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MDL-based root-mean-squared delay spread estimation for MIMO OFDM systems

Journal of Southeast University(English Edition) 2004年第4期20卷 395-400页

作者：徐晓东井雅尤肖虎东南大学移动通信国家重点实验室南京210096

This paper studied the application of minimum description length (MDL) criterion for estimating root-mean-squared (RMS) delay spread (RDS) for MIMO OFDM systems. The analytic relationship between the powers and the correlation matrix of multipath components established the feasibility of the application of the MDL criterion to RDS estimation. The estimator presented both the estimate of instantaneous RDS and the estimates of noise variance, channel power and SNR of current channel with low computational complexity. Given the powers of the estimated multipath components, the MDL criterion was adopted to acquire the number of paths and the time delays of each path of current channel without making eigendecomposition of the correlation matrix normally required by MDL criterion, following which the noise variance and the power of each path can be estimated. The power delay profile (PDP) and RDS of the current channel were achieved. Simulation results showed that the proposed estimator was insensitive to variance of SNR and robust against frequency-selectivity.

关键词： Communication channels (information theory) Delay control systems Fading (radio) Robustness (control systems) Signal processing Wireless telecommunication systems

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Lower bound on BER performance for maximal ratio combining with weighting errors

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Journal of Southeast University(English Edition) 2005年第4期21卷 379-384页

作者：盛彬尤肖虎东南大学移动通信国家重点实验室南京210096

The theoretical lower bounds on mean squared channel estimation errors for typical fading channels are presented by the infinite-length and non-causal Wiener filter and the exact closed-form expressions of the lower bounds for different channel Doppler spectra are derived. Based on the obtained lower bounds on mean squared channel estimation errors, the limits on bit error rate （BER） for maximal ratio combining （MRC） with Gaussian distributed weighting errors on independent and identically distributed （i. i. d） fading channels are presented. Numerical results show that the BER performances of ideal MRC are the lower bounds on the BER performances of non-ideal MRC and deteriorate as the maximum Doppler frequency increases or the SNR of channel estimate decreases.

关键词： lower bound bit error rate minimum mean-square error channel estimation maximal ratio combining

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Doppler shift estimation methods in mobile communication systems

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Journal of Southeast University(English Edition) 2004年第4期20卷 405-411页

作者：华惊宇尤肖虎东南大学移动通信国家重点实验室南京210096

Several Doppler shift estimators, including mean logarithm envelope difference (MLED) method, auto-correlation function (ACF) method, zero crossing rate (ZCR) method and mean square phase difference (MSPD) method were discussed and compared. The estimation principle and theoretical estimation bias of these estimators under Rayleigh fading channels were analyzed; furthermore, the Cramer Rao bound (CRB) of Doppler shift estimation was deduced, and a novel modification method based on two-dimensional polynomial fitting was proposed to reduce the Doppler shift estimation bias. We verified our algorithms with the Monte Carlo computer simulation; simulation results showed better variance performance of modified methods than those of the original methods. In addition, the applicable situations of these estimators were discussed.

关键词： Error analysis Mobile telecommunication systems Monte Carlo methods Polynomials Rayleigh fading Signal to noise ratio Two dimensional

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Relay selection region and system performance analysis for interfered cooperative ad-hoc networks

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Journal of Southeast University(English Edition) 2012年第1期28卷 8-13页

作者：徐艳丽夏玮玮沈连丰东南大学移动通信国家重点实验室南京210096

The performance of interfered cooperative ad-hoc networks is analyzed by stochastic geometry analysis and a selection region of relay is presented. First, assuming that the distribution of nodes in the random network follows the Poisson point process （PPP）, a closed-form expression of the outage probability is derived for the best relay selection （BRS） scheme. Secondly, the capacity of the network is presented for this scheme. Finally, a performance factor is defined to evaluate the performance gain obtained from the BRS. By using this factor, a relay selection region is found to guarantee the performance gain from the BRS. The analysis and simulation results show that the performance of the BRS not only depends on the densities of source nodes and relay nodes but also on the factors of networks such as the path loss factor and the decoding threshold. And the BRS has a greater advantage than direct transmission （DT） in hush environments such as the long transmission distances, much interference and the high decoding thresholds.

关键词： cooperation interference relay selection outageprobability transmission capacity stochastic geometry analysis

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New method to compute the throughput capacity of HDR wireless networks

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Journal of Southeast University(English Edition) 2004年第3期20卷 267-272页

作者：张源毕光国东南大学移动通信国家重点实验室南京210096

A new non-parameter method is proposed to compute the throughput capacity region of high data rate (HDR) wireless networks. We first transform the task of computing the throughput capacity region into a mathematical optimization problem without introducing any additional parameters. By using a greedy algorithm to solve the optimization problem, the non-parametric characterization of the throughput capacity region of HDR can be obtained. By using the new non-parameter method, the HDR throughput capacity region can be characterized by at most N(M2-M+1)N-1 linear constraints where N is the user number and M is the rate set size. The correctness of the new method is verified by several numerical examples.

