WO2021179146A1

WO2021179146A1 - Methods, devices, and medium for communication

Info

Publication number: WO2021179146A1
Application number: PCT/CN2020/078483
Authority: WO
Inventors: Gang Wang
Original assignee: Nec Corporation
Priority date: 2020-03-09
Filing date: 2020-03-09
Publication date: 2021-09-16

Abstract

Embodiments of the present disclosure relate to methods, devices, and medium for communication. According to embodiments of the present disclosure, RLC based data forwarding is introduced. The RLC channels are released based on the BAP address of the network device which is to be handed over. By the present disclosure, it remarkably optimized the IAB node migration to enable the IAB migration intra-Donor CU.

Description

METHODS, DEVICES, AND MEDIUM FOR COMMUNICATION

TECHNICAL FIELD

Embodiments of the present disclosure generally relate to the field of telecommunication, and in particular, to methods, devices, and medium for communication.

BACKGROUND

Communication technologies have been developed. For example, due to expected larger bandwidth available for new radio (NR) systems compared to long-term evolution (LTE) systems, it creates an opportunity to develop and deploy an integrated access backhaul (IAB) architecture for the fifth generation (5G) cellular networks in which the same infrastructure and spectral resources will be used for both access and backhaul. This may allow easier deployment of a dense network of NR cells in a more integrated manner by building upon many of control and data channels/procedures defined for providing access to terminal devices.

SUMMARY

In general, example embodiments of the present disclosure provide a solution of handover for network devices.

In a first aspect, there is provided a method for communication. The method comprises determining, at a first network device, to handover a second network device from a third network device to a fourth network device based on a measurement of channel quality received from the second network device. The method further comprises transmitting a context setup request to the fourth network device, the context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and the second network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device. The method also comprises transmitting, to the third network device or a fifth network device, a node release request indicating a backhaul adaption protocol address of the second network device. The method yet comprises in response to receiving a context setup response from the fourth network device, transmitting radio resource control configuration of the fourth network device to the second network device for preparing the handover.

In a second aspect, there is provided a method for communication. The method comprises transmitting, at a second network device, a measurement of channel quality to a first network device for handover from a third network device to a fourth network device. The method also comprises receiving radio resource control configuration of the fourth network device from the first network device. The method further comprises updating information of routing and bearer mapping between the second network device and the fourth network device based on the radio resource control configuration.

In a third aspect, there is provided a method for communication. The method comprises receiving, at a third network device and from a first network device, a node release request indicating a backhaul adaption protocol address of a second network device which is to be handed over from the third network device to a fourth network device. The method also comprises releasing a second list of radio link control channels between the second network device and the third network device based on the node release information.

In a fourth aspect, there is provided a method for communication. The method comprises receiving, at a fourth network device and from a first network device, a context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and a second network device which is to be handed over from the a third network device to the fourth network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device. The method also comprises establishing the first list of radio link control channels. The method further comprises transmitting a context setup response to the first network device.

In a fifth aspect, there is provided a method for communication. The method comprise receiving, at a fifth network device and from a first network device, node release request indicating a backhaul adaption protocol address of a second network device which is to be handed over from a third network device to a fourth network device, the fifth network device being an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device. The method also comprises releasing a second list of radio link control channels between the second network device and the third network device based on the node release information. The method further comprises transmitting to the first network device a response to the node release request.

In a sixth aspect, there is provided a first network device. The first network device comprises a processing unit; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the first network device to perform determining to handover a second network device from a third network device to a fourth network device based on a measurement of channel quality received from the second network device; transmitting a context setup request to the fourth network device, the context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and the second network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device; transmitting, to the third network device, a node release request indicating a backhaul adaption protocol address of the second network device; and in response to receiving a context setup response from the fourth network device, transmitting radio resource control configuration of the fourth network device to the second network device for preparing the handover.

In a seventh aspect, there is provided a second network device. The second network device comprises a processing unit; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the second network device to perform: transmitting, at a second network device, a measurement of channel quality to a first network device for handover from a third network device to a fourth network device; receiving radio resource control configuration of the fourth network device from the first network device; and updating information of routing and bearer mapping between the second network device and the fourth network device based on the radio resource control configuration.

In an eighth aspect, there is provided a third network device. The third network device comprises a processing unit; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the third network device to perform: receiving, at a third network device and from a first network device, a node release request indicating a backhaul adaption protocol address of a second network device which is to be handed over from the third network device to a fourth network device; and releasing a second list of radio link control channels between the second network device and the third network device based on the node release information.

In a ninth aspect, there is provided a fourth network device. The fourth network device comprises a processing unit; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the fourth network device to perform: receiving, at a fourth network device and from a first network device, a context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and a second network device which is to be handed over from the a third network device to the fourth network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device; establishing the first list of radio link control channels; and transmitting a context setup response to the first network device.

In a tenth aspect, there is provided a fifth network device. The fifth network device comprises a processing unit; and a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the fifth network device to perform: receiving, at a fifth network device and from a first network device, node release request indicating a backhaul adaption protocol address of a second network device which is to be handed over from a third network device to a fourth network device, the fifth network device being an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device; releasing a second list of radio link control channels between the second network device and the third network device based on the node release information; and transmitting to the first network device a response to the node release request.

In an eleventh aspect, there is provided a computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any one of the first aspect, second aspect, third aspect, fourth aspect or fifth aspect.

Other features of the present disclosure will become easily comprehensible through the following description.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the more detailed description of some example embodiments of the present disclosure in the accompanying drawings, the above and other objects, features and advantages of the present disclosure will become more apparent, wherein:

Fig. 1 is a schematic diagram of a communication environment in which embodiments of the present disclosure can be implemented;

Fig. 2 is a signaling chart illustrating a process according to an embodiment of the present disclosure;

Fig. 3 is a flowchart of an example method in accordance with an embodiment of the present disclosure;

Fig. 4 is a flowchart of an example method in accordance with an embodiment of the present disclosure;

Fig. 5 is a flowchart of an example method in accordance with an embodiment of the present disclosure;

Fig. 6 is a flowchart of an example method in accordance with an embodiment of the present disclosure;

Fig. 7 is a flowchart of an example method in accordance with an embodiment of the present disclosure; and

Fig. 8 is a simplified block diagram of a device that is suitable for implementing embodiments of the present disclosure.

