WO2022077226A1

WO2022077226A1 - Discontinuous reception in sidelink communication

Info

Publication number: WO2022077226A1
Application number: PCT/CN2020/120667
Authority: WO
Inventors: Yong Liu; Dong Li
Original assignee: Nokia Shanghai Bell Co., Ltd.; Nokia Solutions And Networks Oy; Nokia Technologies Oy
Priority date: 2020-10-13
Filing date: 2020-10-13
Publication date: 2022-04-21
Also published as: CN116326181A

Abstract

Example embodiments of the present disclosure relate to methods, apparatuses and computer readable storage media for discontinuous reception. The method comprises determining, at a first apparatus, a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode. In this way, the power consumption of terminal devices can be significantly reduced, meanwhile the feasibility and flexibility of resource selection for DRX scheme can be improved.

Description

DISCONTINUOUS RECEPTION IN SIDELINK COMMUNICATION

FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication and in particular, to methods, apparatus and computer readable storage media of discontinuous reception (DRX) mechanism.

BACKGROUND

For vehicle to everything (V2X) communications in the fifth generation New Radio (NR) network, there are two modes of resource allocation. In a first mode (also referred to as NR V2X mode 1 or mode 1 hereinafter) , one terminal device (e.g., a user equipment) may perform V2X communications with the other terminal device by using resources allocated by a network device, such as a base station. In a second mode (also referred to as NR V2X mode 2 or mode 2 hereinafter) , one terminal device may perform V2X communications with the other terminal device by using resources autonomously selected in a resource pool by the one terminal device. V2X communications and device to device (D2D) communications can be performed based on sidelink communication technologies. For this end, sidelink resource pools and sidelink channels can be established for vehicles participating in such communications.

In some communication scenarios for the NR network, for example, in public safety and commercial wearable use cases, the terminal device is usually sensitive to energy consumption, and thus a power saving mechanism may be particularly desired. The DRX scheme can work as an efficient power saving mechanism. For example, in sidelink communication, instead of listening or monitoring the Physical Sidelink Control Channel (PSCCH) all the time, the terminal device wakes up periodically and performs blind decoding on PSCCH in an ON duration for monitoring the PSCCH. Since the ON duration typically includes a plurality of slots, performing blind decoding on PSCCH is not energy efficient. In this situation, the feasibility and flexibility of the resource selection for DRX scheme are also poor.

SUMMARY

In general, example embodiments of the present disclosure provide a solution of DRX scheme in sidelink communication.

In a first aspect, there is provided a first apparatus. The first apparatus comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the first apparatus at least to: determine a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and transmit, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In a second aspect, there is provided a second apparatus. The second apparatus comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the second apparatus at least to: receive, from a first apparatus and in an active mode, a first message comprising a first group of the resources for transmission of a first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In a third aspect, there is provided a third apparatus. The third apparatus comprises at least one processor; and at least one memory including computer program code; the at least one memory and the computer program code are configured to, with the at least one processor, cause the third apparatus at least to: determine a resource allocation scheme indicating candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and transmit the resource allocation scheme to the first apparatus and the second apparatus.

In a fourth aspect, there is provided a method. The method comprises: determining, at a first apparatus, a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In a fifth aspect, there is provided a method. The method comprises: receiving, at a second apparatus in an active mode and from a first apparatus, a first message indicating a first group of the resources for transmission of a first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and detecting the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In a sixth aspect, there is provided a method. The method comprises: determining, at a third apparatus, a resource allocation scheme indicating candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and transmitting the resource allocation scheme to the first apparatus and the second apparatus.

In a seventh aspect, there is provided a first apparatus. The first apparatus comprises: means for determining, at the first apparatus, a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In an eighth aspect, there is provided a second apparatus. The second apparatus comprises: means for receiving, at the second apparatus in an active mode and from a first apparatus, a first message indicating a first group of the resources for transmission of a first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for detecting the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In a ninth aspect, there is provided a third apparatus. The third apparatus comprises: means for means for determining, at the third apparatus, a resource allocation scheme indicating candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for transmitting the resource allocation scheme to the first apparatus and the second apparatus.

In a tenth 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.

In an eleventh 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 fifth aspect.

In a twelfth 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 sixth 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 shows an example environment in which example embodiments of the present disclosure can be implemented;

Fig. 2 shows an example slot format of sidelink channel between a transmitter terminal device and a receiver terminal device according to some example embodiments of the present disclosure;

Fig. 3 shows a signaling chart illustrating a process of DRX in sidelink communication according to some example embodiments of the present disclosure;

Fig. 4 shows an example configuration of DRX procedure according to some example embodiments of the present disclosure;

Fig. 5A shows another configuration of DRX procedure according to some example embodiments of the present disclosure;

Fig. 5B shows still another configuration of DRX procedure according to some example embodiments of the present disclosure;

Fig. 6 shows a flowchart of an example method for DRX procedure according to some example embodiments of the present disclosure;

Fig. 7 shows a flowchart of an example method for DRX procedure according to some example embodiments of the present disclosure;

Fig. 8 shows a flowchart of an example method for DRX procedure according to some example embodiments of the present disclosure;

Fig. 9 shows a simplified block diagram of a device that is suitable for implementing example embodiments of the present disclosure; and

Fig. 10 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) 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) new radio (NR) 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. The network device is allowed to be defined as part of a gNB such as for example in CU/DU split in which case the network device is defined to be either a gNB-CU or a gNB-DU.

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.

In order to lower the power consumption, the terminal device can operate in a DRX mode in which the terminal device periodically goes through an active state and an inactive state in DRX cycles. A DRX cycle includes an opportunity for DRX and the ON duration of DRX. During the opportunity for DRX, the terminal device operates in the inactive state and refrains from listening or monitoring the channel, such as, the PSCCH for NR sidelink. During the ON duration, the terminal device operates in the active state and monitors data transmissions from other terminal devices or network devices. The ON duration of DRX typically includes a plurality of slots in case of no suitable resource for use by the terminal device that acts as a transmitter (also referred to the transmitter terminal device hereinafter) , however, the periodic occurrences of ON durations may not be efficient in terms of power consumption.

To further reduce energy consumption, a sidelink wake-up signal similar to the WUS at Uu interface may be configured to wake up a terminal device that acts as the receiver (also referred to the receiver terminal device hereinafter) . The sidelink wake-up signal is transmitted before the ON duration for monitoring the PSCCH. As such, the receiver terminal device may periodically detect the sidelink wake-up signal with relatively low energy consumption, instead of periodically going through the active state and the inactive state in DRX cycles. If the sidelink wake-up signal is detected successfully, the receiver terminal device is aware that potential control/data transmissions may be transmitted on the PSCCH and Physical Sidelink Share Channel (PSSCH) , and then begins to monitor the corresponding sidelink channel in the following ON duration. Otherwise, if the terminal device fails to detect the sidelink wake-up signal, it may remain in the inactive state rather than monitoring the PSCCH. The resources (e.g., time/frequency/code resources) for the sidelink wake-up signal may be assigned or coordinated by the network device, for example, a gNB. Such a scheme may be particularly suitable for the mode 1 sidelink communication.

