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.
Highlights
The scarcity of the frequency spectrum resources and the ever-growing demand for new broadband services imposes a need for the bandwidth-efficient transceiver schemes
In case of signal-toUCCI-interference ratio (SIR) = 3 dB, the receivers can perfectly suppress the unknown cochannel interference (UCCI) if the Es/N0 value becomes large. This is due to the fact that after convergence the receivers have enough effective DoFs to separate and detect two desired users’ signals and suppress one UCCI
This behavior can be explained by two reasons: first, increasing the frame length results in more samples for R estimation; second, the feedback becomes more accurate with the increased frame length. It can be seen by comparing the results for τ → 0 and τ → ∞ from Figure 9 that the gain from using receiver 2 is larger if the number of significant multipath components is smaller. This is due to the fact that in the rich multipath environment (τ → 0), the number of effective DoFs is much smaller than the number needed to perfectly suppress the UCCI
Summary
The scarcity of the frequency spectrum resources and the ever-growing demand for new broadband services imposes a need for the bandwidth-efficient transceiver schemes. In the channel-coded systems, the optimal receiver is the one that performs joint equalization and decoding and its complexity is exponential in the product of the number of multipath components and the code memory length. In the case of decision feedback equalization (DFE) combined with STTrCdecoder in an iterative manner, a method for complexity reduction was studied by [12, 13] This method is based on the decoupling between the real and imaginary parts of the received signal, resulting in a reduced total number of equalizer states. A noniterative receiver for detection of STTrC codes in the presence of UCCI was introduced in [23] in frequency-flat-fading channels. (vi) [(·)]m,n, [(·)]m denote the (m, n)th element of (·) if (·) is a matrix and the mth element of (·) if (·) is a vector, respectively
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
