Hybrid RAKE/multiuser receivers for UWB

Abstract

We demonstrate the effectiveness of combining multiple arm RAKE reception with adaptive minimum mean square error (MMSE) combining to combat both narrow and wide band interference in an ultra-wide-band (UWB) pulse-based spread spectrum (SS) communications system. Whether a single user SS UWB system, or a direct sequence SS code division multiple access (CDMA) UWB system, the proposed receiver offers robust suppression of a narrowband interference, in marked contrast to the RAKE only receiver. When DSSS is used with CDMA, this receiver provides much greater rejection of multiuser access interference (wideband interference), avoiding an error floor for moderate system load. RAKE reception alone exhibits an error moderate system load. RAKE reception alone exhibits an error floor even at light system load. The proposed hybrid can be considered an enhancement of RAKE reception, replacing the maximum ration combining the MMSE, or as a reduced complexity alternative to adaptive MMSE multiuser detection.