Abstract
Iterative multiuser detection in a single-carrier
broadband multiple-input multiple-output (MIMO) system is studied
in this paper. A minimum mean squared error (MMSE) low-complexity
multiuser receiver is derived for space-division multiple-access
(SDMA) space-time trellis-coded (STTrC) systems in
frequency-selective fading channels. The receiver uses MMSE
filtering to jointly detect several transmit antennas of the user
of interest, while the interference from the undetected transmit
antennas, cochannel interference (CCI), and intersymbol
interference (ISI) are all cancelled by the soft cancellation. The
performances of two extreme receiver cases are evaluated. In the
first case, only one transmit antenna of the user of interest is
detected at a time and the remaining ones are cancelled by soft
cancellation. In the second case, all the transmit antennas are
detected jointly. The comparison of the two cases shows
improvement with the latter one, both in single-user and
multiuser communications and in the presence of unknown cochannel
interference (UCCI). It is further shown that in the multiuser
case, the proposed receivers approach the corresponding
single-user bounds. The number of receive antenna elements
required to achieve single-user bound is thereby equal to the
number of users and not to the total number of transmit antennas.