A multi-mode compatible wireless display link switching method and system

Abstract

This invention discloses a multi-standard compatible wireless display link switching method and system, relating to the fields of wireless display and multi-wireless network switching technology. It addresses the problem of frequent interruptions in wireless displays when multiple standards coexist (WLAN infrastructure, WLAN direct connection, cellular, etc.) and link quality fluctuates, making it impossible to uniformly evaluate and stably and with low interruption complete link switching. The transmitting end establishes a link context containing session numbers and timestamps. RSSI, SNR, retransmission, RTT, packet loss, throughput, and jitter are collected from the primary and auxiliary links according to a unified standard, and normalized and weighted to form a score. Based on historical window thresholds, drop rates, and trend slopes, it determines whether to trigger a switch and selects a target link. During the switching phase, adaptive redundancy and confirmation thresholds are combined with the bearer margin ratio, structural volatility, and switch execution time budget coefficient. Successful confirmation leads to switch submission; failure results in a rollback, ensuring the continuity and stability of the wireless display.

Description

Technical Field

[0001] This invention relates to the field of wireless display and multi-wireless network switching technology, and more specifically, to a multi-standard compatible wireless display link switching method and system. Background Technology

[0002] Wireless display services are highly sensitive to latency, jitter, and packet loss. In current network environments, terminals often have multiple wireless interfaces, including WLAN infrastructure, WLAN direct connection, and cellular interfaces. Due to differences in coverage, interference intensity, channel congestion, AP load, and operator policies, the quality of a single link can fluctuate rapidly with location and time, leading to screen stuttering, display distortion, audio-visual asynchrony, and even session interruption. Existing solutions often employ roaming within a single standard or simple link-based handover, lacking unified metrics and comparable evaluations across standards. Furthermore, inconsistent link quality metrics make it difficult to make consistent decisions across different standards. Some solutions directly disconnect the old system and connect to the new one during handover, easily introducing long reconnection times and media sequence discontinuities. Even when parallel or redundant approaches are used, they often operate with fixed thresholds or fixed redundancy, making it difficult to address queuing amplification issues when throughput margin is insufficient, as well as the risk of false acknowledgments caused by short-term false good windows.

[0003] To address the above problems, this invention proposes a solution. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, the embodiments of the present invention provide a multi-standard compatible wireless display link switching method and system to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: In a preferred embodiment, it includes: Maintain multi-standard candidate links in the link context, determine the primary link based on the link reachability verification results, and register the remaining available links as auxiliary links; Update the link quality collection records for the main link and each auxiliary link according to the collection time window, generate a normalized link quality parameter set and link quality score, and retain historical window data; The handover determination record is updated based on the link quality score sequence. The quality degradation of the primary link is calculated and written into the handover trigger flag in combination with the threshold set. When triggered, the target link identifier is determined from the auxiliary links. After writing the media sequence reference number and the transmit buffer occupancy into the link handover execution record, the target link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time, and target bit rate of wireless display media data are read. The bearer margin ratio, structural fluctuation, and handover execution time budget coefficient are calculated comprehensively. Parallel transmission window parameters and fragment-level redundant transmission parameters are generated and dual-link parallel transmission is driven. The handover confirmation request message and receive status summary are exchanged and the parameters are updated accordingly or the handover and rollback are submitted.

[0006] In a preferred embodiment, when initiating a wireless display service, the transmitting end generates a wireless display session identifier containing a session number and a session establishment timestamp, and creates a link context in local storage, writing the session identifier to associate and save candidate link records and link parameter records. Based on the candidate link discovery results, the transmitting end generates a link identifier for each candidate link, which is a combination of the standard type, local interface identifier, and access point identifier or peer identifier, and writes it into the link context. At the same time, it parses the access capability field or negotiation capability field to generate link access parameters containing authentication method and encryption method, and writes them into the link context. Furthermore, it reads the access credential index and obtains the session key handle, and writes them into the link access parameters.

[0007] In a preferred embodiment, the sending end generates link routing parameters including the local network address, the peer network address, and the peer transmission port and writes them into the link context. Then, it initiates association, networking, or direct connection establishment on each candidate link according to the link access parameters and records the access status. Next, it sends probe messages to the peer network address and records the probe initiation timestamp and probe response timestamp. Based on the difference of the timestamps, it calculates the round-trip time and writes it into the link context. Finally, based on the round-trip time, it selects the primary link from multiple available candidate links and registers the remaining links as auxiliary links and writes them into the link context.

[0008] In a preferred embodiment, the transmitting end establishes link quality acquisition records for the main link and each auxiliary link in the link context, with the link identifier as the index key. Within each acquisition time window, it acquires the received signal strength indication value, signal-to-noise ratio, retransmission count, round-trip delay, packet loss rate, effective throughput, and jitter. The measured values ​​and the corresponding parameter acquisition timestamps are written into the original link quality parameter set. The transmitting end reads the link quality normalization parameter table indexed by standard type, the wireless interface configuration, and the target bitrate of the wireless display media data in the link context from the link context. It determines the upper and lower bounds of the normalization interval for each original parameter, and uses forward linear normalization for the forward parameters and reverse linear normalization for the reverse parameters to generate a normalized link quality parameter set. The normalization upper bound of the effective throughput is taken as the target bitrate of the wireless display media data to map the throughput to the service demand scale. The sending end further reads the link quality weight parameter table from the link context, calculates the link quality score by weighting and summing each normalized result according to the weight coefficient, and writes it into the link quality acquisition record. Finally, at the end of the acquisition time window, the start and end timestamps of the time window, the original link quality parameter set, the normalized link quality parameter set and the link quality score are written into the link context, and the link quality acquisition record of the acquisition time window is retained according to the preset number of historical windows.

[0009] In a preferred embodiment, the sending end establishes a handover determination record in the link context with the session number as the index key, and reads the timestamp range of the most recent consecutive collection time windows from the link quality collection record at each determination timestamp as the collection time window set used for determination. At the same time, it reads the link quality scores of the main link and each auxiliary link within the window range to form a scoring sequence. The sending end calculates the link quality degradation amount of adjacent windows and the link quality trend slope across multiple windows based on the main link scoring sequence, and reads the minimum link quality score threshold, the main link link quality degradation amount threshold, the main link link quality trend slope threshold and the link quality score difference threshold from the link context and writes them into the handover determination record. Then, it compares the main link score of the most recent collection time window with the minimum main link score threshold, compares the degradation amount with the degradation amount threshold, and compares the trend slope with the trend slope threshold, and writes the comparison results into the handover trigger flag and handover reason fields. When the handover trigger flag is triggered, the sending end reads the link quality score of each auxiliary link in the most recent acquisition time window and calculates the score difference relative to the main link. The score difference is compared with the score difference threshold, and a set of candidate target links and their link identifiers are generated and written into the handover decision record. If there are candidate target links, the normalized link quality parameter set and the round-trip delay record of the link reachability verification stage in the most recent acquisition time window of the candidate target links are further read. After sorting according to multiple criteria such as link quality score, round-trip delay and system type priority, the link identifier of the first ranked candidate link is written into the target link link identifier field, and the handover decision record is associated with the decision timestamp and written into the link context.

[0010] In a preferred embodiment, the sending end establishes a link handover execution record in the link context, using the determination timestamp and the target link identifier as index keys, and writes the handover start timestamp, handover execution status, media sequence reference number, transmission buffer occupancy, target link pre-connection status, dual-link parallel transmission status, reception acknowledgment status, and backoff trigger flag. The sending end reads the target link identifier from the most recent handover determination record, and reads the target link's link access parameters and link routing parameters as handover execution inputs. On the target link, it initiates association, network formation, or direct connection establishment according to the authentication method, encryption method, and access credential index, and sends a connectivity probe message based on the peer network address and peer transmission port. The link layer access result and network layer connectivity result are written to the target link pre-connection status and the link handover execution record. Subsequently, the difference between the write pointer and read pointer of the transmit buffer is read to obtain the transmit buffer occupancy and written into the link switching execution record. The media sequence reference number maintained during media fragmentation and encapsulation is read and written into the link switching execution record. After writing the transmit buffer occupancy and the media sequence reference number, the transmitting end reads the link quality score sequence and normalized link quality parameter set of the target link from the link quality acquisition record for the most recent consecutive acquisition time windows. It also reads the original effective throughput, packet loss rate, jitter, and round-trip delay within the most recent acquisition time window. At the same time, it reads the target bitrate of the wireless display media data obtained by statistical analysis of the bitrate output by the video encoder from the link context. The transmit end then writes the link quality score sequence, normalized link quality parameter set, original effective throughput, packet loss rate, jitter, round-trip delay, and target bitrate of the wireless display media data into the link switching execution record.

