CN116567745A

CN116567745A - Communication method, terminal device, access network device, medium and chip

Info

Publication number: CN116567745A
Application number: CN202210869803.5A
Authority: CN
Inventors: 王凡凡; 耿婷婷
Original assignee: Huawei Technologies Co Ltd
Current assignee: Huawei Technologies Co Ltd
Priority date: 2022-01-28
Filing date: 2022-07-21
Publication date: 2023-08-08

Abstract

Communication methods, terminal devices, access network devices, media and chips are provided. The method comprises the steps that the terminal equipment obtains a cell change reason indication. The cell change cause indication indicates that a first cell change of the terminal device from the source cell to the first target cell or a second cell change of the terminal device from the first target cell to the second target cell is associated with a communication service of the terminal device. The first target cell employs a first radio access technology, and the source cell and the second target cell employ a second radio access technology different from the first radio access technology. The method further comprises the terminal device sending a cell change cause indication to a second target access network device providing a second target cell. Therefore, the second target access network device can treat the communication service flow and the intersystem ping-pong event differently, and the optimization of redundant intersystem switching parameters caused by invalid triggering of the normal communication service flow of the terminal device is avoided.

Description

Communication method, terminal device, access network device, medium and chip

Technical Field

The present application relates to the field of communications, and more particularly, to a communication method, a terminal device, an access network device, a computer readable storage medium, and a chip.

Background

The handover of a terminal device between cells employing different radio access technologies (Radio Access Technology, RAT) may be referred to as an intersystem handover. Too frequent inter-system handovers may result in wasted communication resources and poor communication robustness. Thus, inter-system Ping-pong (Inter-system Ping-pong) events may be considered to be involved in Inter-system handoff parameters that may be optimized to avoid too frequent Inter-system handoffs.

However, if the inter-system ping-pong event is not properly identified, it may also cause excessive adjustment of the inter-system handoff parameters, wasting system resources, and reducing communication efficiency.

Disclosure of Invention

The present application provides a scheme for communication.

In a first aspect of the present application, a communication method implemented at a terminal device is provided. The method comprises the following steps: the terminal equipment acquires a cell change reason indication, wherein the cell change reason indication indicates that a first cell change from a source cell to a first target cell or a second cell change from the first target cell to a second target cell of the terminal equipment is associated with communication service of the terminal equipment, the first target cell adopts a first radio access technology (radio access technology, RAT), and the source cell and the second target cell adopt a second RAT different from the first RAT; and the terminal equipment sends the cell change reason indication to the second target access network equipment to which the second target cell belongs. Therefore, the second target access network device can treat the communication service flow and the intersystem ping-pong event differently, and the optimization of redundant intersystem switching parameters caused by invalid triggering of the normal communication service flow of the terminal device is avoided.

In one possible implementation, the cell change cause indication includes: the reason why the terminal device changes out of the source cell or out of the first target cell, and/or the reason why the terminal device changes to the first target cell or to the second target cell.

In one possible implementation, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; alternatively, the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell. Therefore, the optimization of the redundant intersystem switching parameters caused by invalid voice service flow triggering of the terminal equipment is avoided.

In one possible implementation manner, the terminal device may further obtain at least one of the following: an indication of the type of the voice fallback procedure and an indication of the cell change execution mode. The indication of the type of the voice fallback procedure indicates that the voice fallback procedure is an evolved packet system voice fallback procedure or an inter-radio access technology voice fallback procedure. The cell change execution mode includes handover or redirection.

In one possible implementation, the voice fallback procedure includes a normal call voice fallback procedure or an emergency call voice fallback procedure, and the quick return procedure includes a normal call voice quick return procedure or an emergency call voice quick return procedure.

In one possible implementation, the obtaining, by the terminal device, the indication of the cause of the cell change includes the terminal device obtaining, by the terminal device, the indication of the cause of the cell change from a source access network device to which the source cell belongs.

In one possible implementation manner, the terminal device obtaining the indication of the reason for the cell change from the source access network device includes: the terminal device receives a first cell change command associated with a first cell change from the source access network device, the first cell change command comprising a cell change cause indication. Sending the cell change cause indication to the terminal device via the first cell change command may avoid additional signaling overhead.

In one possible implementation manner, the terminal device obtaining the indication of the reason for the cell change includes: the terminal equipment acquires the indication of the cell change reason from the first target access network equipment to which the first target cell belongs.

In one possible implementation manner, the terminal device obtaining the indication of the reason for the cell change from the first target access network device includes: the terminal device receives a second cell change command associated with a second cell change from the first target access network device, the second cell change command comprising a cell change cause indication. Sending the cell change cause indication to the terminal device via the second cell change command may avoid additional signaling overhead.

In one possible implementation manner, the sending, by the terminal device, the indication of the cause of the cell change to the second target access network device includes: the terminal device, in response to receiving a second cell switch command associated with a second cell change from a first target access network device to which the first target cell belongs, sends a radio resource control reconfiguration complete message to the second target access network device, the radio resource control reconfiguration complete message including a cell change cause indication.

In one possible implementation manner, the sending, by the terminal device, the indication of the cause of the cell change to the second target access network device includes: the terminal equipment receives a request for history information of the terminal equipment from second target access network equipment; and the terminal equipment sends history information to the second target access network equipment, wherein the history information comprises cell change reason indication. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, the first RAT may be a second generation (2nd Generation,2G) RAT, a third generation (3) ^rd Generation, 3G) RAT and one of the fourth Generation (4th Generation,4G) RATs, the second RAT may be a fifth Generation (5th Generation,5G) RAT.

In a second aspect of the present application, a communication method implemented at a first target access network device is provided. The method comprises the following steps: the first target access network device acquires a cell change reason indication, wherein the cell change reason indication indicates that a first cell change of the terminal device from a source cell to a first target cell of the first target access network device or a second cell change of the terminal device from the first target cell to a second target cell is associated with communication service of the terminal device, the first target cell adopts a first RAT, and the source cell and the second target cell adopt a second RAT different from the first RAT; and the first target access network equipment provides the cell change reason indication for the second target access network equipment to which the second target cell belongs.

In one possible implementation, the first target access network device further obtains at least one of: an indication of the type of the voice fallback procedure and an indication of the cell change execution mode. The indication of the type of the voice fallback procedure indicates that the voice fallback procedure is an evolved packet system voice fallback procedure or an inter-radio access technology voice fallback procedure. The cell change execution mode includes handover or redirection.

In one possible implementation manner, the obtaining, by the first target access network device, the indication of the cause of the cell change includes: the first target access network device acquires a cell change reason indication from source access network devices to which the source cell belongs.

In one possible implementation, the first target access network device obtaining the indication of the cause of the cell change from the source access network device includes: the first target access network device acquires history information of the terminal device from the source access network device, wherein the history information comprises cell change reason indication. Sending the indication of the cause of the cell change to the first target access network device together with the history information may avoid additional signaling overhead.

In one possible implementation, the providing, by the first target access network device, the indication of the cause of the cell change to the second target access network device includes: the first target access network device provides second history information of the terminal device to the second target access network device, the second history information comprises cell change reason indication, the second history information comprises first history information, and/or third history information of the terminal device recorded by the first target access network device. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, the providing, by the first target access network device, the indication of the cause of the cell change to the second target access network device includes: the first target access network device provides a handover request for the second cell change to the second target access network device, the handover request including a cell change cause indication. Sending the cell change cause indication with the handover request to the second target access network device may avoid additional signaling overhead.

In a third aspect of the present application, a communication method implemented at a second target access network device is provided. The method comprises the following steps: the second target access network device obtains a cell change reason indication, wherein the cell change reason indication indicates that a first cell change from a source cell to a first target cell or a second cell change from the first target cell to a second target cell of the second target access network device of the terminal device is associated with communication service of the terminal device, the first target cell adopts a first RAT, and the source cell and the second target cell adopt a second RAT different from the first RAT; and the second target access network equipment sends the cell change reason indication to the source access network equipment to which the source cell belongs. Therefore, the source access network equipment can treat the communication service flow and the intersystem ping-pong event differently, and the optimization of redundant intersystem switching parameters caused by invalid triggering of the normal communication service flow of the terminal equipment is avoided.

In one possible implementation, the second target access network device further obtains at least one of: an indication of the type of the voice fallback procedure and an indication of the cell change execution mode. The indication of the type of the voice fallback procedure indicates that the voice fallback procedure is an evolved packet system voice fallback procedure or an inter-radio access technology voice fallback procedure. The cell change execution mode includes handover or redirection.

In one possible implementation manner, the second target access network device obtaining the indication of the reason for the cell change from the terminal device includes: a radio resource control reconfiguration complete message is received from the terminal equipment, the radio resource control reconfiguration complete message comprising an indication of a cause of a cell change.

In one possible implementation manner, the obtaining, by the second target access network device, the indication of the cause of the cell change includes: and acquiring the indication of the cell change reason from the terminal equipment.

In one possible implementation manner, the second target access network device obtaining the indication of the reason for the cell change from the terminal device includes: sending a request for history information of the terminal equipment to the terminal equipment; and receiving history information from the terminal device, the history information including an indication of a cause of the cell change. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, obtaining the indication of the cause of the cell change includes: and acquiring the indication of the cell change reason from the source access network equipment to which the source cell belongs.

In one possible implementation, obtaining the indication of the cause of the cell change from the source access network device includes: and acquiring historical information of the terminal equipment from the source access network equipment, wherein the historical information comprises cell change reason indication. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, obtaining the indication of the cause of the cell change includes: and acquiring a cell change reason instruction from first target access network equipment to which the first target cell belongs.

In one possible implementation, obtaining the indication of the cause of the cell change from the first target access network device includes: and acquiring second history information of the terminal equipment from the first target access network equipment, wherein the second history information comprises cell change reason indication, and the second history information comprises first history information of the terminal equipment acquired by the first target access network equipment from source access network equipment to which a source cell belongs and/or third history information of the terminal equipment recorded by the first target access network equipment. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, obtaining the indication of the cause of the cell change from the first target access network device includes: a handover request for a second cell change is received from a first target access network device, the handover request including a cell change cause indication.

In a fourth aspect of the present application, a communication method implemented at a source access network device is provided. The method comprises the following steps: the source access network device obtains a cell change cause indication that the first cell change or the second cell change is associated with a communication service of the terminal device. The first cell change comprises a terminal device changing from a source cell provided by the source access network device to a first target cell, and the second cell change comprises a terminal device changing from the first target cell to a second target cell. The first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology. The first radio access technology is different from the second radio access technology. Further, the source access network device determines that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Therefore, the source access network equipment can treat the communication service flow and the intersystem ping-pong event differently, and the optimization of redundant intersystem switching parameters caused by invalid triggering of the normal communication service flow of the terminal equipment is avoided.