In 5G NR, the Physical Sidelink Feedback Channel (PSFCH) for sidelink communication is specified to carry the Hybrid Automatic Repeat request (HARQ) feedback over the sidelink at the physical layer. A Zadoff-Chu sequence may be transmitted in one physical resource block (PRB) repeated over two OFDM symbols on the PSFCH, the first symbol of which can be used for automatic gain control (AGC) , near the end of the sidelink resource in a slot. DRX signals may be configured to occupy the same location in a slot as PSFCH and employ a Zadoff-Chu sequence which, for example, may be same as or different from the Zadoff-Chu sequence transmitted on the PSFCH. This will reduce standardization effort and thus facilitate advocating the above scheme.

For the mode 2 sidelink communications, since most of the terminal devices may be in RRC idle state, more than one transmitter terminal devices (their corresponding receiver terminal devices are in the DRX mode) may select the same resource, which leads to collisions. Hence, an enhanced scheme is required to enable DRX procedure for sidelink communication.

The embodiments of the present disclosure propose an enhanced DRX scheme suitable for both mode 1 and mode 2 sidelink communications. In the scheme, one or more sidelink signals are defined for notifying the receiver terminal device of remaining in the discontinuous reception mode and waking up for monitoring respective channels. Furthermore, candidate resources for the sidelink signals can be preconfigured from a sidelink resource pool, for example, by the network device. Even for the mode 2 sidelink communication, the transmitter terminal device can select unoccupied resources for transmission of the sidelink signals and avoid resource collisions by sensing the usage of the candidate resources. In this way, the resource selection manner and signaling mechanism in the proposed DRX scheme can be much more flexible and feasible for both mode 1 and mode 2 sidelink communication. In addition, the proposed DRX scheme can meet the requirements and data characteristics of V2X communications, while significantly reduce the power consumption of the terminal devices.

Fig. 1 shows an example environment 100 in which example embodiments of the present disclosure can be implemented. As shown in Fig. 1, the communication network 100 comprises a first apparatus 110, a second apparatus 120, a third apparatus 130 and a fourth apparatus 140. The first apparatus 110, the second apparatus 120 and the fourth apparatus 140 may be terminal devices and the third apparatus 130 may be the network device. The third apparatus 130 may provide radio coverage for serving one or more of the first apparatus 110, the second apparatus 120 and the fourth apparatus 140, that is, a cell 102. It is also to be understood that the number of network devices, terminal devices and serving cells shown in Fig. 1 is given for the purpose of illustration without suggesting any limitations.

In the network 100, the first apparatus 110, the second apparatus 120 and the fourth apparatus 140 may communicate with each other, for example, via mode 1 or mode 2 sidelink communication. For the sake of discussion, in the context of network 100, the first apparatus 110 is described to act as a transmitter terminal device, the second apparatus 120 is described to act as a receiver terminal device, and the communication between the first apparatus 110, the second apparatus 120 and the fourth apparatus 140 is described to be mode 2 sidelink communication. It should be understood that the example embodiments are not limited to such a specific communication scenario, but could be applied to any communication scenario including the mode 1 sidelink communication and any other suitable D2D communications.

According to the example embodiments of the present disclosure, the sidelink DRX signals may be transmitted from the first apparatus 110 to the second apparatus 120 for directing the DRX operations of the receiver terminal device. The sidelink DRX signals may include a first sidelink signal for indicating the receiver terminal device to remain in the discontinuous reception mode. In a case where the second apparatus 120 is in the DRX mode and there is no data traffic to be transmitted to the second apparatus 120, the first apparatus 110 may transmit the first sidelink signal on a predetermined resource to keep the second apparatus 120 in the discontinuous reception mode. From the perspective of the second apparatus 120, if the first sidelink signal is detected successfully, the second apparatus 120 may ignore the following ON duration for monitoring the PSCCH and remain in the inactive state until the next opportunity for detection of the first sidelink signal. The first sidelink signal may also facilitate other terminal devices, for example, the fourth apparatus 140 to sense the usage of the resources for the sidelink DRX signals. After sensing, the fourth apparatus 140 that intends to initiate its own DRX procedures can select unused time/frequency/code resources to transmit the sidelink DRX signals.

In some example embodiments of the present disclosure, the sidelink DRX signals may additionally include a second sidelink signal for indicating the receiver terminal device to monitor data to be transmitted on the sidelink channel between the transmitter terminal device and the receiver terminal device. By way of example, in a case there is control/data to be transmitted on the PSCCH/PSSCH, the first apparatus 110 may transmit the second sidelink signal to the second apparatus 120. Upon receipt of the second sidelink signal, the second apparatus 120 may begin to monitor control/data transmissions on the PSCCH/PSSCH. This will be described below in details.

It should be understood that although the unicast communication between the first apparatus 110 and the second apparatus 120 is shown in Fig. 1, other communication modes are also applicable to the example embodiments of the present disclosure. By way of example, the example embodiments of the present application can involve the groupcast communication between one transmitter terminal device and a plurality of receiver terminal devices. The scope of the present disclosure is not limited to this aspect.

The third apparatus 130 may preconfigure candidate resources for transmission of sidelink DRX signals from the sidelink resource pool. Specifically, sidelink DRX signals may occupy last symbols in a slot, as illustrated in Fig. 2. As shown, a sidelink DRX signal may be in the form of a Zadoff-Chu sequence and transmitted in multiple PRBs repeated over two OFDM symbols, and the first symbol of which can be used for AGC. The time resources for sidelink DRX signals occur periodically, and the period may be set to be 50 ms which is suitable for VoIP traffic in public safety use case. Furthermore, the third apparatus 130 may (pre-) configure the ON duration for monitoring the PSCCH to occur after the resource for the sidelink DRX signals, which occupies multiple slots. Such a resource configuration for the sidelink DRX signals is flexibly frequency-division multiplexed and applicable for the existing specification regarding the transport block size (TBS) .

Depending on the communication technologies, the network 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 others. 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 of 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) 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. For clarity, certain aspects of the techniques are described below for LTE, and LTE terminology is used in much of the description below.

Principle and implementations of the present disclosure will be described in detail below with reference to Figs. 3 to 8. Fig. 3 shows a signaling chart illustrating a process 300 of DRX in sidelink communication according to some example embodiments of the present disclosure. For the purpose of discussion, the process 300 will be described with reference to Fig. 1. The process 300 may involve the first apparatus 110, the second apparatus 120, and the third apparatus 130.

