WO2020143053A1

WO2020143053A1 - Method, device and computer readable medium for measuring sidelink received signal strength

Info

Publication number: WO2020143053A1
Application number: PCT/CN2019/071472
Authority: WO
Inventors: Dong Li; Yong Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2019-01-11
Filing date: 2019-01-11
Publication date: 2020-07-16
Also published as: CN113273121B; CN113273121A

Abstract

Embodiments of the present disclosure provide a method, device and computer readable medium for measuring sidelink received signal strength. The method comprises obtaining, at a terminal device, a received power measurement on a subchannel of a sidelink in a time interval. The method also comprises determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval. The method further comprises determining signal strength for the subchannel at least in part based on the indication.

Description

METHOD, DEVICE AND COMPUTER READABLE MEDIUM FOR MEASURING SIDELINK RECEIVED SIGNAL STRENGTH

FIELD

Embodiments of the present disclosure generally relate to communication techniques, and more particularly, to method, device and computer readable medium for measuring sidelink received signal strength.

BACKGROUND

Communication technologies have been developed in various communication standards to provide a common protocol that enables different wireless devices to communicate on a municipal, national, regional, and even global level. An example of an emerging communication standard is new radio (NR) , for example, 5G radio access. NR is a set of enhancements to the Long Term Evolution (LTE) mobile standard promulgated by Third Generation Partnership Project (3GPP) . Vehicle-to-everything (V2X) communication is the passing of information from a vehicle to any entity that may affect the vehicle, and vice versa. It is a vehicular communication system that incorporates other more specific types of communication as V2I (vehicle-to-infrastructure) , V2N (vehicle-to-network) , V2V (vehicle-to-vehicle) , V2P (vehicle-to-pedestrian) , V2D (vehicle-to-device) and V2G (vehicle-to-grid) . Since the improvements of NR with respect to LTE, issues regarding NR V2X also need to be addressed.

SUMMARY

In general, example embodiments of the present disclosure provide a solution for measuring sidelink received signal strength.

In a first aspect, there is provided a method for communication. The method comprises obtaining, at a terminal device, a received power measurement on a subchannel of a sidelink in a time interval. The method also comprises determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval. The method further comprises determining signal strength for the subchannel at least in part based on the indication.

In a second aspect, there is provided a device. The device comprises at least one processor; and at least one memory including computer program codes; the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to: obtain, at a terminal device, a received power measurement on a subchannel of a sidelink in a time interval; determine an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval; and determine signal strength for the subchannel at least in part based on the indication.

In a third aspect, there is provided an apparatus for communications. The apparatus comprises means for obtaining a received power measurement on a subchannel of a sidelink in a time interval. The apparatus also comprises means for determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval. The apparatus further comprises means for determining signal strength for the subchannel at least in part based on the indication.

In a fourth aspect, there is provided a computer readable medium comprising program instructions for causing an apparatus to perform at least the method according to the above first aspect.

It is to be understood that the summary section is not intended to identify key or essential features of embodiments of the present disclosure, nor is it intended to be used to limit the scope of the present disclosure. Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Some example embodiments will now be described with reference to the accompanying drawings, where:

Fig. 1 illustrates an example communication network in which embodiments of the present disclosure can be implemented;

Fig. 2 illustrates a flowchart of a method implemented at a terminal device according to embodiments of the present disclosure;

Fig. 3 illustrates a schematic diagram showing an example configuration of a Transmission Time Interval (TTI) according to some embodiments of the present disclosure;

Fig. 4 illustrates a schematic diagram showing an example of reference signal (RS) pattern in frequency domain according to some embodiments of the present disclosure;

Fig. 5 illustrates a schematic diagram showing another example configuration of a TTI according to some embodiments of the present disclosure;

Fig. 6 illustrates a graph showing a simulation result according to some embodiments of the present disclosure; and

Fig. 7 illustrates a simplified block diagram of an apparatus that is suitable for implementing embodiments of the present disclosure.

Throughout the drawings, the same or similar reference numerals represent the same or similar element.

DETAILED DESCRIPTION

Principle of the present disclosure will now be described with reference to some example embodiments. It is to be understood that these embodiments are described only for the purpose of illustration and help those skilled in the art to understand and implement the present disclosure, without suggesting any limitation as to the scope of the disclosure. The disclosure described herein can be implemented in various manners other than the ones described below.

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

References in the present disclosure to “one embodiment, ” “an embodiment, ” “an example embodiment, ” and the like indicate that the embodiment described may include a particular feature, structure, or characteristic, but it is not necessary that every embodiment includes the particular feature, structure, or characteristic. Moreover, such phrases are not necessarily referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with an embodiment, it is submitted that it is within the knowledge of one skilled in the art to affect such feature, structure, or characteristic in connection with other embodiments whether or not explicitly described.

It shall be understood that although the terms “first” and “second” etc. 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. 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.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” , “comprising” , “has” , “having” , “includes” and/or “including” , when used herein, specify the presence of stated features, elements, and/or components etc., but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof.