[0011] In a preferred embodiment, the transmitting end calculates the carrying margin ratio based on the original effective throughput of the target link and the target bit rate of the wireless display media data. It then calculates the structural volatility based on the statistical variation amplitude of adjacent windows in the normalized results of effective throughput, packet loss rate, and jitter in the normalized link quality parameter set. Finally, it calculates the handover execution time budget coefficient based on the difference between the transmit buffer occupancy and the media sequence reference number in adjacent time slices. Based on this, it generates parallel transmit window parameters and fragment-level redundant transmit parameters, writes them into the link handover execution record, and writes them into the dual-link parallel transmit status. The parallel transmit window parameters include the parallel transmit start media sequence number determined by the media sequence reference number and the parallel transmit end media sequence number obtained by adjusting the transmittable fragment range corresponding to the transmit buffer occupancy and the handover execution time budget coefficient. The fragment-level redundant transmit parameters include the target link redundancy ratio, the target link transmit rhythm, and the fragment priority rule generated by the fragment type flag.

[0012] In a preferred embodiment, the transmitting end generates a media sequence number for each media data fragment from the media sequence base number and fragment sequence number within the parallel transmission window, and transmits them via the main link and the target link respectively. On the target link side, the same media sequence number is repeatedly transmitted according to the fragmentation priority rules and the target link redundancy ratio. Simultaneously, a switching acknowledgment request message carrying the target link identifier, the parallel transmission start media sequence number, the parallel transmission end media sequence number, the continuous reception threshold, the consistency threshold, and the acknowledgment timeout parameters is transmitted via the target link. The display end receives the media data fragments from the main link and the target link, parses the media sequence numbers, performs deduplication on duplicate fragments with the same media sequence number, and sends them for decoding and rendering in the order of the media sequence numbers. The display end then transmits the media data fragments according to the aforementioned parallel transmission start media sequence number and parallel transmission end media sequence number. On the target link, a receive status digest is generated by statistically analyzing the continuity of media sequence numbers. This digest includes the maximum consecutive received media sequence number, the count of missing media sequence numbers, the count of out-of-order media sequence numbers, and the receive buffer status flag. This digest is then sent back to the sender via a handover acknowledgment message, a receive status receipt message, or by embedding the receive status digest into the application layer handshake response or the link layer hold message payload field. The sender updates the fragment-level redundant transmission parameters, the acknowledgment threshold parameter set, and the parallel transmission termination media sequence number based on the receive status digest and writes them into the link handover execution record. Alternatively, upon receiving a handover acknowledgment message, the sender rewrites the primary link identifier and the candidate primary link flag in the link context and registers the original primary link as an auxiliary link. Or, upon the expiration of the acknowledgment timeout, the sender writes a backoff trigger flag, stops transmission on the target link, and writes the failure field parameters. After the switchover is committed or rolled back, the sending end continues to collect link quality data on the current main link and writes it into the link context using the switchover completion timestamp as the starting reference timestamp of the collection time window.

[0013] In a preferred embodiment, it includes: a candidate link discovery module, a quality acquisition and normalization module, a handover determination and selection module, a handover execution control module, and signal connections between the modules; The candidate link discovery module is used to maintain multi-standard candidate links in the link context, determine the primary link based on the link reachability verification results, and register the remaining available links as auxiliary links; The quality acquisition normalization module is used to update the link quality acquisition records of the main link and each auxiliary link according to the acquisition time window, generate a normalized set of link quality parameters and link quality scores, and retain historical window data. The handover determination and selection module is used to update the handover determination record based on the link quality score sequence, calculate the main link quality degradation and write it into the handover trigger flag in combination with the threshold set, and determine the target link identifier from the auxiliary links when triggered. The handover execution control module is used to write the media sequence reference number and the transmit buffer occupancy into the link handover execution record, and then read the target link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time and wireless display media data target bit rate. It comprehensively calculates the bearer margin ratio, structural fluctuation and handover execution time budget coefficient, generates parallel transmission window parameters and fragment-level redundant transmission parameters and drives parallel transmission of dual links, interacts with handover confirmation request messages and receive status digests and updates parameters or submits handover or rollback accordingly.

[0014] The technical effects and advantages of the multi-standard compatible wireless display link switching method and system of this invention are as follows: This invention forms a closed loop through context solidification, unified quantification, trend judgment, and adaptive parallel confirmation: First, session capabilities, candidate links, access or routing or verification results are uniformly incorporated into the link context, facilitating rapid retrieval and coverage updates within the same session; then, multi-dimensional quality parameters output from different interfaces are normalized to the same scale according to the standard parameter table and weighted for scoring, achieving cross-standard comparability. Handover determination not only considers instantaneous scores but also introduces the decrease amount and trend slope to reduce accidental triggering due to occasional jitter. During the handover execution phase, the parallel window, redundancy ratio, and confirmation threshold are dynamically adjusted based on the bearer margin ratio, structural volatility, and handover execution time budget coefficient, avoiding congestion amplification when throughput is insufficient and suppressing premature submissions caused by short-term false good results; simultaneously, it provides confirmation timeout fallback and alternative target link mechanisms, significantly improving wireless display continuity and robustness. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of a multi-standard compatible wireless display link switching method and system structure according to the present invention.

[0016] Figure 2 This is a schematic diagram of a multi-standard compatible wireless display link switching method and system flow according to the present invention. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] Example This invention discloses a multi-standard compatible wireless display link switching method, such as... Figure 1 As shown, it includes: Step 1: Discovery of multi-standard candidate links and establishment of link context; First, when initiating a wireless display service, the transmitting end generates a wireless display session identifier, which includes a session number and a session establishment timestamp. The session number is generated by the transmitting end from the output of a local random number generator or by the transmitting end reading a local incrementing counter and incrementing it by one. The session number is used to uniquely locate all record items corresponding to the same wireless display service in the link context. The session establishment timestamp is obtained by the transmitting end reading the local clock. The session establishment timestamp is used to mark the start time of the wireless display service in the link context for time sorting and overwriting updates of record items. The transmitting end creates a link context in local storage and writes the wireless display session identifier into it. The local storage is either an in-memory data structure or a persistent key-value store. The link context is used to store the session media capabilities, presentation media capabilities, candidate link records, link parameter records, and link reachability verification records generated in this step, and performs associated retrieval under the same session number.

[0019] Subsequently, the sending end obtains the session media capabilities and sends them to the display end. The session media capabilities are obtained by the sending end by calling the local video encoder capability query interface and the encapsulator capability query interface. The session media capabilities include video encoding format identifiers, a set of resolution levels corresponding to the video encoding format identifiers, and a set of frame rate levels corresponding to the resolution levels. The sending end writes the session media capabilities into the link context and establishes a binding record for each video encoding format identifier with its available resolution levels and frame rate levels in the link context. The binding record is used as a media constraint condition on the sending end side when checking the service bearability of the candidate link in this step. The display end acquires the presentation media capabilities and returns them to the sending end. The presentation media capabilities are obtained by the display end by calling the local video decoder capability query interface and the renderer capability query interface. The presentation media capabilities include the decodeable video encoding format identifier, the set of renderable resolutions corresponding to the video encoding format identifier, and the set of buffer startup parameters required for rendering. After receiving the presentation media capabilities, the sending end writes them into the link context and establishes a binding record between each decodeable video encoding format identifier and its renderable resolution in the link context. The binding record is used as a presentation constraint condition on the display end side when checking the service bearability of candidate links in this step. The set of buffer startup parameters is used as a parameter field for generating the handshake request payload when establishing the application layer handshake probe in this step, so that the handshake request carries startup buffer conditions acceptable to the display end.

[0020] Then, the transmitting end performs candidate link discovery and forms a candidate link set on the wireless interfaces corresponding to various standard types. The candidate link discovery includes two types of operations: active probing and passive listening. Active probing is used to actively obtain a list of connectable objects on the air interface, while passive listening is used to receive announcement information on the air interface to supplement the missing fields in the active probing and to verify the obtained fields. For WLAN infrastructure networking standards, the transmitting end initiates a scan through the wireless network card driver or operating system network interface and obtains the scan results. The scan results include access point identifier, working channel, and access capability fields. The transmitting end writes the access point identifier into the candidate link record to indicate the access point object of the candidate link, writes the working channel into the candidate link record to indicate the channel that needs to be camped or preferred when performing association in the future, and writes the access capability field into the candidate link record for parsing the authentication method and encryption method when generating link access parameters. For WLAN direct connection, the transmitting end sends a discovery request and receives a discovery response through the direct connection discovery process. The discovery response includes peer identifier and negotiation capability fields. The transmitting end writes the peer identifier into the candidate link record to indicate the display object of the candidate link, and writes the negotiation capability field into the candidate link record for parsing the security and negotiation parameters required for direct connection networking when generating link access parameters. For cellular bearer connection, the transmitting end reads the bearer availability status and measurement reporting information through the baseband or operating system cellular network interface. The bearer availability status is written into the candidate link record to indicate whether the cellular bearer allows the establishment of a data session. The measurement reporting information is written into the candidate link record as a reference input when selecting a probe strategy for link reachability verification in this step. When the measurement reporting information indicates a poor link status, the transmitting end prioritizes application layer handshake probes in this step rather than relying solely on ICMP probes to avoid misjudgments caused by network policy restrictions.

