WO2021028194A1

WO2021028194A1 - Methods and apparatuses for sidelink communication

Info

Publication number: WO2021028194A1
Application number: PCT/EP2020/070939
Authority: WO
Inventors: Congchi ZHANG; Antonino ORSINO; Zhang Zhang
Original assignee: Telefonaktiebolaget Lm Ericsson (Publ)
Priority date: 2019-08-15
Filing date: 2020-07-24
Publication date: 2021-02-18

Abstract

Methods and apparatus for configuration of sidelink communication. The method by a first terminal device comprises obtaining (502) first transmission side configuration of the first terminal device. The first transmission side configuration is related to radio link control over a sidelink between the first terminal device and a second terminal device. The method further comprises transmitting (504) the first transmission side configuration of the first terminal device towards the second terminal device. According to the present disclosure, sidelink radio link control configuration may be implemented in a flexible manner so that sidelink communication performance can be improved.

Description

METHODS AND APPARATUSES FOR SIDELINK COMMUNICATION

FIELD OF THE INVENTION

[0001] The present disclosure generally relates to communication networks, and more specifically, to method and apparatus for sidelink (SL) communication.

BACKGROUND

[0002] This section introduces aspects that may facilitate a better understanding of the disclosure. Accordingly, the statements of this section are to be read in this light and are not to be understood as admissions about what is in the prior art or what is not in the prior art.

[0003] Communication service providers and network operators have been continually facing challenges to deliver value and convenience to consumers by, for example, providing compelling network services and performance. With the evolution of wireless communication, a requirement for supporting device to device (D2D) communication features which targets at both commercial and public safety applications has been proposed. Wireless communication networks such as long-term evolution (LTE) and new radio (NR) are expected to support various services over a D2D link such as a si delink (SL) between devices such as user equipments (UEs). Radio resources may be configured for traffic communications over the SL to meet different quality of service (QoS) requirements of the traffics.

SUMMARY

[0004] This summary is provided to introduce a selection of concepts in a simplified form that are further described below in the detailed description. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

[0005] In a wireless communication network such as 5G or NR network, a UE may initiate a request for SL radio bearer (SLRB) and related configuration. For bi directional traffic transmissions, two UEs may initiate two bearers in each direction. If the two UEs are served by different base stations, or one of them is out of coverage (OoC), the bearers initiated by the UEs may be configured differently. In this case, a transmission (TX) side and a reception (RX) side of an SL radio link control (RLC) entity may have different communication configuration (e.g., different RLC sequence number (SN) length, etc.). However, current NR network signaling procedures cannot support such separate configuration of the TX and RX sides of the SL RLC entity. Therefore, it may be desirable to support SL RLC configuration in an efficient way.

[0006] Various exemplary embodiments of the present disclosure propose a solution for SL communication, which can enable a UE to set up RX side configuration of an SL RLC entity separate from TX side configuration of the SL RLC entity, but dependent on TX side configuration of the peer SL RLC entity, which can improve configuration flexibility of the SL RLC entity and avoid potential SLRB configuration controversy.

[0007] According to a first aspect of the present disclosure, there is provided a method performed by a first terminal device such as a UE. The method comprises obtaining first transmission side configuration of the first terminal device. The first transmission side configuration is related to RLC over a SL between the first terminal device and a second terminal device. The method further comprises transmitting the first transmission side configuration of the first terminal device towards the second terminal device.

[0008] In accordance with some exemplary embodiments, the first terminal device may transmit the first transmission side configuration of the first terminal device to the second terminal device over the SL, or to a network node which can forward the first transmission side configuration of the first terminal device to the second terminal device.

[0009] In accordance with some exemplary embodiments, the first transmission side configuration may be obtained by the first terminal device according to at least one of:

•radio resource control (RRC) signaling from a network node;

•system information signaling from the network node; and

•pre-configuration information for the first terminal device.

[0010] In accordance with some exemplary embodiments, the obtaining of the first transmission side configuration of the first terminal device may comprise: transmitting a request for sidelink radio bearer (SLRB) configuration to a network node, and obtaining the first transmission side configuration of the first terminal device from the network node in response to the request for SLRB configuration.

[0011] In accordance with some exemplary embodiments, the method according to the first aspect of the present disclosure may further comprise: receiving second transmission side configuration of the second terminal device from at least one of the second terminal device and a network node. The second transmission side configuration may be related to RLC over the SL between the first terminal device and the second terminal device. According to an embodiment, based at least in part on the second transmission side configuration of the second terminal device, the first terminal device can determine reception side configuration of the first terminal device for the RLC over the SL.

[0012] In accordance with some exemplary embodiments, the method according to the first aspect of the present disclosure may further comprise: transmitting the reception side configuration of the first terminal device to at least one of the second terminal device and the network node.

[0013] According to a second aspect of the present disclosure, there is provided an apparatus which may be implemented as a first terminal device. The apparatus comprises one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the first aspect of the present disclosure.

[0014] According to a third aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the first aspect of the present disclosure.

[0015] According to a fourth aspect of the present disclosure, there is provided an apparatus which may be implemented as a first terminal device. The apparatus comprises an obtaining unit and a transmitting unit. In accordance with some exemplary embodiments, the obtaining unit may be operable to carry out at least the obtaining step of the method according to the first aspect of the present disclosure. The transmitting unit may be operable to carry out at least the transmitting step of the method according to the first aspect of the present disclosure.

[0016] According to a fifth aspect of the present disclosure, there is provided a method performed by a second terminal device such as a UE. The method comprises receiving first transmission side configuration of a first terminal device from at least one of the first terminal device and a network node. The first transmission side configuration is related to RLC over a SL between the first terminal device and the second terminal device. The method further comprises determining reception side configuration of the second terminal device for the RLC over the SL, based at least in part on the first transmission side configuration of the first terminal device.

[0017] In accordance with some exemplary embodiments, the method according to the fifth aspect of the present disclosure may further comprise: transmitting the reception side configuration of the second terminal device to at least one of the first terminal device and the network node.

[0018] In accordance with some exemplary embodiments, the method according to the fifth aspect of the present disclosure may further comprise: obtaining second transmission side configuration of the second terminal device. The second transmission side configuration may be related to RLC over the SL between the first terminal device and the second terminal device.

[0019] In accordance with some exemplary embodiments, the method according to the fifth aspect of the present disclosure may further comprise: transmitting the second transmission side configuration of the second terminal device towards the first terminal device.

[0020] In accordance with some exemplary embodiments, the second transmission side configuration may be obtained by the second terminal device according to at least one of: RRC signaling from the network node, system information signaling from the network node, and pre-configuration information for the second terminal device.

[0021] In accordance with some exemplary embodiments, the obtaining of the second transmission side configuration of the second terminal device may comprise: transmitting a request for SLRB configuration to the network node, and obtaining the second transmission side configuration of the second terminal device from the network node in response to the request for SLRB configuration.

[0022] In accordance with some exemplary embodiments, the request for SLRB configuration may be transmitted to the network node by the second terminal device in response to the reception of the first transmission side configuration of the first terminal device.

[0023] According to a sixth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second terminal device. The apparatus comprises one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the fifth aspect of the present disclosure.

[0024] According to a seventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the fifth aspect of the present disclosure.

[0025] According to an eighth aspect of the present disclosure, there is provided an apparatus which may be implemented as a second terminal device. The apparatus comprises a receiving unit and a determining unit. In accordance with some exemplary embodiments, the receiving unit may be operable to carry out at least the receiving step of the method according to the fifth aspect of the present disclosure. The determining unit may be operable to carry out at least the determining step of the method according to the fifth aspect of the present disclosure.

[0026] According to a ninth aspect of the present disclosure, there is provided a method performed by a first network node such as a base station. The method comprises providing first transmission side configuration to a first terminal device. The first transmission side configuration is related to RLC over a SL between the first terminal device and a second terminal device. [0027] In accordance with some exemplary embodiments, the first transmission side configuration may be provided to the first terminal device in response to a request for SLRB configuration from the first terminal device.

[0028] In accordance with some exemplary embodiments, the method according to the ninth aspect of the present disclosure may further comprise: informing the first transmission side configuration of the first terminal device to a second network node serving the second terminal device. According to an embodiment, the first network node and the second network node may be the same network node.

[0029] In accordance with some exemplary embodiments, the method according to the ninth aspect of the present disclosure may further comprise: informing the first transmission side configuration of the first terminal device to the second terminal device.