As used in this application, the term “circuitry” may refer to one or more or all of the following:

(a) hardware-only circuit implementations (such as implementations in only analog and/or digital circuitry) and

(b) combinations of hardware circuits and software, such as (as applicable) :

(i) a combination of analog and/or digital hardware circuit (s) with software/firmware and

(ii) any portions of hardware processor (s) with software (including digital signal processor (s) ) , software, and memory (ies) that work together to cause an apparatus, such as a mobile phone or server, to perform various functions) and

(c) hardware circuit (s) and or processor (s) , such as a microprocessor (s) or a portion of a microprocessor (s) , that requires software (e.g., firmware) for operation, but the software may not be present when it is not needed for operation.

This definition of circuitry applies to all uses of this term in this application, including in any claims. As a further example, as used in this application, the term circuitry also covers an implementation of merely a hardware circuit or processor (or multiple processors) or portion of a hardware circuit or processor and its (or their) accompanying software and/or firmware. The term circuitry also covers, for example and if applicable to the particular claim element, a baseband integrated circuit or processor integrated circuit for a mobile device or a similar integrated circuit in server, a cellular network device, or other computing or network device.

As used herein, the term “communication network” refers to a network following any suitable communication standards, such as Long Term Evolution (LTE) , LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , High-Speed Packet Access (HSPA) , Narrow Band Internet of Things (NB-IoT) and so on. Furthermore, the communications between a terminal device and a network device in the communication network may be performed according to any suitable generation communication protocols, including, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.75G, the third generation (3G) , the fourth generation (4G) , 4.5G, the future fifth generation (5G) communication protocols, and/or any other protocols either currently known or to be developed in the future. Embodiments of the present disclosure may be applied in various communication systems. Given the rapid development in communications, there will of course also be future type communication technologies and systems with which the present disclosure may be embodied. It should not be seen as limiting the scope of the present disclosure to only the aforementioned system.

As used herein, the term “network device” refers to a node in a communication network via which a terminal device accesses the network and receives services therefrom. The network device may refer to a base station (BS) or an access point (AP) , for example, a node B (NodeB or NB) , an evolved NodeB (eNodeB or eNB) , a NR NB (also referred to as a gNB) , a Remote Radio Unit (RRU) , a radio header (RH) , a remote radio head (RRH) , a relay, a low power node such as a femto, a pico, and so forth, depending on the applied terminology and technology.

The term “terminal device” refers to any end device that may be capable of wireless communication. By way of example rather than limitation, a terminal device may also be referred to as a communication device, user equipment (UE) , a Subscriber Station (SS) , a Portable Subscriber Station, a Mobile Station (MS) , or an Access Terminal (AT) . The terminal device may include, but not limited to, a mobile phone, a cellular phone, a smart phone, voice over IP (VoIP) phones, wireless local loop phones, a tablet, a wearable terminal device, a personal digital assistant (PDA) , portable computers, desktop computer, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, vehicle-mounted wireless terminal devices, wireless endpoints, mobile stations, laptop-embedded equipment (LEE) , laptop-mounted equipment (LME) , USB dongles, smart devices, wireless customer-premises equipment (CPE) , an Internet of Things (loT) device, a watch or other wearable, a head-mounted display (HMD) , a vehicle, a drone, a medical device and applications (e.g., remote surgery) , an industrial device and applications (e.g., a robot and/or other wireless devices operating in an industrial and/or an automated processing chain contexts) , a consumer electronics device, a device operating on commercial and/or industrial wireless networks, and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

As mentioned above, V2X has been proposed. LTE V2X sidelink has been defined in LTE Release 14 to support direct communication of basic road safety services (e.g. vehicle status information such as position, speed and heading etc. ) between a vehicle and a vehicle/pedestrian/infrastructure. In LTE Release 15, V2X sidelink was further enhanced with the features of carrier aggregation, higher order modulation and latency reduction to support more diversified services and more stringent service requirements.

In LTE V2X Release 14/15, channel sensing based resource (re) selection and reservation are applied in V2X sidelink mode 4 (in which a UE performs autonomous resource selection) to avoid resource selection collisions as much as possible. Once a UE has a packet to transmit and media access control (MAC) layer instructs physical (PHY) layer to make candidate resource selection, the UE will perform a procedure of candidate resource subset selection based on channel sensing operations. The channel sensing procedure mainly comprises two major operations of: (1) decoding control channel, i.e. physical sidelink control channel (PSCCH) and measuring the reference signal received power (RSRP) of the corresponding data channel, i.e. physical sidelink shared channel (PSSCH) (PSSCH-RSRP) . Based on the RSRP, excluding some resources from the candidate resource set to avoid collisions with relatively high received power and/or high packet priority; (2) measuring the sidelink received signal strength (S-RSS) and obtaining the sidelink received signal strength indicator (S-RSSI) for each subchannel and then ranking the remaining resources and reporting the resources with least S-RSSI to MAC sublayer for final resource determination.

The S-RSSI is defined as the linear average of total received power in the configured subchannel over all SC-FDMA symbols excluding the first and the last symbol in the subframe (i.e., the sidelink TTI) and the final S-RSSI measurements are obtained through averaging the S-RSSI values over multiple periods (which is generally fixed to 100ms in LTE V2X Release 14/15) .

Currently, for NR V2X, it has been agreed that at least two resource allocation modes, i.e. mode 1 and mode 2, are defined for the sidelink transmission where mode 1 is based on gNB-scheduling while mode 2 uses UE-autonomous resource selection potentially based on sidelink channel sensing operations. Further, it has been agreed to study the sidelink measurements in the channel sensing procedure.

