A cooperative channel access method

Abstract

The application discloses a kind of cooperative channel access methods, consider that multiple untrusted relay nodes exist simultaneously, and the case of adopting non-collusion way eavesdropping source channel, in combination with cooperative interference mechanism, specifically designed safe channel access method.Based on the rational cooperation principle between user pairs, the communication nodes located in the same alliance can simultaneously act as the relay nodes of the other party, increasing the role diversity, and the same user pair can simultaneously join multiple alliances, fully utilizing the spatial and temporal diversity and relay diversity gain.For the overlapping alliance structure, in addition to detecting untrusted relays, further detection of alliance trusted relays is added, and by comparing the expected return functions of detecting different numbers of relay nodes, the optimal detection node and detection set are selected, to the greatest extent avoiding unnecessary detection overhead.

Description

Technical Field

[0001] This invention relates to the field of wireless communication technology, and in particular to a cooperative channel access method for mobile ad-hoc networks based on dynamic alliance cooperative grouping. Background Technology

[0002] In cooperative channel opportunity scheduling in distributed networks, our research group has successively studied channel-aware access modeling and statistical optimization methods under two relay point operating modes: controlled and autonomous. Specifically, based on stopping optimization theory, we proposed a method for full-awareness and access statistical decision-making for relay channels under controlled relay resource mode. Addressing the issue of linearly increasing relay channel awareness overhead with the number of relay points in controlled mode, we conducted research on a fully distributed channel-aware access method under autonomous relay resource mode. We proposed a mathematical modeling method based on a two-order stopping optimization method and established a fully distributed statistical decision-making optimization method for user channel contention awareness and forward-hop broadcasting—multi-relay point distributed awareness and backward-hop forwarding, achieving statistical optimization of network throughput. However, for scenarios with untrusted relays, existing research is still in its early stages. Among published papers, one first combined sink-assisted cooperative interference with multi-user pair cooperative channel opportunity scheduling for a scenario with one untrusted relay, proposing a secure channel opportunity scheduling method. However, this method did not address scenarios with multiple untrusted relays and did not consider mutual cooperation between user pairs, resulting in insufficient utilization of multi-relay cooperation gains.

[0003] It is evident that existing cooperative channel access opportunity scheduling methods have the following five shortcomings:

[0004] 1. The research did not consider the users' willingness to cooperate. Studies that consider mutual cooperation are conducted under the assumption that all users are willing to cooperate. Studies that do not consider cooperation assume that all users do not cooperate. The research lacks analysis of users' motivation to cooperate, and the cooperation mechanism is inflexible and lacks scenario adaptability.

[0005] 2. The secure transmission under multiple untrusted relays is not considered. When multiple untrusted relays eavesdrop on the channel in a non-collusive manner, other physical layer secure transmission methods are required to curb the eavesdropping of the network by untrusted relays.

[0006] 3. The impact of network mobility on the cooperative relationship between user pairs was not considered. When the cooperative benefits of user pairs are linked to the access transmission benefits, the cooperative relationship between user pairs is highly correlated with the network topology location. The cooperative relationship of mobile networks should take into account the dynamic characteristics.

[0007] 4. The case where a user pair can participate in multiple cooperative groups is not considered. When a user pair is limited to participating in only one alliance, the improvement of network benefits from cooperation is also limited, and the cooperative relay diversity gain cannot be maximized.

[0008] 5. The formation rules of distributed alliance structures are complex, requiring multiple iterations to achieve stability, resulting in high computational complexity and long iteration time. Summary of the Invention

[0009] In view of the above problems, the present invention provides a cooperative channel access method for overcoming or at least partially solving the above problems.

[0010] This invention provides the following solution:

[0011] A cooperative channel access method includes:

[0012] For the Each location synchronization period determines the set of user pairs sharing the current channel. and untrusted relay sets ;

[0013] All nodes set backoff time windows based on node IDs and broadcast location data packets sequentially according to an adaptive mechanism;

[0014] Initialize an overlapable alliance structure ;

[0015] Calculate the system's average safe throughput and the individual utility of each user pair ;

[0016] For each user Each user and ,like Then calculate as well as ,renew ; This represents the set of all user pairs who have evaluated whether to establish a collaborative link;

[0017] If the conditions for establishing cooperation are met by using the alliance formation rules, then update... Until all users have no intention to cooperate, a stable, overlapping alliance structure is reached. ;

[0018] Based on a given stable alliance structure Calculate and obtain the first-level decision threshold vector System average safe throughput and category sets ;

[0019] All users compete, decide, and access the system according to the distributed optimal channel security opportunistic access method;

[0020] If the network changes dynamically after the current synchronization cycle ends, the user pair set will be updated, and the next round of distance perception will continue.

[0021] Preferably, the adaptive mechanism includes:

[0022] Set the backoff time window length for node contention channel based on node ID;

[0023] The user determined that a channel was detected in one If the time slot is idle, then after its backoff time ends, it will be determined by probability. Send data packets;

[0024] If a collision occurs, the backoff time is reset after the collision ends, and a probability is applied after the second round of backoff time. Send data packets until the location information data packets for all nodes have been sent.

[0025] Preferably: the backoff time window length of the set node contention channel includes: if there are One user pair, i.e. The nth node, then the nth The backoff time for each node is .

[0026] Preferably: Initialize an overlapable alliance structure This includes: at the beginning of the alliance's formation, assuming that all user pairs do not cooperate, then... .

