CN113068237B - Session management method, user equipment, computer storage medium and system - Google Patents

Abstract

The embodiment of the present application discloses a session management method, user equipment, computer storage medium and system, which are applied to user equipment. The method includes: receiving a protocol data unit PDU session modification command; wherein the PDU session modification command is used to indicate the current and when it is detected that the number of established PDU sessions is less than the preset session threshold, establish a second PDU session and record the monitoring result; wherein, the monitoring result includes at least: the establishment consumption of the second PDU session time and downlink user data flow; release the first PDU session according to the monitoring result. In this way, not only the continuity of service flow transmission can be ensured, but also the time during which new and old sessions coexist can be shortened, resource waste of user equipment and network equipment can be avoided, and system performance can be improved.

Description

A session management method, user equipment, computer storage medium and system

technical field

The present application relates to the field of communication technologies, and in particular, to a session management method, user equipment, computer storage medium and system.

Background technique

With the rapid development of communication technology, the fifth generation (Fifth Generation, 5G) mobile communication technology is applied. In the 5G system, in order to ensure the reliability of data transmission, it is supported that multiple Protocol Data Unit (PDU) sessions can be created between user equipment (User Equipment, UE) and network equipment. Here, the Service and Session Continuity (SSC) mode is an attribute of the PDU session in the 5G system, and is used to indicate the guarantee mode of the service flow continuity of the PDU session when the service is transmitted.

At present, there are three values of SSC mode, namely SSC mode 1, SSC mode 2 and SSC mode 3. When the network device decides to initiate the PDU session switching process in SSC mode 3, it means that the network side no longer wishes to perform service flow transmission through the PDU session, and can release it at any time. However, due to the uncertainty of the specific implementation of the handover process, the current release strategy adopted by the user equipment has some defects, for example, either the downlink service data being transmitted cannot be transmitted to the user, resulting in interruption of service flow transmission; The time keeping of new and old sessions coexists, resulting in waste of resources for both users and the network, resulting in poor system performance.

SUMMARY OF THE INVENTION

The present application proposes a session management method, user equipment, computer storage medium and system, which can not only ensure the continuity of service flow transmission, but also shorten the time when new and old sessions exist at the same time, and avoid the waste of resources by user equipment and network equipment. Helps improve system performance.

In order to achieve the above-mentioned purpose, the technical scheme of the present application is achieved in this way:

In a first aspect, an embodiment of the present application provides a session management method, which is applied to a user equipment, and the method includes:

receiving a protocol data unit PDU session modification command; wherein the PDU session modification command is used to instruct the current first PDU session to be switched; and

When it is detected that the number of established PDU sessions is less than the preset session threshold, a second PDU session is established and a monitoring result is recorded; wherein the monitoring result at least includes: the establishment time and downlink user data of the second PDU session flow;

According to the monitoring result, the first PDU session is released.

In a second aspect, an embodiment of the present application provides a user equipment, where the user equipment includes a receiving unit, a establishing unit, and a releasing unit; wherein,

The receiving unit is configured to receive a protocol data unit PDU session modification command; wherein the PDU session modification command is used to instruct the current first PDU session to be switched;

The establishment unit is configured to establish a second PDU session and record a monitoring result when it is detected that the number of established PDU sessions is less than a preset session threshold; wherein the monitoring result at least includes: the second PDU session. Establish time-consuming and downlink user data traffic;

The releasing unit is configured to release the first PDU session according to the monitoring result.

In a third aspect, an embodiment of the present application provides a user equipment, where the user equipment includes a memory and a processor; wherein,

the memory for storing a computer program executable on the processor;

The processor is configured to execute the method according to the first aspect when running the computer program.

In a fourth aspect, an embodiment of the present application provides a computer storage medium, where the computer storage medium stores a computer program, and the computer program implements the method according to the first aspect when the computer program is executed by at least one processor.

In a fifth aspect, an embodiment of the present application provides a communication system, where the communication system includes a network device and the user equipment according to the second aspect or the third aspect.

In a session management method, user equipment, computer storage medium, and system provided by the embodiments of the present application, a protocol data unit PDU session modification command is received; wherein, the PDU session modification command is used to indicate the current first PDU session Perform handover; and when it is detected that the number of established PDU sessions is less than a preset session threshold, establish a second PDU session and record a monitoring result; wherein, the monitoring result includes at least: the establishment time of the second PDU session and downlink user data traffic; according to the monitoring result, release the first PDU session. In this way, the technical solution of the present application adopts a method in which the user equipment uniformly initiates the release of the old PDU session, which ensures the continuity of service flow transmission, and can also shorten the time during which the old and new PDU sessions exist at the same time, thereby avoiding user equipment and network equipment. It also avoids the risk of transmission interruption of user data, which helps to improve system performance.

Description of drawings

1 is a schematic diagram of a relationship between a user equipment and a network device according to an embodiment of the present application;

2 is a schematic flowchart of a PDU session switching process in SSC mode 3 under a 5G network provided by the related art;

3 is a schematic flowchart of another PDU session switching process in SSC mode 3 in a 5G network provided by the related art;

4 is a schematic flowchart of a session management method provided by an embodiment of the present application;

FIG. 5 is a detailed schematic flowchart of a session management method provided by an embodiment of the present application;

6 is a detailed schematic flowchart of another session management method provided by an embodiment of the present application;

FIG. 7 is a schematic diagram of the composition and structure of a user equipment according to an embodiment of the present application;

FIG. 8 is a schematic diagram of a specific hardware structure of a user equipment according to an embodiment of the present application;

FIG. 9 is a schematic diagram of the composition and structure of a communication system according to an embodiment of the present application.

Detailed ways

In order to have a more detailed understanding of the features and technical contents of the embodiments of the present application, the implementation of the embodiments of the present application will be described in detail below with reference to the accompanying drawings.

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the technical field to which this application belongs. The terms used herein are only for the purpose of describing the embodiments of the present application, and are not intended to limit the present application.

In the following description, reference is made to "some embodiments" which describe a subset of all possible embodiments, but it is understood that "some embodiments" can be the same or a different subset of all possible embodiments, and Can be combined with each other without conflict. It should also be pointed out that the term "first\second\third" involved in the embodiments of the present application is only used to distinguish similar objects, and does not represent a specific ordering of objects. It is understood that "first\second\" Where permitted, the specific order or sequence may be interchanged so that the embodiments of the present application described herein can be implemented in sequences other than those illustrated or described herein.

