An optimal selective relay sensing access method

Abstract

The application discloses an optimal selective relay sensing access method, communication nodes can exist as relay nodes at the same time, role diversity is increased, time, space and equipment resources are fully utilized; an optimal detection relay strategy is adopted to select a best relay detection set, time cost of detection relay is associated with detection benefit, and unnecessary detection cost is avoided; all decision thresholds and global parameters can be calculated offline under the condition of statistical information based on a wireless network channel, an iterative algorithm with linear complexity is proposed, and the optimal solution can be quickly converged, the time for calculation can be effectively reduced for a large-scale distributed network, and errors are not prone to occur; a concept of alliance game is introduced, a benefit function of a communication pair and an alliance ordering operator are constructed, and cooperation motivation among the communication nodes is considered, so that the cooperation relationship is stable and reasonable.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of network protocol and physical layer security technology in wireless communication technology, in particular to an optimal selective relay-aware access method based on multi-user coalition game. BACKGROUND

[0002] Opportunistic access in distributed network is mainly divided into direct connection and cooperation, the direct connection network only considers access through direct connection channel, the core idea of which is that after multi-user distributed mode competes for the channel, the user who wins the channel will compare the channel condition with a fixed threshold, if the channel condition is higher than the threshold, the user will access the channel to carry out adaptive rate transmission, otherwise the user will give up the channel opportunity, and all users will re- compete for the channel. Compared with the direct connection network, the cooperative network structure is more complex, and more factors need to be considered for channel access optimization, so the research difficulty is greater, and the existing research work is still in the initial stage.

[0003] Based on the research results of direct connection network, the distributed channel access method of distributed cooperative network is researched and explored, mainly aiming at the optimal statistical throughput performance of the network. The channel sensing and access modeling and statistical optimization method under the working mode of controlled and autonomous relay point are researched. Among them, based on the stop optimization theory, the mathematical modeling is carried out, and the statistical decision method of relay channel full sensing and access under the mode of controlled relay resource is proposed. In view of the problem that the sensing overhead of controlled mode relay channel increases linearly with the number of relay points, the full distributed channel sensing and access method under the autonomous mode of relay resource is researched, the mathematical modeling method based on double-stage stop optimization method is proposed, and the full distributed statistical decision optimization method of user channel competition sensing and front-hop broadcast-multi-relay point distributed sensing and back-hop forwarding is established, which has the statistical optimality of network throughput.

[0004] It can be seen that the existing distributed cooperative network opportunistic channel access method has the following defects:

[0005] 1. It is divided into relay nodes and communication nodes, and the user nodes communicate with the aid of relay nodes, the relay nodes can only exist as auxiliary relays, the node role is single, and the network resources are not fully utilized;

[0006] 2. The optimization design is based on the willingness of all network nodes to cooperate, and the individual benefit performance of the communication pair is not considered, only the average throughput of the whole network is optimized, such cooperation is not reasonable and does not conform to the actual application scenario.

[0007] 3. The relay selection strategy is basically random single relay selection or full relay detection, which fails to find the balance between detection overhead and detection benefit, and wastes detection time or fails to find the optimal relay link. SUMMARY

[0008] In view of the above problems, the present invention provides an optimal selective relay-aware access method for overcoming the above problems or at least partially solving the above problems.

[0009] The present invention provides the following solutions:

[0010] An optimal selective relay sensing access method, comprising:

[0011] Determining a set of communication pairs, a current alliance structure, and a number of transfers for a given social trust network; the social trust network includes a heterogeneous wireless collaborative network consisting of multiple source and sink pairs with a three-level trust relationship; sources and sinks within the same alliance structure serve as relays for each other;

[0012] All communication nodes in the communication pair set broadcast short packets containing location information in sequence according to their respective node IDs, so that after a round of broadcasting, each communication node obtains the location information of all other communication nodes;

[0013] Obtaining statistical information of channels between the communication nodes based on the location information; calculating the benefit of each communication pair under the current alliance structure using a benefit function according to the statistical information; and using the benefit to evaluate whether each communication pair is motivated to break the current alliance structure to form a new alliance structure; and outputting a stable alliance structure if it is determined that no user has the motivation to break the current alliance structure.

[0014] Based on the stable alliance structure, distributed channel competition and opportunistic channel access are performed according to an opportunistic channel access method based on a fixed alliance structure. The opportunistic channel access method based on a fixed alliance structure includes, under the stable alliance structure, multiple information sources competing for channels by sending and receiving probe data packets in a distributed manner, measuring channel states in real time, and dynamically selecting the best relay channels within all their alliances for opportunistic access.

[0015] Preferably, the method for outputting the stable alliance structure includes:

[0016] Step 11: Current Alliance Structure , calculate the communication pair through the benefit function Stay in the current alliance The benefits within the alliance and the benefits of joining other alliances are evaluated to see whether there is a motivation to transfer. If so, proceed to step 12.

[0017] Step 12: OK , the alliance Join the communication pair Federation history collection In the communication Leave its current alliance , otherwise, no need to update the coalition history set , the communication pair directly leaves the coalition ; transfer factor , enter step 13;

[0018] Step 13: the communication pair joins a new coalition with a transfer mechanism, if there are more than one coalition satisfying the transfer requirement, then select the coalition with the maximum benefit to join; enter step 14;

[0019] Step 14: the communication pair updates the current coalition structure , and informs other communication pairs of the new coalition structure in a broadcast manner; after the end of a single iteration period, enter step 15;

[0020] Step 15: the iteration of all communication pairs is over, and , it is determined that no communication pair breaks the coalition structure in this iteration , the coalition structure reaches stability, and the stable coalition structure is output ; otherwise, , return to step 11.

[0021] Preferably, the opportunistic channel access method of the fixed coalition structure comprises:

[0022] Step 21: based on the given coalition structure , the system average throughput is calculated according to the distributed wireless network channel statistical characteristic parameters , the first decision threshold , and the second decision threshold

[0023] Step 22: a plurality of sources perform channel competition; from the beginning of the micro time slot with a duration , all sources independently compete for the channel by sending an RTS data packet with a probability , and the number of successful channel competitions is n, and the first successful competition is recorded as n=1;

[0024] Step 23: the sink judges which category it belongs to according to the calculation result of step 21, if the communication pair , enter step 24; otherwise, the communication pair , go to step 29;

[0025] Step 24: compare the direct connection channel signal-to-noise ratio with the first decision threshold If , the current access opportunity is abandoned and the process returns to step 22; if , the direct channel is selected for channel access and the transmission rate is , and the process returns to step 22 after a single transmission; otherwise , further probing of the relay channel is selected and the process proceeds to step 25.

[0026] Step 25: The optimal number of relay nodes and the optimal set of relay nodes are selected for probing, and for the secondary decision threshold , if , satisfies , the optimal number of relay nodes for probing is ; if , the optimal number of relay nodes for probing is ; otherwise , the optimal number of relay nodes for probing is , and the optimal set of relay nodes for probing is , and the process proceeds to step 26.

