WO2023109422A1

WO2023109422A1 - Method and appratus for rach procedure with transmission configuration indicatior (tci) state indication

Info

Publication number: WO2023109422A1
Application number: PCT/CN2022/132541
Authority: WO
Inventors: Cheng-Rung Tsai; Yi-Ru Chen
Original assignee: Mediatek Inc.
Priority date: 2021-12-17
Filing date: 2022-11-17
Publication date: 2023-06-22
Also published as: TW202329741A; WO2023109422A9

Abstract

A method for random access channel (RACH) procedure is proposed. The network node allocates a transmission configuration indicator (TCI) state associated with the RACH procedure for a user equipment (UE) and transmits a command triggering the RACH procedure for a candidate cell to the UE. The UE determines the RACH resource configured to the candidate cell based on the TCI state associated with the candidate cell. Then, the UE transmits a message on the RACH resource to the network node.

Description

METHOD AND APPRATUS FOR RACH PROCEDURE WITH TRANSMISSION CONFIGURATION INDICATIOR (TCI) STATE INDICATION

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119 from U.S. Provisional Application Number 63/290,743, entitled “RACH Procedure with TCI State Activation/Indication” , filed on December 17, 2021, the subject matter of which is incorporated herein by reference.

TECHNICAL FIELD

The disclosed embodiments relate generally to wireless communication, and, more particularly, to random access channel (RACH) procedure with transmission configuration indicator (TCI) statue activation/indication.

BACKGROUND

The wireless communications network has grown exponentially over the years. A long-term evolution (LTE) system offers high peak data rates, low latency, improved system capacity, and low operating cost resulting from simplified network architecture. LTE systems, also known as the 4G system, also provide seamless integration to older wireless network, such as GSM, CDMA and universal mobile telecommunication system (UMTS) . In LTE systems, an evolved universal terrestrial radio access network (E-UTRAN) includes a plurality of evolved Node-Bs (eNodeBs or eNBs) communicating with a plurality of mobile stations, referred to as user equipments (UEs) . The 3rd generation partner project (3GPP) network normally includes a hybrid of 2G/3G/4G systems. The next generation mobile network (NGMN) board, has decided to focus the future NGMN activities on defining the end-to-end requirements for 5G new radio (NR) systems.

In conventional 5G technology, after the UE triggers a cell change or a handover procedure through a radio resource control (RRC) signaling, the downlink synchronization (DL sync) operations and the uplink (UL) sync operations (e.g., a random access channel (RACH) procedure) will just be performed. However, in current RACH procedure, there is no TCI state associated with the RACH procedure. The UE may not have enough information to perform the RACH procedure. In addition, in current RACH procedure, the DL sync operations and the UL sync operations needs to be operated based on two separate procedures.

Therefore, a solution is sought.

SUMMARY

A method for random access channel (RACH) procedure is proposed. The network node may allocate a transmission configuration indicator (TCI) state associated with the RACH procedure for a user equipment (UE) and transmit a command which triggers the RACH procedure for a candidate cell to the UE. The UE may determine the RACH resource configured to the candidate cell based on the TCI state associated with the candidate cell. In addition, the UE may transmit a message on the RACH resource to the network node. When the command indicates that the RACH procedure associated with the TCI is triggered for the cell change or the handover, the UE may trigger a cell change or a handover based on the TCI state. Therefore, in the invention, the TCI state can be associated with the RACH procedure and the DL sync operations and the UL sync operations can be combined in the same procedure.

In one embodiment, a user equipment (UE) may receive a command from a network node, wherein the command triggers a random access channel (RACH) procedure for a candidate cell. The UE may determine a RACH resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell. In addition, the UE may transmit a message on the RACH resource to the network node.

In one embodiment, the UE further monitor a random access response (RAR) for the RACH procedure based on the TCI state. In addition, when the command indicates that the RACH procedure is triggered for the cell change or the handover, the UE may further trigger a cell change or a handover based on the TCI state.