[0027] Preferably: Calculate the individual utility for each user pair include:

[0028] For users Given an overlapable alliance structure Below, based on the optimal channel opportunistic access method, the user's expected benefit from access is the amount of securely transmitted data. The expected time cost is Then its individual utility function is:

[0029]

[0030] In the formula: This indicates the probability that the user will succeed in competing for the channel. and These represent the categories to which the corresponding channels belong after successful contention. , , User's expected revenue This represents the average safe throughput of the optimal system. This represents the average probability that a winning user in the network will choose not to access the channel after successfully contending for it. Indicates condition, Indicates the channel coherence time. This represents the average time of a single observation. Indicates the detection time. Indicates the optimal number of trusted relay detection nodes. and the corresponding payoff function, This indicates the maximum eavesdropping rate.

[0031] Preferably: the average probability that a winning user pair in the network chooses not to access the channel after successfully contending for the channel. , represented as:

[0032]

[0033] In the formula: This represents the probability of abandoning access in the secondary decision-making stage. The probability of detecting a trusted relay in the alliance during the second-level decision-making process. This represents the probability of abandoning access in the three-level decision-making process. Indicates the direct channel SNR The probability distribution function.

[0034] Preferably: First-level decision threshold vector Represented as:

[0035] For users Define the optimal decision first-level threshold vector. ,in Equation , and The only solution.

[0036] Preferably, the alliance formation rules include:

[0037] Given a union structure ,have If regarding alliance structure It meets the following conditions:

[0038] Condition one: ,

[0039] Condition two: .

[0040] Then the user's With users Establishing a partnership, users Join the alliance Users Join the alliance ;

[0041] Given a union structure ,have If regarding alliance structure It meets the following conditions:

[0042] Condition one: , ;

[0043] Condition two: .

[0044] Then the user's With users Breaking the partnership, users Leave the league Users Leave the league .

[0045] Preferably: for a given set of user pairs and untrusted relay sets When the topology of all nodes remains unchanged, the establishment or breaking of cooperation is irreversible.

[0046] According to specific embodiments provided by the present invention, the present invention discloses the following technical effects:

[0047] This application provides a cooperative channel access method that considers the scenario where multiple untrusted relay nodes coexist and eavesdrop on the source channel using a non-collusive method. Combining a cooperative interference mechanism, a secure channel access method is specifically designed. Based on the principle of rational cooperation between user pairs, communication nodes within the same alliance can simultaneously act as relay nodes for each other, increasing role diversity. Furthermore, the same user pair can join multiple alliances simultaneously, fully utilizing spatiotemporal diversity and relay diversity gain. For overlapping alliance structures, in addition to detecting untrusted relays, further detection of trusted relays within the alliance is added. By comparing the expected reward functions of detecting different numbers of relay nodes, the optimal detection nodes and detection set are selected, minimizing unnecessary detection overhead. For a given network topology, to achieve a stable overlapping alliance structure, a rule for establishing / breaking cooperative alliances is proposed. This rule possesses irreversible properties; when the topology remains unchanged, two user pairs that have established a cooperative relationship will not break that relationship, and vice versa, avoiding repeated calculations and iterations. Based on the alliance formation rule, a single-convergence dynamic alliance formation method is designed. All user pairs start from a single alliance that does not cooperate, and after one round of evaluation on whether to establish a cooperative relationship, they converge to a stable overlapping alliance structure. Taking the user pair's movement cycle as the unit, a three-stage dynamic distributed optimal cooperative channel security access method is proposed, consisting of node distance awareness, dynamic overlapping alliance formation, and optimal channel security opportunistic access. This method can continuously maintain optimal security access performance when the network dynamically changes.

[0048] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0049] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly described below. Obviously, the drawings described below are merely some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0050] Figure 1 This is a flowchart of a cooperative channel access method provided in an embodiment of the present invention;

[0051] Figure 2 This is a diagram of an overlapping alliance cooperative network model for untrusted relay eavesdropping provided in an embodiment of the present invention;

[0052] Figure 3 This is a schematic diagram of a stable alliance structure under the initial topology provided in an embodiment of the present invention;

[0053] Figure 4This is a schematic diagram illustrating the change in the stable alliance structure after node movement, provided in an embodiment of the present invention.

[0054] Figure 5 This is a comparison chart of the impact of dynamic alliance formation on network performance provided in an embodiment of the present invention;

[0055] Figure 6 This is a performance comparison chart of game strategies under different coherence times provided in the embodiments of the present invention. Detailed Implementation

[0056] 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 a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0057] See Figure 1 This invention provides a cooperative channel access method, such as... Figure 1 As shown, the method may include:

[0058] For the Each location synchronization period determines the set of user pairs sharing the current channel. and untrusted relay sets ;

[0059] All nodes set a backoff time window based on the node ID and broadcast location data packets sequentially according to an adaptive mechanism; in specific implementations, embodiments of this application can provide setting the backoff time window length for node contention of the channel based on the node ID;

[0060] The user determined that a channel was detected in one If the time slot is idle, then after its backoff time ends, it will be determined by probability. Send data packets;

[0061] If a collision occurs, the backoff time is reset after the collision ends, and a probability is applied after the second round of backoff time. Send data packets until the location information data packets for all nodes have been sent.

[0062] The backoff time window length of the set node contention channel includes: if there is One user pair, i.e. The nth node, then the nth The backoff time for each node is .

[0063] Initialize an overlapable alliance structure In practice, the overlapping alliance structure is initialized. This includes: at the beginning of the alliance's formation, assuming that all user pairs do not cooperate, then... , This represents the set of all user pairs who have evaluated whether to establish a collaborative link.

