Relay Network In Presence Research Articles

Multiuser diversity for mixed RF/FSO cooperative relaying in the presence of interference

This paper presents the performance of multiuser diversity over mixed radio frequency / free space optical (RF/FSO) relay network in presence of co-channel interference at relay and destination nodes. The multiuser RF link between source-to-relay experiences Nakagami-m fading, while the FSO link between relay-to-destination is assumed to be affected by α−μ distributed atmospheric turbulence. Moreover, the amplitudes of the interfering signals at relay and destination nodes are assumed to follow independent Nakagami-m fading distribution. We consider both forms of optical demodulation schemes i.e., coherent detection and intensity modulation with direct detection (IM/DD) demodulation. Novel expression of the end-to-end cumulative distribution function (CDF) for the proposed mixed RF/FSO system has been derived which is further utilized to obtain the closed-form expression for outage probability and bit-error-rate of the overall system. Additionally, we present asymptotic expressions of outage probability and bit-error-rate to yield quick insights of the system performance. Finally, the numerical results are provided to examine the effect of various system parameters which are also supported by Monte-Carlo simulations.

Security-Reliability Analysis of Noma-Based Multi-Hop Relay Networks in Presence of an Active Eavesdropper with Imperfect Eavesdropping CSI

In this paper, we evaluate system performances of a multi-hop relay protocol with presence of an active eavesdropper. In the proposed protocol, a source attempts to transmit its data to a destination with assistance of multiple intermediate relays. From the eavesdropping Channel State Information (CSI) estimated, the source and relays adjust their transmit power so that the eavesdropper cannot overhear the transmitted data. Moreover, to enhance throughput for the proposed system, Non-Orthogonal Multiple Access (NOMA) technique with a simple power allocation is also proposed. We derive exact closed-form expressions of the Outage Probability (OP) and throughput for the data transmission over Rayleigh fading channel. In addition, when the CSI estimation is imperfect, Intercept Probability (IP) at the eavesdropper is derived. Finally, Monte Carlo simulations are presented to verify the theoretical derivations.

A REVIEW ON DISTRIBUTED BEAM FORMING TECHNIQUES -AN APPROACH IN WIRELESS RELAY NETWORKS

Physical layer security can be considered to solve the security problem from the point of view of information theory in wireless networks. The combination of cryptographic schemes with channel coding techniques is called for in the basic principle of information-theoretic security. Due to the presence of one or more eavesdropper in wireless relay networks, secrecy of communication is in jeopardy. For such a scenario secrecy rate of the network provide a good measure of performance of the system. In this paper our focus is on secrecy capacity and its optimization with appropriate weight designs of relays taking into consideration the channels through which the eavesdroppers are connected to the relays. We propose the AF and DF based optimal beam forming scheme to improve the wireless security against eavesdropping attack by detecting and removing the eavesdroppers from the wireless relay networks and thus finding measures to maximize the efficiency, response time and the throughput of the system It includes an auto-regression technique as first approach and the use of RC6 algorithm for encrypting the confidential messages. The scheme is a two way approach that will not only provides security to the confidential messages, to be communicated within a wireless relay network in presence of multiple relays and eavesdroppers, but also it will deal with the saving the consumed power by detecting and removing the nodes which are malicious or defected which in turn will consume more power in order to perform malicious activity on the messages or may try to create interferences in the network. The eavesdropper nodes in the proposed system are considered to be working as relays so it may either be connected to source or destination directly or in between the relays.