A 5G network adaptive switching method and system for PTT voice communication

Abstract

The application discloses a 5G network adaptive switching method and system for PTT voice communication and relates to the technical field of communication network switching. In order to solve the problems of switching lag, voice loss and conversation interruption of the existing PTT voice communication in a strong shielding or high-speed moving scene, the application obtains data corresponding to a current service area, a candidate communication area and a PTT voice conversation, establishes a conversation bearing relationship between a current 5G link and a voice frame transmission process, determines a voice frame interval and a remaining bearing period, and generates a network switching demand state according to the same. When entering a regional switching preparation state, a regional bearing relationship corresponding to each candidate communication area is constructed. When entering a regional switching execution state, a bearing communication area and a communication access starting moment and a bearing migration moment are determined. Communication connection and bearing migration are completed according to the moments, and whether the PTT voice conversation is completed is judged in combination with a voice frame transmission state and a conversation control state before and after switching.

Description

Technical Field

[0001] This invention relates to the field of communication network switching technology, and in particular to a 5G network adaptive switching method and system for PTT voice communication. Background Technology

[0002] Push-to-talk (PTT) voice communication is a communication technology that uses buttons to trigger speaking rights and enables real-time voice interaction in one-on-one or group calls. It features short call setup times, ease of operation, and high efficiency in group dispatching, and is widely used in scenarios such as public security fire fighting, emergency rescue, transportation, energy inspection, industrial parks, and large-scale event security. With the development of 5G communication networks, PTT voice communication is gradually expanding from traditional dedicated trunking networks to 5G public networks, 5G private networks, and converged public and private networks, utilizing 5G networks to achieve voice data transmission, speaking rights control, group status synchronization, and dispatch information exchange.

[0003] During PTT (Push-to-Talk) terminal movement, the terminal may switch from its current 5G serving cell to another cell due to changes in location, base station coverage, surrounding obstructions, and network operation status. Existing 5G network handover schemes typically measure the reference signal received power, reference signal received quality, or signal-to-noise ratio of the current serving cell and adjacent candidate cells, comparing the measurement results with preset handover conditions. When the signal quality of the current serving cell falls below a set threshold, and the signal quality of the candidate cells meets the corresponding requirements for a preset time, the terminal reports the measurement results. Based on this, the network selects the target cell and initiates the handover. The terminal then completes handover command reception, target cell access, and service bearer restoration to continue transmitting PTT voice services.

[0004] The above handover methods can usually maintain terminal communication connections when network coverage changes are relatively gradual. However, in areas such as underground passages, tunnels, steel structure factories, or building corners, obstructions from walls, metal equipment, or large vehicles can cause significant changes in the signal quality of the current serving cell within a short period. Before the handover conditions have reached the preset duration, the transmission latency, packet loss, or voice transmission status of the current link may already be affected. If the handover is still performed according to the preset measurement and triggering conditions, the handover operation may not start in time, causing uplink voice transmission delays or downlink voice reception discontinuities before the terminal accesses the target cell, resulting in voice stuttering, missing voice segments, or temporary session interruptions.

[0005] In high-speed mobile scenarios, PTT terminals may pass through multiple 5G cells consecutively within a short period. For example, when patrol vehicles equipped with PTT terminals travel on highways or urban expressways, the terminal may quickly re-enter the coverage area of ​​other cells after completing a cell handover. Existing solutions primarily select target cells based on cell measurement results obtained during handover determination. However, if the terminal's location continues to change during the handover process, the communication conditions of the target cell after the handover may differ from those at the time of selection, easily triggering continuous cell handovers. For terminals engaged in PTT voice communication, continuous access switching and service bearer recovery may also increase voice transmission intervals, resulting in increased end-to-end latency or voice data packet loss.

[0006] The main reason for the above problems is that existing handover schemes are mostly set according to the network connection requirements of general mobile communication services. They typically use pre-set measurement periods, handover thresholds, and trigger durations, and mainly determine whether to handover and select the target cell based on the wireless signal measurement results obtained during the handover decision. This approach is not adaptable to situations where the network status changes significantly in a short period of time or the terminal quickly crosses multiple cells. This can lead to a time lag between handover decision, target cell selection, and actual handover processing, thus affecting the continuous transmission of PTT voice services during handover. Therefore, existing handover schemes may experience increased handover latency, voice data loss, and PTT voice session interruptions in scenarios with strong obstruction or high-speed movement, making it difficult to fully meet the requirements of PTT voice communication for low latency, low packet loss rate, and high reliability. Summary of the Invention

[0007] Based on this, this invention provides a 5G network adaptive handover method and system for PTT voice communication. According to the actual carrying status of the current 5G link for PTT voice frame transmission, the method dynamically determines the area handover preparation timing and the area handover execution timing. By constructing the area acceptance relationship corresponding to each candidate communication area, the method determines the accepting communication area, the communication access initiation time, and the bearer migration time. This allows PTT voice sessions to be seamlessly connected between the current service area and the accepting communication area according to the voice frame transmission process, reducing voice frame loss, transmission interruption, and session control state abnormalities during handover. This improves the continuity, timeliness, and reliability of PTT voice communication in scenarios with strong obstruction or high-speed movement. The technical solution is as follows:

[0008] On the one hand, a 5G network adaptive handover method for PTT voice communication is provided, the method comprising:

[0009] S1. Obtain the current service area measurement data, candidate communication area measurement data and PTT voice session data corresponding to the PTT terminal, determine the corresponding status between the wireless bearer resources and the PTT voice frame transmission process in the current service area, and establish the session bearer relationship between the current 5G link and the PTT voice session.

[0010] S2, based on the session bearer relationship, determines the range of voice frames that the current 5G link can continue to carry and the remaining bearer time period, and dynamically determines the area handover trigger boundary according to the PTT voice session status, generating the network handover requirement status.

[0011] S3, when the network handover demand status characterization enters the area handover preparation state, construct the area succession relationship of the PTT voice session from the current service area to each candidate communication area.

[0012] S4. When the network handover demand status is transformed from the area handover preparation state to the area handover execution state, the handover start point, handover range and handover duration recorded in each area handover relationship are sorted for the combination of the current service area and the candidate communication area to determine the handover communication area. The communication access start time and bearer migration time are generated in combination with the transmission stage of the current voice frame.

[0013] S5, according to the communication access start time, perform access preparation for the receiving communication area, and establish a communication connection between the PTT terminal and the receiving communication area at the bearer migration time, migrate the communication bearer corresponding to the PTT voice session to the receiving communication area, and determine whether the PTT voice session connection is completed based on the voice frame transmission status and session control status before and after the bearer migration.

[0014] On the other hand, a 5G network adaptive handover system for PTT voice communication is provided, the system comprising:

[0015] The session bearer construction module is used to obtain the current service area measurement data, candidate communication area measurement data and PTT voice session data corresponding to the PTT terminal, determine the corresponding status between the wireless bearer resources and the PTT voice frame transmission process in the current service area, and establish the session bearer relationship between the current 5G link and the PTT voice session.

[0016] The handover requirement determination module is used to determine the range of voice frames that the current 5G link can continue to carry and the remaining carrying time period based on the session bearer relationship, and dynamically determine the area handover trigger boundary according to the PTT voice session status to generate the network handover requirement status; the PTT voice session status includes the position of the voice frame currently being sent, the range of voice frames to be sent, and the allowed transmission time limit for each voice frame to be sent.

