Fair and efficient resource allocation for cooperative diversity in ad-hoc wireless networks

User cooperation is a powerful solution that can significantly improve the reliability of wireless networks by using several relays to achieve diversity gains. There has been a lot of work on improving the peer-to-peer link quality of a single source-destination pair. However, how to fairly and efficiently allocate resources among multiple nodes has not received much attention vet. In this paper, we propose a novel cooperative diversity method that can achieve fair and efficient resource allocation. We shall show that fairness cannot be achieved by using fixed sets of relays in general. A multi-state cooperation method, where the relay set of each node can be changed, is then proposed to solve this problem. In this proposed approach, the energy is allocated among the nodes via a finite step iterative algorithm. In each step, the relay sets of nodes are changed so that each step will generate a cooperation state, which characterizes the cooperation relationship among the nodes. Based on the energy allocation result, the duration of each state is then optimized so as to minimize the outage probability. We shall show that the proposed method can not only guarantee fairness, but also provide significant diversity gain over conventional cooperation schemes

Efficient Power Allocation Schemes for Hybrid Decode-Amplify-Forward Relay Based Wireless Cooperative Network

Cooperative communication in various wireless domains, such as cellular networks, sensor networks and wireless ad hoc networks, has gained significant interest recently. In cooperative network, relays between the source and the destination, form a virtual MIMO that creates spatial diversity at the destination, which overcomes the fading effect of wireless channels. Such relay assisted schemes have potential to increase the channel capacity and network coverage. Most current research on cooperative communication are focused broadly on efficient protocol design and analysis, resource allocation, relay selection and cross layer optimization. The first part of this research aims at introducing hybrid decode-amplify-forward (HDAF) relaying in a distributed Alamouti coded cooperative network. Performance of such adaptive relaying scheme in terms of symbol error rate (SER), outage probability and average channel capacity is derived theoretically and verified through simulation based study. This work is further extended to a generalized multi HDAF relaying cooperative frame work. Various efficient power allocation schemes such as maximized channel capacity based, minimized SER based and total power minimization based are proposed and their superiority in performance over the existing equal power allocation scheme is demonstrated in the simulation results. Due to the broadcast nature of wireless transmission, information privacy in wireless networks becomes a critical issue. In the context of physical layer security, the role of multi HDAF relaying based cooperative model with control jamming and multiple eavesdroppers is explored in the second part of the research. Performance evaluation parameters such as secrecy rate, secrecy outage and intercept probability are derived theoretically. Further the importance of the proposed power allocation schemes in enhancing the secrecy performance of the network in the presence of multiple eavesdroppers is studied in detail through simulation based study and analysis. For all the proposed power allocation schemes in this research, the optimization problems are defined under total power constraint and are solved using Lagrange multiplier method and also evolutionary algorithms such as Differential evolution and Invasive Weed Optimization are employed. Monte Carlo simulation based study is adopted throughout the research. It is concluded that HDAF relaying based wireless cooperative network with optimal power allocation schemes offers improved and reliable performance compared to conventional amplify forward and decode forward relaying schemes. Above research contributions will be applicable for future generation wireless cooperative networks