Orthogonal Spatial Multiplexing Research Articles

Behavior of the Minimum Euclidean Distance Optimization Precoders with Soft Maximum Likelihood Detector for High Data Rate MIMO Transmission

The linear closed loop Multiple-input Multiple-output (CL-MIMO) precoding techniques characterized by the channel state information knowledge (CSI), at both sides of the link, aims to improve information throughput and reduce the bit error rate in the communication system. The processing involves multiplying a signal by a precoding matrix, computing from the CSI with some optimized criteria. In this paper, we proposed a new concatenation of the precoders optimizing the minimal Euclidean distance with soft Maximum Likelihood (soft-ML) detection. We analyze the performance in terms of bit error rate (BER) for the proposed association with the three well-known quantized precoders: Maximum of minimum Euclidean distance (Max-dmin) precoder, Orthogonalized Spatial Multiplexing precoder (POSM), and Orthogonalized Spatial Multiplexing (OSM) based on the same criteria, in coded MIMO system over a Rayleigh fading channel, using Quadrature Amplitude Modulation (QAM). Simulations show the interest of the proposed association of the dmin-based precoder with a soft - Ml detector, and the best result is achieved for Max-dmin precoder.

Robust train-to-wayside video communications in tunnels using H.264 error-resilient video encoding combined with multiple antenna systems

With the development of driverless metro systems, the demand for high data rate train-to-wayside wireless transmission is increasing drastically in order to satisfy operational needs such as maintenance, video surveillance of the inside of the trains and passenger information. Thus, the association of new transmission techniques such as new video coding techniques, multi antennas at transmission and reception sides and recent precoders provides technically and economically efficient solutions to improve existing systems. This paper presents and evaluates two novel strategies to enhance train-to-wayside wireless video transmissions in tunnels using realistic channel models obtained with ray tracing previously experimentally validated. Multiple Description Coding (MDC) or Region Of Interest (ROI) coding, using the new Flexible Macroblock Ordering (FMO) technique, is combined with appropriate Multiple Input Multiple Output (MIMO) schemes, namely, spatial multiplexing (SM), orthogonal spatial multiplexing (OSM) and precoded orthogonal spatial multiplexing (P-OSM) depending if full channel state information at transmitter side (CSI-T) is available or not. For each strategy, both video encoding process and MIMO algorithm are combined in an efficient way to provide the best video quality at the receiver with no increase of the number of radio access points along the infrastructure.

Exact Symbol Error Rate and Diversity Analysis of Orthogonalized Spatial Multiplexing Systems with Optimal Precoding

Orthogonalized spatial multiplexing (OSM) systems with optimal precoding, denoted by POSM, was recently proposed which allows a single-symbol decodable maximum likelihood receiver in closed-loop multiple-input multiple-output (MIMO) systems. It was shown that the performance of the POSM is identical to that of the optimal closed-loop MIMO system in terms of the minimum distance. In this letter, we derive an exact symbol error rate (SER) expression of the POSM for 4-QAM and 16-QAM in Rayleigh fading channels. By using polar coordinates and the singular value distributions, the final expression of the SER can be evaluated with a single-integral form. Also, in the high SNR regime, we obtain a simple average SER expression of the POSM which shows that the POSM with two transmitting antennas achieves full diversity. Simulation results confirm the accuracy of our derived analysis.

Optimal precoding for orthogonalized spatial multiplexing in closed-loop MIMO systems

In this paper, we propose a new precoding algorithm for orthogonalized spatial multiplexing (OSM) systems over flat-fading multiple-input multiple-output (MIMO) channels. The OSM scheme was recently introduced for closed-loop MIMO systems which allows single symbol decodable maximum likelihood detection. To further improve the performance of the OSM system, we propose a new precoding method by maximizing the minimum Euclidean distance between constellation points in the effective channel. In order to efficiently identify the parameters of a precoder which maximizes the minimum distance, we introduce a partitioning approach. Through analysis, it is shown that one real value parameter and two bits are required for feedback information for precoding in 16-QAM systems. Simulation results demonstrate that our algorithm provides 9 dB and 7.5 dB gains at a bit error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-4</sup> over the conventional OSM systems for 4-QAM and 16-QAM, respectively. We also confirm that the performance of the proposed scheme is the same as that of the optimum closed-loop MIMO systems in terms of the minimum distance. Consequently, our precoding algorithm significantly improves the system performance with a small increase of feedback amount.

Optimal Downlink Space-Time Scheduling Design With Convex Utility Functions—Multiple-Antenna Systems With Orthogonal Spatial Multiplexing

It is well known that link level throughput could be significantly increased by using multiple antennae at the transmitter and receiver without increasing the bandwidth and power budget. However, optimizing the link level performance of multiple-antenna systems does not always imply achieving system level optimization. Therefore, cross-layer optimization across the link layer and the scheduling layer is very important to fully exploit the temporal and spatial dimensions of the communication channel. In this paper, we consider the optimal downlink space-time scheduling design for a general class of convex utility functions. The access point or base station is equipped with n/sub T/ transmit antennas. There are K mobiles in the system with a single receive antenna. For practical reasons, we assume zero-forcing processing at the physical layer of the base station and mobile. We will apply the design framework to two common utility functions, namely the maximum throughput and the proportional fair. The cross-layer scheduling design is a mixed convex and combinatorial optimization problem and the search space of the optimal solution is enormous. Greedy algorithm, which has been widely used in today's wireless data systems (3G1X, high data rate system (HDR), Universal Mobile Terrestrial Service), is optimal when n/sub T/=1. However, we found that there is a large performance penalty of greedy algorithms (relative to optimal performance) when n/sub T/>1 and this motivates the search for more efficient heuristics. In this paper, we will address genetic-based heuristics and discuss their complexity-performance tradeoff.