METHODS AND APPARATUSES FOR SWITCHING TO A RELAY UE IN AN RRC IDLE OR INACTIVE STATE

Embodiments of the present application relate to methods and apparatuses for switching to a relay user equipment (UE) in a radio resource control (RRC) idle or inactive state. According to an embodiment of the present application, a target network node includes a transceiver and a processor coupled to the transceiver; and the processor is configured: to receive a handover request message via the transceiver from a source network node, wherein the handover request message includes identifier (ID) information of a candidate relay user equipment (UE) for a UE; and to transmit a response message via the transceiver to the source network node, wherein the response message includes at least one of: a handover request acknowledge message including ID information of a target relay UE for the UE; or a message to cancel a resource preparation of path switching for the UE.

TECHNICAL FIELD

Embodiments of the present application generally relate to wireless communication technology, in particular to methods and apparatuses for switching to a relay user equipment (UE) in a radio resource control (RRC) idle or inactive state.

BACKGROUND

Vehicle to everything (V2X) has been introduced into 5G wireless communication technology. In terms of a channel structure of V2X communication, the direct link between two user equipments (UEs) is called a sidelink. A sidelink is a long-term evolution (LTE) feature introduced in 3GPP Release 12, and enables a direct communication between proximal UEs, and data does not need to go through a base station (BS) or a core network.

In the 3rd Generation Partnership Project (3GPP), deployment of a relay node (RN) in a wireless communication system is promoted. One objective of deploying a RN is to enhance the coverage area of a BS by improving the throughput of a UE that is located in the coverage or far from the BS, which can result in relatively low signal quality. A RN may also be named as a relay UE in some cases. A 3GPP 5G sidelink system including a relay UE may be named as a sidelink relay system. A U2N relay UE is a UE that provides functionality to support connectivity to the network for U2N remote UE(s).

A UE may be in an RRC connected state, an RRC idle state, or an RRC inactive state. An RRC connected state may also be named as “a connected state” or “an RRC CONNECTED state” or the like. An RRC idle state may also be named as “an idle state” or “an RRC_IDLE state” or the like. An RRC inactive state may also be named as “an inactive state” or “an RRC_INACTIVE state” or the like.

Currently, in a wireless communication system or the like, details regarding how to switch to a relay UE in an RRC idle state or an RRC inactive state have not been specifically discussed yet.

SUMMARY

Some embodiments of the present application provide a target network node (e.g., a target base station (BS)). The target network node includes a transceiver and a processor coupled to the transceiver; and the processor is configured: to receive a handover request message via the transceiver from a source network node, wherein the handover request message includes identifier (ID) information of a candidate relay user equipment (UE) for a UE; and to transmit a response message via the transceiver to the source network node, wherein the response message includes at least one of: a handover request acknowledge message including ID information of a target relay UE for the UE; or a message to cancel a resource preparation of path switching for the UE.

In some embodiments, the handover request acknowledge message further includes an RRC state of the target relay UE.

In some embodiments, the RRC state of the target relay UE is an RRC connected state or an RRC non-connected state.

In some embodiments, the message to cancel the resource preparation of path switching for the UE is a handover preparation failure message.

In some embodiments, the message to cancel the resource preparation of path switching for the UE includes a failure cause associated with the target relay UE.

In some embodiments, the failure cause includes at least one of: the target relay UE being high load; the target relay UE being overloaded; the target relay UE being not reached; or the target relay UE being not found.

In some embodiments, the processor of the target network node is configured: to determine whether the target relay UE is in an RRC connected state or an RRC non-connected state; and to transmit a paging message to the target relay UE, in response to determining that the target relay UE is in the RRC non-connected state.

In some embodiments, the RRC non-connected state includes at least one of an RRC idle state or an RRC inactive state.

In some embodiments, to transmit the response message, the processor of the target network node is configured: to transmit the handover request acknowledge message via the transceiver to the source network node before transiting the target relay UE to the RRC connected state; and to transmit the message to cancel the resource preparation of path switching for the UE via the transceiver to the source network node, in response to failing to reaching the target relay UE by the paging message.

In some embodiments, to transmit the response message, the processor of the target network node is configured: to transmit the handover request acknowledge message to the source network node, in response to the target relay UE entering into an RRC connected state after a reception of the paging message.

In some embodiments, to transmit the paging message, the processor of the target network node is configured: to transmit a first message for transiting the target relay UE from the RRC non-connected state to the RRC connected state via the transceiver to an access and mobility management function (AMF), in response to determining that the target relay UE is in the RRC non-connected state; and to receive a second message for triggering a radio access network (RAN) paging operation via the transceiver from the AMF; and to transmit the paging message to the target relay UE.

