Abstract
Single-relay selection techniques based on the max-min criterion can achieve the highest bit error rate (BER) performance with full diversity gain as compared to the state-of-the-art single-relay selection techniques. Therefore, in this work, we propose a modified max-min criterion by considering the differences among the close value channels of all relays while selecting the best relay node. The proposed criterion not only enjoys full diversity gain but also offers a significant improvement in the achievable coding gain as compared to the conventional one. Basically, in this article, an improved bi-directional three-phase single-relay selection technique using the decode-and-forward protocol for wireless cooperative communication networks that enhances the overall network performance in terms of BER is proposed and its performance is proved analytically and through Monte-Carlo simulations. More specifically, the proposed criterion is first used to select the best relay-node. After that the selected relay-node forwards the information symbols of the communicating terminals after performing a digital network coding to minimize power consumptions. In our simulations, we show that our proposed technique outperforms the best-known single relay selection techniques. Furthermore, we prove that the BER results obtained from our conducted simulations perfectly match those obtained from the theoretical analysis.
Highlights
1 Introduction In wireless communication systems, the overall performance and the data rate are highly affected by the multi-user interference and channel impairments such as the time varying fading caused by multi-path propagation [1,2,3,4,5,6,7,8,9]
We will discuss the mathematical model derivation of the bit error rate (BER) of the proposed selection technique using binary phase shift keying (BPSK) modulation under the assumptions discussed in Section 2 earlier
We have assumed a wireless relay network with single-antenna relay nodes and independent flat Rayleigh fading channels where the power is distributed among the two terminals and relays as in [11,12,13], the number of Monte Carlo runs is 1010, the number of relays available in the network varies between two to seven, and the applied modulation technique is either BPSK or 4-QAM
Summary
The overall performance and the data rate are highly affected by the multi-user interference and channel impairments such as the time varying fading caused by multi-path propagation [1,2,3,4,5,6,7,8,9]. Those channel impairments can be mitigated by using distributed beamforming techniques [2,3,4,5,6], distributed space-time-coding techniques [5,6,7,8,9], and relay-node selection techniques [10,11,12,13,14,15,16,17,18,19,20,21,22] Such techniques allow the destination node to receive many copies of the same data signal through different paths and with different amplitudes and phases, which will be combined in a way to improve the overall system performance in terms of the whole network achieved data and bit error rate (BER). Additional improvement is achieved by performing a digital network-coding scheme at the selected relay-nodes, which reduces the power consumption by merging the symbols of the communicating terminals in a single symbol with the same constellation.
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