Conventional and modified TAS/OSTBC schemes in dual-hop fixed-gain amplify-and-forward relaying systems with imperfect feedback

Abstract

Modified transmit antenna selection (TAS)/orthogonal space-time block coding (OSTBC) (M-TAS/OSTBC) schemes have been shown to achieve superior error performance together with a reduced-rate feedback channel in the presence of feedback errors (FEs) when compared with the conventional TAS/OSTBC (C-TAS/OSTBC) schemes. This paper focuses on the bringing of fixed-gain amplify-and-forward (FGAF) relaying schemes that employ M-TAS/OSTBC schemes at both hops that provides reduced feedback-rate and robust error performance in the presence of erroneous-feedback channels. The exact expressions of the outage and error probabilities for both dual-hop FGAF relaying schemes in Nakagami-m fading channels have been derived and validated via Monte Carlo simulations. Additionally, with the help of high signal-to-noise ratio (SNR) (i.e., asymptotic) approaches and some analytical approximations, the asymptotic diversity order analysis has been carried out. Besides, by providing a simulation-based examination on the inclusion of power allocation within the modified scheme, the additional advantages on the performance have been exhibited. The extensive investigation and comparisons to the conventional schemes have shown that M-TAS/OSTBC schemes employed at each transmission link provide full diversity order and considerable error performance as the C-TAS/OSTBC scheme in ideal feedback cases and also achieve more robust error performance in the presence of FEs. Thus, by using M-TAS/OSTBC schemes, the overall performances of the dual-hop FGAF relaying schemes have been enhanced, which would result in reductions on the average SNR requirements to achieve a specified error rate constraint. Copyright (c) 2015 John Wiley & Sons, Ltd.