In some embodiments, the first message includes at least one of: the ID information of the target relay UE; or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state.

In some embodiments, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, the second message includes access stratum (AS) layer ID information of the target relay UE.

In some embodiments, the AS layer ID information of the target relay UE is: a NG-5G-S-temporary mobile subscriber identity (TMSI).

In some embodiments, a first association between a source Layer-2 ID of the target relay UE and AS layer ID information of the target relay UE is maintained in the AMF.

In some embodiments, the AS layer ID information of the target relay UE is identified by the AMF based on the source Layer-2 ID of the target relay UE and the first association.

In some embodiments, to transmit the paging message, the processor of the target network node is configured: to transmit a third message for transiting the target relay UE from the RRC non-connected state to the RRC connected state via the transceiver to a set of neighbour network nodes, in response to determining that the target relay UE is in the RRC non-connected state; and to receive a fourth message for triggering a radio access network (RAN) paging operation via the transceiver from a last serving network node of the UE, wherein the set of neighbour network nodes includes the last serving network node; and to transmit a paging message to the target relay UE. The last serving network node may be the last serving gNB, which configures the connected UE to an inactive state. The last serving gNB will keep the context of the UE.

In some embodiments, the third message includes at least one of: the ID information of the target relay UE; or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state.

In some embodiments, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, at least one of the fourth message or the paging message includes access stratum (AS) layer ID information of the target relay UE.

In some embodiments, the AS layer ID information of the target relay UE is an inactive radio network temporary identifier (I-RNTI) or a short I-RNTI.

In some embodiments, in response to the fourth message including the AS layer ID information of the target relay UE, a second association between a source Layer-2 ID of the target relay UE and the AS layer ID information of the target relay UE is maintained in the last serving network node.

In some embodiments, the AS layer ID information of the target relay UE is identified by the last serving network node based on the source Layer-2 ID of the target relay UE and the second association.

In some embodiments, in response to the fourth message not including the AS layer ID information of the target relay UE, the processor of the target network node is configured: to maintain a third association between the source Layer-2 ID of the target relay UE and the AS layer ID information of the target relay UE; and to identify the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the third association.

In some embodiments, the paging message includes: a source Layer-2 ID of the target relay UE, or access stratum (AS) layer ID information of the target relay UE.

In some embodiments, the AS layer ID information of the target relay UE is: a NG-5G-S-temporary mobile subscriber identity (TMSI), or an inactive radio network temporary identifier (I-RNTI).

In some embodiments, to transmit the paging message including the AS layer ID information of the target relay UE, the processor of the target network node is configured: to maintain a fourth association between the source Layer-2 ID of the target relay UE and the AS layer ID information of the target relay UE; and to identify the AS layer ID information of the target relay UE on its own based on the source Layer-2 ID of the target relay UE and the fourth association.

In some embodiments, the processor of the target network node is configured to receive the source Layer-2 ID of the target relay UE via the transceiver from a serving cell of the target relay UE.

Some embodiments of the present application provide a method, which may be performed by a target network node (e.g., a target BS). The method includes: receiving a handover request message from a source network node, wherein the handover request message includes identifier (ID) information of a candidate relay user equipment (UE) for a UE; and transmitting a response message to the source network node, wherein the response message includes at least one of: a handover request acknowledge message including ID information of a target relay UE for the UE; or a message to cancel a resource preparation of path switching for the UE.

Some embodiments of the present application provide an access and mobility management function (AMF). The AMF includes a transceiver and a processor coupled to the transceiver; and the processor is configured: to receive a first message for transiting a target relay user equipment (UE) from a radio resource control (RRC) non-connected state to an RRC connected state via the transceiver from a target network node; and to transmit a second message for triggering a radio access network (RAN) paging operation to the target relay UE via the transceiver to the target network node.

In some embodiments, the RRC non-connected state includes at least one of an RRC idle state or an RRC inactive state.

In some embodiments, the first message includes at least one of: identifier (ID) information of the target relay UE; or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state.

In some embodiments, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, the second message includes access stratum (AS) layer ID information of the target relay UE.

In some embodiments, the AS layer ID information of the target relay UE is: a NG-5G-S-temporary mobile subscriber identity (TMSI).

In some embodiments, the processor of the AMF is configured: to maintain an association between a source Layer-2 ID of the target relay UE and AS layer ID information of the target relay UE; and to identify the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, the processor of the AMF is configured to receive the source Layer-2 ID of the target relay UE via the transceiver from a serving cell of the target relay UE.

