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Experimental investigation of MIMO relay channels statistics and capacity based on wideband outdoor measurements at 2.35 GHz

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science china(Information sciences) 2011年第9期54卷 1945-1956页

作者： NIE Xin 1,2,ZHANG JianHua 1,2,LIU ZeMin 1 & ZHANG Ping 1,2 1 Key Laboratory of Universal Wireless Communications,Ministry of Education beijing university of posts and telecommunications,beijing 100876,china 2 Wireless Technology Innovation Institute,beijing university of posts and telecommunications,beijing 100876,china 1. Key Laboratory of Universal Wireless Communications Ministry of Education Beijing University of Posts and Telecommunications Beijing 100876 China2. Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China

Relay,which serves to enhance the performance of future communication networks,is one of the most promising techniques for IMT-Advanced *** potential performance improvement of relay is investigated in this *** investigation consists of two *** the first step,to obtain a better understanding of the fundamental properties of relay channels,we conducted outdoor measurements at 2.35 GHz with 50 MHz bandwidth in a typical urban area of *** links constituting the relay transmission,i.e.,the link between base station and relay station,the link between relay station and mobile station and the link between base station and mobile station were measured by employing a real-time channel *** main factors that affect the MIMO channel capacity,i.e.,the channel gain and effective degrees of freedom,are *** cross-polarization discrimination was obtained by utilizing space-alternating generalized expectation-maximization *** channel parameters of the three links are statistically analyzed and *** the second step,based on the measured data,the performance of different relaying schemes,i.e.,amplify-and-forward and decode-and-forward,is *** impact of RS antenna configuration on the capacity is also *** measurement and evaluation results reveal that the relay can significantly improve the system coverage and performance.

关键词： MIMO relay channels IMT-Advanced frequency band channel characteristics relay performance evaluation

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Cross layer scheduling for real-time traffic in multiuser MIMO-OFDMA systems

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The Journal of china Universities of posts and telecommunications 2009年第3期16卷 24-29页

作者： SUN Qiao-yun,TIAN Hui,DONG Kun,ZHANG Ping Key Laboratory of Universal Wireless Communications,Ministry of Education,beijing university of posts and telecommunications,beijing 100876,china [a]Key Laboratory of Universal Wireless Communications Ministry of Education beijing university of posts and telecommunications beijing 100876 china

A novel cross layer scheduling algorithm is proposed for real-time （RT） traffic in multiuser downlink multiple-input multiple-output orthogonal frequency division multiple access （MIMO-OFDMA） wireless systems. The algorithm dynamically allocates resources in space, time and frequency domain based on channel state information （CSI）, users＇ quality of service （QoS） requirements and queue state information （QSI）. To provide higher data rate and spectrum efficiency, adaptive modulation and coding （AMC） is employed. The proposed algorithm can improve cell throughput and increase the number of users that can be supported while guaranteeing users＇ QoS requirements and fairness among all users. Simulation results indicate that the proposed algorithm can achieve superior performance.

关键词： MIMO-OFDMA cross layer QoS AMC

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Relationship between Low Temperature Toughness and Microstructure in Low Activation Fe-Cr-Mn(W,V)Steel for Fusion Reactors

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International Journal of Minerals,Metallurgy and Materials 1999年第2期13卷 111-115页

作者： Benfu Hu Chengchang jia(Material science and Engineering school, university of science and Technology beijing, beijing 100083, china) Material science and Engineering school University of Science and Technology Beijing Beijing 100083 China

Fe-Cr-Mn (W, V) austenite steel was researched in order to supply a theory base for the first wall materials of fusion *** included vacuum melting, forging, annealing, solution treatment, Charpy impact tests and microstructure observation. Theresults show that the imped value decreases with the test temperature decreasing. In this system, there is ductile/brittle transition. Themechanism of this decrease of the impact value is considered to be due to γ - ε transformation in sub-stable austenite steel and stoppingoverlapping sacking fault by grain boundaries in stable austenite steel.