[0027] Step 26: Probing of the relay set is performed; the destination sends a CTS packet to the potential relay nodes to be probed and the potential relay nodes and the source , receive the CTS packet, and then the first-hop relay channel signal-to-noise ratio from the source to itself is returned to the destination through an RTS packet, and the destination demodulates and estimates the second-hop relay channel signal-to-noise ratio from the source to itself upon receiving the RTS packet, and all source nodes belonging to the set reply to the RTS packet in turn, and the destination obtains the two-hop link signal-to-noise ratios of all source nodes in the set as relays, and calculates the maximum channel received signal-to-noise ratio of the source for transmission with the assistance of the best relay node in the set , and the corresponding best relay node is , and the process proceeds to step 27. Step 27: If , it is determined that the access benefit is greater than the abandonment benefit, and further access channel selection is performed, and the process proceeds to step 28; otherwise, the access opportunity is abandoned and the process returns to step 22.

[0028] Step 27: If , it is determined that the access benefit is greater than the abandonment benefit, and further access channel selection is performed, and the process proceeds to step 28; otherwise, the access opportunity is abandoned and the process returns to step 22. ​

[0029] Step 28: if , the source transmits in the direct channel at the maximum achievable rate for the time , and returns to step 22 after the transmission; otherwise, the source transmits in the two-phase transmission at the maximum achievable rate with the assistance of the best relay in the coalition for the time , and returns to step 22 after the transmission;

[0030] Step 29: if the signal-to-noise ratio of the direct channel is , the direct channel is selected for channel access, and the sink sends a CTS to the source and all other sources, and the source transmits data in the direct channel at the maximum achievable rate for the time , and all other sources wait for the time , and returns to step 22 after the single transmission; otherwise, the sink gives up the access opportunity, and broadcasts a CTS packet to all source nodes, and all source nodes start channel competition again in the next time slot, and returns to step 22.

[0031] According to the specific embodiments of the application, the following technical effects are provided:

[0032] The optimal selective relay-aware access method provided by the embodiments of the application can simultaneously exist as a relay node, increases role diversity, and fully utilizes time, space, and equipment resources; an optimal probe relay strategy is used to select the best relay probe set, associates the time cost of probe relay with the probe benefit, and avoids unnecessary probe cost; the wireless communication network is modeled according to the actual situation, a channel parameter model is constructed by taking the distance between nodes as a reference, the network heterogeneity is reflected, different access strategies are used for different source-sink pairs, and the corresponding decision thresholds depend on the channel statistical characteristics, and have strong flexibility and applicability; all decision thresholds and global parameters can be calculated offline under the condition of statistical information based on the wireless network channel, an iterative algorithm with linear complexity is proposed, the optimal solution can be quickly converged, the calculation time can be effectively reduced for a large-scale distributed network, and errors are not prone to occur; the concept of coalition game is introduced, a benefit function and a coalition ordering operator of a communication pair are constructed, the cooperation motivation between communication nodes is considered, the cooperation relationship is stable and reasonable. The coalition formation algorithm can be periodically repeated relying on the user mobility characteristics, has low calculation complexity, has strong adaptability to environmental changes, and has strong realizability.

[0033] Of course, implementing any product of the application does not necessarily require achieving all the advantages described above at the same time. BRIEF DESCRIPTION OF DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0035] Figure 1 is a flow chart of an optimal selective relay sensing access method provided by an embodiment of the present application;

[0036] Figure 2 is a system model diagram provided by an embodiment of the present application;

[0037] Figure 3 is a potential relay detection process schematic diagram provided by an embodiment of the present application;

[0038] Figure 4 is an opportunistic channel access flow chart provided by an embodiment of the present application;

[0039] Figure 5 is a system average throughput calculation algorithm flow chart provided by an embodiment of the present application;

[0040] Figure 6 is a convergence and stability simulation result diagram provided by an embodiment of the present application;

[0041] Figure 7 is a network average throughput simulation result diagram provided by an embodiment of the present application. DETAILED DESCRIPTION

[0042] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art belong to the scope of protection of the present application.

[0043] Referring to Figure 1 , an optimal selective relay sensing access method provided by an embodiment of the present application is shown in the figure, which can include: Figure 1

[0044] ​Determining a set of communication pairs, a current alliance structure, and a number of transfers for a given social trust network; the social trust network includes a heterogeneous wireless collaborative network consisting of multiple source and sink pairs with a three-level trust relationship; sources and sinks within the same alliance structure serve as relays for each other;

[0045] All communication nodes in the communication pair set broadcast short packets containing location information in sequence according to their respective node IDs, so that after a round of broadcasting, each communication node obtains the location information of all other communication nodes;

[0046] Statistical information of the channels between the communication nodes is calculated based on the location information; the benefit of each communication pair under the current alliance structure is calculated using a benefit function according to the statistical information, and the benefits are used to evaluate whether each communication pair is motivated to break the current alliance structure to form a new alliance structure. If it is determined that no user has the motivation to break the current alliance structure, a stable alliance structure is output. In specific implementation, the embodiment of the present application can provide the method for outputting the stable alliance structure, including:

[0047] Step 11: Current Alliance Structure , calculate the communication pair through the benefit function Stay in the current alliance The benefits within the alliance and the benefits of joining other alliances are evaluated to see whether there is a motivation to transfer. If so, proceed to step 12.

[0048] Step 12: OK , the alliance Join the communication pair Federation history collection In the communication Leave its current alliance Otherwise, there is no need to update the alliance history set , communication pair Leave the alliance directly ; Transfer factor , go to step 13;

[0049] Step 13: Communication Pair Join a new alliance with transfer motivation. If there is more than one alliance that meets the transfer requirements, choose the alliance with the greatest benefit to join; proceed to step 14;

[0050] Step 14: Communication Pair Update the current alliance structure and the new alliance structure Inform other communication pairs by broadcasting; after the single iteration cycle time ends, go to step 15;

[0051] Step 15: One iteration of all communication pairs ends, and determines that this iteration does not break the coalition structure The coalition structure reaches stability, and outputs the stable coalition structure ; otherwise, goes back to step 11.

[0052] The revenue function is represented by the following formula:

[0053]

[0054] In the formula: represents the revenue of the communication pair , represents the condition, is the expected cost of the probe relay; represents the probability that the condition in the square brackets is true; represents the average throughput of the system, represents the first decision threshold, represents the access revenue function of the communication pair , represents the access revenue function of the communication pair , a set of communication pairs, represents the channel coherence time, represents the average time of a single observation, represents the probe time, represents the transmission probability of the source, represents the received signal-to-noise ratio of the direct connection channel of the th source to its sink.

[0055] The coalition ordering operator is defined as follows:

[0056] For the communication pair , the coalition ordering operator is defined as , represents that the coalition is better than the coalition , and the coalition ordering operator further includes the equal ordering relationship between the coalitions on the basis of the coalition ordering operator

[0057] The coalition ordering operator is quantified to the revenue of the communication pair , and is represented by the following formula:

[0058] ​

[0059] wherein, denotes a sufficient condition, is a preference function and equals the payoff function when the condition is met .

[0060] Whether there is a transition of the machine is evaluated by the following way:

[0061] Given a coalition structure , if the condition is met, the pair of communicating parties has the incentive to move from the current coalition to the coalition , if the pair of communicating parties moves from the coalition to the coalition , the coalition structure changes from to .

