WO2023168676A1

WO2023168676A1 - Sidelink ranging and positioning

Info

Publication number: WO2023168676A1
Application number: PCT/CN2022/080250
Authority: WO
Inventors: Mikko SÄILY; Joerg Schaepperle; Torsten WILDSCHEK; Yong Liu
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2022-03-10
Filing date: 2022-03-10
Publication date: 2023-09-14

Abstract

Embodiments of the present disclosure relate to device, method, apparatus and computer readable storage media of sidelink ranging and positioning. The method comprises: transmitting, at a first terminal device and to a second terminal device, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first terminal device; receiving, from the second terminal device, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second terminal device and a frequency offset due to a relative movement between the first terminal device and the second terminal device; determining a first frequency offset between the first transmitted frequency and the second received frequency; and causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device.

Description

SIDELINK RANGING AND POSITIONING

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular to devices, methods, apparatuses and computer readable storage media of sidelink ranging and positioning.

BACKGROUND

Sidelink ranging and/or positioning has been identified as important approach for determining a distance and/or direction of a UE, especially when the Global Navigation Satellite System (GNSS) coverage is not available. Specifically, UEs need to transmit and/or receive over the sidelink radio interface reference signals for positioning, which are also referred to as sidelink positioning reference signals (SL-PRS) . The UEs then conduct measurements, such as time of arrival (ToA) , time difference of arrival (TDoA) , round trip time (RTT) , angle of arrival (AoA) , etc., on these reference signals. Based on the measurements, the UEs estimate their positions, including relative and/or absolute positions.

Compared to existing positioning methods, sidelink ranging and/or positioning has the advantage of operating outside (partially or fully) of cellular coverage, in addition to in-coverage conditions, where network-based positioning is not applicable, or when UEs are beyond the reach of GNSS coverage. Accordingly, sidelink ranging and/or positioning is expected to be standardized in 3GPP Rel-18, and is designed to be an enabler of many use cases, most prominently public safety and V2X, and various vehicular applications including traffic efficiency, coordinated driving, and autonomous driving. Hence, there is a need to improve sidelink ranging and/or positioning techniques in terms of high accuracy and low latency requirements for sidelink or V2X applications.

SUMMARY

Example embodiments of the present disclosure provide a solution of sidelink ranging and positioning.

In a first aspect, there is provided a first terminal device. The first terminal 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 first terminal device at least to: transmit, to a second terminal device, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first terminal device; receive, from the second terminal device, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second terminal device and a frequency offset due to a relative movement between the first terminal device and the second terminal device; determine a first frequency offset between the first transmitted frequency and the second received frequency; and cause a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device.

In a second aspect, there is provided a network device. The network 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 network device at least to: obtain a first frequency offset between a first transmitted frequency for a first reference signal at a first terminal device and a second received frequency for a second reference signal at the first terminal device, the first reference signal being transmitted from the first terminal device to the second terminal device, and the second reference signal being transmitted from the second terminal device to the first terminal device; obtain a second frequency offset between a first received frequency for the first reference signal at a second terminal device and a second transmitted frequency for the second reference signal at the second terminal device; and determine a parameter associated with a relative movement between the first terminal device and the second terminal device based on the first and second frequency offsets.

In a third aspect, there is provided a method. The method comprises: transmitting, at a first terminal device and to a second terminal device, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first terminal device; receiving, from the second terminal device, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second terminal device and a frequency offset due to a relative movement between the first terminal device and the second terminal device; determining a first frequency offset between the first transmitted frequency and the second received frequency; and causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device.

In a fourth aspect, there is provided a method. The method comprises: obtaining, at a network device, a first frequency offset between a first transmitted frequency for a first reference signal at a first terminal device and a second received frequency for a second reference signal at the first terminal device, the first reference signal being transmitted from the first terminal device to the second terminal device, and the second reference signal being transmitted from the second terminal device to the first terminal device; obtaining a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device; and determining a parameter associated with a relative movement between the first terminal device and the second terminal device based on the first and second frequency offsets.

In a fifth aspect, there is provided a first apparatus, comprising: means for transmitting, to a second apparatus, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first apparatus; means for receiving, from the second apparatus, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second apparatus and a frequency offset due to a relative movement between the first apparatus and the second apparatus; means for determining a first frequency offset between the first transmitted frequency and the second received frequency; and means for causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus.

In a sixth aspect, there is provided a third apparatus, comprising: means for obtaining a first frequency offset between a first transmitted frequency for a first reference signal at a first apparatus and a second received frequency for a second reference signal at the first apparatus, the first reference signal being transmitted from the first apparatus to the second apparatus, and the second reference signal being transmitted from the second apparatus to the first apparatus; means for obtaining a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus; and means for determining a parameter associated with a relative movement between the first apparatus and the second apparatus based on the first and second frequency offsets.

In a seventh aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the third aspect.

In an eighth aspect, there is provided a computer readable medium having a computer program stored thereon which, when executed by at least one processor of a device, causes the device to carry out the method according to the fourth aspect.

Other features and advantages of the embodiments of the present disclosure will also be apparent from the following description of specific embodiments when read in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of embodiments of the disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the disclosure are presented in the sense of examples and their advantages are explained in greater detail below, with reference to the accompanying drawings, where

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

FIG. 2 shows a signaling chart illustrating a process for sidelink ranging and positioning according to some example embodiments of the present disclosure;

FIG. 3 illustrates a flowchart of an example method for sidelink ranging and positioning according to some example embodiments of the present disclosure;

FIG. 4 illustrates a flowchart of an example method for sidelink ranging and positioning according to some example embodiments of the present disclosure;

FIG. 5 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

FIG. 6 shows a block diagram of an example computer readable medium in accordance with some 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 example 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 functionalities of various elements. 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 fifth generation (5G) systems, 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) , Wi-Fi 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 5G new radio (NR) communication protocols, the future six generation (6G) 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 Next Generation NodeB (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. A RAN split architecture comprises a gNB-CU (Centralized unit, hosting RRC, SDAP and PDCP) controlling a plurality of gNB-DUs (Distributed unit, hosting RLC, MAC and PHY) . A relay node may correspond to DU part of the IAB node.

