Ultra wideband (UWB) technology is characterized by transmitting extremely short duration radio pulses. To improve its multiple access (MA) capability, UWB technology can be combined with traditional spread spectrum (SS) techniques. Existing spreading codes are only optimal in additive white Gaussian noise (AWGN) and their performance degrades in multipath fading and narrow band interference. In this paper, we propose the use of spreading codes obtained using a novel design methodology based on genetic programming (GP) and DNA computation for DS-UWB communications. The spreading codes obtained by this novel design methodology performs better than traditional spreading codes in both AWGN and multipath fading. In addition, spreading codes with desired spectral characteristics could be designed to minimize the mutual interference between the DS-UWB and co-existing narrowband systems. The proposed design methodology is attractive for spreading code in terms of performance and flexibility to design spreading codes for a specific design criteria.
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