In one possible implementation manner, the source access network device obtaining the indication of the reason for the cell change includes: and acquiring a cell change reason instruction from second target access network equipment to which the second target cell belongs.

In one possible implementation, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; and the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell.

In one possible implementation, the method further includes: the source access network device obtains at least one of the following: an indication of the type of the voice fallback procedure and an indication of the cell change execution mode. The indication of the type of voice fallback procedure indicates that the voice fallback procedure is an evolved packet system voice fallback procedure or an inter-radio access technology voice fallback procedure. Cell change implementations include handover or redirection.

In a possible implementation manner of the first aspect, the second aspect, the third aspect or the fourth aspect, the indication of the cause of the cell change includes: the reason why the terminal device changes out of the source cell or out of the first target cell, and/or the reason why the terminal device changes to the first target cell or to the second target cell.

In a possible implementation manner of the first aspect, the second aspect, the third aspect or the fourth aspect, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; alternatively, the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell. Therefore, the optimization of the redundant intersystem switching parameters caused by invalid voice service flow triggering of the terminal equipment is avoided.

In a possible implementation manner of the first aspect, the second aspect, the third aspect or the fourth aspect, the voice fallback procedure includes a normal call voice fallback procedure or an emergency call voice fallback procedure, and the quick return procedure includes a normal call voice quick return procedure or an emergency call voice quick return procedure.

In a possible implementation manner of the first aspect, the second aspect, the third aspect or the fourth aspect, the first RAT is one of a 2G RAT, a 3G RAT and a 4G RAT, and the second RAT is a 5G RAT.

In a fifth aspect of the present application, there is provided a communication apparatus comprising means for performing the steps described in the first aspect above. The communication device may be a terminal or a device for a terminal.

For example, the communication apparatus includes an acquisition unit and a transmission unit. The acquisition unit is configured to acquire a cell change cause indication indicating that a first cell change of the terminal device from the source cell to the first target cell or a second cell change of the terminal device from the first target cell to the second target cell is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The transmitting unit is configured to transmit a cell change cause indication to a second target access network device to which the second target cell belongs.

In a sixth aspect of the present application, there is provided an access network device comprising means or means for performing the steps described in the second aspect above.

For example, the access network device comprises an acquisition unit and a providing unit. The acquisition unit is configured to acquire a cell change cause indication indicating that a first cell change of a first target cell managed by the terminal device from a source cell to the access network device or a second cell change of a second target cell from the first target cell to the second target cell is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The providing unit is configured to provide an indication of a cause of a cell change to a second target access network device to which the second target cell belongs.

In a seventh aspect of the present application, there is provided an access network device comprising means or means for performing the steps described in the third aspect above.

The access network device comprises an acquisition unit and a determination unit. The acquisition unit is configured to acquire a cell change cause indication indicating that a first cell change of the terminal device from the source cell to the first target cell or a second cell change of the second target cell managed from the first target cell to the access network device is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The determining unit is configured to determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication.

In an eighth aspect of the present application, there is provided an access network device comprising means for performing the steps described in the fourth aspect above.

The access network device comprises an acquisition unit and a determination unit. The acquisition unit is configured to acquire a cell change cause indication, the cell change cause indication being associated with a communication service of the terminal device. The first cell change comprises a terminal device changing from a source cell provided by the source access network device to a first target cell, and the second cell change comprises a terminal device changing from the first target cell to a second target cell. The first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology. The determining unit is configured to determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication.

In a ninth aspect of the present application, a communication apparatus is provided. The communication device includes: at least one processor; and at least one memory coupled to the at least one processor and storing instructions for execution by the at least one processor. The instructions, when executed by at least one processor, cause the communication device to implement the method according to any one of the first, second, third and fourth aspects described above.

In a tenth aspect of the present application, a computer readable storage medium is provided. A computer-readable storage medium has stored thereon a computer program which, when executed by a processor, implements the method according to any of the above first, second, third and fourth aspects.

In an eleventh aspect of the present application, a computer program product is provided. The computer program product is tangibly stored on a computer readable medium and comprises computer executable instructions which, when executed, cause an apparatus to implement the method according to any one of the first, second, third and fourth aspects described above.

In a twelfth aspect of the present application, a chip is provided. The chip is configured to perform the method according to any of the above first, second, third and fourth aspects.

In a thirteenth aspect of the present application, a communication system is provided. The communication system comprises a communication apparatus according to the fifth aspect, an access network device according to the sixth aspect, an access network device according to the seventh aspect and an access network device according to the eighth aspect.

Drawings

Features, advantages, and other aspects of various implementations of the present application will become apparent with reference to the following detailed description when taken in conjunction with the accompanying drawings. Several implementations of the present application are illustrated herein by way of example and not by way of limitation, in the accompanying drawings:

fig. 1 shows a schematic block diagram of a communication network in which a possible implementation of the present application may be implemented;

FIGS. 2A and 2B show schematic block diagrams of communication networks, respectively, in which possible implementations of the present application may be implemented;

FIG. 3 illustrates a signaling interaction diagram of an example communication process according to one possible implementation of the present application;

fig. 4 and 5 show signaling interaction diagrams of an example communication procedure according to another possible implementation of the present application;

FIG. 6 shows a signaling interaction diagram of an example communication procedure according to yet another possible implementation of the present application;

fig. 7 and 8 show signaling interaction diagrams of an example communication procedure according to yet another possible implementation of the present application;

FIG. 9 shows a flow chart of a communication method according to one possible implementation of the present application;

FIG. 10 shows a flow chart of a communication method according to another possible implementation of the present application;

FIG. 11 shows a flow chart of a communication method according to yet another possible implementation of the present application;

fig. 12 shows a schematic block diagram of a terminal device according to one possible implementation of the present application;

fig. 13 shows a schematic block diagram of a first access network device according to another possible implementation of the present application;

fig. 14 shows a schematic block diagram of a second access network device according to yet another possible implementation of the present application; and FIG. 15 is a simplified block diagram of an example device suitable for implementing a possible implementation of the present application.

In the various drawings, the same or similar reference numbers represent the same or similar elements.

Detailed Description

Possible implementations of the present application will be described in more detail below with reference to the accompanying drawings.

In the description of possible implementations of the present application, the term "comprising" and its similar terms should be understood as open-ended, i.e. "including, but not limited to. The term "based on" should be understood as "based at least in part on". The term "one possible implementation" or "the possible implementation" should be understood as "at least one possible implementation". The terms "first," "second," and the like, may refer to different or the same object. Other explicit and implicit definitions are also possible below. A expression similar to "at least one of A, B and C" or "at least one of A, B or C" should be understood as any one of the following: at least one A; at least one B; at least one C; at least one a and at least one B; at least one a and at least one C; at least one B and at least one C; at least one a, at least one B and at least one C, as exemplified above by the three elements A, B and C, when more elements are present in the expression, the meaning of the expression may be obtained according to the rules described above.

Fig. 1 shows a schematic block diagram of a communication network 100 in which a possible implementation of the present application may be implemented. As shown, communication network 100 includes access network devices 110, 120, and 130 and terminal device 140.

The access network devices 110, 120 and 130 are radio access network (Radio Access Network, RAN) devices that access the terminal device 140 to a wireless network. Examples of RAN devices may include, but are not limited to: next generation mobile communication Node B (gNB), transmission and reception Point (TransmissionReception Point, TRP), evolved Node B (eNB), radio network controller (Radio Network Controller, RNC), node B (Node B, NB), base station controller (Base Station Controller, BSC), base transceiver station (Base Transceiver Station, BTS), home Base station (e.g., home Evolved Node B, or home Node B), baseband Unit (Base Band Unit, BBU), or wireless fidelity (Wireless Fidelity, wifi) Access Point (Access Point, AP), access backhaul integrated (Integrated Access and Backhaul, IAB) Node, and the like. In one possible implementation, at least one of access network devices 110, 120, and 130 may include a Centralized Unit (CU), or a Distributed Unit (DU), or both a CU and a DU.

The terminal device 140 is a device having a wireless transmitting/receiving function. Terminal device 140 may be deployed on land, including indoors or outdoors, hand-held, or vehicle-mounted; can also be deployed on the water surface (such as ships, etc.); but may also be deployed in the air (e.g., on aircraft, balloon, satellite, etc.). The terminal device 140 may be a Mobile Phone (Mobile Phone), a tablet (Pad), a computer with a wireless transceiving function, a Virtual Reality (VR) terminal device, an augmented Reality (Augmented Reality, AR) terminal device, a wireless terminal device in industrial control (Industrial Control), a wireless terminal device in unmanned (Self Driving), a wireless terminal device in Remote Medical (Remote Medical), a wireless terminal in Smart Grid (Smart Grid), a wireless terminal in transportation security (Transportation Safety), a wireless terminal device in Smart City (Smart City), a wireless terminal device in Smart Home (Smart Home), or a User Equipment (UE), etc.

It will be appreciated that the number of access network devices and terminal devices shown in fig. 1 is merely an example and is not intended to suggest any limitation. The communication network 100 may comprise any suitable number of access network devices, terminal devices, according to the actual needs.

Access network device 110 employs a first RAT and access network devices 120 and 130 employ a second RAT that is different from the first RAT, that is, the communication scheme of access network device 110 is different from the communication scheme of access network devices 120 and 130. In one possible implementation, the first RAT may be one of 2G, 3G, and 4G RATs and the second RAT may be a 5G RAT. Although in the following possible implementations of the present application will be described by taking the example that the first RAT is a 4G RAT and the second RAT is a 5G RAT, in other possible implementations, the first RAT and the second RAT may also be other RATs as long as they are different from each other. For example, in another possible implementation, the first RAT may be a 2G or 3G RAT and the second RAT may be a 4G RAT.

At least one of the access network devices 110, 120 and 130 provides services for the terminal device 140. The service areas of access network devices 110, 120, and 130 are referred to as cells 112, 122, and 132, respectively.

In one possible implementation, the communication traffic of terminal device 140 may trigger terminal device 140 to change from cell 132 to cell 112 and then from cell 112 to cell 122. In such possible implementations, the access network device 130 is also referred to as a source access network device 130, and the cell 132 is also referred to as a source cell 132; the access network device 110 is also referred to as a first target access network device 110, and the cell 112 is also referred to as a first target cell 112; access network device 120 is also referred to as a second target access network device 120 and cell 122 is also referred to as a second target cell 122. Hereinafter, the cell change of the terminal device 140 from the cell 132 to the cell 112 is also referred to as a first cell change, and the cell change of the terminal device 140 from the cell 112 to the cell 122 is also referred to as a second cell change.