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

DETAILED DESCRIPTION

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

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

As used herein, the term “network device” refers to a device which is capable of providing or hosting a cell or coverage where terminal devices can communicate. Examples of a network device include, but not limited to, a Node B (NodeB or NB) , an Evolved NodeB (eNodeB or eNB) , a NodeB in new radio access (gNB) a Remote Radio Unit (RRU) , a radio head (RH) , a remote radio head (RRH) , a low power node such as a femto node, a pico node, a satellite network device, an aircraft network device, and the like. For the purpose of discussion, in the following, some example embodiments will be described with reference to eNB as examples of the network device.

As used herein, the term “terminal device” refers to any device having wireless or wired communication capabilities. Examples of the terminal device include, but not limited to, user equipment (UE) , personal computers, desktops, mobile phones, cellular phones, smart phones, personal digital assistants (PDAs) , portable computers, tablets, wearable devices, internet of things (IoT) devices, Internet of Everything (IoE) devices, machine type communication (MTC) devices, device on vehicle for V2X communication where X means pedestrian, vehicle, or infrastructure/network, or image capture devices such as digital cameras, gaming devices, music storage and playback appliances, or Internet appliances enabling wireless or wired Internet access and browsing and the like. In the following description, the terms “terminal device” , “communication device” , “terminal” , “user equipment” and “UE” may be used interchangeably.

In one embodiment, the terminal device may be connected with a first network device and a second network device. One of the first network device and the second network device may be a master node and the other one may be a secondary node. The first network device and the second network device may use different radio access technologies (RATs) . In one embodiment, the first network device may be a first RAT device and the second network device may be a second RAT device. In one embodiment, the first RAT device is eNB and the second RAT device is gNB. Information related with different RATs may be transmitted to the terminal device from at least one of the first network device and the second network device. In one embodiment, first information may be transmitted to the terminal device from the first network device and second information may be transmitted to the terminal device from the second network device directly or via the first network device. In one embodiment, information related with configuration for the terminal device configured by the second network device may be transmitted from the second network device via the first network device. Information related with reconfiguration for the terminal device configured by the second network device may be transmitted to the terminal device from the second network device directly or via the first network device.

Communications discussed herein may use conform to any suitable standards including, but not limited to, New Radio Access (NR) , Long Term Evolution (LTE) , LTE-Evolution, LTE-Advanced (LTE-A) , Wideband Code Division Multiple Access (WCDMA) , Code Division Multiple Access (CDMA) , cdma2000, and Global System for Mobile Communications (GSM) and the like. Furthermore, the communications may be performed according to any generation communication protocols either currently known or to be developed in the future. Examples of the communication protocols include, but not limited to, the first generation (1G) , the second generation (2G) , 2.5G, 2.85G, the third generation (3G) , the fourth generation (4G) , 4.5G, the fifth generation (5G) communication protocols. The techniques described herein may be used for the wireless networks and radio technologies mentioned above as well as other wireless networks and radio technologies.

As used herein, the singular forms “a” , “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. The term “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” 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. ” The terms “first, ” “second, ” and the like may refer to different or same objects. Other definitions, explicit and implicit, may be included below.

In some examples, values, procedures, or apparatus are referred to as “best, ” “lowest, ” “highest, ” “minimum, ” “maximum, ” or the like. It will be appreciated that such descriptions are intended to indicate that a selection among many used functional alternatives can be made, and such selections need not be better, smaller, higher, or otherwise preferable to other selections.

As mentioned above, the IAB technology has been proposed. In an IAB environment, there may be an IAB donor (for example, donor control unit, Donor CU) which is a 5G base station and one or more IAB nodes which is 5G relay station. In NR IAB, mobility for IAB has been introduced. So, the handover of IAB should be addressed. The IAB node usually doesn’t have radio resource control (RRC) or packet data convergence protocol (PDCP) entity, so the RRC function should be delivered to Donor CU to handle the configuration and command. According to conventional technologies, data is forwarded in Xn interface between a source network device and a target network device. However, in IAB, there is no interface between a source IAB and a target IAB. Thus, how to forward the data during the handover should be resolved.

Generally, for bearer mapping, a backhaul adaption protocol (BAP) entity may perform mapping to egress logical channel based on a backhaul radio link channel (RLC) channel mapping configuration. Regarding routing, the BAP entity may perform routing based on the backhaul (BH) routing configuration. Each entry of the BH routing configuration may contain a BAP routing identity which includes one or more of: a BAP address, a BAP path identity, and a Next Hop BAP Address.

In some conventional technologies, inter-donor IAB-node migration has been introduced, which increases robustness and allows for more refined load-balancing and topology management. Reduction of service interruption time caused by IAB-node migration and BH RLF recovery improves network performance and allows network deployments to undergo more frequent topology changes, and provides stable backhaul performance. However, latency problem needs to be addressed.

Further, some other issues are still needed to be addressed, for example, how to perform data forwarding, how to perform group handover, how to quickly ensure the uplink/downlink data transmission, given the long propagation delay of multiple-hop IAB architecture.

In order to solve at least part of the aforementioned problems, new technologies in handover are needed. According to embodiments of the present disclosure, RLC based data forwarding is introduced. The RCL channels are released based on the BAP address of the network device which is to be handed over. By the present disclosure, it remarkably optimized the IAB node migration to enable the IAB migration intra-Donor CU.

Fig. 1 illustrates a schematic diagram of a communication system in which embodiments of the present disclosure can be implemented. The communication system 100, which is a part of a communication network, comprises a network device 110-1, a network device 110-2, a network device 110-3, a network device 110-4, a network device 110-2, a network device 110-5, ..., a network device 110-N, which can be collectively referred to as “network device (s) 110. ” The network devices 110 may comprise one or more donor network devices and one or more IAB nodes. Only for the purpose of illustrations, the network device 110-1 which may also be called the first network device 110-1 may be regarded as the donor network device/IAB-donor. The network device 110-2 (i.e., the second network device) , the network device 110-3 (i.e., the third network device) , the network device 110-4 (i.e., the fourth network device) , the network device 110-5 (i.e., the fifth network device) , the network device 110-6 (i.e., the sixth network device) may be regarded as IAB nodes.