[0017] The regional handover construction module is used to construct the regional handover relationship for PTT voice sessions to continue from the current service area to each candidate communication area when the network handover demand status characterization enters the regional handover preparation state.

[0018] The handover planning module is used to sort the combinations of the current service area and candidate communication areas according to the handover start point, handover range and handover duration recorded in the handover relationship of each area when the network handover demand status characterization changes from the area handover preparation state to the area handover execution state. From this sorting, the receiving communication area is determined, and the communication access start time and bearer migration time are generated in combination with the transmission stage of the current voice frame.

[0019] The session continuation execution module is used to perform access preparation for the receiving communication area according to the communication access start time, and to establish a communication connection between the PTT terminal and the receiving communication area at the bearer migration time, migrate the communication bearer corresponding to the PTT voice session to the receiving communication area, and determine whether the PTT voice session continuation is completed based on the voice frame transmission status and session control status before and after the bearer migration.

[0020] The beneficial effects achieved by the provided technical solution include at least the following:

[0021] (1) This invention obtains measurement data of the current service area, measurement data of candidate communication areas, and PTT voice session data, and maps the wireless bearer resources of the current 5G link to the PTT voice frame transmission process. Based on the number of voice frames, the amount of data per frame, and the allowed transmission time limit, it can determine the remaining bearer status, critical bearer status, or insufficient bearer status within the current monitoring period. This further reflects the degree of support of the current 5G link for actual PTT voice data transmission tasks, making the network handover judgment correspond to the current voice frame transmission process, and reducing the handover judgment deviation caused by the inconsistency between signal measurement results and service bearer status.

[0022] (2) This invention determines the range of voice frames that the current 5G link can continue to carry and the remaining carrying time period, and sets the handover preparation margin and handover execution margin according to the voice frame carrying margin and carrying time margin, respectively. When the current 5G link still has sufficient carrying margin, the original communication connection is maintained. When the carrying margin decreases to the handover preparation margin, the candidate communication area measurement, resource confirmation and access preparation are completed in advance. When the carrying margin decreases to the handover execution margin, the actual handover process is started. This avoids the waste of original wireless resources caused by premature handover, and also avoids the temporary handover when the current link can no longer complete the subsequent voice frame transmission. This improves the matching degree between the area handover triggering timing and the continuous transmission requirements of PTT voice services.

[0023] (3) After the current service area enters the area handover preparation state, the present invention determines the voice frame carrying start position, voice frame carrying range, and carrying duration corresponding to each candidate communication area based on the access preparation time, allocable uplink transmission volume, single frame data volume of the voice frame to be sent, and allowed transmission time limit of each candidate communication area, and constructs the area acceptance relationship. Through this area acceptance relationship, the voice frame starting acceptance position, subsequent voice frame acceptance type, and corresponding acceptance duration of each candidate communication area can be clearly defined, so that the selection of candidate communication areas is no longer based solely on instantaneous wireless signal strength, but also considers the carrying connection between the current voice frame transmission process, thereby improving the service relevance of the candidate communication area evaluation results and reducing the risk that the target area may have good signal conditions but cannot accept subsequent PTT voice frames in time.

[0024] (4) This invention calculates the frame position difference between the start position of the voice frame carrying in each candidate communication region and the next frame after the end of the voice frame carrying the current 5G link, and combines the number of voice frames carried, the minimum cutoff margin, and the access preparation time to sort the handover combinations between the current service region and each candidate communication region, thereby determining the receiving communication region. This processing method can prioritize retaining candidate communication regions where the start position of the carrying is continuous with the end position of the current link carrying, and on this basis, prioritize selecting candidate communication regions with a large number of voice frames carried, a large minimum cutoff margin, and a short access preparation time, reducing gaps, overlaps, or insufficient carrying between voice frames before and after handover, so that the selection result of the receiving communication region directly corresponds to the continuous transmission requirements of PTT voice frames, improving the accuracy and stability of communication region selection in scenarios with strong obstruction, rapid movement, or continuous cross-regional transmission.

[0025] (5) This invention determines the communication access start time based on the current 5G link's carry time margin and the access preparation time of the receiving communication area, and determines the bearer migration time based on whether the current voice frame has been sent. This allows the acquisition of access configuration and the reservation of uplink resources in the receiving communication area to be completed in advance while the current link is still maintaining voice transmission, and no second radio resource control connection is established before the bearer migration. Subsequently, communication access and communication bearer migration are completed after the current voice frame is sent or before the next voice frame to be sent. At the same time, by comparing the sequence number of the last voice frame sent before the handover with the sequence number of the first voice frame sent after the handover, and verifying the consistency of the session identifier, the current speaker identifier, the voice sending permission identifier, and the session maintenance identifier, it is possible to determine whether the PTT voice session has been successfully connected from the perspectives of voice frame continuity and session control continuity, thereby reducing voice frame loss, duplicate transmission, abnormal speaking permissions, and session interruption, and improving the low latency, continuity, and reliability of PTT voice communication. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is a flowchart of a 5G network adaptive handover method for PTT voice communication provided according to an embodiment of the present invention;

[0028] Figure 2 This is a schematic diagram of a 5G network adaptive handover system for PTT voice communication according to an embodiment of the present invention;

[0029] Figure 3 This is a distribution diagram of voice frame double redundancy and network switching requirements provided in an embodiment of the present invention;

[0030] Figure 4 This is a timing diagram showing the change of dual redundancy after the network handover requirement state is triggered, according to an embodiment of the present invention.

[0031] Figure 5 This is a diagram showing the wireless measurement status and measurement time interval before switching, provided according to an embodiment of the present invention;

[0032] Figure 6 This is a communication access preparation startup and bearer migration delay diagram provided according to an embodiment of the present invention. Detailed Implementation

[0033] The technical solution of the present invention will now be described with reference to the accompanying drawings.

[0034] The embodiments of the present invention provide, as follows Figure 1 The flowchart shown is a 5G network adaptive handover method for PTT voice communication. The processing flow of this method may include the following steps:

[0035] S1 includes:

[0036] The uplink wireless connection between the PTT terminal and the base station in the current service area, used for transmitting the current PTT voice session data, is defined as the current 5G link. A continuous monitoring period is divided using the monitoring timer of the PTT terminal; in this embodiment, a single monitoring period is set to 100 milliseconds, and the uplink scheduling record generated by the MAC layer of the 5G communication module is read within each monitoring period. The uplink scheduling record includes the data radio bearer identifier, the number of allocated uplink resource blocks, the modulation and coding scheme, the number of occupied symbols, the transport block size, the protocol header data volume, and the actual retransmission data volume. Based on the data radio bearer identifier corresponding to the current PTT voice session, transport blocks belonging to the current PTT voice session are selected from the uplink scheduling record. The sizes of the selected transport blocks are accumulated, and the corresponding protocol header data volume and actual retransmission data volume are subtracted to obtain the available voice transmission volume for sending PTT voice frames within the current monitoring period. When no uplink transmission resources are allocated to the data radio bearer within the current monitoring period, the available voice transmission volume is determined to be 0.