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 (IoT) 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. The terminal device may also correspond to Mobile Termination (MT) part of the integrated access and backhaul (IAB) node (a.k.a. a relay node) . In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

Although functionalities described herein can be performed, in various example embodiments, in a fixed and/or a wireless network node, in other example embodiments, functionalities may be implemented in a user equipment apparatus (such as a cell phone or tablet computer or laptop computer or desktop computer or mobile IoT device or fixed IoT device) . This user equipment apparatus can, for example, be furnished with corresponding capabilities as described in connection with the fixed and/or the wireless network node (s) , as appropriate. The user equipment apparatus may be the user equipment and/or or a control device, such as a chipset or processor, configured to control the user equipment when installed therein. Examples of such functionalities include the bootstrapping server function and/or the home subscriber server, which may be implemented in the user equipment apparatus by providing the user equipment apparatus with software configured to cause the user equipment apparatus to perform from the point of view of these functions/nodes.

Sidelink ranging/positioning in Rel-18 aims to enable tracking of objects and devices based on energy efficient ranging. Objects and devices that include coin battery powered devices can be easily found and tracked by deriving relative position information and/or direction from ranging measurements, also in out-of-coverage or partial coverage situations. Hence, this is very useful for tracking a victim or first responder during an emergency event. By further linking the ranging information with a known location of a device (e.g., a UE or drone that is located using the existing solution, e.g., eLCS or secure user plane location (SUPL) , within the network coverage) , an accurate position estimation can be achieved, making it much easier to find the respective object or device.

The key requirements for sidelink/V2X applications are low latency and high accuracy. For example, a UE (e.g., UE1) moving with at high speed should update its ranging/positioning information frequently, such that the emergency can be identified in time and collision avoidance/warning based on distance can be realized. In addition to the current distance to another UE (e.g., UE2) , another quantity that is particularly important for collision avoidance is the rate at which the distance changes (e.g., a relative longitudinal speed) . There are two basic approaches over sidelink for estimating the relative speed:

· Take at least two consecutive distance measurements and determine the relative speed as the rate with which the distance changes over time;

· Make use of the Doppler effect, which allows determining the relative speed from a single measurement of the frequency offset caused by Doppler shift. This approach is commonly used with RADAR.

· In case of network based and UE assisted positioning within the network coverage, the network computes periodically the locations of target UEs and estimate the distance and the relative speed based on the rate the distance is changing over a time offset.

If both of the UEs involved in the sidelink ranging/positioning procedure, for example, the UE1 and UE2, are operated for transmission and reception at the exact same carrier frequency, then the Doppler shift due to the relative movement between these two UEs could be directly determined from the frequency offset between a UE’s own frequency and the frequency of a signal received from the other UE.

In reality, however, frequency synchronization is not ideal and the UEs are affected by frequency error. The relevant requirement is specified by RAN4, in TS 38.101-1 clause 6.4E. 1.1, as below:

· The UE modulated carrier frequency for NR V2X sidelink transmissions shall be accurate to within ±0.1 PPM observed over a period of 1 ms compared to the absolute frequency in case of using GNSS synchronization source.

The Doppler shift due to the relative speed between the UEs can be determined as follows.

f _Doppler=f ₀ v/c (1)

where f ₀ is the nominal carrier frequency, v is the relative speed, c is the speed of light. Accordingly, a frequency error of 0.1 ppm corresponds to a relative speed of v = 0.1×10 ^-6×c ≈30 m/s=108 km/h.

In consequence, estimation of the relative speed from a single UE’s Doppler measurement is to be rather inaccurate. By way of example, with the nominal sidelink carrier frequency f ₀, UE1’s carrier frequency, denoted by f ₁, may be determined as follows:

f ₁=f ₀+Δf ₁ (2)

where Δf ₁ is UE1’s frequency error with abs (Δf ₁) ≤0.1×10 ^-6 f ₀.

UE2’s carrier frequency, denoted by f ₂, may be determined as follows:

f ₂=f ₀+Δf ₂ (3)

where Δf ₂ is UE2’s frequency error with abs (Δf ₂) ≤0.1×10 ^-6 f ₀.

The two UEs’ actual frequencies can be offset with respect to each other by up to 0.2 ppm, i.e., abs (Δf ₁-Δf ₂) ≤0.2× 10 ^-6 f ₀, which corresponds to a relative speed of about 216 km/h.

In the above example, UE1’s measurement of frequency offset of a SL-PRS transmitted by UE2 can be determined as follows:

Δf _1, 2=Δf ₁-Δf ₂+f _Doppler (4)

where f _Doppler is the actual Doppler shift due to a relative movement between UE1 and UE2, Δf ₁-Δf ₂ is the frequency offset between the two UEs due to the UEs’ frequency errors. The value of Δf ₁-Δf ₂ is a priori unknown to the UEs and its absolute value can be much larger than the Doppler shift f _Doppler.

In case of network based and UE assisted ranging, the signaling complexity is high with long latency. Moreover, this approach causes discontinuity to the relative speed estimates, when for example the platooning vehicles are performing handover to a new target cell at different times.