The "cell change" may also be referred to as "cell change". In one possible implementation, the cell change or the manner in which the cell change is performed may include a handover or redirection.

In one possible implementation, the communication network 100 may employ a dual connectivity mode. In the dual connectivity mode, the terminal device 140 may be connected to the primary node and the secondary node at the same time, where the primary node may be an access network device using a 5G RAT, the secondary node may be an access network device using a 4G RAT, the primary node may establish a control plane connection with the 5G core network, and the primary node or the secondary node may respectively establish a user plane connection with the 5G core network. This will be described with reference to fig. 2A.

Fig. 2A shows a schematic block diagram of a communication network 200A in which a possible implementation of the present application may be implemented. Communication network 200A may be considered an example implementation of communication network 100. As shown in fig. 2A, communication network 200A includes access network devices 110, 120, and 130, and terminal device 140. The communication network 200A adopts a dual connectivity mode. Access network devices 120 and 130 employing 5GRAT are connected to 5GC150, and access network device 110 employing 4G RAT is also connected to 5GC150. In communication network 200A, access network device 120 or 130 acts as a primary node and access network device 110 acts as a secondary node. Terminal device 140 is connected to both access network devices 120 and 130 and access network device 110.

It will be appreciated that in the dual connectivity mode, the terminal device 140 changes from the cell of the primary node to the cell of the secondary node for some type of communication traffic (e.g., voice traffic). In this case, other communication services (e.g., communication services other than voice services) of the terminal device 140 are still performed in the master node. After the communication service is completed, the terminal device 140 may change from the cell of the secondary node to the cell of the primary node, and re-access the cell of the primary node. Furthermore, the source cell in the dual connectivity scenario is the cell of the primary node, while the first target cell is the cell of the secondary node, the cell of the re-accessed primary node may be different from the source cell.

In another possible implementation, the communication network 100 may employ a single connection mode. In the single connectivity mode, access network devices employing a 5G RAT may connect to a 5G core network 5GC, while access network devices employing a 4G RAT may connect to an evolved packet core network (Evolved Packet Core, EPC). The terminal device 140 is connected only to an access network device employing a 5G RAT or only to an access network device employing a 4G RAT.

In the single connection mode, the terminal device 140 may change from a source cell employing a 5G RAT to a target cell employing a 4G RAT for some type of communication service (e.g., voice service). In this case, the terminal device 140 hands over all traffic to the target cell. After completing the communication service, the terminal device 140 may change from the target cell back to the cell of the source system, and re-access the cell of the source system. The cell of the source system may be a source cell or other cell that uses the same RAT as the source cell. This will be described with reference to fig. 2B.

Fig. 2B shows a schematic block diagram of a communication network 200B in which a possible implementation of the present application may be implemented. Communication network 200B may be viewed as another example implementation of communication network 100. In communication network 200B, access network devices 120 and 130 employing a 5G RAT are connected to 5gc 150, respectively, while access network device 110 employing a 4G RAT is connected to EPC160.

In one possible implementation, examples of communication traffic that triggers the terminal device 140 to perform the first cell change and the second cell change may include, but are not limited to, voice traffic, data traffic. Possible implementations of the present application will be described hereinafter by taking voice traffic as an example. However, it should be understood that the solution of the present application is also applicable to other communication services than voice services.

In an implementation where the communication traffic is voice traffic, the 5G network may not support voice traffic (e.g., voNR). The reason why the 5G network does not support voice traffic may be at least one of: 5GC does not deploy IMS; although 5GC deploys IMS, there is no 5G cell coverage or poor 5G cell coverage; the 5GC deploys IMS, but the capabilities of the terminal device do not support voice services based on the 5G network. In such an implementation, the terminal device 140 may drop (fallback) the voice traffic back to the 4G network by switching or redirecting to the 4G cell (e.g., cell 112 employing the 4G RAT) before the voice call is established, to ensure that the voice traffic is ongoing. Alternatively, the terminal device 140 may switch to a 3G or 2G cell (e.g., cell 112 employing a 3G or 2G RAT) using single wireless voice call continuity (Single Radio Voice Call Continuity, SRVCC) to drop voice traffic back to the 3G or 2G network. After the terminal device 140 completes the voice service and deletes the voice service bearer in the 4G, 3G or 2G network, if it is determined that there is no service that cannot be switched on the terminal device 140, a fast return (fast return) procedure is triggered, so that the terminal device 140 is re-connected to the 5G cell.

It can be seen that the voice traffic flow involves a first intersystem handover from a 5G cell to a 4G, 3G or 2G cell, and a second intersystem handover from a 4G, 3G or 2G cell to a 5G cell.

Similarly, an Inter-system Ping-pong (Inter-system Ping-pong) event also involves two Inter-system handovers. Specifically, an intersystem ping-pong event is defined as follows: the terminal device is handed over from a cell in the source system, e.g. a 5G system, to a cell in a target system different from the source system, e.g. an evolved packet system (Evolved Packet System, EPS), and then within a predefined limited time the terminal device is handed over back to the cell in the source system, while the coverage of the source system is sufficient for the service used by the terminal device. This event may occur more than once. After determining that the inter-system ping-pong event occurs, the access network device after the second inter-system handover indicates the inter-system ping-pong event to the source access network device. Accordingly, the source access network device may perform optimization of the intersystem handover parameters, e.g., increase the threshold for intersystem handover, to avoid the intersystem ping-pong event from reoccurring.

As can be appreciated from the above description, the inter-system ping-pong event is directed to the case that the coverage quality of the source system cell meets the service requirement, but the inter-system handover is performed due to unreasonable setting of the inter-system handover parameters, and then the handover is triggered to the source system due to the coverage quality. The two intersystem handovers in the voice traffic flow are triggered by the ongoing communication traffic flow, irrespective of the coverage and intersystem handover parameters. Therefore, in order to avoid the optimization of the inter-system handover parameters, which are redundant due to invalid triggering of the normal communication traffic flow of the terminal device, it is necessary to treat the communication traffic flow differently from the inter-system ping-pong event.

At least in view of the above-mentioned problems, and potentially other related problems, the present application proposes a communication method. By providing an indication of the cause of the cell change to the access network device after the second intersystem handover to indicate that the first intersystem cell change or the second intersystem cell change is associated with the communication service of the terminal device, the access network device may determine that the two intersystem cell changes are independent of an intersystem ping-pong event. Possible implementations of the present application will be described in detail below with reference to fig. 3 to 15.

Fig. 3 shows a signaling interaction diagram of an example communication process 300 according to a possible implementation of the present application. For purposes of discussion, the communication process 300 will be described with reference to the various elements shown in FIG. 1. However, it should be understood that the communication procedure 300 may also be performed between an access network device and a terminal device in any other communication scenario.

As shown in fig. 3, the terminal device 140 obtains (310) a cell change cause indication indicating that a first cell change of the terminal device 140 from the source cell 132 to the first target cell 112 or a second cell change from the first target cell 112 to the second target cell 122 is associated with communication traffic of the terminal device 140. The first target cell 112 employs a first RAT, and the source cell 132 and the second target cell 122 employ a second RAT different from the first RAT.

As previously mentioned, a "cell change" may also be referred to as a "cell change", and the manner in which a cell change or cell change is performed may include a handover or redirection. Thus, in one implementation, the cell change cause indication may be a handover cause indication.

The terminal device 140 sends (320) a cell change cause indication to the second target access network device 120 to which the second target cell 122 belongs. Accordingly, the second target access network device 120 receives (325) the cell change cause indication. Further, the second target access network device 120 determines (330) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Therefore, the second target access network device 120 may not indicate an intersystem ping-pong event to the source access network device 130, so that optimization of an intersystem handover parameter that is invalid and redundant due to triggering may be avoided, system resources may be saved, and communication efficiency may be improved.

In one possible implementation, the cell change cause indication may indicate at least one of: the first cell change is associated with a voice fallback procedure of the terminal device 140 from the source cell 132 to the first target cell 112, and the second cell change is associated with a quick return procedure of the terminal device 140 from the first target cell 112 to the second target cell 122.

In one possible implementation, the terminal device 140 may further obtain at least one of the following: an indication of the type of the voice fallback procedure and an indication of the cell change execution mode. The indication of the type of the voice fallback procedure may indicate that the voice fallback procedure is an evolved packet system voice fallback (EPS fallback) procedure or an inter-radio access technology voice fallback (Inter RAT fallback) procedure. The cell change execution may include a handover or redirection.

In one possible implementation, the first RAT may be one of 2G, 3G, and 4G RATs and the second RAT may be a 5G RAT. In another possible implementation, the first RAT may be a 2G or 3G RAT and the second RAT may be a 4G RAT.

In one possible implementation, the terminal device 140 may obtain the cell change cause indication from the source access network device 130 to which the source cell 132 belongs. In such implementations, the terminal device 140 may receive a first cell change command associated with the first cell change from the source access network device 130, which may include a cell change cause indication. This will be described with reference to fig. 4.

Fig. 4 shows a signaling interaction diagram of an example communication process 400 according to a possible implementation of the present application. For purposes of discussion, the communication process 400 will be described with reference to the various elements shown in fig. 2B. Communication process 400 may be viewed as an example implementation of communication process 300. In the communication procedure 400, the terminal device 140 performs an initial VoNR voice service setup or is in a VoNR voice service.

In one possible implementation, to establish a VoNR voice service, the terminal device 140 may send a request message to the 5gc 150 to request establishment of a voice session. The 5gc 150, upon receiving the request message, may forward it to the source access network device 130. The request message may instruct the source access network device 130 to establish a voice specific bearer with a 5G quality of service indicator (5G Quality of Service Indicator,5QI) of 1. If the source cell 132 does not support VoNR, then at 410 the source access network device 130 may reply with a rejection message to the 5GC 150 and indicate a voice fallback, and may determine a target access network device (e.g., the first target access network device 110) for the cell change based on the switching parameter configuration and the capabilities of the terminal device 140.

After determining the first target access network device 110, the source access network device 130 may send a handover request to the 5gc 150 through the NG port, and the 5gc 150 may forward the context information of the terminal device 140 to the EPC 160.EPC 160 may send a handover request to first target access network device 110 over the S1 port. The EPC 160, upon receiving a response message for the handover request from the first target access network device 110, forwards the response message to the 5gc 150. Alternatively, the source access network device 130 may send a handover request to the first target access network device 110 through the X2 port, and the first target access network device 110 may send a response message for the handover request to the source access network device 130 through the X2 port.