Other embodiments and advantages are described in the detailed description below. This summary does not purport to define the invention. The invention is defined by the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, where like numerals indicate like components, illustrate embodiments of the invention.

Figure 1 illustrates an exemplary 5G new radio (NR) network 100 in accordance with aspects of the current invention.

Figure 2 is a simplified block diagram of a network node and a user equipment that carry out certain embodiments of the present invention.

Figure 3 illustrates a RACH procedure for cell change or handover in accordance with one novel aspect.

Figure 4 is a flow chart of a method for RACH procedure in accordance with one novel aspect.

Figure 5 is a flow chart of a method for RACH procedure in accordance with another novel aspect.

DETAILED DESCRIPTION

Reference will now be made in detail to some embodiments of the invention, examples of which are illustrated in the accompanying drawings.

Figure 1 illustrates an exemplary 5G new radio (NR) network 100 in accordance with aspects of the current invention. The 5G NR network 100 comprises a network node 101 communicatively connected to a user equipment (UE) 102 operating in a licensed band (e.g., 30GHz～300GHz for mmWave) of an access network 110 which provides radio access using a Radio Access Technology (RAT) (e.g., the 5G NR technology) . The access network 110 is connected to a 5G core network 120 by means of the NG interface, more specifically to a User Plane Function (UPF) by means of the NG user-plane part (NG-u) , and to a Mobility Management Function (AMF) by means of the NG control-plane part (NG-c) . One gNB can be connected to multiple UPFs/AMFs for the purpose of load sharing and redundancy. The network node 101 may be a base station (BS) or a gNB. The UE 102 may be a smart phone, a wearable device, an Internet of Things (IoT) device, and a tablet, etc. Alternatively, UE 102 may be a Notebook (NB) or Personal Computer (PC) inserted or installed with a data card which includes a modem and RF transceiver (s) to provide the functionality of wireless communication.

The network node 101 may provide communication coverage for a geographic coverage area in which communications with the UE 102 is supported via a communication link 103. The communication link 103 between the network node 101 and the UE 102 may utilize one or more frequency carriers to form one or more cells (e.g., a PCell and one or more SCells) . The communication link 103 shown in the 5G NR network 100 may include uplink transmissions from the UE 102 to the network node 101 (e.g., on the Physical Uplink Control Channel (PUCCH) or Physical Uplink Shared Channel (PUSCH) ) or downlink transmissions from the network node 101 to the UE 102 (e.g., on the Physical Downlink Control Channel (PDCCH) or Physical Downlink Shared Channel (PDSCH)) .

In accordance with one novel aspect, the UE 102 may receive a command from the network node 101. The command may trigger a random access channel (RACH) procedure for a candidate cell. Then, the UE 102 may perform RACH procedure based on the command. Specifically, the UE 102 may determine a RACH resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell. The UE 102 may receive the command based on the TCI state. In addition, the UE 102 may transmit the message or information corresponding to the RACH procedure on the RACH resource to the network 101.

In accordance with one novel aspect, the command from the network node 101 may indicate at least an index of the TCI state. In addition, the command may indicate at least a preamble index of the RACH procedure and a physical RACH (PRACH) mask index for contention free random access (CFRA) .

In an example, the command may be a downlink control information (DCI) which indicates the TCI state to the UE 102 at least for downlink (DL) reception. In another example, the command may be a medium access control (MAC) -control element (CE) which indicates the TCI state to UE 102 at least for the activation of the TCI state. In the application, the command may indicate that the RACH procedure is triggered for handover (or cell change) or indicate that the RACH procedure is triggered for other operations (e.g., timing advance (TA) acquisition) .

In accordance with one novel aspect, the UE 102 may select or determine a synchronization signal (SS) and physical broadcast channel (PBCH) block (SSB) or a channel status information (CSI) -reference signal (RS) based on the TCI state associated with the RACH procedure. That is to say, the triggered RACH procedure may be associated with the SSB or the CSI-RS which is determined or selected by the UE 102 based on the TCI state. The SSB or the CSI-RS may be a source RS associated with at least quasi co location (QCL) -Type D which is directly or indirectly associated with the TCI-state.