In order to solve the above and other potential problems, embodiments of the present disclosure provide an improved sidelink ranging and positioning scheme. According to the improved scheme, UEs involved in the sidelink ranging/positioning procedure are able to operate at the exact same carrier frequency. As a result, the Doppler shift due to the relative movement between these UEs can be directly determined from the frequency offset between a UE’s own frequency and the frequency of the reference signal received from the other UE.

Furthermore, the proposed scheme extends the ranging procedure related to distance and direction to provide additional information between the initiating UE and other UEs, including at least one of Doppler offset, the relative speed, the frequency offset due to frequency error and so on. In this way, the sidelink ranging/positioning procedure between UEs can compensate the frequency error due to Doppler offset.

FIG. 1 illustrates an example network environment in which example embodiments of the present disclosure can be implemented. The network system 100, which may be a part of a communication network, includes a first terminal device 110, a second terminal device 120 (hereinafter which may be also referred to as

UEs

110 and 120, respectively) , and a network device 130 (hereinafter which may be also referred to as a base station or gNB 130) .

As shown in FIG. 1, the network 130 serves the first terminal device 110 and the second terminal device 120, and may communicate with them via respective wireless communication channels. The network device 130 may receive and transmit control and/or data transmissions with the

terminal devices

110 and 120. In some cases, the network device 130 may also allocate resources or schedule transmissions of the first terminal device 110 and the second terminal device 120.

The first terminal device 110 and the second terminal device 120 may communication with each other via a sidelink channel. The sidelink transmissions between the first and second

terminal devices

110 and 120 may be performed based on either sidelink mode 1 or mode 2. In sidelink mode 1, the sidelink transmissions are scheduled by the network device 130. In sidelink mode 2, a resource pool is preconfigured by the network device 130, and the first terminal device 110 and the second terminal device 120 autonomously select resources from the resource pool for the sidelink transmissions.

The first terminal device 110 and the second terminal device 120 may perform the sidelink ranging/positioning procedure, within or beyond the reach of GNSS coverage. One of the first terminal device 110 and the second terminal device 120 that initiates a sidelink ranging/positioning procedure is referred to as the initiating UE or the target UE, while the other one is referred to as the responding UE or the support UE. In other words, in the example shown in FIG. 1, either of the first and second

terminal devices

110 and 120 can initiate the sidelink ranging and positioning procedure. In some cases, the initiating UE may initiate sidelink ranging/positioning with multiple responding UEs.

The sidelink ranging/positioning procedure may be triggered for various purposes. For example, the triggers for initiating the sidelink ranging/positioning include the following:

· During a lane change/lane merging maneuver on a busy motorway, safe execution of the maneuver requires that the gap between adjacent vehicles on a lane be sufficiently large (ensured by distance measurement) and the speed difference between the involved vehicles should be sufficiently small. Before actually executing the maneuver, the vehicle can trigger the sidelink ranging/positioning procedure to verify whether these conditions are met.

· Collision prediction between vehicles on a road, AGVs (automatic guided vehicles) in a factory or UAVs (e.g., drones) in the air can benefit from obtaining fast and efficient estimates of distance, direction and relative speed.

· When traveling in a formation, e.g., heavy goods vehicles in a platoon on the motorway or AGVs cooperatively transporting a large work piece in a factory, it is important to ensure that both distance and relative speed between the involved vehicles are tightly controlled.

Reference signals (RSs) may be communicated among multiple terminal devices (e.g., the first and second terminal devices 110 and 120) for sidelink ranging/positioning. In the context of the example embodiments, the reference signals may be SL-PRS or any other RS that is suitable for sidelink positioning/ranging. SL-PRS is mentioned for illustrative purpose only.

Additionally, the initiating UE may provide information about the sidelink ranging/positioning to the responding UE, including but not limited to, resources for RS, measurements of RS (e.g., time and/or angle measurements) , an indication of whether the sidelink ranging/positioning is one-shot, i.e., a single exchange of SL-PRS, or to be repeated periodically.

It is to be understood that the numbers of terminal devices and network device are given for the purpose of illustration without suggesting any limitations to the present disclosure. The network system 100 may include any suitable number of devices and/or object adapted for implementing implementations of the present disclosure. Although not shown, it would be appreciated that one or more additional devices may be located in the network system 100.

It should be also understood that, although illustrated as mobile terminals, the first terminal device 110 and the second terminal device 120 may be other devices than mobile terminals, for example, vehicles, unmanned aerial vehicles and so on. Moreover, although illustrated as a base station, the network device 120 may be a device other than a base station or a part of a base station.

Depending on the communication technologies, the network system 100 may be a Code Division Multiple Access (CDMA) network, a Time Division Multiple Address (TDMA) network, a Frequency Division Multiple Access (FDMA) network, an Orthogonal Frequency-Division Multiple Access (OFDMA) network, a Single Carrier-Frequency Division Multiple Access (SC-FDMA) network or any other. Communications discussed in the network 100 may conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, 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 fifth generation (5G) , the sixth generation (6G) or any future generation communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies.

Principle and implementations of the present disclosure will be described in detail below with reference to FIGs. 2 to 4. FIG. 2 shows a signaling chart illustrating a process 200 for sidelink ranging and positioning according to some example embodiments of the present disclosure. For the purpose of discussion, the process 200 will be described with reference to FIG. 1. The process 200 may involve the first terminal device 110, the second terminal device 120 and the network device 130.

For the purpose of describing the process 200, the SL-PRS transmitted from the first terminal device 110 to the second terminal device 120 is referred to as the first reference signal or SL-PRS1, and the SL-PRS transmitted from the second terminal device 120 to the first terminal device 110 is referred to as the second reference signal or SL-PRS2.