关键词： capacity region high data rate (HDR) resource allocation

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Joint eigenvalue estimation by balanced simultaneous Schur decomposition

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Journal of Southeast University(English Edition) 2006年第4期22卷 445-450页

作者：付佗高西奇东南大学移动通信国家重点实验室南京210096

The problem of joint eigenvalue estimation for the non-defective commuting set of matrices A is addressed. A procedure revealing the joint eigenstructure by simultaneous diagonalization of. A with simultaneous Schur decomposition （SSD） and balance procedure alternately is proposed for performance considerations and also for overcoming the convergence difficulties of previous methods based only on simultaneous Schur form and unitary transformations, it is shown that the SSD procedure can be well incorporated with the balancing algorithm in a pingpong manner, i. e., each optimizes a cost function and at the same time serves as an acceleration procedure for the other. Under mild assumptions, the convergence of the two cost functions alternately optimized, i. e., the norm of A and the norm of the left-lower part of A is proved. Numerical experiments are conducted in a multi-dimensional harmonic retrieval application and suggest that the presented method converges considerably faster than the methods based on only unitary transformation for matrices which are not near to normality.

关键词： direction of arrival multi-dimensional harmonic retrieval joint eigenvalue simultaneous Schur decomposition balance algorithm

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Analysis of handoff in distributed mobile communications system based on remote antenna unit selection

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Journal of Southeast University(English Edition) 2007年第2期23卷 156-161页

作者：蒋占军潘文赵新胜尤肖虎东南大学移动通信国家重点实验室

A remote antenna unit （RAU） selection model is presented, and two kinds of handoffs, intra-cell handoff （HO） and inter-cell HO, are defined in distributed mobile communications systems （DAS）. After that, an inter-cell HO model is proposed, in which the average power of the active set （AS） is used to predict the position of the mobile station （MS）. The total power of the AS and the handoff set （HOS） are utilized to determine whether an inter-cell HO is necessary. Furthermore, the relationship between HO parameters and performance metrics is studied in detail based on RAU selection. Simulation results show that both the intra-cell HO and the inter-cell HO can achieve oerfect performance by aoprooriate settings of HO parameters.

关键词： distributed mobile communications system handoff generalized cell remote antenna unit selection

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Effect of phase noise in an OFDM/OQAM system

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Journal of Southeast University(English Edition) 2003年第2期19卷 108-113页

作者：陈琦帆吴炳洋程时昕东南大学移动通信国家重点实验室南京210096

The performance of an OFDM/OQAM system under phase noise is analyzed. The analysis helps to direct the design of low cost tuners through specifying the required phase noise characteristics. Discrete time formulation of OFDM/OQAM is first derived with the square root raised cosine (SRRC) filter as the pulse-shaping filter. Then the effect of multiplicative phase noise is equivalently represented as additive white Gaussian noise (AWGN), the variance of which is given analytically. We can observe that the same result as OFDM/QAM system is derived. Lastly, all the analytical results are verified by the bit error rate (BER) degradation through Monte Carlo simulation.

关键词： OFDM/OQAM OFDM/QAM phase noise BER performance

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NBP-based localization algorithm for wireless sensor networks in NLOS environments

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Journal of Southeast University(English Edition) 2016年第4期32卷 395-401页

作者： Bui Thi Oanh 徐平平朱文祥武贵路东南大学移动通信国家重点实验室南京210096

To mitigate the impacts of non-line-of-sight（NLOS） errors on location accuracy, a non-parametric belief propagation（NBP）-based localization algorithm in the NLOS environment for wireless sensor networks is *** to the amount of prior information known about the probabilities and distribution parameters of the NLOS error distribution, three different cases of the maximum a posterior（MAP） localization problems are introduced. The first case is the idealized case, i. e., the range measurements in the NLOS conditions and the corresponding distribution parameters of the NLOS errors are known. The probability of a communication of a pair of nodes in the NLOS conditions and the corresponding distribution parameters of the NLOS errors are known in the second case. The third case is the worst case, in which only knowledge about noise measurement power is obtained. The proposed algorithm is compared with the maximum likelihood-simulated annealing（ML-SA）-based localization algorithm. Simulation results demonstrate that the proposed algorithm provides good location accuracy and considerably outperforms the ML-SA-based localization algorithm for every case. The root mean square error（RMSE）of the location estimate of the NBP-based localization algorithm is reduced by about 1. 6 m in Case 1, 1. 8 m in Case 2 and 2. 3 m in Case 3 compared with the ML-SA-based localization algorithm. Therefore, in the NLOS environments,the localization algorithms can obtain the location estimates with high accuracy by using the NBP method.

关键词： non-line-of-sight（NLOS） localization accuracy wireless sensor networks

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Performance analysis of space-time transmit diversity techniques for multi-antenna WCDMA systems

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Journal of Southeast University(English Edition) 2004年第3期20卷 261-266页

作者：杨馨方昕尤肖虎东南大学移动通信国家重点实验室南京210096

Several space-time coding based transmit diversity techniques for wideband code division multiple access (WCDMA) systems with four transmitter antennas are investigated. Performances of the rake receivers are analyzed and compared with those of the multi-antenna receive diversity techniques. Theoretical analysis shows that the multi-antenna transmit diversity techniques provide considerable performance gain at the mobile receiver in the wireless channel with less inherent multipath diversity, especially the G4 coding based scheme. Compared with the multi-antenna receive diversity techniques with the same diversity order, the transmit diversity techniques introduce much more multi-access plus multipath interference and require measures of interference suppression in the multi-user environments.

关键词： Code division multiple access Diversity reception Multipath propagation Radio transmission Receiving antennas

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