It should be noted that the Service and Session Continuity (SSC) mode is an attribute of the Protocol Data Unit (PDU) session in the 5G system, which is used to indicate that when the PDU session performs service transmission, its A guarantee model for business flow continuity. In the Technical Specification (TS) 24.501 protocol of the 3rd Generation Partnership Project (3GPP), three values of the SSC mode are specified, namely SSC mode 1, SSC mode 2 and SSC mode 3. For a PDU session whose value is SSC mode 1, its protocol data unit session anchor (PDU Session Anchor, PSA) will not change during the existence of the session; for a PDU session whose value is SSC mode 2, its PSA can be released by first releasing the old session , and then switch by establishing a new session connected to the same data network (Data Network, DN); for a PDU session whose value is SSC mode 3, its PSA is to first establish a new session connected to the same DN, and then delete the old session. In this case, the old and new sessions will coexist for a period of time.

The 3GPP TS 23.502 protocol stipulates that during the PDU session switching process in SSC mode 3, the Session Management Function (SMF) on the network side may send a time-related session to the Session Management Module (SMF) on the user side. parameter (often called "session retention time"). After the SM receives this parameter, it directly reports it to the Application Processor (AP) on the user side. This parameter is used by the network side to notify the user side that in this handover, the network side SMF is willing to reserve the old session for the user side. time. For PDU session switching in SSC mode 3, there are currently three scenarios in which the old session is released: (1) The network side carries the session retention time parameter. During the session retention time, the user side determines that all service data on the session has been switched to For transmission on the new session, the user-side AP initiates the release process of the old session; (2) The network side carries the session retention time parameter. After the session retention time exceeds, the network-side SMF directly initiates the release process of the old session; (3) The network side does not carry the session retention time parameter, and the user side waits for the network side SMF to release the old session. In addition, it is clearly pointed out in the 3GPP TS 23.502 protocol that how to switch the service flow on the user side from the old session to the new session depends on the implementation on the user side.

It can be understood that the above-mentioned relationship between the SM, the AP and the network side is specifically shown in FIG. 1 . In FIG. 1, the network side has network equipment, and the user side has user equipment, the user equipment includes an application processor (AP) and a session management module (SM); wherein, in the user equipment, the SM is set in the modem ( Modem).

Referring to FIG. 2 , it shows a schematic flowchart of a PDU session switching process of SSC mode 3 in a 5G network provided by the related art. As shown in Figure 2, the process can include:

S201: Uplink/downlink data is transmitted between the network device and the AP.

S202: The network device determines to switch the current old PDU session.

S203: The network device sends a PDU session modification command to the SM.

S204: The SM returns a PDU session modification completion command to the network device.

S205: The SM reports the first message to the AP.

S206: The AP sends a first message command to the SM.

S207: A new PDU session establishment process is performed between the SM and the network device.

S208: The SM reports the second message to the AP.

S209: The user equipment switches the service flow from the old PDU session to the new PDU session according to its own implementation.

S210: Perform the old PCU session release process between the AP and the network device.

Specifically, during the transmission of uplink/downlink data between the user side and the network side, the network side determines to switch the PSA corresponding to the PDU session where the current service flow is located for some reason. At this time, the network side will first perform internal processing, that is, Step S202 is performed.

Subsequently, the network side can send a PDU session modification command, and the PDU session modification command may carry the session retention time parameter, that is, step S203 is performed; when the SM on the user side receives the PDU session modification command, it will perform the PDU session modification command. In response, the PDU session modification command is reported to the AP on the user side. If there is a session retention time parameter, it is reported to the AP together, that is, steps S204 and S205 are performed. Here, the first message may be a message for modifying the current PDU session, and carries the session retention time.

Further, if the AP on the user side receives the PDU session modification command, it needs to judge whether it is a PDU session modification of SSC mode 3, if the judgment result is yes, then trigger the SM to initiate the PDU session establishment process; that is, execute S206 and S207 Step, the AP sends a first message command to the SM, where the first message command is used to instruct the SM to establish a new PDU session.

Further, after the PDU session is successfully established, the user side switches the service flow from the old PDU session to the new PDU session according to its own implementation; that is, steps S208 and S209 are performed, and after the PDU session is successfully established, the SM reports the second message to the AP, The second message here may be a message that the session is established successfully, and then the AP will switch the service flow from the old PDU session to the new PDU session according to its own implementation method.

Further, in the process of uplink/downlink data transmission between the user equipment and the network equipment, the AP can, according to whether the session retention time parameter is received, the old PDU session is then released by one of the three PDU session release scenarios mentioned above. Release, that is, step S210 is executed.

According to the process shown in FIG. 2 , when the SMF on the network side decides to initiate the PDU session switching process of SSC mode 3, it means that the network side no longer wishes to perform service flow transmission through the PDU session and can release it at any time. Due to the uncertainty of the specific implementation of this handover process on the user side, for the purpose of ensuring the continuous transmission of service flows, the network side can provide a period of time to maintain the coexistence of the old and new PDU sessions (may inform the user side through the session retention time parameter, or (may not be notified), so that the user side has sufficient time to smoothly switch the service flow from the old PDU session to the new PDU session, and then release the old PDU session through the PDU session release process.

At present, there are two commonly used PDU session release strategies on the user side: (1) If the user side receives the session retention time parameter, when the new PDU session is successfully established, the AP directly initiates the release process of the old PDU session; With this parameter, wait for the network side to initiate the release process of the old PDU session. (2) The user side waits for the network side to initiate the release process of the old PDU session regardless of whether the session retention time parameter is received or not.

In common scenarios, the current release strategy adopted by the user side has the following problems:

(a) The user side initiates the release of the old PDU session immediately after the new session is successfully established. Although the old PDU session resources of the user and the network can be quickly released, there may be a situation that interrupts the service flow transmission. That is, when the network just transmits downlink service data through the old PDU session, it receives a release request from the user side, and then releases the old PDU session, so that the downlink service data being transmitted cannot be transmitted to the user, and the service flow transmission is interrupted.

(b) The user side has been waiting for the network side to initiate the release process of the old PDU session. Although it can ensure that there will be no transmission interruption when the service flow is switched from the old PDU session to the new PDU session, the old and new PDU sessions are maintained for a long time. , resulting in a waste of resources for both users and the network.