At the beginning of the process 200, information about the sidelink ranging and positioning procedure is provided by the initiating UE to the responding UE. As shown in FIG. 2, the first terminal device 110 may transmit 205 to the second terminal device 120 a first message including the information about the sidelink ranging and positioning procedure. However, it should be understood that the operations in the process 200 are also applicable to the case where the information about the sidelink ranging and positioning procedure is provided by the second terminal device 120 to the first terminal device 110. The present disclosure is not limited in this regard.

By transmitting the first message, the first terminal device 110 may request the peer UEs, e.g., the second terminal device 120 to measure the SL-PRSs. In other words, the first message may be a trigger for the second terminal device 120 to determine a measurement of the SL-PRS. Additionally, the first message may trigger the second terminal device 120 to include the measurement in a second message, which is the response to the first message.

By way of example, the measurement may be a measurement of the frequency offset between the carrier frequency of the first reference signal and the carrier frequency of the second terminal device 120. Such a request may be indicated, for example, by a flag “reqDeltaF” in the first message.

In some example embodiments, the first message may contain at least one of the following information:

· Resources to be used for transmission of SL-PRS including the SL-PRS1 and SL-PRS2.

· The measurements that the second terminal device 120 is requested to include in the second message. Such measurements may include time and angle measurements for general ranging/positioning, for example, the measurement of the frequency offset associated with the SL-PRSs, which will be described in details below.

· An indication of whether the ranging and positioning procedure is one-shot, e.g., SL-PRS1 and SL-PRS2 are transmitted only once, or to be repeated periodically.

After transmitting the first message, the first terminal device 110 transmits 210 to the second terminal device 120 the first reference signal at a first transmitted frequency f ₁. The first transmitted frequency f ₁ is dependent on a carrier frequency f ₀ and a first frequency error Δf ₁ associated with the first terminal device 110, for example, as determined based on the above formula (2) . The first frequency error Δf ₁ affects the first terminal device 110 for frequency synchronization. Similarly, there is a frequency error Δf ₂ that affects the second terminal device 120 for frequency synchronization, which will be discussed later.

Upon receipt of the first reference signal, the second terminal device 120 measures 215 the first reference signal. The first reference signal may be received at a first received frequency, denoted by f ₁-f _Doppler=f ₀+Δf ₁-f _Doppler.

In addition to measuring the arrival time and/or angle of the first reference signal, the second terminal device 120 measures a frequency offset between the first received frequency for SL-PRS1 and a second transmitted frequency f ₂ for SL-PRS2, which is referred to as a second frequency offset, denoted by Δf _2, 1.

In some example embodiments, the second frequency offset Δf _2, 1 may be determined as below.

Δf _2, 1=Δf ₂-Δf ₁+f _Doppler (5)

where f _Doppler is the Doppler shift due to a relative movement between the first terminal device 110 and the second terminal device 120, Δf ₂-Δf ₁ is the frequency offset between the two terminal devices due to the devices’ frequency errors.

The second terminal device 120 transmits 220 to the first terminal device 110 the second reference signal at the second transmitted frequency f ₂. The second transmitted frequency f ₂ is dependent on the carrier frequency f ₀, the second frequency error Δf ₂ associated with the second terminal device 120, for example, as determined based on the above formula (3) .

Upon receipt of the second reference signal, the first terminal device 110 measures 225 the second reference signal. The second reference signal may be received at a second received frequency, denoted by f ₂-f _Doppler=f ₀+Δf ₂-f _Doppler.

In addition to measuring the arrival time and/or angle of the second reference signal, the first terminal device 110 measures a frequency offset between the first transmitted frequency for SL-PRS1 and the second received frequency for SL-PRS2, which is referred to as a first frequency offset, denoted by Δf _1, 2. In some example embodiments, the first frequency offset Δf _1, 2 may be determined based on the above formula (4) .

Based on the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1, a parameter associated with the relative movement between the first terminal device 110 and the second terminal device 120 can be determined. The parameter associated with the relative movement may be, for example, the Doppler offset f _Doppler, a relative speed, a frequency offset f _err due to frequency error (e.g., the first frequency error and the second frequency error) , etc., which will be discussed in details as below.

In some example embodiments, the Doppler offset f _Doppler may be determined as follows:

In some example embodiments, the relative speed may be derived from the determined Doppler offset f _Doppler, i.e., f _Doppler ×c.

In some example embodiments, the frequency offset f _err due to frequency error may be determined as follows:

According to the example embodiments, the determination of the parameter can be implemented either at terminal devices or at the network device. In the implementation 1, the first terminal device 110 acts as the initiating UE, while the second terminal device 120 acts as the responding UE. In particular, the second terminal device 120 may transmit 230 to the first terminal device 110 a second message including the second frequency offset Δf _2, 1. Upon receipt of the second message, the first terminal device 110 may determine 235 the parameter associated with the relative movement based on the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1.

In some example embodiments, in addition to reporting time and angle measurements, the first terminal device 110 may further report the first frequency offset Δf _1, 2 to the second terminal device 120. In this case, the second terminal device 120 may obtain or calculate the Doppler offset f _Doppler, the relative speed, the frequency offset f _err due to frequency error, etc.

Alternatively, the first terminal device 110 may report 240 one or more of the derived quantities, such as, the Doppler offset f _Doppler, the relative speed, the frequency offset f _err due to frequency error, etc. to the second terminal device 120. Additionally, or alternatively, the first terminal device 110 may further report 245 one or more of the derived quantities to the network device 130.

Considering that the involved UEs’ frequency errors would not be changed significantly, the reporting of measurements of the frequency offset can be skipped for future ranging operations involving the same pair of UEs. That is, frequency offset reports may be sent less frequently than the SL-PRS for Doppler measurements are exchanged. Hence, both of the first terminal device 110 and the second terminal device 120 can perform Doppler measurements just using the SL-PRSs and correct for the frequency error by using the previously estimated f _err.

