A multiple-inputmultiple-output (MIMO) system that combines diversity and multiplexing is proposed for multi-cellular networks with cochannel interference. In the proposed MIMO system, the data stream is divided into...
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A multiple-inputmultiple-output (MIMO) system that combines diversity and multiplexing is proposed for multi-cellular networks with cochannel interference. In the proposed MIMO system, the data stream is divided into multiple substreams, and each substream is transmitted and received over multiple antenna elements. Because of having both the advantages provided by diversity and multiplexing, the proposed MIMO system can gain larger throughput than the scheme with either diversity or multiplexing solely being employed. We propose an algorithm to find the optimum antenna configuration that maximises the throughput of the proposed MIMO system. We also propose a power control algorithm for the proposed MIMO system such that the interference is decreased and the throughput can be increased. In addition, the time division multiple access scheme and a scheduling algorithm are proposed to mitigate the interference in one time slot so that the throughput of the proposed MIMO system can be further increased.
We propose a shuffling cluster sequence technique without separate side information (SI) for multiple-inputmultiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. In the proposed technique, ...
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We propose a shuffling cluster sequence technique without separate side information (SI) for multiple-inputmultiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. In the proposed technique, the active subcarriers over two consecutive OFDM symbols are divided into 2V$$ 2V $$ clusters, and each cluster (packet frame) includes a header for ID#cluster and payload for Data#cluster$$ Data\# cluster $$. The 2V$$ 2V $$ clusters are shuffled to reduce the peak-to-average power ratio (PAPR) of the time-domain OFDM signal, which includes the information data and SI signals, with a low computational complexity. At the receiver, the information data can be correctly reconstructed by ID#cluster in the header of each cluster, achieving a smaller bit error rate than the conventional MIMO-OFDM system without PAPR reduction. Moreover, our technique is comparable with the conventional partial transmit sequence technique without the impact of a separate SI signal even when increasing the number of transmitter antennas in a nonlinear multipath fading channel.
The performance of bit-interleaved coded modulation in multiple-inputmultiple-output (BICM-MIMO) systems using an iterative channel estimator is analysed. In a conventional iterative channel estimator, after initiali...
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The performance of bit-interleaved coded modulation in multiple-inputmultiple-output (BICM-MIMO) systems using an iterative channel estimator is analysed. In a conventional iterative channel estimator, after initialisation with the training phase, the channel estimator switches to the data phase. However, such a conventional iterative channel estimator does not always improve the performance of the receiver. In order to guarantee the performance improvement, a condition on when the output of the decoder should be used by the estimator is determined. Such a condition is related to the reliability of the soft information utilised by the channel estimator. The key in establishing this relationship is to use the mutual information (MI) that the observation vector has about the channel gains given the output of the decoder at each iteration. In this switch-augmented conventional iterative channel estimator, referred to as SAICE, the condition is theoretically found and indicates the needed reliability of the soft information for the channel estimator at the switching time. The switch-augmented scheme guarantees performance improvement of the iterative receiver with each iteration, however, it might need many iterations to converge for moderate to low signal-to-noise ratios (SNRs). A less computationally intensive approach is to use both the training and data segments of the observation. This approach produces a combined iterative channel estimator (CICE) for BICM-MIMO systems. The performance behaviour of the BICM-MIMO system is illustrated through the extrinsic information transfer (EXIT) chart with imperfect channel state information (CSI). Analytical results are verified with computer simulations.
The authors present a complexity reduced near-maximum-likelihood (ML) scheme for the decoding of multiple-inputmultiple-output (MIMO) systems, which is targeted at a recently proposed fixed-complexity sphere decoder ...
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The authors present a complexity reduced near-maximum-likelihood (ML) scheme for the decoding of multiple-inputmultiple-output (MIMO) systems, which is targeted at a recently proposed fixed-complexity sphere decoder (FSD). The proposed decoder that the authors call the statistical threshold-based FSD (ST-FSD) combines a threshold constraint strategy with the FSD search region, thus speeding up the FSD algorithm by avoiding unnecessary search paths. As a consequence, higher efficiency and lower complexity can be obtained. The optimum threshold is derived through analysis of the statistical distributions of the correct and erroneous estimates. Furthermore, a tight lower bound on the threshold has been obtained by using the singular value decomposition (SVD) method and applied to the FSD. From simulation results, the proposed scheme is shown to be able to achieve a significant reduction in computational complexity with almost no performance degradation compared to the original FSD algorithm. Moreover, a novel grouped architecture for efficient hardware implementation of the proposed ST-FSD algorithm is motivated through simulation results and shown to compare favourably with the alternative options. This confirms that the ST-FSD is advantageous with respect to the original FSD in terms of the overall complexity.
The authors investigate the performance of multiple-input-multiple-output multicarrier direct sequence code division multiple access system operating over arbitrarily and equally correlated -mu fading channels in term...