Moreover, the sidelink channel sensing operations for UE-autonomous resource selection in LTE V2X Release 14/15 as discussed above assume the support for only periodic V2X traffic. In this case, the measurement of the sidelink received signal strength (for example, S-RSSI) and the averaging operations over multiple successive periods reflect the statistical situations of the resource usage and average received power level which has at least the following functions: a) Probe the sidelink channel/signal whose associated control channel is not decoded e.g. due to severe collisions; b) Filter out the fast fading channel effect and provide more robust measurement reference for sidelink resource selection, c) Flexibly support the case that certain packet is absent in one period but the resource reservation for next period is still needed. In this case, although the packet is not transmitted in that period (thus resource exclusion based on PSSCH-RSRP cannot be done) , the S-RSSI results averaged over multiple periods could potentially protect that resource for next period.

However, in NR V2X sidelink, one significant difference from LTE V2X is that both periodic V2X traffic and aperiodic V2X traffic will be supported for various V2X traffic types e.g., broadcast, groupcast and unicast sidelink transmissions. Meanwhile, in order to improve resource usage efficiency, the periodic and aperiodic V2X packets may coexist in the same resource pool. In this case, the aperiodic packets will have potential negative impact on the channel sensing procedures especially on the measurements of the sidelink received signal strength. This may reduce the benefits of the sensing-based resource selection and degrade the system performance.

According to embodiments of the present disclosure, there is proposed a solution for measuring sidelink received signal strength to solve the above problem and other potential problems. In the proposed solutions, contributions from aperiodic packets to the received signal strength are explicitly or implicitly excluded. In some cases, received power measurement is performed on symbols for data transmission and reference signal (RS) transmission and the S-RSS is determined by explicitly excluding the reference signal received power (RSRP) associated with aperiodic transmission. In some cases, the received power measurement is performed only on symbols for RS transmission based on a configured RS pattern which differentiates periodic transmission and aperiodic transmission. In this way, impact of aperiodic transmission on the measurements of the sidelink received signal strength can be reduced and sidelink measurements used in the sidelink channel sensing procedure for NR V2X or other device-to-device (D2D) communication can be improved.

Principle and implementations of the present disclosure will be described in detail below with reference to Figs. 1-7.

Fig. 1 illustrates an example communication network 100 in which embodiments of the present disclosure can be implemented. The network 100 includes a network device 110, and three

terminal devices

120, 130 and 140 served by the network device 110. The serving area of the network device 110 is called as a cell 102. It is to be understood that the number of network devices and terminal devices is only for the purpose of illustration without suggesting any limitations. The network 100 may include any suitable number of network devices and terminal devices adapted for implementing embodiments of the present disclosure.

The

terminal devices

120, 130 and 140 shown in Fig. 1 may be associated with vehicles. For example, some or all of the

terminal devices

120, 130 and 140 may be vehicle-mounted terminal devices or may be part of a vehicle. Some or all of the

terminal devices

120, 130 and 140 may be associated with infrastructures, pedestrians, other devices or grids. Although embodiments of the present disclosure are described with respect to V2X scenarios, it is understood that embodiments of the present disclosure are equally applicable to any terminal device which enables D2D communications.

In the communication network 100, the network device 110 can communicate data and control information to the

terminal devices

120, 130 and 140, and the

terminal devices

120, 130 and 140 can also communication data and control information to the network device 110. A link from the network device 110 to the

terminal device

120 or 130 or 140 is referred to as a downlink (DL) , while a link from the

terminal device

120 or 130 or 140 to the network device 110 is referred to as an uplink (UL) .

In addition to the communications via the network device 110, the

terminal devices

120, 130 and 140 may communicate with each other via D2D communication links. As used herein, D2D communication links for D2D communications among the

terminal devices

120, 130 and 140 as well as other terminal devices not shown may be referred to as sidelinks. As shown in Fig. 1, the terminal device 120 may communicate with the terminal device 130 via the sidelink 135 and communicate with the terminal device 140 via the sidelink 145. Further, in case where the

terminal devices

120, 130 and 140 are vehicle-mounted terminal devices, the communications related to the

terminal devices

120, 130 and 140 may be referred to as V2X communications.

Communications in the communication system 100 may be implemented according to any proper communication protocol (s) , comprising, but not limited to, cellular communication protocols of the first generation (1G) , the second generation (2G) , the third generation (3G) , the fourth generation (4G) and the fifth generation (5G) and on the like, wireless local network communication protocols such as Institute for Electrical and Electronics Engineers (IEEE) 802.11 and the like, and/or any other protocols currently known or to be developed in the future. Moreover, the communication may utilize any proper wireless communication technology, comprising but not limited to: Code Divided Multiple Address (CDMA) , Frequency Divided Multiple Address (FDMA) , Time Divided Multiple Address (TDMA) , Frequency Divided Duplexer (FDD) , Time Divided Duplexer (TDD) , Multiple-Input Multiple-Output (MIMO) , Orthogonal Frequency Divided Multiple Access (OFDMA) and/or any other technologies currently known or to be developed in the future.

