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Improved Kalman filter channel estimation method for OFDM systems in fast time-varying environment

Journal of Southeast University(English Edition) 2005年第4期21卷 389-392页

作者：宋晓晋宋铁成沈连丰陆苏东南大学移动通信国家重点实验室南京210096

Under analyzing several characteristics of frequency-selective fast fading channels, such as large Doppler spread and multi-path interference, a low-dimensional Kalman filter method based on pilot signals is presented for the channel estimation of orthogonal frequency division multiplexing （OFDM） systems. For simplicity, a one-dimensional autoregressive （AR） process is used to model the time-varying channel, and the least square （LS） algorithm based on pilot signals is adopted to track the time-varying channel fading factor a. The low-dimensional Kalman filter estimator greatly reduces the complexity of the high-dimensional Kalman filter. To utilize the relationship of fading channel in frequency domain, a minimum mean-square-error （MMSE） combiner is used to refine the estimation results. The simulation results in the frequency band of 5.5 GHz show that the proposed method achieves a good symbol error rate （SER） performance close to the theoretical bound of ideal channel estimation.

关键词： channel estimation orthogonal frequency division multiplexing （OFDM） least square （LS） minimum mean-square-error （MMSE）

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Multi-access performance of DS UWB systemunder indoor dense multi-path channel

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Journal of Southeast University(English Edition) 2005年第4期21卷 393-397页

作者：樊祥宁倪剑强毕光国东南大学移动通信国家重点实验室南京210096

The performance of multi-user code to direct spreading bi-phase shift keying （DS-BPSK） direct impulse ultra wideband （UWB） systems under indoor multi-user and multi-path environment is analyzed and simulated. The system output signals with Rake receiver are derived, then a simple and practical code selection scheme is given; i. e., with a large occupation to empty ratio of the repeating pulses, directly choosing those random or pseudo-random user codes with enough length and good co-relative orthogonal features will make the performance of DS-BPSK approximate the optimum and, so there is no need to carefully design the code or its type. The system multi-access performances are simulated using Gold sequence and PN codes as multi-user codes under CMI-CM4 multi-path channels. Simulation results prove that the proposed scheme is feasible.

关键词： ultra wideband multi-access multi-path Gold code direct sequence Rake

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Downlink cooperative beamforming for MIMO cellular systems

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Journal of Southeast University(English Edition) 2010年第3期26卷 379-383页

作者：张源东南大学移动通信国家重点实验室南京210096

In downlink cellular multiple users in multiple cells systems using beams, the should cooperate to generate beams to improve the spectrum efficiency. A mathematical model for the multi-cell multi-user downlink transmission is established, and the gradients of the variables including beamfonning filters, receiving filters and transmitting power are calculated. Then, a gradient-project-based cooperative beamforming scheme is proposed in which each user iteratively adjusts bearnforming variables in the direction of the gradients and projects onto feasible spaces. The information exchange protocol needed to support the scheme is also described. Simulation results show that the proposed scheme can achieve an average spectral efficiency of about 5 bit/（ s · Hz · cell）. The results show that cooperative beamforming can improve the spectrum efficiency of the cellular systems.

关键词： cellular system mutiple-input mutiple-output （MIMO） cooperative beamforming spectral efficiency

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Adaptive channel estimation based on pilot signals and transform-domain processing in SISO/MIMO OFDM systems

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Journal of Southeast University(English Edition) 2005年第3期21卷 249-253页

作者：宋铁成尤肖虎沈连丰宋晓晋东南大学移动通信国家重点实验室南京210096

Based on the transform-domain characteristics of pilot signals,a band suppression filter is used as a transform-domain filter to restrain the interference of noise in channel *** performance effect on channel estimation for an orthogonal frequency division multiplex （OFDM） system by different energy coefficients in the transform domain and the energy coefficient under the different signal-to-noise ratios （SNR） are also analyzed.A new energy coefficient expression is *** is theoretically proven that dynamically selecting an energy coefficient can significantly improve the performance of channel *** results show that the proposed algorithm can achieve better performance close to the theoretic bounds of perfect channel estimation. The algorithm is adapted to single-input single-output （SISO） OFDM and multi-input multi-output （MIMO） OFDM systems.

关键词： adaptive channel estimation orthogonal frequency division multiplex （OFDM） transmit diversity

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Different known guard intervals for single/multi-carrier transceiver

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Journal of Southeast University(English Edition) 2006年第1期22卷 11-15页

作者：李玮程时昕陈明东南大学移动通信国家重点实验室南京210096

To enhance the bandwidth efficiency of the guard interval （GI） assisted wireless communication system, an attractive scheme is proposed, which combines the functions of pilots and the GI together, so that the pilot resource used for estimating channel state is saved. Based on the proposed different known guard intervals （DKGI）, the time-domain channel estimation can be simply applied on the receiver side. After channel estimation, the receiver can employ the cyclic convolution restoring （CCR） function to reconstruct the cyclical convolution relationship between the signal and the channel, by which the receiver can also achieve good performance through the conventional 1-tap frequency domain equalization （FDE）.