In addition, in a special scenario, the release strategy currently adopted by the user side will cause a more serious problem. If the number of PDU sessions established by the SM layer of the user side has reached the limit number of the user side, according to the description of the 3GPP TS24.501 protocol, after the user receives the PDU session modification command sent by the network, because a new PDU session cannot be established, the Directly reject this request from the network and continue to use the old PDU session for transmission. At this time, the network side may have two corresponding processes: 1) Terminate this handover process, and continue to use the current PDU session (ie, the old PDU session) for transmission. However, since the PSA of the old PDU session on the network side is already in a saturated state due to the switchover, continuing to use the old PDU session may cause the transmission quality to degrade. 2) After waiting for a period of time, the network directly initiates the release of the old PDU session. This will result in that the service flow performed on the PDU session cannot continue to be transmitted, which violates the original intention of ensuring the continuity of the service flow of the PDU session as much as possible. Exemplarily, referring to FIG. 3 , it shows a schematic flowchart of another PDU session switching process of SSC mode 3 in a 5G network provided by the related art. As shown in Figure 3, the process may include:

S301: Uplink/downlink data is transmitted between the network device and the AP.

S302: The network device determines to switch the current old PDU session.

S303: The network device sends a PDU session modification command to the SM.

S304: When it is detected that the number of currently established sessions reaches the preset session threshold, the SM will reject the PDU session modification command.

S305: The SM returns a PDU session modification rejection command to the network device.

S306: The network device continues to use or release the old PDU session.

Specifically, during the transmission of uplink/downlink data between the user side and the network side, if the network decides to switch the current PDU session, the network side will initiate a PDU session modification process, that is, perform steps S302 and S303.

On the user side, if the SM detects that the currently established PDU session has reached the preset session threshold (such as the maximum number of sessions supported by the user setting), the user side will reject the network's PDU session modification command, that is, step S304 is performed.

Further, the user returns the PDU session modification rejection command to the network device. After the network side receives the modification rejection, the old PDU session can be maintained or released after a period of time, that is, steps S305 and S306 are performed.

In short, in the related art, due to the uncertainty of the specific implementation of the PDU switching process for SSC mode 3, the release strategy adopted by the current user equipment has some defects, for example, the downlink service data being transmitted cannot be transmitted to the user. , resulting in interruption of service flow transmission; or keeping new and old sessions coexisting for a long time, resulting in waste of resources for both users and the network, resulting in poor system performance.

An embodiment of the present application provides a session management method, which is applied to a user equipment. The basic idea of the method is: receiving a PDU session modification command; wherein the PDU session modification command is used to instruct the current first PDU session to be switched And when it is detected that the number of established PDU sessions is less than the preset session threshold, the second PDU session is established and the monitoring result is recorded; Wherein, the monitoring result includes at least: the establishment time-consuming and downlink of the second PDU session User data traffic; according to the monitoring result, release the first PDU session. In this way, the technical solution of the present application adopts the method in which the user equipment uniformly initiates the release of the old PDU session, which ensures the continuity of service flow transmission, can also shorten the time that the old and new PDU sessions coexist, and can avoid the user equipment and network equipment. waste, but also to avoid the risk of transmission interruption of user data, which helps to improve system performance.

The embodiments of the present application will be described in detail below with reference to the accompanying drawings.

In an embodiment of the present application, referring to FIG. 4 , it shows a schematic flowchart of a session management method provided by an embodiment of the present application. As shown in Figure 4, the method may include:

S401: Receive a PDU session modification command.

It should be noted that, the session management method in the embodiment of the present application is applied to the user equipment. Here, the user equipment may also be referred to as a terminal device, such as a smart phone, a tablet computer, a notebook computer, a palmtop computer, a personal digital assistant (Personal Digital Assistant, PDA), a portable media player (Portable Media Player, PMP), Navigation device, wearable device, mobile station (mobile station), mobile unit (mobile unit), mobile client, chip, Field Programmable Gate Array (Field Programmable Gate Array, FPGA), etc., which are not specifically limited here.

It should also be noted that the PDU session modification command is used to instruct the current first PDU session to be switched. Specifically, when the network device decides to switch the current first PDU session, the network device will initiate a PDU session modification process at this time, and send a PDU session modification command to the terminal device. That is, if the network device decides to switch the current first PDU session, the user equipment can receive the PDU session modification command sent by the network device.

In the embodiment of the present application, from the perspective of service flow continuity, after receiving the PDU session modification command, the user equipment may, according to the application scenario and its own actual situation, propose corresponding optimization schemes for different application scenarios to determine the user When does the device release the first PDU session (ie, the old PDU session), so as to ensure the continuity of service flow transmission as much as possible and save resources on the user side and the network side.

Specifically, the embodiment of the present application can divide the application scenarios into normal scenarios and special scenarios according to the comparison result between the number of established PDU sessions and the preset session threshold, and then respectively propose optimization schemes for the two application scenarios.

S402: In the case that it is detected that the number of established PDU sessions is less than the preset session threshold, establish a second PDU session and record the monitoring result.

S403: Release the first PDU session according to the monitoring result.

Here, the monitoring result may at least include: the establishment time of the second PDU session and the downlink user data traffic.

It should be noted that the number of established PDU sessions refers to the number of PDU sessions that have been successfully established in the user equipment. Generally, the maximum number of sessions supported by the user equipment is 15, and the preset session threshold may be the maximum number of sessions supported by the user equipment. However, the preset session threshold may be specifically set according to the actual situation. For example, the preset session threshold may be set to 15 or 10, which is not limited here.

It should also be noted that the number of established PDU sessions is compared with the preset session threshold; if the number of established PDU sessions is less than the preset session threshold, it indicates that the current application scenario is a normal scenario, then the optimization solution at this time is to execute S402 and step S403. If the number of established PDU sessions is greater than or equal to the preset session threshold, it indicates that the current application scenario is a special scenario, and the optimization scheme at this time will be described as follows.

In some embodiments, after S401, the method may further include:

In the case of detecting that the number of established PDU sessions is greater than or equal to a preset session threshold, release the first PDU session;

After the first PDU session is successfully released, a second PDU session is established.

That is to say, for a special scenario, after receiving the PDU session modification command, if the user equipment detects that the number of established PDU sessions is greater than or equal to the preset session threshold, it will release the first PDU session first, and then use the first PDU session in the first PDU session. After the release is successful, a second PDU session is established.

Specifically, in special scenarios, if it is detected that the number of established PDU sessions is greater than or equal to the preset session threshold, then process information can be recorded at this time, such as recording an identification information, and the first PDU session is released at the same time; in the first PDU After the session is released successfully, a second PDU session is established according to the identification information. Wherein, the identification information here may indicate that when it is detected that the number of established PDU sessions is greater than or equal to the preset session threshold, first trigger the release process of the first PDU session, and then start the establishment process of the second PDU session.