关键词： fusion reactor first wall materials low temperature toughness Fe-Cr-Mn system

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Context-aware end-to-end QoS diagnosis and quantitative guarantee based on Bayesian network

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The Journal of china Universities of posts and telecommunications 2010年第6期17卷 106-112页

作者： LIN Xiang-tao,CHNEG Bo,CHEN Jun-liang,QIAO Xiu-quan State Key Laboratory of Networking and Switching Technology,beijing university of posts and telecommunications,beijing 100876,china [a] State Key Laboratory of Networking Switching Technology Beijing University of Posts telecommunications Beijing 100876 China

To support quality of service （QoS） management on current Internet working with best effort,we bring forth a systematic approach for end-to-end QoS diagnosis and quantitative guarantee. For QoS diagnosis,we take contexts of a service into consideration in a comprehensive way that is realized by exploiting causal relationships between a QoS metric and its contexts with the help of Bayesian network （BN） structure learning. Context discretization algorithm and node ordering algorithm are proposed to facilitate BN structure learning. The QoS metric is diagnosed to be causally related to its causal contexts,and the QoS metric can be quantitatively guaranteed by its causal contexts. For quantitative QoS guarantee,those causal relationships are first modeled quantitatively by BN parameter learning. Then,the QoS metric is guaranteed to certain value with a probability given its causal contexts tuned to suitable values,that is,quantitative QoS guarantee is reached. Simulations with three sequential stages：context discretization,QoS diagnosis and quantitative QoS guarantee,on a peer-to-peer （P2P） network,are discussed and our approach is validated to be effective.

关键词： context context discretization QoS qualitative diagnosis QoS quantitative guarantee Bayesian network

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A BATCH ARRIVAL RETRIAL QUEUE WITH STARTING FAILURES,FEEDBACK AND ADMISSION CONTROL

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Journal of Systems science and Systems Engineering 2010年第3期19卷 306-320页

作者： Jinting WANG Peng-Feng ZHOU Department of Mathematics,school of science,beijing Jiaotong university,beijing,china Department of Mathematics School of Science Beijing Jiaotong University Beijing China

This paper is concerned with the analysis of a feedback M^[X]/G/1 retrial queue with starting failures and general retrial times. In a batch, each individual customer is subject to a control admission policy upon arrival. If the server is idle, one of the customers admitted to the system may start its service and the rest joins the retrial group, whereas all the admitted customers go to the retrial group when the server is unavailable upon arrival. An arriving customer （primary or retrial） must turn-on the server, which takes negligible time. If the server is started successfully （with a certain probability）, the customer gets service immediately. Otherwise, the repair for the server commences immediately and the customer must leave for the orbit and make a retrial at a later time. It is assumed that the customers who find the server unavailable are queued in the orbit in accordance with an FCFS discipline and only the customer at the head of the queue is allowed for access to the server. The Markov chain underlying the considered queueing system is studied and the necessary and sufficient condition for the system to be stable is presented. Explicit formulae for the stationary distribution and some performance measures of the system in steady-state are obtained. Finally, some numerical examples are presented to illustrate the influence of the parameters on several performance characteristics.

关键词： Batch arrival feedback repair retrial queue starting failure

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Secure communication by generalized chaotic synchronization

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Journal of university of science and Technology beijing 2003年第2期10卷 75-78页

作者： Lequan Min, Xianhua Zhang, and Miao YangApplied science school, university of science and Technology beijing, beijing 100083, china Applied science school University of Science and Technology Beijing Beijing 100083 China

Chaotic communication is a rather new and active field of research. Althoughit is expected to have promising advantages, some investigators provide evidences that chaoticcommunication is not safety. This letter provides a new chaotic secure communication scheme based ona generalized synchronization theory of coupled system. The secret message hidden in the chaoticsource signal generated via the scheme is very difficult to be unmasked by so-called nonlineardynamic forecasting technique. One example for Internet communications was presented to illustratethe security of our scheme.

关键词： secure communication generalized chaotic synchronization Internet

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Thermodynamic Properties of Mn-P and Fe-Mn-P Melts

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International Journal of Minerals,Metallurgy and Materials 2000年第1期14卷 10-13页

作者： Jian Zhang Rong Zhu Metallurgy school, university of science and Technology beijing, beijing 100083, china Univ Sci & Technol beijing Met Sch Beijing 100083 Peoples R China

Based on the phase diagrams and the coexistence theory of metallic melts structure involving compound formation, the cal- culating models of mass action concentrations for Mn-P and Fe-Mn-P melts have been formulated. The calculated mass action concen- trations agree well with the corresponding measured activities, this in turn shows that the deduced models can reflect the structural char- acteristics of the melts concerned and there isn't any saturation of phosphorus in both melts.

