The authors study the performance of an amplify-and-forward dual-hop, switch-and-staycombining receiver, used in free space optical communications over non-identical fading channels. One path is characterised by the ...
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The authors study the performance of an amplify-and-forward dual-hop, switch-and-staycombining receiver, used in free space optical communications over non-identical fading channels. One path is characterised by the generalised Malaga (or M distribution), whereas the other is influenced by the combined effects of Gamma-Gamma distributed atmospheric turbulence, pointing error and path loss. Novel closed-form expressions for the end-to-end moment generating function, probability density function, and cumulative distribution function are derived in terms of Meijer's G function. Furthermore, the performance of the system is analysed, and closed-form expressions are presented for the end-to-end outage probability and channel capacity.
switch-and-staycombining (SSC) is a low-complexity alternative to selection combining (SC) in dual diversity systems. These diversity systems can either be the conventional colocated diversity setups, where two anten...
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switch-and-staycombining (SSC) is a low-complexity alternative to selection combining (SC) in dual diversity systems. These diversity systems can either be the conventional colocated diversity setups, where two antennas are available at the receiver, or the cooperative diversity systems, where two relays assist one transmitter-receiver pair. In SSC, a single diversity branch (i.e., a single antenna or a single relay) is activated and remains active as long as the corresponding channel is sufficiently strong, regardless of the quality of the other branch. Thereby, the switching threshold determines both the bit error rate (BER) and the switching rate, which are defined as the number of times per second a branch switching occurs. Since high switching rates are not preferred in practice, in this paper, we optimize the switching threshold of SSC to minimize the BER under a constraint on the switching rate. To this end, we derive approximate closed-form solutions for the optimization problem for both the colocated and the distributed antenna case. These solutions are shown to achieve close-to-optimal performance through computer simulations.
Spatial diversity schemes are often used to extract additional performance from wireless communication systems. Incorporating the partial relay selection (PRS) protocol into a distributed switch-and-stay combining (DS...
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Spatial diversity schemes are often used to extract additional performance from wireless communication systems. Incorporating the partial relay selection (PRS) protocol into a distributed switch-and-stay combining (DSSC) cooperative communication network gives the benefit of diversity while simplifying hardware, processing and feedback requirements. Because only a single relay is ever active, the destination employs no combiner; the best relay is chosen based on first-hop relay conditions. However, achieved performance is worse than other distributed protocols, such as distributed selection combining (DSC). In this study, signal space diversity (SSD) is added to the DSSC–PRS system to provide further diversity and error performance gains, at the expense of necessitating a maximum-likelihood detector with increased complexity at the receiver. Analytical results are presented in the form of a lower bound based on the minimum distance lower bound for SSD systems and are verified with simulation. The DSSC–PRS–SSD system shows an improvement of 5 dB at a symbol error rate of 10 − 4 as well as a clear diversity order improvement. Spectral efficiency of the new system with SSD is slightly decreased at low signal-to-noise ratios, but is still an improvement over other distributed schemes, such as DSC.
distributed switch-and-stay combining (DSSC) has been envisioned as an effective transmission technique to achieve spatial diversity in a distributed fashion, with low implementation complexity. In this paper, we take...
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ISBN:
(纸本)9781479913510
distributed switch-and-stay combining (DSSC) has been envisioned as an effective transmission technique to achieve spatial diversity in a distributed fashion, with low implementation complexity. In this paper, we take a step further to incorporate DSSC into spectrum-limited environment, where the operating nodes have to share the frequency radio spectrum with licensed users. In particular, by deploying DSSC scheme in cognitive radio networks, we have shown that the low transmit power at unlicensed users, inflicted by the peak interference power constraint at licensed users, can be alleviated. We present closed-form expressions for outage probability and spectral efficiency, enabling us to evaluate and optimize the considered network performance. Numerical and simulation results show that when the switching threshold is below the outage threshold the full diversity order can be guaranteed at the secondary networks.
In this letter, we propose a distributed switch-and-stay combining network with partial relay selection and show that the system spectral efficiency can be improved via adaptive modulation. Analytical expressions for ...
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In this letter, we propose a distributed switch-and-stay combining network with partial relay selection and show that the system spectral efficiency can be improved via adaptive modulation. Analytical expressions for the achievable spectral efficiency and average bit error rate of the proposed system over Rayleigh fading channels are derived for an arbitrary switching threshold. Numerical results are gathered to substantiate the analytical derivation showing that in terms of spectral efficiency, the system with single relay outperforms that with more than one relay at high signal-to-noise ratios (SNRs) and the optimal switching threshold can significantly improve the system performance at medium SNRs.
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