Research On Wireless Spectrum Sharing Based On Contract Theory

With the rapid development of information technology in recent years,the even increasing service demands bring new challenges in future wireless communication systems.One of the most prominent challenges is the natural scarcity of radio resources.It is imminent to find a new technology that can effectively alleviate the conflict between spectrum scarcity and increased demands.Cognitive radio is regarded as a new emerging design paradigm that can effectively enhance the efficiency of spectrum utilization and has become the focus of many scholars.At the same time,considering the advantages of cooperative communication in improving transmission reliability and increasing system capacity.It is often used in cognitive radio network to improve performance.In the existing cognitive networks,due to the inherent uncertainty and time-varying nature of the wireless channel,information is incomplete between primary user and secondary users,which greatly increases the difficulty of cooperation.Therefore,based on the cognitive radio network,this dissertation incorporates contract theory and cooperative relaying technology to study the problem of asymmetric information and design of incentive mechanism between primary user and secondary users.We combine Orthogonal Frequency Division Multiplexing technology with model to solve the interference between primary user and secondary users or between multiple secondary users.The main work and research results are as follows:1.In view of the different information situations between the primary users and the secondary users,we propose a cooperative spectrum sharing method based on the contract theory for the joint optimization of power and bandwidth.In this method,the interaction process between primary users and secondary users is modeled as a similar labor market model.Primary users and secondary users act as employers and employees in the model respectively.In particular,the secondary user provides the labor force(that is,the relay power used to transmit the information of the primary user)in exchange for the remuneration provided by the primary user(that is,the bandwidth used to send the information of its own).Secondary users can be divided into various types according to their personal information,and corresponding contracts are selected according to different types,and feedback information is given to primary users.We study the contract design problem of symmetric information and asymmetric information,and obtain the optimal access bandwidth and relay power allocation to achieve the goal of maximizing the benefit of primary users.In symmetric information,primary users send each secondary user a contract that contains only the corresponding contract entries of its type;in asymmetric information,the primary user broadcasts a contract containing a number of candidate contract entries to the surrounding secondary users.This method also considers the performance of primary users and secondary users,so as to achieve win-win results.The performance is analyzed through simulation,and compared with other methods,the result proves that this method can make the system achieve better performance.2.In the broadband wireless communication system,we combine the OFDM technology based on contract theory with a time slot and subcarriers joint optimized wireless spectrum sharing method,and study the problem of reasonable contract design and the secondary user selection under the limited budget of the multi-carrier wireless system with different information.In the spectrum sharing method,the first slot allows users to broadcast information that needs to be transmitted.The second time slot,the secondary user forwards the primary user information with the expected signal-to-noise ratio of the primary user.Third time slot,secondary users are given different subcarriers to transmit their information based on the different incentives.This method eliminates the interference between the primary users and the secondary users through the division of the time slot,and eliminates the interference between the secondary users through the allocation of subcarriers.In order to maximize the benefit of primary users,the optimal contract is designed and the secondary user is chosen to meet the requirements of the primary user budget constraints and the individual constraints of the secondary users.The simulation results verify the feasibility and effectiveness of the proposed method.Both the primary and the secondary users can benefit from the proposed method,and the benefit has been greatly improved,and the spectrum utilization is effectively improved.