[0030] In accordance with some exemplary embodiments, the method according to the ninth aspect of the present disclosure may further comprise: obtaining, from the first terminal device, reception side configuration of the first terminal device for the RLC over the SL. The reception side configuration of the first terminal device may be based at least in part on second transmission side configuration of the second terminal device for the RLC over the SL.

[0031] In accordance with some exemplary embodiments, the method according to the ninth aspect of the present disclosure may further comprise: informing the reception side configuration of the first terminal device to the second terminal device or a second network node serving the second terminal device.

[0032] According to a tenth aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus comprises one or more processors and one or more memories storing computer program codes. The one or more memories and the computer program codes may be configured to, with the one or more processors, cause the apparatus at least to perform any step of the method according to the ninth aspect of the present disclosure.

[0033] According to an eleventh aspect of the present disclosure, there is provided a computer-readable medium having computer program codes embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to the ninth aspect of the present disclosure.

[0034] According to a twelfth aspect of the present disclosure, there is provided an apparatus which may be implemented as a first network node. The apparatus comprises a providing unit and optionally an informing unit. In accordance with some exemplary embodiments, the providing unit may be operable to carry out at least the providing step of the method according to the ninth aspect of the present disclosure. The informing unit may be operable to carry out at least the informing step of the method according to the ninth aspect of the present disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] The disclosure itself, the preferable mode of use and further objectives are best understood by reference to the following detailed description of the embodiments when read in conjunction with the accompanying drawings, in which:

[0036] Fig.1 A is a diagram illustrating an exemplary cellular-intelligent transport system (C-ITS) environment according to an embodiment of the present disclosure;

[0037] Fig. IB is a diagram illustrating an example of SF configuration according to an embodiment of the present disclosure;

[0038] Fig.2A is a diagram illustrating an example of SERB configuration exchange between two UEs according to an embodiment of the present disclosure; [0039] Fig.2B is a diagram illustrating an exemplary RLC configuration information element according to an embodiment of the present disclosure;

[0040] Fig.3 is a diagram illustrating an example of RLC SLRB according to an embodiment of the present disclosure;

[0041] Figs.4A-4B are diagrams illustrating exemplary RLC entity configuration according to some embodiments of the present disclosure;

[0042] Fig.5 is a flowchart illustrating a method according to some embodiments of the present disclosure;

[0043] Fig.6 is a flowchart illustrating another method according to some embodiments of the present disclosure;

[0044] Fig.7 is a flowchart illustrating another method according to some embodiments of the present disclosure;

[0045] Fig.8 is a block diagram illustrating an apparatus according to some embodiments of the present disclosure;

[0046] Fig.9 is a block diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure;

[0047] Fig.10 is a block diagram illustrating a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure;

[0048] Fig.11 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure;

[0049] Fig.12 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure;

[0050] Fig.13 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure; and

[0051] Fig.14 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment of the present disclosure.

DETAILED DESCRIPTION

[0052] The embodiments of the present disclosure are described in detail with reference to the accompanying drawings. It should be understood that these embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the present disclosure, rather than suggesting any limitations on the scope of the present disclosure. Reference throughout this specification to features, advantages, or similar language does not imply that all of the features and advantages that may be realized with the present disclosure should be or are in any single embodiment of the disclosure. Rather, language referring to the features and advantages is understood to mean that a specific feature, advantage, or characteristic described in connection with an embodiment is included in at least one embodiment of the present disclosure. Furthermore, the described features, advantages, and characteristics of the disclosure may be combined in any suitable manner in one or more embodiments. One skilled in the relevant art will recognize that the disclosure may be practiced without one or more of the specific features or advantages of a particular embodiment. In other instances, additional features and advantages may be recognized in certain embodiments that may not be present in all embodiments of the disclosure.

[0053] As used herein, the term “communication network” refers to a network following any suitable communication standards, such as new radio (NR), long term evolution (LTE), LTE- Advanced, wideband code division multiple access (WCDMA), high-speed packet access (HSPA), and so on. Furthermore, the communications between a terminal device and a network node 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), 4G, 4.5G, 5G communication protocols, and/or any other protocols either currently known or to be developed in the future.

[0054] The term “network node” refers to a network device in a communication network via which a terminal device accesses to the network and receives services therefrom. The network node may refer to a base station (BS), an access point (AP), a multi-cell/multicast coordination entity (MCE), a controller or any other suitable device in a wireless communication network. The BS may be, for example, a node B (NodeB or NB), an evolved NodeB (eNodeB or eNB), a next generation NodeB (gNodeB or 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.

[0055] Yet further examples of the network node comprise multi- standard radio (MSR) radio equipment such as MSR BSs, network controllers such as radio network controllers (RNCs) or base station controllers (BSCs), base transceiver stations (BTSs), transmission points, transmission nodes, positioning nodes and/or the like. More generally, however, the network node may represent any suitable device (or group of devices) capable, configured, arranged, and/or operable to enable and/or provide a terminal device access to a wireless communication network or to provide some service to a terminal device that has accessed to the wireless communication network.

[0056] The term “terminal device” refers to any end device that can access a communication network and receive services therefrom. By way of example and not limitation, the terminal device may refer to a mobile terminal, a user equipment (UE), or other suitable devices. The UE may be, for example, a subscriber station, a portable subscriber station, a mobile station (MS) or an access terminal (AT). The terminal device may include, but not limited to, portable computers, image capture terminal devices such as digital cameras, gaming terminal devices, music storage and playback appliances, a mobile phone, a cellular phone, a smart phone, a tablet, a wearable device, a personal digital assistant (PDA), a vehicle, and the like.

[0057] As yet another specific example, in an Internet of things (IoT) scenario, a terminal device may also be called an IoT device and represent a machine or other device that performs monitoring, sensing and/or measurements etc., and transmits the results of such monitoring, sensing and/or measurements etc. to another terminal device and/or a network equipment. The terminal device may in this case be a machine- to-machine (M2M) device, which may in a 3rd generation partnership project (3GPP) context be referred to as a machine-type communication (MTC) device.

[0058] As one particular example, the terminal device may be a UE implementing the 3GPP narrow band Internet of things (NB-IoT) standard. Particular examples of such machines or devices are sensors, metering devices such as power meters, industrial machinery, or home or personal appliances, e.g. refrigerators, televisions, personal wearables such as watches etc. In other scenarios, a terminal device may represent a vehicle or other equipment, for example, a medical instrument that is capable of monitoring, sensing and/or reporting etc. on its operational status or other functions associated with its operation.

[0059] As used herein, the terms “first”, “second” and so forth refer to different elements. The singular forms “a” and “an” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The terms “comprises”, “comprising”, “has”, “having”, “includes” and/or “including” as used herein, specify the presence of stated features, elements, and/or components and the like, but do not preclude the presence or addition of one or more other features, elements, components and/or combinations thereof The term “based on” is to be read as “based at least in part on”. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment”. The term “another embodiment” is to be read as “at least one other embodiment”. Other definitions, explicit and implicit, may be included below.

[0060] Wireless communication networks are widely deployed to provide various telecommunication services such as voice, video, data, messaging and broadcasts. To meet dramatically increasing network requirements on traffic capacity and data rates, one interesting option for communication technique development is to allow D2D such as vehicle-to-everything (V2X) communications to be implemented in a wireless communication network such as 4G/LTE or 5G/NR network. V2X communications may carry both non-safety and safety information, where each of the applications and services related to V2X communications may be associated with specific requirements sets, e.g., in terms of latency, reliability, data rates, etc.

[0061] V2X communications may take advantage of a network (NW) infrastructure, when available, but at least basic V2X connectivity needs to be possible even in case of lack of coverage. Many use cases may be defined for V2X communications, for example, vehicle-to-vehicle (V2V) communication, vehicle-to- pedestrian (V2P) communication, and vehicle-to-infrastructure/network (V2I/N) communication. Providing a 3GPP V2X interface may be economically advantageous because of the 3GPP economies of scale and it may enable tighter integration between communications with the NW infrastructure (V2I), pedestrian (V2P) and other vehicles (V2V), as compared to using a dedicated V2X technology. Direct unicast (i.e. one-to- one) and/or multicast (i.e. one-to-many) transmissions over SL may be needed in some use cases such as platooning, cooperative driving, dynamic ride sharing, etc.