As described above in connection with Figs. 1-2, in some cases, for example, the first apparatus 110 determines that there is less incoming packets for transmitting to the second apparatus 120 for a certain period of time, there is no need for the second apparatus 120 to continually monitor the sidelink channel. For the purpose of power saving, the first apparatus 110 and the second apparatus 120 may expect to operate in the DRX mode.

A resource allocation scheme is utilized for the sidelink communication between the first apparatus 110 and the second apparatus 120. The resource allocation scheme indicates at least candidate resources for transmission of the first sidelink signal. In some example embodiments, the resource allocation scheme may be determined by the third apparatus 130. In these embodiments, the third apparatus 130 may determine the candidate resources and transmit 305 the resource allocation scheme indicating the candidate resources to the first apparatus 110 and the second apparatus 120. In other example embodiments, the resource allocation scheme or alternatively the candidate resources may be preconfigured or predefined at the first apparatus 110 and the second apparatus 120. Other terminal devices assigned with the same resource pool with the first apparatus 110 and second apparatus 120, such as, the fourth apparatus 140 may also utilize the resource allocation scheme. In some example embodiments, the resource allocation scheme may further indicate a correspondence between a first group of the resources selected from the candidate resources for transmission of the first sidelink signal and a second group of the resources for transmission of the second sidelink signal. In some other embodiments, the correspondence between the first and second groups of resources may be predefined or preconfigured at the first apparatus 110 and the second apparatus 120. This aspect will be described in details with connection with Figs. 4 and 5A and 5B.

Since some of the candidate resources might already be occupied by other terminal devices, the first apparatus 110 may determine the usage of the candidate resources before indicating the second apparatus 120 to enter the DRX mode. Now referring to Fig. 3, to determine the usage of the candidate resources, the first apparatus 110 may sense on the candidate resources in a predetermined sensing window. In this manner, the first apparatus 110 may determine, from the candidate resources, at least one unused resource and determine the first group of resources for transmission of the first sidelink signal to the second apparatus 120 from the at least one unused resource.

The first apparatus 110 determines 310 the first group of resources. For example, the first apparatus 110 may determine the first group of resources from the candidate resources indicated by the resource allocation scheme. The first apparatus 110 transmits 315 a first message indicative of the first group of the resources to the second apparatus 120. The first message may cause the second apparatus 120 in the DRX mode and to detect the first sidelink signal on the first group of the resources. The first sidelink signal indicates the second apparatus 120 to keep in the DRX mode. In addition, the first sidelink signal may facilitate the sensing based resource selection performed by terminal devices. Once a first sidelink signal from other terminal device, such as the fourth apparatus 140 is sensed on a particular candidate resource, the first apparatus 110 will ignore that resource and select from the rest of the candidate resources.

It should be understood that the determination of the first group of resources by the first apparatus 110 is set forth herein as example implementations and should not be regarded as suggesting any limitations on the scope of the present disclosure. In some other example embodiments, the first group of resources may be determined by the receiver terminal device. In this case, the second apparatus 120 determines the first group of resources from the candidate resources indicated by the resource allocation scheme. After determining the first group of resources, the second apparatus 120 may inform the first apparatus 110 of the first group of resources.

In still other example embodiments, the first group of resources may be determined jointly by the transmitter and receiver terminal devices. In this case, the first apparatus 110 and the second apparatus 120 coordinate to determine the first group of resources from the candidate resources indicated by the resource allocation scheme.

Upon receipt of the first message, the second apparatus 120 in the active mode may determine the first group of resources and enter 320 the DRX mode. In some example embodiments, the first apparatus 110 may determine 325 that no data is to be transmitted on the sidelink channel. In this case, the first apparatus 110 transmits 330 the first sidelink signal on at least one of the resources in the first group to the second apparatus 120.

The second apparatus 120 detects 335 the first sidelink signal on the first group of the resources in the DRX mode. Once the first sidelink signal is successfully detected on at least one of the resources in the first group, the second apparatus 120 is aware of no data to be transmitted and remains 340 in the DRX mode until the next DRX cycle. In other words, in this case, the second apparatus 120 does not monitor the PSCCH/PSSCH and decode information transmitted on the corresponding channel during the next ON duration.

In a case where the first apparatus 110 determines 345 that there is data to be transmitted on the sidelink channel, the first apparatus 110 may indicate the second apparatus 120 to monitor the data to be transmitted on the sidelink channel. To select suitable resources from the resource pool for transmitting the data on the sidelink channel, the first apparatus 110 may sense data transmissions from other terminal devices, such as, the fourth apparatus 140. It should be understood that the sensing based resource selection is given herein as example implementation and many different resource selection mechanisms can also be applied to the example embodiments of the present disclosure. The scope of the present disclosure is not limited to this aspect.

In some example embodiments, if there is data to be transmitted on the sidelink channel, the first apparatus 110 may suspend 350 the transmission of the first sidelink signal on the first group of resources to indicate the second apparatus 120 to monitor the sidelink channel, which is discussed below in connection with Fig. 4.

Fig. 4 shows an example configuration 400 of DRX procedure according to some example embodiments of the present disclosure. As shown, the resource pool includes a plurality of frequency-time resources {t _i, f _i} for sidelink communication, denoted as boxes in various patterns, where n is a positive integer, t _i represents time resources in time domain, and f _i represents frequency resources in frequency domain. Specifically, the boxes in the grid pattern represent the candidate resources indicated by the resource allocation scheme, and the boxes in the stripe pattern represent the first group of resources selected from the candidate resources for transmission of the first sidelink signal.

According to the configuration 400 of the resource pool, the first sidelink signal is supposed to be transmitted at a certain frequency before respective ON-durations periodically, for example, at slots t’, t’+T, …t’+ (n-1) T and so on, where T represents the period for transmission of the sidelink DRX signals. Once the first sidelink signal is detected successfully on a corresponding resource in the first group, the second apparatus 120 will remain in the DRX mode and ignore the next ON-duration 401, that is, not to monitor the data transmission on the sidelink channel in the ON-duration 401. In a case where the first sidelink signal is not detected on a corresponding resource in the first group, for example, on the resource at slot t’+ (n-1) T, which indicates that there might be data to be transmitted on the sidelink channel, the second apparatus 120 will wake up and monitor the data transmission on the sidelink channel during the next ON duration 402. By way of example, the second apparatus 120 may decode the PSCCHs/PSSCHs during the ON duration 402.

The first sidelink signal as shown in Fig. 4 occupies the same number of PRBs as a subchannel that is the minimum resource unit for the PSSCH. It should be understood that such an arrangement is given as an example implementation, and other arrangements for the first sidelink signal that occupies different number of PRBs from the subchannel is also suitable for the embodiments of the present disclosure. The number of PRBs for the first sidelink signal may be configured by the third apparatus, such as, a gNB.

