Research On Physical-layer Secure Wireless Communication

With the rapid evolution of mobile communications network, except for transmission rate, network stability, portability of mobile devices and security of wireless links have attracted more and more interest and attention from researchers all over the world. Often-used physic-layer se-curity methods include optimal beam-forming/precoding strategy, artificial noise (AN) approach as well as relay transmission. Besides, approach of adding cooperative jammer (CJ), combination of cryptographic algorithms and wireless channel properties and antennas selection in transmitter have also been mentioned. Based on MISO (Multiple-antennas transmitter Single-antenna re-ceiver) model, this paper proposed a novel way of guaranteeing wireless security using random phases in transmitter.With reference to traditional Application-layer cryptographic methods and general Physical-layer strategy of achieving wireless security under MISOME, MIMOME model, our paper pro-posed a new approach of random signal phases and amplitude controller in transmitter under MISO-OFDM system. In our proposal, signal phase of each access point in transmitter is ran-domly chosen and corresponding signal amplitude is adjusted to enhance randomness and in-dependency of transmit signals. First, the author investigated how channel correlation factor p, number of antennas in transmitter Nt will affect secrecy rate under both 16QAM discrete input and Gaussian input. Average transmission power with random phases and fixed phases in trans-mitter under random and static channels respectively were explored as well. Finally, we clarified strategy of minimizing transmission power in transmitter, analyzed secrecy rate under minimal power as well as maximal power constraint separately.Furthermore, this graduate thesis compared results of our proposal with that of AN approach w.r.t Bit Error Rate (BER) in eavesdropper as well as secrecy rate under different Carrier Noise Ratio (CNR) and channel correlation. Simulation results showed that the novel random phase approach can achieve comparable BER performance with AN approach under low correlation and higher secrecy rate than AN ap-proach under high correlation only if correlation factor is not 1.0.