[0062] Based on the stable coalition structure, distributed channel contention and opportunistic channel access are performed according to the opportunistic channel access method based on the fixed coalition structure; the opportunistic channel access method based on the fixed coalition structure comprises that, under the stable coalition structure, multiple sources contend for a channel by transmitting and receiving probe data packets in a distributed manner, measure a channel state in real time, and dynamically select a best relay channel in all coalitions thereof for opportunistic access.

[0063] The opportunistic channel access method of the fixed coalition structure comprises:

[0064] Step 21: Based on the given coalition structure , the system average throughput , a first decision threshold and a second decision threshold are calculated according to distributed wireless network channel statistical characteristic parameters; in actual implementation, the system average throughput may be represented by the following formula:

[0065]

[0066] wherein, denotes a payoff of direct channel access, 0 denotes an expected payoff of giving up access, denotes a payoff function of probing a potential relay.

[0067] The first decision threshold is defined as follows:

[0068] For each fixed pair of communicating parties , the maximum payoff function of probing a potential relay is A monotonically increasing function of For the equation The only solution, For the equation The only solution of

[0069] Second-level judgment threshold The definition is as follows:

[0070] For each fixed communication pair , the profit difference function of detecting potential relays for A monotonically increasing function of For the equation The only solution of .

[0071] The profit function It is expressed by the following formula:

[0072]

[0073] Where: Indicates the channel transmission time after the detection relay, represents the channel coherence time, Detection Relay time, Indicates the achievable rate of the direct channel. Indicates the destination The signal-to-noise ratio of the best potential relay node in its alliance potential relay set is obtained.

[0074] Step 22: Multiple Sources Compete for channel; from duration At the beginning of the mini-slot, all sources have the probability Send RTS packets to independently compete for the channel. The number of successful channel competitions is n, and the first successful competition is recorded as n=1;

[0075] Step 23: Sink According to the calculation result of step 21, determine which category it belongs to. If Communication pair , go to step 24; otherwise the communication pair , go to step 29;

[0076] Step 24: Set the direct channel signal-to-noise ratio First-level decision threshold Compare, if , then give up this access opportunity and return to step 22; if , then the direct channel is selected for channel access, and the transmission rate is , after the single transmission is completed, return to step 22; otherwise , select further detection of relay channels and go to step 25;

[0077] Step 25: Select the optimal number and set of relay nodes for detection, and for the secondary decision threshold , if for ,satisfy , then the optimal number of relay nodes for detection is ;like , the optimal number of relay nodes for detection is ;otherwise , the optimal number of relay nodes for detection is ; The optimal detection relay node set is , go to step 26;

[0078] Step 26: Perform relay collection Detection; Sink Send CTS packets to potential relay nodes to be detected and Xinyuan , Potential relay nodes in After receiving the CTS packet, the source The signal-to-noise ratio of the first-hop relay channel to itself Return to the destination via RTS packet , Xinjiu After receiving the RTS packet, demodulate it , and estimate the source The signal-to-noise ratio of the second-hop relay channel to itself , all belonging to the set After the source replies to the RTS packet in sequence, the destination obtains the set The signal-to-noise ratio of the two-hop link with all source nodes as relays is calculated to obtain the source In the collection The maximum channel received signal-to-noise ratio for transmission with the assistance of the best relay node within , the corresponding best relay node is , go to step 27;

[0079] Step 27: If , it is determined that the access benefit is greater than the abandonment benefit, and further access channel selection is performed, and the process goes to step 28; otherwise, the access opportunity is abandoned and competition is restarted, and the process returns to step 22;

[0080] Step 28: If , then the source Here I am time at the maximum achievable rate in a direct channel transmitting, and returning to step 22 after the transmission; otherwise, the source transmits data to the sink and all potential relay nodes in the coalition with the assistance of the relay in two stages, and returning to step 22 after the transmission; in a specific implementation, the two-stage transmission can include , and returning to step 22 after the transmission; in a specific implementation, the two-stage transmission can include

[0081] In the first stage, the source broadcasts data to the sink and all potential relay nodes;

[0082] In the second stage, the best single relay node transmits the received signal to the sink, and the sink receives two signals from the direct link and the relay channel.

[0083] Step 29: If the signal-to-noise ratio of the direct link is , the direct link is selected for channel access, and the sink sends a CTS to the source and all other sources, so that the source transmits data on the direct link at the maximum achievable rate for a time period, and all other sources wait for a time period, and returning to step 22 after a single transmission; otherwise, the sink gives up the access opportunity, and broadcasts a CTS packet to all source nodes, and all source nodes start channel competition again in the next time slot, and returning to step 22. The method provided by the embodiments of the present application is used for forming a game of a distributed coalition structure and making a distributed channel detection and access decision in a heterogeneous wireless cooperative network composed of multiple source-sink pairs. Based on the willingness and motivation of user cooperation, the source and the sink located in the same coalition body can relay each other, and multiple communication pairs decide whether to break the current coalition structure according to the benefits obtained in different coalition structures, so as to form a stable coalition structure. Under a given coalition structure, multiple sources compete for a channel by transmitting and receiving probe data packets in a distributed manner, measure the channel state in real time, dynamically select the best relay channel in all coalition bodies for opportunistic access, and realize data transmission and reception with the assistance of the relay. The simulation results verify the convergence and stability of the distributed coalition formation game algorithm, and the distributed opportunistic channel access method based on the stable coalition structure can realize effective networking of the wireless distributed cooperative network and improve the system average and network spectrum resource utilization rate.

[0084] The method provided by the embodiments of the present application is used for forming a game of a distributed coalition structure and making a distributed channel detection and access decision in a heterogeneous wireless cooperative network composed of multiple source-sink pairs. Based on the willingness and motivation of user cooperation, the source and the sink located in the same coalition body can relay each other, and multiple communication pairs decide whether to break the current coalition structure according to the benefits obtained in different coalition structures, so as to form a stable coalition structure. Under a given coalition structure, multiple sources compete for a channel by transmitting and receiving probe data packets in a distributed manner, measure the channel state in real time, dynamically select the best relay channel in all coalition bodies for opportunistic access, and realize data transmission and reception with the assistance of the relay. The simulation results verify the convergence and stability of the distributed coalition formation game algorithm, and the distributed opportunistic channel access method based on the stable coalition structure can realize effective networking of the wireless distributed cooperative network and improve the system average and network spectrum resource utilization rate.

[0085] The method provided by the embodiments of the present application is used for forming a game of a distributed coalition structure and making a distributed channel detection and access decision in a heterogeneous wireless cooperative network composed of multiple source-sink pairs. Based on the willingness and motivation of user cooperation, the source and the sink located in the same coalition body can relay each other, and multiple communication pairs decide whether to break the current coalition structure according to the benefits obtained in different coalition structures, so as to form a stable coalition structure. Under a given coalition structure, multiple sources compete for a channel by transmitting and receiving probe data packets in a distributed manner, measure the channel state in real time, dynamically select the best relay channel in all coalition bodies for opportunistic access, and realize data transmission and reception with the assistance of the relay. The simulation results verify the convergence and stability of the distributed coalition formation game algorithm, and the distributed opportunistic channel access method based on the stable coalition structure can realize effective networking of the wireless distributed cooperative network and improve the system average and network spectrum resource utilization rate. ​

[0086] The method provided by the embodiments of the present application takes a time discretization manner to determine an algorithm calculation period according to node mobility for a user node with mobility, and one period is divided into three stages: a neighbor discovery stage, an alliance body forming stage and an opportunity channel access stage. The neighbor discovery stage performs user node information collection (mainly node position information); the alliance body forming stage forms a stable alliance body structure according to alliance body forming game algorithm rules; finally, the opportunity channel access stage performs global single channel competition, potential relay channel selective detection and optimal channel access in the alliance body based on a distributed optimal channel access method according to the current stable alliance body structure and in combination with the distance between nodes and channel statistical information.