Further, the 5gc 150 may send a handover command to the source access network device 130, and the source access network device 130 may send 420 the handover command (i.e., the first handover command) to the terminal device 140. The first handover command includes a cell change cause indication. Accordingly, the terminal device 140 receives (425) the first handover command. The cell change cause indication may indicate that a handover of the terminal device 140 to the first target cell 112 is associated with a voice fallback procedure of the terminal device 140 from the source cell 132 to the first target cell 112.

In one possible implementation, the first handover command from the source access network device 130 may include, but is not limited to: mobility command from NR (Mobility from NR Command).

In one possible implementation, to reduce signaling overhead, the source access network device 130 may send the cell change cause indication in association with information of the first target cell 112 in a first handover command. The information of the first target cell 112 may include, for example, but is not limited to, an Identification (ID) of the first target cell 112.

The terminal device 140 then changes (430) to the first target cell 112 to establish VoLTE traffic. For example, a tracking area update (Tracking Area Update, TAU) procedure may be initiated between the terminal device 140 and the EPC 160 so that the EPC 160 may trigger establishment of a voice specific bearer with a QoS class identity (QoS Class Identifier, QCI) of 1.

Further, the terminal device 140 may record the cell change cause indication in history information of the terminal device 140. For example, the terminal device 140 may record the cell change cause indication in association with the related information of the first target cell 112. Alternatively, the terminal device 140 may record the cell change cause indication in association with the related information of the source cell 132.

In one possible implementation, the terminal device 140 may also record an indication of the type of voice fallback procedure in the history information of the terminal device 140. The indication of the type of the voice fallback procedure may indicate that the voice fallback procedure is an EPS voice fallback procedure or an Inter RAT voice fallback procedure. For example, as shown in fig. 2B, in an implementation in which access network devices 120 and 130 employing 5G RATs are connected to 5gc 150, respectively, and access network device 110 employing 4G RATs is connected to EPC 160, the indication of the type of voice fallback procedure may indicate that the voice fallback procedure is an EPS voice fallback procedure. As another example, as shown in fig. 2A, in an implementation in which access network devices 120 and 130 employing a 5G RAT and access network device 110 employing a 4G RAT are both connected to 5gc 150, the indication of the type of voice fallback procedure may indicate that the voice fallback procedure is an Inter RAT voice fallback procedure.

In another possible implementation, the terminal device 140 may also record an indication of the cell change execution mode in the history information of the terminal device 140. The indication of the manner of execution of the cell change may indicate whether the terminal device 140 is executing the cell change by handover or redirection.

In yet another possible implementation, the terminal device 140 may also record a joint indication of the type of the voice fallback procedure and the cell change execution mode in the history information of the terminal device 140. For example, the joint indication may indicate one of: the terminal device 140 performs an EPS voice fallback procedure through handover, an EPS voice fallback procedure through redirection, an Inter RAT voice fallback procedure through handover, and an Inter RAT voice fallback procedure through redirection.

After the voice service is over, the first target access network device 110 determines (440) a target access network device for the cell change. For example, the first target access network device 110 may determine the second target access network device 120 as a target access network device for cell change based on coverage quality information of the primary serving cell and the heterogeneous neighbor cell reported by the terminal device 140. Subsequently, the terminal device 140 performs (450) a handover from the first target cell 112 managed by the first target access network device 110 to the second target cell 122 managed by the second target access network device 120.

After terminal device 140 accesses second target cell 122, second target access network device 120 sends (460) a request to terminal device 140 for history information for terminal device 140. In response to receiving (465) the request, the terminal device 140 sends (470) history information of the terminal device 140 to the second target access network device 120, the history information comprising an indication of a cause of the cell change. Accordingly, second target access network device 120 receives 476 the history information of terminal device 140.

In one possible implementation, the terminal device 140 may store information of the cell in which the terminal device 140 resides as part of the user history information (UE History Information, UHI). The information of the camped cell may include, for example, an identity of the camped cell, a residence time, etc. In such an implementation, the terminal device 140 may include the cell change cause indication obtained from the source access network device 130 in UHI. For example, the terminal device 140 may store the cell change cause indication in association with information of the first target cell 112 to indicate that a cell change to the first target cell 112 is associated with a voice fallback procedure of the terminal device 140 from the source cell 132 to the first target cell 112. In such an implementation, terminal device 140 may cause second target access network device 120 to obtain history information for terminal device 140 by sending UHI to second target access network device 120, which UHI includes an indication of the cause of the cell change. Alternatively, the terminal device 140 may store the cell change cause indication in association with information of the source cell 132 to indicate that the change-out source cell 132 is associated with a voice fallback procedure of the terminal device 140 from the source cell 132 to the first target cell 112.

Upon receiving the indication of the cause of the cell change, the second target access network device 120 determines (330) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, or based on the indication of the cause of the cell change and a residence time at the first target cell. Thus, the second target access network device 120 may not indicate an intersystem ping-pong event to the source access network device 130, such that triggering the source access network device 130 to adjust handover parameters based on the intersystem ping-pong event may be avoided. In addition, the processing time of the source access network equipment is occupied by the adjustment of the switching parameters under the condition that the switching between the two systems is irrelevant to the ping-pong event between the systems, so that the communication efficiency can be improved by adopting the scheme of the application.

In another possible implementation, the second target access network device 120 may not perform act 330, i.e., not determine (330) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Alternatively, the second target access network device 120 may send the cell change cause indication to the source access network device 130 to which the source cell belongs. For example, the second target access network device 120 may generate an inter-system ping-pong report that includes an indication of the cause of the cell change. The second target access network device 120 may send the intersystem ping report to the source access network device 130 by one of the following messages: a handover report message for the Xn port, or an uplink RAN configuration transfer (uplink RAN configuration transfer) message, a downlink RAN configuration transfer message (downlink RAN configuration transfer) message for the NG port. Upon receiving the indication of the cause of the cell change, the source access network device 130 may determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, so that no mobile parameter optimization is performed.

In addition to obtaining the cell change cause indication from the source access network device 130, in one possible implementation, the terminal device 140 may also obtain the cell change cause indication from the first target access network device 110. In such an implementation, the terminal device 140 receives a second handover command associated with the second cell change from the first target access network device 110, the second handover command including the cell change cause indication. This will be described with reference to fig. 5.

Fig. 5 shows a signaling interaction diagram of an example communication process 500 according to a possible implementation of the present application. For purposes of discussion, the communication process 500 will be described with reference to various elements shown in fig. 2B. Communication process 500 may be viewed as another example implementation of communication process 300. In the communication process 500, the terminal device 140 performs an initial VoNR voice service setup or is in a VoNR voice service. Acts in communication process 500, such as 410, 430, 440, 430, 465, 470, 475, and 330, are similar to corresponding acts in communication process 400 and are not described in further detail. The communication procedure 500 differs from the communication procedure 400 in that the first handover command received (510) by the terminal device 140 from the source access network device 130 does not include an indication of the cause of the cell change. Alternatively, the terminal device 140 receives (560) the second handover command from the first access network device 110, including the cell change cause indication.

Specifically, after the voice traffic of terminal device 140 ends and first target access network device 110 determines 440 a target access network device for the cell change (e.g., second target access network device 120), first target access network device 110 sends 520 a handover request to EPC 160 requesting quick return of terminal device 140 to second target cell 122 of second target access network device 120. The EPC 160 receives (525) the handover request and then sends (530) the handover request to the 5gc 150. Optionally, EPC 160 may send the context information of terminal device 140 to 5gc 150 along with the handover request. After receiving (535) the handover request, the 5gc 150 sends (540) the handover request to the second target access network device 120 to inform the second target access network device 120 that it is ready for handover. Upon receiving (545) the handover request, the second target access network device 120 sends a handover preparation complete message (not shown) to the 5gc 150, and the 5gc 150 forwards the handover preparation complete message (not shown) to the EPC 160.

Upon receiving the handover preparation complete message, EPC 160 transmits (550) a handover command to first target access network device 110 to handover from first target cell 112 to second target cell 122. Upon receiving (555) the handover command, the first target access network device 110 sends (560) a handover command (i.e., a second handover command) to the terminal device 140 to handover from the first target cell 112 to the second target cell 122. The second handover command includes a cell change cause indication to indicate that a handover to the second target cell 122 is associated with a fast return procedure.

In one possible implementation, the second handover command from the first target access network device 110 may include, but is not limited to: mobility command (Mobility from EUTRA Command) from Evolved universal mobile telecommunications system terrestrial radio access (EUTRA) UMTS Terrestrial Radio Access.

In one possible implementation, to reduce signaling overhead, the first target access network device 110 may send the cell change cause indication in association with information about the second target cell 122 in a second handover command.

Upon receiving (565) the second handover command, the terminal device 140 may record the cell change cause indication in history information of the terminal device 140. For example, the terminal device 140 may record the cell change cause indication in association with the information of the second target cell 122. For example, in order to record the cell change cause indication in association with the information of the second target cell 122, the cell change cause indication and the information of the second target cell 122 may be recorded in one entry of the list.

In one possible implementation, in response to receiving (565) a second handover command including a cell change cause indication, terminal device 140 may send a radio resource control reconfiguration complete (rrcr configuration complete) message to second target access network device 120 including the cell change cause indication to indicate to second target access network device 120 that a change to second target cell 122 is associated with a voice fallback procedure or a quick return procedure.

In another possible implementation, similar to process 400, in process 500, second target access network device 120 may not perform act 330, i.e., determine (330) that the first cell change and the second cell change are independent of an intersystem ping pong event, not based on the cell change cause indication. Alternatively, the second target access network device 120 may send the cell change cause indication to the source access network device 130 to which the source cell belongs. Upon receiving the indication of the cause of the cell change, the source access network device 130 may determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, so that no mobile parameter optimization is performed.

It should be appreciated that the communication processes 400 and 500 are described above with reference to the various elements shown in fig. 2B. However, at least one of the communication procedures 400 and 500 may also be performed between a terminal device, an access network device and a core network device in any other communication scenario. For example, at least one of the communication procedures 400 and 500 may also be performed between a terminal device, an access network device, and a core network device in the communication network 200A shown in fig. 2A. In such an implementation, messages interacted between the first target access network device 110 and the second target access network device 120 may be forwarded only through the 5gc 150.

The implementation in which the terminal device 140 sends the indication of the cause of the cell change to the second target access network device 120 (i.e. the second target access network device 120 obtains the indication of the cause of the cell change from the terminal device 140) is described above with reference to fig. 3 to 5. In another possible implementation, the second target access network device 120 may also obtain the cell change cause indication from the first target access network device 110. This will be described hereinafter with reference to fig. 6 to 8.