关键词： activity dephosphorization the coexistence theory mass action concentration

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Relaying strategy for peer-to-peer content distribution based on genetic algorithm

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The Journal of china Universities of posts and telecommunications 2010年第2期17卷 85-91页

作者： HE Qian ,MENG Xiang-wu,SHANG Yan-lei,CHEN Jun-liang State Key Laboratory of Networking and Switching Technology,beijing university of posts and telecommunications,beijing 100876,china [a] State Key Laboratory of Networking Switching Technology Beijing University of Posts telecommunications Beijing 100876 China

This article proposes a cooperative relaying strategy to efficiently utilize the relaying resources of Interact service providers （ISPs）, speedup distribution and save server bandwidth costs. ISPs cooperatively relay for each other, and peers assist in distributing and fetching the content as near as possible. Base on the fluid model, a constrained model is derived to get optimized global distribution performance in the channel-based system with limited relaying resources. The multi-objectives of the model are minimizing the average distribution time and the distribution time of the slowest channel. Genetic algorithm （GA） is designed to solve the optimization problem. The relaying strategy based on GA can be run periodically to update the allocation policy of ISPs. The distribution performance of the relaying strategy is analyzed in the experiments and results show that GA can provide proper solutions for various network topologies.

关键词： content distribution peer-to-peer genetic algorithm cooperative relaying resource allocation

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EXIT analysis of M-algorithm based MIMO detectors and LDPC code design optimization

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science in china(Series F) 2009年第12期52卷 2248-2258页

作者： YOU MingHou1,2, TAO XiaoFeng1,2, CUI QiMei1,2 & ZHANG Ping1,2 1 Wireless Technology Innovation Institute, beijing university of posts and telecommunications, beijing 100876, china 2 Key Laboratory of Universal Wireless Communications, (beijing university of posts and telecommunications), Ministry of Education, beijing 100876, china Wireless Technology Innovation Institute Beijing University of Posts and Telecommunications Beijing 100876 China Key Laboratory of Universal Wireless Communications (Beijing University of Posts and Telecommunications) Ministry of Education Beijing 100876 China

This paper investigates joint design and optimization of both low density parity check （LDPC） codes and M-algorithm based detectors including iterative tree search （ITS） and soft-output M-algorithm （SOMA） in multiple-input multiple-output （MIMO） systems via the tool of extrinsic information transfer （EXIT） charts. First, we present EXIT analysis for ITS and SOMA. We indicate that the extrinsic information transfer curves of ITS obtained by Monte Carlo simulations based on output log-likelihood rations are not true EXIT curves, and the explanation for such a phenomenon is given, while for SOMA, the true EXIT curves can be computed, enabling the code design. Then, we propose a new design rule and method for LDPC code degree profile optimization in MIMO systems. The algorithm can make the EXIT curves of the inner decoder and outer decoder match each other properly, and can easily attain the desired code with the target rate. Also, it can transform the optimization problem into a linear one, which is computationally simple. The significance of the proposed optimization approach is validated by the simulation results that the optimized codes perform much better than standard non-optimized ones when used together with SOMA detector.

关键词： MIMO systems iterative receiver LDPC codes code optimization EXIT charts M-algorithm

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ENERGY FLOWS IN COMPLEX ECOLOGICAL SYSTEMS:A REVIEW

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Journal of Systems science & Complexity 2009年第3期22卷 345-359页

作者： Jiang ZHANG Department of Systems science,school of Management,beijing Normal university,beijing 100875,china. Department of Systems science School of Management Beijing Normal University Beijing 100875 China

Energy flow drives the complex systems to *** allometric scaling as the universalenergy flow pattern has been found in different scales of ecological *** reflects the generalpower law relationship between flow and *** underlying mechanisms of energy flow patterns areexplained as the branching transportation networks which can be regarded as the result of systematicoptimization of a biological target under *** flows in the ecological system may bemodelled by the food web model and population dynamics on the *** paper reviews thelatest progress on the energy flow patterns,explanatory models for the allometric scaling and modellingapproach of flow and network evolution dynamics in ***,the possibility of generalizingthese flow patterns,modelling approaches to other complex systems is discussed.

关键词： Allometric scaling energy flow flows in complex systems food web.

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