[0021] After forming a candidate link set, the transmitting end generates a link identifier for each candidate link and writes it into the link context. The link identifier is generated by combining the network standard type, local interface identifier, and access point identifier or peer identifier. The local interface identifier is obtained from the network interface name or interface index provided by the operating system. The local interface identifier is written into the link identifier to distinguish different physical access paths in the case of multiple network cards or multiple radio frequencies coexisting. The transmitting end generates link access parameters based on the access capability field or negotiation capability field in the candidate link record and writes them into the link context. The link access parameters include authentication method and encryption method, which are obtained by parsing the access capability field or negotiation capability field. The authentication method and encryption method are used to drive the wireless interface to select the matching authentication and encryption configuration when performing association, networking, or direct connection establishment. The transmitting end reads the local network configuration to obtain the access credential index and writes it into the link access parameters. The access credential index is used to locate the corresponding authentication material when performing association or networking. When performing security negotiation, the transmitting end obtains the session key handle from the security negotiation interface and writes it into the link access parameters. The session key handle is used to reference the encryption context to complete data encryption and decryption when subsequently sending media data or handshake data. The sending end generates link routing parameters and writes them into the link context. These parameters include the local network address, the peer network address, and the peer transmission port. The local network address is obtained from the operating system's IP protocol stack after address allocation and is used for source address selection in this step when constructing connectivity probe packets. The peer network address and peer transmission port are obtained by parsing the service discovery response or the application layer handshake response and are used to construct the destination endpoint of the connectivity probe packets in this step. If the service discovery response contains a logical service name, the sending end writes the logical service name into the link context and a binding record between the logical service name and the peer network address and peer transmission port. The logical service name is used in this step to deduplicate service discovery results and merge multiple discovery results for the same service endpoint into the same candidate link record.

[0022] After the link parameters are written, the sending end performs link reachability verification on each candidate link and writes the verification result to the link context. The sending end first performs link-layer access verification: it calls the radio interface to initiate association, networking, or direct connection establishment operations according to the authentication method, encryption method, and access credential index in the link access parameters, and reads the access status returned by the radio interface. The access status is used to determine whether the link-layer access is successful and is used to write the link-layer access result field in the link context. For candidate links with successful link-layer access, the sending end performs network-layer connectivity verification: it sends an ICMP echo request message to the peer network address in the link routing parameters and waits for an echo reply message, or sends an application-layer handshake request to the peer transmission port in the link routing parameters and waits for a handshake reply. The sending end records the receipt of an echo reply or handshake reply as a successful connection, and records the failure to receive a reply within a timeout as a connection failure, and writes the result to the network-layer connectivity result field in the link context. When sending a probe message, the sending end writes a probe initiation timestamp, and when receiving a response message, it writes a probe response timestamp. The timestamps are obtained by the sending end's local clock. The sending end calculates the round-trip delay based on the difference between the probe response timestamp and the probe initiation timestamp and writes it into the link context. The round-trip delay is used as a comparison value when selecting the primary link from multiple successfully connected candidate links in this step.

[0023] The sending end selects one candidate link from those that have successfully achieved link-layer access and network-layer connectivity in the link context as the primary link and writes the link identifier of the primary link into the link context. When multiple candidate links meet the conditions, the sending end selects the candidate link with the minimum round-trip delay as the primary link and writes it into the primary link selection criteria field. The sending end registers the remaining candidate links that meet the conditions as auxiliary links and writes the link identifier of each auxiliary link into the link context. At the same time, the sending end retains the link-layer access result, network-layer connectivity result, and round-trip delay corresponding to each auxiliary link in the corresponding candidate link record.

[0024] Step 2: Link quality data collection and standardization; The transmitting end establishes link quality acquisition records for the primary link and each auxiliary link within the link context. These records store link quality data acquired for the same candidate link within the same time window, and are associated with the candidate link record using the candidate link's link identifier as an index key. Each link quality acquisition record includes an acquisition time window, a set of original link quality parameters, a set of normalized link quality parameters, and a link quality score. The acquisition time window consists of a start timestamp and an end timestamp, both obtained from the transmitting end's local clock. The set of original link quality parameters stores unnormalized measurement values ​​returned from different wireless interfaces. The set of normalized link quality parameters stores the results after converting the original measurement values ​​to a unified dimension. The link quality score provides a comparable quantitative representation of different candidate links within the same acquisition time window.

[0025] Within the acquisition time window, the transmitting end performs link quality data acquisition for each candidate link. This acquisition includes link layer measurement acquisition, network layer measurement acquisition, and transport layer measurement acquisition. In link layer measurement acquisition, the transmitting end reads the received signal strength indicator (RSI), signal-to-noise ratio (SNR), and retransmission count through the link layer measurement readout interface of the wireless interface. The RSI is the wireless interface's output measurement of the received signal strength; the SNR is the wireless interface's output measurement of the signal-to-noise power ratio; and the retransmission count is the number of retransmissions counted by the wireless interface under the link layer retransmission mechanism. The RSI reflects the received signal strength level of the wireless link, the SNR reflects the quality level of the received signal relative to noise, and the retransmission count reflects the degree of link layer reliability degradation. In network layer measurement and acquisition, the transmitting end performs connectivity probes on the display end within the acquisition time window and calculates the round-trip delay and packet loss rate. The round-trip delay is obtained by the transmitting end recording the probe initiation timestamp and probe response timestamp using its local clock and calculating the difference. The packet loss rate is calculated by the transmitting end counting the number of probe packets sent and the number of probe responses received within the acquisition time window and calculating the difference. Round-trip delay characterizes the latency level of the candidate link, and packet loss rate characterizes the reliability level of the candidate link at the network layer. In transport layer measurement and acquisition, the transmitting end calculates effective throughput and jitter within the acquisition time window. Effective throughput is obtained by the transmitting end counting the number of data bytes successfully sent and acknowledged by the receiving end within the acquisition time window and dividing by the acquisition time window duration. Jitter is obtained by the transmitting end counting the absolute values ​​of the differences between two adjacent round-trip delays within the acquisition time window and averaging them. Effective throughput characterizes the actual usable transmission capacity of the candidate link for carrying wireless display media data, and jitter characterizes the latency fluctuation of the candidate link. The transmitting end writes the received signal strength indication value, signal-to-noise ratio, retransmission count, round-trip delay, packet loss rate, effective throughput and jitter into the original link quality parameter set of the link quality acquisition record, and writes a parameter acquisition timestamp for each original link quality parameter. The parameter acquisition timestamp is obtained by the transmitting end's local clock and is used to time-align different measurement items within the same acquisition time window.

[0026] Because the dimensions of link quality measurements output by wireless interfaces corresponding to different standards are different, the transmitting end performs a standardization process on the original link quality parameter set and generates a normalized link quality parameter set. The transmitting end first determines the upper and lower bounds of the normalized interval for each original link quality parameter. These upper and lower bounds are obtained by the transmitting end from the link quality normalization parameter table read from the link context. This normalized parameter table is preset by the transmitting end and written into local storage. The normalized parameter table stores the upper and lower bounds of the normalized interval corresponding to each original link quality parameter, using the standard type as the index key. For the received signal strength indication (RSS), the lower bound of the normalized interval is the minimum RSS that the wireless interface of this type can report, and the upper bound is the maximum RSS that the wireless interface of this type can report. For the signal-to-noise ratio (SNR), the lower bound of the normalized interval is the minimum SNR that the wireless interface of this type can report, and the upper bound is the maximum SNR that the wireless interface of this type can report. For the retransmission count, the lower bound of the normalized interval is zero, and the upper bound is the maximum allowed retransmission count threshold within the sampling time window, which is obtained by the transmitter from the wireless interface configuration read from the link context. For the round-trip time (RTD), the lower bound of the normalized interval is zero, and the upper bound is the maximum allowed RTD within the sampling time window. The normalization interval is calculated based on the maximum round-trip delay within the time window or the upper limit threshold preset by the transmitter. For packet loss rate, the lower bound of the normalization interval is zero, and the upper bound is one. For effective throughput, the lower bound of the normalization interval is zero, and the upper bound is the target bitrate of the wireless display media data recorded by the transmitter in the session media capability. The target bitrate of the wireless display media data is obtained by the transmitter from reading the output bitrate of the video encoder under the current encoding configuration and writing it into the link context. This is used to normalize the effective throughput to a proportional scale that meets the service bitrate requirements. For jitter, the lower bound of the normalization interval is zero, and the upper bound is the maximum jitter value calculated within the time window or the upper limit threshold preset by the transmitter.

