  We study the theoretical performance of a combined approach to demodulation
and decoding of binary continuous-phase modulated signals under repetition-like
codes. This technique is motivated by a need to transmit packetized or framed
data bursts in high noise regimes where many powerful, short-length codes are
ineffective. In channels with strong noise, we mathematically study the
asymptotic bit error rates of this combined approach and quantify the
performance improvement over performing demodulation and decoding separately as
the code rate increases. In this context, we also discuss a simple variant of
repetition coding involving pseudorandom code words, based on direct-sequence
spread spectrum methods, that preserves the spectral density of the encoded
signal in order to maintain resistance to narrowband interference. We describe
numerical simulations that demonstrate the advantages of this approach as an
inner code which can be used underneath modern coding schemes in high noise
environments.
