The Experts below are selected from a list of 19863 Experts worldwide ranked by ideXlab platform
Yang Yang - One of the best experts on this subject based on the ideXlab platform.
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carrier aggregation for lte advanced mobile communication systems
IEEE Communications Magazine, 2010Co-Authors: Guangxiang Yuan, Wenbo Wang, Xiang Zhang, Yang YangAbstract:In order to achieve up to 1 Gb/s peak Data rate in future IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-Data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. This article first gives a brief review of continuous and non-continuous CA techniques, followed by two Data aggregation schemes in physical and medium access control layers. Some technical challenges for implementing CA technique in LTE-Advanced systems, with the requirements of backward compatibility to LTE systems, are highlighted and discussed. Possible technical solutions for the asymmetric CA problem, control signaling design, handover control, and guard band setting are reviewed. Simulation results show Doppler frequency shift has only limited impact on Data transmission performance over wide frequency bands in a high-speed mobile environment when the component carriers are time synchronized. The frequency aliasing will generate much more interference between adjacent component carriers and therefore greatly degrades the bit error rate performance of Downlink Data transmissions.
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carrier aggregation for lte advanced mobile communication systems
IEEE Communications Magazine, 2010Co-Authors: Guangxiang Yuan, Wenbo Wang, Xiang Zhang, Yang YangAbstract:In order to achieve up to 1 Gb/s peak Data rate in future IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-Data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. This article first gives a brief review of continuous and non-continuous CA techniques, followed by two Data aggregation schemes in physical and medium access control layers. Some technical challenges for implementing CA technique in LTE-Advanced systems, with the requirements of backward compatibility to LTE systems, are highlighted and discussed. Possible technical solutions for the asymmetric CA problem, control signaling design, handover control, and guard band setting are reviewed. Simulation results show Doppler frequency shift has only limited impact on Data transmission performance over wide frequency bands in a high-speed mobile environment when the component carriers are time synchronized. The frequency aliasing will generate much more interference between adjacent component carriers and therefore greatly degrades the bit error rate performance of Downlink Data transmissions.
Erik G Larsson - One of the best experts on this subject based on the ideXlab platform.
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blind channel estimation for Downlink massive mimo systems with imperfect channel reciprocity
IEEE Transactions on Signal Processing, 2020Co-Authors: Ribhu Chopra, Chandra R Murthy, Himal A Suraweera, Erik G LarssonAbstract:We consider the performance of time-division duplex (TDD) massive multiple-input multiple-output (MIMO) with imperfect calibration of the transmit and receive radio frequency chains. By deriving the achievable signal-to-interference-plus-noise ratio (SINR) and the per-user bit error rate (BER) for constant modulus constellations, we establish that, under linear precoding, reciprocity imperfections can result in substantial reduction of the array gain. To mitigate this loss, we propose an algorithm for blind estimation of the effective channel gain at each user. We show that, with sufficiently many Downlink Data symbols, our blind channel estimation algorithm restores the array gain. In addition, the proposed blind gain estimation algorithm can improve performance compared to standard hardening-based receivers even under perfect reciprocity. Following this, we derive the BERs for non-constant modulus constellations, viz. $M$ -PAM and $M$ -QAM. We corroborate all our derived results using numerical simulations.
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max min fair transmit precoding for multi group multicasting in massive mimo
IEEE Transactions on Wireless Communications, 2018Co-Authors: Meysam Sadeghi, Emil Bjornson, Erik G Larsson, Chau Yuen, Thomas L MarzettaAbstract:This paper considers the Downlink precoding for physical layer multicasting in massive multiple-input multiple-output (MIMO) systems. We study the max–min fairness (MMF) problem, where channel state information at the transmitter is used to design precoding vectors that maximize the minimum spectral efficiency (SE) of the system, given fixed power budgets for uplink training and Downlink transmission. Our system model accounts for channel estimation, pilot contamination, arbitrary path-losses, and multi-group multicasting. We consider six scenarios with different transmission technologies (unicast and multicast), different pilot assignment strategies (dedicated or shared pilot assignments), and different precoding schemes (maximum ratio transmission and zero forcing), and derive achievable spectral efficiencies for all possible combinations. Then, we solve the MMF problem for each of these scenarios, and for any given pilot length, we find the SE maximizing uplink pilot and Downlink Data transmission policies, all in closed forms. We use these results to draw a general guideline for massive MIMO multicasting design, where for a given number of base station antennas, number of users, and coherence interval length, we determine the multicasting scheme that shall be used.
Sidharth Misra - One of the best experts on this subject based on the ideXlab platform.
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development of an on board wide band processor for radio frequency interference detection and filtering
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: Sidharth Misra, Shannon Brown, Rudi Bendig, Jonathon Kocz, R F Jarnot, Carl Felten, J JohnsonAbstract:The demand for microwave spectrum for commercial and industrial use has been increasing rapidly over the last decade, putting stress on the limited spectral resources for passive microwave remote sensing. Radio frequency interference from man-made sources is expected to become worse over the coming years. At 1.4 GHz, the SMAP mission has implemented and demonstrated advanced interference detection algorithms for its microwave radiometer. This scheme will not be feasible at higher microwave frequencies (above 6 GHz) due to much larger radiometer bandwidths used and the limited Downlink Data volume available to implement RFI filtering algorithms in the ground processing. In this paper, we present the design, development, and test of an advanced on-board interference detection and RFI filtering digital back-end that is capable of operation for a 1 GHz-radiometer bandwidth. We describe the combined RFI detection algorithms implemented in the digital backend’s firmware and the on-board RFI filtering of interference-corrupted Data that will be necessary to limit Downlink rate requirements for future high-frequency microwave missions.