In the implementation 2, the second terminal device 120 acts as the initiating UE, while the first terminal device 110 acts as the responding UE, and thus the first message is provided from the second terminal device 120 to the first terminal device 110. In particular, after determining the first frequency offset Δf _1, 2, the first terminal device 110 may transmit 250 to the second terminal device 120 a third message including the first frequency offset Δf _1, 2. Upon receipt of the third message, the second terminal device 120 may determine 255 the parameter associated with the relative movement based on the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1. As previously described, one or more quantities may be derived from the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1, including but not limited to, the Doppler offset f _Doppler, the relative speed, the frequency offset f _err due to frequency error, etc.

In some example embodiments, the second terminal device 120 may further report 260 one or more of the derived quantities, such as, the Doppler offset f _Doppler, the relative speed, the frequency offset f _err due to frequency error, etc. to the first terminal device 110. Additionally, or alternatively, the second terminal device 120 may further report one or more of the derived quantities to the network device 130.

In the implementation 3, the first terminal device 110 acts as the initiating UE, while the second terminal device 120 acts as the responding UE, and the parameter associated with the relative movement is determined by the network device 130. In particular, after the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1 are obtained, the first terminal device 110 may transmit 265 the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1 to the network device 130.

The network device 130 may then determine 270 the parameter associated with the relative movement based on the first frequency offset Δf _1, 2 and the second frequency offset Δf _2, 1. After determining the parameter, the network device 130 may transmit 275 a message including the parameter to the first terminal device 110. In some example embodiments, the network device 130 may further transmit 280 the message including the parameter to the second terminal device 120. Alternatively, the second terminal device 120 may obtain the parameter from the first terminal device 110.

In some example embodiments, the initiating UE performs resource selection for transmission of SL-PRS only for itself. In this case, the first message transmitted in 205 may contain information on the resource to be used for transmission of only SL-PRS1. Accordingly, the transmission of the second message in 230 can be carried out before the transmission of the SL-PRS2 in 220. In particular, the second terminal device 120 may first report the measurement of the second frequency offset of SL-PRS1 and also indicate the resource to be used for transmission of SL-PRS2 in the second message. Next, the second terminal device 120 may transmit the SL-PRS2.

In some example embodiments, the responding UE transmits the reference signal with the same frequency as it receives the reference signal from the initiating UE. By way of example, at 220, the second terminal device 120 may transmit the SL-PRS2 with the same frequency as the SL-PRS1 received from the first terminal device 110, i.e., f ₂=f ₁-f _Doppler. Then, at 225, the first terminal device 110 may measure the first frequency offset between the first transmitted frequency f ₁ for SL-PRS1 and the second received frequency for SL-PRS2, i.e., f ₁-2f _Doppler. As a result, the difference that indicates the first frequency offset is 2f _Doppler, and the Doppler offset f _Doppler can be calculated in 235 by dividing the difference 2f _Doppler by two. In these embodiments, the reporting of the second frequency offset Δf _2, 1 in the second message in 230 is no longer necessary for the process 200. In this case, the request in the first message may indicate the frequency correction in SL-PRS2.

In some example embodiments, once the first terminal device 110 has calculated the frequency offset due to frequency error f _err, the first terminal device 110 may report f _err to the second terminal device 120 so that the second terminal device 120 can calculate the Doppler frequency as f _Doppler=Δf _2, 1+f _err. By doing this, the reporting of the first frequency offset Δf _1, 2 is not necessary for the process 200.

It should be understood that each of the

terminal devices

110 and 120 can act as both the initiating UE and the responding UE. The entire or only a part of the process 200 can be implemented for more than one time as desired. Therefore, the present disclosure is not limited in these regards.

Furthermore, the first terminal device 110 and the second terminal device 120 can perform at least one of ranging and positioning based on the PRS transmissions. The ranging and positioning may be based on TDoA, RTT and any other techniques that are either currently known or to be developed in the future. This present disclosure is not limited in this regard.

According to the example embodiments of the present disclosure, improvements on sidelink ranging and positioning are provided. The proposed solution is applicable to any application that relates to ranging and/or positioning between two or more UEs, for example, a V2X vehicle wants to know the relative position of all the nearby vehicles and needs to compensate the frequency offset. The UEs involved in the sidelink ranging procedure operate at the exact same carrier frequency, then the Doppler shift due to the relative movement between these UEs can be directly determined from the frequency offset between a UE’s own frequency and the frequency of the signal received from another UE. By exchanging frequency offset estimates, a compensation for the frequency error due to Doppler offset can be realized in the sidelink positioning and/or ranging procedure.

Although the principle of the present disclosure is described herein with the positioning/ranging techniques, it is applicable to other sidelink or V2X applications as well, in particular to those which are time-sensitive, require a low latency, a high estimation or measurement accuracy and so on.

Corresponding to the process described in connection with FIG. 2, embodiments of the present disclosure provide a solution of sidelink ranging and positioning implemented at the UEs and/or the gNB. These methods will be described below with reference to FIGs. 3 and 4.

FIG. 3 illustrates a flowchart of an example method 300 of sidelink ranging and positioning according to some example embodiments of the present disclosure. The method 300 can be implemented at a terminal device, for example, the first terminal device 110 as shown in FIG. 1. For the purpose of discussion, the method 300 will be described with reference to FIG. 1.

At 310, the first terminal device 110 transmits a first reference signal to the second terminal device 120 at a first transmitted frequency. The first transmitted frequency may be dependent on a carrier frequency and a first frequency error associated with the first terminal device 110.

