WO2021030969A1

WO2021030969A1 - Rlm and rrm measurement for v2x sl

Info

Publication number: WO2021030969A1
Application number: PCT/CN2019/101115
Authority: WO
Inventors: Tao Chen
Original assignee: MediaTek Singapore Pte Ltd
Current assignee: MediaTek Singapore Pte Ltd
Priority date: 2019-08-16
Filing date: 2019-08-16
Publication date: 2021-02-25
Anticipated expiration: 2022-02-16

Abstract

A method, comprising: receiving the information related to RRM/RLM presence; performing RLM/RRM measurement based on pre-configured and/or indicated DMRS locations; and reporting RLM/RRM status to the higher layer depending on the presence of RRM/RLM RS. NR SL RLM/RLM RS in SL has to be confined within the control/data channel (i. e., No standalone RLM-RS), which implies no periodic and fixed RS transmission due to uncertainty of the control/data transmission. Thus, Rx UE(800) has to blindly detect RLM-RS with the risk of no way for differentiation between "no traffic" and "low SINR on RLM-RS", which will impact RLM evaluation for OoS/IS indication. So it is necessary to have the mechanism to support pre-known RLM-RS for UE(800) to perform RRM/RLM. In case of the active traffic transmission, the UE(800) can perform RRM/RLM RS during the evaluation period assuming there is at least one control/data transmission associated with RRM/RLM RS. In case of inactive traffic, the transmission of RLM/RRM RS can be assumed on a configured/pre-defined period, similar to a keep-alive message, for UE(800) to perform the periodic measurement and report IS/OoS indication to the higher layer. Additionally, UE(800) can be informed about the duration without traffic (e. g., by the timer or explicit singling). Then UE(800) may stop RRM/RLM monitoring and just report "no RS" or "unknown" status to the higher layer during the period instead of IS/OoS indication.

Description

RLM AND RRM MEASUREMENT FOR V2X SL

TECHNICAL FIELD

This disclosure relates generally to wireless communications, and, more particularly, to methods and apparatus for radio link monitoring (RLM) and radio resource management (RRM) in communications via SL.

BACKGROUND

The NR sidelink interface, also known as the PC5 interface, connects two user equipments (UEs) directly, without passing through a base station (e.g. a gNB) . The sidelink interface may be used to carry a variety of services, including unicast services between a single pair of peer UEs. When traffic is sent from one UE to another as part of a service, the peer UEs may be referred to as the transmitting UE (Tx UE) and the receiving UE (Rx UE) .

In the existing art, the Rx UE monitors the condition of the radio link between the two UEs, primarily by evaluating the reception of reference signals (RSs) sent by the Tx UE. If the RSs are received with sufficiently poor signal-and-interference-to-noise ratio (SINR) , the Rx UE may declare an out-of-sync (OOS) condition, while if the RSs are received with a good SINR, the Rx UE may declare an in-sync (IS) condition. Indications of the IS or OOS condition, referred to as IS/OOS indications, may be delivered from a lower protocol layer of the Rx UE (for example, a physical (PHY) layer) to an upper layer of the Rx UE (for example, a radio resource control (RRC) layer) , and the upper layer may be responsible for determining when the IS/OOS indications justify declaring a condition of radio link failure (RLF) . The IS/OOS indications may be delivered periodically or aperiodically. This process of monitoring the radio conditions may be referred to as radio link monitoring (RLM) .

The RSs for RLM/RRM on the sidelink interface are not necessarily transmitted periodically; for instance, they may be transmitted in association with user traffic, and not transmitted when there is no user traffic. Such an aperiodic transmission scheme poses a challenge for RLM/RRM, because if the Rx UE measures extremely poor SINR, it cannot easily infer whether this means that RSs were sent but lost over the air (indicating bad link conditions) , or that no RSs were sent at all (in which case the link condition may be good) . The present invention describes methods of data transmission on the sidelink interface that facilitate effective RLM/RRM.

Moreover, considering the 2-stage sidelink physical control channels used on the sidelink interface, RLM/RRM on the sidelink interface can be developed based on 2-stage SCI solutions.

