The Experts below are selected from a list of 31647 Experts worldwide ranked by ideXlab platform
Kiyomichi Araki - One of the best experts on this subject based on the ideXlab platform.
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Pilot-symbol aided channel estimation in spatially correlated Multiuser MIMO-OFDM channels
IEEE 60th Vehicular Technology Conference 2004. VTC2004-Fall. 2004, 2024Co-Authors: J. Wang, Kiyomichi ArakiAbstract:We address pilot-symbol aided up-link channel estimation for spatially correlated Multiuser MIMO-OFDM systems. A novel pilot-symbol pattern is firstly proposed for this Multiuser system in order to overcome the interference from the Multiuser multi-antennas. Based on these periodically inserted pilot symbols, the channel responses for the entire OFDM data sequence is reconstructed by using the maximum a posteriori probability (MAP) estimation algorithm, exploiting channel correlation in the time, frequency and space domains, which are obtained from a time-variant frequency-selective Rayleigh fading channel model with multiple clusters and complex direction of arrival (DOA). Results demonstrated that system performance can be greatly improved by considering spatial correlation in MIMO-OFDM systems with the designed pilot sequences and proposed 3D filter.
A Chockalingam - One of the best experts on this subject based on the ideXlab platform.
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generalized spatial modulation in large scale Multiuser mimo systems
IEEE Transactions on Wireless Communications, 2015Co-Authors: Lakshmi T Narasimhan, P Raviteja, A ChockalingamAbstract:Generalized spatial modulation (GSM) uses $n_{t} $ transmit antenna elements but fewer transmit radio frequency (RF) chains, $n_{rf} $ . Spatial modulation (SM) and spatial multiplexing are special cases of GSM with $n_{rf}=1$ and $n_{rf}=n_{t} $ , respectively. In GSM, in addition to conveying information bits through $n_{rf} $ conventional modulation symbols (for example, QAM), the indices of the $n_{rf} $ active transmit antennas also convey information bits. In this paper, we investigate GSM for large-scale Multiuser MIMO communications on the uplink. Our contributions in this paper include: 1) an average bit error probability (ABEP) analysis for maximum-likelihood detection in Multiuser GSM-MIMO on the uplink, where we derive an upper bound on the ABEP, and 2) low-complexity algorithms for GSM-MIMO signal detection and channel estimation at the base station receiver based on message passing. The analytical upper bounds on the ABEP are found to be tight at moderate to high signal-to-noise ratios (SNR) . The proposed receiver algorithms are found to scale very well in complexity while achieving near-optimal performance in large dimensions. Simulation results show that, for the same spectral efficiency, Multiuser GSM-MIMO can outperform Multiuser SM-MIMO as well as conventional Multiuser MIMO, by about 2 to 9 dB at a bit error rate of $10^{-3} $ . Such SNR gains in GSM-MIMO compared to SM-MIMO and conventional MIMO can be attributed to the fact that, because of a larger number of spatial index bits, GSM-MIMO can use a lower-order QAM alphabet which is more power efficient.
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generalized spatial modulation in large scale Multiuser mimo systems
arXiv: Information Theory, 2015Co-Authors: Lakshmi T Narasimhan, P Raviteja, A ChockalingamAbstract:Generalized spatial modulation (GSM) uses $n_t$ transmit antenna elements but fewer transmit radio frequency (RF) chains, $n_{rf}$. Spatial modulation (SM) and spatial multiplexing are special cases of GSM with $n_{rf}=1$ and $n_{rf}=n_t$, respectively. In GSM, in addition to conveying information bits through $n_{rf}$ conventional modulation symbols (for example, QAM), the indices of the $n_{rf}$ active transmit antennas also convey information bits. In this paper, we investigate {\em GSM for large-scale Multiuser MIMO communications on the uplink}. Our contributions in this paper include: ($i$) an average bit error probability (ABEP) analysis for maximum-likelihood detection in Multiuser GSM-MIMO on the uplink, where we derive an upper bound on the ABEP, and ($ii$) low-complexity algorithms for GSM-MIMO signal detection and channel estimation at the base station receiver based on message passing. The analytical upper bounds on the ABEP are found to be tight at moderate to high signal-to-noise ratios (SNR). The proposed receiver algorithms are found to scale very well in complexity while achieving near-optimal performance in large dimensions. Simulation results show that, for the same spectral efficiency, Multiuser GSM-MIMO can outperform Multiuser SM-MIMO as well as conventional Multiuser MIMO, by about 2 to 9 dB at a bit error rate of $10^{-3}$. Such SNR gains in GSM-MIMO compared to SM-MIMO and conventional MIMO can be attributed to the fact that, because of a larger number of spatial index bits, GSM-MIMO can use a lower-order QAM alphabet which is more power efficient.
