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Novel THP algorithms with minimum BER criterion for MIMO broadcast communications

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The Journal of china Universities of posts and Telecommunications 2009年第4期16卷 71-77页

作者： YUN Xiang,L Tie-jun school of information and communication engineering,{4. university of posts and Telecommunications,beijing 100876,china [a]school of information and communication engineering beijing university of posts and Telecommunications beijing 100876 china

In this article, two novel Tomlinson-Harashima precoding （THP） algorithms are proposed at the downlink broadcast channel of multi-user multiple-input multiple-output （MIMO） systems. The optimality criterion is the minimization of the bit error rate （BER） at the receiver with a constraint on the overall transmitted power. In these algorithms, transmit power allocation （TPA） matrix is introduced to the traditional THP algorithms as part of the precoding matrix. This leads to a power loading operation based on substreams signal to interference-plus-noise ratio （SINR） and results in improvement of the error rate performance compared with traditional THP algorithms. When the precoding loss factor is considered, further performance improvement is achieved by the enhanced algorithm.

关键词： MIMO system THP minimum bit-error rate (MBER) broadcast communication

Location based spectrum sensing performance analysis over fading channels in cognitive radio networks

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The Journal of china Universities of posts and Telecommunications 2010年第5期17卷 26-31页

作者： YAO Hai-peng,ZHOU Zheng,SUN Xuan,LI Bin school of information and communication engineering,{4. university of posts and Telecommunications,beijing 100876,china [a] school of information communication engineering Beijing University of Posts Telecommunications Beijing 100876 China

This paper analyzes the spectrum sensing performance over fading channel,in which a licensee and multiple unlicensed users coexist and operate in the licensed channel in a local *** overall average probabilities of detection and false alarm by jointly taking the fading and the locations of all secondary users into account are derived,and a statistical model of cumulate interference is *** on the cumulate interference,a closed-form expression of outage probability at the primary user’s receiver according to a specific distribution of the fading is ***,the sensing parameters so as to minimize the total spectrum sensing error and maximize the average opportunistic throughput are *** is noted that the overall average performance analysis and results here enable to benchmark the design of specific spectrum sensing algorithms.

关键词： spectrum sensing cognitive radio cumulate interference outage probability

User-perceived e-mail service QoS parameters and measurement

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The Journal of china Universities of posts and Telecommunications 2010年第3期17卷 85-90页

作者： LI Yong-zhi , LIU Feng, LEI Zhen-ming, CHEN Ling school of information and communication engineering, {4. university of posts and Telecommunications, beijing 100876, china [a] school of information communication engineering Beijing University of Posts Telecommunications Beijing 100876 China

A group of quality of service （QoS） parameters of electronic mail （e-mail） traffic are proposed from users＇ perspective. These parameters cover three fields： delay, throughput and usability. Concept and algorithm of each parameter are presented and its effect on user perceptions is described. In order to evaluate the effectiveness of these parameters, an active measurement system is implemented. Measured results show that the group of QoS parameters we proposed can be used to get a comprehensive view of user-perceived e-mail service QoS.

关键词： user perceptions e-mail service QoS active measurement

Synchronization of MIMO OFDM systems by perfect complete generalized complementary orthogonal loosely synchronous code groups

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The Journal of china Universities of posts and Telecommunications 2009年第2期16卷 1-7页

作者： WANG Jian YANG Xun LI Dao-ben school of information engineering,beijing {4. of posts and Telecommunications,beijing 100876,china [a]school of information engineering beijing university of posts and Telecommunications beijing 100876 china

This article proposes a time/frequency synchronization algorithm in the multiple input multiple output （MIMO） systems, in which the perfect complete generalized complementary orthogonal loosely synchronous code groups are used as the synchronization sequence. The synchronization algorithm is divided into four stages： 1） synchronization in time domain by signal autocorrelation; 2） synchronization in frequency domain by fast Fourier transform （FFT）; 3） multipath dissociation using coherent detection and fine time synchronization; 4. fine frequency offset estimation by phase rotation. As per the perfect complete generalized complementary orthogonal loosely synchronous code groups, the cross-correlation and out-of-phase auto-correlation for any relative shift between any two codes is always zero. This ideal property makes the time/frequency synchronization algorithm simple and efficient. The simulation results show that even in the multipath fast fading channel with low signal noise ratio （SNR）, the MIMO system can get synchronized both in the time domain and frequency domain with high stability and reliability.

关键词： MIMO OFDM synchronization complementary orthogonal code loosely synchronous (LS) code

Valiant load-balancing and regionalized routing scheme

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The Journal of china Universities of posts and Telecommunications 2010年第3期17卷 78-84页

作者： YANG Fan , WANG Zhen-kai, CHEN Jian-ya, LIU Yun-jie school of information and communication engineering, {4. university of posts and Telecommunications, beijing 100876, china [b] school of information communication engineering Beijing University of Posts Telecommunications Beijing 100876 China

Valiant load-balancing （VLB） routing scheme has drawbacks of logical full mesh, intermediate nodes （networks） and single application of topology. To address these, the authors propose a novel routing scheme called regionalized VLB （R-VLB）. Based on ideas of VLB and regionalizing, R-VLB divides the nodes of backbone network into several regions whose topological structure is logical full mesh, and combines shortest-path routing scheme and VLB routing scheme. R-VLB also achieves logical local interconnection, non-central nodes （networks） and a wide range of application of topology. The relevant theoretical analysis and simulation results show that R-VLB achieve good throughput and failure performance close to that of VLB, and it even has better delay performance. R-VLB provides an idea for the application of VLB routing scheme.