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The authors investigate the performance of multiple-input-multiple-output multicarrier direct sequence code division multiple access system operating over arbitrarily and equally correlated -mu fading channels in terms of average bit error probability and average symbol error probability. Closed form expressions for average error probability using moment generating function-based approach are derived and expressed in terms of Lauricella's multivariate hypergeometric functions. Furthermore, based on numerical results, they observe that the performance of the system improves when the number of multipath clusters increases as well as the number of subcarriers (frequency diversity). Similarly, substantial enhancement in system performance is observed due to the effect of spatial diversity. Finally, they verify the results via Monte Carlo simulation-based method to support the accuracy of the analytical approach and also compare with already published ones.
In this study, a rate-varying space-time pre-coding scheme for a multiple-input multiple-output system in a fast-fading channel is proposed. In particular, unlike the traditional fixed rate space-time coding scheme, t...
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In this study, a rate-varying space-time pre-coding scheme for a multiple-input multiple-output system in a fast-fading channel is proposed. In particular, unlike the traditional fixed rate space-time coding scheme, the transmitter which has no channel state information keeps choosing a pre-coding matrix randomly at each space-time symbol period to deliver the information until it is successfully decoded by the receiver. Since the number of received symbol vectors needed to successfully decode the information is determined by the channel realisation, the coding rate of the proposed scheme can adapt to the fast-fading channel. The exact expression of the equivalent signal-to-noise ratio gain after the post-combining and zero-forcing equalisation at the receiver side is derived, and a design criteria to achieve optimal performance in terms of average error probability and ergodic capacity under the mean power constraint is provided. Based on this, a minimal variance pre-coding (MVP) scheme is designed, which is compared with an intuitive Gaussian pre-coding scheme. It is shown that the MVP scheme has better performance and could adapt to different channel conditions.
In steelworks the demand for a higher product quality level has improved the rolling mill process by means of a proper work roll speed control system. Firstly this paper proposes a lumped-parameter hot-rolling mill mo...
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In steelworks the demand for a higher product quality level has improved the rolling mill process by means of a proper work roll speed control system. Firstly this paper proposes a lumped-parameter hot-rolling mill model. The rolling mill examined is reversible and equipped with an independent speed control system for each work roll (two single-input single-outputsystems). Therefore, the same revolution speed, essential for a high-quality process, can only be ensured by equal set point values. Nevertheless, during the process, different disturbance load torques cause speed differences and, even if they are not noticeable, rolled section defects cannot be avoided. The second part of the paper shows that it is possible to design a proper H-infinity controller, to change the two independent control systems into a more complex multiple-input multiple-output system that will obtain decidedly better performances. Simulation examples have shown improvements.
A semi-definite relaxation decoder is proposed for a multiple-inputmultiple-output (MIMO) system based on 256-QAM constellation. Simulation results indicate that it is computationally efficient and can provide better...
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A semi-definite relaxation decoder is proposed for a multiple-inputmultiple-output (MIMO) system based on 256-QAM constellation. Simulation results indicate that it is computationally efficient and can provide better block-error-rate performance than a sub-optimal decoder.
Spatial correlation is a decisive factor for pragmatic multiple-inputmultiple-output (MIMO) system, simultaneously bringing about some problems in the received signal modulation identification respect. In this study,...
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Spatial correlation is a decisive factor for pragmatic multiple-inputmultiple-output (MIMO) system, simultaneously bringing about some problems in the received signal modulation identification respect. In this study, the authors focus on blind digital modulation identification in the spatially correlated MIMO system and deliver a robust signal recognition algorithm based on extreme learning machine (ELM) and higher order statistical features for MIMO signal identification without a priori knowledge of the channel and signal parameters. The superiority of ELM lies in random selections of hidden nodes and ascertains output weights analytically, which result in lower computational complexity. Theoretically, this algorithm has a tendency to supply excellent generalisation performance at staggering learning rate. Further, the simulation results indicate that the ELM could reap a perfectly acceptable recognition performance and thus provides a solid ground structure for tackling MIMO modulation challenges in low signal-to-noise ratio.
A beamforming and combining method for a multi-user large multiple-inputmultiple-output (MIMO) system is proposed, in this study. A transmitter is equipped with a very large number of antennas to serve many users. At...
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A beamforming and combining method for a multi-user large multiple-inputmultiple-output (MIMO) system is proposed, in this study. A transmitter is equipped with a very large number of antennas to serve many users. At the transmitter, a group of antennas is allocated to each user. For a particular group of antennas, a specific beamforming vector is employed at the transmitter for transmission of a signal of a specific user. At the user end, a distinct combining vector is utilised for detecting the transmitted signal. In the proposed scheme, first, the interference due to unwanted signals of undesired users is nullified by using the concept of null space. Then the method of maximum ratio transmission is used to calculate the beamforming vector. The calculation of combining vector depends upon the maximum eigenvalue criterion. The analytical performance of the proposed method is discussed in terms of symbol error rate (SER). An expression of SER is derived by using the moment generating function approach. It is shown by simulations and analysis that the proposed scheme performs better if more antennas are equipped either at the transmitter or users.
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