Some embodiments of the present application provide a method, which may be performed by an AMF. The method includes: receiving a message for transiting a target relay user equipment (UE) from a radio resource control (RRC) non-connected state to an RRC connected state from a target network node; and transmitting a message for triggering a radio access network (RAN) paging operation to the target relay UE to the target network node.

Some embodiments of the present application provide a last serving network node of a user equipment (UE). The last serving network node of the UE includes a transceiver and a processor coupled to the transceiver; and the processor is configured: to receive a third message for transiting a target relay user equipment (UE) from a radio resource control (RRC) non-connected state to an RRC connected state via the transceiver from a target network node; and to transmit a fourth message for triggering a radio access network (RAN) paging operation to the target relay UE via the transceiver to the target network node.

In some embodiments, the third message includes at least one of: the ID information of the target relay UE; or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state.

In some embodiments, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, the fourth message includes access stratum (AS) layer ID information of the target relay UE.

In some embodiments, the AS layer ID information of the target relay UE is an inactive radio network temporary identifier (I-RNTI) or a short I-RNTI.

In some embodiments, in response to the fourth message including the AS layer ID information of the target relay UE, the processor of the last serving network node is configured: to maintain a first association between a source Layer-2 ID of the target relay UE and the AS layer ID information of the target relay UE; and to identify the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the first association.

In some embodiments, in response to the fourth message not including the AS layer ID information of the target relay UE, a second association between a source Layer-2 ID of the target relay UE and the AS layer ID information of the target relay UE is maintained in the target network node; and the AS layer ID information of the target relay UE is identified by the target network node based on the source Layer-2 ID of the target relay UE and the second association.

Some embodiments of the present application provide a method, which may be performed by a last serving network node of a user equipment (UE). The method includes: receiving a message for transiting a target relay user equipment (UE) from a radio resource control (RRC) non-connected state to an RRC connected state from a target network node; and transmitting a message for triggering a radio access network (RAN) paging operation to the target relay UE to the target network node.

Some embodiments of the present application also provide an apparatus for wireless communications. The apparatus includes: a non-transitory computer-readable medium having stored thereon computer-executable instructions; a receiving circuitry; a transmitting circuitry; and a processor coupled to the non-transitory computer-readable medium, the receiving circuitry and the transmitting circuitry, wherein the computer-executable instructions cause the processor to implement any of the above-mentioned methods performed by a network node (e.g., a target BS), and an AMF, or a last serving network node of a UE.

The details of one or more examples are set forth in the accompanying drawings and the descriptions below. Other features, objects, and advantages will be apparent from the descriptions and drawings, and from the claims.

DETAILED DESCRIPTION

The detailed description of the appended drawings is intended as a description of preferred embodiments of the present application and is not intended to represent the only form in which the present application may be practiced. It should be understood that the same or equivalent functions may be accomplished by different embodiments that are intended to be encompassed within the spirit and scope of the present application.

Reference will now be made in detail to some embodiments of the present application, examples of which are illustrated in the accompanying drawings. To facilitate understanding, embodiments are provided under specific network architecture and new service scenarios, such as 3rd Generation Partnership Project (3GPP) LTE and LTE advanced, 3GPP 5G NR, 5G-Advanced, 6G, and so on. It is contemplated that along with developments of network architectures and new service scenarios, all embodiments in the present application are also applicable to similar technical problems; and moreover, the terminologies recited in the present application may change, which should not affect the principle of the present application.

FIG. 1 illustrates a schematic diagram of a wireless communication system 100 in accordance with some embodiments of the present application. As shown in FIG. 1, the wireless communication system 100 includes UE 101, BS 102, and relay UE 103 for illustrative purpose. Although a specific number of UE(s), relay UE(s), and BS(s) are depicted in FIG. 1, it is contemplated that any number of UE(s), relay UE(s), and BS(s) may be included in the wireless communication system 100.

Due to a far distance between UE 101 and BS 102, these they communicate with each other via relay UE 103. UE 101 may be connected to relay UE 103 via a network interface, for example, a PC5 interface as specified in 3GPP standard documents. Relay UE 103 may be connected to BS 102 via a network interface, for example, a Uu interface as specified in 3GPP standard documents. Referring to FIG. 1, UE 101 is connected to relay UE 103 via a PC5 link, and relay UE 103 is connected to BS 102 via a Uu link. UE 101 may be a U2N remote UE. Relay UE 103 may be a U2N relay UE, which is a UE that provides functionality to support connectivity to the network for U2N remote UE(s).

