Comparison Between Several Methods of PPM Demodulation Based on Iterative Techniques

In this paper we examine demodulation methods for nonuniform Pulse Position Modulation (PPM), which is generated by the crossings of a modulating signal with a sawtooth wave. At high sampling rates (several times the Nyquist), demodulation can be achieved by an appropriate low pass filter of the PPM pulses. However, at sampling rates near the Nyquist rate, this approach creates unacceptable distortion. Here, we are interested in PPM at the Nyquist rate and illustrate the efficiency of iterative methods. Lowering the sampling rate we essentially reduce the bandwidth requirement of the transmitted PPM pulses. Several iterative methods such as Wiley/Marvasti, Time-varying, adaptive weight, Zero-order-hold, Voronoi, linear interpolation algorithms are discussed, where the PPM demodulation is converted as a nonuniform sampling reconstruction problem. Also another approach called the inverse system approach is introduced and the performance of the two algorithms is assessed.