[0087] The system model of the wireless distributed cooperative network considered by the present application is shown in Figure 1 . The model describes a wireless distributed cooperative network channel access process based on source node assisted transmission in an alliance body. The system contains multiple source nodes (i.e., source ) and destination nodes (i.e., destination ), the source-destination pair satisfies a mapping relationship, and the information transmitted by the source is transmitted to the destination through a direct connection / relay channel.

[0088] All communication pairs in the network spontaneously form multiple disjoint alliance bodies, as shown by the dashed ellipses S1, S2 and S3 in Figure 1 . The source nodes of the communication pairs in the same alliance body can relay each other, and the communication pairs between different alliance bodies do not cooperate. Based on a given alliance body structure, different source-destination pairs can select different access modes. The specific cases are divided into three types: direct connection channel access (without detecting a relay); relay assisted channel access; and direct connection channel access (a relay in the alliance body is detected, but the channel condition of the direct connection channel is better). When all access channel conditions are poor, the source can select to give up the access opportunity and re-perform channel competition, so as to increase the transmission time of other communication pairs with better channel conditions, thereby increasing the system average throughput of the entire distributed network.

[0089] For ease of description, based on the system model shown in Figure 2 , the basic parameters are defined as follows:

[0090] The source-destination pairs are K, wherein the source index number is , and the destination index number is ; the K communication pairs spontaneously form multiple alliance bodies, and the user source nodes in the same alliance body can relay each other for assisted transmission. The alliance body forming theory framework of the communication pairs is represented as , wherein, denote the set of communication pairs participating in the game, denote the payoff vector of each coalition.

[0091] denote the coalition structure as where denote the number of coalitions contained in , for all coalitions , if and all coalitions are disjoint, then the coalition structure is called a coalition partition. For a communication pair , if it belongs to a coalition in the coalition partition , then the coalition can also be denoted as

[0092] According to the principle and characteristics of the distributed cooperative network opportunistic channel access, the payoff of a coalition has the non-transferable property, i.e., the payoff of the communication pairs in a coalition cannot be freely distributed by the coalition. Therefore, for a coalition structure , the payoff of a coalition is denoted as the set of the payoffs of the communication pairs in the coalition, as follows:

[0093]

[0094] where is the payoff of the communication pair when it belongs to the coalition under the given coalition structure.

[0095] All nodes assume time synchronization and contend for the channel in a distributed manner based on micro-slots. At the beginning of each contention micro-slot, all sources independently transmit a channel contention RTS packet with the same probability . When and only when there is only one source transmitting an RTS packet in the same micro-slot, the source is the winning source, which is called a successful channel contention. The process from the beginning of the channel contention to the appearance of the winning source is defined as an observation. For each observation process, the time experienced before the appearance of the winning source is random. Since each channel contention is independent, the total number of channel contentions experienced in a single observation follows a geometric distribution with parameter , and the average time of a single observation is:

[0096]

[0097] where denotes the time of transmitting an RTS packet, denotes the time of transmitting a CTS packet,​ denotes the number of source-destination pairs, denotes the duration of the idle time slot, the time of collision can be used denotes.

[0098] Consider a random channel fading model with statistical characteristics. The received signal-to-noise ratio of the direct channel from the i-th source to its destination is denoted as , the received signal-to-noise ratio of the first-hop channel from the i-th source to the j-th source and the second-hop channel from the i-th source to the k-th destination are denoted as:

[0099] and .

[0100] wherein, denotes the distance between and , denotes the distance between and , denotes the distance between and , denotes the channel fading depth.

[0101] Both the direct channel and the relay channel are subject to Rayleigh fading model, , and denote the channel fading in the direct, first-hop and second-hop channels respectively, in addition to the distance factor, subject to exponential random distribution, with expected values of , and respectively, and noise subject to Gaussian distribution with normalized variance. It is to be noted that the method provided by the present application is applicable to typical wireless channels such as Rician channel, Nakagami channel, etc.

[0102] The achievable rate of the direct channel is , the received signal of the relay-assisted channel transmission is mainly composed of two parts, the direct channel signal and the relay two-hop channel signal, and the maximum channel received signal-to-noise ratio of the source transmitting with the help of the source is .

[0103] The achievable rate of the channel is:

[0104] ​​​​​

[0105] The channel coherence time is denoted as , detection The time of a relay is recorded as , then the channel transmission time after the detection relay is .

[0106] The present invention adopts a sequential detection mechanism to detect relays, and detects relay sets. The process is as follows Figure 3 As shown. Given a federation partition , if the winning source is , communication pair Belong to the alliance , then the alliance Other source nodes within Can be used as a communication pair The set of potential relays of these source nodes is expressed as , Indicates the alliance Internal elimination source The number of all other source nodes except Received from its source After receiving the RTS packet, the direct channel CSI is obtained. If the destination Select further detection relay channel, then it selects the optimal number of detection relays , and the corresponding detection relay set , winning destination Broadcast a CTS packet to all source nodes, and then communicate with the At the same time in the alliance Other source nodes within (Potential relay) can determine whether it is the detected object based on the received CTS. If , then the node The source The signal-to-noise ratio of the first-hop relay channel to itself Pass and RTS back to the destination , Xinjiu After receiving the RTS packet, you can demodulate it , and estimate the source The signal-to-noise ratio of the second-hop relay channel to itself .

[0107] All belonging to the set After the source (potential relay) replies to RTS in turn, the destination Then get the collection The signal-to-noise ratio of the two-hop link with all source nodes as relays is expressed as a set:

[0108]

[0109] The relay link signal-to-noise ratio set can be calculated:

[0110]

[0111] The source In the collection The maximum channel received signal-to-noise ratio for transmission with the assistance of the best relay node within is:

[0112]

[0113] The best relay node is expressed as:

[0114]

[0115] Then Xin Su Detecting potential relay sets The obtained relay auxiliary channel signal-to-noise ratio is:

[0116]

[0117] From the accommodation Send CTS packet to detect the relay channel and start Relay detection time, destination Obtained its alliance potential relay set The signal-to-noise ratio of the best potential relay node , expressed as , after comparing the direct and relay channel states, the destination Make further access decisions.

[0118] For selecting the number of detection relays , the corresponding detection relay set , specifically described as: for the source and xinxu If you select Detect potential relays, then the detection relay set Expressed as:

[0119]

[0120] in, Indicates all potential relays In the The relay node index number of the value.

[0121] The two-level decision process after successful channel contention is defined as an observation process definition, specifically described as follows: for the nth observation, after the nth successful channel contention, the source Winning channel, its sink Obtaining the n-th observed direct connection channel SNR If the sink If the sink chooses to stop and access the direct connection channel at this time, the amount of information that can be transmitted by accessing the channel is:

[0122]

[0123] The time cost is the time spent from the beginning of the first channel competition after the end of the previous transmission to the end of the current transmission:

[0124]

[0125] Wherein, The time spent in the n-th channel competition is , and the average time is , The time spent in the n-th channel competition is .