It should also be noted that the first PDU session may be referred to as an old PDU session, and the second PDU session may be referred to as a new PDU session. Further, in some embodiments, the method may further include: performing data interaction through the second PDU session.

That is, after the second PDU session is successfully established, the network device and the user equipment can use the second PDU session to perform data exchange.

Understandably, due to an attribute of the PDU session in the SSC mode 5G system, it can indicate the guarantee mode of the service flow continuity of the PDU session when the service is transmitted. Currently, in the 3GPP TS 24.501 protocol, three values of the SSC mode are specified, namely SSC mode 1, SSC mode 2 and SSC mode 3. For a PDU session whose value is SSC mode 1, its PSA will not change during the existence of the session; for a PDU session whose value is SSC mode 2, its PSA can be released by first releasing the old session and then establishing a new session connected to the same DN. Perform handover; for a PDU session whose value is SSC mode 3, its PSA is to first establish a new session connected to the same DN, and then delete the old session. At this time, the old and new sessions will have a coexistence period. That is to say, in SSC mode 3, the network device is allowed to maintain the PDU session between the user equipment and the old PDU session anchor until the new PDU session (the new PDU session anchor is connected to the same DN) is established. The user equipment has two session anchors and a PDU session at the same time, and finally releases the old PDU session.

Based on this, in the SSC mode 3 type PDU session switching process, the network device no longer wishes to perform service flow transmission through the old PDU session, and can release it at any time; however, due to the uncertainty of the specific implementation of the user equipment in the PDU session switching process For the purpose of ensuring continuous transmission of the service flow, the embodiment of the present application mainly solves the problem of the release policy of the old PDU session in the SSC mode 3.

In a possible implementation manner, for a normal scenario, when it is detected that the number of established PDU sessions is less than a preset session threshold, the method may further include:

determining the mode type of the first PDU session;

When the mode type of the first PDU session is a preset mode type, the steps of establishing the second PDU session and recording the monitoring result are performed.

In another possible implementation manner, for a special scenario, when it is detected that the number of established PDU sessions is greater than or equal to a preset session threshold, the method may further include:

determining the mode type of the first PDU session;

When the mode type of the first PDU session is a preset mode type, the step of releasing the first PDU session is performed.

In this embodiment of the present application, the preset mode type is SSC mode 3 .

That is to say, no matter it is a normal scenario or a special scenario, after receiving the PDU session modification command, the user equipment also needs to detect whether the SSC mode 3 type PDU session is currently being switched. In other words, if the mode type of the first PDU session to be switched is SSC mode 3, the old PDU session can be released according to the session management method described in the embodiment of the present application; if the mode of the first PDU session to be switched is currently If the type is not SSC mode 3, the old PDU session can be released according to the traditional session management method.

Further, for a normal scenario, the problem caused by the existing release strategy for releasing the old PDU session can be solved by using the user equipment to initiate the release of the old PDU session. The embodiment of the present application provides a method for user equipment to perform service flow switching to determine when to release a PDU session. Specifically, in some embodiments, the establishing the second PDU session and recording the monitoring result may include:

At the moment when the second PDU session is established and started, record the first moment;

In the process of establishing the second PDU session, monitoring whether the first PDU session receives downlink user data;

At the moment when the second PDU session is successfully established, record the second moment;

According to the second moment and the first moment, calculating the establishment time of the second PDU session;

The establishment time of the second PDU session and the downlink user data flow are recorded as the monitoring result.

It should be noted that when it is detected that the current switching of the SSC mode 3 type PDU session is detected, the establishment process of the second PDU session can be initiated at this time, and at the moment when the establishment of the second PDU session is started, the first moment is recorded, and at the same time Detect whether the first PDU session that is currently being switched receives downlink user data; then after the second PDU session is successfully established, it is necessary to record the second moment in order to calculate the time-consuming of the entire establishment process, that is, the establishment time of the second PDU session. time; at the same time, record the monitoring situation of downlink user data (specifically, it can be downlink user data traffic). In this way, the user equipment can determine the release policy of the first PDU session according to the recorded establishment time of the second PDU session and the monitoring situation of downlink user data, so as to serve as a reference for the subsequent release of the first PDU session.

Optionally, in some embodiments, the releasing the first PDU session according to the monitoring result may include:

During the establishment of the second PDU session, if it is monitored that the first PDU session receives downlink user data, the monitoring of the second PDU session is started;

When monitoring that the second PDU session receives downlink user data, the first PDU session is released.

In a specific example, if the current old PDU session (ie the first PDU session) receives downlink user data during the process of establishing a new PDU session (ie the second PDU session), the user equipment may start monitoring the new PDU session. When the new PDU session receives the first packet of downlink user data, the user equipment initiates a process of releasing the old PDU session.

It should also be noted that the user equipment may include an application processor (AP) and a session management module (SM). In this way, when the AP detects that the current SSC mode 3 type PDU session is being switched, it can initiate the establishment process of a new PDU session, and record the establishment time of the second PDU session and the monitoring of downlink user data; In the process of establishing a new PDU session, if the current old PDU session receives downlink user data, the AP can start monitoring the new PDU session. When the new PDU session receives the first packet of downlink user data, the AP initiates a process of releasing the old PDU session.

Optionally, in some embodiments, the releasing the first PDU session according to the monitoring result may include:

During the establishment of the second PDU session, if it is monitored that the first PDU session does not receive downlink user data, a release timer is started, and monitoring of the second PDU session is started;

Release the first PDU session when the timing of the release timer exceeds a preset duration, or when it is detected that the second PDU session receives downlink user data before the timing of the release timer does not exceed the preset duration .

In this embodiment of the present application, the preset duration may be greater than or equal to the establishment duration of the second PDU session.

In a specific example, if in the process of establishing a new PDU session, the current old PDU session does not receive downlink user data, the AP can start a release timer, and the timeout time of the release timer is set to the new PDU session The establishment is time consuming while monitoring for new PDU sessions. Once the release timer times out, or the new PDU session receives downlink user data before it times out, the AP can also initiate the release process of the old PDU session.

Further, for special scenarios, when the SM layer on the user equipment side receives the PDU session modification command, it no longer rejects the command from the network device, but reports the AP and releases the current PDU session, and establishes a new PDU session at the same time. . After receiving the report, the AP first triggers the release process of the old PDU session, and then initiates the establishment process of the new PDU session. Specifically, in some embodiments, recording the process information may at least include: sending a response message that the PDU session is successfully modified to the network device and reporting a release message of the first PDU session to the AP through the SM.

