Performance of a near-far resistant adaptive power allocation for physical layer network coding systems

The physical layer network coding (PNC) is proposed to improve data rate by multiple accesses in data relaying networks. In linear networks with PNC, the relay node performs the combination of the relaying data from both end users. Using PNC the data transfer can be completed by two transmissions rather than the four transmissions in conventional linear networks (CLN). Moreover, the adaptive power allocation (APA) scheme can optimize the transmission rate of PNC for relaying communication systems. However, when the relay nodes are deployed with different distance to both of end user nodes, it is called near-far effect (NFE). The NFE degrades the bit error rate (BER) performance with deteriorating the decoding performance of PNC. Therefore, in order to further optimize the transmission power allocation (PA) for both of end user nodes and relaying node we propose a total adaptive power allocation (TAPA) scheme in this paper. With the proposed TAPA scheme, the NFE of conventional PNC systems can be diminished and the BER performance is improved. Simulation results show that the proposed ATPA improves the BER performance especially for the severe NFE environments. Moreover, with desired requirements of BER = 10 ^-3 and severe near far ratio of NFR = 10,15 dB, as compared with the conventional PNC, the proposed TAPA saves the power of 5.9 dB and 10.1 dB, respectively.