[0062] As used herein, D2D is referred to in a broader sense to include communications between any type of UEs, and includes V2X communications between a vehicle UE and any other type of UE. D2D and/or V2X may be a component of many existing wireless technologies when it comes to direct communication between wireless devices. D2D and/or V2X communications as an underlay to cellular networks may be proposed as an approach to take advantage of the proximity of devices.

[0063] Although various embodiments are explained in the context of V2X communications, some embodiments can also be used for other types of direct communications, including D2D and other SL communications. Accordingly, the term “V2X” herein can be replaced with the term “D2D” for some exemplary embodiments. Moreover, throughout the disclosure, although some embodiments are described in the context of LTE evolution, they may be used in other wireless systems, including systems that operate according to 5G standards, also referred to as NR, or future radio technologies and standards.

[0064] Fig.1 A is a diagram illustrating an exemplary cellular-intelligent transport system (C-ITS) environment according to an embodiment of the present disclosure. Various embodiments of the present disclosure are described without limitation in the context of a communication system as illustrated in the diagram of Fig.1. The C-ITS aims at defining a new cellular eco-system for the delivery of vehicular services and their dissemination. Such eco-system may include both short-range and long-range V2X service transmissions, as depicted in Fig.lA. In particular, short-range communication may involve transmissions over the D2D link, also defined as SL or PC5 interface in 3 GPP, towards other vehicular UEs (100, 110) or roadside units (RSUs) (120). On the other hand, for long-range transmission, it is intended for the transmission over the Uu interface between a UE (e.g., a smart phone (130), a vehicle device (100, 105), etc.) and a base station (140), in which case packets may be disseminated to different intelligent transport system (ITS) service providers which may be road traffic authorities (150), road operators (160), automotive original equipment manufacturers (OEMs) (170), cellular operators, etc. In addition, interchange servers for country/region A (180) and country /region B (190) are also shown in Fig.lA.

[0065] When it comes to the SL interface, the first standardization effort in 3GPP dates back to Rel-12, targeting public safety use cases. Since then, a number of enhancements have been introduced with the objective to enlarge the use cases that could benefit of the D2D technology. In particular, in LTE Rel-14 and Rel-15, the extensions for the D2D work may consist of support of V2X communication, including any combination of direct communication between vehicles, pedestrians and infrastructure.

[0066] While LTE V2X mainly aims at traffic safety services, NR V2X has a much broader scope including not only basic safety services but also targeting non-safety applications, such as sensor/data sharing between vehicles with the objective to strengthen the perception of the surrounding environment. Hence a new set of applications, such as vehicles platooning, cooperative maneuver between vehicles, remote/autonomous driving may enjoy such enhanced SL framework.

[0067] In this new context, the expected requirements to meet the needed data rate, capacity, reliability, latency, communication range and speed are made more stringent. For example, given the variety of services that can be transmitted over the SL, a robust quality of service (QoS) framework which takes different performance requirements of various V2X services into account may be needed. Additionally, new radio protocols may be designed to handle more robust and reliable communication.

[0068] Fig. IB is a diagram illustrating an example of SL configuration according to an embodiment of the present disclosure. In a wireless communication network such as 5G/NR, SL radio bearer (RB) and SL logical channel (LCH) configuration for a UE may be preconfigured (e.g., by default provision), or configured by the network (NW) when the UE is in coverage. For instance, as shown in Fig. IB, when a TX UE wants to establish a new SERB for a new service, it can send a request to the associated gNB. After receiving the SLRB configuration from the gNB, the TX UE can establish the local SLRB accordingly and prepare for SL data transmission. Then the TX UE can inform a RX UE regarding necessary parameters (e.g., sequence number (SN) space for PDCP/RLC) before the data transmission starts, in order to enable successful reception of SL data at the RX UE side.

[0069] According to an exemplary embodiment, after two UEs discover each other, it is usually the TX UE who initiates the bearer request and configuration. In case of services requiring data transmission in both directions, two UEs may initiate two bearers in each direction. For the case that two UEs are served by different gNBs, or that one UE is in coverage while the other is out of coverage (OoC), the bearers initiated by the two UEs may be differently configured.

[0070] Fig.2A is a diagram illustrating an example of SLRB configuration exchange between two UEs according to an embodiment of the present disclosure. Between the SL unicast UE pair, as in Fig.2A, one UE (e.g., UE1) may send a configuration message (e.g., an SLRB configuration message) to the peer UE (e.g., UE2) via PC5-RRC (radio resource control) signaling, and the peer UE may decide whether to accept the configuration or reject it. For example, UE2 may send a configuration complete message to UE1 to indicate that the SLRB configuration is completed at UE2. If the peer UE (e.g., UE2) is in RRC CONNECTED mode, it may forward the SLRB configuration message to its serving gNB and let the gNB decide to accept or reject the SLRB configuration.

[0071] Fig.2B is a diagram illustrating an exemplary RLC configuration information element according to an embodiment of the present disclosure. In NR Uu case, an RLC unacknowledged mode (UM) entity has either a TX side or a RX side, while an RLC acknowledged mode (AM) entity has both TX side and RX side. For RLC UM, the TX side and the RX side are responsible for data transmission and reception respectively. For RLC AM, the TX side and the RX side are also responsible for RLC status report transmission and reception respectively, in addition to data transmission and reception. The TX side and RX side of an RLC entity may be configured differently by a gNB via RRC signaling. For example, the gNB may indicate different RLC SN length for the TX side and RX side of the RLC entity in an RLC-configuration information element, as shown in Fig.2B. In NR Uu case, according to an embodiment, an UM RLC entity may be configured by RRC signaling to use either a 6-bit SN or a 12-bit SN, while an AM RLC entity may be configured by RRC signaling to use either a 12-bit SN or an 18-bit SN.

[0072] According to an exemplary embodiment, for a NR SL, unicast at access stratum can be supported for services requiring high reliability. More specifically, at the physical layer, a hybrid automatic repeat request (HARQ) acknowledgement/negative acknowledgement (ACK/NACK) feedback can be configured such that a RX UE in a SL unicast pair can send an ACK feedback to a TX UE when a transport block (TB) is received successfully or send a NACK feedback to the TX UE when the TB reception fails. At the RLC layer, an RLC unacknowledged mode (UM) or an RLC acknowledged mode (AM) can be configured for SL unicast transmission. If the RLC UM mode is configured, an RLC entity is responsible for segmentation of RLC service data units (SDUs) from the packet data convergence protocol (PDCP) into suitably sized RLC PDUs. The RLC entity can also detect and remove duplicate received RLC PDUs. If the RLC AM mode is configured, in addition to segmentation and duplication detection, RLC entities in the TX UE and the RX UE are also responsible for retransmission of erroneous packets. The RX RLC entity can monitor the sequence numbers indicated in the headers of the received RLC PDUs and identify the missing ones. RLC status reports may be sent back to the TX RLC entity by the RX RLC entity requesting retransmission of the missing RLC PDUs. Based on the received status reports, the RLC entity at the TX UE can take the appropriate action and retransmit the missing RLC PDUs if needed.

[0073] Fig.3 is a diagram illustrating an example of RLC SLRB according to an embodiment of the present disclosure. As shown in Fig.3, an RLC entity (e.g., RLC1) is configured for UE1 and another RLC entity (e.g., RLC2) is configured for UE2. Regarding the SN length used for RLC AM operation, in principle, as long as the TX side (e.g., TX 1) of UE1 and the RX side (e.g., RX 2) of UE2 use the same RLC SN length (e.g. 12-bit), UE2 can receive the data/status report from UE1 (e.g., via LCHO). For the transmission in the direction from the TX side (e.g., TX 2) of UE2 to the RX side (e.g., RX 1) of UE1, a different RLC SN length (e.g., 18-bit) can be adopted as shown in Fig.3. It can be appreciated that although the example of RLC SLRB shown in Fig.3 is described in the context of bi-directional RLC AM SLRB, different RLC SN length configuration in two directions may be applicable to other possible cases (e.g., RLC UM operation).

[0074] In current NR Uu signaling procedures, both the TX side and the RX side RLC configuration of a UE are provided by the serving gNB. However, this may not be feasible for NR SL, for example, when the two UEs performing SL communications are served by different gNBs or one UE is in coverage while another UE is out of coverage, as (some of) the RX side configuration cannot be set properly without knowing the TX side configuration. Therefore, the current NR Uu signaling and framework may need to be adapted so that it can work properly for SL RLC configuration.