Fig. 6 shows a signaling interaction diagram of an example communication process 600 according to a possible implementation of the present application. For purposes of discussion, the communication process 600 will be described with reference to the various elements shown in fig. 1. However, it should be appreciated that the communication process 600 may also be performed between an access network device and a terminal device in any other communication scenario.

As shown in fig. 6, the first target access network device 110 obtains (610) a cell change cause indication indicating that a first cell change of the terminal device 140 from the source cell 132 to the first target cell 112 or a second cell change from the first target cell 112 to the second target cell 122 is associated with communication traffic of the terminal device 140. The first target cell 112 employs a first RAT, and the source cell 132 and the second target cell 122 employ a second RAT different from the first RAT.

The first target access network device 110 sends 620 an indication of the cause of the cell change to the second target access network device 120. Accordingly, the second target access network device 120 receives (625) the cell change cause indication. Further, the second target access network device 120 determines (630) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, or based on the indication of the cause of the cell change and the residence time in the first target cell. Thus, the second target access network device 120 may not indicate an intersystem ping event to the source access network device 130, so that optimization of the intersystem handover parameters that trigger invalidation and redundancy may be avoided.

In another possible implementation, second target access network device 120 may not perform act 630. Alternatively, the second target access network device 120 may send the cell change cause indication to the source access network device 130 to which the source cell belongs. For example, the second target access network device 120 may generate an inter-system ping-pong report that includes an indication of the cause of the cell change. The second target access network device 120 may send the intersystem ping report to the source access network device 130 by one of the following messages: a handover report message for the Xn port, or an uplink RAN configuration transfer (uplink RAN configuration transfer) message, a downlink RAN configuration transfer message (downlink RAN configuration transfer) message for the NG port. Upon receiving the indication of the cause of the cell change, the source access network device 130 may determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, so that no mobile parameter optimization is performed.

In one possible implementation, the first target access network device 110 may obtain the cell change cause indication from the source access network device 130 to which the source cell 132 belongs. In such an implementation, the first target access network device 110 may obtain the history information of the terminal device 140 from the source access network device 130. The history information may include information of the cell in which the terminal device 140 resides, the residence time, and an indication of the cause of the cell change. This will be described with reference to fig. 7.

Fig. 7 shows a signaling interaction diagram of an example communication process 700 according to a possible implementation of the present application. For purposes of discussion, the communication process 700 will be described with reference to various elements shown in fig. 2B. Communication process 700 may be viewed as an example implementation of communication process 600.

In the communication procedure 700, the source access network device 130 records history information of the terminal device 140, including an indication of the cause of the cell change. For example, the source access network device 130 may store the history information of the terminal device 140 as UHI, which UHI contains an indication of the cause of the cell change. Further, the first target access network device 110 acquires UHI including the cell change cause indication from the source access network device 130 via a handover request from the source cell 132 to the first target cell 112. After the terminal device 140 completes the voice service in the first target cell 112, the first target access network device 110 in turn provides the UHI containing the indication of the cause of the cell change to the second target access network device 120 via a handover request from the first target cell 112 to the second target cell 122.

Specifically, similar to the communication process 400, in the communication process 700, the terminal device 140 performs initial VoNR voice service establishment or is in VoNR voice service. Act 410 in communication process 700 is similar to act 410 in communication process 400 and thus will not be described in detail.

After determining (410) the target access network device (e.g., the first target access network device 110) for the cell change, the source access network device 130 records (710) the history information of the terminal device 140. The history information includes an indication of a cause of the cell change. In one possible implementation, the source access network device 130 may store the cell change cause indication as part of UHI. For example, the source access network device 130 may store the cell change cause indication in association with information of the source cell 132 to indicate that the cause of the terminal device 140 changing out of the source cell 132 of the source access network device 130 is associated with a voice fallback procedure from the source cell 132 to the first target cell 112 of the first target access network device 110. Alternatively, the source access network device 130 may store the cell change cause indication in association with information of the first target cell 112 to indicate that the cause of the terminal device 140 changing to the first target cell 112 is associated with a voice fallback procedure from the source cell 132 to the first target cell 112.

Further, the source access network device 130 sends (720) a handover request from the source cell 132 to the first target cell 112 to the 5gc 150. The handover request includes UHI of the terminal device 140 and the UHI includes an indication of the cause of the cell change. After receiving (725) the handover request, the 5gc 150 sends (730) the handover request to the EPC 160. The handover request includes UHI of the terminal device 140 and the UHI includes an indication of the cause of the cell change. After receiving (735) the handover request, EPC 160 sends (740) the handover request to first target access network device 110 to inform first target access network device 110 that a handover is ready. The handover request includes UHI of the terminal device 140 and the UHI includes an indication of the cause of the cell change. The first target access network device 110 receives (745) the handover request and sends a handover preparation complete message (not shown) to the EPC 160, and the EPC 160 forwards the handover preparation complete message (not shown) to the 5gc 150.

Alternatively, in another possible implementation, the source access network device 130 may not send the handover request to the first target access network device 110 through the 5gc 150 and the EPC 160, but send the handover request to the first target access network device 110 through the X2 port.

In addition, in another possible implementation, the UHI may further include an indication of the manner in which the cell change is performed. The indication of the manner in which the cell change is performed may indicate whether the cell change is performed by a handover or a redirection.

In addition, in another possible implementation manner, the UHI may further include an indication of a type of the voice fallback procedure, so as to indicate that the voice fallback procedure is an EPS voice fallback procedure or an Inter RAT voice fallback procedure.

In yet another possible implementation, the UHI may further include a joint indication of the type of voice fallback procedure and the manner in which the cell change is performed. For example, the joint indication may indicate one of: the method comprises the steps of an EPS voice fallback flow executed through switching, an EPS voice fallback flow executed through redirection, an Inter-RAT voice fallback flow executed through switching and an Inter-RAT voice fallback flow executed through redirection.

Upon receiving the handover preparation complete message, the 5gc 150 transmits a handover command (not shown in the figure) for handover from the source cell 132 to the first target cell 112 to the source access network device 130. Upon receiving the handover command, the source access network device 130 transmits a handover command (not shown in the figure) for handover from the source cell 132 to the first target cell 112 to the terminal device 140. In response to receiving the handover command, the terminal device 140 hands over (430) from the source cell 132 to the first target cell 112 to establish VoLTE traffic. Act 430 in communication process 700 is similar to act 430 in communication process 400 and thus will not be described in detail.

After the voice service is over, the first target access network device 110 determines 440 a target access network device (e.g., second target access network device 120) for the cell change. Act 440 in communication process 700 is similar to act 440 in communication process 400 and thus will not be described in detail.

Further, the first target access network device 110 sends (750) a handover request to the EPC 160 from the first target cell 112 of the first target access network device 110 to the second target cell 122 of the second target access network device 120 requesting a quick return of the terminal device 140 to the second target cell 122. The handover request includes an indication of a cause of the cell change. The EPC 160, upon receiving (755) the handover request, sends (760) the handover request to the 5gc 150. The handover request includes UHI of the terminal device 140 and the UHI includes an indication of the cause of the cell change. Optionally, EPC 160 may send the context information of terminal device 140 to 5gc 150 along with the handover request. After receiving (765) the handover request, 5gc 150 sends (770) the handover request to second target access network device 120 to inform second target access network device 120 that it is ready for handover. The handover request includes UHI of the terminal device 140 and the UHI includes an indication of the cause of the cell change. Upon receiving (775) the handover request, the second target access network device 120 sends a handover preparation complete message (not shown) to the 5gc 150, and the 5gc 150 forwards the handover preparation complete message (not shown) to the EPC 160.

Upon receiving the handover preparation complete message, EPC 160 transmits a handover command (not shown in the figure) for handover from first target cell 112 to second target cell 122 to first target access network device 110. Upon receiving the handover command, the first target access network device 110 sends a handover command (not shown in the figure) to the terminal device 140 for handover from the first target cell 112 to the second target cell 122. In response to receiving the handover command, the terminal device 140 is handed over from the first target cell 112 to the second target cell 122.

After terminal device 140 hands over to second target cell 122, second target access network device 120 determines (780) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Thus, second target access network device 120 may not indicate an intersystem ping event to source access network device 130, such that triggering source access network device 130 to adjust intersystem handover parameters may be avoided.

In another possible implementation, similar to process 400, in process 700, second target access network device 120 may not perform act 780, i.e., determine that the first cell change and the second cell change are independent of an intersystem ping pong event, not based on the cell change cause indication. Alternatively, the second target access network device 120 may send the cell change cause indication to the source access network device 130 to which the source cell belongs. Upon receiving the indication of the cause of the cell change, the source access network device 130 may determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, so that no mobile parameter optimization is performed.

An implementation in which the source access network device 130 records history information of the terminal device 140 and the history information includes an indication of the cause of the cell change is described above with reference to fig. 7. Alternatively, in another possible implementation, the first target access network device 110 may record history information of the terminal device 140 and the history information includes a cell change cause indication. This will be described with reference to fig. 8.

Fig. 8 shows a signaling interaction diagram of an example communication process 800 according to a possible implementation of the present application. For purposes of discussion, the communication process 800 will be described with reference to various elements shown in fig. 2B. Communication process 800 may be viewed as another example implementation of communication process 600.

In the communication process 800, the first target access network device 110 records history information of the terminal device 140, including an indication of the cause of the cell change. Further, after the terminal device 140 completes the voice service in the first target cell 112, the first target access network device 110 provides the cell change cause indication to the second target access network device 120 via a handover request from the first target cell 112 to the second target cell 122.

Specifically, similar to the communication process 400, in the communication process 800, the terminal device 140 performs initial VoNR voice service establishment or is in VoNR voice service. Act 410 in communication process 800 is similar to act 410 in communication process 400 and thus will not be described in detail.

After determining (410) the target access network device (e.g., first target access network device 110) for the cell change, the source access network device 130 sends (810) a handover request from the source cell 132 to the first target cell 112 to the 5gc 150. Unlike the communication procedure 700, the indication of the cause of the cell change is not included in UHI in the handover request from the source access network device 130. Further, the 5gc 150 sends (820) the handover request to the EPC 160. The EPC 160 then sends (830) the handover request to the first target access network device 110 to inform the first target access network device 110 that a handover preparation is made. The first target access network device 110 receives the handover request and sends a handover preparation complete message (not shown) to the EPC 160, and the EPC 160 forwards the handover preparation complete message (not shown) to the 5gc 150.

Upon receiving the handover preparation complete message, the 5gc 150 transmits a handover command (not shown in the figure) for handover from the source cell 132 to the first target cell 112 to the source access network device 130. Upon receiving the handover command, the source access network device 130 transmits a handover command (not shown in the figure) for handover from the source cell 132 to the first target cell 112 to the terminal device 140. In response to receiving the handover command, the terminal device 140 hands over (430) from the source cell 132 to the first target cell 112 to establish VoLTE traffic. Act 430 in communication process 800 is similar to act 430 in communication process 400 and thus will not be described in detail.