Alternatively, in other example embodiments, if there is data to be transmitted on the sidelink channel, the first apparatus 110 may transmit 355, to the second apparatus 120, the second sidelink signal on the second group of resources, and the second sidelink signal is configured to indicate the second apparatus 120 to monitor data to be transmitted on the sidelink channel, which will be discussed in details in connection with Figs. 5A and 5B.

In the above embodiments, the resource allocation scheme may further indicate a correspondence between the first group of resources {t ₁, f ₁, c ₁} and the second group of resources {t ₂, f ₂, c ₂} , which may be denoted as {t ₁, f ₁, c ₁} = f ( {t ₂, f ₂, c ₂} ) , where t _i represents time resources in time domain, f _i represents frequency resources in frequency domain and c _i represents code resources. In this way, the terminal devices may further obtain the correspondence from the resource allocation scheme, and determine the second group of resources from the candidate resources based on the correspondence.

Fig. 5A shows another example configuration 510 of DRX procedure according to some example embodiments of the present disclosure. As shown, the resource pool includes a plurality of frequency/time/code resources {t _i, f _i, c _i} for sidelink communications, denoted as boxes in various patterns. Similarly to the configuration 400, the boxes in the grid pattern represent the candidate resources indicated by the resource allocation scheme and the boxes in the stripe pattern represent the first group of resources {t ₁, f ₁, c ₁} selected from the candidate resources for transmission of the first sidelink signal. In addition, the boxes in the dotted pattern represent the second group of resources {t ₂, f ₂, c ₂} . According to the configuration 510, the second group of resources can be determined as follows:

{t ₂, f ₂, c ₂} = {t ₁+ (n-1) T, f ₁, c ₂ } (1)

where n is a positive integer and c ₂ ≠c ₁.

As shown in the configuration 510, the first sidelink signal and the second sidelink signal are configured to occupy the same frequency resource but different code resources. By way of example, the first sidelink signal and the second sidelink signal may employ the same Zadoff-Chu sequence but different cyclic shifts, and the cyclic shift employed by the second sidelink signal can be inferred from the cyclic shift employed by the first sidelink signal. As shown in Fig. 5A, the second apparatus 120 successfully detects the first sidelink signal on the first group of resources before the ON duration 501, the second apparatus 120 may remain in the DRX mode and ignore the ON duration 501. Subsequently, since the second apparatus 120 fails to detect the first sidelink signal and successfully detects the second sidelink signal on the second group of resources before the ON duration 502, the second apparatus 120 can know that there might be potential data to be transmitted on the sidelink channel and accordingly monitor data transmitted on the sidelink channel during the ON duration 502.

Fig. 5B shows still another example configuration 520 of DRX procedure according to some example embodiments of the present disclosure. As shown, the resource pool includes a plurality of frequency/time/code resources {t _i, f _i, c _i} for sidelink communications, denoted as boxes in various patterns. Similarly to the

configurations

400 and 510, the boxes in the grid pattern represent the candidate resources indicated by the resource allocation scheme and the boxes in the stripe pattern represent the first group of resources {t ₁, f ₁, c ₁} selected from the candidate resources for transmission of the first sidelink signal. In addition, the boxes in the dotted pattern represent the second group of resources {t ₂, f ₂, c ₂} . According to the configuration 520, the second group of resources can be determined as follows:

{t ₂, f ₂, c ₂} = {t ₁+ (n-1) T, f ₁+mF, c ₁} (2)

where n is a positive integer, c ₂=c ₁, and mF denotes a frequency offset.

As shown in the configuration 520, the first sidelink signal and the second sidelink signal occupy different frequency resources but with a fixed relationship, for example, m=3 as shown in Fig. 5B, and F denotes the number of RBs occupied by a sidelink DRX signal. As shown in Fig. 5B, the second apparatus 120 successfully detects the first sidelink signal on the first group of resources before the ON duration 503, the second apparatus 120 may remain in the DRX mode and ignore the ON duration 503. Subsequently, since the second apparatus 120 fails to detect the first sidelink signal and successfully detects the second sidelink signal on the second group of resources before the ON duration 504, the second apparatus 120 can know that there might be potential data to be transmitted on the sidelink channel and accordingly monitor data transmitted on the sidelink channel during the ON duration 504.

It is to be understood that the

configurations

510 and 520 as shown in Figs. 5A and 5B are set forth herein as example implementations and should not be regarded as suggesting any limitations on the scope of the present disclosure. Those skilled in the art would appreciate that there are many different correspondences and configurations of the first sidelink signal and the second sidelink signal based on the real need.

Still in reference to Fig. 3, based on a result of monitoring, the second apparatus 120 determines 360 that there is data transmitted on the sidelink channel, for example, denoted as the boxes in slashed pattern shown in Figs. 4, 5A and 5B. The second apparatus 120 may enter the active mode and be ready to receive further data from the first apparatus 110. In some example embodiments, the second apparatus 120 may transmit 365 a second message to the first apparatus 110 for indicating the second apparatus 120 is in the active mode. The second message includes, but is not limited to an acknowledgement (ACK) or a negative acknowledgement (NACK) for the data transmission on the Physical Sidelink Feedback Channel (PSFCH) . The resources for the data transmission on the sidelink channel during the ON duration may be selected based on a sensing based resource selection performed by the first apparatus 110.

If the second message is received from the second apparatus 120, the first apparatus 110 may transmit 370 further data on the sidelink channel to the second apparatus 120. Otherwise, if the first apparatus 110 fails to receive the second message from the second apparatus 120, the first apparatus 110 may perform 375 the retransmission of the second sidelink signal, for example, until the second message is received from the second apparatus 120. The data transmission may then be performed 380 between the first apparatus 110 and the second apparatus 120 in, for example, a continuous reception manner.

In other example embodiments, instead of reception of the second message, the first apparatus 110 may directly transmit data on the sidelink channel during the following slots.

A time offset from the slot containing the second sidelink signal to a starting slot of the following ON duration can be (pre-) configured by the third apparatus 130 or preconfigured at the first apparatus 110 and the second apparatus 120.

Alternatively, in still other example embodiments, the first apparatus 110 may rely on any suitable upper layer protocol to identify that the second apparatus 120 has received the second sidelink signal and enters the active mode.

According to the example embodiments of the present disclosure, the period of the DRX procedure, including a period of time for the first apparatus 110 to transmit the sidelink DRX signals (e.g., the first sidelink signal and/or the second sidelink signal) , may be determined based on data traffic properties and latency requirements of the sidelink communication. Compared with conventional DRX procedure, the period of the proposed DRX procedure may be negotiated between the first apparatus 110 and the second apparatus 120. In some example embodiments, the period of the DRX procedure can be the same as the period of resources for the sidelink DRX signals determined by the network device or preconfigured at the terminal devices.