[0126] If the relay is detected , then , otherwise, ; if the sink selects to further detect the relay channel, and the number of relay nodes detected is , then the set of potential relay nodes detected is , and the maximum achievable rate after detection is:

[0127]

[0128] At this time, if the sink stops and accesses the direct connection / relay channel, the benefit is:

[0129]

[0130] Since the channel coherence time is fixed, the time cost is constant. Based on this, if the winning sink chooses to stop and access the channel in the Nth observation, the instantaneous throughput is represented as:

[0131] .

[0132] Based on the above distributed wireless cooperative network model, the purpose of the method proposed by the application is to design a distributed alliance formation game algorithm, so that all communication pairs in the network can spontaneously converge to a stable alliance structure ; for a given alliance structure , find the optimal intelligent channel access and decision method, that is, find the optimal strategy , achieving the optimal system average throughput:

[0133]

[0134] in, represents expectation, and sup represents the lowest upper bound.

[0135] To derive the benefit function of the communication pair, for a given alliance structure The present invention first designs an optimal selective relay sensing access method based on a fixed alliance structure. , in order to find the optimal stopping time, the implementation steps are as follows Figure 4 The specific description is as follows:

[0136] Step 21: Based on the given alliance structure , according to the statistical characteristic parameters of the distributed wireless network channel, the average system throughput is obtained through offline iterative calculation , first-level judgment threshold , the second-level judgment threshold , the specific function definition and calculation process are as follows;

[0137] (1) Definition of related functions

[0138] Communication pair Detection Alliance Internal potential relay set The profit function Defined as:

[0139]

[0140] Communication pair The optimal number of detection relays for detecting potential relays Defined as:

[0141]

[0142] The maximum profit function corresponding to the detection relay .

[0143] Communication pair Detection potential relays and probes The profit difference function of potential relays is defined as: .

[0144] First-level judgment threshold definition:

[0145] For each fixed communication pair , the maximum profit function for detecting potential relays for a monotonic increasing function of is the unique solution to the equation , is the unique solution to the equation .

[0146] Secondary decision threshold is defined as

[0147] For each fixed communication pair , the gain difference function of probing potential relay is a monotonic increasing function of is the unique solution to the equation .

[0148] Communication pair classification set is defined as

[0149] Based on the decision threshold , if , the communication pair belongs to the classification set , and there is ; if , the communication pair belongs to the classification set , and there is .

[0150] When the input parameter , .

[0151] System average throughput satisfies the following equation:

[0152]

[0153] Where the first term on the left side represents the gain of direct channel access; the second term 0 represents the expected gain of giving up access, and the third term is the gain function of probing potential relay when .

[0154] (2) Iterative algorithm for calculating system average throughput , primary decision threshold and secondary decision threshold

[0155] Based on the above definitions, the present application proposes an iterative algorithm for offline calculation to calculate the system average throughput , decision threshold and communication pair classification set , and the algorithm flow chart is shown in Figure 5 . ​

[0156] Figure 5 middle, It is the convergence threshold of the iterative algorithm, which is set according to the accuracy requirement. The typical value is , is the step size of iterative update, and its value satisfies:

[0157]

[0158] in, is the initial value of the first iteration, is the result of the kth iteration, is the accuracy of the kth iteration, which is calculated as:

[0159]

[0160] in, For communication The access benefit function at time , its expression is:

[0161]

[0162] in, For communication The access benefit function at time , its expression is:

[0163] in, For the equation The only solution, is the direct channel signal-to-noise ratio The probability integral function of . After a finite number of iterations, Can converge to global parameters , and output all communication pairs The decision threshold and correspondence pair classification set .

[0164] Step 22: Multiple sources compete for the channel. At the beginning of the mini-slot, all sources have the probability Send RTS packets to independently compete for the channel. The number of successful channel competitions is n, and the first successful competition is recorded as n=1. The following three situations may occur:

[0165] If no source sends an RTS packet in the mini-time slot, the channel is idle and all sources compete for the channel in the next time slot.

[0166] If two or more sources send RTS packets at the same time, a packet collision occurs and they need to continue competing in the next time slot;

[0167] If there is only one source, such as If the source sends an RTS packet, it will get the channel access opportunity and is called the winning source. By receiving the RTS data packet and using the training sequence carried in it, the sink corresponding to the winning source will be Get the signal-to-noise ratio of the direct channel and maximum achievable rate , the signal-to-noise ratio of the first-hop relay channel from the source to itself obtained by other source nodes (potential relays) in the same alliance;

[0168] Step 23: Sink According to the calculation result of step 21, determine which category it belongs to. If Communication pair , go to step 24; otherwise the communication pair , go to step 29;

[0169] Step 24: Set the direct channel signal-to-noise ratio and decision threshold Compare, if , then give up this access opportunity and return to step 22; if , then the direct channel is selected for channel access, and the transmission rate is , after the single transmission is completed, return to step 22; otherwise , select further detection of relay channels and go to step 25;

[0170] Step 25: Select the optimal number and set of relay nodes to be detected. Specifically, for the secondary decision threshold , if for ,satisfy , then the optimal number of relay nodes for detection is ;like , then the optimal number of relay nodes for detection is ;otherwise , the optimal number of relay nodes for detection is ; The optimal detection relay node set is , go to step 26;

[0171] Step 26: Perform relay collection Specifically, the destination Send CTS packets to potential relay nodes to be detected and Xinyuan , Potential relay nodes in After receiving the CTS packet, the source The signal-to-noise ratio of the first-hop relay channel to itself Return to the destination via RTS , Xinjiu After receiving the RTS packet, you can demodulate it , and estimate the source The signal-to-noise ratio of the second-hop relay channel to itself All belonging to the set After the source (potential relay) replies to RTS in turn, the destination obtains the set The signal-to-noise ratio of the two-hop link with all source nodes as relays is expressed as the set , the source can be calculated In the collection The maximum channel received signal-to-noise ratio for transmission with the assistance of the best relay node within , the corresponding best relay node is , go to step 27;

[0172] Step 27: If , it means that the access benefit is greater than the abandonment benefit, and further access channel selection is performed, and the process goes to step 28; otherwise, the access opportunity is abandoned and competition is restarted, and the process returns to step 22;

[0173] Step 28: If , then the source In the subsequent time at the maximum achievable rate in a direct channel Transmission, after the transmission is completed, return to step 22; otherwise, the source is the best relay in the alliance Assisted at the maximum achievable rate Two-stage transmission is performed. In the first stage, the source Broadcast data to its destination and all potential relay nodes. In the second phase, the best single relay node The received signal is forwarded to the destination, and then the destination receives two signals from the direct link and the relay channel. The transmission time is , after the transmission is completed, return to step 22;

[0174] Step 29: If the direct channel signal-to-noise ratio , then select the direct channel for channel access, the destination Send CTS to the source and all other sources, In the next time, at the maximum achievable rate Data transmission is carried out on the direct channel, and all other sources are Wait for a certain time, and return to step 22 after a single transmission is completed; otherwise, the destination Abandon this access opportunity and broadcast the CTS packet to all source nodes. All sources restart channel competition in the next time slot and return to step 22.

