Abstract
Abstract We propose a relaying scheme based on superposition coding (SC) with discrete adaptive modulation and coding (AMC) for a three-node wireless relay system, based on half duplex transmission, where each node decodes messages by successive interference cancelation (SIC). Unlike the previous works where the transmission rate of each link is assumed to achieve Gaussian channel capacity, we design a practical superposition-coded relaying scheme with discrete AMC while taking into account the effect of decoding errors at each stage of the SIC process at each node. In our scheme, hierarchical modulation (HM) is used to create an SC message composed of one basic and one superposed message with optimized power allocation. We firstly introduce the proposed scheme without forward error correction (FEC) for high signal-to-noise ratio (SNR) region and provide the optimal power allocation between the superimposed messages. Next, we extend the uncoded scheme to incorporate FEC to overcome bad channel conditions. The power allocation in this case is based on an approximated expression of the bit error rate (BER). Numerical results show the performance gains of the proposed SC relaying scheme with HM compared to conventional schemes, over a large range of SNRs.
Highlights
Cooperative relaying is a recently developed technique that enables to enhance the overall performance of wireless communication systems in terms of transmission rates and coverage by exploiting spatial diversity [1,2]
Since both the optimal power allocation parameter obtained by exhaustive search and the proposed power allocation parameter α S∗C16 obtained numerically from Equation 80 have values less than 0.3, the gap between the approximated and simulated frame error rate (FER) of the basic message is not so large
We have derived the achievable throughput by analysis, taking into account the decoding errors occurring during successive interference cancelation (SIC)
Summary
Cooperative relaying is a recently developed technique that enables to enhance the overall performance of wireless communication systems in terms of transmission rates and coverage by exploiting spatial diversity [1,2]. We consider the three-node wireless relay system composed of one source, one destination, and one relay as shown, where the relay operates according to DF protocol For such a system, authors in [4-6] have proposed cooperative relaying schemes. We first introduce the uncoded SC scheme of [13] with discrete HM, for which we provide here the full analysis for optimizing the power allocation between the two superimposed messages. We extend our uncoded SC scheme in [13] to incorporate FEC technique for overcoming bad channel conditions In this case, due to the difficulty to derive a theoretical formula for the bit error rate (BER) of decoded messages, we make use of an approximate expression of the BER to perform power optimization.
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