[0027] Furthermore, the transmitting end performs linear normalization on each original link quality parameter and writes the result into the normalized link quality parameter set. For original link quality parameters where larger values ​​indicate a better link, the transmitting end uses forward linear normalization; these parameters include received signal strength indicator, signal-to-noise ratio, and effective throughput. For original link quality parameters where larger values ​​indicate a worse link, the transmitting end uses reverse linear normalization; these parameters include retransmission count, round-trip time, packet loss rate, and jitter. The normalization result of any original link quality parameter x is denoted as n(x), where... This represents the lower bound of the normalized interval corresponding to the original link quality parameter. This represents the upper bound of the normalized interval corresponding to the original link quality parameter, and > When the original link quality parameter is positively linearly normalized, the sender calculates it using the following formula: ; When the original link quality parameter is under inverse linear normalization, the sender calculates it using the following formula: ; Wherein, the value range of n(x) is [0,1], which is used to convert the original link quality parameters of different dimensions into comparable quantities of the same scale; x is obtained by the transmitter through wireless interface measurement or connectivity detection statistics within the acquisition time window; and The target bit rate of the wireless display media data is obtained by the transmitting end from the link quality normalization parameter table, wireless interface configuration, acquisition time window statistics, or the wireless display media data target bit rate in the link context.

[0028] Next, after obtaining the normalized set of link quality parameters, the transmitting end calculates the link quality score and writes it into the link quality acquisition record. The link quality score is denoted as S, and the transmitting end records the normalized result of the received signal strength indication value as... The normalized result of the signal-to-noise ratio is denoted as The normalized result of the retransmission count is denoted as The normalized result of the round-trip delay is denoted as The normalized result of the packet loss rate is denoted as The normalized result of the effective throughput is denoted as The normalized result of the jitter is denoted as The transmitting end reads the link quality weight parameter table from the link context to obtain the weight coefficients corresponding to each normalized parameter. The link quality weight parameter table is preset by the transmitting end and written into local storage. The weight coefficients are denoted as follows: Each weighting coefficient is a non-negative real number, and the sum of the weighting coefficients is one. These weighting coefficients are used to adjust the contribution of different link quality parameters to the overall score. The sending end calculates the link quality score using the following formula: Where S ranges from [0,1], it is used to quantize and compare different candidate links within the same acquisition time window; each All parameters are calculated using the above linear normalization formula and written into the normalized link quality parameter set; each weight coefficient is obtained from the link quality weight parameter table. The sending end writes the link quality score S into the link quality acquisition record and associates the link quality acquisition record with the link identifier of the corresponding candidate link in the link context.

[0029] At the end of the collection time window, the sending end writes the start timestamp of the collection time window, the end timestamp of the collection time window, the original link quality parameter set, the normalized link quality parameter set, and the link quality score to the link context for each candidate link, and retains the link quality collection records of the most recent consecutive collection time windows; the number of the most recent consecutive collection time windows is obtained by the sending end from reading the number of historical link quality windows from the link context, and the number of historical link quality windows is preset by the sending end and written to local storage; Step 3: Switching judgment and target link selection; The transmitting end establishes a handover determination record for the wireless display session in the link context. This record stores the input data, intermediate determination values, determination results, and target link selection results used in a single handover determination. It is associated with the link quality acquisition record in the link context using the session number in the wireless display session identifier as an index key. The handover determination record includes a determination timestamp, a set of acquisition time windows used for determination, a main link link quality score sequence, a sequence of link quality scores for each auxiliary link, a handover trigger flag, a target link identifier, and a handover reason field. The determination timestamp is obtained from the transmitting end's local clock and used for time-sorting consecutive determinations. The set of acquisition time windows used for determination is composed of the timestamp ranges of the most recent consecutive acquisition time windows read by the transmitting end from the link context and is used to limit the historical data range of this determination. The main link link quality score sequence and the sequence of link quality scores for each auxiliary link are obtained by the transmitting end from the link quality acquisition records of the corresponding candidate links and are used to calculate trends and differences. The handover trigger flag indicates whether this determination triggers a link handover. The target link identifier indicates the candidate link selected as the handover target. The handover reason field records the reason type corresponding to the trigger condition.

[0030] At each determination timestamp, the sending end reads the link quality score of the main link within the most recent consecutive collection time windows from the link context and forms a main link link quality score sequence, which is denoted as . , where K represents the number of link quality history windows, which is obtained from the link context; These represent the end timestamps of the most recent consecutive collection time windows, obtained from the end timestamps of the collection time windows in the link quality collection record; Indicates that the main link is in The link quality score is calculated within the acquisition time window ending at the timestamp and obtained from the corresponding link quality acquisition record. The transmitting end reads the link quality score of each auxiliary link from the link context in the same manner for the most recent consecutive acquisition time windows and forms an auxiliary link link quality score sequence, denoted as […]. Where j represents the j-th auxiliary link and It was obtained from the link quality collection records of the auxiliary link.

[0031] The sending end calculates the primary link quality degradation based on the primary link quality score sequence and writes the primary link quality degradation into the handover decision record. The primary link quality degradation is denoted as... The sending end calculates according to the following formula: ; in, The main link quality score for the most recent data collection window. The link quality score for the primary link in the immediately preceding data collection time window; Used to characterize the direction and magnitude of change in the main link quality score between two adjacent data collection time windows, when A negative value indicates a decrease in the primary link quality score. To avoid misjudgments caused by occasional fluctuations within a single data collection window, the transmitting end further calculates the primary link quality trend slope and writes it into the handover determination record. The primary link quality trend slope is denoted as... The sending end calculates according to the following formula: ; in, This is the time span of the most recent consecutive collection time windows, obtained from the difference between the end timestamps of the collection time windows in the link quality collection records; Used to characterize the average rate of change of the main link quality score over the stated time span, when A negative value indicates an overall decrease in the quality score of the main link.

[0032] The sending end reads the handover trigger threshold set from the link context and writes it into the handover determination record. The handover trigger threshold set includes the minimum link quality score threshold for the primary link, the primary link quality degradation threshold, the primary link quality trend slope threshold, and the link quality score difference threshold. These thresholds are parameters preset by the sending end and written into local storage, and are saved in the link context. The minimum link quality score threshold for the primary link is denoted as... It is used to determine whether the main link quality score is lower than the allowable lower limit; the threshold for the main link quality degradation is denoted as... It is used to determine whether the degradation of the main link quality exceeds the allowable range; the main link quality trend slope threshold is denoted as... It is used to determine whether the overall rate of decline in the main link quality score exceeds the allowable rate; the link quality score difference threshold is denoted as... It is also used to determine whether the advantage of the auxiliary link over the main link has reached the switching condition.

[0033] The sending end reads the main link quality score of the most recent collection time window at the judgment timestamp. and the lowest link quality score threshold of the main link. Compare, if satisfied The handover reason field is then written into the handover determination record as "primary link quality score is below the threshold". The sending end records the primary link quality degradation amount at the determination timestamp. With the threshold of main link quality degradation Compare, if satisfied The handover reason field in the handover determination record is then written as "the main link quality degradation exceeds the threshold." The sending end records the main link quality trend slope at the determination timestamp. Slope threshold of main link quality trend Compare, if satisfied The handover reason field is then written into the handover determination record as "the slope of the main link quality trend exceeds the threshold". The sending end performs a logical OR operation on the above three comparison results. If at least one comparison result is true, the handover trigger flag is written as "triggered"; if all three comparison results are false, the handover trigger flag is written as "not triggered".