As shown in Fig. 1, the fifth network device 110-5 is an intermedia network device between the first network device 110-1 and the third network device 110-3. The fifth network device 110-5 may also be an intermedia network device between the first network device 110-1 and the fourth network device 110-4. According to the architecture shown in Fig. 1, the sixth network device 110-6 may be a child network device/node of the second network device 110-2. Similarly, the fifth network device 110-5 may be a parent network device/node of the third network device 110-3 and the fourth network device 110-4. It should be noted that the architecture in Fig. 1 is only an example not limitation. The network devices 110 may communicate with each other via backhauls.

The communication system 100 further comprises a terminal device 120-1, a terminal device 120-12, ..., a terminal device 120-M, which can be collectively referred to as “terminal device (s) 120. ” In the communication system 100, the network devices 110 and the terminal devices 120 can communicate data and control information to each other. The numbers of terminal devices and network devices shown in Fig. 1 are given for the purpose of illustration without suggesting any limitations.

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

Embodiments of the present disclosure will be described in detail below. Reference is first made to Fig. 2, which shows a signaling chart illustrating interactions 200 among network devices according to some example embodiments of the present disclosure. Only for the purpose of discussion, the process 200 will be described with reference to Fig. 1. The process 200 may involve the first network device 110-1, the second network device 110-2, the third network device 110-3, the fourth network device 110-4, and the fifth network device 110-5 in Fig. 1.

The second network device 110-2 performs 2005 measurements of channel qualities. For example, the second network device 110-2 may measure a backhaul 130-2 between the second network device 110-2 and the third network device 110-3. Alternatively, a backhaul 130-1 between the second network device 110-2 and the fourth network device 110-4 may also be measured by the second network device 110-2. In some embodiments, the second network device 110-2 may measure power of signals received on the backhauls.

The second network device 110-2 transmits 2010 the measurement to the first network device 110-1. The first network device 110-1 determines 2015 to handover the second network device 110-2 from the third network device 110-3 to the fourth network device 110-4 based on the received measurement.

The first network device 110-1 transmits 2020 a context setup request to the fourth network device 110-4. The context setup request may be transmitted via F1 application (F1-AP) signaling. Alternatively, the context setup request may be transmitted via BAP signaling. The context setup request at least indicates a first list of RCL channels to be established between the second network device 110-2 and the fourth network device 110-4. The first list of the RCL channels correspond to a second list of RLC channels in the backhaul 130-2 between the second network device 110-2 and the third network device 110-3. In some embodiments, the context setup request may comprise security context information. Alternatively, UE capability information may also be included in the context setup request. In other embodiments, the context setup request may indicate a list of bearers.

The fourth network device 110-4 establishes 2025 the first list of RLC channels between the second network device 110-2 and the fourth network device 110-4 based on the context setup request. In some embodiments, the context setup request may be transmitted via BAP signaling. In this situation, the context setup request may indicate to map the established RLC channels to existing RCL channels in backhaul 130-3 (for example, default RCL channels) between the fourth network device 110-4 and the fifth network device 110-5. The first network device 110-1 may also transmit 2030 a further context setup request to the fifth network device 110-5. The further context setup request may indicate to map the existing RCL channels in the backhaul 130-3 to further existing RCL channels in backhaul 130-4. The further context setup request may not be valid until the fourth network device 110-4 transmits 2035 a response to the context setup request to the first network device 110-1. Since the context setup request is transmitted via the BAP signaling, the response may also be received by the fifth network device 110-5 to make the further context setup request valid. After receiving the response, the fifth network device 110-5 may map the existing RCL channels in the backhaul 130-3 to further existing RCL channels in backhaul 130-4. In this way, latency of bearer mapping has been reduced.

In other embodiments, the further context setup request may indicate to establish RCL channels in the backhauls 130-3 and 130-4. The number of established RCL channels may correspond to the number of channels in the first list. Similarly, the further context setup request may not be valid until the fourth network device 110-4 transmits 2035 the response to the context setup request to the first network device 110-1. Since the context setup request is transmitted via the BAP signaling, the response may also be received by the fifth network device 110-5 to make the further context setup request valid. After receiving the response, the fifth network device 110-5 may establish RCL channels in the backhauls 130-3 and 130-4 based on the further context setup request. The fifth network device 110-5 may transmit 2040 the further response to the context setup request.

Alternatively, the context setup request may be transmitted via F1 AP signaling. As discussed above, the context setup request may indicate to map the established RLC channels to existing RCL channels in backhaul 130-3. In this situation, after the fourth network device 110-4 transmits 2035 the response, the first network device 110-1 may transmit the further context setup request to map between the backhaul 130-5 and the backhaul 130-4.

In some embodiments, after receiving the context setup response from the fourth network device 110-4, the first network device 110-1 may transmit RRC configuration to the second network device 110-2. The RRC configuration may comprise BAP configuration of the fourth network device 110-4. The second network device 110-2 may update 2050 the routing and bearer mapping configuration between the second network device 110-2 and the fourth network device 110-3. In some embodiments, if the second network device 110-2 has a child node (for example, the sixth network device 110-6) , the second network device 110-2 may update the BAP configuration of the sixth network device 110-6. For example, the BAP configuration received from the first network device 110-1 may be transmitted to the sixth network device 110-6 to update the routing and bearer mapping at the sixth network device 110-6. Alternatively, the first network device 110-1 may transmit the RRC configuration to the sixth network device 110-6 to update the BAP configuration of the sixth network device 110-6.

In some embodiments, the first network device 110-1 may preconfigure the establishment of the RLC channels. For example, the first network device 110-1 may configure the fifth network device 110-1 to establish the same number of RLC channels in the backhauls 130-3 and 130-4 which corresponds to the RLC channels in the backhaul 130-1. Alternatively, when the backhaul 130-1 is established, all the RCL channels in the backhaul 130-1 are configured to default RLC channels in the backhaul 130-3. In some embodiments, the first network device 110-1 may further transmit and explicit bearer mapping configuration.

The first network device 110-1 transmits 2055 node release request to the third network device 110-3 to release the second list of RLC channels between the third network deice 110-3 and the second network device 110-2. The node release request at least indicates the BAP address of the second network device 110-2. The third network device 110-3 releases 2060 the second list of RLC channels of the second network device 110-2 based on the BAP address in the node release information. In this way, the F1AP signaling in the IAB backhauls can be saved. The third network device 110-3 transmits 2065 a response to the node release information.

