This study investigates the impact of co‐channel interference caused by external terminals on multi‐user bi‐directional amplify‐and‐forward based wireless relaying network. The investigation considers multi‐user pair and a single bi‐directional relay terminal and a finite number of co‐channel interference in the system model. A lower bound on the end‐to‐end outage probability is derived for the simultaneous transmission and the opportunistic source‐pair selection strategy. According to analytical, asymptotic, and Monte‐Carlo based computer simulation results, the opportunistic source‐pair selection strategy achieves a near‐optimal performance for the inter‐cell interference caused by other user‐pairs within the system. Results also show that the opportunistic source‐pair selection strategy also achieves optimal diversity order, which is equal to N , in high signal‐to‐noise ratio regimes. Results also show that the co‐channel interference degrades the achievable diversity order from N to 0 while also affecting the system coding gain.

Free space optical (FSO) communication systems provide high bandwidth in unregulated spectrum and act as a powerful line-of-sight wireless connectivity solution. The performance of FSO systems can be seriously impaired by fading as a result of atmospheric turbulence and/or pointing errors due to misalignment. In the context of FSO systems, relaying was proposed as an effective fading mitigation technique due to the fact that the variance is distance-dependent in turbulence channels. In this article, we present a unified performance analysis of multi-hop FSO systems over Double Generalized Gamma (DGG) turbulence channels with pointing error impairments. We assume amplify-and-forward relaying and consider both heterodyne detection and intensity modulation with direct detection. We derive tight closed-form expressions for the outage probability and bit error probability of both fixed-gain and channel state information (CSI)-assisted relaying in terms of the bivariate Fox-H functions and Fox-H functions, respectively. We further analyze asymptotic behavior of the outage probability in terms of simple elementary functions and obtain the achievable diversity orders. Diversity gain is found to be a function of atmospheric turbulence parameters, pointing error, detection type and the number of hops. Monte Carlo simulation results are further provided to verify the accuracy of the derived expressions.

Free space optical (FSO) communication systems provide line-of-sight wireless connectivity in the unlicensed optical spectrum and achieve higher data rates in comparison to their radio frequency (RF) counterparts. FSO systems are particularly attractive for the last mile access problem by establishing a connectivity bridge between optical fiber-based backbone and RF access networks. To address this practical deployment scenario, there has been an increasing attention on the so-called mixed (dual-hop) FSO-RF systems where FSO transmission is utilized at one hop followed by RF transmission at the other one. In this paper, we investigate the performance of mixed FSO-RF transmission systems where the FSO link is modeled by the double generalized Gamma distribution with generalized pointing error impairments and the RF link experiences the extended generalized-K shadowed fading. For both amplify-and-forward and decode-and-forward relaying, we derive closed-form expressions for outage probability, bit error probability, and ergodic capacity in terms of bivariate Fox-H function. Monte Carlo simulation results are provided to verify the accuracy of derived expressions. We further provide an asymptotic analysis and discuss the achievable diversity orders of mixed FSO-RF systems.

This study investigates the opportunistic source‐pair selection (OSPS) strategy for the intercell interference (ICI) challenge in multi‐user amplify‐and‐forward‐based bi‐directional wireless relaying networks. The method relies on selection of an appropriate SP node among N available SP nodes based on each SP's maximum sum capacity (SC). According to analytical, asymptotic and Monte Carlo simulation results, the OSPS strategy, besides achieving the near‐optimal solution for the ICI challenge, if the number of the user‐pair increases, also achieves multi‐user diversity gain by selecting the maximum SC user‐pair in each time slot. Moreover, the SC‐based user‐pair selection method outperforms the simultaneous transmission model and the max–min‐based user‐pair selection method in such a system model.

Free space optical (FSO) links provide an efficient point-to-point wireless transmission solution. They are particularly useful for filling the connectivity gap between the radio frequency (RF) access network and the fiber optic-based backbone network. To address this combined use, there has been a growing interest in so-called mixed RF/FSO systems where RF transmission is used at one hop and FSO transmission at the other in a dual-hop configuration. In this paper, we investigate the performance of mixed RF/FSO systems along with a direct RF link where the FSO link and RF links, respectively, experience double generalized gamma turbulence with pointing error and Nakagami-m fading. Moreover, the effect of cochannel interference is considered at both relay and destination. Under the assumption of amplify-and-forward relaying and selection combining at the destination, we derive closed form expressions for outage probability and bit error probability in terms of Meijer's-G and two-variate Fox-H functions. Our analysis provides a generalized framework for several existing results, since our adopted turbulence and fading statistical models are the most general ones. Based on the high signal-to-noise-ratio analysis, we further provide a diversity gain analysis and discuss the bottlenecks in the mixed RF/FSO systems.

