The Experts below are selected from a list of 278586 Experts worldwide ranked by ideXlab platform
Yu-dong Yao - One of the best experts on this subject based on the ideXlab platform.
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Deterministic multiuser carrier-frequency offset estimation for interleaved OFDMA uplink
IEEE Transactions on Communications, 2004Co-Authors: Zhongren Cao, Ufuk Tureli, Yu-dong YaoAbstract:In orthogonal frequency-division multiple access (OFDMA), closely spaced multiple subcarriers are assigned to different users for parallel Signal transmission. An interleaved subcarrier-assignment scheme is preferred because it provides maximum frequency diversity and increases the capacity in frequency-selective fading channels. The subcarriers are overlapping, but orthogonal to each other such that there is no intercarrier interference (ICI). Carrier-frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduces ICI, resulting in multiple-access interference. This paper exploits the inner Structure of the Signals for CFO estimation in the uplink of interleaved OFDMA systems. A new uplink Signal model is presented, and an estimation algorithm based on the Signal Structure is proposed for estimating the CFOs of all users using only one OFDMA block. Diversity schemes are also presented to improve the estimation performance. Simulation results illustrate the high accuracy and efficiency of the proposed algorithm.
Julia C Kenyon - One of the best experts on this subject based on the ideXlab platform.
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an rna binding compound that stabilizes the hiv 1 grna packaging Signal Structure and specifically blocks hiv 1 rna encapsidation
Retrovirology, 2018Co-Authors: Carin K Ingemarsdotter, Jingwei Zeng, Ziqi Long, Andrew M L Lever, Julia C KenyonAbstract:NSC260594, a quinolinium derivative from the NCI diversity set II compound library, was previously identified in a target-based assay as an inhibitor of the interaction between the HIV-1 (ψ) stem-loop 3 (SL3) RNA and Gag. This compound was shown to exhibit potent antiviral activity. Here, the effects of this compound on individual stages of the viral lifecycle were examined by qRT-PCR, ELISA and Western blot, to see if its actions were specific to the viral packaging stage. The structural effects of NSC260594 binding to the HIV-1 gRNA were also examined by SHAPE and dimerization assays. Treatment of cells with NSC260594 did not reduce the number of integration events of incoming virus, and treatment of virus producing cells did not affect the level of intracellular Gag protein or viral particle release as determined by immunoblot. However, NSC260594 reduced the incorporation of gRNA into virions by up to 82%, without affecting levels of gRNA inside the cell. This reduction in packaging correlated closely with the reduction in infectivity of the released viral particles. To establish the structural effects of NSC260594 on the HIV-1 gRNA, we performed SHAPE analyses to pinpoint RNA structural changes. NSC260594 had a stabilizing effect on the wild type RNA that was not confined to SL3, but that was propagated across the Structure. A packaging mutant lacking SL3 did not show this effect. NSC260594 acts as a specific inhibitor of HIV-1 RNA packaging. No other viral functions are affected. Its action involves preventing the interaction of Gag with SL3 by stabilizing this small RNA stem-loop which then leads to stabilization of the global packaging Signal region (psi or ψ). This confirms data, previously only shown in analyses of isolated SL3 oligonucleotides, that SL3 is structurally labile in the presence of Gag and that this is critical for the complete psi region to be able to adopt different conformations. Since replication is otherwise unaffected by NSC260594 the flexibility of SL3 appears to be a unique requirement for genome encapsidation and identifies this process as a highly specific drug target. This study is proof of principle that development of a new class of antiretroviral drugs that specifically target viral packaging by binding to the viral genomic RNA is achievable.
V K Bhargava - One of the best experts on this subject based on the ideXlab platform.
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optimal periodic training Signal for frequency offset estimation in frequency selective fading channels
IEEE Transactions on Communications, 2006Co-Authors: Hlaing Minn, V K BhargavaAbstract:This paper addresses an optimal periodic training Signal design for frequency offset estimation in frequency-selective multipath Rayleigh fading channels. For a fixed transmitted training Signal energy within a fixed-length block, the optimal periodic training Signal Structure (the optimal locations of identical training subblocks) and the optimal training subblock Signal are presented. The optimality is based on the minimum Cramer-Rao bound (CRB) criterion. Based on the CRB for joint estimation of frequency offset and channel, the optimal periodic training Structure (optimality only in frequency offset estimation, not necessarily in joint frequency offset and channel estimation) is derived. The optimal training subblock Signal is obtained by using the average CRB (averaged over the channel fading) and the received training Signal statistics. A robust training Structure design is also presented in order to reduce the occurrence of outliers at low Signal-to-noise ratio values. The proposed training Structures and subblock Signals achieve substantial performance improvement
Yietarng Chen - One of the best experts on this subject based on the ideXlab platform.
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joint carrier frequency offset and direction of arrival estimation via hierarchical esprit for interleaved ofdma sdma uplink systems
Vehicular Technology Conference, 2010Co-Authors: Kuohsiung Wu, Wenhsien Fang, Yietarng ChenAbstract:In this paper, we propose an efficient algorithm to jointly estimate the directions of arrival (DOAs) and carrier frequency offsets (CFOs) in interleaved orthogonal frequency division multiple access / space division multiple access (OFDMA/SDMA) uplink networks. The algorithm makes use of the Signal Structure by estimating the CFOs and DOAs in a hierarchical tree Structure, in which two CFO estimations and one DOA estimation are employed alternatively. One special feature in the proposed algorithm is that the algorithm proceeds in a coarse-fine manner with temporal filtering or spatial beamforming being invoked between the parameter estimations to decompose the Signals progressively into subgroups so as to enhance the estimation accuracy and lower the computational overhead. Simulations show that the proposed algorithm can provide satisfactory performance with increased channel capacity.
Zhongren Cao - One of the best experts on this subject based on the ideXlab platform.
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Deterministic multiuser carrier-frequency offset estimation for interleaved OFDMA uplink
IEEE Transactions on Communications, 2004Co-Authors: Zhongren Cao, Ufuk Tureli, Yu-dong YaoAbstract:In orthogonal frequency-division multiple access (OFDMA), closely spaced multiple subcarriers are assigned to different users for parallel Signal transmission. An interleaved subcarrier-assignment scheme is preferred because it provides maximum frequency diversity and increases the capacity in frequency-selective fading channels. The subcarriers are overlapping, but orthogonal to each other such that there is no intercarrier interference (ICI). Carrier-frequency offsets (CFOs) between the transmitter and the receiver destroy the orthogonality and introduces ICI, resulting in multiple-access interference. This paper exploits the inner Structure of the Signals for CFO estimation in the uplink of interleaved OFDMA systems. A new uplink Signal model is presented, and an estimation algorithm based on the Signal Structure is proposed for estimating the CFOs of all users using only one OFDMA block. Diversity schemes are also presented to improve the estimation performance. Simulation results illustrate the high accuracy and efficiency of the proposed algorithm.
