Abstract
In this paper, we propose an output threshold-based incremental multiple-relay combining scheme for cooperative amplify-and-forward relay networks with nonidentically distributed relay channels. Specifically, in order to achieve the required performance, we consider both conventional incremental relaying and multiple-relay selection where relays are adaptively selected based on a predetermined output threshold. Moreover, the adaptive modulation technique is adopted by our proposed scheme for satisfying both the spectral efficiency and the required error rate. For the proposed scheme, we first derive an upper bound of the output combined signal-to-noise ratio and then provide its statistics such as cumulative distribution function (CDF), probability density function (PDF), and moment generating function (MGF) over independent, nonidentically distributed Rayleigh fading channels. Additionally, we analyze the system performance in terms of average spectral efficiency, average bit error rate, outage probability, and system complexity. Finally, numerical examples show that our proposed scheme leads to a certain performance improvement in the cooperative networks.
Highlights
In modern wireless communications, diversity techniques have received great attention to mitigate wireless channel impairments
Opportunistic relaying was proposed in [2] where the system used only the best one among relays based on the relay selection criteria and proved that the same diversity-multiplexing tradeoff could be achieved as the space time-coded cooperative network [3]
We propose output thresholdbased incremental multiple-relay combining with adaptive modulation (IMRC-AM) that is an extended work of the conventional incremental relaying in a distributed multiplerelay network and that can achieve both high spectral efficiency and high diversity gain
Summary
Diversity techniques have received great attention to mitigate wireless channel impairments. Authors in [6] proposed an output threshold-based multiple-relay selection scheme in the amplify-and-forward (AF) transmission where Lc relays are sequentially selected out of L relays according to the predetermined threshold at the destination and gave performance analyses over the independent, identically distributed (i.i.d.) Rayleigh fading channels. We propose output thresholdbased incremental multiple-relay combining with adaptive modulation (IMRC-AM) that is an extended work of the conventional incremental relaying in a distributed multiplerelay network and that can achieve both high spectral efficiency and high diversity gain. Instead just checking some fixed values of output thresholds at the destination like the conventional diversity system [14] and relaying systems [1, 6], we use the minimum threshold of adaptive modulation as the output threshold in order to achieve both spectral efficiency and error performance at a given channel condition where the minimum threshold of adaptive modulation is variable according to error performance requirements. We give some numerical examples to show the system efficiency and to verify our analytical results
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