG; selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal; selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG; selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal; selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; or selecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

[0165] Example 76. The method of any of Examples 73 to 75, wherein the one or more rules indicates at least one of: selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; or selecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

[0166] Example 77. The method of any of Examples 73 to 76, further comprising: receiving from the user device an indication of at least one of the selected first TAG, or a downlink reference timing of the selected first TAG.

[0167] Example 78. The method of any of Examples 73 to 77, wherein the uplink transmission comprises at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH).

[0168] Example 79. The method of any of Examples 73 to 78, wherein the one or more rules is transmitted as part of: a radio resource control (RRC) message; or a medium access control (MAC) control element (MAC-CE).

[0169] Example 80. The method of any of Examples 73 to 79, wherein the at least one of TRP of the second TAG supports reception of at least one of: a physical uplink control channel (PUCCH); or a physical uplink shared channel (PUSCH); and does not supporttransmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

[0170] Example 81. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of Examples 73 to 80.

[0171] Example 82. A computer program comprising instructions stored thereon for performing a method of any of Examples 73 to 80.

Claims

WHAT IS CLAIMED IS:

1. An apparatus, comprising:at least one processor; andat least one memorystoring instructions that, when executed by the at least one processor, cause the apparatus at least to perform:obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined;selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; andperforming the uplink transmission based on the TT.

2. The apparatus of claim 1, wherein the one or more rules determines an association between the first TAG and the second TAG.

3. The apparatus of claim 1 or 2, wherein the one or more rules indicates at least one of:selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list;selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG;selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal;selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG;selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal;selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; orselecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

4. The apparatus of any of claims 1 to 3, wherein the one or more rules indicates at least one of:selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; orselecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

5. The apparatus of claim 4, wherein the TT for the uplink transmission to the at least one TRP of the second TAG is determined based on at least one of:calculating an average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs;calculating a weighted average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; or calculating a linear combination of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs.

6. The apparatus of any of claims 1 to 5, wherein the apparatus is further caused to perform indicating at least one of the selected first TAG, or a downlink reference timing of the selected first TAG to a network node.

7. The apparatus of any of claims 1 to 6, wherein the apparatus is further caused to perform determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

8. The apparatus of any of claim 1 to 7, wherein the uplink transmission comprises at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH).

9. The apparatus of any of claims 1 to 8, wherein:the one or more rules is preconfigured in the apparatus; orthe one or more rules is received as part of:a radio resource control (RRC) message; ora medium access control (MAC) control element (MAC-CE).

10. The apparatus of any of claims 1 to 9, wherein the at least one of TRP of the second TAG supports reception of at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH); anddoes not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

11. An apparatus, comprising:at least one processor; andat least one memorystoring instructions that, when executed by the at least one processor, cause the apparatus at least to perform:transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplinktransmission to at least one transmission reception point (TRP) of a second TAG is to be determined; andreceiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

12. The apparatus of claim 11, wherein the one or more rules determines an association between the first TAG and the second TAG.

13. The apparatus of claim 11 or 12, wherein the one or more rules indicates at least one of:selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list;selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG;selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal;selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG;selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal;selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; orselecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

14. The apparatus of any of claims 11 to 13, wherein the one or more rules indicates at least one of:selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; orselecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

15. The apparatus of any of claims 11 to 14, wherein the apparatus is further caused to perform: receiving from the user device an indication of at least one of the selected first TAG, or a downlink reference timing of the selected first TAG.

16. The apparatus of any of claim 11 to 15, wherein the uplink transmission comprises at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH).

17. The apparatus of any of claims 11 to 16, wherein the one or more rules is transmitted as part of:a radio resource control (RRC) message; ora medium access control (MAC) control element (MAC-CE).

18. The apparatus of any of claims 11 to 17, wherein the at least one of TRP of the second TAG supports reception of at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH); anddoes not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

19. An apparatus, comprising:means for obtaining one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined;means for selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; andmeans for performing the uplink transmission based on the TT.

20. An apparatus, comprising:means for transmitting to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; and means for receiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

21. A method, comprising :obtaining by a user device one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined;selecting, based on the one or more rules, at least one downlink reference signal associated with the first TAG to determine the TT for the uplink transmission to the at least one TRP of the second TAG; andperforming the uplink transmission based on the TT.

22. The method of claim 21, wherein the one or more rules determines an association between the first TAG and the second TAG.

