Salama S. Ikki

Multihop Wireless Relaying Systems in the Presence of Cochannel Interferences: Performance Analysis and Design Optimization

A study of the effect of cochannel interference on the performance of multihop wireless networks with amplify-and-forward (AF) relaying is presented. Considering that transmissions are performed over Rayleigh fading channels, first, the exact end-to-end signal-to-interference-plus-noise ratio (SINR) of the communication system is formulated and upper bounded. Then, the cumulative distribution function (cdf) and probability density function (pdf) of the upper bounded end-to-end SINR are determined. Based on those results, closed-form expression for the error probability is obtained. Furthermore, an approximate expression for the pdf of the instantaneous end-to-end SINR is derived, and based on this, a simple and general asymptotic expression for the error probability is presented and discussed. In addition, the ergodic capacity of multihop wireless networks in the presence of external interference is studied. Moreover, analytical comparisons between AF and decode-and-forward (DP) multihop in terms of error probability and ergodic capacity are presented. Finally, optimization of the power allocation at the networks transmit nodes and the positioning of the relays are addressed.

Performance Analysis of Dual-Hop Relaying Systems in the Presence of Co-Channel Interference

Abstract-In this paper, we investigate the effect of co-channel interference on the performance of dual-hop communications with amplify-and-forward relaying. Based on the derivation of the effective signal-to-interference-plus-noise ratio (SINR) at the destination node of the system, taking into account co-channel interference, we obtain expressions for the error and outage probabilities. Moreover, we study the performance of the system in the high SINR regime. Monte-Carlo simulations are further provided and confirm the accuracy of the analytical results.

Performance Analysis of Two-Way Amplify-and-Forward Relaying in the Presence of Co-Channel Interferences

The performance of two-way amplify-and-forward (AF) relaying networks, considering transmissions over independent but not necessarily identically distributed Rayleigh fading channels in the presence of a finite number of co-channel interferers, is studied. Specifically, closed-form expressions for the cumulative distribution function (CDF) of the equivalent signal-to-interference-plus-noise ratio (SINR), the error probability, the outage probability and the systems achievable rate, are presented. Furthermore, an asymptotic expression for the probability density function (PDF) of the equivalent instantaneous SINR is derived, based on which simple and general asymptotic formulas for the error and outage probabilities are derived and analyzed. Numerical results are also provided, sustained by simulations which corroborate the exactness of the theoretical analysis.

A Study of Optimization Problem for Amplify-and-Forward Relaying over Weibull Fading Channels with Multiple Antennas

We consider power allocation (PA) and relay positioning in a dual-hop regenerative relaying system with multi-antenna destination node in Weibull fading environment. With the fixed relay location, adaptive PA at the source and relay nodes under joint power constraint and with the aim to minimize the average error probability at high signal-to-noise ratios (SNRs) is presented. Then considering fixed PA, the optimal relay location is derived. Thereafter, we propose to jointly optimize the PA and relay positioning. Numerical simulations are also provided to validate the analytical results, and comparisons between the different optimization schemes and their performance are presented. Results show that optimum PA brings only coding gain, while optimum relay positioning yields diversity gains as well. Also, joint optimization improves both, the diversity gain and the coding gain. Furthermore, results illustrate that the proposed adaptive algorithms outperform uniform schemes.

Two-Way Amplify-and-Forward Relaying with Gaussian Imperfect Channel Estimations

In this letter, we study the effect of channel estimation errors on the reception reliability of two-way relaying. For a network with two users that exchange information with each other through multiple amplify-and-forward relays, we investigate a single-relay selection scheme. Since the communication is two-way, the selection scheme aims at optimizing the worse performance of the two communication tasks between the pair of users. The signal-to-noise ratio (SNR) at the users nodes of the relaying network is formulated and upper bounded. Then, the probability density function (PDF) of the upper bounded SNRs are determined. Subsequently, expressions for the error probabilities are obtained. Furthermore, an approximate PDF of the output instantaneous SNRs are derived, based on which simple and general asymptotic expressions for the error probabilities are presented and discussed. Numerical and simulation results are provided to verify the analysis and compare the performance of the two-way relaying network for different operating conditions and scenarios.