[0075] Various exemplary embodiments of the present disclosure propose a solution to support flexible SL RLC configuration. According to the proposed solution, a TX side and a RX side of an SL RLC AM/UM entity can use separate configuration/settings. In accordance with some exemplary embodiments, the network (e.g., a gNB) can configure (or provide pre-configuration information for) only the TX side of an SL RLC entity for a UE, while the RX side configuration of the SL RLC entity may be setup in a way that is dependent on the TX side configuration of the peer UE RLC entity. Taking advantage of various embodiments which may enable a TX side and a RX side of an SL RLC entity to be configured separately can achieve more flexible configuration of the SL RLC entity, and thus avoid problem bring in those scenarios where the TX and RX sides of the SL RLC entities may be configured by two different network nodes.

[0076] Figs.4A-4B are diagrams illustrating exemplary RLC entity configuration according to some embodiments of the present disclosure. Specifically, Fig.4A shows bi-directional RLC entity configuration in RRC CONNECTED state, and Fig.4B shows bi-directional RLC entity configuration in RRC IDLE/INACTIVE/OoC state. In accordance with some exemplary embodiments, different configuration/settings (e.g. SN length, etc.) may be used for a TX side and a RX side of a bi-directional SL RLC entity. The bi-directional SL RLC entity can be either a SL RLC AM entity or UM entity. In some embodiments, UE1 may be configured as the initiating UE that triggers the bi-directional SL RLC entity establishment and UE2 may be configured as the peer UE in SL unicast. It can be appreciated that in some cases, UE2 may also be configured as the initiating UE that triggers the bi-directional SL RLC entity establishment and correspondingly UE1 may also be configured the peer UE in SL unicast. Thus, the term UE1 and UE2 may be used in an inter-chargeable way without losing any meaning. Also, the scenario where UE1 is connected to gNBl and UE2 is connected to gNB2 is considered with all the possible combination among UE1, UE2 and gNBl and gNB2. In some embodiments, UE1 and UE2 may be connected to the same gNB (e.g., gNBl or gNB2).

[0077] In accordance with some exemplary embodiments, the configuration information from the network (or pre-configuration information) may only configure a TX side of an RLC entity. According to an exemplary embodiment, the TX side configuration of an RLC entity may include information about one or more of the following fields (but not limited to):

•SN length;

•Maximum retransmission threshold;

•PollByte;

•PollPDU; and •t-PollRetransmit.

[0078] In accordance with some exemplary embodiments, upon receiving configuration information from a network node (e.g., gNBl) or according to pre configuration information, UE1 can configure the RX side of the RLC entity dependently on the TX side configuration of the peer UE RLC entity (e.g., the RLC entity of UE2).

[0079] In accordance with some exemplary embodiments, when the network node (e.g., gNBl/gNB2) receives an SLRB configuration request from an RRC CONNECTED UE1/UE2, as shown in Fig.4A, the network node can provide SLRB configuration to UE1/UE2 to establish the TX side of an RLC entity, for example, via dedicated RRC signaling (e.g, including UE1/UE2 RLC AM TX side configuration), while the RLC RX side configuration may not be provided to UE1/UE2.

[0080] In accordance with some exemplary embodiments, the network node (e.g., gNBl/gNB2) can provide the SLRB configuration to UE1/UE2 to establish the RLC TX side for RRC IDLE/INACTIAVE UE, for example, via system information block (SIB) signaling, while the RLC RX side configuration may not be provided to UE1/UE2.

[0081] In accordance with some exemplary embodiments, UE1 can obtain the RLC TX side configuration, for example, via dedicated RRC signaling when in RRC CONNECTED state, or via SIB signaling when in RRC INACTIVE/IDLE state, or via pre-configuration when out-of-coverage.

[0082] In accordance with some exemplary embodiments, per PC5-RRC signaling UE1 may send its RLC TX side configuration to UE2 (e.g., without RLC RX side configuration of UE1). For example, as shown in Fig.4A and Fig.4B, UE1 may send SLRB configuration including UE1 RLC AM TX side configuration to UE2.

[0083] In accordance with some exemplary embodiments, per PC5-RRC signaling UE1 may receive RLC TX side configuration of UE2 (e.g., without RLC RX side configuration of UE2). For example, as shown in Fig.4A and Fig.4B, UE1 may receive a configuration complete message including UE2 RLC AM TX side configuration from UE2.

[0084] In accordance with some exemplary embodiments, when UE1 receives RLC TX side configuration from UE2 (which indicating a successful SLRB configuration at UE2), UE1 can establish its local RLC entity. As mentioned previously, the RLC TX side configuration of UE1 may follow the configuration obtained via NW configuration or pre-configuration information. The RLC RX side configuration of UE1 may follow the RLC TX side configuration of UE2. For example, the RLC RX side of UE1 and the RLC TX side of UE2 may use the same SN length.

[0085] In accordance with some exemplary embodiments, after receiving the RLC TX side configuration, UE1 may send the RLC TX side configuration to UE2, and UE2 can configure its RLC entity accordingly for both TX side and RX side. In an embodiment, UE1 may send RLC TX side configuration to UE2, and UE2 can configure UE2 TX side accordingly. In another embodiment, UE1 may send RLC TX side and RX side configuration to UE2, and UE2 can configure both UE2 TX and RX sides accordingly. In this case, the TX and RX sides of the RLC entity may be able to communicate without any errors. According to an embodiment, both TX side and RX side RLC configuration may be configured by UE2 based on the RLC TX side configuration of UE1, without configuration information from gNB2.

[0086] In accordance with some exemplary embodiments, UE2 can obtain the RLC TX side configuration, for example, via dedicated RRC signaling when in RRC CONNECTED state, or via SIB signaling when in RRC INACTIVE/IDLE state, or via pre-configuration when out-of-coverage.

[0087] In accordance with some exemplary embodiments, when RRC CONNECTED UE2 receives initiating signaling from UE1 (e.g., including UE1 RLC TX side configuration), UE2 can indicate to its serving cell (e.g., gNB2, which may be different from the serving cell of the UE1) the demand to establish a corresponding RLC entity, for example, without forwarding the TX side configuration of UE1 to gNB2.

[0088] In accordance with some exemplary embodiments, after UE2 receives the initiating signaling from UE1 and if UE2 obtains proper RLC TX side configuration (e.g., via RRC signaling, SIB signaling, or pre-configuration), UE2 can establish its local RLC entity. As mentioned previously, the RLC TX side configuration of UE2 may follow the configuration obtained via NW configuration or pre- configuration information. The RLC RX side configuration of UE2 may follow the RLC TX side configuration of UE1. For example, the RLC RX side of UE2 and the RLC TX side of UE1 may use the same SN length.

[0089] In accordance with some exemplary embodiments, UE2 may receive the RLC RX side configuration from UE1 and apply the received configuration for establishing the TX side of the RLC entity, so that the TX and RX sides of the RLC entity may be able to communicate without any errors.

[0090] In accordance with some exemplary embodiments, per PC5-RRC the UE2 may respond to UE1 about the RLC TX side configuration of UE2 and optionally an explicit flag indicating that the configuration is complete.

[0091] In accordance with some exemplary embodiments, after sending the RLC TX side configuration or pre-configuration to UE1, gNBl may inform gNB2 about the RLC TX side configured for UE1. According to an embodiment, gNBl may send the information about the RLC TX side configuration of UE1 to gNB2 via inter-node RRC messages. According to another embodiment, gNBl may send the information about the RLC TX side configuration of UE1 to the gNB2 via X2/Xn signaling. Optionally, gNB2 may further forward the information about the RLC TX side configuration of UE1 to UE2, and UE2 then can configure its RLC RX side accordingly.

[0092] In accordance with some exemplary embodiments, after sending the RLC TX side configuration or pre-configuration to UE2, gNB2 may inform gNB 1 about the RLC TX side configured for UE2. According to an embodiment, gNB2 may send the information about the RLC TX side configuration of UE2 to gNBl via inter-node RRC messages. According to another embodiment, gNB2 may send the information about the RLC TX side configuration of UE2 to gNBl via X2/Xn signaling. Optionally, gNB 1 may further forward the information about the RLC TX side configuration of UE2 to UE1, and UE1 then can configure its RLC RX side accordingly.