[0064] Calculate the system's average safe throughput and the individual utility of each user pair ;

[0065] For each user and ,like Then calculate as well as ,renew ;

[0066] In specific implementation, embodiments of this application can provide calculation of the individual utility of each user pair. include:

[0067] For users Given an overlapable alliance structure Below, based on the optimal channel opportunistic access method, the user's expected benefit from access is the amount of securely transmitted data. The expected time cost is Then its individual utility function is:

[0068]

[0069] In the formula: This indicates the probability that the user will succeed in competing for the channel. and These represent the categories to which the corresponding channels belong after successful contention. , , User's expected revenue This represents the average safe throughput of the optimal system. This represents the average probability that a winning user in the network will choose not to access the channel after successfully contending for it. Indicates condition, Indicates the channel coherence time. This represents the average time of a single observation. Indicates the detection time. Indicates the optimal number of trusted relay detection nodes. and the corresponding payoff function, This represents the maximum eavesdropping rate. The average probability that a winning user pair in the network will choose not to access the channel after successfully contending for it. , is represented as:

[0070]

[0071] In the formula: This represents the probability of abandoning access in the secondary decision-making stage. The probability of detecting a trusted relay in the alliance during the second-level decision-making process. This represents the probability of abandoning access in the three-level decision-making process. Indicates the direct channel SNR The probability distribution function.

[0072] If the conditions for establishing cooperation are met by using the alliance formation rules, then update... Until all users have no intention to cooperate, a stable, overlapping alliance structure is reached. In specific implementation, the alliance formation rules in this application embodiment may include:

[0073] Given a union structure ,have If regarding alliance structure It meets the following conditions:

[0074] Condition one: ,

[0075] Condition two: .

[0076] Then the user's With users Establishing a partnership, users Join the alliance Users Join the alliance ;

[0077] Given a union structure ,have If regarding alliance structure It meets the following conditions:

[0078] Condition one: , ;

[0079] Condition two: .

[0080] Then the user's With users Breaking the partnership, users Leave the league Users Leave the league .

[0081] Based on a given stable alliance structure Calculate and obtain the first-level decision threshold vector System average safe throughput and category sets In specific implementation, embodiments of this application may provide a first-level decision threshold vector. Represented as:

[0082] For users Define the optimal decision first-level threshold vector. ,in Equation , and The only solution.

[0083] All users compete, decide, and access the system according to the distributed optimal channel security opportunistic access method;

[0084] If the network changes dynamically after the current synchronization cycle ends, the user pair set will be updated, and the next round of distance perception will continue.

[0085] The cooperative channel access method provided in this application addresses secure cooperative transmission communication scenarios with multiple untrusted relays. To further enhance the flexibility and efficiency of cooperative transmission, and as a comprehensive combination, optimization, and improvement of existing research techniques, this invention proposes a mobile ad-hoc network cooperative channel access method based on dynamic alliance cooperative grouping in scenarios with multiple untrusted relays, based on the theory of overlapping alliances. This method allows a single user pair to participate in multiple alliances. Specifically, the technical approach involves: first, designing a distributed optimal channel security opportunity access multi-level decision-making method under a static overlapping alliance structure; then analyzing the mapping relationship between the individual payoff function of each user pair and the average network security throughput under this multi-level decision-making method; next, proposing a distributed overlapping alliance game algorithm based on maximizing the individual payoff of the user pair and the overall network payoff to obtain a stable overlapping alliance structure; finally, based on this overlapping alliance structure, obtaining an optimal distributed channel security opportunity access method suitable for the current network topology. Compared with existing secure access algorithms, simulations verify the system average security throughput performance of the proposed method.

[0086] The method provided in the embodiments of the present invention will be described in detail below, and its effectiveness will be verified.

[0087] For secure cooperative transmission communication scenarios with multiple untrusted relays, a cooperative channel access method for mobile ad-hoc networks based on dynamic confederation cooperative grouping is proposed. First, a multi-level decision-making method for distributed optimal channel security opportunity access under a static overlapping confederation structure is designed. Then, the mapping relationship between the individual payoff function of each user pair and the average secure throughput of the network under this multi-level decision-making method is analyzed. Next, a distributed overlapping confederation game algorithm based on maximizing the individual payoff of user pairs and the overall network payoff is proposed to obtain a stable overlapping confederation structure. Finally, based on this overlapping confederation structure, an optimal distributed channel security opportunity access method suitable for the current network topology is obtained.

[0088] The overlapping cooperative network model for untrusted relay eavesdropping considered in this invention is as follows: Figure 2 The diagram illustrates a multi-user pair network with multiple untrusted relays. Consider a network consisting of... A source-destination user communication pair and A wireless cooperative communication network consisting of several untrusted relays, each composed of a set of... and set It means that among them and They represent the first The source and destination of a communication pair.

[0089] To avoid ambiguity, in the following description of this invention, the communication pair Equivalent to All nodes are equipped with a single antenna and operate in half-duplex mode, with relays using half-duplex AF mode. All user pairs share the same channel in a contention-based manner. User pairs can cooperate and communicate by forming overlapping alliances, acting as trusted relays to each other. Dedicated untrusted relays are shared by all users, do not participate in alliance formation, but continuously and passively eavesdrop on the winning source, making them an indispensable factor in alliance formation and secure access method design. For the user pair set... An overlapping alliance structure is represented as , This represents a single alliance, where users may overlap between alliances, meaning the same user pair can join multiple alliances. Considering the complexity of overlapping alliance structures, to clearly represent the available relay set for each user pair, another representation of overlapping alliance structures is defined, namely... ,in Indicates user's opinion The set of all trusted relay nodes is represented as: .