After the voice service is over, the first target access network device 110 determines 440 a target access network device (e.g., second target access network device 120) for the cell change. Act 440 in communication process 800 is similar to act 440 in communication process 400 and thus will not be described in detail.

Further, the first target access network device 110 records 840 the history information of the terminal device 140. The history information includes an indication of a cause of the cell change. In one possible implementation, the first target access network device 110 may store the cell change cause indication in UHI. For example, the first target access network device 110 may store the cell change cause indication in association with information of the first target cell 112 to indicate that the cause of the change of the terminal device 140 from the first target cell 112 is associated with a quick return procedure from the first target cell 112 to the second target cell 122.

Further, the first target access network device 110 sends (850) a handover request to the EPC 160 from the first target cell 112 of the first target access network device 110 to the second target cell 122 of the second target access network device 120 requesting a quick return of the terminal device 140 to the second target cell 122. The handover request includes an indication of a cause of the cell change. The EPC 160, upon receiving (855) the handover request, sends (860) the handover request to the 5gc150. The handover request includes an indication of a cause of the cell change. Optionally, EPC 160 may send the context information of terminal device 140 to 5GC150 along with the handover request. After receiving (865) the handover request, the 5gc150 sends (880) the handover request to the second target access network device 120 to inform the second target access network device 120 that it is ready for handover. The handover request includes an indication of a cause of the cell change.

In one possible implementation, the first target access network device 110 may include the cell change cause indication in UHI of the terminal device 140, and in turn include UHI in the handover request from the first target cell 112 to the second target cell 122 for transmission to the second target access network device 120.

In another possible implementation, the first target access network device 110 may include the cell change cause indication in a cell or field other than UHI, which in turn is included in the handover request from the first target cell 112 to the second target cell 122 for transmission to the second target access network device 120. For example, the cell or field may be a cell dedicated to carrying an indication of a cause of a cell change, the scope of the application is not limited in this respect.

Upon receiving (875) the handover request, the second target access network device 120 sends a handover preparation complete message (not shown) to the 5gc 150, and the 5gc 150 forwards the handover preparation complete message (not shown) to the EPC 160.

After terminal device 140 switches to second target cell 122, second target access network device 120 determines (880) that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Thus, second target access network device 120 may not indicate an intersystem ping event to source access network device 130, such that triggering source access network device 130 to adjust intersystem handover parameters may be avoided.

In another possible implementation, similar to process 400, in process 800, second target access network device 120 may not perform act 880, i.e., determine that the first cell change and the second cell change are independent of an intersystem ping pong event, not based on the cell change cause indication. Alternatively, the second target access network device 120 may send the cell change cause indication to the source access network device 130 to which the source cell belongs. Upon receiving the indication of the cause of the cell change, the source access network device 130 may determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the indication of the cause of the cell change, so that no mobile parameter optimization is performed.

It should be appreciated that the communication processes 700 and 800 are described above with reference to the various elements shown in fig. 2B. However, at least one of the communication procedures 700 and 800 may also be performed between a terminal device, an access network device and a core network device in any other communication scenario. For example, at least one of the communication procedures 700 and 800 may also be performed between a terminal device, an access network device, and a core network device in the communication network 200A shown in fig. 2A. In such an implementation, messages interacted between the first target access network device 110 and the second target access network device 120 may be forwarded only through the 5gc 150.

It will be understood that the various possible implementations of the application described above may be referred to each other, and that like terms have like meanings unless specifically indicated.

Fig. 9 shows a flow chart of a communication method 900 according to one possible implementation of the present application. In one possible implementation, the method 900 may be implemented by the terminal device 140 in the example communication network 100, 200A, or 200B, for example, by a processor or processing unit of the terminal device 140 in combination with other components (e.g., a transceiver). In other possible implementations, the method 900 may also be implemented by other communication devices independent of the example communication network 100, 200A, or 200B.

At block 910, the terminal device 140 obtains a cell change cause indication. The cell change cause indication indicates that a first cell change of the terminal device 140 from the source cell to the first target cell or a second cell change of the terminal device 140 from the first target cell to the second target cell is associated with the communication traffic of the terminal device 140. The first target cell employs a first RAT, and the source cell and the second target cell employ a second RAT different from the first RAT.

At block 920, the terminal device 140 sends a cell change cause indication to the second target access network device to which the second target cell belongs. Therefore, the second target access network device can treat the communication service flow and the intersystem ping-pong event differently, so that optimization of redundant intersystem handover parameters caused by invalid triggering of the normal communication service flow of the terminal device 140 is avoided.

In one possible implementation, the terminal device 140 obtaining the indication of the cause of the cell change includes the terminal device 140 obtaining the indication of the cause of the cell change from a source access network device to which the source cell belongs.

In one possible implementation, the terminal device 140 obtaining the indication of the cause of the cell change from the source access network device includes: the terminal device 140 receives a first cell change command associated with a first cell change from the source access network device, the first cell change command comprising a cell change cause indication. Sending the cell change cause indication to the terminal device 140 via the first cell change command may avoid additional signaling overhead.

In one possible implementation, the obtaining, by the terminal device 140, the indication of the cause of the cell change includes: the terminal device 140 obtains the indication of the cause of the cell change from the first target access network device to which the first target cell belongs.

In one possible implementation, the terminal device 140 obtaining the indication of the cause of the cell change from the first target access network device includes: the terminal device 140 receives a second cell change command associated with a second cell change from the first target access network device, the second cell change command comprising a cell change cause indication. Sending the cell change cause indication to the terminal device 140 via the second cell change command may avoid additional signaling overhead.

In one possible implementation, the sending, by the terminal device 140, the indication of the cause of the cell change to the second target access network device includes: the terminal device 140 receives a request for history information of the terminal device 140 from the second target access network device; and the terminal device 140 sends history information to the second target access network device, the history information including an indication of a cause of the cell change. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

Fig. 10 shows a flow chart of a communication method 1000 according to one possible implementation of the present application. In one possible implementation, the method 1000 may be implemented by the first access network device 110 in the example communication network 100, 200A, or 200B, for example, by a processor or processing unit of the first access network device 110 in conjunction with other components (e.g., a transceiver). In other possible implementations, the method 1000 may also be implemented by other communication devices independent of the example communication network 100, 200A, or 200B.

At block 1010, the first target access network device 110 obtains an indication of a cause of the cell change. The cell change cause indication indicates that a first cell change of the terminal device from the source cell to a first target cell of the first target access network device 110 or a second cell change of the terminal device from the first target cell to a second target cell is associated with a communication service of the terminal device. The first target cell employs a first RAT, and the source cell and the second target cell employ a second RAT different from the first RAT.

At block 1020, the first target access network device 110 provides an indication of the cause of the cell change to a second target access network device to which the second target cell belongs.

In one possible implementation, the obtaining, by the first target access network device 110, the indication of the cause of the cell change includes: the first target access network device 110 obtains a cell change cause indication from the source access network device to which the source cell belongs.

In one possible implementation, the first target access network device 110 obtaining the cell change cause indication from the source access network device includes: the first target access network device 110 obtains history information of the terminal device from the source access network device, where the history information includes an indication of a cause of a cell change. Sending the cell change cause indication to the first target access network device 110 together with the history information may avoid additional signaling overhead.

In one possible implementation, the providing, by the first target access network device 110, the indication of the cause of the cell change to the second target access network device 120 includes: the first target access network device 110 provides the second target access network device 120 with second history information of the terminal device 140, the second history information including an indication of a cause of the cell change, the second history information including the first history information, and/or third history information of the terminal device recorded by the first target access network device. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, the providing, by the first target access network device 110, the indication of the cause of the cell change to the second target access network device includes: the first target access network device 110 provides a handover request for the second cell change to the second target access network device, the handover request comprising a cell change cause indication. Sending the cell change cause indication with the handover request to the second target access network device may avoid additional signaling overhead.

Fig. 11 shows a flow chart of a communication method 1100 according to one possible implementation of the present application. In one possible implementation, the method 1100 may be implemented by the second access network device 120 in the example communication network 100, 200A, or 200B, for example, by a processor or processing unit of the second access network device 120 in combination with other components (e.g., a transceiver). In other possible implementations, the method 1100 may also be implemented by other communication devices independent of the example communication network 100, 200A, or 200B.

At block 1110, the second target access network device 120 obtains an indication of the cause of the cell change. The cell change cause indication indicates that a first cell change of the terminal device from the source cell to the first target cell or a second cell change of the second target cell from the first target cell to the second target access network device 120 is associated with the communication traffic of the terminal device. The first target cell employs a first RAT, and the source cell and the second target cell employ a second RAT different from the first RAT.

At block 1120, the second target access network device 120 determines that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication. Therefore, the second target access network device 120 can treat the communication service flow and the inter-system ping-pong event differently, so that the optimization of the redundant inter-system switching parameters caused by invalid normal communication service flow triggering of the terminal device is avoided.

In one possible implementation, the second target access network device 120 obtaining the indication of the cause of the cell change includes: and acquiring the indication of the cell change reason from the terminal equipment.

In one possible implementation, the second target access network device 120 obtaining the cell change cause indication from the terminal device includes: sending a request for history information of the terminal equipment to the terminal equipment; and receiving history information from the terminal device, the history information including an indication of a cause of the cell change. Sending the cell change cause indication to the second target access network device 120 along with the history information may avoid additional signaling overhead.

In one possible implementation, obtaining the indication of the cause of the cell change from the source access network device includes: and acquiring historical information of the terminal equipment from the source access network equipment, wherein the historical information comprises cell change reason indication. Sending the cell change cause indication to the second target access network device 120 along with the history information may avoid additional signaling overhead.

In one possible implementation, obtaining the indication of the cause of the cell change from the first target access network device includes: and acquiring second history information of the terminal equipment from the first target access network equipment, wherein the second history information comprises cell change reason indication, and the second history information comprises first history information of the terminal equipment acquired by the first target access network equipment from source access network equipment to which a source cell belongs and/or third history information of the terminal equipment recorded by the first target access network equipment. Sending the cell change cause indication to the second target access network device 120 along with the history information may avoid additional signaling overhead.

In one possible implementation of the method 900, 1000 or 1100, the cell change cause indication includes: the reason why the terminal device changes out of the source cell or out of the first target cell, and/or the reason why the terminal device changes to the first target cell or to the second target cell.