[0037] Voice frames that have been encoded but have not yet started transmission at the radio access layer are read from the PTT terminal's voice transmission queue and identified as voice frames to be transmitted. Voice frames that have entered the radio access layer transmission process but have not yet returned a transmission completion flag are recorded separately as currently being transmitted voice frames and are not repeatedly included in the set of voice frames to be transmitted. A 16-bit sequence number is read from the sequence number field of the RTP data packet, and an extended voice frame sequence number is generated based on the number of wraparounds of this sequence number. The extended voice frame sequence number is equal to the product of the number of wraparounds and 65536 plus the current 16-bit sequence number. Subsequent voice frame sorting, subtraction, and increment operations are all performed based on the extended voice frame sequence number. The data size of a single frame is obtained from the voice data packet length field, and the voice frame generation time is obtained from the timestamp written when the encoder outputs the voice frame. The voice frame generation time is added to the preset maximum queuing transmission time to obtain the transmission deadline, and the time length between the transmission deadline and the current time is determined as the allowed transmission time limit. In this embodiment, the maximum queuing transmission time is set to 200 milliseconds.

[0038] The data volume of each voice frame to be transmitted is accumulated in ascending order of frame number until the accumulated data volume exceeds the available voice transmission capacity after adding the next voice frame. The number of voice frames accumulated before addition is determined as the number of voice frames that can be transmitted within the current monitoring period. The end time of the current monitoring period is used as the period determination time. The number of voice frames to be transmitted whose transmission deadline is not later than the period determination time is counted to obtain the number of voice frames that need to be transmitted within the current monitoring period.

[0039] The number of voice frames that need to be sent is subtracted from the number of voice frames that can be sent to obtain the bearer frame difference. In this embodiment, the preset bearer critical range is set to 0 to 1 frames. When the bearer frame difference is greater than 1 frame, the bearer state of the current 5G link is uniquely determined as the surplus bearer state; when the bearer frame difference is equal to 0 or 1 frame, the bearer state is uniquely determined as the critical bearer state; when the bearer frame difference is less than 0 frames, the bearer state is uniquely determined as the insufficient bearer state. The current monitoring period and the two previous complete monitoring periods are combined into a state observation window; when there are less than three complete monitoring periods after the session starts, only the bearer state of the monitoring periods that have been formed is recorded. After three consecutive complete monitoring periods are formed, the following frame-by-frame bearer range calculation based on the state observation window is performed. The surplus bearer state, critical bearer state, or insufficient bearer state corresponding to three consecutive monitoring periods are used to characterize the change in the current 5G link bearer support level, and are not directly used as the calculation operand for the estimated completion time of frame-by-frame transmission; subsequent frame-by-frame bearer judgment uniformly adopts the available voice transmission volume within this state observation window and the estimated voice transmission rate calculated from it.

[0040] When three consecutive complete monitoring cycles have been formed and there are voice frames to be sent in the voice transmission queue, the voice frame with the smallest frame sequence number is determined as the starting voice frame for transmission. The average available voice transmission volume of the current monitoring cycle and the two preceding monitoring cycles is calculated, and this average is used as the estimated available voice transmission volume for subsequent monitoring cycles. Voice frames to be sent are allocated sequentially according to their frame sequence numbers. The sum of the available voice transmission volumes of the three monitoring cycles is divided by the total duration of the three monitoring cycles to obtain the estimated voice transmission rate of the current 5G link. The data volume of each voice frame to be sent is divided by the estimated voice transmission rate to obtain the corresponding estimated transmission duration. When the estimated voice transmission rate is greater than 0, the estimated transmission duration is sequentially added according to the extended voice frame sequence number to obtain the estimated transmission completion time of each voice frame. When the estimated transmission completion time of any voice frame is not later than the corresponding transmission deadline, the voice frame is determined to meet the on-time transmission condition. When the estimated transmission completion time is later than the transmission deadline, the transmission judgment for subsequent voice frames is stopped.

[0041] When the voice transmission queue is empty, no voice frame carrying interval or voice frame double margin is generated in this monitoring period. The handover requirement determination of the current monitoring period ends and the next monitoring period begins. When the voice transmission queue is not empty but the estimated voice transmission rate is less than or equal to 0, or there are no voice frames to be sent that meet the on-time transmission conditions, it is determined that there is no voice frame interval that can continue to be carried by the current 5G link. The network handover requirement status corresponding to the current PTT voice session is directly determined as the area handover execution status. The voice frames that have not yet been sent are kept in the transmission queue and the area handover relationship is constructed in S3. The end voice frame, estimated transmission time or minimum cutoff margin is no longer calculated for the empty voice frame interval.

[0042] When at least one voice frame meets the on-time transmission condition, the last voice frame that meets the on-time transmission condition is determined as the end-of-bearing voice frame. The voice frame interval that the current 5G link can continue to carry is formed from the start-of-bearing voice frame to the end-of-bearing voice frame. The estimated transmission durations of each voice frame within the voice frame interval are summed to obtain the estimated transmission time required to complete the transmission of that voice frame interval. The difference between the transmission cutoff time and the estimated transmission completion time of each voice frame is calculated, and the minimum value is determined as the minimum cutoff margin of the current 5G link. Since the voice frame interval only includes voice frames whose estimated transmission completion time is no later than the transmission cutoff time, the minimum cutoff margin is a value not less than 0.

[0043] The link identifier, starting voice frame number, ending voice frame number, voice frame range, estimated completion time of each voice frame, estimated transmission time, and minimum cutoff margin of the current 5G link are stored accordingly to obtain the correspondence between the voice frame carrying range and transmission timing of the current 5G link for the current PTT voice session. For example, if the current 5G link identifier is L1, the starting voice frame number is 1201, the ending voice frame number is 1210, the estimated transmission time is 500 milliseconds, and the minimum cutoff margin is 80 milliseconds, then a corresponding record is established for link L1, voice frames 1201 to 1210, the estimated transmission time of 500 milliseconds, and the minimum cutoff margin of 80 milliseconds. This indicates that the current 5G link needs 500 milliseconds to send frames 1201 to 1210 according to the current estimated voice transmission rate, and the voice frame closest to the transmission cutoff time still retains an 80-millisecond time margin.

[0044] S2 includes:

[0045] The system reads the end-of-transmission voice frame number, the estimated completion time of each voice frame, and the minimum cutoff margin for the current 5G link from the correspondence between the voice frame carrying range and transmission timing. The end-of-transmission voice frame number indicates the last voice frame number that the current 5G link is expected to complete on time according to the estimated voice transmission rate, and the minimum cutoff margin indicates the minimum difference between the transmission cutoff time and the estimated completion time of each voice frame.

[0046] The system reads the head-of-line transmission record, the head-of-line record, and the tail-of-line record of the PTT terminal's voice transmission queue. The head-of-line transmission record corresponds only to currently transmitted voice frames that have entered the radio access layer transmission process but have not yet returned a transmission completion flag. The head-of-line record and the tail-of-line record correspond only to voice frames that have not yet started radio access layer transmission, thus avoiding the same voice frame being counted in both the currently transmitted set and the waiting-to-be-transmitted set. The system obtains the sequence number of the currently transmitted voice frame, the sequence number of the first voice frame to be transmitted, and the sequence number of the last voice frame to be transmitted. Based on the timestamp written when each voice frame to be transmitted is generated and the preset maximum queuing transmission time, the system calculates the transmission cutoff time, where the transmission cutoff time is the sum of the voice frame generation time and the maximum queuing transmission time. In this embodiment, the maximum queuing transmission time is set to 200 milliseconds.

