Multiuser Detection Techniques for TH-PPM Systems

This paper investigates detection mechanisms for time hopping pulse position modulated multiple access systems in both additive white Gaussian noise environment and fading environment. In such systems, the raw data is not linearly related to the received signal. One technique is to express the pulse position modulated signal as the sum of linearly modulated signals with the input being a nonlinear function of the raw data. This reduces the system to an equivalent pulse amplitude modulated system with significant increase in complexity. We present two new lower complexity detectors. The first detector uses the properties of the pulse correlation matrix to develop a lower complexity detector. The second detector relies on the knowledge of the time-hopping sequence to despread the received signal. The detection is then done on chip-by-chip basis. The performance of these detectors is compared in terms of the probability of at least one user being in error and the average number of correctly decoded users.