Investigation On Hybrid Satellite-Terrestrial Relay Systems With Hardware Impairments

The hybrid satellite terrestrial relay system(HSTRS)has been widely employed in the field of navigation and broadcasting for its broad coverage,high communication quality and large channel capacity.However,the practical environment of wireless communication is generally complicated.Communication systems would generate hardware impairments due to the noise of physical-layer,I/Q imbalance and nonlinearities of high-power amplifier,which may restrict the performance of communication systems to some extent.In this context,hardware impairments have become a research hotspot in the field of wireless communication.Therefore,this paper explores the transmission reliability and secrecy outage performance of HSTRS when hardware impairments exist.Relay selection schemes are enhanced to reduce the effect of hardware impairments on the performance HSTRS.The details are as follows:First,the paper investigates the impact of hardware imperfections on the transmission reliability performance of HSTRS.Here,all terminals are equipped with a single antenna and subjected to hardware impairments.A multi-relay selection(MRS)scheme is proposed to enhance the transmission reliability performance of HSTRS.The single-relay selection(SRS)scheme is also considered for comparison purposes.The simulation results show the transmission reliability performance of HSTRS can be enhanced under the MRS scheme with a certain level of hardware impairments at the HSTRS.Then,the effect of hardware impairments on the secrecy outage probability of HSTRS is explored.An optimal relay selection(ORS)scheme is proposed for enhancing the secrecy outage performance of HSTRS against hardware impairments.The round-robin scheduling(RRS)is also considered for comparison purposes.The simulation results show the secrecy outage performance of ORS scheme is better than that of the RRS with a given certain hardware impairments.In addition,the secrecy outage probability of both the RRS and ORS schemes would increase to one at a high signal-to-noise ratio(SNR)when hardware is not ideal.Finally,this paper also studies the impact of hardware impairments on the secrecy outage probability of HSTRS where destination and eavesdropper are equipped with multi antennas,while other nodes are still equipped with a single antenna.In this scenario,this paper considers an effect of the number of user antenna on the secrecy outage performance under the RRS and ORS schemes.The simulation results tell us the secrecy probability will be reduced to some extent when the number of antennas of the destination user is significantly larger than that of the eavesdropper.