[0047] When there is a currently transmitting voice frame, the number of the currently transmitting voice frame is subtracted from the number of the voice frame that ended transmission to obtain the voice frame carrying capacity. For example, if frame 1200 is currently being transmitted and frame 1210 is the voice frame that ended transmission, then the voice frame carrying capacity is 10 frames. When there is no currently transmitting voice frame but there are voice frames to be transmitted, the number of the first voice frame to be transmitted is subtracted from the number of the voice frame that ended transmission and then incremented by 1 to obtain the voice frame carrying capacity, which represents the number of voice frames that the current 5G link is expected to carry on time since the first voice frame to be transmitted. The minimum cutoff margin of the current 5G link is determined as the carrying time margin; the carrying time margin is a value not less than 0, and the larger the value, the more sufficient the time margin is reserved for the voice frame closest to the transmission cutoff time in the current voice frame interval. When S1 determines that there is no voice frame interval that can continue to be carried, the voice frame carrying capacity and carrying time margin are not calculated, and the area handover execution state is directly entered according to the processing of S1.

[0048] The system reads the candidate communication area measurement duration, resource confirmation duration, access preparation duration, communication access duration, and bearer migration duration from the successful area handover records saved on the PTT terminal. When there are at least 20 successful area handover records, the most recent 20 records are read; when there are 1 to 19 records, all existing records are read; when there are no successful area handover records, the system reads the preset handover preparation time parameter and handover execution time parameter from the terminal configuration file. In this embodiment, the preset handover preparation time parameter is set to 300 milliseconds, and the preset handover execution time parameter is set to 100 milliseconds.

[0049] The initial handover preparation time margin is determined by summing the maximum values ​​of the candidate communication area measurement duration, resource confirmation duration, and access preparation duration. The initial handover execution time margin is determined by summing the maximum value of the communication access duration and the maximum value of the bearer migration duration. The initial handover execution time margin is then used as the handover execution time margin. This initial handover preparation time margin is compared with the handover execution time margin plus a 20-millisecond voice frame interval; the larger of the two is taken as the handover preparation time margin, ensuring that the handover preparation time margin is always greater than the handover execution time margin. Finally, the handover preparation time margin and the handover execution time margin are divided by 20 milliseconds and rounded up to obtain the handover preparation frame margin and the handover execution frame margin, respectively.

[0050] Within each monitoring cycle, the network handover demand status corresponding to the current PTT voice session is uniquely determined according to the priority order of regional handover execution status, regional handover preparation status, and hold status. When the voice frame capacity remaining is less than or equal to the handover execution frame capacity remaining, the capacity remaining is less than or equal to the handover execution time remaining, or the sequence number of the voice frame ending the handover is less than the sequence number of the last voice frame to be sent, the network handover demand status is determined to be regional handover execution status. When the conditions for determining regional handover execution status are not met, and the voice frame capacity remaining is less than or equal to the handover preparation frame capacity remaining, or the capacity remaining is less than or equal to the handover preparation time remaining, the network handover demand status is determined to be regional handover preparation status. When the voice frame capacity remaining is greater than the handover preparation frame capacity remaining and the capacity remaining is greater than the handover preparation time remaining, the network handover demand status is determined to be hold status. Once the network handover demand status enters the regional handover execution status, it will not fall back to the hold status until the current handover is completed or a handover failure result is output.

[0051] When the network handover requirement status directly meets the judgment conditions for the area handover execution status from the hold status, the area acceptance relationship corresponding to the current monitoring period is first constructed according to S3; only after the area acceptance relationship is constructed will it proceed to S4.

[0052] like Figure 3The diagram shows the distribution of voice frame dual margins and network handover requirements according to an embodiment of the present invention. The horizontal axis represents the voice frame carrying margin; when there is a currently transmitting voice frame, it is the difference between the current 5G link's end voice frame sequence number and the currently transmitting voice frame sequence number, in frames; when there is no currently transmitting voice frame, it is determined by the end voice frame sequence number and the first voice frame to be transmitted sequence number. The vertical axis represents the carrying time margin, which is the minimum difference between the transmission cutoff time and the corresponding expected transmission completion time of each voice frame within the voice frame interval, in milliseconds, and is not less than 0 when a valid voice frame interval exists. The vertical dashed lines in the diagram represent a handover execution frame margin of 5 frames and a handover preparation frame margin of 15 frames, respectively; the horizontal dashed lines represent a handover execution time margin of 100 milliseconds and a handover preparation time margin of 300 milliseconds, respectively. Each scatter point corresponds to a monitoring period with a valid voice frame interval, and different markers represent the hold state, area handover preparation state, and area handover execution state, respectively. When the voice frame carrying capacity is less than or equal to 5 frames, or the carrying time capacity is less than or equal to 100 milliseconds, the corresponding monitoring period is classified as the area handover execution state. If the area handover execution state is not met, when the voice frame carrying capacity is less than or equal to 15 frames, or the carrying time capacity is less than or equal to 300 milliseconds, it is classified as the area handover preparation state. Only when the voice frame carrying capacity is greater than 15 frames and the carrying time capacity is greater than 300 milliseconds is it classified as the hold state. For monitoring periods in S1 that are directly determined to be in the area handover execution state due to the absence of a valid voice frame interval, they are not represented by double-capacity scatter plots.

[0053] like Figure 4 The figure shown is a timing diagram of the dual redundancy after the network switching demand state is triggered according to an embodiment of the present invention. Figure 4 The horizontal axis of section (a) represents the time after entering the area switching execution state, in milliseconds, and the vertical axis represents the voice frame carrying capacity, in frames. Different curves represent the changes in voice frame carrying capacity under normal movement, strong occlusion and high-speed continuous cross-area scenarios, respectively. The semi-transparent area represents the distribution range of the corresponding data within the same time range. Figure 4 The horizontal axis of section (b) also represents the time after entering the area handover execution state, in milliseconds, and the vertical axis represents the carrying time margin, in milliseconds. This figure only counts the monitoring period of the still valid voice frame interval, so the carrying time margin is defined as a value not less than 0 as mentioned above. After entering the area handover execution state, the current 5G link continues to send voice frames already configured to the link before the bearer migration process starts. As the number of voice frames that can continue to be carried decreases and the sending deadline is continuously consumed, the voice frame carrying margin and carrying time margin gradually approach the corresponding execution boundary. Among them, the voice frame carrying margin approaches the execution boundary faster in the strong obstruction scenario, and the carrying time margin is more sensitive to the time progress in the high-speed continuous cross-area scenario.

[0054] S3 includes:

[0055] When the network handover requirement status corresponding to the current PTT voice session is determined to be in the area handover preparation state, or when the area handover execution state is directly satisfied by the hold state but no effective area transfer relationship has been formed for the current monitoring period, a candidate communication area set is determined based on the candidate communication area measurement data. The candidate communication area measurement data includes the SS-RSRP report value, SS-RSRQ report value, SS-SINR report value, and the reporting time corresponding to each report value for the candidate communication area. The pre-handover measurement interval is obtained by subtracting the reporting time corresponding to each report value from the determination time of the current network handover requirement status, and the measurement interval and the corresponding wireless measurement report value are associated and stored. A maximum effective measurement interval for candidate communication area measurement data is preset; in this embodiment, it is set to 1000 milliseconds. Only wireless measurement records with a pre-handover measurement interval not greater than the maximum effective measurement interval are considered valid measurement data for the current monitoring period. Records exceeding the maximum effective measurement interval are not used for candidate communication area determination and trigger the reacquisition of wireless measurement data for the corresponding candidate communication area. If a candidate communication area does not have valid measurement data, it is not included in the current candidate communication area set. Candidate communication area refers to the candidate coverage area measured by PTT terminal, and candidate access node refers to the base station or network access device responsible for wireless access and resource scheduling in the candidate communication area.