In some embodiments of the present application, UE 101 or relay UE 103 may include computing devices, such as desktop computers, laptop computers, personal digital assistants (PDAs), tablet computers, smart televisions (e.g., televisions connected to the Internet), set-top boxes, game consoles, security systems (including security cameras), vehicle on-board computers, network devices (e.g., routers, switches, and modems), or the like.

In some further embodiments of the present application, UE 101 or relay UE 103 may include a portable wireless communication device, a smart phone, a cellular telephone, a flip phone, a device having a subscriber identity module, a personal computer, a selective call receiving circuitry, or any other device that is capable of sending and receiving communication signals on a wireless network.

In some other embodiments of the present application, UE 101 or relay UE 103 may include wearable devices, such as smart watches, fitness bands, optical head-mounted displays, or the like. Moreover, UE 101 or relay UE 103 may be referred to as a subscriber unit, a mobile, a mobile station, a user, a terminal, a mobile terminal, a wireless terminal, a fixed terminal, a subscriber station, a user terminal, or a device, or described using other terminology used in the art.

BS(s) 102 may be distributed over a geographic region. In certain embodiments of the present application, each of the BS(s) 102 may also be referred to as an access point, an access terminal, a base, a base unit, a macro cell, a Node-B, an evolved Node B (eNB), a gNB, a Home Node-B, a relay node, or a device, or described using other terminology used in the art. BS(s) 102 is generally a part of a radio access network that may include one or more controllers communicably coupled to one or more corresponding BS(s) 102.

In some embodiments of the present application, the wireless communication system 100 is compatible with the 5G NR of the 3GPP protocol, wherein BS(s) 102 transmit data using an OFDM modulation scheme on the downlink (DL), and UE(s) 101 (e.g., UE 101 or other similar UE) transmit data on the uplink (UL) using a Discrete Fourier Transform-Spread-Orthogonal Frequency Division Multiplexing (DFT-S-OFDM) or cyclic prefix-OFDM (CP-OFDM) scheme. More generally, however, the wireless communication system 100 may implement some other open or proprietary communication protocols, for example, WiMAX, among other protocols.

In some embodiments of the present application, BS(s) 102 may communicate using other communication protocols, such as the IEEE 1002.11 family of wireless communication protocols. Further, in some embodiments of the present application, BS(s) 102 may communicate over licensed spectrums, whereas in other embodiments, BS(s) 102 may communicate over unlicensed spectrums. The present application is not intended to be limited to the implementation of any particular wireless communication system architecture or protocol. In yet some embodiments of present application, BS(s) 102 may communicate with UE(s) 101 using the 3GPP 5G protocols.

UE(s) 101 may access BS(s) 102 to receive data packets from BS(s) 102 via a downlink channel and/or transmit data packets to BS(s) 102 via an uplink channel. In normal operation, since UE(s) 101 does not know when BS(s) 102 will transmit data packets to it, UE(s) 101 has to be awake all the time to monitor the downlink channel (e.g., a Physical Downlink Control Channel (PDCCH)) to get ready for receiving data packets from BS(s) 102. However, if UE(s) 101 keeps monitoring the downlink channel all the time even when there is no traffic between BS(s) 102 and UE(s) 101, it would result in significant power waste, which is problematic to a power limited UE or a power sensitive UE.

Some embodiments of the present application refer to switching from direct to indirect path. A gNB (e.g., BS 102 as shown in FIG. 1) can select a U2N Relay UE (e.g., relay UE 103 as shown in FIG. 1) in any RRC state, i.e., RRC_IDLE, RRC_INACTIVE, or RRC_CONNECTED, as a target U2N Relay UE for direct to indirect path switch. For service continuity of L2 U2N Remote UE, the following procedure is used, in case of a L2 U2N Remote UE (e.g., UE 101 as shown in FIG. 1) switching to an indirect path via the U2N Relay UE in RRC_CONNECTED.

Embodiments of the present application aim to solve issues of an inter-gNB path switching in a L2 U2N relay case, e.g., in a use case of switching an inter-gNB direct or indirect path to an indirect path. For example, some embodiments of the present application study a mechanism for a case in which a remote UE is switched to a relay UE in an RRC idle or inactive state. Some embodiments of the present application study a case that a BS does not transit a relay UE in an RRC idle or inactive state to an RRC connected state before transmitting a handover request acknowledge message. Some further embodiments of the present application study a case that a BS does not transit a relay UE in an RRC idle or inactive state to an RRC connected state before transmitting a handover request acknowledge message, but the BS may transit the relay UE in an RRC idle or inactive state to an RRC connected state before a UE performs a path switching procedure. Some other embodiments of the present application study a case that a BS transits a relay UE in an RRC idle or inactive state to an RRC connected state before transmitting a handover request acknowledge message.