关键词： cyclic prefix zero padding fixed symbol padding channel estimation

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基于微带无源电路的宽带毫米波分谐波混频器

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红外与毫米波学报 2021年第1期40卷 33-37页

作者：徐杰许正彬郭健钱澄赵涤燹东南大学毫米波国家重点实验室江苏南京210096 东南大学移动通信国家重点实验室江苏南京210096 紫金山实验室江苏南京211111

设计了一款基于微带结构的宽带毫米波分谐波混频器。混频器中引入了短路结构的宽带射频滤波器以及一个高性能本振-中频双工器,这些无源电路能够抑制空闲组合频率,同时为中频、射频以及本振信号提供合适的回路。测试结果表明,本文设计的... 详细信息

设计了一款基于微带结构的宽带毫米波分谐波混频器。混频器中引入了短路结构的宽带射频滤波器以及一个高性能本振-中频双工器,这些无源电路能够抑制空闲组合频率,同时为中频、射频以及本振信号提供合适的回路。测试结果表明,本文设计的毫米波分谐波混频器射频工作频率为27~48 GHz,中频工作频率宽至6 GHz.在整个工作频段内上、下变频损耗均小于12.5 dB。当射频为33 GHz,中频为1 GHz时,上变频、下变频达到最小变频损耗分别为8.2 dB和7.5 dB。

关键词：毫米波分谐波混频器微带宽带

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Distribution algorithm of entangled particles for wireless quantum communication mesh networks

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Journal of Southeast University(English Edition) 2015年第4期31卷 450-456页

作者：王霄峻施丽慧占海涛项睿清余旭涛东南大学移动通信国家重点实验室南京210096 东南大学毫米波国家重点实验室南京210096

With ensured network connectivity in quantum channels, the issue of distributing entangled particles in wireless quantum communication mesh networks can be equivalently regarded as a problem of quantum backbone nodes selection in order to save cost and reduce complexity. A minimum spanning tree（ MST）-based quantum distribution algorithm（ QDMST） is presented to construct the mesh backbone network. First, the articulation points are found,and for each connected block uncovered by the articulation points, the general centers are solved. Then, both articulation points and general centers are classified as backbone nodes and an M ST is formed. The quantum path between every two neighbor nodes on the MST is calculated. The nodes on these paths are also classified as backbone nodes. Simulation results validate the advantages of QDMST in the average backbone nodes number and average quantum channel distance compared to the existing random selection algorithm under multiple network scenarios.

关键词： wireless quantum communication networks entangled particles distribution wireless mesh networks minimum spanning tree

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Employing temporal channel correlation in user selection for MIMO broadcast systems

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Journal of Southeast University(English Edition) 2008年第1期24卷 1-5页

作者：王静蒋占军王炎尤肖虎东南大学移动通信国家重点实验室南京210096

Taking the time varying nature of wireless channels into account, two user selection schemes with lower complexity are developed for multiple-input multiple-output broadcast （MIMO BC）systems. According to the relationship between coherence time and Doppler frequency, an information frame is divided into several segments. At the beginning of each segment, the user selection is carded out with the greedy selection algorithm. In the simplified user selection algorithms employing the temporal correlation （SUSTC）, the selection results are applied for all the remaining slots in each segment. But in the improved simplified user selection algorithms employing the temporal correlation（ISUSTC）, at the remaining slots, users are kept with favorable channel conditions selected at the previous slot, and other users are updated from the candidate pool to communicate simultaneously. Simulations show that compared with the greedy user selection method, the proposed algorithms can reduce the selection complexity with a little sum capacity loss.

关键词： user selection multiple-input multiple-outputbroadcast temporal channel correlation

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Improved parallel weighted bit-flipping algorithm

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Journal of Southeast University(English Edition) 2009年第4期25卷 423-426页

作者：刘晓健赵春明吴晓富东南大学移动通信国家重点实验室南京210096

An improved parallel weighted bit-flipping（PWBF） algorithm is presented. To accelerate the information exchanges between check nodes and variable nodes, the bit-flipping step and the check node updating step of the original algorithm are parallelized. The simulation experiments demonstrate that the improved PWBF algorithm provides about 0. 1 to 0. 3 dB coding gain over the original PWBF algorithm. And the improved algorithm achieves a higher convergence rate. The choice of the threshold is also discussed, which is used to determine whether a bit should be flipped during each iteration. The appropriate threshold can ensure that most error bits be flipped, and keep the right ones untouched at the same time. The improvement is particularly effective for decoding quasi-cyclic low-density paritycheck（QC-LDPC） codes.

关键词： low-density parity-check（LDPC） parallel weighted bit-flipping（PWBF） improved modified weighted bit-flipping （IMWBF） algorithm weighted-sum weighted bit-flipping （WSWBF） algorithm

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多个TCP连接的拥塞丢包模型

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电子学报 2002年第7期30卷 990-994页

作者：陈相宁王京程时昕陈明蒋朱成清华大学微波与数字通信国家重点实验室北京100084 东南大学移动通信国家重点实验室江苏南京210096

本文提出了有关TCP连接的拥塞丢包分析模型 .网络瓶颈一般承载许多TCP连接 ,瓶颈处不可避免的拥塞和缓存溢出 ,是导致网上丢包的主要原因 .网络瓶颈处的行为很大程度上左右了网络性能 .本文的模型估计了存在大量持续TCP连接时 ,网络瓶... 详细信息

本文提出了有关TCP连接的拥塞丢包分析模型 .网络瓶颈一般承载许多TCP连接 ,瓶颈处不可避免的拥塞和缓存溢出 ,是导致网上丢包的主要原因 .网络瓶颈处的行为很大程度上左右了网络性能 .本文的模型估计了存在大量持续TCP连接时 ,网络瓶颈的丢包概率和网络传输中断概率 ,给出了对实际网络的良好近似 .这对于研究TCP对网络性能的影响 ,提出改善网络性能的新算法 ,以及分析 (从长远来看 )TCP还应做哪些改进 ,都是非常有用的 .

关键词：多TCP连接拥塞控制丢包模型 TCP协议网络瓶颈

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