Theoretical Investigations on Digital Communications Using Noise Carriers

Nowadays lots of efforts have been spent on researching the technique of Ultra-Wideband (UWB) transmission. In stead of using narrow pulses as information bearer, broadband pure noise with Gaussian distribution is also a good candidate to work as a carrier. Two new modulation techniques utilizing noise carrier have been studied in the Telecommu-nication Engineering group at the University of Twente, namely time-offset modulation and frequency-offset modulation. In previous research, a simple receiver structure has been used to retrieve information bits. This proposed signal processing gives rise to the limits of the performance of the system due to the self-interference from the received signal. This requires to develop optimal receivers for these two modulation schemes. In this thesis, the optimal detection problems for these two systems in additive white Gaussian noise (AWGN) channel are investigated. By analyzing the corresponding optimum receiver, the disadvantages of time-offset and frequency-offset systems are pointed out. The numerical results from simulations are used to verify the analytical derivation and analysis. A system applying non-offset scheme with frequency division multiple access (FDMA) technique is proposed in the end.