More details will be illustrated in the following text in combination with the appended drawings. Persons skilled in the art should well know that the wording “a/the first,” “a/the second” and “a/the third” etc. are only used for clear description, and should not be deemed as any substantial limitation, e.g., sequence limitation.

FIG. 2 illustrates an exemplary flow chart for receiving a handover request message in accordance with some embodiments of the present application. The exemplary flow chart 200 may be performed by a target network node (e.g., a target BS). Specific examples of exemplary flow chart 200 are described in embodiments of FIGS. 5-8 as follows. Although described with respect to a target network node, it should be understood that other devices may be configured to perform a method similar to that of FIG. 2. Details described in all other embodiments of the present application (for example, all details regarding switching to a relay UE in an RRC idle or inactive state) are applicable for the exemplary flow chart 200. Moreover, details described in the exemplary flow chart 200 are applicable for all the embodiments of FIGS. 3-10.

In the exemplary flow chart 200 as shown in FIG. 2, in operation 201, a target network node (e.g., target BS 504, target BS 604, target BS 704, or target BS 804 as shown in any of FIGS. 5-8) receives a handover request message from a source network node (e.g., source BS 502, source BS 602, source BS 702, or source BS 902 as shown in any of FIGS. 5-8). The handover request message includes ID information of a candidate relay UE for a UE (e.g., UE 501, UE 601, UE 701, or UE 801 as shown in any of FIGS. 5-8). In operation 202, the target network node transmits a response message to the source network node. The response message includes at least one of: a handover request acknowledge message including ID information of a target relay UE (e.g., relay UE 503, relay UE 603, relay UE 703, or relay UE 803 as shown in any of FIGS. 5-8) for the UE; or a message to cancel a resource preparation of path switching for the UE.

In some embodiments, the handover request acknowledge message further includes an RRC state of the target relay UE (e.g., relay UE 503, relay UE 603, relay UE 703, or relay UE 803 as shown in any of FIGS. 5-8). In an embodiment, the RRC state of the target relay UE is an RRC connected state or an RRC non-connected state. For example, the RRC non-connected state may include an RRC idle state and/or an RRC inactive state.

In some embodiments, the message to cancel the resource preparation is a handover preparation failure message. In an embodiment, the message to cancel the resource preparation includes a failure cause associated with the target relay UE. For example, the failure cause includes at least one of: the target relay UE being high load; the target relay UE being overloaded; the target relay UE being not reached; or the target relay UE being not found. A specific example is described in the embodiments of FIG. 6 as follows.

In some embodiments, the target network node determines whether the target relay UE is in an RRC connected state or an RRC non-connected state; and transmits a paging message to the target relay UE, in response to determining that the target relay UE is in the RRC non-connected state. In an embodiment, the RRC non-connected state includes an RRC idle state and/or an RRC inactive state. Specific examples are described in the embodiments of FIGS. 6-8 as follows.

In some embodiments, the target network node transmits the handover request acknowledge message to the source network node before transiting the target relay UE to the RRC connected state; and transmits the message to cancel the resource preparation to the source network node, in response to failing to reaching the target relay UE by the paging message. A specific example is described in the embodiments of FIG. 6 as follows.

In some embodiments, the target network node transmits the handover request acknowledge message to the source network node, in response to the target relay UE entering into an RRC connected state after a reception of the paging message. Specific examples are described in the embodiments of FIGS. 7 and 8 as follows.

In some embodiments, the target network node transmits “a message (named as “1st message” for simplicity) for transiting the target relay UE from the RRC non-connected state to the RRC connected state” to an AMF (e.g., AMF 705 as shown in FIG. 7), in response to determining that the target relay UE is in the RRC non-connected state. The target network node receives “a message (named as “2nd message” for simplicity) for triggering a RAN paging operation” from the AMF. Then, the target network node transmits the paging message to the target relay UE. A specific example is described in the embodiments of FIG. 7 as follows.

In an embodiment, the 1st message includes: the ID information of the target relay UE; and/or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state. For instance, the ID information of the target relay UE is a source Layer-2 ID. In an embodiment, the 2nd message includes AS layer ID information of the target relay UE. For example, the AS layer ID information is a NG-5G-S-TMSI. In an embodiment, an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE” is maintained in the AMF. For instance, the AS layer ID information of the target relay UE is identified by the AMF based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, the target network node transmits “a message (named as “3rd message” for simplicity) for transiting the target relay UE from the RRC non-connected state to the RRC connected state” to a set of neighbour network nodes, in response to determining that the target relay UE is in the RRC non-connected state. The target network node receives “a message (named as “4th message” for simplicity) for triggering a RAN paging operation” from a last serving network node of the UE. The set of neighbour network nodes includes the last serving network node of the UE. Then, the target network node transmits a paging message to the target relay UE. The last serving network node of the UE may be the last serving gNB, which configures the connected UE to an inactive state. The last serving gNB will keep the context of the UE. A specific example is described in the embodiments of FIG. 8 as follows.