When operating in an autonomous resource selection mode (for example, mode 2 mentioned above) , the

terminal devices

120, 130 and 140 may autonomously select resources for transmission from a resource pool by means of channel sensing procedure. In NR V2X, to better perform the resource selection for sidelink transmission, the

terminal devices

120, 130 and 140 need to exclude the affect of aperiodic transmission during the channel sending procedure.

Now implementations of the present disclosure will be described in detail below with reference to Figs. 2-7. Fig. 2 illustrates a flowchart of an example method 200 in accordance with embodiments of the present disclosure. It is to be understood that the method 200 may include additional blocks not shown and/or may omit some blocks as shown, and the scope of the present disclosure is not limited in this regard. The method 200 can be implemented at a terminal device, such as the terminal device 120 as shown in Fig. 1. Additionally or alternatively, the method 200 can also be implemented at the

terminal devices

130 and 140, as well as other the terminal devices not shown in Fig. 1. Only for the purpose of discussion, the method 200 will be described with reference to Fig. 1 as performed by the terminal device 120.

When the terminal device 120 operating in an autonomous resource selection mode may have a packet to transmit, it may select a candidate resource for transmitting the packet via the sidelink based on a channel sensing procedure. The terminal device 120 may perform the S-RSS measurement as a part of the channel sensing procedure.

At block 210, the terminal device 120 obtains a received power measurement on a subchannel of a sidelink in a time interval. The subchannel may comprise a configurable number of physic resource blocks (PRB) in frequency domain and may be any of the configured subchannels. Although the process of S-RSS measurement is described herein with respect to one subchannel, the terminal device 120 may perform the S-RSS measurement for each configured subchannel.

The time interval may be a part of a TTI. For example, the time interval may comprise all SC-FDMA symbols excluding the first and the last symbol in the TTI. The time interval may comprise symbols for transmitting data (which are referred to as data symbols herein for ease of discussion) and symbols for transmitting RS (which are referred to as RS symbols herein for ease of discussion) .

Now reference is made to Fig. 3, which illustrates a schematic diagram 300 showing an example configuration of a TTI 310 according to some embodiments of the present disclosure. As shown in Fig. 3, the time interval 350 includes the symbols of the TTI 310 excluding the first symbol 311 and the last symbol 321. The first symbol 311 may be configured for automatic gain control and the last symbol 321 may be a punctured symbol as guard time. A RS such as a demodulation reference signal (DMRS) may be transmitted in the RS symbols 301-304, while data may be transmitted in data symbols 311-319 in the same TTI 310. The RS symbols used to transmit the DMRS may be also referred to as DMRS symbols.

The time interval may be defined as other time length and the scope of the present disclosure is not limited in this regard. For example, the time interval may include all the symbols in the TTI 310 when the first symbol 311 and the last symbol 321 are not reserved for other purpose. Alternatively, the time interval may include the symbols 301-304 and 311-319 in the TTI 310 excluding the last symbol 321.

In some embodiments, the terminal device 120 may perform the received power measurement over both the data and RS symbols, as in the channel sensing procedure for the LTE V2X. For example, the terminal device 120 may measure the received power for the data symbols 312-319 and the RS symbols 301-340. For the scenario with mixed periodic transmission and aperiodic transmission, the result of the received power measurement in this case may include the power contribution from the aperiodic transmission, which will be removed in a subsequent step as described below with reference to block 220.

In some embodiments, the terminal device 120 may perform the received power measurement only over the RS symbols (e.g. the RS symbols 301-304) or some of the RS symbols in the time interval 350, based on a predefined RS pattern which differentiates a reference signal associated with periodic transmission and a reference signal associated with aperiodic transmission. For purpose of discussion, these embodiments may be referred to as “RS-only based measurements” . The periodic transmission and aperiodic transmission may employ an orthogonal RS pattern. For example, the orthogonal RS pattern can be implemented in a way of frequency-division multiplexing (FDM) and/or time-division multiplexing (TDM) .

In such embodiments, resources configured for transmitting a RS associated with the periodic transmission may not be occupied by the aperiodic transmission. For the orthogonal RS pattern implemented by means of TDM, different RS symbols in the TTI 310 may be configured to transmit the RSs associated with the periodic transmission and the aperiodic transmission, respectively. For example, the

RS symbols

301 and 303 may be configured to transmit the RS associated with the periodic transmission, while the

RS symbols

302 and 304 may be configured to transmit the RS associated with the aperiodic transmission.

For the orthogonal RS pattern implemented by means of FDM, different resource elements or subcarriers corresponding to the RS symbols may be configured to transmit the RSs associated with the periodic transmission and the aperiodic transmission, respectively. For example, a Comb RS pattern in frequency domain may be employed. Such cases will be described below with reference to Fig. 4.

In such embodiments, since the terminal device 120 is able to distinguish the RS associated with the periodic transmission and the RS associated with the aperiodic transmission, the received power measurement may be performed only based on the power received on the resource (s) used for the RS associated with the periodic transmission. For example, the terminal device 120 may determine, from a configured resource pool of the subchannels over the time interval (e.g. the time interval 350) , a target resource subset for the RS associated with the periodic transmission. In this case, the target resource subset is unoccupied by the aperiodic transmission. The terminal device 120 may then perform the received power measurement only based on the target resource subset. Such embodiments will be described below in detail with reference to Figs. 3, 4 and 5.

