Sequence detection and equalization for pulse-position modulation

We propose several strategies for detecting digital pulse-position modulation (PPM) in the presence of intersymbol interference and additive white Gaussian noise. We develop an equivalent vector channel by viewing PPM as a binary block code, and use this vector channel to derive the maximum likelihood (ML) sequence detector. We also propose three sub-optimal block-by-block detectors, all of which use block decision-feedback equalization (DFE) to mitigate inter-block interference, but differ in how they mitigate intra-block interference: the ML-BDFE accounts for it in an optimal way, the comparator-BDFE uses linear equalization, and the correcting-scalar-DFE uses DFE. We illustrate low-complexity implementations of these equalizers, and compare their performance to the ML detector using Monte-Carlo simulations