In an embodiment, the 3rd message includes: the ID information of the target relay UE; and/or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state. For instance, the ID information of the target relay UE is a source Layer-2 ID. In an embodiment, the 4th message and/or “the paging message transmitted by the target network node” includes AS layer ID information of the target relay UE. For instance, the AS layer ID information is an I-RNTI or a short I-RNTI. The information element (IE) “Short I-RNTI-Value” may be used to identify the suspended UE context of a UE in an RRC inactive state using fewer bits compared to the IE “I-RNTI-Value”.

In some embodiments, in response to the 4th message including the AS layer ID information of the target relay UE, an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE” is maintained in the last serving network node of the UE. The AS layer ID information of the target relay UE may be identified by the last serving network node of the UE based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, in response to the 4th message not including the AS layer ID information of the target relay UE, the target network node maintains an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE”; and identifies the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, the paging message includes: a source Layer-2 ID of the target relay UE, or AS layer ID information of the target relay UE. For instance, the AS layer ID information is a NG-5G-S-TMSI or an I-RNTI.

In some embodiments, the target network node maintains an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE”, and identifies the AS layer ID information of the target relay UE on its own based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, the target network node receives the source Layer-2 ID of the target relay UE from a serving cell of the target relay UE. Specific examples are described in the embodiments of FIGS. 7 and 8 as follows.

FIG. 3 illustrates an exemplary flow chart for transmitting a message for triggering a RAN paging operation in accordance with some embodiments of the present application. The exemplary flow chart 300 may be performed by an AMF. A specific example of exemplary flow chart 300 is described in embodiments of FIG. 7 as follows. Although described with respect to an AMF, it should be understood that other devices may be configured to perform a method similar to that of FIG. 3. Details described in all other embodiments of the present application are applicable for the exemplary flow chart 300. Moreover, details described in the exemplary flow chart 300 are applicable for all the embodiments of FIGS. 2 and 4-10.

In the exemplary flow chart 300 as shown in FIG. 3, in operation 301, an AMF (e.g., AMF 705 as shown in FIG. 7) receives “a message for transiting a target relay UE (e.g., relay UE 703 as shown in FIG. 7) from an RRC non-connected state to an RRC connected state” from a target network node (e.g., target BS 704 as shown in FIG. 7). In operation 302, the AMF transmits “a message for triggering a RAN paging operation to the target relay UE” to the target network node.

In some embodiments, the RRC non-connected state includes an RRC idle state and/or an RRC inactive state.

In some embodiments, the message for transiting the target relay UE includes: ID information of the target relay UE; and/or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state. In an embodiment, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, the message for triggering the RAN paging operation includes AS layer ID information of the target relay UE. In an embodiment, the AS layer ID information is a NG-5G-S-TMSI.

In some embodiments, the AMF maintains an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE”, and identifies the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, the AMF receives the source Layer-2 ID of the target relay UE from a serving cell of the target relay UE.

FIG. 4 illustrates a further exemplary flow chart for transmitting a message for triggering a RAN paging operation in accordance with some embodiments of the present application. The exemplary flow chart 400 may be performed by a last serving network node of a UE, i.e., a previous serving network node which served the UE before the UE switching to the current serving network node. The last serving network node may be the last serving gNB, which configures the connected UE to an inactive state. The last serving gNB will keep the context of the UE. A specific example of exemplary flow chart 400 is described in embodiments of FIG. 8 as follows. Although described with respect to a last serving network node of a UE, it should be understood that other devices may be configured to perform a method similar to that of FIG. 4. Details described in all other embodiments of the present application are applicable for the exemplary flow chart 400. Moreover, details described in the exemplary flow chart 400 are applicable for all the embodiments of FIGS. 2, 3, and 5-10.

In the exemplary flow chart 400 as shown in FIG. 4, in operation 401, a last serving network node (e.g., neighbour BS 805 as shown in FIG. 8) of a UE (e.g., UE 801 as shown in FIG. 8) receives “a message for transiting a target relay UE (e.g., relay UE 803 as shown in FIG. 8) from an RRC non-connected state to an RRC connected state” from a target network node (e.g., target BS 804 as shown in FIG. 8). In operation 402, the last serving network node of the UE transmits “a message for triggering a RAN paging operation to the target relay UE” to the target network node.