In some embodiments, if each radio control channel between the second network device 110-2 and the third network device 110-3 corresponds to each radio control channel between the third network device 110-3 and the fifth network device 110-5 (i.e., 1: 1 mapping) , the first network device 110-1 may transmit 2070 the node release request to the fifth network device 110-5 to release the second list of RLC channels between the third network deice 110-3 and the second network device 110-2. For example, if the RLC channels in the backhaul 130-2 and the backhaul 130-5 are one-to-one mapped, then the second network device 110-2 is visible to the fifth network device 110-5. The node release request indicating the BAP address of the second network device 110-2 can be transmitted to the fifth network device 110-5 in order to release all RLC channels in the backhaul 130-2. The fifth network device 110-5 may transmit 2075 a response to the node release request to the first network device 110-1.

In other embodiments, in case of multi-to-one mapping in backhaul 130-5, the RLC channels from the backhaul 130-2 and the backhaul 130-6 may aggregated in the backhaul. So, in case the RLC channels in the backhaul 130-2 channels are released, the third network device 110-3 may decrease a bit rate based on the bit rate on the released second list of RLC channels until receiving further explicit configuration from the first network device 110-1 indicating an updated bit rate. For example, the third network device 110-3 may decrease maximum bit rate (MBR) . Alternatively, or in addition, the third network device 110-3 may decrease guaranteed bit rate (GBR) .

As shown in Fig. 2, the third network device 110-3 may transmit 2080 a RLC sequence number status transfer information of radio link control channel between the third network device 110-3 and the fourth network device 110-4 to the first network device 110-1 or the fifth network device 110-5. The first network device 110-1 may transmit 2085 the RLC sequence number status transfer information to the fourth network device 110-4.

In some embodiments, in order to perform data forwarding, the first network device 110-1 may trigger the user plane tunnel establishment. In some embodiments, the date may be forwarded via the fifth network device 110-5. In this situation, the first network device 110-1 may transmit 2090 a first tunnel setup request to the third network device 110-3. The first tunnel setup request may comprise one or more of: the BAP address of the fourth network device 110-4 or the fifth network device 110-5, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The third network device 110-3 may establish the data tunnel between the third network device 110-3 and the fifth network device 110-5 based on the first tunnel setup request and transmits 2095 a response to the first tunnel setup request.

Further, the first network device 110-1 may transmit 2100 a second tunnel setup request to the fourth network device 110-4. The second tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The fourth network device 110-4 may establish the data tunnel between the fourth network device 110-4 and the fifth network device 110-5 based on the second tunnel setup request and transmits 2105 a response to the second tunnel setup request.

In addition, the first network device 110-1 may transmit 2110 a third tunnel setup request to the fifth network device 110-5. The third tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The fifth network device 110-5 may establish the data tunnel based on the second tunnel setup request and transmits 2115 a response to the third tunnel setup request.

In other example embodiments, a F1-AP layer is responsible for the tunnel establishment. The tunnel is established between the third network device 110-3 and the first network device 110-1 and between the fourth network device 110-4 and the first network device 110-1. In other words, the fifth network device 110-5 is transparent for the F1-AP layer. In this situation, the first network device 110-1 may transmit 2090 a fourth tunnel setup request to the third network device 110-3. The fourth tunnel setup request may comprise one or more of: the F1-AP address of the fourth network device 110-4 or the second list of RLC channels. The third network device 110-3 may establish the data tunnel between the third network device 110-3 and the first network device 110-1 based on the first tunnel setup request and transmits 2095 a response to the fourth tunnel setup request.

Further, the first network device 110-1 may transmit 2100 a fifth tunnel setup request to the fourth network device 110-4. The fifth tunnel setup request may comprise one or more of: the FA-AP address of the third network device 110-3 or the second list of RLC channels. The fourth network device 110-4 may establish the data tunnel between the fourth network device 110-4 and the first network device 110-1 based on the second tunnel setup request and transmits 2105 a response to the fifth tunnel setup request.

After the data tunnel is established, the data may forward between the fourth network device 110-4 and the third network device 110-3. In some embodiments, the data may be forwarded through the fifth network device 110-5. Alternatively, the data may be forwarded via the first network device 110-1.

Fig. 3 shows a flowchart of an example method 300 in accordance with an embodiment of the present disclosure. Only for the purpose of illustrations, the method 300 can be implemented at a first network device 110-1 as shown in Fig. 1.

At block 310, the first network device 110-1 determines to handover the second network device 110-2 from the third network device 110-3 to the fourth network device 110-4 based on the received measurement. For example, the second network device 110-2 may measure a backhaul 130-2 between the second network device 110-2 and the third network device 110-3. Alternatively, a backhaul 130-1 between the second network device 110-2 and the fourth network device 110-4 may also be measured by the second network device 110-2. In some embodiments, the second network device 110-2 may measure power of signals received on the backhauls.

At block 320, the first network device 110-1 transmits a context setup request to the fourth network device 110-4. The context setup request may be transmitted via F1 application (F1-AP) signaling. Alternatively, the context setup request may be transmitted via BAP signaling. The context setup request at least indicates a first list of RCL channels to be established between the second network device 110-2 and the fourth network device 110-4. The first list of the RCL channels correspond to a second list of RLC channels in the backhaul 130-2 between the second network device 110-2 and the third network device 110-3. In some embodiments, the context setup request may comprise security context information. Alternatively, UE capability information may also be included in the context setup request. In other embodiments, the context setup request may indicate a list of bearers.

In some embodiments, the first network device 110-1 may also transmit a further context setup request to the fifth network device 110-5. The further context setup request may indicate to map the existing RCL channels in the backhaul 130-3 to further existing RCL channels in backhaul 130-4. The further context setup request may not be valid until the fourth network device 110-4 transmits a response to the context setup request to the first network device 110-1.

In other embodiments, the further context setup request may indicate to establish RCL channels in the backhauls 130-3 and 130-4. The number of established RCL channels may correspond to the number of channels in the first list.

