Soft information relaying with transceiver hardware impairments in cognitive networks

This paper demonstrates the impact of transceiver impairments on channel capacity and bit-error-rate (BER) performance of a dual-hop half-duplex cognitive relay network over AWGN channel. We consider the soft-information-relaying (SIR) protocol where the relay node computes the reliabilities (soft) of the received signal from source and then forwards to the destination. The hardware impairment model of the received signal via AWGN channel is first introduced. The analysis on capacity and BER performance are then presented for the network with binary phase shift keying (BPSK) modulation. Furthermore, the impacts of hardware impairments on BER are quantified for the network with SIR and hard decode-and-forward (DF) protocol. The simulation results on channel capacity of the network with SIR protocol acknowledge the ceiling capacity of the realistic transceivers that can not be exceeded by increasing transmit power. Moreover, we found that the BER performance of SIR network with the worst hardware impairment level in 3GPP LTE requirements is on par with the best transceiver level of the network with hard DF. This concludes that the SIR outperforms the hard DF on limit the impact of hardware impairments on BER performance.