[0090] Rayleigh fading is used to model the wireless channel. From the source... To their lodging The direct-connect channel SNR is represented as ,in express and The straight-line distance between them For channel fading depth, The fading parameters are small-scale and follow the mean value. If the negative exponential random distribution is followed, then Follow the mean The negative exponential random distribution. For non-directly connected links, the nodes... The channel SNR between them is expressed as:

[0091] in, Represents a node and nodes The distance between them The fading parameters are small-scale and follow the mean value. If the negative exponential random distribution is followed, then Follow the mean The negative exponential random distribution, The probability distribution function is , The probability distribution function is The method proposed in this invention is applicable to typical wireless channels such as Ricean channels and Nakagami channels. It is assumed that all wireless channels possess symmetry, i.e. The channel coherence time is .

[0092] based on Figure 2 The network model shown, under a given overlapping alliance structure Under these circumstances, multiple users follow Algorithm 1 to achieve distributed secure channel access.

[0093] Algorithm 1: Distributed Optimal Channel Security Opportunity Access Method

[0094] enter: , , , , , , , ;

[0095] In each micro-time slot Initially, all information sources are given probabilities. Send a contention-based RTS;

[0096] For the This was the second successful channel contention. Victory Obtain the instantaneous SNR of the direct channel To make the first-level decision;

[0097] If the user Then further judgment is needed; if ,but Select the DT access mechanism and send CTS. Then at the maximum achievable rate Access to direct channel, duration .

[0098] Otherwise, the user Then, further judgment is made if... ,but Abandon access and send CTS, then compete again in the next time slot.

[0099] if ,but Select the DT access mechanism and send CTS. Then at the maximum achievable rate Access to direct channel, duration .

[0100] otherwise, Select to detect all untrusted relays and send CTS. An untrusted relay then sequentially replies with RTS, detection time back, Obtain the cooperative two-hop link SNRs of untrusted relays:

[0101]

[0102] The secure transmission rate of DT access can be calculated. Secure transmission rate of CJ access mechanism with untrusted relay assistance ,make Make a second-level decision;

[0103] If the user , then, if ,but The decision was made to stop and send CTS;

[0104] if ,but Choose the DT access mechanism After receiving CTS, at the maximum achievable rate Access to direct channel, duration .

[0105] otherwise, Choose CJ access mechanism After receiving CTS, at the maximum achievable rate Access channel, duration .forward Within a time period, and Broadcast data and jamming signals separately, then Time, unreliable relay Towards It amplifies and forwards the data packets it receives.

[0106] otherwise The user relinquishes access and sends a CTS message, then competes again in the next time slot. Then calculate the optimal number of trusted relay detection nodes. traversal Calculate the difference function ,like ,but End the traversal.

[0107] otherwise, .calculate ;

[0108] if ,but Select Stop and Send CTS;

[0109] if ,but Choose the DT access mechanism After receiving CTS, at the maximum achievable rate Access to direct channel, duration .

[0110] otherwise, Choose CJ access mechanism After receiving CTS, at the maximum achievable rate Access channel, duration .forward Within a time period, and Broadcast data and jamming signals separately, then Time, unreliable relay Towards It amplifies and forwards the data packets it receives.

[0111] if ,but Abandon access and send CTS, then compete again in the next time slot.

[0112] otherwise Select Detection Each alliance trusted relay sends CTS, and the set The trusted relays within then sequentially reply with RTS, and the detection time... back, Obtain the cooperative two-hop link SNRs of trusted relays:

[0113]

[0114] Calculate the secure transmission rate of the CJ access mechanism with trusted relay assistance. Then, make a third-level decision.

[0115] if ,but Select Stop and Send CTS;

[0116] if ,but Select DT access After receiving CTS, at the maximum achievable rate Access to direct channel, duration .

[0117] otherwise, Choose CJ access mechanism After receiving CTS, at the maximum achievable rate Access channel, duration .forward Within a time period, and Broadcast data packets and interference separately, then Time, Unreliable / Reliable Relay Towards It amplifies and forwards the data packets it receives.

[0118] otherwise, Abandon access and send CTS, then compete again in the next time slot.

[0119] After the single access ends, continue to the next... This was the first successful channel contention.

[0120] The successful channel contention described in Algorithm 1 is specifically as follows: At the beginning of each contention micro-slot, all sources independently transmit channel contention RTS packets with equal probability p0. A source is considered the winning source if and only if, in the same micro-slot, only one source transmits an RTS packet, and this channel contention is considered successful. Since each channel contention is independent, the average time until a source succeeds in each contention is:

[0121]

[0122] in Indicates the time of RTS packet transmission. Indicates the time of CTS packet transmission. This indicates the number of source-destination pairs. Indicates the duration of an idle time slot; the time when a conflict occurs can be used. express.

[0123] The DT (Direct Connection) access mechanism described in Algorithm 1 is specifically described as follows: For the information source... It transmits signals to the destination via a direct link. The secure transmission rate under direct channel transmission is:

[0124]

[0125] in For the achievable transmission rate of a direct link, To achieve the maximum eavesdropping rate, let This indicates the maximum snooping SNR of an untrusted relay.

[0126] The CJ (Cooperative Interference) access mechanism described in step 14 of Algorithm 1 is specifically described as follows: Source Choose to use cooperative interference in relays With assistance, equal-length two-stage data transmission is performed. The safe transmission rate for cooperative interference transmission is:

[0127]

[0128] in, This refers to the relay transmission rate.

[0129] This represents the maximum eavesdropping rate.