In other embodiments, the further context setup request may indicate to establish a set of radio link control channels between the fifth network device 110-5 and the first network device 110-1 and a further set of radio link control channels between the fourth network device 110-4 and the fifth network device 110-5. The number of established RCL channels in in the set of radio link control channels and in the further set of radio link control channels may correspond to the number of channels in the first list. Each radio link control channel in the set of radio link control channels and each radio link control channel in the further set of radio link control channels may correspond to each radio link control channel between the fifth network device 110-5 and the third network device 110-3. Similarly, the further context setup request may not be valid until the fourth network device 110-4 transmits the response to the context setup request to the first network device 110-1.

Alternatively, the context setup request may be transmitted via F1 AP signaling. As discussed above, the context setup request may indicate to map the first list of radio link control channels to existing radio link control channels between the fourth network device 110-4 and the fifth network device 110-5. The further context setup request may indicate update mapping of the existing radio link control channels to further existing radio link control channels between the fifth network device 110-5 and the first network device 110-1. In this situation, after the fourth network device 110-4 transmits the response, the first network device 110-1 may transmit the further context setup request to map between the backhaul 130-5 and the backhaul 130-4.

At block 330, the first network device 110-1 transmits node release request to the third network device 110-3/the fifth network device 110-5 to release the second list of RLC channels between the third network deice 110-3 and the second network device 110-2. The node release request at least indicates the BAP address of the second network device 110-2. In this way, the F1AP signaling in the IAB backhauls can be saved.

In some embodiments, the first network device 110-1 may transmit the node release request to the fifth network device 110-5 to release the second list of RLC channels between the third network deice 110-3 and the second network device 110-2. For example, if the RLC channels in the backhaul 130-2 and the backhaul 130-5 are one-to-one mapped, then the second network device 110-2 is visible to the fifth network device 110-5. The node release request indicating the BAP address of the second network device 110-2 can be transmitted to the fifth network device 110-5 in order to release all RLC channels in the backhaul 130-2.

In other embodiments, in case of multi-to-one mapping in backhaul 130-5, the RLC channels from the backhaul 130-2 and the backhaul 130-6 may aggregated in the backhaul. So, in case the RLC channels in the backhaul 130-2 channels are released, the third network device 110-3 may decrease a bit rate on the second list of RLC channels in the backhaul 130-2 until receiving further explicit configuration from the first network device 110-1 to update one or more RLC channels.

At block 340, after receiving the context setup response from the fourth network device 110-4, the first network device 110-1 transmits RRC configuration to the second network device 110-2. The RRC configuration may comprise BAP configuration of the fourth network device 110-4. Alternatively, the first network device 110-1 may transmit the RRC configuration to the sixth network device 110-6 to update the BAP configuration of the sixth network device 110-6.

In an example embodiment, the first network device 110-1 may receive from the third network device 110-3 information regarding a sequence number status transfer of radio link control channels. The first network device 110-1 may transmit to the fourth network device 110-4 the information regarding the sequence number status transfer of radio link control channels.

In some embodiments, the first network device 110-1 may transmit a first tunnel setup request to the third network device 110-3. The first tunnel setup request may comprise one or more of: the BAP address of the fourth network device 110-4, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4.

Further, the first network device 110-1 may transmit a second tunnel setup request to the fourth network device 110-4. The second tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4.

In addition, the first network device 110-1 may transmit a third tunnel setup request to the fifth network device 110-5. The third tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4.

In other example embodiments, a F1-AP layer is responsible for the tunnel establishment. The tunnel is established between the third network device 110-3 and the first network device 110-1 and between the fourth network device 110-4 and the first network device 110-1. In other words, the fifth network device 110-5 is transparent for the F1-AP layer. In this situation, the first network device 110-1 may transmit a fourth tunnel setup request to the third network device 110-3. The first tunnel setup request may comprise one or more of: the F1-AP address of the fourth network device 110-4 or the second list of RLC channels.

Further, the first network device 110-1 may transmit a fifth tunnel setup request to the fourth network device 110-4. The second tunnel setup request may comprise one or more of: the FA-AP address of the third network device 110-3 or the second list of RLC channels.

Fig. 4 shows a flowchart of an example method 400 in accordance with an embodiment of the present disclosure. Only for the purpose of illustrations, the method 400 can be implemented at a second network device 110-2 as shown in Fig. 1.

The second network device 110-2 may perform measurements of channel qualities. For example, the second network device 110-2 may measure a backhaul 130-2 between the second network device 110-2 and the third network device 110-3. Alternatively, a backhaul 130-1 between the second network device 110-2 and the fourth network device 110-4 may also be measured by the second network device 110-2. In some embodiments, the second network device 110-2 may measure power of signals received on the backhauls.

At block 410, the second network device 110-2 transmits the measurement to the first network device 110-1 for handover from the third network device 110-3 to the fourth network device 110-4.

At block 420, the second network device 110-2 receives radio resource control configuration of the fourth network device 110-4 from the first network device 110-1.

At block 430, the second network device 110-2 updates information of routing and bearer mapping between the second network device 110-2 and the fourth network device 110-4 based on the radio resource control configuration.

In some embodiments, if the second network device 110-2 has a child node (for example, the sixth network device 110-6) , the second network device 110-2 may update the BAP configuration of the sixth network device 110-6. For example, the BAP configuration received from the first network device 110-1 may be transmitted to the sixth network device 110-6 to update the routing and bearer mapping at the sixth network device 110-6.

Fig. 5 shows a flowchart of an example method 500 in accordance with an embodiment of the present disclosure. Only for the purpose of illustrations, the method 500 can be implemented at a third network device 110-3 as shown in Fig. 1.

At block 510, the third network device 110-3 receives a node release request indicating a backhaul adaption protocol address of the second network device 110-2 which is to be handed over from the third network device110-3 to a fourth network device 110-4.

At block 520, the third network device 110-3 releases the second list of radio link control channels between the second network device 110-2 and the third network device 110-3 based on the backhaul adaption protocol address of the second network device 110-2. In some embodiment, the third network device 110-3 may decrease a bit rate on the second list of radio link control channels until receiving a further channel configuration of the second list of radio link control channels. The third network device 110-3 may transmit to the first network device 110-1 a response to the node release information. In some embodiments, the third network device 110-3 may transmit a RLC sequence number status transfer information to the first network device 110-1.

