Research On Multi-user Detection Technology For Th-uwb Wireless Communication System

In recent years, with the rapid development of short-range wireless communications, Impluse Radio Ultra-wideband technology (IR-UWB) has become one of the cutting-edge communicaton technologies and attracted widespread attention in various research institutions and standardization organizations, due to its high data rate, large capacity, strong anti-multipath ability, simple system structure. However, in the practical application of UWB systems, Multiple Access Interference (MAI) caused by the correlation of each user's time-hopping sequence, reduces the system capacity, generates near-far effect, and becomes the main interference in multi-user UWB systems. Thus, MAI affects the performance of UWB systems severely.In this paper, proceeding from the impacts caused by MAI, two different UWB systems based on Gaussian white noise channel and the modified S-V channel model recommended by IEEE802.15.3 are established. Based on the two simulation system models, an in-depth and comprehensive study is conducted to improve the anti-MAI ability and to reduce the complexity of system implement.Firstly, a kind of interative multi-user detector based on interference cancellation and Gaussian approximation is proposed by studying anti-multi-multiple-access interference in Gaussian channel environment. This detector is divided into two parts and the soft information reflecting the bit credibility interates between these two parts. In addition, an inteference cancellation algorithm is used to improve the accuracy of transmitting information, and a Guassian approximation implementation is used in the remaining inteference, to reduce the complexity of the algorithm.Secondly, a partial inteference cancellation algorithm is presented by studying anti-multi-multiple-access interference in the modified S-V multipath channel model environment. In order to apply the interative structure to UWB systems, the received signals of TH-UWB systems in the multipath channel are analyzed, the interative structure in Gaussian channel environment is extended by using the received signals, and then the estimated inteference is multiplied by a weighting factor valued between 0 and 1, to improve its accuracy and the detection performance of UWB systems. Ultimately, the selection method of weighting factor is derived.Finally, The interference cancellation and Gaussian approximation algorithm is assessed using simulations in Gaussian white noise channel environment and the partial interference cancellation algorithm is assessed using simulations in the modified S-V channel environment. The simulation results show that the interative multi-user detectors based on these two algorithms have a low complexity of implementation, a good performance of system, a strong ability of anti-MAI, etc. Thus, the detector has an excellent applied value.