Performance Analysis And Effect Of Multi-user Interference For Ultra Wideband Communications

Ultra-Wideband (UWB) is an upcoming technology for short-range high data rate applications like Wireless Personal Area Networks or medium/long-range low data rate applications like sensor networks. UWB has many captivating characteristics such as very short duration pulses (order of nanoseconds), multipath channel, large instantaneous bandwidth and time hopping pulse trains resulting in coexistence with the existing narrow band users. The Ultra Wideband communication systems employ the technique of Impulse radio of transmitting short duration pulses which result in extremely wide bandwidth and many performance benefits. Since UWB systems operate in dense multipath environments, RAKE receiver is the optimum choice for the receiver. Considering the evolving nature and the wide applications of this technology, it is important to analyze the system performance for different scenarios including the multi-user environment. My thesis mainly targets the analysis of the bit error rate (BER) performance of the time hopping pulse position modulation (TH-PPM) UWB system with the use of Ideal Rake Receiver and the performance degradation when the Selective and Partial Rake receivers are employed. I have also analyzed the effect of changing the repletion code length on the performance. The performance analysis is carried out for varying the modulation index M by employing 4-PPM instead of Binary PPM and simulation results show that 4-PPM offers a worse performance to the binary PPM case. Furthermore, I have evaluated the performance in the presence of Multi-user Interference using the Standard Gaussian Approximation. Finally, the performance of employing M-ary PPM in the multi-user scenario is also evaluated. The simulations are performed under the assumption of perfect channel knowledge. The IEEE UWB indoor channel model is used for Non Line of Sight (NLOS) Case C, which is for 4 to 10 m distance between the transmitter and the receiver.