In some embodiments, data tunnel may be established. In this situation, the third network device 110-3 may receive a first tunnel setup request from the first network device 110-1. The first tunnel setup request may comprise one or more of: the BAP address of the fourth network device 110-4 or the fifth device 110-5, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The third network device 110-3 may establish the data tunnel between the fifth network device 110-5 and the third network device 110-3 based on the first tunnel setup request and transmits a response to the first tunnel setup request.

In other example embodiments, a F1-AP layer is responsible for the tunnel establishment. The tunnel is established between the third network device 110-3 and the first network device 110-1 and between the fourth network device 110-4 and the first network device 110-1. In other words, the fifth network device 110-5 is transparent for the F1-AP layer. In this situation, the third network device 110-3 may receive a fourth tunnel setup request from the first network device 110-1. The fourth tunnel setup request may comprise one or more of: the F1-AP address of the fourth network device 110-4 or the second list of RLC channels. The third network device 110-3 may establish the data tunnel between the first network device 110-1 and the third network device 110-3 based on the first tunnel setup request and transmits 2095 a response to the fourth tunnel setup request.

Fig. 6 shows a flowchart of an example method 600 in accordance with an embodiment of the present disclosure. Only for the purpose of illustrations, the method 600 can be implemented at a fourth network device 110-4 as shown in Fig. 1.

At block 610, the fourth network device 110-4 may receive a context setup request from the first network device 110-1. The context setup request may be transmitted via F1 application (F1-AP) signaling. Alternatively, the context setup request may be transmitted via BAP signaling. The context setup request at least indicates a first list of RCL channels to be established between the second network device 110-2 and the fourth network device 110-4. The first list of the RCL channels correspond to a second list of RLC channels in the backhaul 130-2 between the second network device 110-2 and the third network device 110-3. In some embodiments, the context setup request may comprise security context information. Alternatively, UE capability information may also be included in the context setup request. In other embodiments, the context setup request may indicate a list of bearers.

At block 620, the fourth network device 110-4 establishes the first list of RLC channels between the second network device 110-2 and the fourth network device 110-4 based on the context setup request. In some embodiments, the context setup request may be transmitted via BAP signaling. In this situation, the context setup request may indicate to map the established RLC channels to existing RCL channels in backhaul 130-3 (for example, default RCL channels) between the fourth network device 110-4 and the fifth network device 110-5.

At block 630, the fourth network device 110-4 transmits a context setup response to the first network device 110-1. In some embodiments, the fourth network device 110-4 may receive from the first network device information regarding a sequence number status transfer of radio link control channels for data forwarding.

In some embodiments, data tunnel may be established. For example, the fourth network device 110-4 t may receive a second tunnel setup request to from the first network device 110-1. The second tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The fourth network device 110-4 may establish the data tunnel between the fifth network device 110-4 and the fourth network device 110-4 based on the second tunnel setup request and transmits a response to the second tunnel setup request.

In other example embodiments, a F1-AP layer is responsible for the tunnel establishment. The tunnel is established between the third network device 110-3 and the first network device 110-1 and between the fourth network device 110-4 and the first network device 110-1. In other words, the fifth network device 110-5 is transparent for the F1-AP layer. In this situation, he fourth network device 110-4 t may receive a fifth tunnel setup request to from the first network device 110-1. The fifth tunnel setup request may comprise one or more of: the FA-AP address of the third network device 110-3 or the second list of RLC channels. The fourth network device 110-4 may establish the data tunnel between the first network device 110-1 and the fourth network device 110-4 based on the second tunnel setup request and transmit a response to the fifth tunnel setup request.

Fig. 7 shows a flowchart of an example method 700 in accordance with an embodiment of the present disclosure. Only for the purpose of illustrations, the method 700 can be implemented at a fifth network device 110-5 as shown in Fig. 1.

At block 710, the fifth network device 110-5 receives from the first network device 110-1 node release request indicating a backhaul adaption protocol address of a second network device 110-2 which is to be handed over from the third network device 110-3 to the fourth network device 110-4.

At block 720, the fifth network device 110-5 releases a second list of radio link control channels between the second network device 110-2 and the third network device110-3 based on the node release information.

At block 730, the fifth network device 110-5 transmits to the first network device 110-1 a response to the node release request.

In some embodiments, the first network device 110-1 may preconfigure the establishment of the RLC channels. For example, the first network device 110-1 may configure the fifth network device 110-1 to establish the same number of RLC channels in the backhauls 130-3 and 130-4 which corresponds to the RLC channels in the backhaul 130-1. Each radio link control channel in the set of radio link control channels and each radio link control channel in the further set of radio link control channels may correspond to each radio link control channel between the fifth network device 110-5 and the third network device 110-3. Alternatively, when the backhaul 130-1 is established, the fifth network device 110-1 may map all the RCL channels in the backhaul 130-1 to default RLC channels in the backhaul 130-3. In some embodiments, the first network device 110-1 may further transmit and explicit bearer mapping configuration.

In some embodiments, the fifth network device 110-5 may receive from the first network device110-1 a context setup request to establish a set of radio link control channels between the fifth network device 110-5 and the first network device 110-1 and a further set of radio link control channels between the fourth network device 110-4 and the fifth network device 110-5. The number of radio link control channels in the set of radio link control channels and in the further set of radio link control channels corresponding to the number of radio link control channels in the second list. The setup context request is transmitted via F1-AP signaling or backhaul adaption protocol signaling.

In an example embodiment, the fifth network device 110-5 may receive from the first network device110-1 a context setup request via backhaul adaption protocol signaling to update mapping the existing radio link control channels to further existing radio link control channels between the fifth network device 110-5 and the first network device 110-1. After receiving a response to a further context setup request from the second network device 110-2 via the backhaul adaption protocol signaling, the fifth network device 110-5 may map the existing radio link control channels to the further existing radio link control channels.

In some embodiments, data tunnel may be established. The fifth network device 110-5 may receive a third tunnel setup request from the first network device 110-1. The third tunnel setup request may comprise one or more of: the BAP address of the third network device 110-3, the second list of RLC channels and the routing configuration between the third network device 110-3 and the fourth network device 110-4. The fifth network device 110-5 may establish the data tunnel based on the second tunnel setup request and transmits a response to the third tunnel setup request.