[0093] In accordance with some exemplary embodiments, UE1 and UE2 are in two different gNB coverages, and UE2 cannot be reached directly by gNBl. In this case, gNBl may send RLC TX side and/or RX side configuration to gNB2 which can forward the configuration to UE2. According to an embodiment, after sending the RLC TX side configuration or pre-configuration to UE1, gNBl may send the RLC RX side configuration of UE1 to gNB2 which may send the RLC RX side configuration of UE1 to UE2, if UE2 cannot be reached directly. According to another embodiment, after sending the RLC TX side configuration or pre- configuration to UE2, gNB2 may send the RLC RX side configuration of UE2 to gNBl which may send the RLC RX side configuration of UE2 to UE1, if UE1 cannot be reached directly.

[0094] It is noted that some embodiments of the present disclosure are mainly described in relation to LTE or NR specifications being used as non-limiting examples for certain exemplary network configurations and system deployments. As such, the description of exemplary embodiments given herein specifically refers to terminology which is directly related thereto. Such terminology is only used in the context of the presented non-limiting examples and embodiments, and does naturally not limit the present disclosure in any way. Rather, any other system configuration or radio technologies may equally be utilized as long as exemplary embodiments described herein are applicable.

[0095] Fig.5 is a flowchart illustrating a method 500 according to some embodiments of the present disclosure. The method 500 illustrated in Fig.5 may be performed by a first terminal device or an apparatus communicatively coupled to the first terminal device. In accordance with an exemplary embodiment, the first terminal device may comprise a communication device such as a UE1 in Figs.4A-4B. The first terminal device can be configured to perform D2D communications with one or more second terminal devices (e.g., UE2 in Figs.4A-4B) which may be able to support SL communications. Optionally, the first terminal device can be configured to perform cellular communication with a network node such as a base station.

[0096] According to the exemplary method 500 illustrated in Fig.5, the first terminal device can obtain first transmission side configuration of the first terminal device, as shown in block 502. The first transmission side configuration (e.g., UE1 RLC AM TX side configuration in Figs.4A-4B) may be related to RLC over a SL between the first terminal device and a second terminal device. In accordance with some exemplary embodiments, the first transmission side configuration may be obtained by the first terminal device according to at least one of: RRC signaling from a network node, system information signaling (e.g., SIB signaling) from the network node, and pre- configuration information for the first terminal device.

[0097] In accordance with some exemplary embodiments, the obtaining of the first transmission side configuration of the first terminal device may comprise: transmitting a request for SLRB configuration to a network node by the first terminal device, and obtaining by the first terminal device the first transmission side configuration of the first terminal device from the network node in response to the request for SLRB configuration.

[0098] In accordance with some exemplary embodiments, the first terminal device may transmit the first transmission side configuration of the first terminal device towards the second terminal device, as shown in block 504. According to an embodiment, the first terminal device may directly transmit the first transmission side configuration of the first terminal device to the second terminal device over the SL. Alternatively or additionally, the first terminal device may transmit the first transmission side configuration of the first terminal device to a network node which can forward the first transmission side configuration of the first terminal device to the second terminal device.

[0099] In accordance with some exemplary embodiments, the first terminal device may receive second transmission side configuration of the second terminal device from at least one of the second terminal device and a network node. The second transmission side configuration (e.g., UE2 RLC AM TX side configuration in Figs.4A-4B) may be related to RLC over the SL between the first terminal device and the second terminal device. Based at least in part on the second transmission side configuration of the second terminal device, the first terminal device can determine reception side configuration of the first terminal device for the RLC over the SL.

[00100] In accordance with some exemplary embodiments, the first terminal device may transmit the reception side configuration of the first terminal device to at least one of the second terminal device and the network node. Optionally, the network may forward the RLC configuration of the first terminal device to the second terminal device or other terminal devices.

[00101] In accordance with some exemplary embodiments, the first terminal device may transmit the transmission side configuration of the first terminal device to the second terminal device, so that the second terminal device can configure its RLC entity accordingly for both transmission side and reception side.

[00102] In accordance with some exemplary embodiments, the first terminal device can establish an RLC entity after having both transmission side configuration and reception side configuration (e.g., from the network node and/or the second terminal device).

[00103] Fig.6 is a flowchart illustrating a method 600 according to some embodiments of the present disclosure. The method 600 illustrated in Fig.6 may be performed by a second terminal device or an apparatus communicatively coupled to the second terminal device. In accordance with an exemplary embodiment, the second terminal device may comprise a communication device such as UE2 in Figs.4A-4B. The second terminal device can be configured to perform D2D communications with one or more first terminal devices (e.g., UE1 in Figs.4A-4B) which may be able to support SL communications. Optionally, the second terminal device can be configured to support cellular communication with a network node such as a base station. [00104] According to the exemplary method 600 illustrated in Fig.6, the second terminal device may receive first transmission side configuration of a first terminal device (e.g., the first terminal device as described with respect to Fig.5) from at least one of the first terminal device and a network node, as shown in block 602. The first transmission side configuration may be related to RLC over a SL between the first terminal device and the second terminal device. Based at least in part on the first transmission side configuration of the first terminal device, the second terminal device can determine reception side configuration of the second terminal device for the RLC over the SL, as shown in block 604.

[00105] In accordance with some exemplary embodiments, the second terminal device may transmit the reception side configuration of the second terminal device to at least one of the first terminal device and the network node. Optionally, the network may forward the RLC configuration of the second terminal device to the first terminal device or other terminal devices.

[00106] In accordance with some exemplary embodiments, the second terminal device may obtain its second transmission side configuration which is related to RLC over the SL between the first terminal device and the second terminal device. Optionally, the second terminal device may transmit the second transmission side configuration of the second terminal device towards the first terminal device. For example, the second terminal device may transmit the second transmission side configuration to the first terminal device over the SL, or to a network node which can forward the second transmission side configuration of the second terminal device to the first terminal device.

[00107] In accordance with some exemplary embodiments, the second terminal device may transmit the second transmission side configuration towards the first terminal device in response to reception of the first transmission side configuration of the first terminal device.

[00108] In accordance with some exemplary embodiments, the second transmission side configuration may be obtained by the second terminal device according to RRC signaling from the network node, system information signaling from the network node, and/or pre-configuration information for the second terminal device.

[00109] In accordance with some exemplary embodiments, the second terminal device can obtain the second transmission side configuration of the second terminal device by transmitting a request for SLRB configuration to the network node, and obtain the second transmission side configuration of the second terminal device from the network node in response to the request for SLRB configuration. According to an exemplary embodiment, the second terminal device may transmit the request for SLRB configuration to the network node, in response to reception of the first transmission side configuration of the first terminal device.

[00110] In accordance with some exemplary embodiments, the second terminal device can establish an RLC entity after having both transmission side configuration and reception side configuration (e.g., from the network node and/or the first terminal device).

[00111] In accordance with some exemplary embodiments, the second terminal device described with respect to Fig.6 may be equipped with the same or similar capabilities as those of the first terminal device described with respect to Fig.5 and accordingly may be configured to perform the method 500 illustrated in Fig.5. Similarly, the first terminal device described with respect to Fig.5 may be equipped with the same or similar capabilities as those of the second terminal device described with respect to Fig.6 and accordingly may be configured to perform the method 600 illustrated in Fig.6. [00112] Fig.7 is a flowchart illustrating a method 700 according to some embodiments of the present disclosure. The method 700 illustrated in Fig.7 may be performed by a first network node or an apparatus communicatively coupled to the first network node. In accordance with an exemplary embodiment, the first network node may comprise a base station such as gNBl and gNB2 in Figs.4A-4B. The first network node can be configured to serve one or more terminal devices (e.g., UE1 and UE2 in Figs.4A-4B) which may be able to support SL communications.

[00113] According to the exemplary method 700 illustrated in Fig.7, the first network node can provide first transmission side configuration to a first terminal device (e.g., the first terminal device as described with respect to Fig.5), as shown in block 702. The first transmission side configuration may be related to RLC over a SL between the first terminal device and a second terminal device (e.g., the second terminal device as described with respect to Fig.6). In accordance with some exemplary embodiments, the first transmission side configuration may be provided to the first terminal device by the first network node, in response to a request for SLRB configuration from the first terminal device.

[00114] Optionally, the first network node may inform the first transmission side configuration of the first terminal device to a second network node serving the second terminal device, as shown in block 704. According to an exemplary embodiment, the second network node can forward the first transmission side configuration of the first terminal device to the second terminal device.