Further, in some embodiments, after the first PDU session is successfully released, the method may further include:

Report the successful release message of the first PDU session to the AP through the SM;

Correspondingly, the establishing the second PDU session may include:

Report the establishment message of the second PDU session to the AP through the SM;

The AP starts the process of establishing the second PDU session according to the received establishment message of the second PDU session.

That is to say, if the SM on the user equipment side detects that the number of currently established PDU sessions has reached the preset session threshold (such as the maximum number supported by itself), then the local will record this process and reply to the network device's PDU session modification success response message, and report the release message of the current PDU session to the AP at the same time. The AP then triggers the release procedure of the old PDU session. After the old PDU session is successfully released, the SM reports a release success message, and at the same time, according to the locally recorded process information, the SM reports to the AP to establish a new PDU session. The AP triggers the establishment process of a new PDU session. After the new PDU session is successfully established, the AP can use the new PDU session (ie, the second PDU session) to perform service flow transmission with the network device.

In short, the embodiments of the present application provide a specific method for switching the AP layer service flow on the user equipment side from the old PDU session to the new PDU session, and in special scenarios on the user equipment side, it can also be implemented locally to make the service flow. Streams are capable of continuous transmission. In this way, the embodiment of the present application is based on the perspective of ensuring the continuity of user service data transmission based on the SSC mode, and two scenarios (including normal scenarios and special scenarios) that have problems in the process of switching between SSC mode 3 type PDU sessions in the prior art specifications. optimized separately. Under normal circumstances, a specific method for switching the service flow of the AP on the user equipment side can be given, so that the release of the old PDU session is initiated by the AP, which ensures the continuity of service flow transmission and releases unnecessary resources in time. In a specific case, it can not only ensure the continuous transmission of user service data, but also avoid the risk of transmission interruption of user service data.

This embodiment provides a session management method, which is applied to user equipment. By receiving a protocol data unit PDU session modification command; wherein, the PDU session modification command is used to instruct the current first PDU session to be switched; and when it is detected that the number of established PDU sessions is less than the preset session threshold, establish The second PDU session is performed and the monitoring result is recorded; wherein, the monitoring result at least includes: the establishment time and downlink user data flow of the second PDU session; according to the monitoring result, the first PDU session is released. In this way, because the user equipment uniformly initiates the release of the old PDU session, the continuity of service flow transmission is ensured, and the time for the new and old PDU sessions to exist at the same time can be shortened, thereby avoiding the waste of resources by the user equipment and network equipment. It also avoids the risk of transmission interruption of user data, which helps to improve system performance.

In another embodiment of the present application, taking the best effort to ensure the continuity of service flow transmission and saving resources on the user equipment side and the network equipment side as the starting point, the release policies in the above-mentioned two scenarios (normal scenario and special scenario) are used as the starting point. A description of the detailed process.

It should be pointed out that the user equipment includes an application processor (AP) and a session management module (SM); wherein, in the user equipment, the SM is set on a modem (Modem). In addition, data interaction can be performed between the user equipment and the network equipment.

For normal scenarios, in the case of normal transmission, the problem caused by the old PDU session release policy is solved by the method of releasing the old PDU session initiated by the AP on the user equipment side, and a service on the user equipment side is provided. Flow switching method to determine when the AP releases old PDU sessions. Specifically, refer to FIG. 5 , which shows a detailed flowchart of a session management method provided by an embodiment of the present application. As shown in Figure 5, the detailed process may include:

S501: Uplink/downlink data is transmitted between the network device and the AP.

S502: The network device determines to switch the current old PDU session.

S503: Execute a PDU session modification process between the AP and the network device.

S504: The AP delivers the first message command to the SM.

S505: A new PDU session establishment process is performed between the SM and the network device.

S506: The AP records the current time and monitors whether the old PDU session receives downlink user data.

S507: The SM reports the second message to the AP.

S508: The AP calculates the time required for establishing the new PDU session, records the monitoring situation of downlink user data, switches the service flow, and releases the old PDU session.

S509: Perform the old PCU session release process between the AP and the network device.

It should be noted that the old PDU session is the first PDU session described in the foregoing embodiments, and the new PDU session is the second PDU session described in the foregoing embodiments.

It should also be noted that for S503, the PDU session modification process performed between the AP and the network device may specifically include: the network device sends a PDU session modification command to the SM; the SM returns a PDU session modification completion command to the network device; the SM sends a PDU session modification completion command to the network device. The AP reports the first message. Here, the first message may be a message for modifying the current PDU session, and carries the session retention time. In this way, after the AP on the user side receives the PDU session modification command, it needs to determine whether it is a PDU session modification in SSC mode 3. If the judgment result is yes, then the AP sends the first message command to the SM, that is, establishes a new PDU session. The command.

Further, after S504, that is, after the AP sends the first message command to the SM, on the one hand, the AP records the current time and monitors whether the old PDU session receives downlink user data, and on the other hand, executes a new PDU session between the SM and the network device. The establishment process, that is, S505 and S506 are performed simultaneously.

Further, for S507, the SM reports the second message to the AP, where the second message can be a message that the session is established successfully, and then the AP calculates the time-consuming for the establishment of the new PDU session, and records the monitoring situation of the downlink user data; and then according to These monitoring cases perform service flow switching and release old PDU sessions.

Specifically, when the network side decides to switch the current PDU session, it can initiate a PDU session modification process. Then, the user-side AP detects that the current SSC mode 3 type PDU session is modified, and can initiate a new PDU session establishment process, record the current time, and monitor whether the old PDU session currently being modified receives downlink user data. Subsequently, after the new PDU session is successfully established, the AP records the time again to calculate the time-consuming of the entire establishment process (ie, the establishment time of the new PDU session), and records the monitoring results of downlink user data for reference in subsequent release decisions.

In this embodiment of the present application, the AP can decide when to initiate the release of the old PDU session according to the following release policy:

(1) If in the process of establishing a new PDU session, the current old PDU session receives downlink user data, then the AP starts to monitor the new PDU session. When the new PDU session receives the first packet of downlink user data, the AP may initiate a process of releasing the old PDU session.

(2) If in the process of establishing a new PDU session, the current old PDU session does not receive downlink user data, then the AP starts a release timer. PDU session. Once the release timer expires, or before the new PDU session receives downlink user data, the AP can initiate the release procedure of the old PDU session.

Further, through the release process of the PDU session, the old PDU session can be released, and then the new PDU session can be used to perform service flow transmission with the network device.