In other example embodiments, a F1-AP layer is responsible for the tunnel establishment. The tunnel is established between the third network device 110-3 and the first network device 110-1 and between the fourth network device 110-4 and the first network device 110-1. In other words, the fifth network device 110-5 is transparent for the F1-AP layer. In this situation, the first network device 110-1 may transmit 2090 a fourth tunnel setup request to the third network device 110-3. The first tunnel setup request may comprise one or more of: the F1-AP address of the fourth network device 110-4 or the second list of RLC channels. The third network device 110-3 may establish the data tunnel based on the first tunnel setup request and transmits 2095 a response to the fourth tunnel setup request.

Further, the first network device 110-1 may transmit 2100 a fifth tunnel setup request to the fourth network device 110-4. The second tunnel setup request may comprise one or more of: the FA-AP address of the third network device 110-3 or the second list of RLC channels. The fourth network device 110-4 may establish the data tunnel based on the second tunnel setup request and transmits 2105 a response to the fifth tunnel setup request.

Fig. 8 is a simplified block diagram of a device 800 that is suitable for implementing embodiments of the present disclosure. The device 800 can be considered as a further example implementation of the terminal device 110, the network device 120, the network device 130, or the transition network device 310 as shown in Fig. 1 and Fig. 3. Accordingly, the device 800 can be implemented at or as at least a part of the terminal device 110, the network device 120, the network device 130, or the transition network device 310.

As shown, the device 800 includes a processor 810, a memory 820 coupled to the processor 810, a suitable transmitter (TX) and receiver (RX) 840 coupled to the processor 810, and a communication interface coupled to the TX/RX 840. The memory 820 stores at least a part of a program 830. The TX/RX 840 is for bidirectional communications. The TX/RX 840 has at least one antenna to facilitate communication, though in practice an Access Node mentioned in this application may have several ones. The communication interface may represent any interface that is necessary for communication with other network elements, such as X2 interface for bidirectional communications between eNBs, S1 interface for communication between a Mobility Management Entity (MME) /Serving Gateway (S-GW) and the eNB, Un interface for communication between the eNB and a relay node (RN) , or Uu interface for communication between the eNB and a terminal device.

The program 830 is assumed to include program instructions that, when executed by the associated processor 810, enable the device 800 to operate in accordance with the embodiments of the present disclosure, as discussed herein with reference to Fig. 2 to 7. The embodiments herein may be implemented by computer software executable by the processor 810 of the device 800, or by hardware, or by a combination of software and hardware. The processor 810 may be configured to implement various embodiments of the present disclosure. Furthermore, a combination of the processor 810 and memory 820 may form processing means 850 adapted to implement various embodiments of the present disclosure.

The memory 820 may be of any type suitable to the local technical network and may be implemented using any suitable data storage technology, such as a non-transitory computer readable storage medium, semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory, as non-limiting examples. While only one memory 820 is shown in the device 800, there may be several physically distinct memory modules in the device 800. The processor 810 may be of any type suitable to the local technical network, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs) and processors based on multicore processor architecture, as non-limiting examples. The device 800 may have multiple processors, such as an application specific integrated circuit chip that is slaved in time to a clock which synchronizes the main processor.

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

The present disclosure also provides at least one computer program product tangibly stored on a non-transitory computer readable storage medium. The computer program product includes computer-executable instructions, such as those included in program modules, being executed in a device on a target real or virtual processor, to carry out the process or method as described above with reference to any of Figs. 2-4. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, or the like that perform particular tasks or implement particular abstract data types. The functionality of the program modules may be combined or split between program modules as desired in various embodiments. Machine-executable instructions for program modules may be executed within a local or distributed device. In a distributed device, program modules may be located in both local and remote storage media.

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

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

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

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

Claims

A communication method comprising:

determining, at a first network device, to handover a second network device from a third network device to a fourth network device based on a measurement of channel quality received from the second network device;

transmitting a context setup request to the fourth network device, the context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and the second network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device;

transmitting, to the third network device, a node release request indicating a backhaul adaption protocol address of the second network device; and

in response to receiving a context setup response from the fourth network device, transmitting radio resource control configuration of the fourth network device to the second network device for preparing the handover.
The method of claim 1, further comprising:

in response to each radio control channel between the second network device and the third network device corresponding to each radio control channel between the third network device and a fifth network device, transmitting, to the fifth network device, the node release request indicating a backhaul adaption protocol address of the second network device, the fifth network device being an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device.
The method of claim 1, wherein transmitting the radio resource control configuration to the second network device comprises:

transmitting the radio resource control configuration indicating configuration of backhaul adaption protocol of the fourth network device, to enable the second network device to update information of routing and bearer mapping between the second network device and the fourth network device.
The method of claim 1, further comprising:

transmitting, to a fifth network device, a further context setup request to establish a set of radio link control channels between the fifth network device and the first network device and a further set of radio link control channels between the fourth network device and the fifth network device, the number of radio link control channels in the set of radio link control channels and in the further set of radio link control channels corresponding to the number of radio link control channels between the second network device and the third network device, each radio link control channel in the set of radio link control channels and each radio link control channel in the further set of radio link control channels corresponding to each radio link control channel between the fifth network device and the third network device.
The method of claim 1, wherein transmitting the context setup request comprises:

transmitting, to the second network device, the context setup request indicating to map the first list of radio link control channels to default radio link control channels between the fourth network device and the fifth network device; and

transmitting to the fifth network device a further context setup request to update mapping of the default radio link control channels to further default radio link control channels between the fifth network device and the first network device.
The method of claim 4 or 5, wherein the context setup request and the further setup context request are transmitted via backhaul adaption protocol signaling.
The method of claim 1, further comprising:

receiving, from the third network device, information regarding a radio link control layer sequence number status transfer of radio link control channel between the third network device and the fourth network device; and

transmitting, to the fourth network device, the information regarding the radio link control layer sequence number status transfer.
The method of claim 1, further comprising:

establishing a data tunnel for forwarding data between the third network device and the fourth network device.
The method of claim 8, wherein establishing the data tunnel comprises:

transmitting, to the third network device, a first tunnel setup request indicating one or more of the following: a backhaul adaption protocol address of the fourth network device or a fifth network device, the second list of radio link control channels, or routing configuration between the third network device and the fourth network device, wherein the fifth network device is an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device;

transmitting, to the fourth network device, a second tunnel setup request indicating one or more of the following: a backhaul adaption protocol address of the third network device, the second list of radio link control channels , or the routing configuration; and