In the conventional single SCI transmission scheme for SL data scheduling, the sidelink physical data channel (PSSCH) can be scheduled by one sidlelink control information (SCI) carried in sidelink physical control channel (PSCCH) . Instead, 2-stage SCI with 2 SCIs can be used for SL sensing/scheduling. In this case, the 1st SCI is used for sensing and/or broadcast communication whereas the 2nd SCI carrying the remaining information for data scheduling of unicast/groupcast data transmission. Typically, the 1 ^st SCI carrying the sensing information targets the larger coverage for sensing by more UEs than the 2 ^nd SCI only targeting the intended UEs.

The 2nd SCI time/frequency location can be derived from the information fields carried in the 1st SCI. The 1st SCI and 2nd SCI can be time domain multiplexed in different symbols and/or frequency domain multiplexed in different RBs (interleaved or non-interleaved) . The 2 ^nd SCI can share/use the time/frequency resources reserved for the data channel. The 2nd SCI can have the link adaptation associated with the data channel link adaptation. 2nd SCI can have the same transmission scheme as the data channel with the same antenna port (s) .

SUMMARY

NR SL RLM/RLM RS in SL has to be confined within the control/data channel (i.e., No standalone RLM-RS) , which implies no periodic and fixed RS transmission due to uncertainty of the control/data transmission. Thus, Rx UE has to blindly detect RLM-RS with the risk of no way for differentiation between “no traffic” and “low SINR on RLM-RS” , which will impact RLM evaluation for OoS/IS indication. So it is necessary to have the mechanism to support pre-known RLM-RS for UE to perform RRM/RLM. In case of the active traffic transmission, the UE can perform RRM/RLM RS during the evaluation period assuming there is at least one control/data transmission associated with RRM/RLM RS. In case of inactive traffic, the transmission of RLM/RRM RS can be assumed on a configured/pre-defined period, similar to a keep-alive message, for UE to perform the periodic measurement and report IS/OoS indication to the higher layer. Additionally, UE can be informed about the duration without traffic (e.g., by the timer or explicit singling) . Then UE may stop RRM/RLM monitoring and just report “no RS” or “unknown” status to the higher layer during the period instead of IS/OoS indication.

For the RS to be used for RRM/RLM measurement, it can be based on the DMRS of the SCI (e.g., 1 ^st SCI and/or 2 ^nd SCI) or CSI-RS/PTRS confined within the control/data channels with presence/location information indicated by the SCI (e.g., 1 ^st SCI and/or 2 ^nd SCI) .

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be more fully understood by reading the subsequent detailed description and examples with references made to the accompanying drawings, wherein:

Fig. 1 shows an exemplary block diagram of a UE (a.k.a device) according to an embodiment of the disclosure.

DETAILED DESCRIPTION OF PREFERRED IMPLEMENTATIONS

Certain terms are used throughout the description and following claims to refer to particular components. As one skilled in the art will appreciate, manufacturers may refer to a component by different names. This document does not intend to distinguish between components that differ in name but not function. In the following description and in the claims, the terms "include" and "comprise" are used in an open-ended fashion, and thus should be interpreted to mean "include, but not limited to ... " . Also, the term "couple" is intended to mean either an indirect or direct electrical connection. Accordingly, if one device is coupled to another device, that connection may be through a direct electrical connection, or through an indirect electrical connection via other devices and connections. The making and using of the embodiments of the disclosure are discussed in detail below. It should be appreciated, however, that the embodiments can be embodied in a wide variety of specific contexts. The specific embodiments discussed are merely illustrative, and do not limit the scope of the disclosure. Some variations of the embodiments are described. Throughout the various views and illustrative embodiments, like reference numbers are used to designate like elements.

The following description is of the best-contemplated mode of carrying out the invention. This description is made for the purpose of illustrating the general principles of the invention and should not be taken in a limiting sense. Note that the 3GPP specifications described herein are used to teach the spirit of the invention, and the invention is not limited thereto.

To support periodic indication of In Sync (IS) or Out of Sync (OoS) in the aperiodic transmission scenario, there is need to secure at least one RLM-RS transmission during a period, e.g., indication interval. In case there is no traffic during the period, it can be done by triggering A-CSI reporting or a kind of keep-alive message or the standalone PSCCH transmission associated with RLM/RRM RS.