In accordance with one novel aspect, the TCI state associated with the RACH procedure may be associated with an addition physical cell index (PCI) corresponding to a candidate cell. That is to say, if the TCI state is associated with an addition PCI, the SSB or the CSI-RS may be associated with the addition PCI. In addition, the PRACH resource may be associated with the SSB or the CSI-RS. The network node 101 may configure the parameters of RACH resource configuration (e.g., RACH configuration and RACH occasion) to the UE 102 per additional PCI. In an example, the UE 102 may determine or select the RACH resource corresponding to the SSB or the CSI-RS. In another example, the network node 101 may assign the RACH resource corresponding to the SSB or the CSI-RS through the RACH resource configuration. In another example, the UE 102 may determine or select the RACH resource corresponding to the SSB or the CSI-RS and the network node 101 may assign the RACH resource corresponding to the SSB or the CSI-RS through the RACH resource configuration.

In accordance with one novel aspect, the UE 102 may determine a spatial transmission (Tx) filter based on the TCI state associated with the RACH procedure.

In accordance with one novel aspect, after the UE 102 transmits the message or information corresponding to the RACH procedure on the RACH resource to the network 101, the UE 102 may monitor and receive a random access response (RAR) for the RACH procedure based on the TCI state.

In accordance with one novel aspect, when the UE 102 monitors the RAR for the RACH procedure based on the TCI state, the UE 102 may detect downlink control information (DCI) on a control channel by assuming demodulation reference signal (DM-RS) antenna port quasi-co-location (QCL) properties based on the TCI state. In addition, the UE 102 may receive RAR by assuming the DM-RS antenna port QCL properties based on the TCI state. The UE 102 may determine a setting of the control channel. In an example, the UE 102 may determine a setting of the control channel based on a configuration of a serving cell associated with the RACH procedure (or the cell triggering the RACH procedure) . In another example, the UE 102 may determine a setting of the control channel based on a configuration of a candidate cell associated with the TCI state. In another example, the UE 102 may determine a setting of the control channel based on a system information block (SIB) associated with an SSB determined based on the TCI state.

In accordance with one novel aspect, the network 101 may indicate the UE 102 whether to monitor the RAR or not. In an example, the network 101 may indicate the UE 102 whether to monitor the RAR or not through the command associated with the RACH procedure. In other words, the command may indicate whether the UE 102 needs to monitor RAR for the RACH procedure. If the command indicates that UE doesn’ t need to monitor RAR for the RACH procedure, it means the UE only needs to transmit a random access preamble to network.

In accordance with one novel aspect, the UE 102 may apply an initial timing advance (TA) value indicated in the RAR or a TA command to an TA group associated with the TCI state.

In accordance with one novel aspect, if the command indicates that the RACH procedure is triggered for the cell change or the handover, the UE 102 may transmit the message or information (e.g., a random access preamble) corresponding to the RACH procedure on the RACH resource to another network node in the candidate cell (or target cell) . After the UE 102 receives the RAR from the network node in the candidate cell (or target cell) , the UE 102 may perform a cell change or a handover based on the TCI state.

Figure 2 is a simplified block diagram of a network node and a user equipment (UE) that carry out certain embodiments of the present invention. The network node 201 may be a base station (BS) or a gNB, but the present invention should not be limited thereto. The UE 202 may be a smart phone, a wearable device, an Internet of Things (IoT) device, and a tablet, etc. Alternatively, UE 202 may be a Notebook (NB) or Personal Computer (PC) inserted or installed with a data card which includes a modem and RF transceiver (s) to provide the functionality of wireless communication.

Network node 201 has an antenna array 211 having multiple antenna elements that transmits and receives radio signals, one or more RF transceiver modules 212, coupled with the antenna array 211, receives RF signals from antenna array 211, converts them to baseband signal, and sends them to processor 213. RF transceiver 212 also converts received baseband signals from processor 213, converts them to RF signals, and sends out to antenna array 211. Processor 213 processes the received baseband signals and invokes different functional modules 220 to perform features in network node 201. Memory 214 stores program instructions and data 215 to control the operations of network node 201. Network node 201 also includes multiple function modules that carry out different tasks in accordance with embodiments of the current invention.