关键词： routing scheme VLB topology backbone network

Lifetime maximization of cooperative networks with mean channel gain information

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The Journal of china Universities of posts and Telecommunications 2009年第4期16卷 98-103页

作者： YANG Chang-qing,WANG Wen-bo,ZHAO Shuang,PENG Mu-gen school of information and communication engineering,{4. university of posts and Telecommunications,beijing 100876,china [a]school of information and communication engineering beijing university of posts and Telecommunications beijing 100876 china

A simple but effective relay-selection and power-allocation scheme is proposed to maximize the lifetime of decode-and-forward （DF） cooperative networks under the constraint that only the mean channel gain information is available at the transmitters. The new scheme takes both channel state information （CSI） and residual energy information （REI） into consideration. To evaluate the performance of the proposed scheme, three typical relay-selection and power-allocation schemes, i.e., maximum residual energy （MRE）, minimum transmit power （MTP） and equal transmit power （ETP） are considered. Simulation results show that the proposed scheme outperforms the MRE and the MTP in lifetime duration and outage probability, while needing much less signal overhead compared with the ETP.

关键词： cooperative commtmication lifetime relay selection power allocation Rayleigh fading

Construction of LDPC codes over GF(q) with modified progressive edge growth

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The Journal of china Universities of posts and Telecommunications 2009年第5期16卷 103-106,113页

作者： CHEN Xin , MEN Ai-dong, YANG Bo, QUAN Zi-yi school of information and communication engineering, {4. university of posts and Telecommunications, beijing 100876, china [a]school of information and communication engineering beijing university of posts and Telecommunications beijing 100876 china

A parity check matrix construction method for constructing a low-density parity-check （LDPC） codes over GF（q）（q〉2） based on the modified progressive edge growth （PEG） algorithm is introduced. First, the nonzero locations of the parity check matrix are selected using the PEG algorithm. Then the nonzero elements are defined by avoiding the definition of subcode. A proof is given to show the good minimum distance property of constructed GF（q）-LDPC codes. Simulations are also presented to illustrate the good error performance of the designed codes.

关键词： LDPC codes over GF(q) progressive edge growth large minimum distance

QoS-guaranteed multi-relay selection and power allocation optimization in cooperative systems

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The Journal of china Universities of posts and Telecommunications 2010年第6期17卷 25-31页

作者： CHEN Dan,JI Hong,LI Xi,LI Yi College of information and communication engineering,beijing {4. of posts and Telecommunications,beijing 100876,china [a] College of information communication engineering Beijing University of Posts Telecommunications Beijing 100876 China

This paper investigates the relay selection and power allocation problem in multi-user based cooperative networks,where intermediate relay nodes help source forward information to destination using decode-and-forward （DF） relaying protocol. Specifically,we propose a novel multi-relay nodes selection strategy taking both instantaneous channel state information （I-CSI） and residual energy into consideration,by which ＇emergence＇ diversity gain can be achieved and the imbalance of resource utilization can be overcome. Besides,using Largangian dual-primal decomposition and subgradient projection approach,an optimal power allocation algorithm at source and cooperative relay nodes is presented with the constraints of each user＇s individual quality of service （QoS） requirements and system total transmit power. Theoretical analysis and simulation results demonstrate that the proposed scheme can significantly improve energy efficiency,while guaranteeing a good balance between achievable data rate and average network lifetime with relatively low implementation complexity.

关键词： cooperative diversity relay selection resource allocation Lagrangian dual-primal decomposition subgradient projection

Transmit-reference UWB system based on m-sequence codes

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The Journal of china Universities of posts and Telecommunications 2010年第1期17卷 25-31页

作者： ZHAO Lin-li,Lü Tie-jun,QIAO Yong-wei school of information and communication engineering,{4. university of posts and Telecommunications,beijing 100876,china [a] school of information communication engineering Beijing University of Posts Telecommunications Beijing 100876 China

In this article, a novel transmit-reference （TR） signaling scheme is proposed for ultra-wideband （UWB） system, where by invoking m-sequence codes the reference and data pulses can be transmitted side by side to increase the data rate. This structure enables demodulation with a simple and practical autocorrelation receiver despite existence of severe inter-pulse interference （IPI） To evaluate detection performance of the new designs, closed-form expression for bit error probability （BRP） is theoretically derived and simulation results confirm the analytical results. In addition, the proposed scheme can be extended to M-ary systems to further improve the data rate and power efficiency.

关键词： UWB TR IPI m-sequence M-ary