For Rx UE to perform RLM measurement, it can blindly detect all candidate RS positions which may be (pre) configured associated with the resource pool (pre) configuration or data/control channel (pre) configuration. If there is at least one measurement on the candidate RS higher than IS threshold, it can be declared as IS for indication to the higher layer. If the measurements on all candidate RSs lower than OoS threshold, it can be declared as OoS for indication to the higher layer.

Additionally, the indication interval can be set to be same as the evaluation period to avoid consecutive IS/OoS indications based on the evaluation over the same set of measurements.

Additionally, in case of the active traffic transmission, the UE can perform RRM/RLM RS during the evaluation period assuming there is at least one control/data transmission associated with RRM/RLM RS. In case of the inactive traffic for transmission, the transmission of RLM/RRM RS can be assumed on a configured/pre-defined period, similar to a keep-alive message, for UE to perform the periodic measurement and report IS/OoS indication to the higher layer. Additionally, UE can be informed about the duration without traffic (e.g., by the timer or explicit singling) . Then UE may stop RRM/RLM monitoring and just report “no RS” or “unknown” status to the higher layer during the period instead of IS/OoS indication.

In case that the UE doesn’ t start to DRX during the “no traffic” period, so it is still monitoring in case some traffic comes. The Tx UE may not necessarily know in advance when traffic will resume for irregular services. Then the problematic case is where the link gets lost during the “no traffic” period, so the Rx UE goes into the altered RLM mode (sending “no RS” or “unknown” indications) and never comes out of it. This could be handled with a (long) timer in the Rx UE, or by waiting for the upper-layer keep-alive to fail.

From signaling perspective, there are several options for RLM mechanism:

Option 1: Rx UE receives MAC CE carrying the endOftraffic marker and inform the physical layer. The physical layer can perform IS/OoS/unknown evaluation and send the indication) to RRC. In this case, it is still a kind of periodic indication regardless of whether the RLM/RRM RS is known or unknown.

Option 2: Rx UE receives MAC CE carrying the endOfTraffic marker and deliver the no traffic information to RRC layer. RRC layer will instruct the physical layer when/how to perform IS/OoS indication, e.g., only during the active traffic period. In this case, periodic indication for IS/OoS is only reported to the higher layer within the evaluation duration indicated by the higher layer by assuming the presence of RLM/RRM-RS transmission in the physical layer.

Option 3: Simialr to Option 2, Rx UE receives MAC CE carrying the endOfTraffic marker and deliver the no traffic information to RRC layer. RRC layer will instruct the physical layer when/how to perform IS/OoS indication. In this case, periodic indication for IS/OoS (i.e., no “unknown” status) is only reported to the higher layer. In case of no traffic period as indicated by the higher layer, UE may not perform the measurement but will still report IS to the higher layer for processing. The higher layer can derive whether it is a valid IS or no traffic. Alternatively, UE may report IS or OoS with the traffic status assumed for evaluation. Then the higher layer can combine the traffic status in the higher layer and the physical layer reports to perform RLM/RLF. Moreover, there can be a supervisory timer to run at RRC layer for controlling physical layer reporting.

For the RS to be used for RRM/RLM measurement, it can be based on the DMRS of the SCI (e.g., 1 ^st SCI and/or 2 ^nd SCI) or CSI-RS/PTRS confined within the control/data channels with presence and/or location information indicated by the SCI (e.g., 1 ^st SCI and/or 2 ^nd SCI) . Due to the larger coverage of the 1 ^st SCI w/o close-loop MIMO typically, it is more reliable and simple to be used for RLM/RRM measurement for SL maintenance.

In addition to the Rx UE based RLM/RRM, Tx UE based RLM/RRM can be used. In case of Tx UE based RLM, there is no need of periodic indication. Instead, the Tx UE can just derive the link quality based on whether it can receive the number of A/Ns as expected. In this case, the aperiodic indication of the IS/OoS can be applied.

Fig. 1 shows an exemplary block diagram of a UE 800 according to an embodiment of the disclosure. The UE 800 can be configured to implement various embodiments of the disclosure described herein. The UE 800 can include a processor 810, a memory 820, and a radio frequency (RF) module 830 that are coupled together as shown in Fig. 1. In different examples, the UE 800 can be a mobile phone, a tablet computer, a desktop computer, a vehicle carried device, and the like.