[0034] When the handover trigger flag is set to trigger, the transmitter performs target link selection for each auxiliary link and writes the target link identifier into the handover determination record. The transmitter then reads the link quality score of each auxiliary link within the most recent acquisition time window at the determination timestamp. And calculate the link quality score difference between the auxiliary link and the primary link. The link quality score difference Calculate using the following formula: ; in, The link quality score for the j-th auxiliary link within the most recent data acquisition window. The link quality score of the main link within the most recent data collection window; This is used to characterize the extent of the advantage of the auxiliary link relative to the main link within the current acquisition time window. The transmitting end will... The threshold for the difference between the link quality score and the threshold Compare, if satisfied The auxiliary link is then recorded as a candidate target link that meets the difference threshold, and its link identifier is written into the candidate target link set field of the handover determination record. If there is no candidate target link that meets the difference threshold, the sending end will rewrite the handover trigger flag to not trigger and rewrite the handover reason field to insufficient advantage of the auxiliary link.

[0035] When candidate target links that meet the difference threshold exist, the transmitter performs multi-criteria sorting on the candidate target link set to determine the target link. The transmitter reads the normalized link quality parameter set for each candidate target link in the most recent acquisition time window from the link context, and reads the round-trip delay record obtained in the link reachability verification for that candidate target link; the transmitter then assigns a link quality score to the candidate target link. The candidate target links are sorted using the first sorting key, the round-trip time (RTD) as the second sorting key, and the network type priority as the third sorting key. The sorting is then performed in descending order of the first sorting key, ascending order of the second sorting key, and descending order of the third sorting key. The network type priority is preset by the sender, written to local storage, and saved in the link context. This priority is used to select the network type that best fits the preset strategy when the link quality score and RTD are similar. The sender determines the first-ranked candidate target link as the target link and writes its link identifier into the target link identifier field of the handover decision record.

[0036] When the handover trigger flag is not triggered, the sending end writes the target link identifier field to the primary link identifier in the handover determination record, and writes the handover reason field to the condition that the handover was not triggered. The sending end writes the handover determination record to the link context and stores the handover determination record in association with the determination timestamp; Step 4: Link switching execution and post-switching stability control; The sending end establishes a link switching execution record in the link context. The link switching execution record is used to save the execution parameters, execution process status, execution result and rollback information of a link switching, and associates it with the link context using the judgment timestamp in the switching judgment record and the target link identifier as index keys. The link switching execution record includes a switching start timestamp, a switching completion timestamp, a switching execution status, a media sequence reference number, a transmit buffer occupancy, a target link pre-connection status, a dual-link parallel transmission status, a receive acknowledgment status, and a backoff trigger flag. The switching start timestamp and switching completion timestamp are obtained from the sender's local clock and are used to characterize the link switching duration. The switching execution status indicates whether the switching process is in a pre-connection, parallel transmission, switching confirmation, old link release, or backoff state. The media sequence reference number is used for deduplication and continuity control of media data during link switching. The transmit buffer occupancy determines the starting position of parallel transmission and the range of data that can be transmitted in parallel. The target link pre-connection status records whether the target link has completed link layer access and network layer connectivity. The dual-link parallel transmission status records whether the primary link and the target link simultaneously transmit the same media data. The receive acknowledgment status records whether the display end has confirmed receiving media data that meets the switching conditions on the target link. The backoff trigger flag records whether a backoff from the target link to the original primary link or to other auxiliary links is triggered.

[0037] The sending end reads the most recent handover determination record from the link context, including the handover trigger flag and the target link identifier. When the handover trigger flag is triggered, the sending end determines the candidate link corresponding to the target link identifier as the target link and reads the target link's access parameters and routing parameters as input for handover execution. When the handover trigger flag is not triggered, the sending end terminates the link handover execution in this step and keeps the primary link unchanged. The sending end writes a handover start timestamp and sets the handover execution status to pre-connection when it begins executing the link handover.

[0038] The transmitting end performs target link pre-connection on the target link, which includes target link layer access and target link network layer connectivity. During target link layer access, the transmitting end calls the radio interface to which the target link belongs and initiates association, networking, or direct connection establishment operations based on the authentication method, encryption method, and access credential index in the target link access parameters, and reads the access status returned by the radio interface. When the access status is successful, the transmitting end writes the link layer access result in the target link pre-connection status as successful; when the access status is unsuccessful, the transmitting end writes the link layer access result in the target link pre-connection status as unsuccessful and writes the handover execution status as fallback preparation. During target link network layer connectivity, the sending end sends a connectivity probe message to the display end based on the peer network address and peer transmission port in the target link routing parameters and waits for a response message. The connectivity probe message is either an Internet Control Message Protocol echo request message or an application layer handshake request message. When a response message is received, the sending end writes the network layer connectivity result in the target link pre-connection state as successful. If no response message is received within a timeout period, the sending end writes the network layer connectivity result in the target link pre-connection state as failed and writes the handover execution status as fallback ready. The sending end writes the target link pre-connection state into the link handover execution record.

[0039] When both the link layer access result and the network layer connectivity result are successful in the target link pre-connection state, the sending end reads the current main link's transmit buffer occupancy and writes it into the link switching execution record. The transmit buffer occupancy is the number of bytes of media data to be transmitted in the transmit buffer, obtained by the sending end reading the difference between the write pointer and the read pointer of the transmit buffer. The transmit buffer occupancy is used to determine the range of media data to be transmitted in parallel and the media data position corresponding to the starting point of parallel transmission. The sending end reads the media sequence reference number in the current media stream and writes it into the link switching execution record. The media sequence reference number is the starting number or current number of the continuous number assigned by the sending end after media data fragmentation. It is generated and maintained by the sending end during media fragmentation and encapsulation. The media sequence reference number is used to consistently identify media data fragments during link switching to support the display end in performing deduplication and continuous decoding.

[0040] It should be noted that during the time slice after the handover is triggered and the link handover execution begins, the transmitting end reads a continuously decreasing trend in the link quality score of the main link from the most recent consecutive acquisition time windows. Simultaneously, although a higher link quality score can be read on the target link side, the normalized link quality parameters of the target link within the same time slice, including effective throughput, packet loss rate, and jitter, exhibit inconsistent fluctuations between adjacent acquisition time windows. This means that the overall score advantage and the bearer stability do not appear synchronously. Furthermore, the target bitrate of the wireless display media data used by the transmitting end is statistically obtained from the video encoder's output bitrate and remains at the target level under the current encoding configuration. Meanwhile, the original effective throughput of the target link is statistically obtained from the number of confirmed received bytes and the window duration within each acquisition time window, and fluctuates between these windows. This causes the margin state between the two to drift across different time windows. Furthermore, the sender reads that the send buffer occupancy is high, and the media sequence reference number advances rapidly during media fragmentation and encapsulation. This causes the coverage of the media data fragment sequence to be sent to expand and compress over time, compressing the tolerance time available for handover confirmation and submission. Consequently, the handover execution time budget coefficient for the waiting, retry, and parallel sending ranges during the handover execution phase shows a shrinking trend.

[0041] Therefore, in this embodiment, after completing the pre-connection of the target link and writing the transmit buffer occupancy and media sequence reference number, the transmitting end reads the link quality score sequence and normalized link quality parameter set of the target link in the most recent consecutive collection time windows from the link context, and reads the original effective throughput, packet loss rate, jitter, and round-trip delay of the target link in the most recent collection time window; wherein the link quality score sequence and normalized link quality parameter set are obtained by reading the link quality collection record corresponding to the target link, and are used to characterize the short-term stability changes of the target link; the original effective throughput is obtained by dividing the number of data bytes successfully acknowledged and received in the collection time window by the collection time window duration, and is used to characterize the actual available carrying capacity of the target link; the packet loss rate is obtained by counting the number of probe message transmissions and probe response receptions, and is used to characterize the reliability level of the target link; the jitter is obtained by counting the absolute value of the difference between two adjacent round-trip delays, and is used to characterize the delay fluctuation level of the target link; the round-trip delay is obtained by the difference between the probe initiation timestamp and the probe response timestamp, and is used to characterize the delay scale of the target link interaction closed loop. The transmitting end simultaneously reads the target bitrate of the wireless display media data from the link context. This target bitrate is obtained by the transmitting end from the video encoder output bitrate statistics under the current encoding configuration, and is used to characterize the current media output's demand level on link throughput. The transmitting end writes the aforementioned link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time, and target bitrate of the wireless display media data into the link handover execution record. This writing is used to solidify the input conditions for this handover execution. The transmitter calculates the carrying margin ratio based on the original effective throughput and the target bit rate of the wireless display media data. The load margin ratio Calculate using the following formula: ; in This represents the original effective throughput of the target link, obtained from link quality collection records. Indicates the target bit rate of the wireless display media data and is obtained by reading the link context; bearer margin ratio This is used to determine the allowable redundancy transmission intensity and the upper limit of the allowable transmission rhythm for the target link during the handover execution phase, so that redundant transmission will not amplify queuing delay and packet loss when throughput margin is insufficient. The transmitting end calculates the structural volatility based on the normalized link quality parameter set. The structural volatility The results are obtained by statistically analyzing the changes in adjacent windows of the normalized results of effective throughput, packet loss rate, and jitter within the target link over the most recent consecutive collection time windows. Each normalized result is obtained from the set of normalized link quality parameters in the link quality collection records, including structural volatility. This is used to determine the conservatism of the acknowledgment threshold and the fault tolerance configuration of the acknowledgment loop during the handover execution phase, enabling the acknowledgment criteria to avoid short-term false good intervals. The sending end calculates the handover execution time budget coefficient based on the transmit buffer occupancy and the media sequence reference number advancement speed. The send buffer occupancy is obtained by the sender reading the difference between the write pointer and read pointer of the send buffer, and is used to characterize the backlog of media data fragments to be sent; the media sequence reference number advancement speed is obtained by the sender reading the media sequence reference number in two adjacent time slices and calculating the difference, and is used to characterize the growth rate of the media sequence number; the switching execution time budget coefficient. This is used to limit the allowed confirmation waiting time and the allowed parallel transmission window length during the handover execution phase, so that the handover execution will not cause the parallel coverage to get out of control due to excessive waiting time.