In some example embodiments, prior to transmitting the first reference signal, the first terminal device 110 may transmit a first message to the second terminal device 120, and the first message at least includes a trigger for determining the second frequency offset.

In some example embodiments, the first message may further indicate a resource for the first reference signal.

In some example embodiments, the first message may further indicate at least one of a resource for the second reference signal and an indication of whether the transmissions of the first and second reference signals is one-shot or to be periodically repeated.

At 320, the first terminal device 110 receives a second reference signal from the second terminal device 120 at a second received frequency. The second received frequency may be dependent on the carrier frequency, a second frequency error associated with the second terminal device 120 and a frequency offset due to a relative movement between the first terminal device 110 and the second terminal device 120.

At 330, the first terminal device 110 determines a first frequency offset between the first transmitted frequency and the second received frequency.

At 340, the first terminal device 110 causes a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device 120 and a second transmitted frequency for the second reference signal at the second terminal device 120.

In some example embodiments, the first received frequency may be dependent on the carrier frequency, the first frequency error and the frequency offset due to the relative movement, and the second transmitted frequency may be dependent on the carrier frequency and the second frequency error.

In some example embodiments, the parameter associated with the relative movement may be determined based on the first frequency offset and the second frequency offset by removing the first frequency error and the second frequency error.

In some example embodiments, the first terminal device 110 may receive a second message from the second terminal device 120, and the second message may include the second frequency offset. The first terminal device 110 may then determine the parameter associated with the relative movement based on the first frequency offset and the second frequency offset. The second message may be received before the second reference signal. Alternatively, the second message may be received after the second reference signal.

In some example embodiments, the first terminal device 110 may report the parameter associated with the relative movement to the second terminal device 120 or a network device, e.g., the network device 130.

In some example embodiments, the first terminal device 110 may receive a second message from the second terminal device 120, and the second message may include the second frequency offset. The first terminal device 110 may then transmit the first frequency offset and the second frequency offset to a network device for determining the parameter associated with the relative movement.

In the above embodiments, the second message may be received before the second reference signal. Alternatively, the second message may be received after the second reference signal.

In some example embodiments, the first terminal device 110 may receive a first message from the second terminal device 120, and the first message may at least include a trigger for determining the first frequency offset. The first terminal device 110 may transmit a third message to the second terminal device 120, and the third message may include the first frequency offset for determining the parameter associated with the relative movement.

In some example embodiments, the parameter associated with the relative movement may be determined by the second terminal device 120 or a network device, e.g., the network device 130.

In some example embodiments, the first terminal device 110 may receive a third message from the second terminal device 120 that indicates the frequency offset associated with the first frequency error and the second frequency error. The first terminal device 110 may then determine a Doppler offset based on the first frequency offset and the frequency offset.

In some example embodiments, the first reference signal and the second reference signal may be positioning reference signals.

It should be understood that the entire or only a part of the method 300 can be implemented at the first terminal device 110 for more than one time.

According to the example embodiments of the present disclosure, there is provided an improved scheme of sidelink ranging and positioning. In the proposed scheme, frequency offsets due to frequency errors and Doppler shift are estimated between the initiating UE and at least one responding UE. In this way, the ranging and/or positioning procedure can be extended to provide parameters such as, Doppler offset, the relative speed and the frequency offset due to frequency error. Therefore, the compensation for the frequency error due to Doppler offset can be realized in the sidelink positioning and/or ranging procedure, and thus the strict requirements of sidelink communication in terms of estimation accuracy and latency can be satisfied.

FIG. 4 illustrates a flowchart of an example method 400 of sidelink ranging and positioning according to some example embodiments of the present disclosure. The method 400 can be implemented at a network device, for example, the network device 130 as shown in FIG. 1. For the purpose of discussion, the method 400 will be described with reference to FIG. 1.

At 410, the network device 130 obtains a first frequency offset between a first transmitted frequency for a first reference signal at a first terminal device 110 and a second received frequency for a second reference signal at the first terminal device 110. In this case, the first reference signal is transmitted from the first terminal device 110 to the second terminal device 120, and the second reference signal is transmitted from the second terminal device 120 to the first terminal device 110.

At 420, the network device 130 obtains a second frequency offset between a first received frequency for the first reference signal at the second terminal device 120 and a second transmitted frequency for the second reference signal at the second terminal device 120.

In some example embodiments, the first frequency offset may be obtained from the first terminal device 110, and the second frequency offset may be obtained from the second terminal device 120.

In some example embodiments, the first and second frequency offsets may be obtained from one of the first terminal device 110 or the second terminal device 120.

At 430, the network device 130 determines a parameter associated with a relative movement between the first terminal device 110 and the second terminal device 120 based on the first and second frequency offsets.

In some example embodiments, the network device 130 may transmit the parameter associated with the relative movement to at least one of the first terminal device 110 and the second terminal device 120.

In some example embodiments, the parameter associated with the relative movement may include at least one of a Doppler offset, a relative speed, and a frequency offset associated with the first frequency error and the second frequency error.

It should be understood that the entire or only a part of the method 400 can be implemented at the network device 130 for more than one time.

In some example embodiments, a first apparatus capable of performing the method 300 (for example, implemented at the UE or the first terminal device 110) may comprise means for performing the respective steps of the method 300. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the first apparatus comprises: means for transmitting, to a second apparatus, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first apparatus; means for receiving, from the second apparatus, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second apparatus and a frequency offset due to a relative movement between the first apparatus and the second apparatus; means for determining a first frequency offset between the first transmitted frequency and the second received frequency; and means for causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus.

In some example embodiments, the first apparatus further comprises: means for prior to transmitting the first reference signal, transmitting a first message to the second apparatus, the first message at least comprising a trigger for determining the second frequency offset.

