Research On The Pulse Waveforms Design And Multi-user Detection Of WDMA-UWB Communication Systems

Due to the advantages of ultra-wideband communications include strong anti-interference ability, good concealment, high data transmission rate, simple equipment and low power consumption, the UWB has become a hot research topic. More people study the TH-UWB and DS-UWB, both are similar to traditional CDMA. The waveform division multiple access, as a new multiple access, has many unique advantages. Such as the actual communication rate is high, the synchronization acquisition is easy and the transceivers are simple. This thesis mainly discusses three parts of WDMA-UWB, including the system model of WDMA-UWB, the orthogonal pulse waveforms design and the multi-user detection of WDMA-UWB communication systems.Firstly, UWB system model can be divided into three parts, including transmitter model, receiver model and channel model. The three parts are researched respectively and the signal expressions are presented. Finally, the expression of theoretical bit error rate is deduced. The study of WDMA-UWB system model lays a good fundamental for future research.Secondly, the key issue of WDMA-UWB is the design of orthogonal pulse waveforms. By analyzing the current waveform design methods, Gegenbauer orthogonal polynomials are used for orthogonal pulse waveforms design in this paper. Our studies and simulation results show that the greater order difference of Gegenbauer pulse waveforms the better cross-correlation properties. But the increase of order difference makes the pulse waveforms complicated. In this paper, the method of combined pulse waveforms design based on genetic algorithm is proposed for solving this problem. The genetic algorithm is used for solving combination coefficients. Simulation results demonstrate that thirty pulse waveforms with good cross-correlation properties can be designed by the first twenty Gegenbauer pulse waveforms.Finally, the combined pulse waveforms designed by genetic algorithm can’t restrain multi-access interference completely. The receiver of WDMA-UWB needs multi-user detection technology. A method of MAI suppression based on detection reconstruction and similarity comparison algorithm is proposed for using under the conditions of good cross-correlation properties and small users. This method has good detection performance and low computational complexity. While a MUD algorithm based on the improved hybrid artificial fish swarm is designed to fit on the WDMA-UWB with a large number of users. The improvement by combining artificial fish and simulated annealing algorithm and introducing feedbacking behavior and swallowing behavior is to improve the local search capability, convergence speed, detection accuracy and computational complexity. The simulation results show that this algorithm achieves the bit error rate performance very close to that of OMD under the condition of thirty users in WDMA-UWB system.