[00115] In accordance with some exemplary embodiments, the first network node and the second network node may be the same network node. In this case, both the first terminal device and the second terminal device may be served by the first network node. According to an exemplary embodiment, the first network node may inform the first transmission side configuration of the first terminal device to the second terminal device.

[00116] In accordance with some exemplary embodiments, the first network node may obtain, from the first terminal device, reception side configuration of the first terminal device for the RLC over the SL. The reception side configuration of the first terminal device may be based at least in part on second transmission side configuration of the second terminal device for the RLC over the SL. Optionally, the first network node may inform the reception side configuration of the first terminal device to the second terminal device. Alternatively or additionally, the first network node may inform the reception side configuration of the first terminal device to the second network node which may forward the reception side configuration of the first terminal device to the second terminal device.

[00117] The various blocks shown in Figs.5-7 may be viewed as method steps, and/or as operations that result from operation of computer program code, and/or as a plurality of coupled logic circuit elements constructed to carry out the associated function(s). The schematic flow chart diagrams described above are generally set forth as logical flow chart diagrams. As such, the depicted order and labeled steps are indicative of specific embodiments of the presented methods. Other steps and methods may be conceived that are equivalent in function, logic, or effect to one or more steps, or portions thereof, of the illustrated methods. Additionally, the order in which a particular method occurs may or may not strictly adhere to the order of the corresponding steps shown.

[00118] Fig.8 is a block diagram illustrating an apparatus 800 according to various embodiments of the present disclosure. As shown in Fig.8, the apparatus 800 may comprise one or more processors such as processor 801 and one or more memories such as memory 802 storing computer program codes 803. The memory 802 may be non-transitory machine/processor/computer readable storage medium. In accordance with some exemplary embodiments, the apparatus 800 may be implemented as an integrated circuit chip or module that can be plugged or installed into a first terminal device as described with respect to Fig.5, a second terminal device as described with respect to Fig.6, or a first network node as described with respect to Fig.7. In such case, the apparatus 800 may be implemented as a first terminal device as described with respect to Fig.5, a second terminal device as described with respect to Fig.6, or a first network node as described with respect to Fig.7.

[00119] In some implementations, the one or more memories 802 and the computer program codes 803 may be configured to, with the one or more processors 801, cause the apparatus 800 at least to perform any operation of the method as described in connection with Fig.5. In other implementations, the one or more memories 802 and the computer program codes 803 may be configured to, with the one or more processors 801, cause the apparatus 800 at least to perform any operation of the method as described in connection with Fig.6. In other implementations, the one or more memories 802 and the computer program codes 803 may be configured to, with the one or more processors 801, cause the apparatus 800 at least to perform any operation of the method as described in connection with Fig.7. Alternatively or additionally, the one or more memories 802 and the computer program codes 803 may be configured to, with the one or more processors 801, cause the apparatus 800 at least to perform more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

[00120] Various embodiments of the present disclosure provide an apparatus which may comprise an obtaining unit and a transmitting unit. In an exemplary embodiment, the apparatus may be implemented in a first terminal device such as a UE. The obtaining unit may be operable to carry out the operation in block 502, and the transmitting unit may be operable to carry out the operation in block 504. Optionally, the obtaining unit and/or the transmitting unit may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

[00121] Various embodiments of the present disclosure provide an apparatus which may comprise a receiving unit and a determining unit. In an exemplary embodiment, the apparatus may be implemented in a second terminal device such as a UE. The receiving unit may be operable to carry out the operation in block 602, and the determining unit may be operable to carry out the operation in block 604. Optionally, the receiving unit and/or the determining unit may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

[00122] Various embodiments of the present disclosure provide an apparatus which may comprise a providing unit and optionally an informing unit. In an exemplary embodiment, the apparatus may be implemented in a first network node such as a base station. The providing unit may be operable to carry out the operation in block 702, and the informing unit may be operable to carry out the operation in block 704. Optionally, the providing unit and/or the informing unit may be operable to carry out more or less operations to implement the proposed methods according to the exemplary embodiments of the present disclosure.

[00123] According to various embodiments of the present disclosure, some proposals may be provided as below:

• Proposal 1 : When an RRC CONNECTED UE receives an RLC AM SLRB configuration message, it forwards to the serving gNB. It may be up to the gNB to accept or reject the RLC AM SLRB establishment.

Proposal 2: When an RRC IDLE/INACTIVE/OoC UE receives an RLC AM SLRB configuration message, the UE can decide to accept or reject the RLC AM SLRB establishment.

• Proposal 3 : It may be considered if TX side and RX side of the same SL RLC AM entity can adopt different RLC SN lengths.

• Proposal 4: The established SL RLC AM entity can operate as SL RLC UM if the corresponding peer UE RLC entity using the same logical channel identifier (LCID) is UM.

[00124] Fig.9 is a block diagram illustrating a telecommunication network connected via an intermediate network to a host computer in accordance with some embodiments of the present disclosure.

[00125] With reference to Fig.9, in accordance with an embodiment, a communication system includes a telecommunication network 910, such as a 3GPP- type cellular network, which comprises an access network 911, such as a radio access network, and a core network 914. The access network 911 comprises a plurality of base stations 912a, 912b, 912c, such as NBs, eNBs, gNBs or other types of wireless access points, each defining a corresponding coverage area 913a, 913b, 913c. Each base station 912a, 912b, 912c is connectable to the core network 914 over a wired or wireless connection 915. A first UE 991 located in a coverage area 913c is configured to wirelessly connect to, or be paged by, the corresponding base station 912c. A second UE 992 in a coverage area 913a is wirelessly connectable to the corresponding base station 912a. While a plurality of UEs 991, 992 are illustrated in this example, the disclosed embodiments are equally applicable to a situation where a sole UE is in the coverage area or where a sole UE is connecting to the corresponding base station 912.

[00126] The telecommunication network 910 is itself connected to a host computer 930, which may be embodied in the hardware and/or software of a standalone server, a cloud-implemented server, a distributed server or as processing resources in a server farm. The host computer 930 may be under the ownership or control of a service provider, or may be operated by the service provider or on behalf of the service provider. Connections 921 and 922 between the telecommunication network 910 and the host computer 930 may extend directly from the core network 914 to the host computer 930 or may go via an optional intermediate network 920. An intermediate network 920 may be one of, or a combination of more than one of, a public, private or hosted network; the intermediate network 920, if any, may be a backbone network or the Internet; in particular, the intermediate network 920 may comprise two or more sub-networks (not shown).

[00127] The communication system of Fig.9 as a whole enables connectivity between the connected UEs 991, 992 and the host computer 930. The connectivity may be described as an over-the-top (OTT) connection 950. The host computer 930 and the connected UEs 991, 992 are configured to communicate data and/or signaling via the OTT connection 950, using the access network 911, the core network 914, any intermediate network 920 and possible further infrastructure (not shown) as intermediaries. The OTT connection 950 may be transparent in the sense that the participating communication devices through which the OTT connection 950 passes are unaware of routing of uplink and downlink communications. For example, the base station 912 may not or need not be informed about the past routing of an incoming downlink communication with data originating from the host computer 930 to be forwarded (e.g., handed over) to a connected UE 991. Similarly, the base station 912 need not be aware of the future routing of an outgoing uplink communication originating from the UE 991 towards the host computer 930.

[00128] Fig.10 is a block diagram illustrating a host computer communicating via a base station with a UE over a partially wireless connection in accordance with some embodiments of the present disclosure. [00129] Example implementations, in accordance with an embodiment, of the UE, base station and host computer discussed in the preceding paragraphs will now be described with reference to Fig.10. In a communication system 1000, a host computer 1010 comprises hardware 1015 including a communication interface 1016 configured to set up and maintain a wired or wireless connection with an interface of a different communication device of the communication system 1000. The host computer 1010 further comprises a processing circuitry 1018, which may have storage and/or processing capabilities. In particular, the processing circuitry 1018 may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The host computer 1010 further comprises software 1011, which is stored in or accessible by the host computer 1010 and executable by the processing circuitry 1018. The software 1011 includes a host application 1012. The host application 1012 may be operable to provide a service to a remote user, such as UE 1030 connecting via an OTT connection 1050 terminating at the UE 1030 and the host computer 1010. In providing the service to the remote user, the host application 1012 may provide user data which is transmitted using the OTT connection 1050.