23. The method of claim 21 or 22, wherein the one or more rules indicates at least one of:selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list;selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG;selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal;selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG;selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal;selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; orselecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

24. The method of any of claims 21 to 23, wherein the one or more rules indicates at least one of:selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; orselecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

25. The method of claim 24, wherein the TT for the uplink transmission to the at least one TRP of the second TAG is determined based on at least one of:calculating an average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs;calculating a weighted average of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs; orcalculating a linear combination of downlink reference timings of the plurality of downlink reference signals of the plurality of TRPs of the first TAG, or the plurality of downlink reference signals of the plurality of TRPs of the plurality of first TAGs.

26. The method of any of claims 21 to 25, further comprising: indicating at least one of the selected first TAG, or a downlink reference timing of the selected first TAG to a network node.

27. The method of any of claims 21 to 26, further comprising determining the TT for the uplink transmission based on a timing advance (TA) associated with the second TAG.

28. The method of any of claim 21 to 27, wherein the uplink transmission comprises at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH).

29. The method of any of claims 21 to 28, wherein:the one or more rules is preconfigured in the user device; orthe one or more rules is received as part of:a radio resource control (RRC) message; ora medium access control (MAC) control element (MAC-CE).

30. The method of any of claims 21 to 29, wherein the at least one of TRP of the second TAG supports reception of at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH); anddoes not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

31. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of claims 21 to 30.

32. A computer program comprising instructions stored thereon for performing a method of any of claims 21 to 30.

33. A method, comprising:transmitting, by a network node to a user device, one or more rules for selecting a first timing advance group (TAG) based on which a transmission timing (TT) for an uplink transmission to at least one transmission reception point (TRP) of a second TAG is to be determined; andreceiving the uplink transmission based on the TT, wherein the TT is determined based on the one or more rules.

34. The method of claim 33, wherein the one or more rules determines an association between the first TAG and the second TAG.

35. The method of claim 33 or 34, wherein the one or more rules indicates at least one of:selecting the first TAG from a list of TAGs based on an identifier of the first TAG being adjacent to an identifier of the second TAG in the list;selecting from the list, the first TAG with a largest identifier value, wherein the largest identifier value of the first TAG is less than an identifier value of the second TAG; selecting from the list, the first TAG with a smallest identifier value, wherein the smallest identifier value of the first TAG is larger than an identifier value of the second TAG;selecting from the list, a first occurrence of the first TAG that comprises one or more TRPs that support transmission of a downlink reference signal;selecting the first TAG based on receiving a timing advance command (TAC) from at least one TRP of the first TAG for the at least one TRP of the second TAG;selecting, if the first TAG associated with the second TAG does not comprise any TRP that supports transmission of downlink reference signal, a third TAG that is associated with the first TAG and comprises at least one TRP that supports transmission of a downlink reference signal;selecting the first TAG based on a timing advance (TA) value, wherein the TA value is smallest among TAs of a plurality of first TAGs with downlink reference signals, or the TA value is largest among the TAs of the plurality of first TAGs with downlink reference signals; orselecting the first TAG based on a time offset value, wherein the time offset value is smallest among the time offsets of the plurality of first TAGs with downlink reference signals, or the time offset value is largest among the time offsets of the plurality of first TAGs with downlink reference signals.

36. The method of any of claims 33 to 35, wherein the one or more rules indicates at least one of:selecting a plurality of downlink reference signals of a plurality of TRPs of the first TAG for determining the TT for the uplink transmission to the at least one TRP of the second TAG; orselecting a plurality of downlink reference signals of a plurality of TRPs of a plurality of first TAGs for determining the TT for the uplink transmission to the at least one TRP of the second TAG.

37. The method of any of claims 33 to 36, further comprising: receiving from the user device an indication of at least one of the selected first TAG, or a downlink reference timing of the selected first TAG.

38. The method of any of claim 33 to 37, wherein the uplink transmission comprises at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH).

39. The method of any of claims 33 to 38, wherein the one or more rules is transmitted as part of:a radio resource control (RRC) message; ora medium access control (MAC) control element (MAC-CE).

40. The method of any of claims 33 to 39, wherein the at least one of TRP of the second TAG supports reception of at least one of:a physical uplink control channel (PUCCH); ora physical uplink shared channel (PUSCH); anddoes not support transmission of a physical downlink control channel (PDCCH) and a physical downlink shared channel (PDSCH).

41. A non-transitory computer-readable storage medium comprising instructions stored thereon that, when executed by at least one processor, are configured to cause a computing system to perform a method of any of claims 33 to 40.

42. A computer program comprising instructions stored thereon for performing a method of any of claims 33 to 40.

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