In some other example embodiments, the period of the DRX procedure may be different from the period of the resources for the sidelink DRX signals. The period of the DRX procedure, for example, 100 ms can be multiples of the period of (pre-) configured resources for the sidelink DRX signals (e.g. 50 ms) . The period for transmission of the sidelink DRX signals at the first apparatus 110 and a corresponding period for detection of the sidelink DRX signals at the second apparatus 120 may follow the period of the DRX procedure (e.g. 100 ms) , that is, transmissions and receptions of the sidelink DRX signals are performed every 100 ms.

Alternatively, the period for transmission of the sidelink DRX signals at the first apparatus 110 may follow the (pre-) configured period of the resources for the sidelink DRX signals (e.g. 50 ms) . The corresponding period for detection of the sidelink DRX signals at the second apparatus 120 may also follow the period of the DRX procedure (e.g. 100 ms) . As such, the sensing for the resources occupied by sidelink DRX signals at other terminal devices, such as, the fourth apparatus 140 can be facilitated and accelerated.

According to the example embodiments of the present disclosure, there is provided a solution for the DRX procedure. By means of the sidelink DRX signals, either the first sidelink signal alone or the first and second sidelink signals together, the resource selection for the DRX procedure can be more flexible and thus the resource collisions between different terminal devices can be avoided. In this way, the power consumption of terminal devices will be significantly reduced, meanwhile the feasibility and flexibility of resource selection for DRX scheme can be improved.

Fig. 6 shows a flowchart of an example method 600 for DRX procedure according to some example embodiments of the present disclosure. The method 600 can be implemented at a terminal device, e.g., the first apparatus 110 described with reference to Fig. 1. The method 600 may further involve the second apparatus 120, the third apparatus 130 and the fourth apparatus 140. It is to be understood that the method 600 may include additional acts not shown and/or may omit some acts as shown, and the scope of the present disclosure is not limited in this regard. In addition, it will be appreciated that, although primarily presented herein as being performed serially, at least a portion of the acts of the process 600 may be performed contemporaneously or in a different order than as presented in Fig. 6.

At 610, the first apparatus 110 determines the first group of resources for transmission of the first sidelink signal to the second apparatus 120. The first sidelink signal indicates the second apparatus 120 to remain in the DRX mode.

In some example embodiments, the first apparatus 110 may determine the first group of resources from candidate resources indicated by a resource allocation scheme. In this case, the first apparatus 110 may receive the resource allocation scheme from the third apparatus 130. Alternatively, in other example embodiments, the resource allocation scheme indicating the candidate resources may be predefined or preconfigured at the first apparatus 110. Additionally, the terminal devices assigned with the same resource pool for sidelink communications may utilize the same resource allocation scheme for coordinating the resource selection and avoidance of collisions.

In some example embodiments, the first apparatus 110 may determine, from the candidate resources, at least one unused resource by sensing on the candidate resources in a sensing window. For example, the first apparatus 110 may sense the first sidelink signals transmitted by the fourth apparatus 140 on a particular candidate resource, and thereby unused candidate resources can be determined based on the sensing result. The first apparatus 110 may then determine the first group of resources from the at least one unused resource.

At 620, the first apparatus 110 transmits, to the second apparatus 120 in an active mode, the first message indicating the first group of the resources. The receipt of the first message causes the second apparatus 120 to detect the first sidelink signal on the first group of the resources in the DRX mode.

In some example embodiments, the first apparatus 110 may determine whether there is data to be transmitted on the sidelink channel between the first apparatus 110 and the second apparatus 120. If the first apparatus 110 determines that no data is to be transmitted to the second apparatus 120, the first apparatus 110 may transmit, to the second apparatus 120, the first sidelink signal on at least one of the resources in the first group.

The first sidelink signal may be periodically transmitted to the second apparatus 120. In some example embodiments, if the first apparatus 110 determines that there is data to be transmitted on the sidelink channel, the first apparatus 110 may suspend the transmission of the first sidelink signal on the first group of resources.

Alternatively, in other example embodiments, if the first apparatus 110 determines that there is data to be transmitted on the sidelink channel, the first apparatus 110 may transmit, to the second apparatus 120, the second sidelink signal on the second group of resources. The second sidelink signal is configured to indicate the second apparatus 120 to monitor data to be transmitted on the sidelink channel.

In some example embodiments, the first apparatus 110 may determine, from the candidate resources for transmission of sidelink signals and based on a correspondence between the first and the second groups of the resources, the second group of the resources. In this case, the sidelink signals include the first sidelink signal and the second sidelink signal, and the second sidelink signal indicates the second apparatus 120 to monitor data to be transmitted on a sidelink channel between the first apparatus and the second apparatus.

In some example embodiments, the first apparatus 110 may determine the second group of the resources based on the resource allocation scheme indicating the candidate resources and the correspondence. As discussed above, the resource allocation scheme may be received from the third apparatus 130, or alternatively predefined at the first apparatus 110.

Upon detection of absence of the first sidelink signal, or alternatively upon receipt of the second sidelink signal, the second apparatus 120 knows that there might be data to be transmitted on the next ON duration. In such cases, the second apparatus 120 may monitor potential control and data transmission on the PSCCH and PSSCH during the next ON duration. If the second apparatus 120 determines that data of interest is transmitted, for example, by decoding the PSCCH and PSSCH, the second apparatus 120 may transmit the second message to the first apparatus 110 for indicating that the second apparatus 120 is in the active mode and ready to receive further data from the first apparatus 110. The second message may include the ACK or the NACK for data transmission. In such embodiments, upon receipt of the second message, the first apparatus 110 may transmit, to the second apparatus 120, further data on the sidelink channel. Otherwise, if the first apparatus 110 fails to receive the second message from the second apparatus 120 for a predetermined time period, the first apparatus 110 may perform retransmission of the second sidelink signal.

Fig. 7 shows a flowchart of an example method 700 for DRX procedure according to some example embodiments of the present disclosure. The method 700 can be implemented at a terminal device, e.g., the second apparatus 120 described with reference to Fig. 1. For the purpose of discussion, the method 700 will be described with reference to Fig. 1. The method 700 may further involve the first apparatus 110, the third apparatus 130 and the fourth apparatus 140. It is to be understood that the process 700 may include additional acts not shown and/or may omit some acts as shown, and the scope of the present disclosure is not limited in this regard. In addition, it will be appreciated that, although primarily presented herein as being performed serially, at least a portion of the acts of the method 700 may be performed contemporaneously or in a different order than as presented in Fig. 7.

Initially, the second apparatus 120 may be in the active mode. At 710, receives, from the first apparatus 110, the first message indicating a first group of the resources for transmission of the first sidelink signal. The first sidelink signal is configured to indicate the second apparatus 120 to remain in the DRX mode.

