Performance improvement with limited feedback in PLNC using OSTBC

In this paper, we introduce limited feedback technique into physical-layer network coding (PLNC) protocol using decode-and-forward (DF) and partial-decode-and-forward (PDF) strategies in two-way relay channels consisted of one relay and two end nodes (sources). All nodes are assumed having two antennas to allow transmission by Alamouti´s orthogonal space-time block code (OSTBC) to improve the bit error rate (BER) performance by exploiting diversity. For DF strategy with limited feedback, the closed-form upper and lower bounds on the bit error probability using binary phase-shift keying (BPSK) and quadrature-PSK (QPSK) modulations are derived analytically and approved via computer simulations. Since classical PDF strategy does not satisfy orthogonality at the end nodes, a modified-PDF (MPDF) strategy with limited feedback is proposed for which single-symbol decoding is achieved besides full diversity. The BER performance of MPDF is evaluated via computer simulations for BPSK and QPSK modulations and it is shown that MPDF significantly outperforms the classical PDF.