[0042] The sending end calculates... , and Then, parallel transmission window parameters are generated, and the switching execution state is written as dual-link parallel transmission. The parallel transmission window parameters include a parallel transmission start media sequence number and a parallel transmission end media sequence number. The parallel transmission start media sequence number is taken from the media sequence reference number and is used to specify the starting point of the parallel transmission coverage. The parallel transmission end media sequence number is determined by the transmittable fragment range corresponding to the transmission buffer occupancy and based on... Adjustment, used to specify the endpoint of parallel transmission coverage: when When the allowed acknowledgment wait time is short, the sender will send the termination media sequence number in parallel to shrink the coverage area and compress the acknowledgment loop time; when When the allowed acknowledgment waiting time is long and the send buffer usage is low, the sender will send the termination media sequence number in parallel to extend the coverage and improve the confidence of the acknowledgment statistics.

[0043] The sending end generates fragment-level redundancy transmission parameters and writes them into the link switching execution record. These parameters include the target link redundancy ratio, the target link transmission rhythm, and fragment priority rules. The target link redundancy ratio indicates the probability or frequency of repeated transmission of media data fragments with the same media sequence number on the target link. The target link transmission rhythm indicates the transmission interval or token rate limit on the target link. The fragment priority rules indicate which media data fragments are preferentially repeated within the parallel transmission window. The fragment priority rules are generated by the fragment type flag obtained by the sending end during media fragmentation and encapsulation. The fragment type flag indicates whether the media data fragment belongs to a keyframe-related fragment or a reference frame-related fragment. The fragment type flag is obtained by mapping the frame type information output by the video encoder to the fragment header field generated by the encapsulator. The fragment priority rules are used to prioritize ensuring that fragments with a greater impact on picture continuity are reliably received by the target link when the target link structure fluctuates. The sending end bases its decisions on... and Set the target link redundancy ratio and target link transmission rhythm, and write them into the link switching execution record: when Characterized by high bearing capacity and When the structural volatility is high, the transmitting end increases the target link redundancy ratio and the retransmission priority of key frame-related fragments to compensate for the loss of key fragments caused by intermittent packet loss and jitter; when Characterizing the carrying capacity margin ratio is close to the critical and When the characterization structure exhibits high volatility, the sending end increases the priority of retransmitting keyframe-related fragments and reduces the transmission rhythm of the target link to prevent further increases in packet loss rate due to overload during throughput decline intervals; when Characterized by high bearing capacity and When the structural volatility is low, the transmitter reduces the redundancy ratio of the target link and keeps the transmission rhythm of the target link close to that of the main link in order to reduce the overhead of repeated transmissions and shorten the acknowledgment loop.

[0044] During the dual-link parallel transmission phase, the transmitting end generates a media sequence number for each media data fragment within the parallel transmission window and transmits it on both the main link and the target link. The media sequence number is obtained by adding the fragment number to the media sequence base number, enabling the display end to deduplicate duplicate fragments and maintain the continuity of the decoding input sequence. When transmitting media data fragments on the target link, the transmitting end performs repeated transmission based on fragment-level redundancy transmission parameters: the transmitting end prioritizes repeated transmission of media data fragments that meet the fragment priority rules, and determines the number of repeated transmissions for the same media sequence number according to the target link redundancy ratio; the number of repeated transmissions is used to increase the fragment arrival probability and reduce the probability of missing critical fragments when the target link packet loss rate and jitter intermittently worsen. The display end receives media data fragments and parses the media sequence numbers on both the main link and the target link, performs deduplication on duplicate fragments with the same media sequence number, and sends the deduplicated media data fragments into decoding and rendering in the order of their media sequence numbers; the deduplication operation is used to avoid redundancy and buffer expansion caused by duplicate fragments, and sequential transmission is used to maintain the continuity of the image presentation.

[0045] During the dual-link parallel transmission phase, the transmitting end sends a handover acknowledgment request message to the display end via the target link. This message carries the target link identifier, the parallel transmission start media sequence number, the parallel transmission end media sequence number, an acknowledgment threshold parameter set, and an acknowledgment timeout parameter. The acknowledgment threshold parameter set includes a continuous reception threshold and a consistency threshold. The continuous reception threshold limits the length of the continuous reception interval formed by the display end on the target link, while the consistency threshold limits the maximum number of missing fragments and out-of-order fragments allowed by the display end within the parallel transmission window. The continuous reception threshold and the consistency threshold are determined by the transmitting end based on… , and Setting: When When the threshold is high, the transmitter increases the continuous reception threshold and sets a more conservative consistency threshold to avoid premature acknowledgment during short-term false-good intervals on the target link; when When the transmit buffer occupancy is low and high, the transmitter lowers the continuous receive threshold and tightens the consistency threshold to compress the acknowledgment closure time and limit long-term parallel coverage; when When approaching the critical point, the transmitter raises the continuous reception threshold and reduces the transmission rate of the target link to reduce overload and increase the probability of continuous reception during the throughput drift range. The acknowledgment timeout parameter is determined by the transmitter based on... The mapping is used to limit the maximum allowed time for the display end to continuously receive and return acknowledgments, preventing the acknowledgment loop from being extended indefinitely. The sending end writes the handover acknowledgment request message sending action and message content into the link handover execution record, which is used to reproduce the basis for the values ​​of the acknowledgment threshold and acknowledgment time limit during execution backtracking.

[0046] After receiving media data fragments on the target link, the display terminal performs continuous statistics on the media sequence numbers on the target link based on the parallel transmission start media sequence number and parallel transmission end media sequence number in the handover confirmation request message, and forms a reception status summary. The reception status summary includes the maximum continuously received media sequence number, the missing media sequence number count, the out-of-order media sequence number count, and the display terminal's reception buffer status flag. The maximum continuously received media sequence number represents the progress position of the continuous reception interval; the missing media sequence number count represents the degree of missing media sequence numbers within the parallel transmission window; the out-of-order media sequence number count represents the degree of out-of-order; and the display terminal's reception buffer status flag represents whether the display terminal's reception buffer can maintain continuous decoding input. When the continuous reception threshold is met and both the missing media sequence number count and the out-of-order media sequence number count meet the consistency threshold, the display terminal returns a handover confirmation response message to the sending terminal, carrying the target link identifier and the reception status summary. This allows the sending terminal to bind the confirmation to the target link and read the continuous reception status at the time of confirmation. When the display terminal fails to meet the continuous reception threshold or the consistency threshold and the acknowledgment time limit has not expired, it returns a reception status acknowledgment message to the sending terminal, carrying the target link identifier and reception status summary. This message is used to provide the sending terminal with acknowledgment progress and gap information, enabling the sending terminal to update the redundancy ratio and threshold parameters accordingly.

[0047] To reduce reliance on reliable returns from a single control message, the display end embeds a received status summary into the payload field of the application layer handshake response or periodic link layer hold message to form an embedded received status receipt. The application layer handshake response is the display end's reply to the sender's handshake request, and the link layer hold message is the hold message sent by the display end to maintain connection activity; both are generated from the display end's existing communication processes. The received status summary embedding action ensures that the received status can still be transmitted to the sender even when the return direction is unstable or the dedicated acknowledgment message is lost. After receiving the handover acknowledgment response, received status receipt message, or embedded received status receipt, the sender writes the received acknowledgment status to the link handover execution record and also writes the received status summary to the link handover execution record. The received acknowledgment status indicates whether the acknowledgment condition has been met, and the received status summary indicates missing or out-of-order distribution when the acknowledgment condition has not been met.

