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

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-by- antenna (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.     

Measurement Data-Based Link-Level and System-Level Simulations for Single Carrier SC/MMSE MIMO Turbo Equalization Technique

Current advances in multi-dimensional channel sounding techniques make it possible to evaluate performances of signal processing algorithms in realistic conditions. By using channel impulse response measurement data collected in the real fields, link-level performances of signal transmission techniques in the fields such as bit error rate (BER) and frame error rate (FER) performances can be evaluated. This technique is called link-level simulation. Through statistical analysis of link-level simulation results, system-level performances of the techniques such as geographical distribution of BER and FER in the area of interest can also be evaluated. This technique is called system-level simulation. This paper focuses on link- and system-level performances of a multiple-input multiple-output (MIMO) Turbo Equalizer in real fields. Methodologies for the link- and system-level simulations using field measurement data are first presented. Results of link- and system-level simulations using two-dimensional channel sounding field measurement data collected in Tokyo are then presented. This revised version was published online in August 2006 with corrections to the Cover Date.     

Multilevel-coded QAM with MIMO turbo-equalization in broadband single-carrier signaling

A new scheme employing multilevel coded bit-interleaved transmission allowing for efficient turbo-equalization is proposed for multiple-input-multiple-output (MIMO) broadband single-carrier signaling. The proposed scheme is based on block-partitioned hierarchical constellations and offers robustness in data throughput efficiency against varying spatio-temporal characteristics of fading channels. The proposed scheme is compared to a standard bit-interleaved-coded-modulation (BICM) system in frequency-selective channels, and found to offer better overall throughput. It is also shown that level-wise retransmission control with the proposed multilevel single-carrier signaling scheme can offer further throughput improvement. Channel measurement-based simulations are used to evaluate performances of both schemes in real fields. Channel parameter analysis using a superresolution technique is performed to clarify the underlying reasons for the performance characteristics of the systems.