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microwave radiometer radio frequency interference detection algorithms a comparative study
International Geoscience and Remote Sensing Symposium, 2009Co-Authors: Sidharth Misra, Priscilla N Mohammed, Aris Gune, Jeffrey R Piepmeie, Joel T JohnsoAbstract:Two algorithms used in microwave radiometry for radio-frequency interference (RFI) detection and mitigation are the pulse detection algorithm and the kurtosis detection algorithm. The relative performance of the algorithms is compared both analytically and empirically. Their probabilities of false alarm under RFI-free conditions and of detection when RFI is present are examined. The Downlink Data rate required to implement each algorithm in a spaceborne application is also considered. The kurtosis algorithm is compared to a pulse detection algorithm operating under optimal RFI detection conditions. The performance of both algorithms is also analyzed as a function of varying characteristics of the RFI. The RFI detection probabilities of both algorithms under varying subsampling conditions are compared and validated using Data obtained from a field campaign. Implementation details, resource usage, and postprocessing requirements are also addressed for both algorithms.
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comparison of pulsed sinusoid radio frequency interference detection algorithms using time and frequency sub sampling
International Geoscience and Remote Sensing Symposium, 2008Co-Authors: Sidharth MisraAbstract:The performance of two major Radio Frequency Interference (RFI) detection algorithms is compared. The peak detection algorithm and the kurtosis detection algorithm are characterized using the receiver operating characteristic (ROC) for pulsed sinusoid RFI. Downlink Data bandwidth is one of the major design factors to be considered when comparing detection algorithms. Results are presented in this paper that compare the kurtosis algorithm performance with an ideally matched peak detection algorithm. The RFI parameters are also varied to analyze the overall detection performance of both algorithms. Factors such as implementation details, resource usage, post-processing and practicality are also addressed for both algorithms.
J Johnson - One of the best experts on this subject based on the ideXlab platform.
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development of an on board wide band processor for radio frequency interference detection and filtering
IEEE Transactions on Geoscience and Remote Sensing, 2019Co-Authors: Sidharth Misra, Shannon Brown, Rudi Bendig, Jonathon Kocz, R F Jarnot, Carl Felten, J JohnsonAbstract:The demand for microwave spectrum for commercial and industrial use has been increasing rapidly over the last decade, putting stress on the limited spectral resources for passive microwave remote sensing. Radio frequency interference from man-made sources is expected to become worse over the coming years. At 1.4 GHz, the SMAP mission has implemented and demonstrated advanced interference detection algorithms for its microwave radiometer. This scheme will not be feasible at higher microwave frequencies (above 6 GHz) due to much larger radiometer bandwidths used and the limited Downlink Data volume available to implement RFI filtering algorithms in the ground processing. In this paper, we present the design, development, and test of an advanced on-board interference detection and RFI filtering digital back-end that is capable of operation for a 1 GHz-radiometer bandwidth. We describe the combined RFI detection algorithms implemented in the digital backend’s firmware and the on-board RFI filtering of interference-corrupted Data that will be necessary to limit Downlink rate requirements for future high-frequency microwave missions.
Guangxiang Yuan - One of the best experts on this subject based on the ideXlab platform.
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carrier aggregation for lte advanced mobile communication systems
IEEE Communications Magazine, 2010Co-Authors: Guangxiang Yuan, Wenbo Wang, Xiang Zhang, Yang YangAbstract:In order to achieve up to 1 Gb/s peak Data rate in future IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-Data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. This article first gives a brief review of continuous and non-continuous CA techniques, followed by two Data aggregation schemes in physical and medium access control layers. Some technical challenges for implementing CA technique in LTE-Advanced systems, with the requirements of backward compatibility to LTE systems, are highlighted and discussed. Possible technical solutions for the asymmetric CA problem, control signaling design, handover control, and guard band setting are reviewed. Simulation results show Doppler frequency shift has only limited impact on Data transmission performance over wide frequency bands in a high-speed mobile environment when the component carriers are time synchronized. The frequency aliasing will generate much more interference between adjacent component carriers and therefore greatly degrades the bit error rate performance of Downlink Data transmissions.
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carrier aggregation for lte advanced mobile communication systems
IEEE Communications Magazine, 2010Co-Authors: Guangxiang Yuan, Wenbo Wang, Xiang Zhang, Yang YangAbstract:In order to achieve up to 1 Gb/s peak Data rate in future IMT-Advanced mobile systems, carrier aggregation technology is introduced by the 3GPP to support very-high-Data-rate transmissions over wide frequency bandwidths (e.g., up to 100 MHz) in its new LTE-Advanced standards. This article first gives a brief review of continuous and non-continuous CA techniques, followed by two Data aggregation schemes in physical and medium access control layers. Some technical challenges for implementing CA technique in LTE-Advanced systems, with the requirements of backward compatibility to LTE systems, are highlighted and discussed. Possible technical solutions for the asymmetric CA problem, control signaling design, handover control, and guard band setting are reviewed. Simulation results show Doppler frequency shift has only limited impact on Data transmission performance over wide frequency bands in a high-speed mobile environment when the component carriers are time synchronized. The frequency aliasing will generate much more interference between adjacent component carriers and therefore greatly degrades the bit error rate performance of Downlink Data transmissions.