[0048] When the sending end receives a handover confirmation response message within the confirmation time limit, it writes the handover execution status as "confirmed handover" and submits the primary link handover. The primary link handover submission process is as follows: the sending end rewrites the primary link identifier in the link context to the target link identifier, and registers the original primary link identifier as the secondary link identifier; the sending end writes the primary link flag of the candidate link record corresponding to the target link as true in the link context, and writes the primary link flag of the candidate link record corresponding to the original primary link as false. When the sending end does not receive a handover acknowledgment message within the acknowledgment time limit but continues to receive a receive status digest, the sending end updates the fragment-level redundancy transmission parameters and acknowledgment threshold parameter set based on the maximum continuously received media sequence number, missing media sequence number count, and out-of-order media sequence number count in the receive status digest, and writes the update result into the link handover execution record. When updating the target link redundancy ratio, the sending end uses the increase in the missing media sequence number count and the increase in the out-of-order media sequence number count as trigger conditions to increase the redundancy ratio and increase the priority of repeated transmission of key frame-related fragments, in order to improve the arrival probability of key fragments; when updating the target link transmission rhythm, the sending end uses the stagnation of the maximum continuously received media sequence number as a trigger condition to reduce the target link transmission rhythm, in order to reduce queuing delay and reduce out-of-order transmission; when updating the parallel transmission termination media sequence number, the sending end uses the decrease in the remaining acknowledgment time limit and the increase in the transmission buffer occupancy as trigger conditions to shrink the parallel coverage area forward, in order to shorten the acknowledgment loop and limit the expansion of the coverage area. After completing the above update, the sending end sends a handover confirmation request message to the display end again through the target link, carrying the updated confirmation threshold parameter set, and continues to perform parallel transmission on both links until it receives a handover confirmation response message or the confirmation time limit expires.

[0049] If no handover confirmation response message is received by the expiration of the confirmation period, the sending end writes the result into the link handover execution record and triggers the rollback preparation. The sending end stops sending media data fragments on the target link and continues to send media data fragments on the original main link. At the same time, the target link redundancy ratio, target link transmission rhythm, fragmentation priority rules, confirmation threshold parameter set, confirmation time limit parameter and parallel transmission window parameter are written into the link handover execution record as failure field parameters.

[0050] After the primary link handover is submitted, the transmitter sets the handover execution status to "Release Old Link" and executes the old link release. Old link release means the transmitter stops transmitting media data fragments on the original primary link and calls the radio interface to which the original primary link belongs to disconnect, exit the network, or disconnect the direct connection. If the original primary link is registered as an auxiliary link and needs to maintain a pre-connection, the transmitter does not perform a disconnection operation but only stops media data transmission and retains the link layer access state. After completing the old link release or stopping media transmission, the transmitter writes a handover completion timestamp, sets the handover execution status to "Completed," and writes the link handover execution record to the link context.

[0051] When the target link pre-connection status fails or a handover confirmation response message is not received within the predetermined confirmation time during dual-link parallel transmission, the sending end triggers a fallback and writes the fallback trigger flag into the link handover execution record. The predetermined confirmation time is obtained by the sending end from the preset parameters read from the link context. After the fallback is triggered, the sending end writes the handover execution status as fallback and executes the fallback. Fallback execution means that the sending end stops transmitting media data fragments on the target link while maintaining the original primary link to continue transmitting media data fragments. At the same time, it calls the radio interface to which the target link belongs to release the link layer access of the target link or releases the security negotiation context of the target link. If there are other auxiliary links in the link context and their link reachability verification record is successful, the sending end writes the link identifier of the other auxiliary link into the link identifier field of the target link and re-executes the target link pre-connection and dual-link parallel transmission. The sending end writes the failure reason during the fallback execution process into the fallback reason field of the link handover execution record. The fallback reason field includes three values: target link link layer access failure, target link network layer connectivity failure, and handover confirmation timeout. The sending end then writes the link handover execution record into the link context.

[0052] Finally, after the link switchover is completed or the rollback is finished, the sending end continues to collect link quality data on the current main link and updates the link quality collection record. The switchover completion timestamp in the link switchover execution record is used as the starting reference timestamp of the subsequent collection time window to separate the link quality changes before and after the switchover into different collection time windows.

[0053] This invention also proposes a multi-standard compatible wireless display link switching system, such as... Figure 2 As shown, it includes: a candidate link discovery module, a quality acquisition and normalization module, a switching determination and selection module, a switching execution control module, and signal connections between the modules; The candidate link discovery module is used to maintain multi-standard candidate links in the link context, determine the primary link based on the link reachability verification results, and register the remaining available links as auxiliary links; The quality acquisition normalization module is used to update the link quality acquisition records of the main link and each auxiliary link according to the acquisition time window, generate a normalized set of link quality parameters and link quality scores, and retain historical window data. The handover determination and selection module is used to update the handover determination record based on the link quality score sequence, calculate the main link quality degradation and write it into the handover trigger flag in combination with the threshold set, and determine the target link identifier from the auxiliary links when triggered. The handover execution control module is used to write the media sequence reference number and the transmit buffer occupancy into the link handover execution record, and then read the target link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time and wireless display media data target bit rate. It comprehensively calculates the bearer margin ratio, structural fluctuation and handover execution time budget coefficient, generates parallel transmission window parameters and fragment-level redundant transmission parameters and drives parallel transmission of dual links, interacts with handover confirmation request messages and receive status digests and updates parameters or submits handover or rollback accordingly.

[0054] The above formulas are all dimensionless calculations. The formulas are derived from software simulations based on a large amount of collected data to obtain the most recent real-world results. The preset parameters in the formulas are set by those skilled in the art according to the actual situation.

[0055] The above embodiments can be implemented, in whole or in part, by software, hardware, firmware, or any other combination thereof. When implemented using software, the above embodiments can be implemented, in whole or in part, in the form of a computer program product.

[0056] Those skilled in the art will recognize that the modules and algorithm steps of the various examples described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are implemented in hardware or software depends on the specific application and inventive constraints of the technical solution. Those skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of this application.

[0057] In addition, the functional modules in the various embodiments of this application can be integrated into one processing module, or each module can exist physically separately, or two or more modules can be integrated into one module.

[0058] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

[0059] In conclusion, the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A multi-standard compatible wireless display link switching method, characterized in that, include: Maintain multi-standard candidate links in the link context, determine the primary link based on the link reachability verification results, and register the remaining available links as auxiliary links; Update the link quality collection records for the main link and each auxiliary link according to the collection time window, generate a normalized link quality parameter set and link quality score, and retain historical window data; The handover determination record is updated based on the link quality score sequence. The quality degradation of the primary link is calculated and written into the handover trigger flag in combination with the threshold set. When triggered, the target link identifier is determined from the auxiliary links. After writing the media sequence reference number and the transmit buffer occupancy into the link handover execution record, the target link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time, and target bit rate of wireless display media data are read. The bearer margin ratio, structural fluctuation, and handover execution time budget coefficient are calculated comprehensively. Parallel transmission window parameters and fragment-level redundant transmission parameters are generated and dual-link parallel transmission is driven. The handover confirmation request message and receive status summary are exchanged and the parameters are updated accordingly or the handover and rollback are submitted.

2. The multi-standard compatible wireless display link switching method according to claim 1, characterized in that: When initiating a wireless display service, the transmitting end generates a wireless display session identifier containing a session number and a session establishment timestamp, and creates a link context in local storage, writing the session identifier to associate and save candidate link records and link parameter records. Based on the candidate link discovery results, the transmitting end generates a link identifier for each candidate link, which is a combination of the standard type, local interface identifier, and access point identifier or peer identifier, and writes it into the link context. At the same time, it parses the access capability field or negotiation capability field to generate link access parameters containing authentication method and encryption method, and writes them into the link context. Furthermore, it reads the access credential index and obtains the session key handle, and writes them into the link access parameters.

3. The multi-standard compatible wireless display link switching method according to claim 2, characterized in that: The sending end generates link routing parameters containing the local network address, the peer network address, and the peer transmission port and writes them into the link context. Then, it initiates association, networking, or direct connection establishment on each candidate link according to the link access parameters and records the access status. Next, it sends probe messages to the peer network address and records the probe initiation timestamp and probe response timestamp. Based on the difference of the timestamps, it calculates the round-trip delay and writes it into the link context. Finally, based on the round-trip delay, it selects the primary link from multiple available candidate links and registers the remaining links as auxiliary links and writes them into the link context.

