Spread Spectrum Codes for Continuous-Phase Modulated Systems

TL;DR

This paper analyzes the performance of a combined demodulation and decoding approach for binary continuous-phase modulated signals using spread spectrum codes, demonstrating improved error rates in high noise environments.

Contribution

It introduces a novel combined demodulation-decoding technique with spread spectrum codes for high noise regimes, including theoretical analysis and simulation results.

Findings

Asymptotic bit error rates are improved with the combined approach.

Pseudorandom spread spectrum codes maintain spectral density and resistance to interference.

Numerical simulations show advantages over separate demodulation and decoding in high noise.

Abstract

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.