Thesis

Simultaneous channel utilization: a frequency notching approach

Many spectrum utilization challenges have arisen from the increased demands of wireless data transmission with limited spectral bandwidth. One of these challenges includes simultaneous channel utilization which results in interference between local communication systems. It has become essential to examine potential techniques available to maximize channel utilization efficiency by allowing simultaneous transmissions on a shared band of frequencies. This report presents the technique of frequency notching that can be used to efficiently solve the simultaneous channel utilization problem. In this report the frequency notching system is confirmed to be an effective simultaneous channel utilization technique and a possible efficient solution to the unintentional interference problem caused by multiple communication systems operating in close proximity to a high power transmitter. The effects of frequency notching on signal acquisition, detection and degradation of two simultaneous shared channel signals are examined. The bit error performance of the frequency notched system is determined as a function of both the notch bandwidth and location within the spread spectrum band. It is proven that the BER degradation is within the acceptable limits for a notch filter implemented towards the beginning or at the end of the main lobe, occupying less than 20% of the available spectrum. In addition, the data rate limitations on the narrow-band signals, operating within the notch filter frequency band were determined to be directly proportional to the ratio of energy per bit to the noise power spectral density(E_b⁄N_0 ).

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