[0175] In the distributed cooperative communication network, the application provides a wireless distributed cooperative network opportunity channel access method based on coalition formation game theory, which realizes the steps as shown in the figure, mainly including four stages, and the specific description is as follows: Figure 1

[0176] I. Stage one-initialization stage. All communication pairs exist independently, and for the communication pair set , the initial coalition structure is . The number of transitions .

[0177] II. Stage two-neighbor discovery stage. All communication nodes in the network broadcast short packets containing position information according to their node ID in turn, and after one round of broadcasting, each node obtains the position information of all other nodes. The distance between nodes that do not receive the broadcast packet is too far, and the cooperation relationship does not exist by default. The unknown position information does not affect the subsequent algorithm.

[0178] III. Stage three-coalition formation stage. Based on the user position information, the statistical information of the channel between each user node can be obtained. The revenue function of each communication pair under the current coalition structure is calculated, and whether the communication pair has the motivation to break the current coalition structure to form a new coalition structure is evaluated. If no user has the motivation to break the current coalition structure, the coalition structure is stable. For a mobile network, a mobile time period is set according to the moving speed, and the stage two is returned at the end of each time period . The implementation steps of the coalition formation algorithm are described as follows:

[0179] Step 1: for the given coalition structure , the first iteration is . The communication pair calculates the revenue of staying in the current coalition and the revenue of joining other coalitions, and evaluates whether there is a transition motivation. If there is, go to step 2, otherwise, go to step 4. The specific description and definition are as follows:

[0180] (1) Algorithm iteration and signaling interaction mechanism description:

[0181] According to the principle of node ID from small to large, the first iteration is to set different start iteration times for each communication pair. Each communication pair only executes steps 1 to 4 in its own time period. For a given algorithm iteration period, the same order will be followed in each subsequent iteration period. With this mechanism, the broadcast packet collision of each communication pair can be avoided.

[0182] (2) Related definitions: ​

[0183] The revenue function is defined as:

[0184] In the distributed cooperative network scenario of the present application, based on the opportunity channel access method based on the fixed alliance body structure proposed in the foregoing, the revenue of a communication pair may be expressed as the instantaneous average throughput obtained by accessing the channel, and the calculation formula is:

[0185]

[0186] wherein, represents a condition, and when the condition in the square brackets is met, the value is 1, otherwise 0; is the expected cost of detecting a relay, which is calculated by Monte Carlo random simulation; represents the probability that the condition in the square brackets is true; is the probability that the in-network communication pair gives up access after winning the channel, and the calculation formula is:

[0187]

[0188] Alliance body ordering operator definition:

[0189] For a communication pair , the alliance body ordering operator is defined as: represents that the alliance body is strictly superior to the alliance body , and the alliance body ordering operator further includes the equal ordering relationship between the alliance bodies on the basis of the alliance body ordering operator

[0190] Quantifying the alliance body ordering operator to the revenue of the communication pair , there is:

[0191]

[0192] wherein, represents a necessary and sufficient condition, is a preference function, which is equal to the revenue function when the condition is met.

[0193] Specifically as follows:

[0194]

[0195] wherein, is the alliance body history set, and represents a communication pair ​​Layer once joined and then left the coalition, considering the wireless cooperative network characteristics, any communication pair has the power to decide not to cooperate, then the single coalition Will not be added to the coalition history set .

[0196] Preference function The condition on the right side of the equation Indicates that only when the joining of the communication pair Will not reduce the benefits of other communication pairs in the coalition , its benefits are valid, and the communication pair Will not join the same coalition repeatedly (except for single coalition).

[0197] Transfer definition:

[0198] Given the coalition structure , if , the communication pair has the motivation to transfer from the current coalition To the coalition , if the communication pair Transfers from the coalition To the coalition , the coalition structure changes from To .

[0199] Step 2: if , add the coalition To the communication pair's coalition history set , then leave its current coalition , otherwise, there is no need to update the history set , directly leave the coalition . Transfer factor , enter step 3;

[0200] Step 3: the communication pair joins the new coalition that exists in step 1 that has the motivation to transfer, if there is more than one coalition that meets the transfer requirements, then select the coalition with the highest benefits to join. Enter step 4;

[0201] Step 4: the communication pair Updates the current coalition structure , and informs other communication pairs of the new coalition structure In a broadcast manner. After the end of a single iteration period, enter step 5;

[0202] Once the iteration of all communication pairs is over, since Is a global variable, the transfer of any communication pair Will increase the value of the corresponding channel gain, thus, if , it means that this iteration has no communication pair breaking the coalition structure , the coalition structure reaches stability, and the stable coalition structure is output ; otherwise, , return to step 1. After a single moving period , return to phase two.

[0203] Four, phase four--opportunity channel access phase.

[0204] Based on the stable coalition structure given in phase three , the opportunity channel access method based on the fixed coalition structure proposed in this patent , distributed channel competition and opportunity channel access are carried out.

[0205] The present application has been strictly simulated and tested, and the effectiveness and process realizability of the method proposed in the patent are verified by computer simulation. In a wireless network with a range of 5km*5km, 10 source-destination communication pairs are set, and the distance between the source and the destination is random. All direct channels and relay channels are subject to Rayleigh fading, and the expected configuration is , in dB. The main configuration parameters of the network model are , , .

[0206] First, numerical simulation is used to verify the convergence and stability of the distributed coalition formation algorithm proposed. The channel parameters are configured as , and 10 communication pairs in the network operate in a distributed manner, and the coalition is formed through the transfer operation.

[0207] Figure 6 The stable coalition structure formed after several iteration periods is shown. Through numerical experiments, the coalition formation process is described as follows. In the initial iteration, all pairs do not cooperate. After 3 iteration periods, no user pair breaks the current coalition structure, and the network coalition structure at this time is convergent and stable.

[0208] Figure 6 In the figure, different shaped icons are used to distinguish communication pairs, and the source and the destination of the same communication pair use the same shaped icon, and are distinguished by corresponding symbols. It can be seen that the final stable coalition structure contains 5 coalitions. They are coalition , coalition , coalition , coalition and coalition . It can be seen that coalitions , and The communication pairs in the vicinity of each other can relay for each other, thus are more willing to form a cooperative coalition.

[0209] Unlike them, the communication pair 1 has good direct channel condition and is unwilling to cooperate, thus it forms a single coalition by itself .

[0210] In addition, the communication pair 7 has poor direct channel condition and hopes to join a nearby coalition However, since the source of the communication pair 7 cannot provide efficient relay links for other communication pairs in the coalition , the joining of the communication pair 7 will result in the damage of the benefits of other communication pairs in the coalition Thus, the communication pair 7 forms a single coalition by itself .

[0211] Table 1 Average throughput benefits of 10 communication pairs

[0212]

[0213] Secondly, the effectiveness of the proposed algorithm is verified from the individual benefits of the communication pairs by comparing with other three strategies. The three strategies are: non-cooperation strategy, cooperative relay full-probing strategy and large coalition strategy. For the non-cooperation strategy, all communication pairs only consider direct channel transmission; for the cooperative relay full-probing strategy, users form a coalition, but in the second probing, all relays are selected to be probed; for the large coalition strategy, all users cooperate with each other to form a large coalition, and in the relay probing, all relays are selected to be probed.

