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Physical transceiver implementations for multiple-input multiple-output (MIMO) wireless communication systems suffer from transmit-RF (Tx-RF) impairments. In this paper, we study the effect on channel capacity and error-rate performance of residual Tx-RF impairments that defy proper compensation. In particular, we demonstrate that such residual distortions severely degrade the performance of (near-)optimum...
We report on the feasibility of using the multiple modes of a MMF for MIMO processing with the goal to increase the transmission capacity by mode-multiplexing. Experimental results up to a 3×3 MIMO system are shown and the limitations as well as the potential of this technique are discussed.
This document describes the design of received signal strength indicators (RSSI) for RF-MIMO systems. It covers considerations of system level aspects such as dynamic range and the suiting location of the RSSI and presents the implementation of a fully integrated RSSI circuit for 802.11a compliant diversity receivers. Drawing a total current of 6.1 mA from a 3.3 V supply, this circuit provides a dynamic...
Recently, lattice-reduction (LR) has been proposed to improve the performance of linear and successive interference cancellation (SIC) detectors and precoders in MIMO systems. It is proved that LR-aided linear detectors collect the same diversity order as that exploited by the ML detector but with much lower complexity when perfect channel state information (CSI) is assumed to be available. However,...
Iterative Soft-Input Soft-Output (SISO) detection and channel decoding offer significant improvement in error-rate performance for a reduced signal-to-noise ratio. With Multiple-Input Multiple-Output (MIMO) technology being part of many wireless system standards, several low-complexity suboptimal detection algorithms have been proposed. In this paper, a detailed flexibility and convergence analysis...
The Multiple-Input-Multiple-Output (MIMO) has become an attractive technique due to its capability of providing high data rates and link reliability. For next generation wireless systems, for example, WiMAX, LTE and other Orthogonal Frequency Division Multiplexing (OFDM) based communication schemes, system performance greatly depends on the quality detection. Optimal solution for hard decision detection...
An efficient and practicable MIMO transceiver in which transmitter antenna selection is applied to QR detector and GMD precoding through limited feedback channel is implemented. For over 4 ?? 5 antenna selection, the proposed antenna selection scheme can save more than 50% computational complexity compared with that of the exhausting method. From the simulation results, the proposed transceiver can...
This paper describes the concept, architecture, development and demonstration of a real time, maximum likelihood Alamouti decoder for a wireless 4-transmit 4-receiver multiple input and multiple output (MIMO) Smart Antenna Software Radio Test System (SASRATS) platform. It is implemented on a Xilinx Virtex 2 Pro Field Programmable Gate Array (FPGA).Hardware, firmware, use of the Xilinx Core Generator...
This paper considers precoding schemes in physical network coded two-way MIMO relay channels. We propose a lattice reduction aided Tomlinson-Harashima Precoding(THP) scheme at first, and compare it with the existing amplify-and-forward (AF) scheme zero-forcing (ZF) schemes traditional decode-and-forward (DF) scheme and network coding (NC) scheme. Simulations show that the proposed scheme outperforms...
In this paper a VLSI architecture of a high throughput and high performance soft-output (SO) MIMO detector (the recently presented Layered ORthogonal Lattice Detector, LORD) is presented. The baseline implementation includes optimal (i.e. maximum-likelihood - ML - in the max-log sense) SO generation. A reduced complexity variant of the SO generation stage is also described. To the best of the authors'...
MIMO wireless technology is required to increase the data rates for a broad range of applications, including low cost mobile devices. In this paper we present a very low area reconfigurable MIMO detector which achieves a high throughput of 103Mbps and uses 27 Kilo Gates when implemented in a commercial 180nm CMOS process. The low area is achieved by the proposed in-place architecture. This architecture...
The maximum likelihood (ML) detection is the optimal detection method for multiple-input multiple-output (MIMO) communication systems. The normal K-best sphere decoding algorithm (SDA) can guarantee a fixed throughput, but it induces a large bit error rate (BER) degradation. In order to achieve close-to-ML performance, the K value needs to be sufficiently large. Thus, it needs large computation with...
We investigate the capacity of MIMO-CDMA system based on LS spread sequence with suboptimum multicode detector in Ricean fading channel. We compare the capacity of optimum ML multicode detector and suboptimum ZF (zero-forcing) multicode detector under two different Ricean models. It shows multicode detector's behavior is very different with different Ricean models. When Ricean channel is beneficial,...
This paper describes approaches to the problem that lattice-reduction-aided (LRA) detectors have non-ideal decision region and detect outlying constellation points. The proposed approaches find the shortest distance from a received signal to added search signals using quantization error. Using these approaches, we can improve a bit error (BER) performance with a low complexity compared to full search...
Sphere Decoding (SD) algorithms have been shown to provide maximum likelihood (ML) detection over Gaussian multiple input-multiple output (MIMO) channels with lower complexity than the exhaustive search. These methods are based on a closest lattice point search over a limited search space (hypersphere). There exist several implementations of these algorithms pursuiting different search strategies...
In this paper, we propose a low-complexity constant-throughput LLL algorithm for lattice-reduction-aided (LRA) multi-input multi-output (MIMO) detection. The traditional LLL algorithm for the lattice reduction has a drawback of varying throughput due to the variable iteration loops for the size-reduction and LLL-reduction checks. To address this problem, we propose a constant-throughput LLL (CT-LLL)...
We consider soft MIMO detection for the case of block fading. That is, the transmitted codeword spans over several independent channel realizations and several instances of the detection problem must be solved for each such realization. We develop methods that adaptively allocate the computational resources to the detection problems of each channel realization, under a total per-codeword complexity...
An optimal detector for space-time block coded signals with pilot symbol assisted modulation in multiple-input multiple-output (MIMO) systems with imperfect channel estimation is proposed and investigated. We compare its performance with that of traditional mismatched detectors treating channel estimates as perfect in spatially and temporally correlated fading channels. The channel time variations...
We consider the problem of maximum likelihood (ML) signal detection in multiple-input multiple-output (MIMO) wireless communication systems. We propose a new preprocessing algorithm in the form of channel ordering for sphere decoders. Numerical results show that this new channel ordering leads to significantly lower complexity (in the form of the number of nodes visited by the search algorithm); for...
This paper proposes an improved lattice-reduction aided (LRA) MMSE detection based on the Gram-Schmidt (GS) procedure. The proposed detection reduces the column vectors of the MIMO channel matrix using the LLL algorithm and the GS procedure to create mutually purely orthogonal column vectors of the reduced channel matrix. Then the decision boundary becomes the same as that for the ML detection. Compared...
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