[0130] For the optional relay set Select relay node As the best relay, the maximum secure transmission rate and its corresponding achievable transmission rate and SNR They can be represented as:

[0131]

[0132] As described in Algorithm 1, the optimal number of trusted relay probe nodes is calculated. Specifically, it is described as follows: Regarding the selection of the number of detection relays... The corresponding set of detection relays For the trusted relay set of the alliance Mean SNR of internal trunk links The largest A set of trusted relays in a federation.

[0133] For detection Trusted relay and detection alliance The difference function for J trusted relays in a federation, and the payoff function for detecting J relays are:

[0134]

[0135] in, The optimal number of trusted relay detection nodes and the corresponding profit function for:

[0136]

[0137] The input parameters described in Algorithm 1 Its specific description is as follows: For a given set of user pairs... Untrusted relay set Overlapping Alliance Structure Optimal system average safe throughput The unique solution is to satisfy the following equation.

[0138]

[0139] in, To detect the payoff function of all untrusted relays ,for Non-single users , ;for Single users , .

[0140] The input parameters described in Algorithm 1 Its specific description is as follows. Regarding user feedback... Define the optimal decision first-level threshold vector. ,in Equation , and The only solution. Note that if Does not exist The solution is then let . This is the revenue function for direct channel access.

[0141] The input parameters described in Algorithm 1 , , Its specific description is as follows: For a given set of user pairs... Untrusted relay set Overlapping Alliance Structure Users They can be classified as follows.

[0142] for For single users, if ;

[0143] Then the user's Belongs to a category set ;

[0144] Otherwise, the user Belongs to a category set ;

[0145] for Alliance users It belongs to the category set .

[0146] Based on the above-mentioned optimal secure channel opportunity access method under the given overlapping alliance structure, and considering node movement, this invention proposes the following distributed optimal channel secure opportunity access method based on dynamic overlapping formation game.

[0147] Algorithm 2: Distributed optimal channel security opportunity access method based on dynamic overlapping alliance formation game.

[0148] For the Each location synchronization period, inputting the set of user pairs sharing the current channel. and untrusted relay sets ;

[0149] During the distance awareness phase, all nodes set backoff time windows based on their IDs and broadcast location data packets sequentially according to an adaptive mechanism.

[0150] Alliance formation phase, initialization ;

[0151] Average secure throughput of computing systems Calculate the individual utility for each user pair. ;

[0152] For each user For each user and ,like Then calculate , ,renew ;

[0153] If the conditions for establishing cooperation are met, then update. Until all users have no intention of cooperating, a stable, overlapping alliance structure is achieved. .

[0154] Based on the optimal DCOS phase of the consortium, and based on a given stable consortium structure. Calculate the first-level decision threshold vector and system average safe throughput Determine the classification set .

[0155] All users compete for access using the distributed optimal channel security opportunistic access method shown in Algorithm 1.

[0156] If the network changes dynamically after the current synchronization cycle ends, the user pair set will be updated, and the next round of distance perception will continue.

[0157] The adaptive mechanism described in Algorithm 2 is specifically as follows: First, based on the node ID, the backoff time window length for node contention channels is set. For example, if there are... One user pair, i.e. The nth node, then the nth The backoff time for each node is Once a user detects that a channel is in a... If the time slot is idle, then after its backoff time ends, it will be determined by probability. If a collision occurs while sending data packets, the backoff time is reset after the collision ends, and a probability is applied after the second round of backoff time. Send data packets, and so on, until all location information data packets for all nodes have been sent.

[0158] Algorithm 2's initialization Specifically, it is described as follows: At the beginning of the alliance, it is assumed that all user pairs do not cooperate. This represents the set of all user pairs who have evaluated whether to establish a collaborative link.

[0159] The calculation of individual utility for each user pair described in step 7 of Algorithm 2 Specifically, it is described as follows: Regarding user feedback... Given an overlapable alliance structure Below, based on the optimal channel opportunity access method of Algorithm 1, the user's expected benefit from access is the amount of securely transmitted data. The expected time cost is Since only one user pair accesses the channel at a time, the time cost for all user pairs is... They are the same. Therefore, their individual utility function is:

[0160]

[0161] The probability that the user succeeds in competing for the channel is expressed as:

[0162]

[0163] and Each corresponds to a category set after successful channel contention. , , The user's expected benefit, i.e., the amount of securely transmitted data, can be expressed as:

[0164]

[0165] Let be the average probability that a winning user pair in the network chooses not to access the channel after successfully contending for it, expressed as:

[0166]

[0167] in, The probability of abandoning access in the secondary decision-making process, event It can be represented as:

[0168]

[0169] For the probability of detecting trusted relays in a secondary decision-making process, the event... It can be represented as:

[0170]

[0171] The probability of abandoning access in the three-level decision-making process, event It can be represented as:

[0172]

[0173] The alliance formation rules in the alliance formation phase described in Algorithm 2 include two types: establishment and breaking, which are described in detail below.

[0174] Establishment: Given a union structure ,have If regarding alliance structure It meets the following conditions.

[0175] Condition one: ,

[0176] Condition two: .

[0177] Then the user's With users Establishing a cooperative relationship, that is, users to Join the alliance Users Join the alliance Breaking: Given a coalition structure ,have If regarding alliance structure It meets the following conditions:

[0178] Condition one: , ;

[0179] Condition two: .

[0180] Then the user's With users Breaking the partnership, that is, the user's... Leave the league Users Leave the league .

[0181] The aforementioned alliance formation rules have the following properties: for a given set of user pairs and untrusted relay sets When the topology of all nodes remains unchanged, the establishment / breaking of cooperation is irreversible. That is, once two nodes establish cooperation, they will not be broken, and vice versa.

