Multiuser receivers for DS-CDMA UWB

We demonstrate the effectiveness of multiuser detection for an ultra-wideband (UWB) pulse based direct sequence spread spectrum system using code division multiple access. Extensive simulations were run using channel soundings of the 2-8 GHz band collected in a residential setting and characterized by a high level of multipath fragmentation. We show that adaptive minimum mean square error (MMSE) multiuser detection (MUD) receivers are able to gather multipath energy and reject intersymbol and interchip interference for these channels to a much greater extent than RAKE receivers with 4 and 8 arms. We also demonstrate that the adaptive MMSE is able to reject an IEEE 802.11a OFDM interferer, even for SIR as severe as -30 dB. The adaptive MMSE exhibits only a 6 dB penalty in the 16-user case relative to the single user case. The practical RAKE receivers were incapable of effectively rejecting either strong narrowband interference or heavily loaded wideband interference. Even more moderate levels of interference caused significant performance degradation of RAKE receivers.