New Convolutional Encoders for Spectral Line Suppresion in Pulse Position Modulated Time Hopping Impulse Radio Ultra Wideband Systems

The topic of spectral line suppression is of major interest in the design of pulse position modulated (PPM) time hopping impulse radio (TH-IR) ultra wideband (UWB) communications systems. Previously pseudo-chaotic time hopping (PCTH) has been introduced to eliminate spectral lines as well as improving bit error rates. In this paper six new convolutional encoders are introduced that have the same constraint lengths and power spectral characteristics as those used in PCTH but with better binary free distance. BERs for hard decision Viterbi decoding are also improved upon by the computation of branch metrics based on the m-ary symbols rather than their binary representations.