For special scenarios, when the user-side SM receives the PDU session modification command, it no longer rejects the network's PDU session modification command, but reports the AP to release the current PDU session and establish a new PDU session. After receiving the report, the AP first triggers the release process of the old PDU session, and then initiates the establishment process of the new PDU session. The network equipment performs corresponding operations according to the received request of the user equipment. Specifically, refer to FIG. 6 , which shows a detailed flowchart of another session management method provided by an embodiment of the present application. As shown in Figure 6, the detailed process may include:

S601: Uplink/downlink data is transmitted between the network device and the AP.

S602: The network device determines to switch the current old PDU session.

S603: The network device sends a PDU session modification command to the SM.

S604: When the SM detects that the number of currently established sessions reaches a preset session threshold, the SM records this process locally.

S605: The SM returns a PDU session modification completion command to the network device.

S606: The SM reports the first message to the AP.

S607: The AP delivers the first message command to the SM.

S608: Perform the old PDU session release process between the SM and the network device.

S609: The SM initiates the establishment of a new PDU session again according to the locally recorded content.

S610: The SM reports the second message to the AP.

S611: The SM reports the third message to the AP.

S612: The AP sends a third message command to the SM.

S613: A new PDU session establishment process is performed between the SM and the network device.

S614: The SM reports the fourth message to the AP.

S615: According to the new PDU session, transmit uplink/downlink data between the network device and the AP.

It should be noted that the old PDU session is the first PDU session described in the foregoing embodiments, and the new PDU session is the second PDU session described in the foregoing embodiments.

It should also be noted that the first message may be a message for releasing the current PDU session, and the first message command may be a command for a session release request to instruct the SM to open the release process of the old PDU session; the second message may be a successful session release. message; the third message may be a message for establishing a new session, and the third message command may be a command for a session establishment request to instruct the SM to open the establishment process of a new PDU session; the fourth message may be a successful session establishment message, so that the AP The traffic flow with the network device can be implemented according to the new PDU session.

Specifically, first, when the network side decides to switch the current PDU session, it initiates a PDU session modification process. Secondly, the SM on the user side detects that the number of currently established PDU sessions reaches the maximum number supported by itself, records the process locally, replies that the modification of the PDU session on the network side is successful, and reports to the AP to release the current PDU session. Again, the AP triggers the release process of the old PDU session. After the old PDU session is released successfully, the SM reports a release success message, and at the same time reports the establishment of a new PDU session to the AP according to the local record. Again, the AP triggers the process of establishing a new PDU session. After the new PDU session is successfully established, the AP can use the new PDU session for service flow transmission.

In short, for the first normal scenario, the specific service flow switching method of the user-side AP can be given, and the AP can uniformly initiate the release of the old PDU session to ensure the continuity of the service flow transmission and minimize the It is possible to shorten the time that the old and new PDU sessions exist at the same time, which can avoid the waste of resources by the user and the network. This release strategy greatly optimizes the release strategy in the current technical specification. For example, releasing resources as soon as possible cannot guarantee continuous service flow transmission, or guaranteeing continuous service flow transmission but waiting for maximum time to waste resources. In this way, in the conflicting scenarios of ensuring continuity of service flow transmission and saving resources, the embodiment of the present application finds an optimal solution.

For the second special scenario, the method of first releasing the old PDU session and then establishing a new PDU session connected to the same DN may be adopted. Although the service flow transmission on the PDU session may be temporarily stopped, compared with the technical specification The method can ensure that the service flow continues to transmit after it is stopped. In addition, the stop time under normal circumstances should be in the millisecond level, which is negligible for users using wireless device applications, and it can also try its best to ensure the continuity of service flow transmission.

This embodiment provides a session management method, which is applied to user equipment. The specific implementation of the foregoing embodiments is described in detail through the foregoing embodiments, from which it can be seen that, through the technical solutions of the foregoing embodiments, the waste of resources by the user equipment and the network equipment can be avoided, and the transmission of user data can also be avoided. The risk of outage helps to improve system performance.

In yet another embodiment of the present application, based on the same inventive concept as the foregoing embodiments, see FIG. 7 , which shows a schematic structural diagram of a user equipment 70 provided by an embodiment of the present application. As shown in FIG. 7 , the user equipment 70 may include: a receiving unit 701, a establishing unit 702 and a releasing unit 703; wherein,

The receiving unit 701 is configured to receive a PDU session modification command; wherein, the PDU session modification command is used to instruct the current first PDU session to be switched;

The establishment unit 702 is configured to establish a second PDU session and record a monitoring result when it is detected that the number of established PDU sessions is less than a preset session threshold; wherein the monitoring result at least includes: the establishment of the second PDU session Time-consuming and downlink user data traffic;

The releasing unit 703 is configured to release the first PDU session according to the monitoring result.

In some embodiments, the releasing unit 703 is further configured to release the first PDU session when it is detected that the number of established PDU sessions is greater than or equal to a preset session threshold;

The establishing unit 702 is further configured to establish a second PDU session after the first PDU session is successfully released.

In some embodiments, referring to FIG. 7 , the user equipment 70 may further include a determination unit 704 configured to perform data interaction through the second PDU session.

In some embodiments, the determining unit 704 is further configured to determine the mode type of the first PDU session when it is detected that the number of established PDU sessions is less than a preset session threshold;

The establishing unit 702 is further configured to execute the step of establishing a second PDU session and recording the monitoring result when the mode type of the first PDU session is a preset mode type.

In some embodiments, the establishing unit 702 is specifically configured to record the first moment at the moment when the establishment of the second PDU session is started; and monitor the first PDU session during the establishment of the second PDU session Whether downlink user data is received; and at the moment when the second PDU session is successfully established, record the second moment; and calculate the establishment time of the second PDU session according to the second moment and the first moment ; and recording the establishment time of the second PDU session and the downlink user data flow as the monitoring result.

In some embodiments, the releasing unit 703 is specifically configured to, in the process of establishing the second PDU session, if it is monitored that the first PDU session receives downlink user data, then enable the release of the second PDU session. monitoring; and when monitoring that the second PDU session receives downlink user data, releasing the first PDU session.

In some embodiments, the release unit 703 is specifically configured to start the release timer and start the pairing process if it is detected that the first PDU session does not receive downlink user data during the establishment of the second PDU session. Monitoring of the second PDU session; when the timing of the release timer exceeds a preset duration, or before the timing of the release timer does not exceed a preset duration, it is monitored that the second PDU session receives downlink user data , release the first PDU session.

In some embodiments, the preset duration is greater than or equal to the establishment duration of the second PDU session.

In some embodiments, the determining unit 704 is further configured to determine the mode type of the first PDU session when it is detected that the number of established PDU sessions is greater than or equal to a preset session threshold;

The establishing unit 702 is further configured to release the first PDU session when the mode type of the first PDU session is a preset mode type.