Upon receipt of the first message, at 720, the second apparatus 120 detects the first sidelink signal on the first group of the resources in the DRX mode. In some example embodiments, in a case where the first sidelink signal is detected on at least one of the resources in the first group, the second apparatus 120 remains in the DRX mode. In a case where the first sidelink signal is not detected on a corresponding resource in the first group of resources, the second apparatus 120 knows that there might be data of interest to be transmitted on the sidelink channel during the next ON duration. In such cases, the second apparatus 120 monitors data transmitted on the sidelink channel for a preconfigured duration.

In some example embodiments, the resource allocation scheme is utilized for indicating candidate resources for transmission of sidelink DRX signals including the first sidelink signal and the second sidelink signal as well as a correspondence between the first group of resources and the second group of resources for transmission of the second sidelink signal. The second sidelink signal is configured to indicate the second apparatus 120 to monitor the sidelink channel. In such cases, the second apparatus 120 may receive the resource allocation scheme from the third apparatus 130. Alternatively, in other example embodiments, the resource allocation scheme may be predefined or preconfigured at the second apparatus 120.

In the above embodiments, the second apparatus 120 may determine, from the candidate resources and based on the correspondence, the second group of resources for transmission of the second sidelink signal. If the first sidelink signal is detected on at least one of the resources in the first group, the second apparatus 120 remains in the DRX mode. Otherwise, if the first sidelink signal is not detected on a corresponding resource in the first group of resources, the second apparatus 120 knows that there might be data of interest to be transmitted on the sidelink channel during the next ON duration. In such cases, the second apparatus 120 detects the second sidelink signal on the second group of the resources.

Fig. 8 shows a flowchart of an example method for DRX procedure according to some example embodiments of the present disclosure. The method 800 can be implemented at a network device, e.g., the third apparatus 130 described with reference to Fig. 1. For the purpose of discussion, the method 800 will be described with reference to Fig. 1. The method 800 may further involve the first apparatus 110 and second apparatus 120. It is to be understood that the process 800 may include additional acts not shown and/or may omit some acts as shown, and the scope of the present disclosure is not limited in this regard. In addition, it will be appreciated that, although primarily presented herein as being performed serially, at least a portion of the acts of the method 800 may be performed contemporaneously or in a different order than as presented in Fig. 8.

At 810, the third apparatus 130 determines a resource allocation scheme indicating candidate resources for transmission of a first sidelink signal from the first apparatus 110 to the second apparatus 120. In the example embodiments, the first sidelink signal is configured to indicate the second apparatus 120 to remain in the DRX mode. In some example embodiments, the third apparatus 130 may determine the correspondence between the first group of the resources and the second group of the resources for transmission of the second sidelink signal to the second apparatus 120. As discussed above, the second sidelink signal is configured to indicate the second apparatus 120 to monitor the sidelink channel between the first apparatus 110 and the second apparatus 120, such as, the PSCCH or/and the PSSCH. In such embodiments, the third apparatus 130 may determine the resource allocation scheme indicating the correspondence and the candidate resources.

At 820, the third apparatus 130 transmits the resource allocation scheme to the first apparatus 110 and the second apparatus 120.

In some example embodiments, a first apparatus capable of performing the method 600 (for example, the first apparatus 110) may comprise means for performing the respective steps of the method 600. The means may be implemented in any suitable form. For example, the means may be implemented in a circuitry or software module. The first apparatus may be implemented as or included in the first apparatus 110. In some embodiments, the means may comprise at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured to, with the at least one processor, cause performance of the first apparatus.

In some example embodiments, the first apparatus comprises means for determining a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In some example embodiments, the means for determining the first group of resources comprises means for determining the first group of resources from candidate resources for transmission of at least one sidelink signal, the at least one sidelink signal comprising the first sidelink signa. In some example embodiments, the candidate resources is indicated by a resource allocation scheme received from a third apparatus or predefined at the first apparatus.

In some example embodiments, the means for determining the first group of resources comprises: means for determining, from the candidate resources, at least one unused resource by sensing on the candidate resources in a sensing window; and means for determining, from the at least one unused resource, the first group of resources.

In some example embodiments, the first apparatus further comprises means for in accordance with a determination that no data is to be transmitted on a sidelink channel between the first apparatus and the second apparatus, transmitting, to the second apparatus, the first sidelink signal on at least one of the resources in the first group.

In some example embodiments, the first sidelink signal is periodically transmitted to the second apparatus, and the first apparatus further comprises means for in accordance with a determination that there is data to be transmitted on a sidelink channel between the first apparatus and the second apparatus, suspending the transmission of the first sidelink signal on the first group of resources.

In some example embodiments, the first apparatus further comprises: means for determine, from candidate resources for transmission of sidelink signals, a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the sidelink signals comprising the first sidelink signal and the second sidelink signal, and the second sidelink signal indicating the second apparatus to monitor data to be transmitted on a sidelink channel between the first apparatus and the second apparatus.

In some example embodiments, the means for determining the second group of the resources comprises means for determining the second group of the resources based on a resource allocation scheme indicating the candidate resources and the correspondence, the resource allocation scheme being received from a third apparatus or predefined at the first apparatus.

In some example embodiments, the first apparatus further comprises means for in accordance with a determination that there is data to be transmitted on the sidelink channel, transmitting, to the second apparatus, the second sidelink signal on the second group of resources.

In some example embodiments, the first apparatus further comprises: means for in response to receiving a second message from the second apparatus, transmitting, to the second apparatus, further data on the sidelink channel, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data; and means for in response to failing to receive the second message from the second apparatus for a predetermined time period, performing retransmission of the second sidelink signal.

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

In some example embodiments, a second apparatus capable of performing the method 700 (for example, the second apparatus 120) may comprise means for performing the respective steps of the method 700. 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 means may comprise at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured to, with the at least one processor, cause performance of the second apparatus. The second apparatus may be implemented as or included in the second apparatus 120.

In some example embodiments, the second apparatus comprises means for receiving, from a first apparatus and in an active mode, a first message indicating a first group of the resources for transmission of a first sidelink signal, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for detecting the first sidelink signal on the first group of the resources in the discontinuous reception mode.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remaining in the discontinuous reception mode; and means for in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, monitoring data transmitted on a sidelink channel between the first apparatus and the second apparatus for a preconfigured duration.

In some example embodiments, the second apparatus further comprises: means for determining a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and the second apparatus.

In some example embodiments, the means for determining the second group of the resources comprises: means for determining the second group of the resources from candidate resources for transmission of sidelink signals from the first apparatus, the sidelink signals comprising the first sidelink signal and the second sidelink signal.

In some example embodiments, the candidate resources and the correspondence are indicated by a resource allocation scheme received from a third apparatus or predefined at the second apparatus.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remaining in the discontinuous reception mode; and means for in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, detecting the second sidelink signal on the second group of the resources.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that the second sidelink signal is not detected on a corresponding resource of the second group of the resources, remaining in the discontinuous reception mode; and means for in accordance with a determination that the second sidelink signal is detected on a corresponding resource of the second group of the resources, monitoring data transmitted on a sidelink channel for a preconfigured duration.

