Shi Cheng

Date of Graduation

2007

Document Type

Dissertation/Thesis

Abstract

Continuous-phase frequency shift keying (CPFSK) is a type of frequency shift keying (FSK) that maintains phase continuity from symbol to symbol. The bandwidth efficiency of a CPFSK waveform is characterized by its modulation index, number of frequency tones and channel coding rate. These parameters can be flexibly designed to meet different bandwidth and energy requirements in wireless communication systems. One special case of CPFSK, orthogonal FSK, could be applied when bandwidth constraints are loose. By increasing the number of frequency tones, the energy efficiency can be improved at the expense of spectral efficiency. In this dissertation, the general case of orthogonal FSK, orthogonal modulation is first studied. Capacity, convergence behavior and asymptotic error rates of coded orthogonal modulation are analyzed. In addition to coherent detection, we consider noncoherent detection as well, which is one benefit of CPFSK. More often, CPFSK is designed to achieve high spectral efficiency by reducing its modulation index. The general case of nonorthogonal CPFSK is then studied. Capacity, spectral efficiency and capacity approaching code design are discussed for both coherent and noncoherent CPFSK. In addition to the system design and information theoretic issues, channel estimation for noncoherent CPFSK is considered. An iterative channel estimation, demodulation and decoding algorithm is derived using the expectation maximization (EM) algorithm. Finally, we apply noncoherent CPFSK to frequency hopping (FH) networks, leveraging the results acquired throughout the dissertation. Simulations show FH networks with CPFSK modulation and channel estimation can achieve robust performance against partial-band and multiple-access interference.

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