4. The multi-standard compatible wireless display link switching method according to claim 3, characterized in that: The transmitting end establishes link quality acquisition records for the main link and each auxiliary link in the link context, with the link identifier as the index key. Within each acquisition time window, it acquires the received signal strength indicator value, signal-to-noise ratio, retransmission count, round-trip delay, packet loss rate, effective throughput, and jitter. The measured values ​​and the corresponding parameter acquisition timestamps are written into the original link quality parameter set. The transmitting end reads the link quality normalization parameter table indexed by the standard type, the wireless interface configuration, and the target bitrate of the wireless display media data in the link context from the link context. It determines the upper and lower bounds of the normalization interval for each original parameter, and uses forward linear normalization for the forward parameters and reverse linear normalization for the reverse parameters to generate a normalized link quality parameter set. The normalization upper bound of the effective throughput is taken as the target bitrate of the wireless display media data to map the throughput to the service demand scale. The sending end further reads the link quality weight parameter table from the link context, calculates the link quality score by weighting and summing each normalized result according to the weight coefficient, and writes it into the link quality acquisition record. Finally, at the end of the acquisition time window, the start and end timestamps of the time window, the original link quality parameter set, the normalized link quality parameter set and the link quality score are written into the link context, and the link quality acquisition record of the acquisition time window is retained according to the preset number of historical windows.

5. A multi-standard compatible wireless display link switching method according to claim 4, characterized in that: The sending end establishes a handover determination record in the link context with the session number as the index key. At each determination timestamp, it reads the timestamp range of the most recent consecutive collection time windows from the link quality collection record as the collection time window set used for determination. At the same time, it reads the link quality scores of the main link and each auxiliary link within the window range to form a score sequence. Based on the main link score sequence, the sending end calculates the link quality degradation amount of adjacent windows and the link quality trend slope across multiple windows. It reads the minimum link quality score threshold of the main link, the main link link quality degradation amount threshold, the main link link quality trend slope threshold and the link quality score difference threshold from the link context and writes them into the handover determination record. Then, it compares the main link score of the most recent collection time window with the minimum main link score threshold, compares the degradation amount with the degradation amount threshold, and compares the trend slope with the trend slope threshold. The comparison results are written into the handover trigger flag and handover reason fields. When the handover trigger flag is triggered, the sending end reads the link quality score of each auxiliary link in the most recent acquisition time window and calculates the score difference relative to the main link. The score difference is compared with the score difference threshold, and a set of candidate target links and their link identifiers are generated and written into the handover decision record. If there are candidate target links, the normalized link quality parameter set and the round-trip delay record of the link reachability verification stage in the most recent acquisition time window of the candidate target links are further read. After sorting according to multiple criteria such as link quality score, round-trip delay and system type priority, the link identifier of the first ranked candidate link is written into the target link link identifier field, and the handover decision record is associated with the decision timestamp and written into the link context.

6. The multi-standard compatible wireless display link switching method according to claim 5, characterized in that: The sending end establishes a link handover execution record in the link context with the determination timestamp and the target link identifier as the index key, and writes the handover start timestamp, handover execution status, media sequence reference number, transmission buffer occupancy, target link pre-connection status, dual-link parallel transmission status, reception acknowledgment status and backoff trigger flag. The sending end reads the target link identifier from the most recent handover determination record, and reads the target link's link access parameters and link routing parameters as handover execution input. On the target link, it initiates association, networking, or direct connection establishment according to the authentication method, encryption method, and access credential index, and sends connectivity probe messages based on the peer network address and peer transmission port. The link layer access result and network layer connectivity result are written into the target link pre-connection state and into the link handover execution record. Subsequently, the difference between the write pointer and read pointer of the transmit buffer is read to obtain the transmit buffer occupancy and written into the link switching execution record. The media sequence reference number maintained during media fragmentation and encapsulation is read and written into the link switching execution record. After writing the transmit buffer occupancy and the media sequence reference number, the transmitting end reads the link quality score sequence and normalized link quality parameter set of the target link from the link quality acquisition record for the most recent consecutive acquisition time windows. It also reads the original effective throughput, packet loss rate, jitter, and round-trip delay within the most recent acquisition time window. At the same time, it reads the target bitrate of the wireless display media data obtained by statistical analysis of the bitrate output by the video encoder from the link context. The transmit end then writes the link quality score sequence, normalized link quality parameter set, original effective throughput, packet loss rate, jitter, round-trip delay, and target bitrate of the wireless display media data into the link switching execution record.

7. A multi-standard compatible wireless display link switching method according to claim 6, characterized in that: The transmitting end calculates the carrying margin ratio based on the original effective throughput of the target link and the target bit rate of the wireless display media data. It calculates the structural volatility based on the statistical changes in adjacent windows of the normalized results of effective throughput, packet loss rate, and jitter in the normalized link quality parameter set. It calculates the handover execution time budget coefficient based on the difference between the transmission buffer occupancy and the media sequence reference number in adjacent time slices. Based on this, it generates parallel transmission window parameters and fragment-level redundancy transmission parameters, writes them into the link handover execution record, and writes them into the dual-link parallel transmission status. The parallel transmission window parameters include the parallel transmission start media sequence number determined by the media sequence reference number and the parallel transmission end media sequence number obtained by adjusting the transmittable fragment range corresponding to the transmission buffer occupancy and the handover execution time budget coefficient. The fragment-level redundancy transmission parameters include the target link redundancy ratio, the target link transmission rhythm, and the fragment priority rules generated by the fragment type flag.

8. A multi-standard compatible wireless display link switching method according to claim 7, characterized in that: Within the parallel transmission window, the sending end generates a media sequence number for each media data fragment from the media sequence base number and the fragment sequence number, and sends them through the main link and the target link respectively. On the target link side, the same media sequence number is repeatedly transmitted according to the fragmentation priority rules and the target link redundancy ratio. At the same time, a switching acknowledgment request message carrying the target link identifier, the parallel transmission start media sequence number, the parallel transmission end media sequence number, the continuous reception threshold, the consistency threshold, and the acknowledgment time limit parameters is sent through the target link. The display end receives media data fragments from the main link and the target link and parses the media sequence numbers. It performs deduplication on duplicate fragments with the same media sequence number and sends them to decoding and rendering in sequence. Based on the parallel transmission start media sequence number and the parallel transmission end media sequence number, it generates a receive status digest on the target link, including the maximum consecutive received media sequence number, missing media sequence number count, out-of-order media sequence number count, and receive buffer status flag. This digest is sent back to the sending end via a switch confirmation reply message, a receive status receipt message, or by embedding the receive status digest into the application layer handshake reply or link layer hold message payload field. The sending end updates the fragment-level redundant transmission parameters, the confirmation threshold parameter set, and the parallel transmission end media sequence number based on the receive status digest and writes them into the link switch execution record. Alternatively, upon receiving a switch confirmation reply message, it rewrites the main link identifier and candidate link main link flag in the link context and registers the original main link as an auxiliary link. Or, when the confirmation timeout expires, it writes a backoff trigger flag, stops the target link transmission, and writes the failure field parameters. After the switchover is committed or rolled back, the sending end continues to collect link quality data on the current main link and writes it into the link context using the switchover completion timestamp as the starting reference timestamp of the collection time window.

9. A multi-standard compatible wireless display link switching system, used to implement the multi-standard compatible wireless display link switching method according to any one of claims 1-8, characterized in that, include: Candidate link discovery module, quality acquisition and normalization module, switching judgment and selection module, switching execution control module, and signal connections between modules; The candidate link discovery module is used to maintain multi-standard candidate links in the link context, determine the primary link based on the link reachability verification results, and register the remaining available links as auxiliary links; The quality acquisition normalization module is used to update the link quality acquisition records of the main link and each auxiliary link according to the acquisition time window, generate a normalized set of link quality parameters and link quality scores, and retain historical window data. The handover determination and selection module is used to update the handover determination record based on the link quality score sequence, calculate the main link quality degradation and write it into the handover trigger flag in combination with the threshold set, and determine the target link identifier from the auxiliary links when triggered. The handover execution control module is used to write the media sequence reference number and the transmit buffer occupancy into the link handover execution record, and then read the target link quality score sequence, normalized link quality parameter set, raw effective throughput, packet loss rate, jitter, round-trip time and wireless display media data target bit rate. It comprehensively calculates the bearer margin ratio, structural fluctuation and handover execution time budget coefficient, generates parallel transmission window parameters and fragment-level redundant transmission parameters and drives parallel transmission of dual links, interacts with handover confirmation request messages and receive status digests and updates parameters or submits handover or rollback accordingly.

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