In some example embodiments, the second apparatus further comprises: means for in accordance with a determination that there is no data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, remaining in the discontinuous reception mode; and means for in accordance with a determination that there is data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, entering the active mode.

In some example embodiments, the second apparatus further comprises means for in accordance with a determination that there is data transmitted on the sidelink channel, transmitting, to the first apparatus, a second message indicating the second apparatus is in the active mode, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data.

In some example embodiments, a third apparatus capable of performing the method 800 (for example, the third apparatus 130) may comprise means for performing the respective steps of the method 800. 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 means may comprise at least one processor and at least one memory including computer program code. The at least one memory and computer program code are configured to, with the at least one processor, cause performance of the third apparatus. The third apparatus may be implemented as or included in the third apparatus 130.

In some example embodiments, the third apparatus comprises: means for determining candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and means for transmitting, to the first apparatus and the second apparatus, a resource allocation scheme indicating the candidate resources .

In some example embodiments, the means for determining the resource allocation scheme comprises: means for determining a correspondence between the first group of the resources and a second group of the resources for transmission of a second sidelink signal to the second apparatus, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and second apparatus; and means for determining the resource allocation scheme indicating the correspondence and the candidate resources.

Fig. 9 is a simplified block diagram of a device 900 that is suitable for implementing embodiments of the present disclosure. The device 900 may be provided to implement the communication device, for example the first apparatus 110, the second apparatus 120, the third apparatus 130 and fourth apparatus 140 as shown in Fig. 1. As shown, the device 900 includes one or more processors 910, one or more memories 920 coupled to the processor 910, and one or more communication modules 940 coupled to the processor 910.

The communication module 940 is for bidirectional communications. The communication module 940 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 910 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 900 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 920 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) 924, 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) 922 and other volatile memories that will not last in the power-down duration.

A computer program 930 includes computer executable instructions that are executed by the associated processor 910. The program 930 may be stored in the ROM 920. The processor 910 may perform any suitable actions and processing by loading the program 930 into the RAM 920.

The embodiments of the present disclosure may be implemented by means of the program 930 so that the device 900 may perform any process of the disclosure as discussed with reference to Figs. 6 to 8. 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 930 may be tangibly contained in a computer readable medium which may be included in the device 900 (such as in the memory 920) or other storage devices that are accessible by the device 900. The device 900 may load the program 930 from the computer readable medium to the RAM 922 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. 10 shows an example of the computer readable medium 1000 in form of CD or DVD. The computer readable medium has the program 930 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 600 to 800 as described above with reference to Figs. 6-8. 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 apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the first apparatus at least to:

determine a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

transmit, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.
The first apparatus of Claim 1, wherein the first apparatus is caused to determine the first group of resources by:

determining the first group of resources from candidate resources for transmission of at least one sidelink signal, the at least one sidelink signal comprising the first sidelink signal.
The first apparatus of Claim 2, wherein the candidate resources is indicated by a resource allocation scheme received from a third apparatus or predefined at the first apparatus.
The first apparatus of Claim 1, wherein the first apparatus is further caused to determine the first group of resources by:

determining at least one unused resource by sensing on candidate resources in a sensing window; and

determining, from the at least one unused resource, the first group of resources.
The first apparatus of Claim 1, wherein the first apparatus is further caused to:

in accordance with a determination that no data is to be transmitted on a sidelink channel between the first apparatus and the second apparatus, transmit, to the second apparatus, the first sidelink signal on at least one of the resources in the first group.
The first apparatus of Claim 1, wherein the first sidelink signal is periodically transmitted to the second apparatus, and the first apparatus is further caused to:

in accordance with a determination that there is data to be transmitted on a sidelink channel between the first apparatus and the second apparatus, suspend the transmission of the first sidelink signal on the first group of resources.
The first apparatus of Claim 1, wherein the first apparatus is further caused to:

determine, from candidate resources for transmission of sidelink signals, a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the sidelink signals comprising the first sidelink signal and the second sidelink signal, and the second sidelink signal indicating the second apparatus to monitor data to be transmitted on a sidelink channel between the first apparatus and the second apparatus.
The first apparatus of Claim 7, wherein the first apparatus is caused to determine the second group of the resources by:

determining the second group of the resources based on a resource allocation scheme indicating the candidate resources and the correspondence, the resource allocation scheme being received from a third apparatus or predefined at the first apparatus.
The first apparatus of Claim 7, wherein the first apparatus is further caused to:

in accordance with a determination that there is data to be transmitted on the sidelink channel, transmit, to the second apparatus, the second sidelink signal on the second group of resources.
The first apparatus of Claim 9, wherein the first apparatus is further caused to:

in response to receiving a second message from the second apparatus, transmit, to the second apparatus, further data on the sidelink channel, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data; and

in response to failing to receive the second message from the second apparatus for a predetermined time period, perform retransmission of the second sidelink signal.
The first apparatus of any of Claims 1 to 10, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A second apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the second apparatus at least to:

receive, from a first apparatus and in an active mode, a first message indicating a first group of the resources for transmission of a first sidelink signal, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.
The second apparatus of Claim 12, wherein the second apparatus is further caused to:

in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remain in the discontinuous reception mode; and

in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, monitor data transmitted on a sidelink channel between the first apparatus and the second apparatus for a preconfigured duration.
The second apparatus of Claim 12, wherein the second apparatus is further caused to:

determine a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and the second apparatus.
The second apparatus of Claim 14, wherein the second apparatus is caused to determine the second group of the resources by:

determining the second group of the resources from candidate resources for transmission of sidelink signals from the first apparatus, the sidelink signals comprising the first sidelink signal and the second sidelink signal.
The second apparatus of Claim 15, wherein the candidate resources and the correspondence are indicated by a resource allocation scheme received from a third apparatus or predefined at the second apparatus.
The second apparatus of Claim 14, wherein the second apparatus is further caused to:

in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remain in the discontinuous reception mode; and

in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, detect the second sidelink signal on the second group of the resources.
The second apparatus of Claim 17, wherein the second apparatus is further caused to:

in accordance with a determination that the second sidelink signal is not detected on a corresponding resource of the second group of the resources, remain in the discontinuous reception mode; and

in accordance with a determination that the second sidelink signal is detected on a corresponding resource of the second group of the resources, monitor data transmitted on a sidelink channel for a preconfigured duration.
The second apparatus of Claim 13 or 18, wherein the second apparatus is further caused to:

in accordance with a determination that there is no data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, remain in the discontinuous reception mode; and

in accordance with a determination that there is data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, enter the active mode.
The second apparatus of Claim 18, wherein the second apparatus is further caused to:

in accordance with a determination that there is data transmitted on the sidelink channel, transmit, to the first apparatus, a second message indicating the second apparatus is in the active mode, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data.
The second apparatus of any of Claims 14 to 20, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A third apparatus, comprising:

at least one processor; and

at least one memory including computer program code;

wherein the at least one memory and the computer program code are configured to, with the at least one processor, cause the third apparatus at least to:

determine candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

transmit, to the first apparatus and the second apparatus, a resource allocation scheme indicating the candidate resources.
The third apparatus of Claim 22, wherein the third apparatus is further caused to:

determine a correspondence between the first group of the resources and a second group of the resources for transmission of a second sidelink signal to the second apparatus, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and the second apparatus; and

wherein the third apparatus is caused to transmit the resource allocation scheme by:

transmitting the resource allocation scheme indicating the correspondence and the candidate resources.
The third apparatus of Claim 22 or 23, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A method comprising:

determining, at a first apparatus, a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode;

transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.
The method of Claim 25, wherein determining the first group of resources comprises:

determining the first group of resources from candidate resources for transmission of at least one sidelink signal, the at least one sidelink signal comprising the first sidelink signal.
The method of Claim 26, wherein the candidate resources is indicated by a resource allocation scheme received from a third apparatus or predefined at the first apparatus.
The method of Claim 25, further comprising:

in accordance with a determination that no data is to be transmitted on a sidelink channel between the first apparatus and the second apparatus, transmitting, to the second apparatus, the first sidelink signal on at least one of the resources in the first group.
The method of Claim 25, wherein determining the first group of resources comprises:

determining at least one unused resource by sensing on candidate resources in a sensing window; and

determining, from the at least one unused resource, the first group of resources.
The method of Claim 25, wherein the first sidelink signal is periodically transmitted to the second apparatus, and the method further comprises:

in accordance with a determination that there is data to be transmitted on a sidelink channel between the first apparatus and the second apparatus, suspending the transmission of the first sidelink signal on the first group of resources.
The method of Claim 25, further comprising:

determine, from candidate resources for transmission of sidelink signals, a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the sidelink signals comprising the first sidelink signal and the second sidelink signal, and the second sidelink signal indicating the second apparatus to monitor data to be transmitted on a sidelink channel between the first apparatus and the second apparatus.
The method of Claim 31, wherein determining the second group of the resources comprises:

determining the second group of the resources based on a resource allocation scheme indicating the candidate resources and the correspondence, the resource allocation scheme being received from a third apparatus or predefined at the first apparatus.
The method of Claim 31, further comprising:

in accordance with a determination that there is data to be transmitted on the sidelink channel, transmitting, to the second apparatus, the second sidelink signal on the second group of resources.
The method of Claim 33, further comprising:

in response to receiving a second message from the second apparatus, transmitting, to the second apparatus, further data on the sidelink channel, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data; and

in response to failing to receive the second message from the second apparatus for a predetermined time period, performing retransmission of the second sidelink signal.
The method of any of Claims 25 to 34, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A method comprising:

receiving, at a second apparatus in an active mode and from a first apparatus, a first message indicating a first group of the resources for transmission of a first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

detecting the first sidelink signal on the first group of the resources in the discontinuous reception mode.
The method of Claim 36, further comprising:

in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remaining in the discontinuous reception mode; and

in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, monitoring data transmitted on a sidelink channel between the first apparatus and the second apparatus for a preconfigured duration.
The method of Claim 36, further comprising:

determining a second group of the resources for transmission of a second sidelink signal based on a correspondence between the first and the second groups of the resources, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and the second apparatus.
The method of Claim 38, wherein determining the second group of the resources comprises:

determining the second group of the resources from candidate resources for transmission of sidelink signals from the first apparatus, the sidelink signals comprising the first sidelink signal and the second sidelink signal.
The method of Claim 39, wherein the candidate resources and the correspondence are indicated by a resource allocation scheme received from a third apparatus or predefined at the second apparatus.
The method of Claim 38, further comprising:

in accordance with a determination that the first sidelink signal is detected on at least one of the resources in the first group, remaining in the discontinuous reception mode; and

in accordance with a determination that the first sidelink signal is not detected on a corresponding resource in the first group of resources, detecting the second sidelink signal on the second group of the resources.
The method of Claim 41, further comprising:

in accordance with a determination that the second sidelink signal is not detected on a corresponding resource of the second group of the resources, remaining in the discontinuous reception mode; and

in accordance with a determination that the second sidelink signal is detected on a corresponding resource of the second group of the resources, monitoring data transmitted on a sidelink channel for a preconfigured duration.
The method of Claim 37 or 42, further comprising:

in accordance with a determination that there is no data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, remaining in the discontinuous reception mode; and

in accordance with a determination that there is data transmitted on the sidelink channel in the preconfigured duration based on the result of monitoring, entering the active mode.
The method of Claim 43, further comprising:

in accordance with a determination that there is data transmitted on the sidelink channel, transmitting, to the first apparatus, a second message indicating the second apparatus is in the active mode, the second message comprising an acknowledgement or a negative acknowledgement for the transmission of the data.
The method of any of Claims 36 to 44, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A method comprising:

determining, at a third apparatus, candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

transmitting, to the first apparatus and the second apparatus, the resource allocation scheme indicating the candidate resources.
The method of Claim 46, wherein the method further comprises:

determining a correspondence between the first group of the resources and a second group of the resources for transmission of a second sidelink signal to the second apparatus, the second sidelink signal indicating the second apparatus to monitor a sidelink channel between the first apparatus and the second apparatus; and

wherein transmitting the resource allocation scheme comprises:

transmitting the resource allocation scheme indicating the correspondence and the candidate resources.
The method of Claim 46 or 47, wherein the first apparatus is a terminal device, the second apparatus is a further terminal device, and the third apparatus is a network device.
A first apparatus comprising:

means for determining, at the first apparatus, a first group of resources for transmission of a first sidelink signal to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode;

means for transmitting, to the second apparatus in an active mode, a first message indicating the first group of the resources, to cause the second apparatus to detect the first sidelink signal on the first group of the resources in the discontinuous reception mode.
A second apparatus comprising:

means for receiving, at the second apparatus in an active mode and from a first apparatus, a first message indicating a first group of the resources for transmission of a first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

means for detecting the first sidelink signal on the first group of the resources in the discontinuous reception mode.
A third apparatus comprising:

means for determining, at the third apparatus, candidate resources for transmission of a first sidelink signal from a first apparatus to a second apparatus, the first sidelink signal indicating the second apparatus to remain in a discontinuous reception mode; and

transmitting, to the first apparatus and the second apparatus, a resource allocation scheme indicating the candidate resources.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of Claims 25-35.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of Claims 36-45.
A non-transitory computer readable medium comprising program instructions for causing an apparatus to perform at least the method of any of Claims 46-48.