In some embodiments, the preset mode type is Service and Session Continuity SSC Mode 3.

In some embodiments, the user equipment includes an application processor AP and a session management SM;

Correspondingly, the release unit 703 is further configured to report the successful release message of the first PDU session to the AP through the SM;

The establishing unit 702 is further configured to report the establishment message of the second PDU session to the AP through the SM; and the AP starts the establishment process of the second PDU session according to the received establishment message of the second PDU session.

In some embodiments, the preset session threshold is the maximum number of sessions supported by the user equipment.

It can be understood that, in this embodiment, a "unit" may be a part of a circuit, a part of a processor, a part of a program or software, etc., of course, it may also be a module, and it may also be non-modular. Moreover, each component in this embodiment may be integrated into one processing unit, or each unit may exist physically alone, or two or more units may be integrated into one unit. The above-mentioned integrated units can be implemented in the form of hardware, or can be implemented in the form of software function modules.

If the integrated unit is implemented in the form of a software functional module and is not sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this embodiment is essentially or The part that contributes to the prior art or the whole or part of the technical solution can be embodied in the form of a software product, the computer software product is stored in a storage medium, and includes several instructions for making a computer device (which can be It is a personal computer, a server, or a network device, etc.) or a processor (processor) that executes all or part of the steps of the method described in this embodiment. The aforementioned storage medium includes: U disk, removable hard disk, Read Only Memory (ROM), Random Access Memory (Random Access Memory, RAM), magnetic disk or optical disk and other media that can store program codes.

Therefore, this embodiment provides a computer storage medium, which is applied to the user equipment 70. The computer storage medium stores a computer program, and when the computer program is executed by at least one processor, any one of the foregoing embodiments is implemented. steps of the method.

Based on the composition of the user equipment 70 and the computer storage medium described above, see FIG. 8 , which shows a schematic diagram of a specific hardware structure of the user equipment 70 provided by the embodiment of the present application. As shown in FIG. 8 , it may include: a communication interface 801 , a memory 802 and a processor 803 ; various components are coupled together through a bus system 804 . It will be appreciated that the bus system 804 is used to implement connection communication between these components. In addition to the data bus, the bus system 804 also includes a power bus, a control bus, and a status signal bus. However, for clarity of illustration, the various buses are labeled as bus system 804 in FIG. 8 . Among them, the communication interface 801 is used for receiving and sending signals in the process of sending and receiving information with other external network elements;

a memory 802 for storing computer programs that can be executed on the processor 803;

The processor 803 is configured to, when running the computer program, execute:

receiving a protocol data unit PDU session modification command; wherein the PDU session modification command is used to instruct the current first PDU session to be switched; and

When it is detected that the number of established PDU sessions is less than the preset session threshold, a second PDU session is established and a monitoring result is recorded; wherein the monitoring result at least includes: the establishment time and downlink user data of the second PDU session flow;

According to the monitoring result, the first PDU session is released.

It can be understood that the memory 802 in this embodiment of the present application may be a volatile memory or a non-volatile memory, or may include both volatile and non-volatile memory. Wherein, the non-volatile memory may be Read-Only Memory (ROM), Programmable Read-Only Memory (PROM), Erasable Programmable Read-Only Memory (Erasable PROM, EPROM), Erase programmable read-only memory (Electrically EPROM, EEPROM) or flash memory. The volatile memory may be random access memory (RAM), which is used as an external cache. By way of example and not limitation, many forms of RAM are available, such as Static RAM (SRAM), Dynamic RAM (DRAM), Synchronous DRAM, SDRAM), double data rate synchronous dynamic random access memory (Double Data Rate SDRAM, DDRSDRAM), enhanced synchronous dynamic random access memory (Enhanced SDRAM, ESDRAM), synchronous link dynamic random access memory (Synchronous link DRAM, SLDRAM) And direct memory bus random access memory (Direct Rambus RAM, DRRAM). The memory 802 of the systems and methods described herein is intended to include, but not be limited to, these and any other suitable types of memory.

The processor 803 may be an integrated circuit chip with signal processing capability. In the implementation process, each step of the above-mentioned method can be completed by an integrated logic circuit of hardware in the processor 803 or an instruction in the form of software. The above-mentioned processor 803 may be a general-purpose processor, a digital signal processor (Digital Signal Processor, DSP), an application specific integrated circuit (Application Specific Integrated Circuit, ASIC), a Field Programmable Gate Array (Field Programmable Gate Array, FPGA) or other Programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The methods, steps, and logic block diagrams disclosed in the embodiments of this application can be implemented or executed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in conjunction with the embodiments of the present application may be directly embodied as executed by a hardware decoding processor, or executed by a combination of hardware and software modules in the decoding processor. The software modules may be located in random access memory, flash memory, read-only memory, programmable read-only memory or electrically erasable programmable memory, registers and other storage media mature in the art. The storage medium is located in the memory 802, and the processor 803 reads the information in the memory 802, and completes the steps of the above method in combination with its hardware.

It will be appreciated that the embodiments described herein may be implemented in hardware, software, firmware, middleware, microcode, or a combination thereof. For hardware implementation, the processing unit may be implemented in one or more Application Specific Integrated Circuits (ASIC), Digital Signal Processing (DSP), Digital Signal Processing Device (DSP Device, DSPD), programmable logic Devices (Programmable Logic Device, PLD), Field-Programmable Gate Array (Field-Programmable Gate Array, FPGA), general purpose processors, controllers, microcontrollers, microprocessors, other electronic units for performing the functions described in this application or a combination thereof.

For a software implementation, the techniques described herein may be implemented through modules (eg, procedures, functions, etc.) that perform the functions described herein. Software codes may be stored in memory and executed by a processor. The memory can be implemented in the processor or external to the processor.

Optionally, as another embodiment, the processor 803 is further configured to execute the steps of the method in any one of the foregoing embodiments when running the computer program.

This embodiment provides a user equipment, and the user equipment may include a receiving unit, a establishing unit, and a releasing unit. In this way, the technical solution of the present application adopts a method in which the user equipment uniformly initiates the release of the old PDU session, which ensures the continuity of service flow transmission, and can also shorten the time during which the old and new PDU sessions exist at the same time, thereby avoiding user equipment and network equipment. It also avoids the risk of transmission interruption of user data, which helps to improve system performance.