[0214] For all 10 communication pairs, the individual average throughput benefits under the four strategies are listed in Table 1. From the table, it can be seen that compared with the non-cooperation strategy, the coalition cooperation in the proposed strategy increases the average throughput benefits of most communication pairs, such as pairs 2, 3, 4, 5, 6, 8, 9 and 10, while some other communication pairs, such as pairs 1 and 7, suffer losses; in addition, in the cooperative strategy, since the proposed method adopts the optimal relay probing mechanism, compared with the cooperative relay full-probing strategy and the large coalition strategy, the proposed algorithm has higher individual average throughput benefits, and the benefits distribution among the users is more even. The necessity of the rational cooperation analysis is verified.

[0215] Finally, the effectiveness of the proposed algorithm is verified from the network average throughput by comparing with other three strategies. When the channel statistical parameter varies from 0 to 9 dB, the network average throughput curves are as shown in Figure 7It can be seen that when the direct and relay channel conditions become better, the network average throughput also increases. In addition, compared with the non-cooperation strategy, the network average throughput under the other three strategies is obviously improved; compared with the large alliance strategy, the cooperation strategies with multiple alliance bodies (cooperation relay full detection strategy and the proposed strategy) have improved the system average throughput due to the reduction of part of the detection overhead; compared with the cooperation relay full detection strategy, the proposed method further optimizes the selective relay detection strategy, further improving the performance under the alliance structure; the efficiency of the proposed algorithm is verified.

[0216] It can be seen that the optimal selective relay-aware access method provided by the application is based on a distributed wireless cooperative network with different cooperation relationships, proposes an opportunity channel access method based on a fixed alliance body structure, defines a mechanism for detecting potential relays in the alliance body, defines two-level decision thresholds according to the revenue function under different access conditions, and converts the complex problem into a linear decision problem.

[0217] All thresholds, global parameters, and source-destination pair classifications in the method can be obtained through offline calculation. An offline iterative algorithm is proposed for calculating global parameters and classifying communication pairs. The algorithm has low complexity and can converge to the optimal solution in a limited number of iterations.

[0218] In the method, the relay detection in the alliance body selects the optimal number of detected relays according to the expected revenue function, and the optimal relay set corresponding to the optimal number of detection. The expected revenue function is used to select the number of detected relays to avoid unnecessary detection overhead. The potential relay purgatory expectation is used to sort the relays and select the relay nodes to be detected first to achieve the best detection effect under fixed detection overhead.

[0219] The method is based on global parameters, classification sets, and two-level decision thresholds, and designs an opportunity channel access strategy based on a fixed alliance body structure. After the source successfully competes for the channel, it compares the sizes of the two decision thresholds to determine its classification interval and selects the corresponding opportunity access strategy. Then, by comparing the direct channel signal-to-noise ratio with the first-level decision threshold, it determines whether to further detect the relay channel. If the relay is selected for detection, it further compares the second-level decision threshold to select the optimal number of detected relays and the optimal relay set. Subsequently, based on the direct / relay channel information obtained through detection, the optimal access method is selected for access. The proposed method combines the physical layer and the network layer, fully utilizes multi-user diversity and relay diversity, and users cooperate with each other to optimize the overall system throughput of the network.

[0220] Based on the proposed opportunistic channel access method with fixed coalition structure, the revenue function of each communication pair in the coalition is derived, and based on the revenue function, the ordering operator between coalitions is defined, the iteration rule of coalition structure is formulated, and the coalition formation algorithm is designed, which can guarantee the convergence of the coalition structure to stability from any coalition structure.

[0221] Combining the coalition formation algorithm and the opportunistic channel access method based on fixed coalition structure, a wireless distributed cooperative network opportunistic channel access method based on coalition formation game theory is proposed, which mainly includes four stages of initialization, neighbor discovery, coalition formation and opportunistic channel access. The initialization stage sets the initial state of the network, the neighbor discovery stage acquires the information of the whole network, the coalition formation stage enables the communication pairs in the whole network to spontaneously form a stable coalition structure, and the opportunistic channel access stage performs corresponding opportunistic channel access according to the stable coalition structure. The proposed method is explained for network mobility and can adapt to the demand of mobile wireless mobile network.

[0222] In summary, the optimal selective relay sensing access method provided by the application can increase the role diversity by allowing the communication nodes to exist as relay nodes at the same time, and fully utilize the time, space and equipment resources. The optimal detection relay strategy is used to select the best relay detection set, which associates the time cost of detection relay with the detection benefit, thereby avoiding unnecessary detection cost. According to the actual situation of the wireless communication network, the wireless networking is modeled, the channel parameter model is constructed with the distance between nodes as the reference, the heterogeneity of the network is reflected, different access strategies are used for different source-destination pairs, and the corresponding decision thresholds depend on the channel statistical characteristics of each pair, which has strong flexibility and applicability. All decision thresholds and global parameters can be calculated offline based on the statistical information of the wireless network channel, and an iterative algorithm with linear complexity is proposed, which can quickly converge to the optimal solution. For large-scale distributed networks, the calculation time can be effectively reduced, and the algorithm is not prone to errors. The concept of coalition game is introduced, the revenue function of the communication pair and the ordering operator of the coalition are constructed, and the cooperation motivation between the communication nodes is considered, so that the cooperation relationship is stable and reasonable. Relying on the mobile characteristics of users, the coalition formation algorithm can be repeated periodically, has low computational complexity, and has strong adaptability to environmental changes, and is easy to implement.

[0223] It is to be noted that, in the present text, the terms such as first and second, and the like, are used merely to distinguish one entity or operation from another, without necessarily requiring or implying any such actual relationship or order between such entities or operations. Moreover, the terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but can also include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element preceded by "comprises a" does not, without more constraints, foreclose the existence of additional identical elements in the process, method, article, or apparatus that comprises the recited element.

[0224] From the description of the above embodiments, those skilled in the art can clearly understand that the present application can be implemented by means of software plus a necessary general hardware platform. Based on such an understanding, the technical solutions of the present application can be embodied in the form of a software product, which can be stored in a storage medium, such as a ROM / RAM, a magnetic disk, an optical disk, and the like, and includes a number of instructions to make a computer device (which can be a personal computer, a server, or a network device, etc.) execute the methods described in each embodiment or some parts of the embodiments of the present application.

[0225] Each of the embodiments in the present specification is described in a progressive manner, and the same or similar parts between the embodiments can be referred to each other, and each embodiment mainly describes the difference from other embodiments. In particular, for the system or system embodiments, since it is basically similar to the method embodiments, it is described more simply, and the related parts can be referred to the part of the description of the method embodiments. The above-described system and system embodiments are merely illustrative, and the units described as separate components can be or can not be physically separated, and the components displayed as units can be or can not be physical units, i.e., they can be located in one place, or can be distributed on multiple network units. Part or all of the modules can be selected to achieve the purpose of the present embodiment scheme according to actual needs. Those skilled in the art can understand and implement it without creative labor.

[0226] The above only describes the preferred embodiments of the present application, and is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application is included in the protection scope of the present application.

