On optimum system design for wireless communications
Date
2018-07-19
Authors
Wu, Bo
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Abstract
This dissertation addresses the issue of optimum system design to achieve reliable
communication in the presence of various types of interference. Multiobjective
formulation is used with noncooperative and cooperative approaches owing to the
nature of the problems under consideration.
Since intentional Jamming is one of the most severe kinds of interference, anti-jam
techniques are crucial for communications in a hostile environment. The jam
and anti-jam problem is modeled as a two-person zero-sum game in which the communicator and the jammer have antagonistic objectives and are viewed as the two
players. The concept of Nash equilibrium is introduced and its characterizations
such as existence, uniqueness, stability, robustness, and sensitivity are investigated.
This model is then applied to a frequency-hop spread spectrum M-ary frequency-shift-keying system where ratio-threshold diversity is used to combat partial-band
noise and multitone jamming. Equilibrium performance in terms of cutoff rate and
bit error rate is shown to be superior to that predicted by worst-case analysis.
When mutual interference caused by simultaneous transmissions is the major
concern in a heterogeneous packet network, a multiobjective framework is proposed
in this dissertation with the objectives and constraints of the individual users taken
into consideration. Near-far effect and Rayleigh fading may occasion packet capture
and therefore create unfairness in favor of closer users. Thus, multiobjective
optimality is introduced, in which criterion of fairness is embedded. Optimum
strategies controlling transmission probability and/or power are examined to yield
the Pareto optimal solution in a slotted ALOHA network. Then, the same control
strategies are studied with the channel utilization being the maximization objective.
Optimization results are obtained in various situations, and effectiveness of
different strategies is compared.
A multimedia direct-sequence spread spectrum system may support multiple
services with different transmission rates and diverse quality-of-service requirements. To facilitate multimedia applications and maximize the system capacity,
average power control, error correction coding, and time diversity are incorporated
into the system. The capacity of such a system is evaluated in multipath Rayleigh
fading channels. Average bit error rate, outage probability, and corresponding information theoretic bounds are discussed. Concatenation of Reed-Solomon codes
and convolutional codes is considered for error correction to account for different
quality and delay constraints. It is shown through a numerical example that the
system capacity can be increased significantly by an appropriate system design.
Description
Keywords
Mathematical optimization, Wireless communication systems