Still referring to Fig. 2. At block 220, the terminal device 120 determines an indication for the subchannel at least in part based on the received power measurement. The indication indicates a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval. The determined indication may be in the form of the S-RSSI.

In above embodiments where the received power measurement is performed only based on the RS symbols, i.e. the RS-only based measurements, the indication for the subchannel in the time interval may be determined as the linear average of the total received power over the symbols where the received power measurement is performed. For example, if the received power measurement is performed only based on the

RS symbols

301 and 303, the indication may be the linear average of the total received power over the configured subchannel within the

symbols

301 and 303. In this case, since the power contribution from the aperiodic transmission is not included during the received power measurement, the indication may be simply determined based on the received power measurement at block 210.

In the above embodiments where the received power measurement is performed over the data and RS symbols, additional operations may be required to exclude the power contribution from the aperiodic transmission. The terminal device 120 may determine an initial indication based on a result of the received power measurement. For example, the terminal device 120 may determine an initial S-RSSI, which is the linear average of the total received power over the configured subchannel in the data and RS symbols where the received power measurement is performed, such as, in the data symbols 312-319 and the RS symbols 301-304.

Then, the terminal device 120 may obtain a RSRP associated with the aperiodic transmission in the time interval. For example, the terminal device 120 may measure the RSRP of the aperiodic packet on data channel PSSCH according to the decoded information of corresponding control channel PSCCH or measure the RSRP of the aperiodic packet on the corresponding control channel PSCCH.

The terminal device 120 may then determine the indication based on the initial indication and the RSRP. For example, the indication for the subchannel in the time interval, such as the S-RSSI, may be determined by subtracting a value derived from the RSRP from the corresponding initial indication, e.g. the intial S-RSSI. It is to be noted that if the RSRP is measured over more than one symbol, an average over the more than one symbol should be considered.

At block 230, the terminal device 120 may determine signal strength for the subchannel at least in part based on the indication. In some embodiments, the signal strength for the subchannel may be simply determined as the value of the indication determined at block 220.

In some embodiments, the signal strength for the subchannel may be determined by averaging the indication over multiple sidelink periods. In these embodiments, the terminal device 120 may obtain a further indication for the subchannel determined at least in part based on a further received power measurement on the subchannel in a further time interval. The further time interval precedes the time interval. Then, the terminal device 120 may determine the signal strength for the subchannel based on the indication and the further indication. The signal strength may be an average of the indication and the further indication.

For example, the final S-RSSI for the subchannel may be determined by averaging values of the S-RSSI in multiple time intervals over a configurable number of successive sidelink periods. In this case, the averaging of the S-RSSI values over multiple sidelink periods is performed over a configurable number of successive sidelink periods. The sidelink period here may be the sidelink packet period of the terminal device 120 (e.g. the UE performing the channel sensing) or may be configured by the network device 110 or may be fixed to one specific value.

Therefore, in some embodiments, the further time interval precedes the time interval by a time period. The time period may be based on at least one of: a period of periodic transmission to be performed on the sidelink by the terminal device 120; a value configured by the network device 110 serving the terminal device 120; and a fixed value.

The above described process of sidelink received signal strength measurement is described with respect to one subchannel. The terminal device 120 may apply the same process to each of the configured subchannels such that the resource selection can be performed based on the channel sensing procedure. In this way, impact of aperiodic transmission on the measurements of the sidelink received signal strength can be reduced and the sensing based resource selection may be improved.

As mentioned above, the orthogonal RS pattern may be employed in some embodiments. Such embodiments, i.e. the RS-only based measurements, will be described in detail with reference to Figs. 3-5.

Referring to Fig. 3. For the orthogonal RS pattern implemented in way of TDM, some of the RS symbols 301-304 may be configured for reference signals associated with the periodic packets, while some others of the RS symbols 301-304 may be configured for reference signals associated with the aperiodic packets. Only be way of example, the

RS symbols

301 and 302 may be configured for reference signals associated with the periodic packets, while the

RS symbols

303 and 304 may be configured for reference signals associated with the aperiodic packets.

In such embodiments, to obtain the received power measurement at block 210, the terminal device 120 may first determine the position (s) of the RS symbol (s) for transmitting the reference signal associated with the periodic transmission based on the predefined RS pattern. The terminal device 120 may determine, from the time interval 350, a set of symbols configured for transmitting the reference signal associated with the periodic transmission. For example, the terminal device 120 may determine the positions of the

symbols

301 and 302. Then, the terminal device 120 may determine resources corresponding to the set of symbols. For example, the terminal device 120 may determine the PRBs configured for the subchannel corresponding to the

RS symbols

301 and 302.

As such, the S-RSS measurement will be performed only based on the determined target resource subset, e.g. in this case the resources corresponding to the

RS symbols

301 and 302. In this way, the S-RSS measurement only contains the contribution from the received power of the periodic transmission and the power contribution from the aperiodic transmission can be explicitly removed.

Now referring to Fig. 4, which illustrates a schematic diagram 400 showing an example of a RS pattern in frequency domain according to some embodiments of the present disclosure. For ease of illustration, the RS pattern is shown only in one PRB.