Zhi Ding - One of the best experts on this subject based on the ideXlab platform.
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Robust blind Multiuser detection against signature waveform mismatch based on second-order cone programming
IEEE Transactions on Wireless Communications, 2005Co-Authors: Shuguang Cui, Mikalai Kisialiou, Zhi Quan Luo, Zhi DingAbstract:Blind signal detection in Multiuser code division multiple access (CDMA) system is particularly attractive when only the desired user signature is known to a given receiver. A problem common to several existing blind Multiuser CDMA detectors is that the detection performance is very sensitive to the signature waveform mismatch (SWM) which may be caused by channel distortion. In this paper, we consider the design of a blind Multiuser CDMA detector that is robust to the SWM. We present a convex formulation for this problem by using the second-order cone (SOC) programming. The resulting SOC problem can be solved efficiently using the recently developed interior point methods. Computer simulations indicate that the performance of our new robust blind Multiuser detector is superior to those of many existing methods.
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Robust blind Multiuser detection against CDMA signature mismatch
2001 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings (Cat. No.01CH37221), 2001Co-Authors: Shuguang Cui, Zhi Quan Luo, Zhi DingAbstract:A common problem with the existing blind Multiuser CDMA detectors is that their performance is very sensitive to the signature waveform mismatch (SWM) caused by channel distortion. We consider the problem of designing a blind Multiuser CDMA detector which is robust to the SWM. We present a convex formulation for this problem by using the second order cone (SOC) programming. We also propose the use of recently developed interior point methods to efficiently solve the resulting SOC problem. Computer simulations indicate that the performance of our new robust blind Multiuser detector is superior
Xiaodong Wang - One of the best experts on this subject based on the ideXlab platform.
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adaptive subchannel allocation in Multiuser mc cdma systems
Global Communications Conference, 2004Co-Authors: Chuxiang Li, Xiaodong WangAbstract:We treat the Multiuser scheduling problem in MC-CDMA systems. To reduce the implementation complexity, we present an efficient structure for the Multiuser scheduler. Given the active users and the channels, the subchannel allocator then aims at maximizing the instantaneous system throughput. We develop a stochastic-ruler based algorithm to achieve the subchannel allocation, and prove its global convergence. We also extend the algorithm to track the time-varying optimum in non-stationary channels. We present simulation results to show the performance of the proposed schemes in terms of the throughput maximization with fast convergence, the excellent tracking capability in time-varying channels, and the small throughput loss of the Multiuser scheduler.
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turbo Multiuser detection with unknown interferers
IEEE Transactions on Communications, 2002Co-Authors: Daryl Reynolds, Xiaodong WangAbstract:We consider the problem of turbo Multiuser detection for synchronous and asynchronous code-division multiple-access (CDMA) in the presence of unknown users. Turbo Multiuser detectors, as previously developed, typically require knowledge of the signature waveforms of all of the users in the system and ignore users whose signature sequences are unknown, e.g., users outside the cell. We develop turbo Multiuser detection for CDMA uplink systems and other environments in which the receiver has knowledge of the signature waveforms of only K/spl breve//spl les/ K users. Subspace techniques are used to estimate the interference from the unknown-users and the interference estimate is subtracted from the received signal. We see that the new receiver significantly outperforms the conventional turbo Multiuser receiver for moderate and high signal-to-noise ratios. It is also seen that the traditional turbo receiver provides little gain through iteration when unknown users are present.
