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A new method for multiple-input multiple-output (MIMO) detection with soft-output, the partial marginalization (PM) algorithm, was recently proposed. Advantages of the method are that it is straightforward to parallelize, and that it offers a fully predictable runtime. PM trades performance for computational complexity via a user-defined parameter. In the limit of high computational complexity, the...
In MIMO communication system the conventional Turbo-BLAST receiver using Gray mapping converges slow. For this reason, an improved Turbo-BLAST scheme with Anti-Gray mapping is proposed in this paper. Research has shown that the iterative receiver using new scheme outperforms the convention alone and obtains a faster convergence rate. Also, an improved receiver based on soft interference cancellation...
In this paper, the time-delay estimation problem is studied for multiple-input single-output (MISO) systems. First, a theoretical analysis is carried out by deriving the Cramer-Rao lower bound (CRLB) for time-delay estimation in a MISO system. Then, the maximum likelihood (ML) estimator for the time-delay parameter is obtained, which results in a complex optimization problem in general. In order to...
Precoding is an effective method to improve the transmission quality in multiple-input multiple-output (MIMO) systems. In a real-world system, the precoder is selected from a codebook, and its index is fed back to the transmitter. For a maximum-likelihood (ML) receiver, the criterion for precoder selection is equivalent to maximizing the minimum distance of the received signal constellation. The derivation...
In this paper, an efficient Multiple-input multiple-output (MIMO) detection scheme with low complexity is proposed. The proposed scheme has a feature of combined a QRD-M, which is the M-algorithm combined with QR decomposition, with a complex lattice reduction (LR)-aided detection scheme. For the first T stages, the QRD-M detection is executed. And then, the complex LR-aided detection is executed...
The throughout of wireless communication systems can be improved by adding multiple antennas at the transmitter and receiver to create multiple-input multiple-output channels. To avoid the prohibitive complexity involved in the ML detectors, some special detectors were proposed to improve the performance-complexity trade-off, such as zero-forcing (ZF), minimum mean-square (MMSE), vertical Bell labs...
Computing the log likelihood ratios (LLR's) of the transmitted bits in a multiple-input multiple-output (MIMO) system is an NP hard problem. Many suboptimal soft MIMO detectors have been proposed to reduce the detection complexity. The state-of-the art tries to combine the search for the maximum a posteriori (MAP) estimate and the counter-hypotheses in a single tree pass. However, not all possible...
The QR Decomposition (QRD) of communication channel matrices is a fundamental prerequisite to several detection schemes in Multiple-Input Multiple-Output (MIMO) communication systems. Herein, the main feature of the QRD is to transform the non-causal system into a causal system, where consequently efficient detection algorithms based on the Successive Interference Cancellation (SIC) or Sphere Decoder...
Recently, pre-fast Fourier transform (pre-FFT) combining has been introduced for space-time block-coded (STBC) orthogonal frequency division multiplexing (OFDM) systems. Despite the complexity reduction, the resultant signal-to-noise ratio (SNR) values of different subcarriers are often not balanced, and it limits the system performance. In this paper, we propose to use the max-min fair criterion...
Because of rapid channel attenuation in lossy environment, there is a severe packet drop loss problem in wireless ad hoc networks. Though MIMO (Multi-Input Multi-Output) technology can alleviate this effect greatly, it will result in higher transmission energy depletion as using more transmit antennas. Lots of schemes have been proposed to reduce such energy cost by transmit antenna selection. However,...
The VLSI implementation of maximum likelihood (ML) detection for higher order multiple input multiple output (MIMO) systems continues to be a major challenge. Battery driven handheld devices impose strict area and power constraints while demanding guaranteed performance over a wide range of operating conditions. This paper presents a modified, low complexity K-best detector for a 4??4, 64 QAM MIMO...
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