[0056] like Figure 5 The diagram shown is a graph of the wireless measurement status and measurement time interval before switching, provided in an embodiment of the present invention. Figure 5 In section (a), the horizontal axis represents the measurement interval between the reporting time of wireless measurement data and the determination time of network handover requirement status. The measurement interval is equal to the determination time of network handover requirement status minus the reporting time of the corresponding wireless measurement report, in milliseconds. The vertical axis represents the number of wireless measurement events falling within the corresponding measurement interval, in times. The bars represent the distribution of the number of events, the curves represent the trend of the number of events with the measurement interval, and the dashed line represents the maximum effective measurement interval of 1000 milliseconds used in this embodiment. Figure 5In sections (b), (c), and (d), the horizontal axis represents the measurement interval before handover, and the vertical axis represents the SS-RSRP, SS-RSRQ, and SS-SINR report values, respectively. The attached figures in this embodiment use the quantized report values ​​directly output by the 5G communication module as the vertical axis. These values ​​are dimensionless when used as a protocol quantization index, and are expressed in dBm, dB, and dB after physical quantity conversion. The scatter plots represent single wireless measurement records, and the black broken line represents the trend of report values ​​within different measurement intervals. As shown in the figure, the candidate communication area measurement records are mainly distributed within the 1000 milliseconds before the network handover requirement is determined. This embodiment only uses the records within the maximum effective measurement interval to construct the candidate communication area set and confirm candidate access node resources.

[0057] The PTT terminal sends resource confirmation requests to candidate access nodes corresponding to each candidate communication area through the current access node corresponding to the current service area, and receives resource confirmation information returned by each candidate access node. It reads the access configuration distribution duration, terminal access response duration, and radio bearer configuration duration from the resource confirmation information. The access configuration distribution duration is determined as the access preparation duration of the corresponding candidate access node, representing the time required to acquire the access configuration and complete the target uplink resource reservation preparation. The sum of the terminal access response duration and the radio bearer configuration duration is determined as the communication access execution reference duration, used to estimate the time required from the start of the random access procedure to the completion of the target uplink data radio bearer establishment. Simultaneously, it reads the uplink transmission block size and allocation period pre-allocated by the candidate access node for the data radio bearer corresponding to the current PTT voice session. The uplink transmission block sizes within one allocation period are accumulated to obtain the allocatable uplink transmission volume for the corresponding candidate communication area. The allocatable uplink transmission volume is divided by the corresponding allocation period to obtain the estimated available uplink transmission rate for the candidate communication area.

[0058] The bearing time margin and the estimated completion time of each voice frame are read from the correspondence between the voice frame carrying range and transmission timing of the current 5G link. For each candidate communication area, the access preparation time and the communication access execution reference time of the candidate communication area are subtracted from the bearing time margin to obtain the candidate access waiting time. When the candidate access waiting time is greater than 0, the sum of the current time and the candidate access waiting time is determined as the estimated access preparation start time; otherwise, the current time is determined as the estimated access preparation start time. The sum of the estimated access preparation start time and the access preparation time is determined as the estimated access preparation completion time. When there is a voice frame currently being transmitted, the later of the estimated transmission completion time and the estimated access preparation completion time is determined as the estimated bearer migration process start time; otherwise, the estimated access preparation completion time is determined as the estimated bearer migration process start time. Finally, the sum of the estimated bearer migration process start time and the communication access execution reference time is determined as the estimated bearer establishment completion time. The last voice frame in the current 5G link whose expected completion time is no later than the expected completion time of the corresponding candidate communication area's bearer establishment is determined as the access front-end voice frame, and the next extended voice frame of the access front-end voice frame is determined as the start position of the voice frame bearer in the corresponding candidate communication area.

[0059] Starting from the beginning position of the voice frame bearer, the data volume of each single frame of the voice frame to be sent is read sequentially according to the extended voice frame sequence number. The data volume of each single frame is divided by the estimated available uplink transmission rate of the candidate communication area to obtain the estimated transmission duration of the corresponding voice frame in the candidate communication area. Starting from the estimated bearer establishment completion time, the estimated transmission duration is accumulated sequentially according to the voice frame sequence number to obtain the estimated transmission completion time of each voice frame. When the estimated transmission completion time is not later than the transmission deadline of the corresponding voice frame, the voice frame is included in the range of the carried voice frames; when the estimated transmission completion time is later than the transmission deadline, inclusion in subsequent voice frames is stopped.

[0060] When at least one voice frame meeting the transmission deadline requirement exists from the start position of the voice frame carrier, a voice frame carrying range is formed from the start position to the last voice frame meeting the transmission deadline requirement. The number of voice frames within this range is counted. The estimated transmission durations of each voice frame are summed to obtain the estimated transmission time required for the candidate communication region to complete the transmission of this voice frame carrying range. The difference between the transmission deadline and the estimated transmission completion time of each voice frame is calculated, and the minimum value is determined as the minimum cutoff margin of the candidate communication region. When no voice frame meeting the transmission deadline requirement exists from the start position of the voice frame carrier, no region acceptance relationship is generated for this candidate communication region, and the candidate communication region is excluded from the current valid acceptance candidates.

[0061] Using each candidate communication region as an index, the corresponding candidate access node, voice frame start position, voice frame range, number of voice frames carried, estimated transmission time, minimum cutoff margin, estimated access preparation start time, estimated access preparation completion time, estimated bearer migration process start time, and estimated bearer establishment completion time are recorded to form an effective regional acceptance relationship for the current monitoring period. For example, candidate communication region A corresponds to candidate access node A1, frames 1211 to 1225, frame 15, estimated transmission time of 300 milliseconds, and minimum cutoff margin of 60 milliseconds. This means that candidate access node A1 will accept frames 1211 to 1225 starting from frame 1211, and the transmission within this range is expected to take 300 milliseconds, with the voice frame with the smallest time margin still retained for 60 milliseconds.

[0062] S4 includes:

[0063] When the network handover requirement for the current PTT voice session is determined to be in the area handover execution state, the area transfer relationship generated in the current monitoring period is read. If there is no valid area transfer relationship in the current monitoring period, the process first returns to S3 to construct the area transfer relationship, without directly executing the candidate communication area sorting. Before executing the sorting, it is checked again that the candidate communication area measurement data on which each area transfer relationship is based still meets the maximum valid measurement interval, and that the candidate access node corresponding to the resource confirmation information is consistent with the record in the current monitoring period. Area transfer relationships that do not meet the above conditions do not participate in this sorting, and the process returns to S3 to re-obtain the corresponding measurement data or resource confirmation information.

[0064] The starting position of voice frame carrying, the number of voice frames carried, the access preparation time and the minimum cutoff margin are read from the connection relationship of each region. The ending voice frame sequence number and the minimum cutoff margin of the current 5G link are read from the correspondence between the voice frame carrying range and the transmission timing of the current 5G link.

