Low-Rate Convolutional Code Applications in Spread-Spectrum Communications

Low-rate convolutional codes are useful as an interference mitigation technique in frequency-hopped spread-spectrum systems. In this paper we show how good low-rate convolutional codes can readily be constructed from higher-rate codes that are known to exhibit good performance. The performance of low-rate convolutional codes is established theoretically and through the use of computer simulation and hardware experimentation. Typical performance curves are shown for convolutional codes with rates between 1/64 and 1/2, both in additive white Gaussian noise and in burst interference. The impact of code rate, constraint length, burst length, interleaving and modulation on total system performance are discussed.