[00130] The communication system 1000 further includes a base station 1020 provided in a telecommunication system and comprising hardware 1025 enabling it to communicate with the host computer 1010 and with the UE 1030. The hardware 1025 may include a communication interface 1026 for setting up and maintaining a wired or wireless connection with an interface of a different communication device of the communication system 1000, as well as a radio interface 1027 for setting up and maintaining at least a wireless connection 1070 with the UE 1030 located in a coverage area (not shown in Fig.10) served by the base station 1020. The communication interface 1026 may be configured to facilitate a connection 1060 to the host computer 1010. The connection 1060 may be direct or it may pass through a core network (not shown in Fig.10) of the telecommunication system and/or through one or more intermediate networks outside the telecommunication system. In the embodiment shown, the hardware 1025 of the base station 1020 further includes a processing circuitry 1028, which may comprise one or more programmable processors, application- specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The base station 1020 further has software 1021 stored internally or accessible via an external connection.

[00131] The communication system 1000 further includes the UE 1030 already referred to. Its hardware 1035 may include a radio interface 1037 configured to set up and maintain a wireless connection 1070 with a base station serving a coverage area in which the UE 1030 is currently located. The hardware 1035 of the UE 1030 further includes a processing circuitry 1038, which may comprise one or more programmable processors, application-specific integrated circuits, field programmable gate arrays or combinations of these (not shown) adapted to execute instructions. The UE 1030 further comprises software 1031, which is stored in or accessible by the UE 1030 and executable by the processing circuitry 1038. The software 1031 includes a client application 1032. The client application 1032 may be operable to provide a service to a human or non-human user via the UE 1030, with the support of the host computer 1010. In the host computer 1010, an executing host application 1012 may communicate with the executing client application 1032 via the OTT connection 1050 terminating at the UE 1030 and the host computer 1010. In providing the service to the user, the client application 1032 may receive request data from the host application 1012 and provide user data in response to the request data. The OTT connection 1050 may transfer both the request data and the user data. The client application 1032 may interact with the user to generate the user data that it provides.

[00132] It is noted that the host computer 1010, the base station 1020 and the UE 1030 illustrated in Fig.10 may be similar or identical to the host computer 930, one of base stations 912a, 912b, 912c and one of UEs 991, 992 of Fig.9, respectively. This is to say, the inner workings of these entities may be as shown in Fig.10 and independently, the surrounding network topology may be that of Fig.9.

[00133] In Fig.10, the OTT connection 1050 has been drawn abstractly to illustrate the communication between the host computer 1010 and the UE 1030 via the base station 1020, without explicit reference to any intermediary devices and the precise routing of messages via these devices. Network infrastructure may determine the routing, which it may be configured to hide from the UE 1030 or from the service provider operating the host computer 1010, or both. While the OTT connection 1050 is active, the network infrastructure may further take decisions by which it dynamically changes the routing (e.g., on the basis of load balancing consideration or reconfiguration of the network).

[00134] Wireless connection 1070 between the UE 1030 and the base station 1020 is in accordance with the teachings of the embodiments described throughout this disclosure. One or more of the various embodiments improve the performance of OTT services provided to the UE 1030 using the OTT connection 1050, in which the wireless connection 1070 forms the last segment. More precisely, the teachings of these embodiments may improve the latency and the power consumption, and thereby provide benefits such as lower complexity, reduced time required to access a cell, better responsiveness, extended battery lifetime, etc.

[00135] A measurement procedure may be provided for the purpose of monitoring data rate, latency and other factors on which the one or more embodiments improve. There may further be an optional network functionality for reconfiguring the OTT connection 1050 between the host computer 1010 and the UE 1030, in response to variations in the measurement results. The measurement procedure and/or the network functionality for reconfiguring the OTT connection 1050 may be implemented in software 1011 and hardware 1015 of the host computer 1010 or in software 1031 and hardware 1035 of the UE 1030, or both. In embodiments, sensors (not shown) may be deployed in or in association with communication devices through which the OTT connection 1050 passes; the sensors may participate in the measurement procedure by supplying values of the monitored quantities exemplified above, or supplying values of other physical quantities from which the software 1011, 1031 may compute or estimate the monitored quantities. The reconfiguring of the OTT connection 1050 may include message format, retransmission settings, preferred routing etc.; the reconfiguring need not affect the base station 1020, and it may be unknown or imperceptible to the base station 1020. Such procedures and functionalities may be known and practiced in the art. In certain embodiments, measurements may involve proprietary UE signaling facilitating the host computer 1010’s measurements of throughput, propagation times, latency and the like. The measurements may be implemented in that the software 1011 and 1031 causes messages to be transmitted, in particular empty or ‘dummy’ messages, using the OTT connection 1050 while it monitors propagation times, errors etc.

[00136] Fig.11 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig.9 and Fig.10. For simplicity of the present disclosure, only drawing references to Fig.11 will be included in this section. In step 1110, the host computer provides user data. In substep 1111 (which may be optional) of step 1110, the host computer provides the user data by executing a host application. In step 1120, the host computer initiates a transmission carrying the user data to the UE. In step 1130 (which may be optional), the base station transmits to the UE the user data which was carried in the transmission that the host computer initiated, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1140 (which may also be optional), the UE executes a client application associated with the host application executed by the host computer.

[00137] Fig.12 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig.9 and Fig.10. For simplicity of the present disclosure, only drawing references to Fig.12 will be included in this section. In step 1210 of the method, the host computer provides user data. In an optional substep (not shown) the host computer provides the user data by executing a host application. In step 1220, the host computer initiates a transmission carrying the user data to the UE. The transmission may pass via the base station, in accordance with the teachings of the embodiments described throughout this disclosure. In step 1230 (which may be optional), the UE receives the user data carried in the transmission.

[00138] Fig.13 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig.9 and Fig.10. For simplicity of the present disclosure, only drawing references to Fig.13 will be included in this section. In step 1310 (which may be optional), the UE receives input data provided by the host computer. Additionally or alternatively, in step 1320, the UE provides user data. In substep 1321 (which may be optional) of step 1320, the UE provides the user data by executing a client application. In substep 1311 (which may be optional) of step 1310, the UE executes a client application which provides the user data in reaction to the received input data provided by the host computer. In providing the user data, the executed client application may further consider user input received from the user. Regardless of the specific manner in which the user data was provided, the UE initiates, in substep 1330 (which may be optional), transmission of the user data to the host computer. In step 1340 of the method, the host computer receives the user data transmitted from the UE, in accordance with the teachings of the embodiments described throughout this disclosure.

[00139] Fig.14 is a flowchart illustrating a method implemented in a communication system, in accordance with an embodiment. The communication system includes a host computer, a base station and a UE which may be those described with reference to Fig.9 and Fig.10. For simplicity of the present disclosure, only drawing references to Fig.14 will be included in this section. In step 1410 (which may be optional), in accordance with the teachings of the embodiments described throughout this disclosure, the base station receives user data from the UE. In step 1420 (which may be optional), the base station initiates transmission of the received user data to the host computer. In step 1430 (which may be optional), the host computer receives the user data carried in the transmission initiated by the base station.

[00140] According to some exemplary embodiments, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise providing user data at the host computer. Optionally, the method may comprise, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station which may perform any step of the exemplary method 700 as describe with respect to Fig.7.

[00141] According to some exemplary embodiments, there is provided a communication system including a host computer. The host computer may comprise processing circuitry configured to provide user data, and a communication interface configured to forward the user data to a cellular network for transmission to a UE. The cellular network may comprise a base station having a radio interface and processing circuitry. The base station’ s processing circuitry may be configured to perform any step of the exemplary method 700 as describe with respect to Fig.7.

[00142] According to some exemplary embodiments, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise providing user data at the host computer. Optionally, the method may comprise, at the host computer, initiating a transmission carrying the user data to the UE via a cellular network comprising the base station. The UE may perform any step of the exemplary method 500 as describe with respect to Fig.5 or any step of the exemplary method 600 as describe with respect to Fig.6.

[00143] According to some exemplary embodiments, there is provided a communication system including a host computer. The host computer may comprise processing circuitry configured to provide user data, and a communication interface configured to forward user data to a cellular network for transmission to a UE. The UE may comprise a radio interface and processing circuitry. The UE’s processing circuitry may be configured to perform any step of the exemplary method 500 as describe with respect to Fig.5 or any step of the exemplary method 600 as describe with respect to Fig.6.