[0065] The frame position difference is obtained by subtracting the extended voice frame sequence number corresponding to the start position of the voice frame in each candidate communication area from the sum of the current 5G link end voice frame sequence number and one. A frame position difference of 0 indicates that the candidate communication area will start accepting the next frame after the current 5G link end voice frame; a frame position difference greater than 0 indicates that there are unaccepted voice frames between the current 5G link end position and the candidate communication area start position; a frame position difference less than 0 indicates that there are duplicate voice frames between the two bearer ranges.

[0066] Only candidate communication regions with a frame position difference of 0 are retained as valid acceptance candidates to avoid omission or duplication of voice frames after bearer handover. When no candidate communication region with a frame position difference of 0 exists, the region acceptance relationship is output as unavailable, the voice frame to be sent remains in the sending queue, and the process returns to S3 to reacquire resource confirmation information for the candidate access node. If, after constructing the region acceptance relationship based on the reacquired resource confirmation information, no valid acceptance candidate with a frame position difference of 0 still exists, the handover failure result is output, the region handover execution process ends, and the network handover requirement status corresponding to the current PTT voice session is re-determined in the next monitoring cycle. For valid acceptance candidates with a frame position difference of 0, they are first sorted in descending order of the number of voice frames carried; when the number of voice frames carried is the same, they are sorted in descending order of the minimum cutoff margin; when the minimum cutoff margin is still the same, they are sorted in ascending order of access preparation time. The candidate communication region corresponding to the first ranked candidate is determined as the acceptance communication region, and the candidate access node corresponding to this candidate communication region is determined as the acceptance access node.

[0067] The expected access preparation start time, expected access preparation completion time, expected bearer migration process start time, and expected bearer establishment completion time are read from the area acceptance relationship corresponding to the communication acceptance area. The expected access preparation start time and expected bearer migration process start time are then determined as the communication access preparation start time and bearer migration process start time for this handover, respectively. Since the above times have already been uniformly calculated in S3 according to the current 5G link bearer time margin, access preparation duration, expected completion time of current voice frame transmission, and communication access execution reference duration, S4 does not recalculate the voice frame bearer start position or access waiting duration using different time bases.

[0068] like Figure 6 The diagram shown is a delay diagram of the communication access preparation and bearer migration process provided in an embodiment of the present invention. Figure 6The horizontal axis of section (a) represents the delay relative to the trigger time of the area handover execution state, in milliseconds. Specifically, the communication access preparation start delay equals the communication access preparation start time minus the area handover execution state trigger time, and the bearer migration process start delay equals the bearer migration process start time minus the area handover execution state trigger time. The vertical axis represents the handover decision sequence number obtained by arranging each handover decision in this embodiment according to the bearer migration process start delay from smallest to largest. This only indicates the sample arrangement order and is a dimensionless sequence number. Blue scatter dots represent the communication access preparation start delay corresponding to each handover decision, and orange scatter dots represent the corresponding bearer migration process start delay. If the communication access preparation start delay in the same handover decision is less than or equal to the bearer migration process start delay, it means that the receiving access node first completes the access configuration acquisition and uplink resource reservation preparation, and then initiates random access, radio resource control connection establishment, and uplink data radio bearer configuration after the current voice frame is sent and access preparation is completed. Figure 6 The horizontal axis of section (b) represents three operating scenarios: normal movement, strong occlusion, and high-speed cross-regional operation. The vertical axis represents the start-up latency of the bearer migration process, in milliseconds. The violin outline and scatter points represent the distribution range of the start-up latency of the bearer migration process and the single handover record under each scenario.

[0069] The system reads the transmission completion flag of the current voice frame and determines the bearer migration procedure initiation condition based on the estimated access preparation completion time recorded in S3. If the current voice frame has not yet been transmitted, the bearer migration procedure is initiated when the current voice frame actually returns a transmission completion flag and the system clock is not earlier than the estimated access preparation completion time. If the current voice frame has already been transmitted or there are no voice frames currently being transmitted, the bearer migration procedure is initiated when the system clock reaches the estimated access preparation completion time. The bearer migration procedure initiation time only indicates the start time of random access and subsequent radio bearer establishment procedures, and does not indicate that the radio bearer in the receiving communication area has been established. The next voice frame to be transmitted is only transmitted through the receiving communication area after receiving the radio bearer establishment completion flag returned by the receiving access node.

[0070] S5 includes:

[0071] When the system clock reaches the communication access preparation start time, the PTT terminal receives the access configuration information corresponding to the receiving access node through the current 5G link. The receiving access node reserves uplink resources according to the resource confirmation result. During this stage, no second radio resource control connection is established, and the current 5G link continues to send the current voice frame already configured to this link. If it is found that the candidate communication area measurement data has exceeded the maximum effective measurement interval before the bearer migration process starts, or if the candidate access node corresponding to the resource confirmation information is inconsistent with the current effective area acceptance relationship, the start of this bearer migration process is canceled, and the process returns to S3 to reconstruct the area acceptance relationship.

[0072] When the system clock reaches the start time of the bearer migration process and the aforementioned conditions for the completion of current voice frame transmission are met, the configuration of new PTT voice frames to the current 5G link is stopped. The PTT terminal sends a random access request to the receiving access node according to the access configuration information, and sequentially completes the reception of access response, establishment of radio resource control connection, and configuration of uplink data radio bearer. When the radio bearer establishment completion flag returned by the receiving access node is received, the reception time of the flag is determined as the bearer handover completion time. Only after the bearer handover completion time is the data radio bearer flag corresponding to the subsequent voice frames to be sent switched to the data radio bearer flag corresponding to the receiving communication area, and the first voice frame to be sent is sent from the voice frame bearer start position recorded in the area receiving relationship. If the random access, radio resource control connection establishment, or uplink data radio bearer configuration returns a failure flag, the handover failure result is output, the voice frames that have not yet obtained the transmission completion flag are kept in the transmission queue, the current area handover execution process ends, and the network handover requirement status is re-determined in the next monitoring cycle.

[0073] A session bearer association table is established locally on the PTT terminal, and the session identifier, current speaker identifier, voice transmission permission identifier, session hold identifier, and sequence number of the first extended voice frame to be sent of the current PTT voice session are associated and stored with the data radio bearer identifier corresponding to the communication area. The application layer session identifier is not written into the network-side radio bearer configuration.

[0074] Read the sequence number of the last extended voice frame that returned a transmission completion identifier before the bearer handover from the radio access layer transmission completion record of the current 5G link, and increment the extended voice frame sequence number by one to obtain the target connection voice frame sequence number; read the sequence number of the first extended voice frame that returned a transmission completion identifier after the bearer handover from the radio access layer transmission completion record corresponding to the receiving communication area.

[0075] Read the session identifier, current speaker identifier, voice transmission permission identifier, and session hold identifier from the local session control record saved before the bearer handover, and read the corresponding identifiers from the local session control record updated after the first voice frame is sent in the receiving communication area.