[0182] Proof: Based on the user's perception of individual utility From the definition, we can obtain that for the average throughput of an individual, all users share the same Users who establish / break partnerships The increase in revenue comes from This refers to the improvement in its own transmission quality; at this time, users who do not participate in establishing / breaking cooperation... This results in reduced revenue, which is due to the contention nature of the channel. An increased access probability for individual user pairs leads to a decreased access probability for other user pairs within the same timeframe, increasing the time cost of a single access attempt, equivalent to... Unchanged but As the alliance structure changes, the benefits decrease. Therefore, during the alliance formation process, each change in the alliance structure will result in an increase in benefits for users whose cooperative relationships have changed, while the benefits for other users will decrease by the same proportion.

[0183] First, we analyze the reversibility of establishing cooperative operations, specifically regarding the user's... Once they establish cooperation, it will affect the current alliance structure. and , This makes users more aware of The average secure throughput gains for each individual do not decrease, and at least one party's gains increase. Clearly, when other alliance structures remain unchanged, this cooperation is irreversible; when, except for user... In addition, after the cooperative relationships of other nodes change, the alliance structure becomes Users The average secure throughput per individual decreases proportionally, but users' expectations are lower. Bring and The incremental gains still exist, and regardless of how the alliance structure iterates, the system's average secure throughput will never decrease. Therefore, breaking the alliance structure... and cooperative alliance structure Users Cooperation can still yield greater individual utility; the three conditions in Definition 6.4 are still met; and users' [utility / interest]... The cooperative relationship will not be broken. Therefore, in the distributed cooperative channel security opportunistic access scenario based on overlapping alliances presented in this chapter, establishing cooperation is irreversible. Similarly, breaking cooperation is also irreversible. Q.E.D.

[0184] This invention has undergone rigorous simulation testing, and related numerical simulations were performed in MATLAB to analyze and evaluate the network performance. Consider a 5km × 5km square map, within which 12 source-sink communication pairs are randomly deployed. Referring to common wireless communication scenarios, the channel fading depth is set to... .

[0185] For nodes The statistical parameters for the relay channel and the direct channel are set as follows: The unit is dB, meaning that for the same wireless transmission distance, the SNR of a relay channel is higher than that of a direct channel. dB facilitates the establishment of cooperative relationships among users, promotes the formation of alliances, and allows simulation analysis results to more intuitively reflect the performance of the proposed method. Referring to the simulation parameter settings in 3.5, the coherence time for maintaining the channel state unchanged under quasi-static fading is... The duration of an idle micro-slot is The transmission duration for RTS and CTS is During the alliance formation phase, the channel contention probability is... .

[0186] First, the stability and reliability of the proposed distributed, overlapping federated game algorithm are verified. When , hour, Figure 3The topology of randomly generated node locations and the corresponding stable alliance structure are presented. This structure converges to stability after only one round of establishing cooperation, verifying the irreversibility of the proposed establishment / breaking rules, making the overlapping alliance formation algorithm easier to converge. Figure 3 As can be seen, the formation of alliances and cooperative relationships basically follows the principle of proximity, for example... Some users form only one alliance, for example, users to Some users participate in multiple alliances, for example, users on... The remaining users choose not to cooperate, for example, users who... Specifically, users 3 and 4 simultaneously establish cooperative relationships with user 7, but they do not cooperate with each other; users 1 and 2 simultaneously form alliances. and But users are The fact that 11 and 12 do not cooperate with each other reflects the flexible reuse characteristics of overlapping alliances compared to non-overlapping alliances, which can make full use of the cooperation between users to improve the overall transmission performance of the network.

[0187] Further considering the mobility characteristics of network nodes, Figure 3 The node topology shown is the initial position (0th move). Eight random node moves are performed, each moving a random distance between 0 and 0.5m above and below the horizontal and vertical coordinates, respectively. These random values ​​are generated by the rand function and follow a uniform distribution. If a node's position exceeds the map's boundaries, its coordinates are set to the map's maximum / minimum value minus / plus 0.1. For example, for updating coordinate points... , Let them be equal to respectively , To adapt to the simulated map area.

[0188] Figure 4 The stable alliance structure after the 1st to 4th node moves is given, from Figure 4 As can be seen, when a node's position changes, its alliance and cooperation relationships may change. For example, from the first move to the second move, the user's... The alliance relationship of user 8 remains unchanged, while the alliance relationships of other user pairs have changed, and user pair 8 has changed from a single alliance to a non-single alliance.

[0189] Furthermore, to further verify the adaptability of the proposed alliance formation algorithm to dynamic mobile network topology changes, Figure 5A line graph comparing network performance under single-member alliances and stable alliance structures is presented, starting from the initial state and after each node movement. Because node movements are random, the network channel state changes randomly, resulting in an irregular line graph showing network throughput performance with increasing number of movements. Specifically, for each iteration, the initial alliance structure is an all-single alliance. After the alliance converges to stability, as described in Algorithm 1, all user pairs are... The performance under contention channel conditions corresponds to the "stable alliance structure" curve. As can be seen from the figure, compared with an all-single alliance structure, the stable alliance structure formed by establishing cooperative relationships can improve the average secure throughput of the system by 45%-85%, verifying the effectiveness of the proposed method.

