In this dissertation, I investigated two problems in wireless communication system designs: jamming optimization and transmission in high mobility systems.
In the first part (Chapter 2), I studied the impact of joint partial-band, partial-time jamming on a multicarrier asynchronous direct-sequence code-division multiple access system in a Rician fading environment. I analyzed two different subcarrier combining and decoding schemes. In addition, I studied two types of partial-time jamming modes: equal probability jamming on each symbol, and burst jamming with interleaving. I showed that with interleaving, the two partial-time jamming modes have identical performance on average. I then derived an easy-to-evaluate upper bound on the system’s bit-error-rate performance, and used it to determine the optimal jamming strategy for the joint partial-band, partial-time jammer. I discussed the strategy to optimally choosing partial-band and partial-time jamming parameters based on available jamming power, known channel statistics, and system parameters.
In the second part (Chapter 3), I considered using noncoherent transmission as an alternative to coherent transmission in fast fading environments. I compared the performances of coherent signaling using pilot-symbol assisted modulation and noncoherent signaling based on star-quadrature amplitude modulation constellations. The throughput performances of coherent transmission and noncoherent transmission in fast fading environments were compared. For coherent transmission, both fixed pilot insertion pattern and adaptive pilot insertion pattern were studied. Both fast fading channels with fixed Doppler spread and varying Doppler spread were considered. I considered the situations when noncoherent transmission can outperform coherent transmission, and the feasibility of having adaptive pilot insertion pattern in coherent systems.