[0076] When the sequence number of the first extended voice frame to be transmitted after a bearer switch is equal to the sequence number of the target connected voice frame, and the session identifier, current speaker identifier, voice transmission permission identifier, and session hold identifier are the same before and after the bearer switch, it is determined that the uplink voice frame transmission bearer of the local radio access layer of the PTT speaking terminal has completed continuous connection, and the radio bearer context corresponding to the current 5G link is released; otherwise, it is determined that the uplink voice frame transmission bearer of the local radio access layer of the PTT speaking terminal has not completed continuous connection, the connection verification result is output, the voice frames that have not yet obtained the transmission completion identifier are retained in the transmission queue, the current bearer switch process ends, and the network switch requirement status is re-determined in the next monitoring cycle. This determination is only used to confirm whether the uplink transmission bearer of the local radio access layer of the PTT speaking terminal is continuous, and is not used to indicate whether the receiving end has received the corresponding voice frame, nor is it used to directly determine the downlink voice reception status of all PTT session members.

[0077] It should be noted that both the area handover preparation state and the area handover execution state refer to the network handover demand state corresponding to the current PTT voice session, not the state of the current service area itself. When the network handover demand state enters the area handover preparation state, the current 5G link continues to transmit the PTT uplink voice frames already allocated to that link, and obtains the access preparation time, allocable uplink transmission volume, and estimated frame-by-frame transmission completion time of the candidate access nodes to construct the effective area handover relationship for the current monitoring period.

[0078] When the network handover requirement enters the area handover execution state, it is first confirmed that a valid area acceptance relationship for the current monitoring period has been generated. Then, the acceptance communication area is determined from the candidate communication areas where the frame position difference is equal to 0, and the communication access preparation start time and bearer migration process start time are determined according to the unified time base in the area acceptance relationship. After receiving the radio bearer establishment completion flag returned by the acceptance access node, the bearer handover completion time is determined. When the monitoring result directly meets the area handover execution conditions from the hold state, the area acceptance relationship is first constructed, and then the acceptance communication area determination and bearer migration process are executed to avoid directly executing the handover when no area acceptance relationship exists.

[0079] The embodiments of the present invention provide, as follows Figure 2 The diagram shown illustrates the structure of a 5G network adaptive handover system for PTT voice communication. This system may include:

[0080] The session bearer construction module is used to acquire current service area measurement data, candidate communication area measurement data and PTT voice session data, analyze the corresponding status between the current service area wireless bearer resources and the voice frame transmission process, determine the bearer range and bearer duration of the voice frames to be sent on the current 5G link, and establish the session bearer relationship between the current 5G link and the PTT voice session.

[0081] The handover requirement determination module is used to determine the range of voice frames that the current 5G link can continue to carry and the remaining carrying time period based on the session carrying relationship. It calculates the voice frame carrying capacity and carrying time capacity by combining the current voice frame transmission position, the voice frame to be transmitted at the end and the transmission deadline, and generates the network handover requirement status based on the corresponding handover capacity.

[0082] The regional acceptance construction module is used to obtain the access preparation time and allocable uplink transmission volume of each candidate communication area when the current service area enters the regional handover preparation state, determine the voice frame carrying start position, voice frame carrying range and carrying duration corresponding to each candidate communication area, and construct the regional acceptance relationship for the continuation of PTT voice sessions to each candidate communication area.

[0083] The handover planning module is used to sort the handover connections based on the frame position difference, the number of voice frames carried, the minimum cutoff margin, and the access preparation time when the current service area enters the area handover execution state. The candidate communication area with the highest ranking is determined as the receiving communication area, and the communication access start time and bearer migration time are determined in combination with the current voice frame transmission status.

[0084] The session continuation execution module is used to obtain the access configuration information of the receiving communication area at the time of communication access startup and reserve uplink resources for the receiving access node. Before the bearer migration, it maintains the current 5G link and does not establish a second radio resource control connection. At the time of bearer migration, it completes the communication access of the PTT terminal to the receiving communication area and migrates the communication bearer corresponding to the PTT voice session to the receiving communication area. It compares the voice frame sequence number and session control identifier before and after the handover to determine whether the PTT voice session has been successfully continued.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. For those skilled in the art, any technical solution that employs the same or substantially equivalent technical means as the present invention to achieve continuous transmission of uplink voice frames between different communication regions in a PTT speaking terminal should fall within the scope of protection of the present invention.

Claims

1. A 5G network adaptive handover method for PTT voice communication, characterized in that, The method includes: S1. Obtain the current service area measurement data, candidate communication area measurement data and PTT voice session data corresponding to the PTT terminal, determine the corresponding status between the wireless bearer resources and the PTT voice frame transmission process in the current service area, and establish the session bearer relationship between the current 5G link and the PTT voice session. S2, based on the session bearer relationship, determines the voice frame range and remaining bearer time period that the current 5G link can continue to carry, and dynamically determines the area handover trigger boundary according to the PTT voice session status, and generates the network handover requirement status; The PTT voice session status includes the position of the currently being sent voice frame, the range of voice frames to be sent, and the allowed sending time limit for each voice frame to be sent. S3, When the network handover demand status characterization enters the area handover preparation state, construct the area succession relationship of the PTT voice session from the current service area to each candidate communication area; S4. When the network handover demand status is represented from the area handover preparation state to the area handover execution state, the handover start point, handover range and handover duration recorded in each area handover relationship are sorted for the combination of the current service area and the candidate communication area to determine the handover communication area, and the communication access start time and bearer migration time are generated in combination with the transmission stage of the current voice frame. S5, according to the communication access start time, perform access preparation for the receiving communication area, and establish a communication connection between the PTT terminal and the receiving communication area at the bearer migration time, migrate the communication bearer corresponding to the PTT voice session to the receiving communication area, and determine whether the PTT voice session connection is completed based on the voice frame transmission status and session control status before and after the bearer migration.

2. The 5G network adaptive handover method for PTT voice communication as described in claim 1, characterized in that, S1 includes: Obtain the available voice transmission volume of the current 5G link within the current monitoring period, and obtain the frame sequence number, single frame data volume, and allowed transmission time limit of each voice frame to be sent in the current PTT voice session; The data volume of each voice frame to be sent is accumulated sequentially according to the voice frame sequence number. The number of voice frames whose accumulated data volume does not exceed the available voice transmission volume is determined as the number of voice frames that can be sent within the current monitoring period. Based on the allowed transmission time limit of each voice frame to be sent, the number of voice frames that need to be sent within the current monitoring period is counted. The number of voice frames that need to be sent is subtracted from the number of voice frames that can be sent within the current monitoring period to obtain the carrying frame difference. When the difference between the bearer frames is greater than the upper limit of the preset bearer critical range, the support status of the current 5G link for the current PTT voice frame transmission process is determined as the reserve bearer status. When the bearer frame difference is within the preset bearer critical range, the current 5G link's support status for the current PTT voice frame transmission process is determined as the critical bearer state. When the difference between the bearer frames is less than the lower limit of the preset bearer critical range, the current 5G link’s support status for the current PTT voice frame transmission process is determined to be an insufficient bearer status. The remaining capacity, critical capacity, or insufficient capacity status determined within a continuous monitoring period characterizes the current 5G link's capacity support for PTT voice frame transmission.

3. The 5G network adaptive handover method for PTT voice communication as described in claim 2, characterized in that, S1 further includes: Taking the first voice frame to be sent in the current PTT voice session as the starting position of the bearer, according to the remaining bearer status, critical bearer status or insufficient bearer status corresponding to each monitoring cycle, the voice frame sequence number is used to determine whether each voice frame to be sent can be sent within the corresponding allowed sending time limit, and the last voice frame that can be sent on time is determined as the end position of the bearer. The voice frame interval that the current 5G link can continue to carry is formed from the start position to the end position of the bearer. Based on the transmission duration of each voice frame in the voice frame interval, the remaining bearer time period required for the current 5G link to complete the transmission of the voice frame interval is determined. The transmission duration of each voice frame is accumulated according to the voice frame sequence number to obtain the expected transmission completion time of each voice frame. By mapping the current 5G link to the range of voice frames that can continue to be carried, the remaining carrying time period, and the expected completion time of each voice frame, the correspondence between the voice frame carrying range and carrying time of the current 5G link for the current PTT voice session is obtained.