[0190] Table 1 Stable Alliance Structures under Different Network Parameter Settings

[0191]

[0192] Finally, to further verify the performance of the proposed method compared with other game strategies, the average safe throughput of the system under the proposed overlapping coalition strategy and other coalition game strategies is compared. Figure 6 Performance comparison curves for four strategies under two configurations are presented. The proposed strategies refer to: a stable alliance where all user pairs compete with equal probability, and secure channel access is achieved according to Algorithm 1; a non-overlapping alliance where a user pair can only join one alliance, converging to stability under alliance switching rules, and then achieving three-level optimal secure channel access based on the stable alliance structure as shown in Algorithm 1; a single alliance where all user pairs do not cooperate and can only access the channel through direct connections or untrusted relays; and a large alliance where all user pairs form a large alliance and can act as relays for each other.

[0193] Figure 5 When , The curves showing the change in the system's average secure throughput of the proposed original strategy and the four comparative strategies as the time varies from 1ms to 5ms. The solid line represents... In this case, the dashed line represents... The situation. From Figure 5 As can be seen, the difference between the relay channel SNR and the direct channel SNR is... The larger the value, the greater the performance difference between different comparison strategies. At this point, the performance of the proposed strategy, the large alliance strategy, and the non-overlapping alliance strategy are very similar. The performance difference in secure transmission between relay links and direct links is small, and the performance gain from alliance cooperation is not significant, resulting in a small performance gap between different cooperation methods. However, compared to the single alliance strategy, the cooperative alliance strategy's improvement in the system's average secure throughput is not negligible. Compared with the single-alliance strategy, the cooperative alliance strategy can significantly improve the secure transmission performance of the system. The performance improvement of the non-overlapping alliance strategy comes from the improvement of alliance cooperation from 0 to 1. Compared with the non-overlapping alliance strategy, the performance improvement of the proposed strategy comes from the reusability of the node alliance, which further improves the relay diversity gain.

[0194] when At that time, the average security throughput performance of the proposed strategy remained basically equal to that of the large alliance strategy. When the size is small, the proposed strategy performs slightly better. When the size is large, the performance of the major league strategy is slightly better. At that time, the performance of the two strategies was basically the same. It can be concluded that the proposed optimal channel security opportunity access method based on overlapping alliances takes rational cooperation between user pairs as its starting point, maximizes the utilization of multi-relay diversity gain of user pairs as relays, maximizes the average security throughput of the system, and can achieve network performance close to that of the ideal large alliance strategy, realizing a win-win situation for individual user benefits and overall network benefits.

[0195] As can be seen, the cooperative channel access method provided in this application studies the distributed channel security opportunity scheduling problem for reusable alliance user nodes in a wireless cooperative transmission network with multiple user pairs and untrusted relays. The rational cooperative secure access between user pairs is modeled as an optimal channel security opportunity access problem based on an overlapping alliance formation game.

[0196] For a given overlapping alliance structure, with the goal of maximizing the average secure throughput of the system, a distributed optimal channel security opportunistic access algorithm based on the alliance structure with three-level stopping is designed; it makes full use of the eavesdropping-transmission duality of untrusted relays and the rational cooperative gain of trusted alliance relays.

[0197] Based on this distributed optimal channel security opportunistic access algorithm, the individual utility function of each user pair under this method is defined as the expected average secure throughput of the user pair, and the expression of the individual utility function is derived to quantify the rational cooperation motivation of the user pair.

[0198] Based on the individual utility function of users, an irreversible alliance establishment / breaking rule is proposed. When the topology remains unchanged, two user pairs that establish a cooperative relationship will not break the cooperative relationship, and vice versa. Based on this alliance formation rule, a dynamic overlapping alliance formation algorithm is designed, which enables user pairs to form alliances in a distributed manner and converge to a stable alliance structure after one round of iteration, without the need for multiple repeated iterations.

[0199] For the proposed dynamic overlapping alliance formation algorithm, a history set is defined. After each user pair evaluates whether it wants to establish a cooperative relationship with another user pair, regardless of whether the cooperative relationship is established, the link between the two user pairs is added to the history set. For subsequent alliance relationship establishment of user pairs, it is first determined whether it belongs to the history set. If it does, it means that the evaluation of establishing a cooperative relationship has been carried out, and there is no need to calculate it again.

[0200] For dynamic mobile networks, an adaptive backoff broadcast algorithm based on node ID is designed. This algorithm correlates the backoff time with the channel conditions of user pairs, allowing users with better channel conditions to access the channel first. User pairs with different channel conditions have different backoff times, thus preventing broadcast packet collisions. For a very small number of user pairs with essentially equal channel conditions, when a broadcast packet collision occurs, the user pairs dynamically adjust their contention probabilities to reduce the probability of collisions in the next contention. Under this method, all user pairs can achieve network-wide location information synchronization with a relatively short time overhead.

[0201] By combining overlapping alliance game theory, optimal access theory, and sink-assisted cooperative interference mechanism, a dynamic distributed optimal cooperative channel security access method with three stages—node distance awareness, dynamic overlapping alliance formation, and optimal channel security opportunistic access—is proposed. This method has good adaptability to mobile networks and can always maintain the optimal overlapping alliance structure under dynamic changes in network topology, thereby achieving the optimal system security transmission throughput.