In such embodiments, a RS may only occupy some of the frequencies/subcarriers configured for the subchannel. Fig. 4 shows

RSs

450 and 460 in Comb RS patterns (e.g. Comb DMRS pattern) . The RS 450 is associated with the periodic transmission and the RS 460 is associated with the aperiodic transmission. In a Comb DMRS structure with discontinuous frequency resources, a frequency offset may be used to indicate a starting frequency/subcarrier for the RS relative to a starting frequency of the selected resource.

In this example shown, the Comb RS 450 has a Comb offset of 0, and therefore occupies

subcarriers

0, 2, 4, 6, 8 and 10 of the PRB with 12 subcarriers in total. Likewise, the Comb RS 460 has a Comb offset of 1, and occupies

subcarriers

1, 3, 5, 7, 9 and 11 of the PRB. For the Comb RS 450 transmitted in a certain RS symbol, the RS 450 only occupies the resource elements which are spaced apart evenly in frequency domain, for example, the

resource elements

401, 403, 405, 407, 409 and 411. As a result, the

resource elements

402, 404, 406, 408, 410 and 412 are null resource elements. Likely, for the Comb RS 460 transmitted in a certain RS symbol, the RS 460 only occupies the resource elements which are spaced apart evenly in frequency domain, for example, the

resource elements

422, 424, 426, 428, 430 and 432. As a result, the

resource elements

421, 423, 425, 427, 429 and 431 are null resource elements.

It is to be understood that the Comb RS pattern (Comb-2 RS structure) shown in Fig. 4 is only by way of example, other Comb RS pattern can also be employed. For example, Comb-4 RS structure can be employed with a Comb offset of 0 and 2 for the RS associated with the periodic packets and a Comb offset of 1 and 3 for the RS associated with the aperiodic packets.

Other orthogonal RS patterns than the Comb RS pattern can also be employed. For example, the subcarriers 0-6 of the PRB can be configured for transmitting the RS associated with the periodic packets and the subcarriers 7-11 of the PRB can be configured for transmitting the RS associated with the aperiodic packets.

Therefore, in the embodiments where the orthogonal RS pattern is implemented by way of FDM as described above, the terminal device 120 only need to perform the S-RSS measurement based on the resource elements configured for transmitting the RS associated with the periodic packet.

In such embodiments, to obtain the received power measurement at block 210, the terminal device 120 may determine the target resource subset to perform the received power measurement from the resources corresponding to a RS symbol. The terminal device 120 may determine a set of resource elements in the configured subchannel corresponding to a symbol in the time interval. The symbol is configured for transmitting reference signals associated with the periodic transmission and the aperiodic transmission, for example the RS symbol 301. The terminal device 120 may then select, from the set of resource elements, a subset of resource elements for transmitting the reference signal associated with the periodic transmission. This process for selecting the subset of resource elements may be performed on some or all of RS symbols in the time interval.

For the Comb RS example shown in Fig. 4, the

resource elements

401, 403, 405, 407, 409 and 411 (and other resource elements not shown if any) may be determined as the target resource subset to perform the received power measurement. In this way, the power contribution from the periodic transmission is included in the S-RSS measurement. Similarly, the

resource elements

421, 423, 425, 427, 429 and 431 (and other resource elements not shown if any) may also be determined as the target resource subset. Since the RS 460 is associated with the aperiodic transmission, these resource elements are null. As a result, the received power measured based on these resource elements are zero or very low. In this way, the power contribution from the aperiodic transmission is removed from the S-RSS measurement in an implicit way.

The orthogonal RS pattern implemented in way of FDM as described with reference to Fig. 4 is efficient in time. Therefore, these embodiments are preferred for V2X traffic in particular with high mobility requirements.

In some embodiments, the RS symbols in the time interval may comprise a base RS symbol (s) and an additional RS symbol (s) . The base RS symbol is configured or preconfigured and thus the terminal device 120 may be aware of the position of the base RS symbol. The additional RS symbol (s) is dynamically configured to support high mobility scenarios. Thus the terminal device 120 may be unaware of the position of the additional RS symbol (s) unless the corresponding control channel is decoded by the terminal device 120. That is, the position of the additional RS symbol (s) is to be determined based on control information. In this case, the measurement of S-RSS may be performed only based on the base RS symbol (s) .

Referring to Fig. 5, which illustrates a schematic diagram 500 showing another example configuration of a TTI 510 according to some embodiments of the present disclosure. As shown, the

symbols

511 and 521 are reserved for automatic gain control and for guard time, respectively. The time interval 550 comprises the

base RS symbols

501 and 503 and the

additional RS symbols

502 and 504. As such, the S-RSS measurement described above with reference to Figs. 3 and 4 will be performed over the

base RS symbols

501 and 503.

In such embodiments, the terminal device 120 may determine from the time interval 550 the base RS symbols, e.g. the

base RS symbol

501 and 503 and determine the target resource subset only based on the base RS symbols. The determining of the target resource subset based on the base RS symbol may be performed according to the orthogonal RS pattern as described with reference to Figs. 3 and 4. It is to be noted that aspects described with reference to Figs. 3-5 can be combined as needed.