4. The 5G network adaptive handover method for PTT voice communication as described in claim 3, characterized in that, S2 includes: Extract the end voice frame and remaining time period of the current 5G link from the correspondence between the voice frame carrying range and carrying duration; The PTT terminal obtains the sequence number of the currently being transmitted voice frame, the sequence number of the first voice frame to be transmitted, and the sequence number of the last voice frame to be transmitted from the voice frame transmission queue, and determines the corresponding transmission deadline based on the allowed transmission time limit for each voice frame to be transmitted. The difference between the sequence number of the voice frame that has ended transmission and the sequence number of the voice frame that is currently being transmitted is determined as the voice frame transmission margin. Calculate the difference between the transmission cutoff time and the corresponding expected transmission completion time for each voice frame that the current 5G link can continue to carry, and determine the minimum value as the carrying time margin.

5. The 5G network adaptive handover method for PTT voice communication as described in claim 4, characterized in that, S2 further includes: When both the voice frame carrying capacity and the carrying time capacity are higher than their respective handover preparation capacity, it is determined that the current service area is in a hold-up state. When either the voice frame carrying capacity or the carrying time capacity decreases to the corresponding handover preparation capacity, and both are higher than their respective handover execution capacity, the current service area is determined to enter the area handover preparation state. When either the voice frame carrying capacity or the carrying time capacity decreases to the corresponding handover execution capacity, or when the voice frame carrying the end of the carrying is earlier than the voice frame waiting to be sent at the end, the current service area is determined to enter the area handover execution state. The handover preparation margin is the number of voice frames and the carrying time reserved to complete the candidate communication area measurement, resource confirmation and access preparation; The switching execution margin is the minimum number of voice frames and the carrying time reserved to complete the communication access and voice bearer migration.

6. The 5G network adaptive handover method for PTT voice communication as described in claim 5, characterized in that, S3 includes: When the current service area enters the area handover preparation state, the access preparation time and allocable uplink transmission volume corresponding to each candidate communication area are obtained, and the voice frame bearing start position corresponding to each candidate communication area after the access preparation is completed is determined in combination with the remaining bearing time of the current 5G link. Based on the allocable uplink transmission volume, the single-frame data volume of each voice frame to be sent, and the allowed transmission time limit, the expected transmission completion time of each voice frame to be sent is calculated sequentially according to the voice frame sequence number. The range of voice frames to be carried and the carrying duration corresponding to each candidate communication area are determined, and the minimum value of the difference between the transmission cutoff time and the expected transmission completion time of each voice frame within the range of voice frames to be carried is determined as the minimum cutoff margin. Using each candidate communication region as an index, the starting position of its corresponding voice frame is taken as the start point of acceptance, the range of voice frames carried is taken as the acceptance range, the carrying duration is taken as the acceptance duration, and the minimum cutoff margin is taken as the acceptance time margin. These are then configured to the corresponding candidate communication regions to obtain the region acceptance relationship.

7. The 5G network adaptive handover method for PTT voice communication as described in claim 6, characterized in that, S4 includes: Obtain the frame position difference between the start position of the voice frame bearer in each candidate communication region and the next frame after the end of the voice frame bearer in the current 5G link, and obtain the number of voice frames carried in each candidate communication region, the minimum cutoff margin, and the access preparation time. Candidate communication regions with a frame position difference of 0 are identified as valid reception candidates; The valid candidates for connection are sorted in descending order of the number of voice frames carried, descending order of the minimum cutoff margin, and ascending order of access preparation time. The candidate communication area corresponding to the first position in the sort is determined as the communication area to be connected. If there are no valid successor candidates with a frame position difference of 0, return to S3 to rebuild the region successor relationship.

8. The 5G network adaptive handover method for PTT voice communication as described in claim 7, characterized in that, S4 further includes: Obtain the access preparation time of the communication area to be taken over and the current 5G link bearing time margin. Subtract the access preparation time from the bearing time margin to obtain the access preparation waiting time. When the access preparation waiting time is greater than 0, the sum of the current time and the access preparation waiting time is determined as the communication access start time; when the access preparation waiting time is less than or equal to 0, the current time is determined as the communication access start time. If the current voice frame has not yet been sent, the moment when the current voice frame is sent and the receiving communication area has completed access preparation is determined as the bearer migration moment. If the current voice frame has been sent, the time between the completion of access preparation in the receiving communication area and the start of transmission of the next voice frame to be sent is determined as the bearer migration time, so that the next voice frame to be sent can continue to be transmitted from the voice frame bearer start position corresponding to the receiving communication area.

9. A 5G network adaptive handover method for PTT voice communication as described in claim 8, characterized in that, The determination of whether a PTT voice session has been successfully connected includes: Obtain the sequence number of the last voice frame sent before the bearer switch and the sequence number of the first voice frame sent after the bearer switch. Increment the sequence number of the last voice frame sent before the bearer switch to obtain the sequence number of the target connected voice frame. Obtain the session identifier, current speaker identifier, voice transmission permission identifier, and session hold identifier before and after the bearer switch; When the sequence number of the first voice frame sent after the bearer switch is equal to the sequence number of the target connected voice frame, and all the above-mentioned identifiers are consistent before and after the bearer switch, the PTT voice session connection is confirmed to be complete. Otherwise, it indicates that the PTT voice session connection has not been completed.

10. A 5G network adaptive handover system for PTT voice communication, employing the 5G network adaptive handover method for PTT voice communication as described in any one of claims 1-9, characterized in that, The system includes: The session bearer construction module is used to obtain the current service area measurement data, candidate communication area measurement data and PTT voice session data corresponding to the PTT terminal, determine the corresponding status between the wireless bearer resources and the PTT voice frame transmission process in the current service area, and establish the session bearer relationship between the current 5G link and the PTT voice session. The handover requirement determination module is used to determine the range of voice frames that the current 5G link can continue to carry and the remaining carrying time period based on the session bearer relationship, and dynamically determine the area handover trigger boundary according to the PTT voice session status to generate the network handover requirement status. The regional handover construction module is used to construct the regional handover relationship of PTT voice sessions from the current service area to each candidate communication area when the network handover demand status characterization enters the regional handover preparation state. The handover planning module is used to sort the combinations of the current service area and candidate communication areas according to the handover start point, handover range and handover duration recorded in the handover relationship of each area when the network handover demand status characterization changes from the area handover preparation state to the area handover execution state, thereby determining the handover communication area, and generating the communication access start time and bearer migration time in combination with the transmission stage of the current voice frame. The session continuation execution module is used to perform access preparation for the receiving communication area according to the communication access start time, and to establish a communication connection between the PTT terminal and the receiving communication area at the bearer migration time, migrate the communication bearer corresponding to the PTT voice session to the receiving communication area, and determine whether the PTT voice session continuation is completed based on the voice frame transmission status and session control status before and after the bearer migration.

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