Özet:
In this thesis, we consider the user cooperation in ultra-wideband (UWB) systems characterized by severe frequency selective channels. To circumvent this problem we present a space-time (ST) coded UWB system employing the multiband orthogonal frequency division multiplexing (MB-OFDM). Space-time coded cooperation (STCC) is subject to error floors due to hard-decision detection errors in between users. For this reason we propose a soft-information aided cooperation mechanism which lower the error floor significantly. Adding iterative decoding to partners improved the performance further. We also proposed a cyclic redundancy check (CRC) employed system to decide on cooperation. The simulation results and comparisons with the single user case indicate that the proposed user cooperative UWB transceiver architectures have significantly improved error floor and bit-error rate (BER) performance.
