  Pulse position modulation (PPM) is a popular signal modulation technique
which creates M-ary data by means of the position of a pulse within a time
interval. While PPM and its variations have great advantages in many contexts,
this type of modulation is vulnerable to loss of synchronization, potentially
causing a severe error floor or throughput penalty even when little or no noise
is assumed. Another disadvantage is that this type of modulation typically
offers no error correction mechanism on its own, making them sensitive to
intersymbol interference and environmental noise. In this paper we propose a
coding theoretic variation of PPM that allows for significantly more efficient
symbol and frame synchronization as well as strong error correction. The
proposed scheme can be divided into a synchronization layer and a modulation
layer. This makes our technique compatible with major existing techniques such
as standard PPM, multipluse PPM, and expurgated PPM as well in that the scheme
can be realized by adding a simple synchronization layer to one of these
standard techniques. We also develop a generalization of expurgated PPM suited
for the modulation layer of the proposed self-synchronizing modulation scheme.
This generalized PPM can also be used as stand-alone error-correcting PPM with
a larger number of available symbols.
