FRAME SYNCHRONIZATION FOR OPTICAL MULTIPULSE PULSE POSITION MODULATION

We investigate frame synchronization algorithms for direct detection m ulti-pulse pulse position modulation (MPPM) optical communication syst ems. The optimal rules (in a maximum likelihood sense) are derived, ap proximations to them that are computationally easier to implement are identified, and upper bounds on the synchronization probability are ob tained. It is seen that the high SNR rules have a performance nearly e qual to that of the ML rules, but provide a significant performance im provement over the simple correlation rules and are virtually as simpl e to implement for a wide range of signal energies. We also address th e problem of designing periodic MPPM synchronization sequences with go od autocorrelation properties, based on a maximum, worst case, peak-to -sidelobe distance criterion. Upper bounds on the peak-to-sidelobe dis tance for such sequences are derived, and a few sequences, generated b y computer simulations, for different synchronization sequence lengths are given.