In some example embodiments, the first message further indicates a resource for the first reference signal.

In some example embodiments, the first message further indicates at least one of a resource for the second reference signal and an indication of whether the transmissions of the first and second reference signals is one-shot or to be periodically repeated.

In some example embodiments, the first received frequency is dependent on the carrier frequency, the first frequency error and the frequency offset due to the relative movement, and the second transmitted frequency is dependent on the carrier frequency and the second frequency error.

In some example embodiments, the parameter associated with the relative movement is determined based on the first frequency offset and the second frequency offset by removing the first frequency error and the second frequency error.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, a second message comprising the second frequency offset; and means for determining the parameter associated with the relative movement based on the first frequency offset and the second frequency offset.

In some example embodiments, the first apparatus further comprises: means for reporting the parameter associated with the relative movement to the second apparatus or a third apparatus.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, a second message comprising the second frequency offset; and means for transmitting, to a third apparatus, the first frequency offset and the second frequency offset for determining the parameter associated with the relative movement.

In some example embodiments, the second message is received before the second reference signal, or the second message is received after the second reference signal.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, a first message at least comprising a trigger for determining the first frequency offset; and means for transmitting, to the second apparatus, a third message comprising the first frequency offset for determining the parameter associated with the relative movement.

In some example embodiments, the parameter associated with the relative movement is determined by the second apparatus or a third apparatus.

In some example embodiments, the parameter associated with the relative movement comprises at least one of a Doppler offset, a relative speed, and a frequency offset associated with the first frequency error and the second frequency error.

In some example embodiments, the first apparatus further comprises: means for receiving, from the second apparatus, a third message indicating the frequency offset associated with the first frequency error and the second frequency error; and means for determining a Doppler offset based on the first frequency offset and the frequency offset.

In some example embodiments, the first reference signal and the second reference signal comprise positioning reference signals.

In some example embodiments, the first apparatus may be a first terminal device, the second apparatus may be a second terminal device, and the third apparatus may be a network device.

In some example embodiments, a third apparatus capable of performing the method 400 (for example, implemented at a gNB or the network device 130) may comprise means for performing the respective steps of the method 400. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module.

In some example embodiments, the third apparatus comprises: means for obtaining a first frequency offset between a first transmitted frequency for a first reference signal at a first apparatus and a second received frequency for a second reference signal at the first apparatus, the first reference signal being transmitted from the first apparatus to the second apparatus, and the second reference signal being transmitted from the second apparatus to the first apparatus; means for obtaining a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus; and means for determining a parameter associated with a relative movement between the first apparatus and the second apparatus based on the first and second frequency offsets.

In some example embodiments, the first frequency offset is obtained from the first apparatus, and the second frequency offset is obtained from the second apparatus.

In some example embodiments, the first and second frequency offsets are obtained from one of the first apparatus or the second apparatus.

In some example embodiments, the third apparatus further comprises: means for transmitting the parameter associated with the relative movement to at least one of the first apparatus and the second apparatus.

FIG. 5 is a simplified block diagram of a device 500 that is suitable for implementing embodiments of the present disclosure. The device 500 may be provided to implement the communication device, for example the first terminal device 110, the second terminal device 120, and the network device 130 as shown in FIG. 1. As shown, the device 500 includes one or more processors 510, one or more memories 520 coupled to the processor 510, and one or more communication modules 540 coupled to the processor 510.

The communication module 540 is for bidirectional communications. The communication module 540 has at least one antenna to facilitate communication. The communication interface may represent any interface that is necessary for communication with other network elements.

The processor 510 may be of any type suitable to the local technical network and may include one or more of the following: general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 500 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.

The memory 520 may include one or more non-volatile memories and one or more volatile memories. Examples of the non-volatile memories include, but are not limited to, a Read Only Memory (ROM) 524, an electrically programmable read only memory (EPROM) , a flash memory, a hard disk, a compact disc (CD) , a digital video disk (DVD) , and other magnetic storage and/or optical storage. Examples of the volatile memories include, but are not limited to, a random access memory (RAM) 522 and other volatile memories that will not last in the power-down duration.

A computer program 530 includes computer executable instructions that are executed by the associated processor 510. The program 530 may be stored in the ROM 524. The processor 510 may perform any suitable actions and processing by loading the program 530 into the RAM 522.

The embodiments of the present disclosure may be implemented by means of the program 530 so that the device 500 may perform any process of the disclosure as discussed with reference to FIGs. 3 and 4. The embodiments of the present disclosure may also be implemented by hardware or by a combination of software and hardware.

In some embodiments, the program 530 may be tangibly contained in a computer readable medium which may be included in the device 500 (such as in the memory 520) or other storage devices that are accessible by the device 500. The device 500 may load the program 530 from the computer readable medium to the RAM 522 for execution. The computer readable medium may include any types of tangible non-volatile storage, such as ROM, EPROM, a flash memory, a hard disk, CD, DVD, and the like. FIG. 6 shows an example of the computer readable medium 600 in form of CD or DVD. The computer readable medium has the program 530 stored thereon.

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 representations, it is to be understood that the block, apparatus, system, technique or method 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 any of the

methods

300 and 400 as described above with reference to FIGs. 3 and 4. 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.

In the context of the present disclosure, the computer program codes or related data may be carried by any suitable carrier to enable the device, apparatus or processor to perform various processes and operations as described above. Examples of the carrier include a signal, computer readable medium, and the like.