Fig. 6 illustrates a graph 600 showing a simulation result according to some embodiments of the present disclosure. System level simulations are performed to evaluate the performance gains of the proposed solution. In the simulations, freeway scenario with UE speed of 140kmph is assumed. The broadcast V2X traffic is assumed with 50%UEs having periodic sidelink packets and 50%UEs having aperiodic sidelink packets. For periodic packets, the packet size is 800 bytes in probability 80%or 1200 bytes in probability 20%; while for aperiodic packets, the packet size is uniformly distributed among the values of 200, 400, 600, ..., 2000 bytes. In the simulations, it is assumed that 16QAM with 1/2 rate LDPC coding are used without packet retransmissions. The periodic and aperiodic sidelink packet transmissions share the same resource pool. In the simulations, the sensing-based UE-autonomous resource selection is used and the S-RSSI measurement (i.e. energy measurements shown in the figure) is part of the sidelink channel sensing procedure.

As shown, two energy measurement procedures are compared, wherein the curve 601 for the measurement with removal of aperiodic packet received power using the proposed solution and the curve 602 for the measurement without the removal of the aperiodic packet which means the measured energy contains the contributions from both periodic packets and aperiodic packets. From the simulation results shown in Fig. 6, it can be seen that the proposed measurement procedure for S-RSSI can greatly improve the system performance. For example, at the packet reception ratio (PRR) of 90%, the proposed scheme can improve the sidelink communication range from 180 meters to about 270 meters.

In some embodiments, an apparatus capable of performing the method 200 (for example, the terminal device 120) may comprise means for performing the respective steps of the method 200. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some embodiments, the apparatus comprises: means for obtaining a received power measurement on a subchannel of a sidelink in a time interval; means for determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval; and means for determining signal strength for the subchannel at least in part based on the indication.

In some embodiments, the means for obtaining the received power measurement comprises: means for determining, from a resource set of the subchannel allocated to the time interval, a target resource subset for a reference signal associated with the periodic transmission, the target resource subset being unoccupied by the aperiodic transmission; and means for performing the received power measurement only based on the target resource subset.

In some embodiments, the means for determining the target resource subset comprises: means for determining a set of resource elements corresponding to a symbol in the time interval, the symbol being configured for transmitting reference signals associated with the periodic transmission and the aperiodic transmission; and means for selecting, from the set of resource elements, a subset of resource elements for transmitting the reference signal associated with the periodic transmission.

In some embodiments, resource elements in the subset are evenly spaced apart in frequency domain.

In some embodiments, the means for determining the target resource subset comprises: means for determining, from the time interval, a set of symbols configured for transmitting the reference signal associated with the periodic transmission; and means for determining resources corresponding to the set of symbols.

In some embodiments, the time interval comprises a first symbol and a second symbol for transmitting reference signals, a position of the first symbol being configured or preconfigured and a position of the second symbol being to be determined based on control information. The means for determining the target resource subset comprises: means for determining, from the time interval, the first symbol; and means for determining the target resource subset only based on the first symbol.

In some embodiments, the reference signal comprises a demodulation reference signal.

In some embodiments, the means for determining the indication for the subchannel comprises: means for determining an initial indication based on a result of the received power measurement; means for obtaining reference signal receiving power, RSRP, associated with the aperiodic transmission in the time interval; and means for determining the indication based on the initial indication and the RSRP.

In some embodiments, the means for determining the signal strength for the subchannel comprises: means for obtaining a further indication for the subchannel determined at least in part based on a further received power measurement on the subchannel in a further time interval, the further time interval preceding the time interval; and means for determining the signal strength for the subchannel based on the indication and the further indication.

In some embodiments, the further time interval precedes the time interval by a time period and the time period is based on at least one of: a period of periodic transmission to be performed on the sidelink by the terminal device; a value configured by a network device serving a terminal device; and a fixed value.

Fig. 7 is a simplified block diagram of a device 700 that is suitable for implementing embodiments of the present disclosure. The device 700 can be considered as a further example implementation of the

terminal device

120 or 130 or 140 as shown in Fig. lA. Accordingly, the device 700 can be implemented at or as at least a part of the

terminal device

120 or 130 or 140.

As shown, the device 700 includes a processor 710, a memory 720 coupled to the processor 710, a suitable transmitter (TX) and receiver (RX) 740 coupled to the processor 710, and a communication interface coupled to the TX/RX 740. The memory 710 stores at least a part of a program 730. The TX/RX 740 is for bidirectional communications. The TX/RX 740 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and a terminal device.

The program 730 is assumed to include program instructions that, when executed by the associated processor 710, enable the device 700 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Fig. 2 and Fig. 5. The embodiments herein may be implemented by computer software executable by the processor 710 of the device 700, or by hardware, or by a combination of software and hardware. The processor 710 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 710 and memory 710 may form processing means 750 adapted to implement various embodiments of the present disclosure.