In some embodiments, the message for transiting the target relay UE includes: the ID information of the target relay UE; and/or a request to transit the target relay UE from the RRC non-connected state to the RRC connected state. In an embodiment, the ID information of the target relay UE is a source Layer-2 ID.

In some embodiments, the message for triggering the RAN paging operation includes AS layer ID information of the target relay UE. In an embodiment, the AS layer ID information of the target relay UE is an I-RNTI or a short I-RNTI.

In some embodiments, in response to the message for triggering the RAN paging operation including the AS layer ID information of the target relay UE, the last serving network node maintains an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE”, and identifies the AS layer ID information of the target relay UE based on the source Layer-2 ID of the target relay UE and the association.

In some embodiments, in response to the message for triggering the RAN paging operation not including the AS layer ID information of the target relay UE, an association between “a source Layer-2 ID of the target relay UE” and “AS layer ID information of the target relay UE” is maintained in the target network node; and the AS layer ID information of the target relay UE is identified by the target network node based on the source Layer-2 ID of the target relay UE and the association.

FIG. 5 illustrates a flow chart of an exemplary procedure 500 of wireless communications in accordance with some embodiments of the present disclosure. The exemplary procedure 500 refers to a procedure for Inter-gNB path switching from a direct or indirect path to an indirect path. In the exemplary procedure 500, a BS does not transit a relay UE in an RRC idle or inactive state to an RRC connected state before transmitting a handover request acknowledge message. Details described in all other embodiments of the present disclosure are applicable for the embodiments shown in FIG. 5.

Referring to FIG. 5, UE 501, target BS 504, and relay UE 503 may function as UE 101, BS 102, and relay UE 103 as shown in FIG. 1, respectively. Source BS 502 may be one source BS not shown in FIG. 1. In particular, following steps are performed in the exemplary procedure 500.

FIG. 6 illustrates a flow chart of an exemplary procedure 600 of wireless communications in accordance with some embodiments of the present disclosure. The exemplary procedure 600 also refers to a procedure for Inter-gNB path switching from a direct or indirect path to an indirect path. In the exemplary procedure 600, a BS does not transit a relay UE in an RRC idle or inactive state to an RRC connected state before transmitting a handover request acknowledge message, but the BS may transit the relay UE in an RRC idle or inactive state to an RRC connected state before a UE performs a path switching procedure. Details described in all other embodiments of the present disclosure are applicable for the embodiments shown in FIG. 6.

Referring to FIG. 6, UE 601, target BS 604, and relay UE 603 may function as UE 101, BS 102, and relay UE 103 as shown in FIG. 1, respectively. Source BS 602 may be one source BS not shown in FIG. 1. In particular, following steps are performed in the exemplary procedure 600.

FIG. 7 illustrates a flow chart of an exemplary procedure 700 of wireless communications in accordance with some embodiments of the present disclosure. Exemplary procedure 700 also refers to a procedure for Inter-gNB path switching from a direct or indirect path to an indirect path. In the exemplary procedure 700, a BS transits a relay UE in an RRC idle state to an RRC connected state before transmitting a handover request acknowledge message. Details described in all other embodiments of the present disclosure are applicable for the embodiments shown in FIG. 7.

Referring to FIG. 7, UE 701, target BS 704, and relay UE 703 may function as UE 101, BS 102, and relay UE 103 as shown in FIG. 1, respectively. Source BS 702 may be one source BS not shown in FIG. 1. In particular, following steps are performed in the exemplary procedure 700.

FIG. 8 illustrates a flow chart of an exemplary procedure 800 of wireless communications in accordance with some embodiments of the present disclosure. Exemplary procedure 800 also refers to a procedure for Inter-gNB path switching from a direct or indirect path to an indirect path. In the exemplary procedure 800, a BS transits a relay UE in an RRC inactive state to an RRC connected state before transmitting a handover request acknowledge message. Details described in all other embodiments of the present disclosure are applicable for the embodiments shown in FIG. 8.

Referring to FIG. 8, UE 801, target BS 804, and relay UE 803 may function as UE 101, BS 102, and relay UE 103 as shown in FIG. 1, respectively. Source BS 802 may be one source BS not shown in FIG. 1. In particular, following steps are performed in the exemplary procedure 800.

It should be appreciated by persons skilled in the art that the sequence of the operations in any of exemplary procedures 200 to 800 in FIGS. 2-8 may be changed and some of the operations in any of exemplary procedures 200 to 800 in FIGS. 2-8 may be eliminated or modified, without departing from the spirit and scope of the disclosure.