Impact of Imperfect Channel Estimation and Co-Channel Interference on Regenerative Cooperative Networks

In this work, we analyze the performance of decode-and-forward cooperative diversity networks with imperfect channel estimation and co-channel interference. Orthogonal relaying is considered and all relays that correctly decode the source message in the broadcasting phase participate in the relaying phase. First, the output signal-to-interference-plus-noise ratio (SINR) at the destination is derived. Then, considering error and outage as the performance metrics, we obtain exact closed-form expressions for the error and outage probabilities. Simple and general asymptotic expression for the error probability, which explicitly shows the coding and the diversity gains, is also derived and discussed.

Performance Study and Optimization of Cooperative Diversity Networks with Co-Channel Interference

In this paper, we investigate the effect of co-channel interference on the performance of cooperative diversity networks with amplify-and-forward (AF) relaying. We consider both conventional and opportunistic relaying. First, we obtain a tight upper-bound for the equivalent signal-to-interference-plus-noise ratio (SINR) at the destination. Subsequently, the cumulative distribution function (CDF), probability density function (PDF) and moment generating function (MGF) of the effective SINR are determined based on the upper-bound. Expressions for the error probabilities in both conventional and opportunistic relaying are derived utilizing the statistical characterization of the effective SINR. We also derive an approximate PDF of the equivalent instantaneous SINR at the destination. This leads to a simple and general asymptotic error probability expression which facilitates better insight into the effect of different system parameters on the error probability. Furthermore, we investigate the problem of optimum resource allocation in the network aiming at improving performance in the presence of resource constraints. We present numerical results that illustrate the excellent match between the analytical results and the simulation results, and the performance enhancement resulting from the proposed optimal resource allocation.

Impact of Imperfect Channel Estimation and Co-Channel Interference on Dual-Hop Relaying Systems

In this letter, we analyze the performance of amplify-and-forward dual-hop cooperative diversity networks with imperfect channel estimation in the presence of co-channel interference. Exact closed-form expression is derived for the end-to-end signal-to-interference-plus-noise ratio (SINR), and an upper-bound of the exact SINR is introduced. In addition, exact closed-form expressions are obtained for the cumulative density function (CDF) of the upper-bound SINR and the average symbol error probability (ASEP). Furthermore, simple and accurate asymptotic expression for the ASEP is derived. Simulation results demonstrate the accuracy of the theoretical analysis.

Effects of Co-Channel Interference on the Error Probability Performance of Multi-Hop Relaying Networks

We introduce closed-form lower bounds for the performance of multi-hop wireless networks with non-regenerative relays over Rayleigh fading channels in the presence of co-channel interference. The analysis assumes an arbitrary number of independent and identically distributed Rayleigh interferers. Novel closed-form expressions are obtained for the probability density function (PDF) and cumulative distribution function of the upper bounded end-to-end signal-to-interference-plus-noise ratio (SINR) at the destination node. These results are then used to study the average error probability. Furthermore, an approximate expression for the PDF of the instantaneous end-to-end SINR is derived, based on which general asymptotic expression for the error probability is presented and discussed. Moreover, analytical comparison of the error probability achieved by amplify-and-forward and decode-and-forward multi-hop transmissions is provided. Using these expressions, the effect of co-channel interference on system performance is investigated.

A Study of Optimization Problem for Amplify-and-Forward Relaying over Weibull Fading Channels

This paper addresses the power allocation and relay positioning problems in Amplify-and-forward cooperative networks over Weibull fading channels. We study adaptive power allocation (PA) with fixed relay location, optimal relay location with fixed power allocation, and joint optimization of the PA and relay location under total transmit power constraint, in order to minimize the outage probability and average error probability at high signal-to-noise ratios (SNR). Analytical results are validated by numerical simulations and comparisons between the different optimization schemes and performance are provided. Results show that optimum PA brings only coding gain, while optimum relay location yields, in addition to the latter, diversity gains as well. Also, joint optimization improves both, the diversity gain and coding gain. Furthermore, results illustrate that the analyzed adaptive algorithms outperform uniform schemes.