In one possible implementation of the method 900, 1000 or 1100, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; and the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell. Therefore, the optimization of the redundant intersystem switching parameters caused by invalid voice service flow triggering of the terminal equipment is avoided.

In one possible implementation of the method 900, 1000, or 1100, the voice fallback procedure includes a normal call voice fallback procedure or an emergency call voice fallback procedure, and the quick return procedure includes a normal call voice quick return procedure or an emergency call voice quick return procedure.

In one possible implementation of the method 900, 1000 or 1100, the first RAT is one of a 2G RAT, a 3G RAT and a 4G RAT, and the second RAT is a 5G RAT.

By using the method 900, 1000 or 1100, the optimization of the inter-system switching parameters which are invalid and redundant can be avoided, the system resources are saved, and the communication efficiency is improved.

Details of possible implementations of the present application described above with reference to fig. 1 to 8 are equally applicable to methods 900, 1000 and 1100, and thus are not repeated.

Fig. 12 shows a schematic block diagram of a communication device 1200 according to one possible implementation of the present application. The communications apparatus 1200 may be implemented as a device or chip in a device, as the scope of the application is not limited in this respect. The communications apparatus 1200 can include a plurality of modules for performing corresponding steps in the method 900 as discussed in fig. 9. The communication apparatus 1200 may be implemented as the terminal device 140 or as a part of the terminal device 140 as shown in fig. 1, 2A or 2B.

As shown in fig. 12, the communication apparatus 1200 includes an acquisition unit 1210 and a transmission unit 1220. The acquisition unit 1210 is configured to acquire a cell change cause indication. The cell change cause indication indicates that a first cell change of the terminal device from the source cell to a first target cell or a second cell change of the terminal device from the first target cell to a second target cell is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The transmitting unit 1220 is configured to transmit a cell change cause indication to a second target access network device to which the second target cell belongs.

In one possible implementation, the obtaining unit 1210 is configured to obtain the indication of the cause of the cell change from a source access network device to which the source cell belongs.

In one possible implementation, the acquisition unit 1210 is configured to receive a first cell change command associated with a first cell change from the source access network device, the first cell change command comprising a cell change cause indication. Sending the cell change cause indication to the communication device 1200 via the first cell change command may avoid additional signaling overhead.

In one possible implementation, the obtaining unit 1210 is configured to obtain the indication of the cause of the cell change from a first target access network device to which the first target cell belongs.

In one possible implementation, the obtaining unit 1210 is configured to receive a second cell change command associated with a second cell change from the first target access network device, the second cell change command comprising a cell change cause indication. Sending the cell change cause indication to the communication device 1200 via the second cell change command may avoid additional signaling overhead.

In one possible implementation, the communication apparatus 1200 further includes a receiving unit. The receiving unit is configured to receive a request for history information of the communication apparatus 1200 from the second target access network device. The sending unit 1220 is configured to send history information to the second target access network device, the history information comprising an indication of a cause of a cell change. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

Fig. 13 shows a schematic block diagram of an access network device 1300 according to one possible implementation of the present application. The access network device 1300 may be implemented as a device or as a chip in a device, the scope of the application being limited in this respect. The access network device 1300 may include a number of modules for performing the corresponding steps in the method 1000 as discussed in fig. 10. The access network device 1300 may be implemented as the first target access network device 110 or as part of the first target access network device 110 as shown in fig. 1, 2A or 2B.

As shown in fig. 13, the access network device 1300 includes an acquisition unit 1310 and a providing unit 1320. The obtaining unit 1310 is configured to obtain a cell change cause indication indicating that a first cell change of the terminal device from the source cell to a first target cell of the access network device 1300 or a second cell change of the terminal device from the first target cell to a second target cell is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The providing unit 1320 is configured to provide an indication of a cause of a cell change to a second target access network device to which the second target cell belongs.

In one possible implementation, the obtaining unit 1310 is configured to obtain the indication of the cause of the cell change from a source access network device to which the source cell belongs.

In one possible implementation, the obtaining unit 1310 is configured to obtain, from the source access network device, history information of the terminal device, where the history information includes an indication of a cause of the cell change. Sending the cell change cause indication to the access network device 1300 along with the history information may avoid additional signaling overhead.

In one possible implementation, the providing unit 1320 is configured to provide the history information of the terminal device to the second target access network device, the history information including the cell change cause indication. Sending the indication of the cause of the cell change to the second target access network device together with the history information may avoid additional signalling overhead.

In one possible implementation, the providing unit 1320 is configured to provide a handover request for the second cell change to the second target access network device, the handover request including the cell change cause indication. Sending the cell change cause indication with the handover request to the second target access network device may avoid additional signaling overhead.

Fig. 14 shows a schematic block diagram of an access network device 1400 according to one possible implementation of the present application. The access network device 1400 may be implemented as a device or chip within a device, the scope of the application being not limited in this respect. The access network device 1400 may include a plurality of modules for performing the corresponding steps in the method 1100 as discussed in fig. 11. The access network device 1400 may be implemented as the second target access network device 120 or as part of the second target access network device 120 as shown in fig. 1, 2A, or 2B.

As shown in fig. 14, the access network device 1400 includes an acquisition unit 1410 and a providing unit 1420. The obtaining unit 1410 is configured to obtain a cell change cause indication indicating that a first cell change of the terminal device from the source cell to the first target cell or a second cell change of the terminal device from the first target cell to the second target cell of the access network device 1400 is associated with a communication service of the terminal device, the first target cell employing a first RAT, the source cell and the second target cell employing a second RAT different from the first RAT. The determining unit 1420 is configured to determine that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication.

In one possible implementation, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; and the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell. Therefore, the optimization of the redundant intersystem switching parameters caused by invalid voice service flow triggering of the terminal equipment is avoided.

In one possible implementation, the obtaining unit 1410 is configured to obtain the indication of the cause of the cell change from the terminal device.

In one possible implementation, the obtaining unit 1410 is configured to send a request for history information of the terminal device to the terminal device; and receiving history information from the terminal device, the history information including an indication of a cause of the cell change. Sending the cell change cause indication to the access network device 1400 along with the history information may avoid additional signaling overhead.

In one possible implementation, the obtaining unit 1410 is configured to obtain the indication of the cause of the cell change from a source access network device to which the source cell belongs.

In one possible implementation, the obtaining unit 1410 is configured to obtain, from the source access network device, history information of the terminal device, where the history information includes an indication of a cause of the cell change. Sending the cell change cause indication to the access network device 1400 along with the history information may avoid additional signaling overhead.

In one possible implementation, the obtaining unit 1410 is configured to obtain the indication of the cause of the cell change from a first target access network device to which the first target cell belongs.

In one possible implementation, the obtaining unit 1410 is configured to obtain, from the first target access network device, history information of the terminal device, where the history information includes an indication of a cause of the cell change. Sending the cell change cause indication to the access network device 1400 along with the history information may avoid additional signaling overhead.

In one possible implementation of the communication apparatus 1200, the access network device 1300 or the access network device 1400, the cell change cause indication includes: the reason why the terminal device changes out of the source cell or out of the first target cell, and/or the reason why the terminal device changes to the first target cell or to the second target cell.

In one possible implementation of the communication apparatus 1200, the access network device 1300 or the access network device 1400, the cell change cause indication indicates at least one of: the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; and the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell. Therefore, the optimization of the redundant intersystem switching parameters caused by invalid voice service flow triggering of the terminal equipment is avoided.

In one possible implementation of the communication apparatus 1200, the access network device 1300, or the access network device 1400, the voice fallback procedure includes a normal call voice fallback procedure or an emergency call voice fallback procedure, such as the communication apparatus initiating a voice service by switching or redirecting fallback from the 5G cell to the LTE cell, and the fast return procedure includes a normal call voice fast return procedure or an emergency call voice fast return procedure, such as the communication apparatus returning from the LET cell to the 5G cell by switching or redirecting after the voice service of the communication apparatus is finished.

In one possible implementation of the communication apparatus 1200, the access network device 1300 or the access network device 1400, the first RAT is one of a 2G RAT, a 3G RAT and a 4G RAT, and the second RAT is a 5G RAT.

Details of the possible implementations of the present application described above with reference to fig. 1 to 11 are equally applicable to the communication apparatus 1200, the access network device 1300 and the access network device 1400, and are therefore not described in detail.

Fig. 15 is a simplified block diagram of an example device 1500 suitable for implementing a possible implementation of the present application. Device 1500 may be used to implement terminal device 140, first target access network device 110, or second target access network device 120 as shown in fig. 1, 2A, or 2B. As shown, the device 1500 includes one or more processors (or processing units) 1510, and may further include one or more memories 1520 coupled to the processor 1510, and may further include a communication interface 1540 coupled to the processor 1510.

Communication interface 1540 may be used to communicate with other devices or apparatuses, such as transmission or reception of data and/or signals. Communication interface 1540 may have at least one communication interface for communicating. The communication interface may include any interface necessary to communicate with other devices. By way of example, the communication interface may be a transceiver, circuit, bus, module, or other type of communication interface.

The processor 1510 may include, but is not limited to, at least one of: one or more of a general purpose computer, a special purpose computer, a microcontroller, a digital signal controller (Digital Signal Processor, DSP), or a controller-based multi-core controller architecture. The device 1500 may have multiple processors, such as application specific integrated circuit chips, that are slaved in time to a clock that is synchronized to the master processor.

Memory 1520 may include one or more non-volatile memories and one or more volatile memories. Examples of non-volatile memory include, but are not limited to, at least one of: read-Only-Memory (ROM) 1524, erasable programmable Read-Only Memory (EPROM), flash Memory, hard disk, compact Disc (CD), digital video Disc (Digital Video Disk, DVD), or other magnetic and/or optical storage. Examples of volatile memory include, but are not limited to, at least one of: random access memory (Random Access Memory, RAM) 1522, or other volatile memory that does not last for the duration of the power outage.

The computer program 1530 includes computer-executable instructions that are executed by the associated processor 1510. The program 1530 may be stored in the ROM 1520. The processor 1510 may perform any suitable actions and processes by loading the program 1530 into the RAM 1520.

Possible implementations of the present application may be implemented by means of program 1530 such that device 1500 may perform any of the processes discussed with reference to fig. 2 through 11. Possible implementations of the present application may also be realized in hardware or by a combination of software and hardware.

In some implementations, the program 1530 may be tangibly embodied in a computer-readable medium, which may be included in the device 1500 (such as in the memory 1520) or other storage device accessible by the device 1500. The program 1530 may be loaded from a computer readable medium into the RAM 1522 for execution. The computer readable medium may include any type of tangible, non-volatile memory, such as ROM, EPROM, flash memory, hard disk, CD, DVD, etc.

