Performance Analysis of Hybrid Decode-Amplify-Forward (HDAF) Relaying for Improving Security in Cooperative Wireless Network

In present communication scenario, security and privacy of data being transmitted is very difficult due to the openness of wireless medium. To secure and protect the confidentiality of data being transmitted, physical layer security offers attractive solutions using cooperative relaying schemes, in which relay assists the transmission of data between source and destination. In this work, we consider a cooperative wireless network in which relay either tries to improve the channel capacity of source to destination link using cooperative relaying protocols or reduce the channel capacity of source to eavesdropper link using jamming techniques. In order to improve the performance of the communication system, optimal relay and jammer are selected based on the three proposed relay and jamming selection schemes namely Conventional selection (Without jamming), Optimal selection with jamming (OSJ) and Optimal selection with control jamming (OSCJ).Optimal relay forwards the source information using cooperating relaying protocols such as decode and forward(DF), Amplify and Forward(AF) ,Hybrid decode amplify forward (HDAF) which combines the benefits of both DF and AF schemes. At the same time, jammer generates artificial noise using cooperative jamming scheme, to confuse the eavesdropper. The received signals at the receiver are combined using the various diversity techniques such as maximum ratio combining (MRC) and fixed ratio combining (FRC) techniques.Monte Carlo simulations are carried out and the obtained results are compared for different relay,jammer and eavesdropper locations. A study of comparison is made in terms of secrecy capacity and intercept probability for the proposed relaying schemes in the presence of single eavesdropper. Finally from the simulated comparison study, it is observed that HDAF scheme outperforms AF and DF schemes and we can also observe control jamming selection achieves more secrecy rate compared to without jamming and with optimal jamming

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