Some embodiments of the present application also provide a wireless communication apparatus for a L2 U2N relay case. For example, FIG. 9 illustrates an exemplary block diagram of an apparatus 900 for a L2 U2N relay case in accordance with some embodiments of the present application.

As shown in FIG. 9, the apparatus 900 may include at least one non-transitory computer-readable medium 902, at least one receiving circuitry 904, at least one transmitting circuitry 906, and at least one processor 908 coupled to the non-transitory computer-readable medium 902, the receiving circuitry 904 and the transmitting circuitry 906. The at least one processor 908 may be a CPU, a DSP, a microprocessor etc. The apparatus 900 may be a network apparatus (e.g., a target BS, an AMF, or a last serving BS of a UE) configured to perform a method illustrated in the above or the like.

Although in this figure, elements such as the at least one processor 908, receiving circuitry 904, and transmitting circuitry 906 are described in the singular, the plural is contemplated unless a limitation to the singular is explicitly stated. In some embodiments of the present application, the receiving circuitry 904 and the transmitting circuitry 906 can be combined into a single device, such as a transceiver. In certain embodiments of the present application, the apparatus 900 may further include an input device, a memory, and/or other components.

In some embodiments of the present application, the non-transitory computer-readable medium 902 may have stored thereon computer-executable instructions to cause a processor to implement the method with respect to a network apparatus (e.g., a target BS, an AMF, or a last serving BS of a UE) as described above. For example, the computer-executable instructions, when executed, cause the processor 908 interacting with receiving circuitry 904 and transmitting circuitry 906, so as to perform the steps with respect to a network apparatus (e.g., a target BS, an AMF, or a last serving BS of a UE) as illustrated above.

FIG. 10 illustrates a further exemplary block diagram of an apparatus 1000 for a L2 U2N relay case in accordance with some embodiments of the present application.

Referring to FIG. 10, the apparatus 1000, for example a BS or a UE, may include at least one processor 1002 and at least one transceiver 1004 coupled to the at least one processor 1002. The transceiver 1004 may include at least one separate receiving circuitry 1006 and transmitting circuitry 1008, or at least one integrated receiving circuitry 1006 and transmitting circuitry 1008. The at least one processor 1002 may be a CPU, a DSP, a microprocessor etc.

According to some embodiments of the present application, when the apparatus 1000 is a target BS, the processor 1002 is configured: to receive a handover request message via the transceiver from a source network node, wherein the handover request message includes ID information of a candidate relay UE for a UE; and to transmit a response message via the transceiver to the source network node, wherein the response message includes at least one of: a handover request acknowledge message including ID information of a target relay UE for the UE; or a message to cancel a resource preparation of path switching for the UE.

According to some embodiments of the present application, when the apparatus 1000 is an AMF, the processor 1002 is configured: to receive a message for transiting a target relay UE from an RRC non-connected state to an RRC connected state via the transceiver from a target network node; and to transmit a message for triggering a RAN paging operation to the target relay UE via the transceiver to the target network node.

According to some other embodiments of the present application, when the apparatus 1000 is a last serving network node of a UE, the processor 1002 is configured: to receive a message for transiting a target relay UE from an RRC non-connected state to an RRC connected state via the transceiver from a target network node; and to transmit a message for triggering a RAN paging operation to the target relay UE via the transceiver to the target network node.

The method(s) of the present disclosure can be implemented on a programmed processor. However, controllers, flowcharts, and modules may also be implemented on a general purpose or special purpose computer, a programmed microprocessor or microcontroller and peripheral integrated circuit elements, an integrated circuit, a hardware electronic or logic circuit such as a discrete element circuit, a programmable logic device, or the like. In general, any device that has a finite state machine capable of implementing the flowcharts shown in the figures may be used to implement the processing functions of the present disclosure.

While this disclosure has been described with specific embodiments thereof, it is evident that many alternatives, modifications, and variations may be apparent to those skilled in the art. For example, various components of the embodiments may be interchanged, added, or substituted in the other embodiments. Also, all of the elements of each figure are not necessary for operation of the disclosed embodiments. For example, those having ordinary skills in the art would be enabled to make and use the teachings of the disclosure by simply employing the elements of the independent claims. Accordingly, embodiments of the disclosure as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the spirit and scope of the disclosure.

In this document, the terms “includes,” “including,” or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. An element proceeded by “a,” “an,” or the like does not, without more constraints, preclude the existence of additional identical elements in the process, method, article, or apparatus that includes the element. Also, the term “another” is defined as at least a second or more. The term “having” and the like, as used herein, are defined as “including”.