Performance analysis and comparison of different multirate TH-UWB systems: uncoded and coded schemes

Multirate time hopping ultra wideband (TH-UWB) communication systems are considered where each user can have several multirate services. Three methods named as parallel mapping, serial mapping with variable spreading factor, and multicode using Walsh subcode concatenation schemes are investigated. In the parallel mapping method, one kind of signature code (PN code) is used to distinguish users and their diverse services alike. For the serial mapping with variable spreading factor scheme, one signature code is assigned to each user and different services send their data in distinct frames. Whereas in the multicode using Walsh subcode method, different users and different services of the same user are distinguished through two kinds of signature codes, namely PN codes and Walsh codes, respectively. The performance of these three multirate TH-UWB systems is evaluated and compared for both uncoded and coded schemes in synchronous AWGN channel using conventional single user correlator receiver. The analytical and numerical results indicate that while the multicode using Walsh subcode structure outperforms the other structures in the uncoded system, the parallel mapping method performs the best for the coded scheme. The results also show that even though the coded scheme considered requires the same bandwidth as the uncoded scheme, the coded scheme significantly outperforms the uncoded scheme for all three multirate structures.