[00144] According to some exemplary embodiments, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise, at the host computer, receiving user data transmitted to the base station from the UE which may perform any step of the exemplary method 500 as describe with respect to Fig.5 or any step of the exemplary method 600 as describe with respect to Fig.6.

[00145] According to some exemplary embodiments, there is provided a communication system including a host computer. The host computer may comprise a communication interface configured to receive user data originating from a transmission from a UE to a base station. The UE may comprise a radio interface and processing circuitry. The UE’s processing circuitry may be configured to perform any step of the exemplary method 500 as describe with respect to Fig.5 or any step of the exemplary method 600 as describe with respect to Fig.6.

[00146] According to some exemplary embodiments, there is provided a method implemented in a communication system which may include a host computer, a base station and a UE. The method may comprise, at the host computer, receiving, from the base station, user data originating from a transmission which the base station has received from the UE. The base station may perform any step of the exemplary method 700 as describe with respect to Fig.7.

[00147] According to some exemplary embodiments, there is provided a communication system which may include a host computer. The host computer may comprise a communication interface configured to receive user data originating from a transmission from a UE to a base station. The base station may comprise a radio interface and processing circuitry. The base station’s processing circuitry may be con figured to perform any step of the exemplary method 700 as describe with respect to Fig.7.

[00148] In general, the various exemplary embodiments may be implemented in hardware or special purpose chips, circuits, software, logic or any combination thereof. For example, 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, although the disclosure is not limited thereto. While various aspects of the exemplary embodiments of this disclosure may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

[00149] As such, it should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be practiced in various components such as integrated circuit chips and modules. It should thus be appreciated that the exemplary embodiments of this disclosure may be realized in an apparatus that is embodied as an integrated circuit, where the integrated circuit may comprise circuitry (as well as possibly firmware) for embodying at least one or more of a data processor, a digital signal processor, baseband circuitry and radio frequency circuitry that are configurable so as to operate in accordance with the exemplary embodiments of this disclosure.

[00150] It should be appreciated that at least some aspects of the exemplary embodiments of the disclosure may be embodied in computer-executable instructions, such as in one or more program modules, executed by one or more computers or other devices. Generally, program modules include routines, programs, objects, components, data structures, etc. that perform particular tasks or implement particular abstract data types when executed by a processor in a computer or other device. The computer executable instructions may be stored on a computer readable medium such as a hard disk, optical disk, removable storage media, solid state memory, random access memory (RAM), etc. As will be appreciated by one of skill in the art, the function of the program modules may be combined or distributed as desired in various embodiments. In addition, the function may be embodied in whole or partly in firmware or hardware equivalents such as integrated circuits, field programmable gate arrays (FPGA), and the like.

[00151] The present disclosure includes any novel feature or combination of features disclosed herein either explicitly or any generalization thereof. Various modifications and adaptations to the foregoing exemplary embodiments of this disclosure may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings. However, any and all modifications will still fall within the scope of the non-limiting and exemplary embodiments of this disclosure.

Claims

CLAIMS What is claimed is:

1. A method (500) performed by a first terminal device, comprising: obtaining (502) first transmission side configuration of the first terminal device, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and a second terminal device; and transmitting (504) the first transmission side configuration of the first terminal device towards the second terminal device.

2. The method according to claim 1 , wherein the first transmission side configuration is obtained by the first terminal device according to at least one of: radio resource control signaling from a network node; system information signaling from the network node; and pre-configuration information for the first terminal device.

3. The method according to claim 1 or 2, wherein the obtaining of the first transmission side configuration of the first terminal device comprises: transmitting a request for sidelink radio bearer configuration to a network node; and obtaining the first transmission side configuration of the first terminal device from the network node in response to the request for sidelink radio bearer configuration.

4. The method according to any of claims 1-3, further comprising: receiving second transmission side configuration of the second terminal device from at least one of the second terminal device and a network node, wherein the second transmission side configuration is related to radio link control over the sidelink between the first terminal device and the second terminal device; and determining reception side configuration of the first terminal device for the radio link control over the sidelink, based at least in part on the second transmission side configuration of the second terminal device.

5. The method according to claim 4, further comprising: transmitting the reception side configuration of the first terminal device to at least one of the second terminal device and the network node.

6. A method (600) performed by a second terminal device, comprising: receiving (602) first transmission side configuration of a first terminal device from at least one of the first terminal device and a network node, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and the second terminal device; and determining (604) reception side configuration of the second terminal device for the radio link control over the sidelink, based at least in part on the first transmission side configuration of the first terminal device.

7. The method according to claim 6, further comprising: transmitting the reception side configuration of the second terminal device to at least one of the first terminal device and the network node.

8. The method according to claim 6 or 7, further comprising: obtaining second transmission side configuration of the second terminal device, wherein the second transmission side configuration is related to radio link control over the sidelink between the first terminal device and the second terminal device; and transmitting the second transmission side configuration of the second terminal device towards the first terminal device.

9. The method according to claim 8, wherein the second transmission side configuration is obtained by the second terminal device according to at least one of: radio resource control signaling from the network node; system information signaling from the network node; and pre-configuration information for the second terminal device.

10. The method according to claim 8 or 9, wherein the obtaining of the second transmission side configuration of the second terminal device comprises: transmitting a request for sidelink radio bearer configuration to the network node; and obtaining the second transmission side configuration of the second terminal device from the network node in response to the request for sidelink radio bearer configuration.

11. The method according to claim 10, wherein the request for sidelink radio bearer configuration is transmitted to the network node in response to the reception of the first transmission side configuration of the first terminal device.

12. A method (700) performed by a first network node, comprising: providing (702) first transmission side configuration to a first terminal device, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and a second terminal device.

13. The method according to claim 12, wherein the first transmission side configuration is provided to the first terminal device in response to a request for sidelink radio bearer configuration from the first terminal device.

14. The method according to claim 12 or 13, further comprising: informing (704) the first transmission side configuration of the first terminal device to a second network node serving the second terminal device.

15. The method according to claim 12 or 13, further comprising: informing the first transmission side configuration of the first terminal device to the second terminal device.

16. The method according to any of claims 12-15, further comprising: obtaining, from the first terminal device, reception side configuration of the first terminal device for the radio link control over the sidelink, wherein the reception side configuration of the first terminal device is based at least in part on second transmission side configuration of the second terminal device for the radio link control over the sidelink; and informing the reception side configuration of the first terminal device to the second terminal device or a second network node serving the second terminal device.

17. A first terminal device (800), comprising: one or more processors (801); and one or more memories (802) storing computer program codes (803), the one or more memories (802) and the computer program codes (803) configured to, with the one or more processors (801), cause the first terminal device (800) at least to: obtain first transmission side configuration of the first terminal device, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and a second terminal device; and transmit the first transmission side configuration of the first terminal device towards the second terminal device.

18. The first terminal device according to claim 16, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the first terminal device to perform the method according to any one of claims 2-5.

19. A second terminal device (800), comprising: one or more processors (801); and one or more memories (802) storing computer program codes (803), the one or more memories (802) and the computer program codes (803) configured to, with the one or more processors (801), cause the second terminal device (800) at least to: receive first transmission side configuration of a first terminal device from at least one of the first terminal device and a network node, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and the second terminal device; and determine reception side configuration of the second terminal device for the radio link control over the sidelink, based at least in part on the first transmission side configuration of the first terminal device.

20. The second terminal device according to claim 18, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the second terminal device to perform the method according to any one of claims 7-11.

21. A first network node (800), comprising: one or more processors (801); and one or more memories (802) storing computer program codes (803), the one or more memories (802) and the computer program codes (803) configured to, with the one or more processors (801), cause the first network node (800) at least to: provide first transmission side configuration to a first terminal device, wherein the first transmission side configuration is related to radio link control over a sidelink between the first terminal device and a second terminal device.

22. The first network node according to claim 20, wherein the one or more memories and the computer program codes are configured to, with the one or more processors, cause the first network node to perform the method according to any one of claims 13- 16.

23. A computer-readable medium having computer program codes (803) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 1-5.

24. A computer-readable medium having computer program codes (803) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 6-11.

25. A computer-readable medium having computer program codes (803) embodied thereon which, when executed on a computer, cause the computer to perform any step of the method according to any one of claims 12-16.