The memory 710 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 710 is shown in the device 700, there may be several physically distinct memory modules in the device 700. The processor 710 may be of any type suitable to the local technical network, and may include one or more of general-purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 700 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

Generally, various embodiments of the present disclosure may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. Some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device. While various aspects of embodiments of the present disclosure are illustrated and described as block diagrams, flowcharts, or using some other pictorial representation, it will be appreciated that the blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to any of Figs. 2 and 5. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

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

The above program code may be embodied on a machine readable medium, which may be any tangible medium that may contain, or store a program for use by or in connection with an instruction execution system, apparatus, or device. The machine readable medium may be a machine readable signal medium or a machine readable storage medium. A machine readable medium may include but not limited to an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples of the machine readable storage medium would include an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM) , a read-only memory (ROM) , an erasable programmable read-only memory (EPROM or Flash memory) , an optical fiber, a portable compact disc read-only memory (CD-ROM) , an optical storage device, a magnetic storage device, or any suitable combination of the foregoing.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

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

Claims

A method for communication, comprising:

obtaining, at a terminal device, a received power measurement on a subchannel of a sidelink in a time interval;

determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval; and

determining signal strength for the subchannel at least in part based on the indication.
The method of claim 1, wherein obtaining the received power measurement comprises:

determining, from a resource set of the subchannel in the time interval, a target resource subset for a reference signal associated with the periodic transmission, the target resource subset being unoccupied by the aperiodic transmission; and

performing the received power measurement only based on the target resource subset.
The method of claim 2, wherein determining the target resource subset comprises:

determining a set of resource elements corresponding to a symbol in the time interval, the symbol being configured for transmitting reference signals associated with the periodic transmission and the aperiodic transmission; and

selecting, from the set of resource elements, a subset of resource elements for transmitting the reference signal associated with the periodic transmission.
The method of claim 3, wherein resource elements in the subset are evenly spaced apart in frequency domain.
The method of claim 2, wherein determining the target resource subset comprises:

determining, from the time interval, a set of symbols configured for transmitting the reference signal associated with the periodic transmission; and

determining resources corresponding to the set of symbols.
The method of claim 2, wherein the time interval comprises a first symbol and a second symbol for transmitting reference signals, a position of the first symbol being configured or preconfigured and a position of the second symbol being to be determined based on control information, and determining the target resource subset comprises:

determining, from the time interval, the first symbol; and

determining the target resource subset only based on the first symbol.
The method of claim 2, wherein the reference signal comprises a demodulation reference signal.
The method of claim 1, wherein determining the indication for the subchannel comprises:

determining an initial indication based on a result of the received power measurement;

obtaining reference signal receiving power, RSRP, associated with the aperiodic transmission in the time interval; and

determining the indication based on the initial indication and the RSRP.
The method of claim 1, wherein determining the signal strength for the subchannel comprises:

obtaining a further indication for the subchannel determined at least in part based on a further received power measurement on the subchannel in a further time interval, the further time interval preceding the time interval; and

determining the signal strength for the subchannel based on the indication and the further indication.
The method of claim 9, wherein the further time interval precedes the time interval by a time period and the time period is based on at least one of:

a period of periodic transmission to be performed on the sidelink by the terminal device;

a value configured by a network device serving the terminal device; and

a fixed value.
A device comprising:

at least one processor; and

at least one memory including computer program codes;

the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

obtain, at a terminal device, a received power measurement on a subchannel of a sidelink in a time interval;

determine an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval; and

determine signal strength for the subchannel at least in part based on the indication.
The device of claim 11, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

determine, from a resource set of the subchannel in the time interval, a target resource subset for a reference signal associated with the periodic transmission, the target resource subset being unoccupied by the aperiodic transmission; and

perform the received power measurement only based on the target resource subset.
The device of claim 12, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

determine a set of resource elements corresponding to a symbol in the time interval, the symbol being configured for transmitting reference signals associated with the periodic transmission and the aperiodic transmission; and

select, from the set of resource elements, a subset of resource elements for transmitting the reference signal associated with the periodic transmission.
The device of claim 13, wherein resource elements in the subset are evenly spaced apart in frequency domain.
The device of claim 12, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

determine, from the time interval, a set of symbols configured for transmitting the reference signal associated with the periodic transmission; and

determine resources corresponding to the set of symbols.
The device of claim 12, wherein the time interval comprises a first symbol and a second symbol for transmitting reference signals, a position of the first symbol being configured or preconfigured and a position of the second symbol being to be determined based on control information, and the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

determine, from the time interval, the first symbol; and

determine the target resource subset only based on the first symbol.
The device of claim 12, wherein the reference signal comprises a demodulation reference signal.
The device of claim 11, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

determine an initial indication based on a result of the received power measurement;

obtain reference signal receiving power, RSRP, associated with the aperiodic transmission in the time interval; and

determine the indication based on the initial indication and the RSRP.
The device of claim 11, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, cause the device to:

obtain a further indication for the subchannel determined at least in part based on a further received power measurement on the subchannel in a further time interval, the further time interval preceding the time interval; and

determine the signal strength for the subchannel based on the indication and the further indication.
The device of claim 19, wherein the further time interval precedes the time interval by a time period and the time period is based on at least one of:

a period of periodic transmission to be performed on the sidelink by the terminal device;

a value configured by a network device serving the terminal device; and

a fixed value.
An apparatus for communications comprising:

means for obtaining a received power measurement on a subchannel of a sidelink in a time interval;

means for determining an indication for the subchannel at least in part based on the received power measurement, the indication indicating a received power associated with periodic transmission in the time interval without indicating a received power associated with aperiodic transmission in the time interval; and

means for determining signal strength for the subchannel at least in part based on the indication.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of claims 1-10.