Claims

1. An optimal selective relay sensing access method, characterized in that: include: Determine the set of communication pairs, current alliance structure, and number of transfers for a given social trust network; The social trust network includes a heterogeneous wireless collaborative network consisting of multiple information source and information sink pairs with a three-level trust relationship; the information sources and information sinks within the same alliance structure serve as relays for each other; All communication nodes in the communication pair set broadcast short packets containing location information in sequence according to their respective node IDs, so that after a round of broadcasting, each communication node obtains the location information of all other communication nodes; Obtaining statistical information of channels between the communication nodes based on the location information; calculating the benefit of each communication pair under the current alliance structure using a benefit function according to the statistical information; and using the benefit to evaluate whether each communication pair is motivated to break the current alliance structure to form a new alliance structure; and outputting a stable alliance structure if it is determined that no user has the motivation to break the current alliance structure. Based on the stable alliance structure, distributed channel competition and opportunistic channel access are performed according to an opportunistic channel access method based on a fixed alliance structure. The opportunistic channel access method based on a fixed alliance structure includes, under the stable alliance structure, multiple information sources competing for channels by sending and receiving probe packets in a distributed manner, measuring channel states in real time, and dynamically selecting the best relay channel within all of its alliances for opportunistic access. The method for outputting a stable alliance structure includes: Step 11: Current Alliance Structure , calculate the communication pair through the benefit function Stay in the current alliance The benefits within the alliance and the benefits of joining other alliances are evaluated to see whether there is a motivation to transfer. If so, proceed to step 12. Step 12: OK , the alliance Join the communication pair Federation history collection In the communication Leave its current alliance Otherwise, there is no need to update the alliance history set , communication pair Leave the alliance directly ; Transfer factor , go to step 13; Step 13: Communication Pair Join a new alliance with transfer motivation. If there is more than one alliance that meets the transfer requirements, choose the alliance with the greatest benefit to join; proceed to step 14; Step 14: Communication Pair Update the current alliance structure and the new alliance structure Inform other communication pairs by broadcasting; after the single iteration cycle time ends, go to step 15; Step 15: One iteration of all communication pairs ends, and , confirm that no communication pair breaks the alliance structure in this iteration , the alliance structure reaches stability, and outputs a stable alliance structure ;otherwise, , return to step 11.

2. The optimal selective relay sensing access method according to claim 1, characterized in that: The profit function is expressed as follows: Where: Indicates communication pair of income, Indicates conditions, The expected overhead of the detection relay; Indicates the probability that the conditions in the square brackets are true; represents the average throughput of the system, Represents the first-level decision threshold, Indicates communication pair The access income letter at the time of Indicates communication pair The access benefit function when Communication pair set, represents the channel coherence time, represents the average time of a single observation, Indicates the detection time, represents the probability of the source sending, Indicates the Source To their destination The receive signal-to-noise ratio of the direct channel.

3. The optimal selective relay sensing access method according to claim 1, characterized in that: The alliance sorting operator is defined as follows: For communication pairs , define the alliance sorting operator , for the alliance , Indicates the alliance Better than alliance , in the alliance sorting operator The basis further includes the equal ranking relationship between alliance bodies; The alliance sorting operator Quantized to communication pairs The income is expressed by the following formula: Where, represents the necessary and sufficient condition, is a preference function and is equal to the benefit function when the conditions are met .

4. The optimal selective relay sensing access method according to claim 1, characterized in that: Assess the presence of motivation to transfer by: Given the alliance structure , if satisfied , then the communication pair has the motivation to leave the current alliance Transfer to the alliance If the communication pair From the alliance Transfer to the alliance , then the alliance structure changes from Changes to .

5. The optimal selective relay sensing access method according to claim 1, characterized in that: The opportunistic channel access method of the fixed alliance structure includes: Step 21: Based on the given alliance structure , according to the statistical characteristic parameters of the distributed wireless network channel, the average system throughput is calculated , first-level judgment threshold and the second-level judgment threshold ; Step 22: Multiple Sources Compete for channel; from duration At the beginning of the mini-slot, all sources have the probability Send RTS packets to independently compete for the channel. The number of successful channel competitions is n, and the first successful competition is recorded as n=1; Step 23: Sink According to the calculation result of step 21, determine which category it belongs to. If Communication pair , go to step 24; otherwise the communication pair , go to step 29; Step 24: Set the direct channel signal-to-noise ratio First-level decision threshold Compare, if , then give up this access opportunity and return to step 22; if , then the direct channel is selected for channel access, and the transmission rate is , after the single transmission is completed, return to step 22; otherwise , select further detection of relay channels and go to step 25; Step 25: Select the optimal number and set of relay nodes for detection, and for the secondary decision threshold , if for ,satisfy , then the optimal number of relay nodes for detection is ;like , the optimal number of relay nodes for detection is ;otherwise , the optimal number of relay nodes for detection is ; The optimal detection relay node set is , go to step 26; Step 26: Perform relay collection Detection; Sink Send CTS packets to potential relay nodes to be detected and Xinyuan , Potential relay nodes in After receiving the CTS packet, the source The signal-to-noise ratio of the first-hop relay channel to itself Return to the destination via RTS packet , Xinjiu After receiving the RTS packet, demodulate it , and estimate the source The signal-to-noise ratio of the second-hop relay channel to itself , all belonging to the set After the source replies to the RTS packet in sequence, the destination obtains the set The signal-to-noise ratio of the two-hop link with all source nodes as relays is calculated to obtain the source In the collection The maximum channel received signal-to-noise ratio for transmission with the assistance of the best relay node within , the corresponding best relay node is , go to step 27; Step 27: If , it is determined that the access benefit is greater than the abandonment benefit, and further access channel selection is performed, and the process goes to step 28; otherwise, the access opportunity is abandoned and competition is restarted, and the process returns to step 22; Step 28: If , then the source Here I am time at the maximum achievable rate in a direct channel Transmission, after the transmission is completed, return to step 22; otherwise, the source is the best relay in the alliance Assisted at the maximum achievable rate Two-stage transmission is performed, and the transmission time is , after the transmission is completed, return to step 22; Step 29: If the direct channel signal-to-noise ratio , then select the direct channel for channel access, the destination Send CTS to the source and all other sources, exist time, at the maximum achievable rate Data transmission is carried out on the direct channel, and all other sources are Wait for a certain time, and return to step 22 after a single transmission is completed; otherwise, the destination Abandon this access opportunity and broadcast the CTS packet to all source nodes. All source nodes restart channel competition in the next time slot and return to step 22.

6. The optimal selective relay sensing access method according to claim 5, characterized in that: The two-stage transmission includes: In the first stage, the source Broadcast data to its destination and all potential relay nodes; In the second phase, the best single relay node The received signal is forwarded to the destination, which receives two signals, one from the direct link and the other from the relay channel.

7. The optimal selective relay-aware access method according to claim 5, characterized in that: System average throughput It is expressed by the following formula: Where: represents the benefit of direct channel access, 0 represents the expected benefit of giving up access, express The profit function of detecting potential relays when .

8. The optimal selective relay-aware access method according to claim 7, characterized in that: The first-level decision threshold The definition is as follows: For each fixed communication pair , the maximum profit function for detecting potential relays for A monotonically increasing function of For the equation The only solution, For the equation The only solution of Second-level judgment threshold The definition is as follows: For each fixed communication pair , the profit difference function of detecting potential relays for A monotonically increasing function of For the equation The only solution of .

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