[0202] In summary, the cooperative channel access method provided in this application considers the simultaneous existence of multiple untrusted relay nodes and the use of non-collusive methods to eavesdrop on the source channel. Combined with a cooperative interference mechanism, a secure channel access method is specifically designed. Based on the principle of rational cooperation between user pairs, communication nodes within the same alliance can simultaneously act as relay nodes for each other, increasing role diversity. Furthermore, the same user pair can join multiple alliances simultaneously, fully utilizing spatiotemporal diversity and relay diversity gain. For overlapping alliance structures, in addition to detecting untrusted relays, further detection of trusted relays within the alliance is added. By comparing the expected reward functions of detecting different numbers of relay nodes, the optimal detection nodes and detection set are selected, minimizing unnecessary detection overhead. For a given network topology, to achieve a stable overlapping alliance structure, a rule for establishing / breaking cooperative alliances is proposed. This rule possesses irreversible properties; when the topology remains unchanged, two user pairs that establish a cooperative relationship will not break the cooperative relationship, and vice versa, avoiding repeated calculations and iterations. Based on the alliance formation rule, a single-convergence dynamic alliance formation method is designed. All user pairs start from a single alliance that does not cooperate, and after one round of evaluation on whether to establish a cooperative relationship, they converge to a stable overlapping alliance structure. Taking the user pair's movement cycle as the unit, a three-stage dynamic distributed optimal cooperative channel security access method is proposed, consisting of node distance awareness, dynamic overlapping alliance formation, and optimal channel security opportunistic access. This method can continuously maintain optimal security access performance when the network dynamically changes.

[0203] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0204] As can be seen from the above description of the embodiments, those skilled in the art can clearly understand that this application can be implemented by means of software plus necessary general-purpose hardware platforms. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, can be embodied in the form of a software product. This computer software product can be stored in a storage medium, such as ROM / RAM, magnetic disk, optical disk, etc., and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute the methods described in various embodiments or some parts of the embodiments of this application.

[0205] The various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to mutually. Each embodiment focuses on describing the differences from other embodiments. In particular, for system or system embodiments, since they are basically similar to method embodiments, the description is relatively simple, and relevant parts can be referred to the descriptions in the method embodiments. The systems and system embodiments described above are merely illustrative. The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs. Those skilled in the art can understand and implement this without creative effort.

[0206] The above description is merely a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention are included within the scope of protection of the present invention.

Claims

1. A cooperative channel access method, characterized in that, include: For the Each location synchronization period determines the set of user pairs sharing the current channel. and untrusted relay sets ; All nodes set backoff time windows based on node IDs and broadcast location data packets sequentially according to an adaptive mechanism; Initialize an overlapable alliance structure ; Calculate the system's average safe throughput and the individual utility of each user pair ; For each user Each user and ,like Then calculate as well as ,renew ; This represents the set of all user pairs who have evaluated whether to establish a collaborative link; If the conditions for establishing cooperation are met by using the alliance formation rules, then update... Until all users have no intention to cooperate, a stable, overlapping alliance structure is reached. ; Based on a given stable alliance structure Calculate and obtain the first-level decision threshold vector System average safe throughput and category sets ; All users compete, decide, and access the system according to the distributed optimal channel security opportunistic access method; If the network changes dynamically after the current synchronization cycle ends, the user's set will be updated, and the next round of distance perception will begin. The rules for forming the alliance include: Given a union structure ,have If regarding alliance structure It meets the following conditions: Condition 1: , ; Condition two: ; Then the user's With users Establishing a partnership, users Join the alliance Users Join the alliance ; Given a union structure ,have ; Regarding alliance structure It meets the following conditions: Condition 1: , ; Condition two: ; Then the user's With users Breaking the partnership, users Leave the league Users Leave the league .

2. The cooperative channel access method according to claim 1, characterized in that, The adaptive mechanism includes: Set the backoff time window length for node contention channel based on node ID; The user determined that a channel was detected in one If the time slot is idle, then after its backoff time ends, it will be determined by probability. Send data packets; If a collision occurs, the backoff time is reset after the collision ends, and a probability is applied after the second round of backoff time. Send data packets until the location information data packets for all nodes have been sent.

3. The cooperative channel access method according to claim 2, characterized in that, The backoff time window length of the set node contention channel includes: if there is One user pair, i.e. The nth node, then the nth The backoff time for each node is .

4. The cooperative channel access method according to claim 1, characterized in that, Initialize an overlapable alliance structure This includes: at the beginning of the alliance's formation, assuming that all user pairs do not cooperate, then... .

5. The cooperative channel access method according to claim 1, characterized in that, Calculate the individual utility for each user pair include: For users Given an overlapable alliance structure Below, based on the optimal channel opportunistic access method, the user's expected benefit from access is the amount of securely transmitted data. The expected time cost is Then its individual utility function is: In the formula: This indicates the probability that the user will succeed in competing for the channel. and These represent the categories to which the corresponding channels belong after successful contention. , , User's expected revenue This represents the average safe throughput of the optimal system. This represents the average probability that a winning user in the network will choose not to access the channel after successfully contending for it. Indicates condition, Indicates the channel coherence time. This represents the average time of a single observation. Indicates the detection time. Indicates the optimal number of trusted relay detection nodes. and the corresponding payoff function, This indicates the maximum eavesdropping rate.

6. The cooperative channel access method according to claim 5, characterized in that, The average probability that a winning user in a network will choose not to access the channel after successfully contending for it. , represented as: In the formula: This represents the probability of abandoning access in the secondary decision-making stage. The probability of detecting a trusted relay in the alliance during the second-level decision-making process. This represents the probability of abandoning access in the three-level decision-making process. Indicates the direct channel SNR The probability distribution function.

7. The cooperative channel access method according to claim 1, characterized in that, First-level decision threshold vector Represented as: For users Define the optimal decision first-level threshold vector. ,in Equation , and The only solution.

8. The cooperative channel access method according to claim 1, characterized in that, For a given set of user pairs and untrusted relay sets When the topology of all nodes remains unchanged, the establishment or breaking of cooperation is irreversible.

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