Two closed-form expressions for the end-to-end cumulative distribution function (CDF) and outage probability of two-way interference-limited amplify-and-forward (AF) relaying were recently presented in Equations (19) and (24) in the above titled paper (ibid., vol. 61, no. 8 pp. 3156-3169, Aug. 2013). However, the expressions contain a notational error. A correction is presented here.

In this paper, we present the performance of selective combining decode-and-forward relay networks in independent and non-identically distributed Nakagami-n and Nakagami-q fading channels by using the best-worse and the decoding-set approaches. The outage probability, moment generation function, symbol error probability and average channel capacity are derived in closed-form using the signal to noise ratio SNR statistical characteristics. After that, we analyze the outage probability at high SNRs, and then, we optimize it. Beside the optimum method, we have proposed a sub-optimum adaptive method. Also, we derive the outage probability for the selection-combining case with the direct link between the source and the destination. Finally, for comparison with analytical formulas, we perform some Monte-Carlo simulations. Copyright © 2012 John Wiley & Sons, Ltd.

We investigate the performance of two-way interference-limited amplify-and-forward relaying systems over independent but non-identically distributed (i.n.i.d.) Nakagami-m fading channels. A tight closed-form lower bound on the outage probability of the system is derived, along with a simplified expression in the asymptotically low outage regime. Some special cases of practical interest (e.g., no interference power and interference-limited case) are also examined. The theoretical and numerical results provide important physical insights into the implications of the model parameters on the system performance.

We investigate the performance of two-way interference-limited amplify-and-forward (AF) relaying systems with selection-combining (SC) over Nakagami-m fading channels. In particular, a tight lower bound on the end-to-end outage probability (OP) is derived in closed-form, while a useful expression is presented for the asymptotically low outage regime. Some special cases of practical interest (e.g., no interference power and Rayleigh fading channels) are also studied. The numerical results provide important physical insights into the implications of model parameters on the system performance.

We analyze the performance of a dual-hop selection combining amplify-and-forward cooperative system over independent and identically distributed Nakagami-m fading channels, where multiple antennas are deployed in the receive side of relays and the destination. The outage probability, symbol error probability and average channel capacity are derived at arbitrary signal to noise ratios (SNRs). In order to obtain additional physical insights, we derive the above mentioned performance metrics in the high SNR regime; this enables us to parameterize the performance of the system in terms of diversity order and coding gain. Furthermore, some special cases of interest (e.g., Nakagami-0.5 and Rayleigh fading channels) are also studied. It is demonstrated that the analytical expressions, expressed via infinite series, match precisely with the Monte-Carlo simulations using only a small number of terms.

In this paper, we investigate the performance of two-way interference-limited amplify-and-forward relaying systems over independent, non-identically distributed Nakagami-m fading channels. Our analysis generalizes several previous results, since it accounts for interference affecting all network nodes. In particular, tight lower bounds on the end-to-end outage and symbol error probability are derived in closed-form, while a useful expression is presented for the asymptotically low outage regime. Some special cases of practical interest (e.g., no interference power and interference-limited case) are also studied. Using the derived lower bounds as a starting point and for the case of Rayleigh fading, we formulate and solve analytically three practical optimization problems, namely, power allocation under fixed location for the relay, optimal relay position with fixed power allocation, and joint optimization of power allocation and relay position under a transmit power constraint. The numerical results provide important physical insights into the implications of model parameters on the system performance; for instance, it is demonstrated that relay position optimization offers significant performance enhancement over the non-optimized case for an asymmetric interference power profile, whilst the optimization gains are marginal for a symmetric one.

In this paper, we present the performance of selective combining decode-and-forward relay networks in independent and non identical distributed Rician fading channels. The outage probability, moment generation function, symbol error probability and average channel capacity are derived in closed-form using the SNR statistical characteristics. After that, we analyze the outage probability at high SNR and then we optimize it. Finally, for comparison with analytical formulas, we perform some Monte-Carlo simulations.