Research On Distributed Channel Opportunistic Access Method Based On Coalition Formation Game Theory

As an important development direction of the wireless distributed network technology,distributed cooperative networks possess characteristics such as flexible networking,node autonomy management,minimal signaling interaction,and strong resilience,are widely used in many areas such as emergency communication and interconnectivity among unmanned clusters.By using the multi-node diversity gain,cooperative communications can improve the network performance,such as enhancing the transmission rates,expanding the communication coverage,and reducing the energy consumption.In recent years,domestic and international researches on the channel access methods of distributed cooperative networks are primarily focusing on the design of multi-node cooperative transmission mechanisms and access algorithms.In these studies,end-to-end users cooperative with each other to form multiple relay channels,aiming to optimize end-to-end communication capacity and effectively improve the overall performance of channel access.However,it should be noted that in the absence of a trust relationship between users and relays,the security channel access needs to consider the avoidance of relay’s eavesdropping.In the absence of dedicated relays,the willingness to cooperate among users in the network is motivated by theirs rewards and exhibits dynamic evolvability.Users participating in multiple groups simultaneously can further enhance the diversity gain.These dynamic characteristics further significantly impact the channel access methods of wireless networks,affecting user access mechanisms and transmission benefits,resulting in dynamic behavior in terms of channel access strategies and network transmission performance.To explore the interaction relationship among the user’s cooperative behavior,access utility,and the network performance,and to analyze the impact of untrusted relays on channel access strategies,based on the existing researches of our groups on distributed channel access,we conducted research on distributed channel access methods based on coalition formation game theory,utilizing sequential planning decision and coalition formation game theory as the foundation.The main work includes:1)Research on optimal channel access methods of distributed cooperative network.For the wireless cooperative networks with multiple relays,we analyze the relationships between network channel parameters and channel access process,model the distributed channel access problem as an observation-decision sequential planning problem and derive a basic structure of the optimal access method based on the sequential decision theory.The analytical expressions and monotonicity of the expected utility functions for different access decision options are derived.By analyzing the mapping relationships between threshold vectors,utility functions,and optimal decisions,a distributed optimal channel access method with pure threshold structure is proposed,and its throughput optimality is verified through numerical simulations.All thresholds in the proposed method can be calculated off-line based on channel statistics,which has low on-line computation complexity and greatly improves the system average throughput.2)Research on optimal channel access methods of distributed cooperative network based on the coalition formation games.In the scenario that sources relay for each other in the absence of dedicated relays,user pairs form disjoint cooperative groups by joining rational coalitions.For a given coalition structure,a distributed channel access method achieving the optimal system average throughput is proposed,and the individual utility functions are derived by following it.Combined with the coalitional switching rule of user pairs,a dynamic distributed coalition formation game algorithm driven by individual utilities of users is proposed to converge to a stable coalition partition.Combining with the multi-user channel contention access process and the optimal channel access method under the given coalition structure,an optimal channel access method of distributed cooperative network based on the coalition formation game theory can be designed,which has low computational complexity.The proposed method makes up for the deficiency of the existing channel access method research in the scene without dedicated relay,and is the first attempt to apply coalition formation game theory to the research on opportunistic access methods of cooperative channels,verifying the necessity of rational cooperation and the optimality of access method design under the stable coalition structure.3)Research on optimal channel secure access methods for untrusted relays.For a multiuser pair network with an untrusted relay,the optimal channel opportunistic access strategies are extended to the secure communication scenario.By combining the channel scheduling strategies in MAC layer with the DACJ mechanism of PLS technology,a distributed optimal channel secure access method is designed to maximize the average system secrecy throughput.The performance of the proposed strategy is compared with the existing CSMA/CA and ALOHA strategies through numerical simulations,and its superiority in terms of average system security throughput and SOP is verified.Compared with the existing research,the proposed method combines the channel scheduling of MAC layer with the cooperative jamming of PHY layer,makes full use of the advantages of cross-layer joint optimization,effectively improves the network secure transmission performance and lays a methodological foundation for the research of cooperative channel security opportunity access.4)Research on distributed channel access methods for wireless cooperative networks based on overlapping coalition formation games.The distributed optimal channel secure access method is modified to adapt to the overlapping coalition structures and the scenarios with multiple untrusted relays.For a given overlapping coalition structure,based on the distributed channel access statistics model and the distributed optimal channel secure access method under the condition that users can participate in multiple coalitions.We analyze the individual utility functions of user pairs and modify the traditional coalition formation rules,and design an optimized distributed overlapping coalition formation game algorithm for multiple user pairs converging to the stable coalition structure in one iteration.Combined with the multi-user channel contention access mechanism,a multi-user channel opportunistic access method based on overlapping coalition formation game theory is designed,which has well adaptability to network topology changes and lower computational complexity.The proposed method makes full use of the overlapping coalitional characteristics to improve the multi-relay diversity gain,and adjusts the contention probability based on the average access gain of users to avoid the time wasting caused by invalid contention.It is an efficient combination of coalition formation game,channel scheduling and secure transmission,and significantly improves the secure transmission performance of the network.