Congratulations to Mr. Pang-Cheng (Brian) Lan for passing his Qualifying Exam on January 22, 2015. The title of Brian’s thesis proposal is “Enhancing Secrecy in Wireless Environment with Only Channel State Information: Theory and Applications”. His Qualifying Exam committee consisted of Jay Kuo (Chair), Keith Chugg, Andy Molisch, Salman Avestimehr and Wlodek Proskurowski (Outside Member).
In his proposal, Brian shows the advantages of having only transmitter-side channel state information (CSI) but none or limited CSI at the receiver and the eavesdropper in wiretap channels. With CSI only at the transmitter (CSIT), distortion and interference on the main channel can be pre-compensated by the transmitter to facilitate detection at the receiver while leaving the eavesdropper confused by the uncertainties of its own channel. These ideas are first tested in the case of finite-alphabet discrete memoryless wiretap channels, where the secrecy capacity expression is derived, and are then applied to two practical scenarios, namely, fading wiretap channels and those with Gaussian interference. Truncation-based schemes are proposed to ensure that the transmission occurs only when the main channel is sufficiently reliable. Furthermore, a practical unitary modulation scheme is recommended as application of exploiting the benefits of having CSIT in secrecy for multi-antenna communication systems in which Long Term Evolution (LTE) is used as an example. The achievable secrecy rates of the proposed schemes are derived and asymptotic or approximate expressions are proposed for the optimization purpose. The effectiveness of the proposed transmission schemes and the advantages of having only CSIT are demonstrated through numerical simulations.