In this paper, we apply iterative detection to typical time hopping (TH) pulse position modulation (PPM) ultra wideband (UWB) spread spectrum systems. Unlike a typical TH-PPM UWB which employs repetition code, the proposed system uses self-encoded code which is updated by user information itself. To take advantage of self-encoded spread spectrum, we apply iterative detection to the TH-PPM UWB system. Simulations are conducted to investigate the bit error rate (BER) performance of the proposed system in additive white gaussian noise (AWGN) channels as well as in fading and multipath channels. We observe a significant BER performance improvement over conventional TH-PPM UWB systems.

Self-encoded spread spectrum (SESS) derives its spreading codes from the random information source rather than using traditional pseudo-random codes. It has been shown that the memory in SESS modulated signals not only can deliver a 3 dB gain in additive white Gaussian noise (AWGN) channels, but also can be exploited to achieve time diversity and robust bit-error rate (BER) performance in fading channels. In this paper, we propose an extension to SESS, namely coded-sequence self-encoded spread spectrum (CS-SESS), and show that it can further improve the BER performance. We describe the CS-SESS scheme and present the theoretical analysis and simulation results for AWGN and fading channels. Iterative detector is developed to exploit the inherent temporal diversity of CS-SESS modulation. The simulation results show that it can achieve the expected 4.7 dB gain with a complexity that increases linearly with the spreading sequence length under AWGN. In Rayleigh fading channel, it can effectively mitigate the fading effects by exploiting the overall diversity gain. Chip interleaving is shown to yield a performance improvement of around 4.7 dB when compared to an chip interleaved direct sequence spread spectrum (DSSS) system.