In yet another embodiment of the present application, referring to FIG. 9 , it shows a schematic structural diagram of the composition of a communication system 90 provided by an embodiment of the present application. As shown in FIG. 9 , the communication system 90 may include a network device 901 and a user device 902 . Here, the user equipment 902 may be the user equipment described in any one of the foregoing embodiments.

It should be noted that the communication system 90 described in the embodiments of the present application is not limited to the Long Term Evolution (Long Term Evolution, LTE) system, the 4th Generation (the 4th Generation, 4G) system, or the fifth generation mobile communication (the 5th Generation, 5G) system, New Radio (NR) system, and even the subsequent evolution of the communication system. In this communication system, data interaction can be performed between the network device 901 and the user equipment 902 through a wireless network.

In this way, in the communication system 90, the network side determines for some reason to switch the PSA corresponding to the PDU session where the current service flow is located. At this time, the network device 901 can send the PDU session modification command to the user equipment 902. After receiving the PDU session modification command, the user equipment 902 can divide the application scenarios into normal scenarios and special scenarios according to the comparison result between the number of established PDU sessions and the preset session threshold; and then propose corresponding optimization solutions for different application scenarios to determine when the user equipment releases the first PDU session (that is, the old PDU session), so as to not only ensure the continuity of service flow transmission, shorten the coexistence time of the old and new PDU sessions, but also avoid the waste of resources by the user equipment and network equipment At the same time, it can also avoid the risk of transmission interruption of user data, which helps to improve system performance.

It should be noted that, in this application, the terms "comprising", "comprising" or any other variation thereof are intended to encompass non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements , but also other elements not expressly listed or inherent to such a process, method, article or apparatus. Without further limitation, an element qualified by the phrase "comprising a..." does not preclude the presence of additional identical elements in a process, method, article or apparatus that includes the element.

The above-mentioned serial numbers of the embodiments of the present application are only for description, and do not represent the advantages or disadvantages of the embodiments.

The methods disclosed in the several method embodiments provided in this application can be arbitrarily combined under the condition of no conflict to obtain new method embodiments.

The features disclosed in the several product embodiments provided in this application can be combined arbitrarily without conflict to obtain a new product embodiment.

The features disclosed in several method or device embodiments provided in this application can be combined arbitrarily without conflict to obtain new method embodiments or device embodiments.

The above are only specific embodiments of the present application, but the protection scope of the present application is not limited to this. should be covered within the scope of protection of this application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims (16)

1. A session management method applied to a User Equipment (UE), the method comprising:

receiving a Protocol Data Unit (PDU) session modification command; wherein the PDU session modification command is used for indicating switching of the current first PDU session; and

under the condition that the number of the established PDU sessions is smaller than a preset session threshold value, establishing a second PDU session and recording a monitoring result; wherein the monitoring result at least comprises: establishing the second PDU session consumes time and carries out downlink user data flow;

and releasing the first PDU session according to the monitoring result.

2. The method of claim 1, further comprising:

releasing the first PDU session when detecting that the number of the established PDU sessions is larger than or equal to a preset session threshold value;

and after the first PDU session is successfully released, establishing a second PDU session.

3. The method according to claim 1 or 2, characterized in that the method further comprises:

and carrying out data interaction through the second PDU session.

4. The method of claim 1, wherein in case it is detected that the number of established PDU sessions is less than a preset session threshold, the method further comprises:

determining a mode type of the first PDU session;

and when the mode type of the first PDU session is a preset mode type, executing the steps of establishing a second PDU session and recording a monitoring result.

5. The method of claim 4, wherein establishing the second PDU session and recording the monitoring result comprises:

recording a first moment at the moment of establishing and starting the second PDU session;

monitoring whether the first PDU session receives downlink user data or not in the process of establishing the second PDU session;

recording a second moment at the moment when the second PDU session is successfully established;

calculating the time consumption for establishing the second PDU session according to the second time and the first time;

and taking the time consumed for establishing the second PDU session and the downlink user data flow as the monitoring result for recording.

6. The method of claim 5, wherein the releasing the first PDU session according to the monitoring result comprises:

in the process of establishing the second PDU session, if the first PDU session is monitored to receive downlink user data, starting monitoring of the second PDU session;

and when the second PDU session is monitored to receive downlink user data, releasing the first PDU session.

7. The method of claim 5, wherein the releasing the first PDU session according to the monitoring result comprises:

in the process of establishing the second PDU session, if monitoring that the first PDU session does not receive downlink user data, starting a release timer and starting monitoring of the second PDU session;

and when the timing of the release timer exceeds a preset time length, or when the second PDU session is monitored to receive downlink user data before the timing of the release timer does not exceed the preset time length, releasing the first PDU session.

8. The method of claim 7, wherein the preset duration is greater than or equal to a time consumed for establishing the second PDU session.

9. The method according to claim 2, wherein in case it is detected that the number of established PDU sessions is greater than or equal to a preset session threshold, the method further comprises the steps of:

determining a mode type of the first PDU session;

and when the mode type of the first PDU session is a preset mode type, releasing the first PDU session.

10. The method of claim 4 or 9, wherein the predetermined pattern type is traffic and session continuity SSC pattern 3.

11. The method of claim 2, wherein the user equipment comprises an application processor AP and a session management module SM, and wherein after the session release of the first PDU is successful, the method further comprises:

reporting a successful release message of the first PDU session to an AP through an SM;

accordingly, the establishing the second PDU session includes:

reporting a building message of the second PDU session to the AP through the SM;

and the AP starts the establishment flow of the second PDU session according to the received establishment message of the second PDU session.

12. The method of claim 1, wherein the preset session threshold is a maximum number of sessions supported by the UE.

13. User equipment, characterized in that the user equipment comprises a receiving unit, an establishing unit and a releasing unit; wherein,

the receiving unit is configured to be a Protocol Data Unit (PDU) session modification command; wherein the PDU session modification command is used for indicating switching of the current first PDU session;

the establishing unit is configured to establish a second PDU session and record a monitoring result under the condition that the number of the established PDU sessions is smaller than a preset session threshold value; wherein the monitoring result at least comprises: establishing the second PDU session consumes time and carries out downlink user data flow;

the release unit is configured to release the first PDU session according to the monitoring result.

14. A user device, wherein the user device comprises a memory and a processor; wherein,

the memory for storing a computer program operable on the processor;

the processor, when running the computer program, is configured to perform the method of any of claims 1 to 12.

15. A computer storage medium, characterized in that the computer storage medium stores a computer program which, when executed by at least one processor, implements the method of any one of claims 1 to 12.

16. A communication system, characterized in that the communication system comprises a network device and a user equipment according to claim 13 or 14.

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