Iterative MIMO Turbo Multiuser Detection and Equalization for STTrC-Coded Systems with Unknown Interference

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.

On the MMSE Criterion for Space-Time Coded Signaling in the Presence of Unknown Interference

“…Two JA-MMSE criteria, A-Criterion [3] and HCriterion [2,4], were presented independently in different literatures. As described in Section 1, the primary purpose of this letter is to provide comparative assessments to JA-MMSE using those different criteria.…”

“…Following the mathematical derivation process shown in [3], we can easily obtain the ith, 1 ≤ i ≤ m, column of the optimal solution of matrix pair W A and A, as…”

“…In ST-coded systems, receiver has to be equipped with multiple receive antennas if unknown interference (UKIF) components have to be suppressed while detecting the desired ST-coded signals. To preserve the ST-coded signal structure while suppressing the interference, joint-over-antenna (JA) detection techniques based on the minimum mean-squared error (MMSE) criterion have been introduced for channels without frequency selectivity in [2] and with frequency selectivity in [3,4]. Two different criteria for MMSE spatial filtering have been proposed for this purpose; one is to minimize the mean-squared error (MSE) between the spatial filter output and the actually received composite signal comprised of the desired ST-coded signals [2,4], which is referred to as HCriterion in this letter, where H represents the actual channel matrix; the other is to minimize the MSE also between the two terms but the desired signal term should not necessarily be actually received composite signal [3], referred to as ACriterion, where A represents an equivalent channel matrix; they were presented independently in different publications.…”

Groupwise Frequency Domain Multiuser MMSE Turbo Equalization for Single Carrier Block Transmission Over Spatially Correlated Channels

“…To overcome this performance degradation, groupwise turbo equalization [15], [16] can be employed that combines SC-MMSE filtering and optimal MAP detection.…”

Turbo Equalization For Space-Time Block Coded FWA Systems

“…Moreover, only a single-input, multiple-output system (for a single user) is considered in [14]. The turbo multiuser detection technique previously proposed in [10] is extended to STBC and STTC coded systems in [15][16][17] for flat-fading channels and frequency-seletive fading channels, respectively. In [18], the STBC originally developed for flat fading channels is generalized for frequency selective channels, where the transmitted signals are coded on a block-to-block basis rather than a symbol-by-symbol basis.…”