Research On Multi-user Combined Detection For TH-UWB

While UWB system improves the resource utilization by sharing the same channel for multiple users, multiple access interference is introduced, which will seriously affect the performance of receiving. Multi-user detection technology can effectively reduce multiple access interference, and improve detection performance. The application of multi-user detection technology is one of the hot spots of current research.TH-UWB based on pulse amplitude modulation and TH-UWB based on pulse position modulation are introduced at first. In the single user TH-UWB system, the performance of two systems is compared, and the research object of this paper is based on the pulse amplitude modulation.Then, several multi-user detection algorithms: matched filter detection, linear detection and nonlinear detection are studied based on the mathematical model of PAM-TH-UWB. The structure of traditional matched filter detection algorithm is simple, but the detection performance is poor in the system, which is hard to meet the requirements of engineering applications. Linear detection includes decorrelating detection and minimum mean square error detection. They are both related to the matrix inversion. In the case of large number of users, computation complexity is still high. Because using an iterative technique, parallel interference cancellation detection has the defects of error extension. Therefore, to solve this problem, two improved algorithms binding PIC multi-user detection with DEC and MMSE respectively are proposed. Simulation results show that the proposed methods are superior to the traditional parallel interference cancellation multiuser detection, and the parallel interference cancellation multi-user detection algorithm based on MMSE is best.Finally, ultra wide band multi-user system model based on time diversity is established. On this basis, several corresponding improved algorithms from setting different weighing coefficients and reducing the computational complexity are proposed. By setting the weighing coefficients, there have three improved algorithms which include maximal ratio combining based on the number of interference users, selective combining in view on the pulse conflicts and maximal ratio combining based on the collision probabilities. The simulation results show that the performance of maximal ratio combining based on the collision probabilities is best among three kinds of improved algorithms. To reduce computational complexity, two low-complexity algorithms which include low-complexity DEC detection and low-complexity MMSE detection are proposed. The results prove that these two methods can effectively reduce the computational complexity in the context of maintaining the performance of the system,and the performance of low-complexity MMSE multi-user detection is best.