Abstract
In this paper, we study the performance of the four-node multiple-access relay channel with binary Network Coding (NC) in various Rayleigh fading scenarios. In particular, two relay protocols, decode-and-forward (DF) and demodulate-and-forward (DMF) are considered. In the first case, channel decoding is performed at the relay before NC and forwarding. In the second case, only demodulation is performed at the relay. The contributions of the paper are as follows: (1) two joint network/channel decoding (JNCD) algorithms, which take into account possible decoding error at the relay, are developed in both DF and DMF relay protocols; (2) both perfect channel state information (CSI) and imperfect CSI at receivers are studied. In addition, we propose a practical method to forward the relays error characterization to the destination (quantization of the BER). This results in a fully practical scheme. (3) We show by simulation that the number of pilot symbols only affects the coding gain but not the diversity order, and that quantization accuracy affects both coding gain and diversity order. Moreover, when compared with the recent results using DMF protocol, our proposed DF protocol algorithm shows an improvement of 4 dB in fully interleaved Rayleigh fading channels and 0.7 dB in block Rayleigh fading channels.
Highlights
In cooperative communications systems, idle nodes have the capability to relay information from other active nodes
It is shown that channel state information (CSI) quantization errors affect both coding gain and diversity order
8 Conclusion In this paper, we have studied the performance of the multiple access relay channel with binary Network Coding and joint network/channel decoding (JNCD) at the destination in practical situations
Summary
Idle nodes have the capability to relay information from other active nodes. In [7,8], it has been shown that, compared to conventional distributed turbo coding and separate network and channel decoding, JNCD can improve the performance of canonical two-way and multiple-access relay channels These results assume that only correct packets are forwarded from the relay to the destination. All these papers assume that CSI and decoding error probability at the relay are available at the destination, which is not always true in practical wireless systems It is shown in [19,20] that imperfect CSI can significantly degrade the performance of cooperative systems. The contributions of the paper are as follows: we show that JNCD provides better performance than separate network channel decoding only if the destination has enough knowledge of the decoding error probability at the relay; in addition, this gain will be larger as the number of fading blocks per codeword increases. N (index is ignored for simplicity) is the noise vector whose components are circularly symmetric zero-mean complex Gaussian random variables with power spectrum density equal to σn, nk ∼ CN(0, σn2)
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