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Turbo Multiuser detection with unknown interferers
Proceedings. 2001 IEEE International Symposium on Information Theory (IEEE Cat. No.01CH37252), 2001Co-Authors: Daryl Reynolds, Xiaodong WangAbstract:We consider the problem of turbo Multiuser detection over synchronous CDMA channels in the presence of interfering users whose signature sequences are unknown. We will see that the new receiver significantly outperforms the conventional turbo Multiuser receiver in the presence of unknown interferers, even in situations in which the conventional turbo receiver suffers catastrophic failure.
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Multiuser detection in impulsive noise via slowest descent search
IEEE Workshop on Statistical Signal and Array Processing, 2000Co-Authors: Predrag Spasojevic, Xiaodong WangAbstract:A new technique is proposed for robust Multiuser detection in the presence of non-Gaussian ambient noise. This method is based on minimizing a certain cost function (e.g. the Huber penalty function) over a discrete set of candidate user bit vectors. The set of candidate points are chosen based on the so-called "slowest-descent search", starting from the estimate closest to the unconstrained minimizer of the cost function, and along mutually orthogonal directions where this cost function grows the slowest. The extension of the proposed technique to Multiuser detection in unknown multipath fading channels is also proposed. Simulation results show that this new technique offers substantial performance improvement over the recently proposed robust Multiuser detectors, with little attendant increase in computational complexity.
Zhi Quan Luo - One of the best experts on this subject based on the ideXlab platform.
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Robust blind Multiuser detection based on the worst-case performance optimization of the MMSE receiver
IEEE Transactions on Signal Processing, 2005Co-Authors: Keyvan Zarifi, Shahram Shahbazpanahi, Alex B. Gershman, Zhi Quan LuoAbstract:The conventional minimum mean-square error (MMSE) Multiuser receiver requires that each particular user transmits a sequence of training symbols known to the receiver and the receiver estimates the user signatures using this knowledge. However, in the presence of multiaccess interference (MAI) during the training period and/or in scenarios with short training sequence length, the signature estimates can be erroneous, and the performance of the MMSE Multiuser receiver can degrade substantially. In this paper, we propose a new blind Multiuser receiver that is robust against the effects of erroneously presumed desired user signature and short data length. Our approach is based on the explicit modeling of possible mismatches in the mean-square error cost function and worst-case performance optimization. We show that this approach leads to a Multiuser receiver which uses the data covariance matrix with an adaptive diagonal loading . The proposed method has simple implementation with a computational complexity comparable with that of the fixed diagonal loading-based Multiuser receiver. Simulation results show performance improvements achieved by our approach relative to existing techniques.
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Robust blind Multiuser detection against signature waveform mismatch based on second-order cone programming
IEEE Transactions on Wireless Communications, 2005Co-Authors: Shuguang Cui, Mikalai Kisialiou, Zhi Quan Luo, Zhi DingAbstract:Blind signal detection in Multiuser code division multiple access (CDMA) system is particularly attractive when only the desired user signature is known to a given receiver. A problem common to several existing blind Multiuser CDMA detectors is that the detection performance is very sensitive to the signature waveform mismatch (SWM) which may be caused by channel distortion. In this paper, we consider the design of a blind Multiuser CDMA detector that is robust to the SWM. We present a convex formulation for this problem by using the second-order cone (SOC) programming. The resulting SOC problem can be solved efficiently using the recently developed interior point methods. Computer simulations indicate that the performance of our new robust blind Multiuser detector is superior to those of many existing methods.
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Robust blind Multiuser detection against CDMA signature mismatch
2001 IEEE International Conference on Acoustics Speech and Signal Processing. Proceedings (Cat. No.01CH37221), 2001Co-Authors: Shuguang Cui, Zhi Quan Luo, Zhi DingAbstract:A common problem with the existing blind Multiuser CDMA detectors is that their performance is very sensitive to the signature waveform mismatch (SWM) caused by channel distortion. We consider the problem of designing a blind Multiuser CDMA detector which is robust to the SWM. We present a convex formulation for this problem by using the second order cone (SOC) programming. We also propose the use of recently developed interior point methods to efficiently solve the resulting SOC problem. Computer simulations indicate that the performance of our new robust blind Multiuser detector is superior