The processor 810 can be configured to perform various functions of the UE 800 described above with reference to embodiments described before. The processor 810 can include signal processing circuitry to process received or to be transmitted data according to communication protocols specified in, for example, LTE and NR standards. Additionally, the processor 810 may execute program instructions, for example, stored in the memory 820, to perform functions related with different communication protocols. The processor 810 can be implemented with suitable hardware, software, or a combination thereof. For example, the processor 810 can be implemented with application specific integrated circuits (ASIC) , field programmable gate arrays (FPGA) , and the like, that includes circuitry. The circuitry can be configured to perform various functions of the processor 810.

In one example, the memory 820 can store program instructions that, when executed by the processor 810, cause the processor 810 to perform various functions as described herein. The memory 820 can include a read only memory (ROM) , a random access memory (RAM) , a flash memory, a solid state memory, a hard disk drive, and the like.

The RF module 830 can be configured to receive a digital signal from the processor 810 and accordingly transmit a signal to a base station in a wireless communication network via an antenna 840. In addition, the RF module 830 can be configured to receive a wireless signal from a base station and accordingly generate a digital signal which is provided to the processor 810. The RF module 830 can include digital to analog/analog to digital converters (DAC/ADC) , frequency down/up converters, filters, and amplifiers for reception and transmission operations. For example, the RF module 830 can include converter circuits, filter circuits, amplification circuits, and the like, for processing signals on different carriers or bandwidth parts.

The UE 800 can optionally include other components, such as input and output devices, additional CPU or signal processing circuitry, and the like. Accordingly, the UE 800 may be capable of performing other additional functions, such as executing application programs, and processing alternative communication protocols.

The processes and functions described herein can be implemented as a computer program which, when executed by one or more processors, can cause the one or more processors to perform the respective processes and functions. The computer program may be stored or distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with, or as part of, other hardware. The computer program may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems. For example, the computer program can be obtained and loaded into an apparatus, including obtaining the computer program through physical medium or distributed system, including, for example, from a server connected to the Internet.

The computer program may be accessible from a computer-readable medium providing program instructions for use by or in connection with a computer or any instruction execution system. A computer readable medium may include any apparatus that stores, communicates, propagates, or transports the computer program for use by or in connection with an instruction execution system, apparatus, or device. The computer-readable medium can be magnetic, optical, electronic, electromagnetic, infrared, or semiconductor system (or apparatus or device) or a propagation medium. The computer-readable medium may include a computer-readable non-transitory storage medium such as a semiconductor or solid state memory, magnetic tape, a removable computer diskette, a random access memory (RAM) , a read-only memory (ROM) , a magnetic disk and an optical disk, and the like. The computer-readable non-transitory storage medium can include all types of computer readable medium, including magnetic storage medium, optical storage medium, flash medium and solid state storage medium.

While aspects of the present disclosure have been described in conjunction with the specific embodiments thereof that are proposed as examples, alternatives, modifications, and variations to the examples may be made. Accordingly, embodiments as set forth herein are intended to be illustrative and not limiting. There are changes that may be made without departing from the scope of the claims set forth below.

Claims

A method, comprising:

receiving the information related to RRM/RLM presence;

performing RLM/RRM measurement based on (pre-) configured and/or indicated DMRS locations; and

reporting RLM/RRM status to the higher layer depending on the presence of RRM/RLM RS.
The method of claim 1, wherein receiving the information related to RRM/RLM presence is implemented by the signaling about the traffic status and/or a timer associated with the traffic status to derive the presence of RLM/RRM RS for measurement.
The method of claim 1, wherein performing RLM/RRM measurement based on (pre-) configured and/or indicated DMRS locations is based on DMRS of 1 ^st SCI in case of 2-stage SCI or DMRS of SCI or CSI-RS confined within control/data channels with location (pre-) configured and/or indicated in SCI.
The method of claim 1, wherein reporting RLM/RRM status to the higher layer depending on the presence of RRM/RLM RS is an indication to the higher layer about IS or OoS or “unknown” depending on the measurement and traffic status..