| With the rapid development of wireless communication techniques,the Multiple-Input Multiple-Output(MIMO)technique has attracted much attention for its superior performance.The technique can provide diversity gain to increase the link reliability,and can also provide multiplexing gain to improve the system transmission rate.Furthermore,a trade-off between different functions of a system can also be achieved,and it plays an important role in terms of increasing network coverage,saving energy consumption,reducing interference between different cells,improving system throughput and so on.Given this,MIMO has been widely used in various wireless networks.However,as the technique needs to install multiple antennas on terminals,which means taking up extra space and power of the terminals,and this makes the technique cannot be implemented in the situation where the terminals' size and power are strictly limited.Thus,the issue restricts the application of this technique.To solve this problem,cooperative diversity has been proposed.The technique can take advantage of the broadcast nature of wireless channels,such that users can share each other's resources to create a virtual multi-antenna environment and thus realize the technique of MIMO.The technique provides a completely new idea for the applications of MIMO.In recent years,cooperative diversity has been drawing widely attention,and its superior performance has been fully confirmed.However,the technique cannot be properly implemented in distributed wireless networks.This is due to the fact that there is no centralized node in a distributed network,each user can choose whether to participate in cooperation by himself,if a user chooses to forward information for other users,he needs to consume extra resources(such as energy and bandwidth,etc.),and there is no guarantee that he can find a partner who is willing to relay his information.If a user is rational or selfish,he will choose not to cooperate.This problem seriously restricts the application of cooperative diversity in distributed wireless networks.To address the above issues,this paper introduces game theory to analyze the users' behavior,and then presents effective cooperative incentive mechanisms to make sure the cooperative diversity technique can be achieved in the distributed network.At the same time,efficient resource allocation schemes are proposed,which makes the use of resources more efficiently.The main contribution of this dissertation can be summarized as follows.Consider a distributed wireless network with multiple source and multiple relay nodes,the problem of how to assign source-relay pairs to achieve cooperation is investigated.The pricing-based approach is introduced to stimulate cooperation.And when a source node is matched with a relay node,it will obtain diversity gain and the relay node can get virtual revenue,which can be used to stimulate cooperation when he has data to send.By jointly considering the benefits of the source node and the relay node,we prove that the source-relay assignment problem can be modeled by a two-sided one-to-one matching game,which is a branch of coalitional games.The deferred acceptance procedure is introduced to solve the matching problem,and it turns out that a solution can always be found and is proved in the core of the coalitional game.Consequently,each node is satisfied with its final state and has no incentive to deviate,which leads to a stable matching state.Simulation results demonstrate that the proposed matching scheme has linear time complexity,which means the scheme is easy to implemention.However,it can achieve comparable performance to that employing centralized optimal scheme in terms of total profit of the system.To address the noncooperation problems of selffish nodes in distributed cooperative wireless networks,an auction-based pricing scheme is introduced to stimulate cooperation.And then an efficent partner selection method is designed,in which sources act as bidders and relays act as auctioneers,and the sources compete to obtain the relay's assistance with monetary incentives.Due to the fact that the sources should compete with each other to determine the recipient of the cooperative resources,the proposed scheme is an example of so-called competitive fairness.When an auction is implemented,the winning source will obtain diversity gains and the relay will get virtual currency.The two most prevalent auction forms,i.e.,the second-price auction and first-price auction are both introduced and analyzed in this paper.A single-relay network is considered first,and the Nash equilibrium(NE)for each source and the optimal reserve price for the relay are characterized.Based on the equilibrium,the expected payoff of each source and the expected revenue of the relay are then derived.Furthermore,from the perspective of the whole system,the multiple-relay networks are discussed,in which a source can select multiple partners for cooperative transmission by bidding to several relays.It is proved that the issues that to which relays should each source bid can be modeled as linear 0-1 integer programming problems in both the second-and first-price auctions.We draw the conclusion that a source prefers the first-price auction to the second-price auction when its virtual currency is limited.In distributed wireless networks,to solve the following two basic problems,i.e.,when to cooperate and how to cooperate,a cooperation strategy among rational nodes in a wireless cooperative relaying network is proposed.A symmetric system model comprising two users and two destination nodes is presented.In the model,each user plays an equal role and acts as a source as well as a potential relay and has the right to decide whether to cooperate.Cooperative communications is modeled as a repeated game in which the two participating terminals are selfish and seek to maximize their own payoff,a general utility function that monotonically increases with signal-to-noise ratio.Results show if the node care his future payoff,a Nash Equilibrium in which users mutually cooperate can be derived. |
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