Similarly, UE 202 has an antenna array 231, which transmits and receives radio signals. A RF transceiver 232, coupled with the antenna, receives RF signals from antenna array 231, converts them to baseband signals and sends them to processor 233. RF transceiver 232 also converts received baseband signals from processor 233, converts them to RF signals, and sends out to antenna array 231. Processor 233 processes the received baseband signals and invokes different functional modules 240 to perform features in UE 202. Memory 234 stores program instructions and data 235 to control the operations of UE 202. UE 202 also includes multiple function modules and circuits that carry out different tasks in accordance with embodiments of the current invention.

The functional modules and

circuits

220 and 240 can be implemented and configured by hardware, firmware, software, and any combination thereof. The function modules and

circuits

220 and 240, when executed by the processors 213 and 233 (e.g., via executing program codes 215 and 235) , allow network node 201 and UE 202 to perform embodiments of the present invention.

In the example of Figure 2, the network node 201 may comprise a resource allocation circuit 221 and a configuration circuit 222. Resource allocation circuit 221 may allocate a transmission configuration indicator (TCI) state associated with the RACH procedure for the UE 202. Configuration circuit 222 may transmit a command which triggers the RACH procedure for a candidate cell to the UE 202.

In the example of Figure 2, the UE 202 may comprise a determination circuit 241 and a report circuit 242. Determination circuit 241 may trigger the PRACH procedure based on the command from the network node 201 and determine the RACH resource configured to the candidate cell based on the TCI state associated with the candidate cell. Report circuit 242 may transmit message or information (e.g., a random access preamble) corresponding to the RACH procedure on the RACH resource to the network node 201.

Figure 3 illustrates a RACH procedure for cell change or handover in accordance with one novel aspect. In step 310, the network node 301 in the serving cell transmits a command to the UE 302. The command triggers a RACH procedure for a candidate cell.

In step 320, the UE 302 determine a RACH resource configured to the candidate cell based on a TCI state associated with the candidate cell. The UE 302 may receive the command based on the TCI state associated with the candidate cell.

In step 330, the UE 302 transmits the message or information (e.g., a random access preamble) for the RACH procedure on the RACH resource to the network node 303 in the candidate cell (or target cell) .

Steps

320 and 330 may be applied to Msg1 of the conventional RACH procedure.

In step 340, the UE 302 may monitor the RAR for the RACH procedure based on the TCI state. The command may indicate whether the UE 302 needs to monitor the RAR for the RACH procedure.

In step 350, the network node 303 in the candidate cell may transmit the RAR for the RACH procedure to the UE 302.

Steps

340 and 350 may be applied to Msg2 of the conventional RACH procedure.

In step 360, the UE 302 may perform a cell change or a handover based on the TCI state (i.e., switch from the serving cell to the target cell) .

Figure 4 is a flow chart of a method for RACH procedure in accordance with one novel aspect. In step 401, a user equipment (UE) receives a command from a network node, wherein the command triggers a random access channel (RACH) procedure for a candidate cell.

In step 402, the UE determines a RACH resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell. In this embodiment, the UE 402 may receive the command based on the TCI state associated with the candidate cell.

In step 403, the UE transmits a message on the RACH resource to the network node.

Figure 5 is a flow chart of a method for RACH procedure in accordance with another novel aspect. In step 501, a user equipment (UE) receives a command from a first network node in a serving cell, wherein the command triggers a random access channel (RACH) procedure for a candidate cell. In this embodiment, the command further indicates that the RACH procedure is triggered for the cell change or the handover.

In step 502, the UE determines a RACH resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell. In this embodiment, the UE 502 may receive the command based on the TCI state associated with the candidate cell.

In step 503, the UE transmits a message on the RACH resource to a second network node in a candidate cell (or target cell) .

In step 504, the UE receives a random access response (RAR) for the RACH procedure from the second network node.