The application also provides a communication system. The communication system comprises a communication apparatus 1200, an access network device 1300 and an access network device 1400 as described above.

In general, the various possible implementations of the application may be realized 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 the possible implementations of this application are shown and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof.

The present application also provides at least one computer program product tangibly stored on a non-transitory computer-readable storage medium. The computer program product comprises computer executable instructions, such as instructions included in program modules, which are executed in a device on a real or virtual processor of a target to perform the processes/methods as described above with reference to fig. 2-11. Generally, program modules include routines, programs, libraries, objects, classes, components, data structures, etc. that perform particular tasks or implement particular abstract data types. In various possible implementations, the functionality of the program modules may be combined or split between program modules as desired. Machine-executable instructions for program modules may be executed within local or distributed devices. In distributed devices, program modules may be located in both local and remote memory storage media.

Program code for carrying out methods of the present application may be written in any combination of one or more programming languages. These program code 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 code, when executed by the processor or controller, causes the functions/operations specified in the flowchart and/or block diagram to be implemented. The program code may execute entirely on the machine, partly on the machine, as a stand-alone software package, partly on the machine and partly on a remote machine or entirely on the remote machine or server.

In the context of this application, a machine-readable medium may be a tangible medium that can 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. The machine-readable medium may include, but is 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 a machine-readable storage medium would include an electrical connection based on 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.

Moreover, although operations are depicted in a particular order, this should 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 included in the above discussion, these should not be construed as limiting the scope of the present application. Certain features that are described in the context of separate possible implementations may also be implemented in combination in a single implementation. Conversely, various features that are described in the context of a single implementation can also be implemented in multiple implementations separately or in any suitable subcombination.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter 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 example forms of implementing the claims.

Claims

1. A method of communication, comprising:

the method comprises the steps that a terminal device obtains a cell change reason indication, wherein the cell change reason indication indicates that a first cell change from a source cell to a first target cell or a second cell change from the first target cell to a second target cell of the terminal device is associated with communication service of the terminal device, the first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology different from the first wireless access technology; and

and the terminal equipment sends the cell change reason indication to second target access network equipment to which the second target cell belongs.

2. The method of claim 1, wherein the cell change cause indication comprises:

the reason for the terminal device to change out of the source cell or out of the first target cell, and/or,

The reason why the terminal device changes to the first target cell or the reason why a cell changes to the second target cell.

3. The method of claim 1 or 2, wherein the cell change cause indication indicates at least one of:

the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; and

the second cell change is associated with a quick return procedure of the terminal device from the first target cell to the second target cell.

4. A method according to claim 3, further comprising:

the terminal device obtains at least one of the following:

the indication of the type of the voice fallback procedure indicates that the voice fallback procedure is an evolved packet system voice fallback procedure or an inter-radio access technology voice fallback procedure; and

indication of a cell change execution mode, including handover or redirection.

5. The method of claim 3, wherein the voice fallback procedure comprises a normal call voice fallback procedure or an emergency call voice fallback procedure, and the quick return procedure comprises a normal call voice quick return procedure or an emergency call voice quick return procedure.

6. The method of claim 1, wherein the terminal device obtaining the cell change cause indication comprises:

and the terminal equipment acquires the cell change reason indication from source access network equipment to which the source cell belongs.

7. The method of claim 6, wherein the terminal device obtaining the cell change cause indication from the source access network device comprises:

the terminal device receives a first handover command associated with the first cell change from the source access network device, the first handover command including the cell change cause indication.

8. The method of claim 1, wherein the terminal device obtaining the cell change cause indication comprises:

and the terminal equipment acquires the cell change reason indication from first target access network equipment to which the first target cell belongs.

9. The method of claim 8, wherein the terminal device obtaining the cell change cause indication from the first target access network device comprises:

the terminal device receives a second cell handover command associated with the second cell change from the first target access network device, the second handover command including the cell change cause indication.

10. The method of claim 1, wherein the terminal device sending the cell change cause indication to the second target access network device comprises:

the terminal equipment responds to the receiving of a second cell switching command associated with the second cell change from first target access network equipment to which the first target cell belongs, and sends a radio resource control reconfiguration complete message to the second target access network equipment, wherein the radio resource control reconfiguration complete message comprises the cell change reason indication.

11. The method of claim 1, wherein the terminal device sending the cell change cause indication to the second target access network device comprises:

the terminal equipment receives a request for history information of the terminal equipment from the second target access network equipment; and

and the terminal equipment sends the history information to the second target access network equipment, wherein the history information comprises the cell change reason indication.

12. A method of communication, comprising:

a first target access network device acquires a cell change reason indication, wherein the cell change reason indication indicates that a first cell change from a source cell to a first target cell of the first target access network device or a second cell change from the first target cell to a second target cell of the terminal device is associated with communication services of the terminal device, the first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology different from the first wireless access technology; and

And the first target access network equipment provides the cell change reason indication for the second target access network equipment to which the second target cell belongs.

13. The method of claim 12, wherein the cell change cause indication comprises:

the reason why the terminal device changes to the first target cell or the reason why the terminal device changes to the second target cell.

14. The method of claim 12 or 13, wherein the cell change cause indication indicates at least one of:

15. The method of claim 12, further comprising:

the first target access network device obtains at least one of the following:

Indication of a cell change execution mode, including handover or redirection.

16. The method of claim 14, wherein the voice fallback procedure comprises a normal call voice fallback procedure or an emergency call voice fallback procedure, the quick return procedure comprising a normal call voice quick return procedure or an emergency call voice quick return procedure.

17. The method of claim 12, wherein the first target access network device obtaining the cell change cause indication comprises:

and the first target access network equipment acquires the cell change reason indication from the source access network equipment to which the source cell belongs.

18. The method of claim 17, wherein the first target access network device obtaining the cell change cause indication from the source access network device comprises:

the first target access network device obtains first history information of the terminal device from the source access network device, wherein the first history information comprises the cell change reason indication.

19. The method of claim 18, wherein the first target access network device providing the cell change cause indication to the second target access network device comprises:

The first target access network device provides second history information of the terminal device to the second target access network device, the second history information comprises the cell change reason indication, the second history information comprises the first history information, and/or third history information of the terminal device recorded by the first target access network device.

20. The method of any of claims 12 to 19, wherein the first target access network device providing the cell change cause indication to the second target access network device comprises:

the first target access network device sends a handover request for the second cell change to the second target access network device, the handover request including the cell change cause indication.

21. A method of communication, comprising:

a second target access network device obtains a cell change reason indication, wherein the cell change reason indication indicates that a first cell change from a source cell to a first target cell or a second cell change from the first target cell to a second target cell of the second target access network device is associated with communication service of the terminal device, the first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology different from the first wireless access technology; and

And the second target access network equipment sends the cell change reason indication to source access network equipment to which the source cell belongs.

22. The method of claim 21, wherein the cell change cause indication comprises:

23. The method of claim 21 or 22, wherein the cell change cause indication indicates at least one of:

the first cell change is associated with a voice fallback procedure of the terminal device from the source cell to the first target cell; or alternatively

24. The method of claim 23, further comprising:

the second target access network device obtains at least one of the following:

Indication of a cell change execution mode, including handover or redirection.

25. The method of claim 23, wherein the voice fallback procedure comprises a normal call voice fallback procedure or an emergency call voice fallback procedure, the quick return procedure comprising a normal call voice quick return procedure or an emergency call voice quick return procedure.

26. The method of claim 21, wherein the second target access network device obtaining the cell change cause indication comprises:

and acquiring the cell change reason indication from the terminal equipment.

27. The method of claim 26, wherein the second target access network device obtaining the cell change cause indication from the terminal device comprises:

and receiving a radio resource control reconfiguration complete message from the terminal equipment, wherein the radio resource control reconfiguration complete message comprises the cell change reason indication.

28. The method of claim 26, wherein the second target access network device obtaining the cell change cause indication from the terminal device comprises:

sending a request for history information of the terminal equipment to the terminal equipment; and

The history information is received from the terminal device, the history information comprising the cell change cause indication.

29. The method of claim 21, wherein obtaining the indication of the cause of the cell change comprises:

and acquiring the cell change reason indication from first target access network equipment to which the first target cell belongs.

30. The method of claim 29, wherein obtaining the indication of the cause of the cell change from the first target access network device comprises:

obtaining second history information of the terminal equipment from the first target access network equipment, wherein the second history information comprises the cell change reason indication, the second history information comprises first history information of the terminal equipment, which is obtained by the first target access network equipment from source access network equipment to which the source cell belongs, and/or third history information of the terminal equipment, which is recorded by the first target access network equipment.

31. The method of claim 29, wherein obtaining the indication of the cause of the cell change from the first target access network device comprises:

a cell change request for the second cell change is received from the first target access network device, the cell change request comprising the cell change cause indication.

32. A method of communication, comprising:

a source access network device obtains a cell change reason indication, wherein the cell change reason indication indicates that a first cell change or a second cell change is associated with a communication service of the terminal device, the first cell change comprises a source cell change provided by the terminal device from the source access network device to a first target cell, the second cell change comprises a change of the terminal device from the first target cell to a second target cell, the first target cell adopts a first wireless access technology, and the source cell and the second target cell adopt a second wireless access technology; and

the source access network device determines that the first cell change and the second cell change are independent of an intersystem ping-pong event based on the cell change cause indication.

33. The method of claim 32, wherein the source access network device obtaining the cell change cause indication comprises:

and receiving an intersystem ping-pong event report from second target access network equipment to which the second target cell belongs, wherein the intersystem ping-pong event report comprises the cell change reason indication.

34. The method of claim 32, wherein the cell change cause indication indicates at least one of:

35. The method of claim 32, further comprising:

the source access network device obtains at least one of the following:

indication of a cell change execution mode, including handover or redirection.

36. A terminal device comprising means for performing the method according to any of claims 1 to 11.

37. An access network device comprising means for performing the method of any of claims 12 to 20.

38. An access network device comprising means for performing the method of any of claims 21 to 31.

39. An access network device comprising means for performing the method of any of claims 32 to 35.

40. A communication apparatus, comprising:

at least one processor; and

at least one memory coupled to the at least one processor and storing instructions for execution by the at least one processor, which when executed by the at least one processor, cause the communication apparatus to implement the method of any one of claims 1 to 11, 12 to 20, 21 to 31, and 32 to 35.

41. A computer readable storage medium having stored thereon a computer program which, when executed by a processor, implements the method according to any one of claims 1 to 11, 12 to 20, 21 to 31 and 32 to 35.

42. A chip configured to perform the method of any one of claims 1 to 11, 12 to 20, 21 to 31 and 32 to 35.