The computer readable medium may be a computer readable signal medium or a computer readable storage medium. A computer 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 computer 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 languages 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 first terminal 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 first terminal device at least to:

transmit, to a second terminal device, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first terminal device;

receive, from the second terminal device, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second terminal device and a frequency offset due to a relative movement between the first terminal device and the second terminal device;

determine a first frequency offset between the first transmitted frequency and the second received frequency; and

cause a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device.
The first terminal device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

prior to transmitting the first reference signal, transmit a first message to the second terminal device, the first message at least comprising a trigger for determining the second frequency offset.
The first terminal device of Claim 2, wherein the first message further indicates a resource for the first reference signal.
The first terminal device of Claim 2, wherein the first message further indicates at least one of a resource for the second reference signal and an indication of whether the transmissions of the first and second reference signals is one-shot or to be periodically repeated.
The first terminal device of Claim 1, wherein the first received frequency is dependent on the carrier frequency, the first frequency error and the frequency offset due to the relative movement, and the second transmitted frequency is dependent on the carrier frequency and the second frequency error.
The first terminal device of Claim 5, wherein the parameter associated with the relative movement is determined based on the first frequency offset and the second frequency offset by removing the first frequency error and the second frequency error.
The first terminal device of Claim 5, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

receive, from the second terminal device, a second message comprising the second frequency offset; and

determine the parameter associated with the relative movement based on the first frequency offset and the second frequency offset.
The first terminal device of Claim 5, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

report the parameter associated with the relative movement to the second terminal device or a network device.
The first terminal device of Claim 5, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

receive, from the second terminal device, a second message comprising the second frequency offset; and

transmit, to a network device, the first frequency offset and the second frequency offset for determining the parameter associated with the relative movement.
The first terminal device of Claim 7 or 9, wherein the second message is received before the second reference signal, or the second message is received after the second reference signal.
The first terminal device of Claim 1, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

receive, from the second terminal device, a first message at least comprising a trigger for determining the first frequency offset; and

transmit, to the second terminal device, a third message comprising the first frequency offset for determining the parameter associated with the relative movement.
The first terminal device of Claim 11, wherein the parameter associated with the relative movement is determined by the second terminal device or a network device.
The first terminal device of Claim 1, wherein the parameter associated with the relative movement comprises at least one of a Doppler offset, a relative speed, and a frequency offset associated with the first frequency error and the second frequency error.
The first terminal device of Claim 13, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the first terminal device to:

receive, from the second terminal device, a third message indicating the frequency offset associated with the first frequency error and the second frequency error; and

determine a Doppler offset based on the first frequency offset and the frequency offset.
The first terminal device of Claim 1, wherein the first reference signal and the second reference signal comprise positioning reference signals.
A network 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 network device at least to:

obtain a first frequency offset between a first transmitted frequency for a first reference signal at a first terminal device and a second received frequency for a second reference signal at the first terminal device, the first reference signal being transmitted from the first terminal device to a second terminal device, and the second reference signal being transmitted from the second terminal device to the first terminal device;

obtain a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device; and

determine a parameter associated with a relative movement between the first terminal device and the second terminal device based on the first and second frequency offsets.
The network device of Claim 16, wherein the first frequency offset is obtained from the first terminal device, and the second frequency offset is obtained from the second terminal device.
The network device of Claim 16, wherein the first and second frequency offsets are obtained from one of the first terminal device or the second terminal device.
The network device of Claim 16, wherein the at least one memory and the computer program codes are configured to, with the at least one processor, further cause the network device to:

transmit the parameter associated with the relative movement to at least one of the first terminal device and the second terminal device.
The network device of Claim 16, wherein the parameter associated with the relative movement comprises at least one of a Doppler offset, a relative speed, and a frequency offset associated with the first frequency error and the second frequency error.
The network device of Claim 16, wherein the first reference signal and the second reference signal comprise positioning reference signals.
A method comprising:

transmitting, at a first terminal device and to a second terminal device, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first terminal device;

receiving, from the second terminal device, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second terminal device and a frequency offset due to a relative movement between the first terminal device and the second terminal device;

determining a first frequency offset between the first transmitted frequency and the second received frequency; and

causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device.
A method comprising:

obtaining, at a network device, a first frequency offset between a first transmitted frequency for a first reference signal at a first terminal device and a second received frequency for a second reference signal at the first terminal device, the first reference signal being transmitted from the first terminal device to a second terminal device, and the second reference signal being transmitted from the second terminal device to the first terminal device;

obtaining a second frequency offset between a first received frequency for the first reference signal at the second terminal device and a second transmitted frequency for the second reference signal at the second terminal device; and

determining a parameter associated with a relative movement between the first terminal device and the second terminal device based on the first and second frequency offsets.
A first apparatus comprising:

means for transmitting, to a second apparatus, a first reference signal at a first transmitted frequency, the first transmitted frequency being dependent on a carrier frequency and a first frequency error associated with the first apparatus;

means for receiving, from the second apparatus, a second reference signal at a second received frequency, the second received frequency being dependent on the carrier frequency, a second frequency error associated with the second apparatus and a frequency offset due to a relative movement between the first apparatus and the second apparatus;

means for determining a first frequency offset between the first transmitted frequency and the second received frequency; and

means for causing a parameter associated with the relative movement to be determined based on the first frequency offset and a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus.
A third apparatus comprising:

means for obtaining a first frequency offset between a first transmitted frequency for a first reference signal at a first apparatus and a second received frequency for a second reference signal at the first apparatus, the first reference signal being transmitted from the first apparatus to a second apparatus, and the second reference signal being transmitted from the second apparatus to the first apparatus;

means for obtaining a second frequency offset between a first received frequency for the first reference signal at the second apparatus and a second transmitted frequency for the second reference signal at the second apparatus; and

means for determining a parameter associated with a relative movement between the first apparatus and the second apparatus based on the first and second frequency offsets.
A computer readable medium comprising program instructions for causing an apparatus to perform the method of Claim 22 or 23.