transmitting, to the fifth network device, a third tunnel setup request indicating one or more of the following: the backhaul adaption protocol address of the fourth network device, the second list of radio link control channels, or the routing configuration.
The method of claim 8, wherein establishing the data tunnel comprises:

transmitting, to the third network device, a fourth tunnel setup request indicating one or more of the following: a F1 application protocol address of the fourth network device or the second list of radio link control channels; and

transmitting, to the fourth network device, a fifth tunnel setup request indicating one or more of the following: a F1 application protocol address of the third network device or the second list of radio link control channels.
A communication method comprising:

transmitting, at a second network device, a measurement of channel quality to a first network device for handover from a third network device to a fourth network device;

receiving radio resource control configuration of the fourth network device from the first network device; and

updating information of routing and bearer mapping between the second network device and the fourth network device based on the radio resource control configuration.
A communication method comprising:

receiving, at a third network device and from a first network device, a node release request indicating a backhaul adaption protocol address of a second network device which is to be handed over from the third network device to a fourth network device; and

releasing a second list of radio link control channels between the second network device and the third network device based on the backhaul adaption protocol address of the second network device.
The method of claim 12, further comprising:

transmitting to the first network device a response to the node release information.
The method of claim 12, wherein releasing the second list of radio link control channels comprises:

decreasing a bit rate based on bit rates of the released second list of radio link control channels until receiving a configuration indicating an updated bit rate .
The method of claim 12, further comprising:

transmitting, to the first network device or the fifth network device, information regarding a radio link control layer sequence number status transfer of radio link control channel for data forwarding between the third network device and the fourth network device.
The method of claim 12, further comprising:

receiving, from the first network device, a first tunnel setup request indicating one or more of the following: a backhaul adaption protocol address of the fourth network device or a fifth network device, the second list of radio link control channels, or routing configuration between the third network device and the fourth network device, wherein the fifth network device is an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device;

establishing the data tunnel between the fifth network device and the third network device based on the first tunnel setup request; and

transmitting, to the first network device, a response to the first tunnel setup request.
The method of claim 12, further comprising:

receiving, from the first network device, a fourth tunnel setup request indicating one or more of the following: a F1 application protocol address of the fourth network device or the second list of radio link control channels;

establishing the data tunnel between the first network device and the third network device based on the fourth tunnel setup request; and

transmitting, to the first network device, a response to the fourth tunnel setup request.
A communication method comprising:

receiving, at a fourth network device and from a first network device, a context setup request at least indicating a first list of radio link control channels to be established between the fourth network device and a second network device which is to be handed over from the a third network device to the fourth network device, the first list of radio link control channels corresponding to a second list of radio link control channels between the second network device and the third network device;

establishing the first list of radio link control channel; and

transmitting a context setup response to the first network device.
The method of claim 18, further comprising:

mapping the first list of radio link control channels to default radio link control channels between the fourth network device and a fifth network device which is an intermedia device between the fourth network device and the first network device.
The method of claim 18 or 19, wherein the context setup request is received via backhaul adaption protocol signaling.
The method of claim 18, further comprising:

receiving, from the first network device, information regarding a radio link control layer sequence number status transfer for data forwarding between the third network device and the fourth network device.
The method of claim 18, further comprising:

receiving, from the first network device, a second tunnel setup request, the second tunnel setup request indicating one or more of the following: a backhaul adaption protocol address of the third network device, the second list of radio link control channels, or routing configuration between the third network device and the fourth network device;

establishing the data tunnel between the fifth network device and the fourth network device based on the second tunnel setup request; and

transmitting, to the first network device, a response to the second tunnel setup request.
The method of claim 18, further comprising:

receiving, from the first network device, a fifth tunnel setup request indicating one or more of the following: a F1 application protocol address of the third network device or the second list of radio link control channels;

establishing the data tunnel between the first network device and the fourth network device based on the fifth tunnel setup request; and

transmitting, to the first network device, a response to the fifth tunnel setup request.
A communication method comprising:

in response to each radio control channel between a second network device and a third network device corresponding to each radio control channel between the third network device and a fifth network device, receiving, at the fifth network device and from a first network device, a node release request indicating a backhaul adaption protocol address of the second network device which is to be handed over from a third network device to a fourth network device, the fifth network device being an intermedia network device between the third network device and the first network device and between the fourth network device and the first network device;

releasing a second list of radio link control channels between the second network device and the third network device based on the node release request; and

transmitting to the first network device a response to the node release request.
The method of claim 24, further comprising:

establishing a set of radio link control channels between the fifth network device and the first network device and a further set of radio link control channels between the fourth network device and the fifth network device, the number of radio link control channels in the set of radio link control channels and in the further set of radio link control channels corresponding to the number of radio link control channels between the second network device and the third network device, each radio link control channel in the set of radio link control channels and each radio link control channel in the further set of radio link control channels corresponding to each radio link control channel between the fifth network device and the third network device.
The method of claim 23, further comprising:

mapping default radio link control channels between the fourth network device and the fifth network device to further default radio link control channels between the fifth network device and the first network device.
The method of claim 23, wherein the mapping is trigged by receiving from the second network device a response to a context setup request via the backhaul adaption protocol signaling.
The method of claim 23, further comprising:

receiving, from the first network device, a third tunnel setup request indicating one or more of the following: a backhaul adaption protocol address of the fourth network device, the second list of radio link control channels, or a routing configuration; and

transmitting a response to the third tunnel setup request.
A first network device, comprising:

a processing unit; and

a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the first network device to perform any one of claims 1-10.
A second network device, comprising:

a processing unit; and

a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the second network device to perform the method of claim 11.
A third network device, comprising:

a processing unit; and

a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the third network device to perform any one of claims 12-17.
A fourth network device, comprising:

a processing unit; and

a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the fourth network device to perform any one of claims 18-23.
A fifth network device, comprising:

a processing unit; and

a memory coupled to the processing unit and storing instructions thereon, the instructions, when executed by the processing unit, causing the fifth network device to perform any one of claims 24-28.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 1-10.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to claim 11.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 12-17.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 18-23.
A computer readable medium having instructions stored thereon, the instructions, when executed on at least one processor, causing the at least one processor to carry out the method according to any of claims 24-28.