In step 505, the UE triggers a cell change or a handover based on the TCI state.

Although the present invention has been described in connection with certain specific embodiments for instructional purposes, the present invention is not limited thereto. Accordingly, various modifications, adaptations, and combinations of various features of the described embodiments can be practiced without departing from the scope of the invention as set forth in the claims.

Claims

A method, comprising:

receiving, by a user equipment (UE) , a command from a network node, wherein the command triggers a random access channel (RACH) procedure for a candidate cell; and

determining, by the UE, a RACH resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell; and

transmitting, by the UE, a message on the RACH resource to the network node.
The method of Claim 1, wherein the command indicates at least an index of the TCI state.
The method of Claim 1, wherein the command is received by the UE based on the TCI state.
The method of Claim 1, wherein the command indicates at least a preamble index and a PRACH mask index.
The method of Claim 1, wherein the command is a downlink control information (DCI) or a medium access control (MAC) -control element (CE) .
The method of Claim 1, wherein the triggered RACH procedure is associated with a synchronization signal (SS) and physical broadcast channel (PBCH) block (SSB) or a channel status information (CSI) -reference signal (RS) which is determined based on the TCI state, and wherein the RACH resource is associated with the SSB or the CSI-RS.
The method of Claim 1, further comprising:

monitoring, by the UE, a random access response (RAR) for the RACH procedure based on the TCI state.
The method of Claim 1, wherein the command indicates whether the UE need to monitor RAR for the RACH procedure.
The method of Claim 7, further comprising:

performing, by the UE, a cell change or a handover based on the TCI state after receiving the RAR in an event that the command indicates that the RACH procedure is triggered for the cell change or the handover.
The method of Claim 7, wherein the monitoring comprising:

detecting a downlink control information (DCI) on a control channel by assuming demodulation reference signal (DM-RS) antenna port quasi-co-location (QCL) properties based on the TCI state.
The method of Claim 10, further comprising:

determining, by the UE, a setting of the control channel based on at least one of a configuration of a serving cell associated with the RACH procedure, a configuration of a candidate cell associated with the TCI state and a system information block (SIB) associated with an SSB determined based on the TCI state.
The method of Claim 7, further comprising:

applying, by the UE, an initial timing advance (TA) value indicated in the RAR or a TA command to an TA group associated with the TCI state.
A user equipment (UE) , comprising:

a receiver, receiving a command from a network node, wherein the command triggers a random access channel (RACH) procedure for a candidate cell;

a processor, determining a RACH) resource configured to the candidate cell based on a transmission configuration indicator (TCI) state associated with the candidate cell; and

a transmitter, transmitting a message on the RACH resource to the network node.
The UE of Claim 13, wherein the command indicates at least an index of the TCI state and the command is received by the UE based on the TCI state.
The UE Claim 13, wherein the command is a downlink control information (DCI) or a medium access control (MAC) -control element (CE) .
The UE of Claim 13, wherein the triggered RACH procedure is associated with a synchronization signal (SS) and physical broadcast channel (PBCH) block (SSB) or a channel status information (CSI) -reference signal (RS) which is determined based on the TCI state, and wherein the PRACH resource is associated with the SSB or the CSI-RS.
The UE of Claim 13, wherein the processor further monitors a random access response (RAR) for the RACH procedure based on the TCI state, and wherein the command indicates whether the UE needs to monitor RAR for the RACH procedure.
The UE of Claim 17, wherein the processor performs a cell change or a handover based on the TCI state after receiving the RAR in an event that the command indicates that the RACH procedure is triggered for the cell change or the handover.
The UE of Claim 17, wherein the processor further detects a downlink control information (DCI) on a control channel by assuming demodulation reference signal (DM-RS) antenna port quasi-co-location (QCL) properties based on the TCI state.
The UE of Claim 19, wherein the processor further determines a setting of the control channel based on one of a configuration of a serving cell associated with the RACH procedure, a configuration of a candidate cell associated with the TCI state and a system information block (SIB) associated with an SSB determined based on the TCI state.