Iterative Frequency Domain Joint-over-Antenna Detection in Multiuser MIMO

Abstract

Multiuser multiple-input-multiple-output (MIMO) wireless systems have great potential in improving information rate, diversity and resistance to against interference. The primary objective of this paper is to derive for broadband signaling a new iterative frequency domain (FD) multiuser MIMO signal detection technique for joint-over-antenna (JA) detection. The proposed detector is based on soft-cancellation and minimum mean square error (MMSE) filtering, followed by maximum a posteriori probability (MAP) detector to detect several of each users transmit antennas. The purpose of jointly detecting several transmit antennas is to preserve the degrees of freedom (DoF) for MMSE. Computational complexities with FD and its time domain (TD) counterpart are evaluated in this paper, and it is shown that FD requires significantly lower complexity than TD. Numerical results show that JA significantly outperforms the receiver that detects transmit antenna signals antenna-byantenna (AA). The proposed iterative FD JA technique achieves larger performance gains compared to AA when the total number of transmit antennas is larger than the number of receiver antennas, as well as in the presence of spatial correlation.Index Terms-Multiuser MIMO, spatial multiplexing, turbo coding, iterative processing, frequency domain equalization.

Iterative frequency domain equalization for single-carrier wideband MIMO channels

“…Lagrangian vectors and the corresponding scalar constraints (Lagrangian function) can be written as 3 The mitigation of inter-stream interference originated from other antenna stream's spatial interference and inter symbol interference (ISI) resulted from frequency selectivity is done optimally with this structure. This differs from previous MIMO studies in [7], [8] and [9] which use spatial interference suppression techniques based on successive interference cancellation (SIC).…”

“…We, furthermore, derive the jointly optimal forward and backward filters in the frequency domain so that the complexity advantage of FDE is not compromised. Since reliability of coded symbols from the decoding process are used in deriving the optimal forward and backward filters, the filters employed in this work have a different structure from that of previous interference-cancellation-based MIMO turbo equalizers, such as in [7], [8] and [9]. Third, the MIMO wideband channel can be quasi-parallelized with the help of our proposed space-frequency equalizer and so, the code construction techniques achieving optimal rate-diversity tradeoff given by the singleton bound for block-fading channels [10], [11] can be effectively used such that the proposed equalization scheme combined with this type of coding structures yields a very close performance to the MIMO-OFDM outage probability and hypothetical matched filter bound (MFB) [12].…”

Iterative ("Turbo") Multiuser Detectors for Impulse Radio Systems

“…Note that the structure of the pulse-symbol detector is similar to the joint-over-antenna turbo receiver in [18], which employs multiple turbo loops for each antenna, by considering "composite" modulation for multiple antennas as the inner code, and channel coding for different users as the outer code. The main differences are that, for the pulse-symbol detector, the outer code is a simple repetition code, while the inner code is a binary phase shift keying modulation, and that there are also TH and polarity randomization operations in the pulse-symbol detector, which randomize the positions and the polarities of the pulses in different frames.…”

“…Iterative multiuser detectors can be designed for TH-IR systems by considering the TH-IR signaling structure as a concatenated coding system, where the inner code is the modulation and the outer code is the repetition code. Such a technique makes use of the similarity between TH-IR signaling and bit interleaved coded modulation (BICM), where the inner code is modulation and the outer code is channel coding [2], [6], [18], [36].…”

Linear and Nonlinear Time Domain Block Equalizers on MIMO Frequency Selective Channels

“…On the other hand, SC transmission with the same transmission bandwidth as OFDM is able to have much shorter symbol duration than OFDM and the short time block transmission with small number of symbols is strong against time selective fadings. In [4], Turbo encoded MIMO SC transmission scheme is introduced. The authors used the FDE to cancel the ISI and IAI by decomposing the frequency selective channel to the flat Rayleigh fading channel accommodated at each frequency index.…”