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Achievable bit rates of cognitive user with Vandermonde precoder in cognitive radio network

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Science china(Information Sciences) 2011年第7期54卷 1471-1480页

作者： XU XiaoRong 1,ZHANG JianWu 1 & ZHENG BaoYu 2 1 College of Telecommunication Engineering,Hangzhou Dianzi university,Hangzhou 310018,china 2 institute of Signal Processing and Transmission,nanjing university of posts and telecommunications,nanjing 210003,china College of Telecommunication Engineering Hangzhou Dianzi University Hangzhou China institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing China

In cognitive radio network (CRN) where primary user (PU) and secondary user (SU) wish to communicate with their corresponding receivers simultaneously over frequency selective fading channels,the interference between PU and SU should be eliminated in order to realize spectrum *** division multiple access (PDMA) that implements Vandermonde precoder in cognitive orthogonal frequency division multiplexing (OFDM) is proposed,which benefits from the frequency selectivity of the cognitive channel to form a frequency *** precoder enables SUs to achieve higher bit rate with optimal power allocation strategy under the condition of PU interference *** and simulation results are presented to prove theoretical *** is shown that,achievable bit rates (ABR) of SU could be achieved with optimal power allocation scheme in ***,it is also verified that,with Vandermonde precoder to form PDMA,SU’s signal-to-noise ratio (SNR) and the target rate of PU could impact the ABR of SU significantly in CRN.

关键词： achievable bit rates (ABR) Vandermonde precoder precoder division multiple access (PDMA) optimal power allocation cognitive radio network (CRN)

A New Method of Reducing Assembly Delay of Speech Packets

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The Journal of china Universities of posts and telecommunications 2001年第4期8卷 34-41页

作者： YANG Zhen (nanjing university of posts and telecommunications, nanjing 210003, P.R. china) nanjing university of posts and telecommunications Nanjing 210003 P.R. China

Voice over IP ( VoIP ) and Voice over ATM ( VoA ) are two research hotspots in the fields of communication technology. One of the main problems degrading the QoS in VoIP and VoA is the longer time delay when speech packets are transmitted from a speaker to a listener. This paper discusses in detail the composition of time delay and the influence of different parts of delay on speech quality under IP and ATM network environments. The author puts forward a new method to convert usual CBR code streams into VBR streams for the purpose of reducing time delay from one terminal to another, which can avoid the dilemma between compressing the bit rates of speech sources and reducing assembly delay of speech packets.

关键词： speech communication CBR and VBR code streams time delay

On critical values concerning the evolution of the long period families

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Chinese Journal of Astronomy and Astrophysics 2009年第4期9卷 494-500页

作者： Xi-Yun Hou1,21 Astronomy Department, nanjing university, nanjing 210093, china 2 institute of Space Environment and Astronautics, nanjing university, nanjing 210093, china Astronomy Department Nanjing University Nanjing 210093 China institute of Space Environment and Astronautics Nanjing University Nanjing 210093 China

In a previous paper, we proposed another special critical value concerning the evolution of the long period family around the equilateral equilibrium points, besides the two values given by Henrard. Are there any other special critical values？ After studying the stability curves of the long period family carefully, we gave a negative answer. During the study, we found an interesting family of periodic orbits which we called the homo family. We studied the evolution of this family following the increase of μ. With these findings, we were able to explain the origin of the four branches of periodic families emanating from L4 and the stability results of the equilateral equilibrium points.

关键词： celestial mechanics

One-step estimation for varying coefficient models

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Science china Mathematics 2005年第2期48卷 198-213页

作者： TANG Qingguo & WANG Jinde Department of Mathematics, nanjing university, nanjing 210093, china institute of Sciences, PLA university of Science and Technology, nanjing 210007, china Department of Mathematics Nanjing University Nanjing China institute of Sciences PLA University of Science and Technology Nanjing China

A one-step method is proposed to estimate the unknown functions in the varying coefficient models, in which the unknown functions admit different degrees of smoothness. In this method polynomials of different orders are used to approximate unknown functions with different degrees of smoothness. As only one minimization operation is employed, the required computation burden is much less than that required by the existing two-step estimation method. It is shown that the one-step estimators also achieve the optimal convergence rate. Moreover this property is obtained under conditions milder than that imposed in the two-step estimation method. More importantly, as only one minimization operation is employed, the full asymptotic properties, not only the asymptotic bias and variance, but also the asymptotic distributions of the estimators can be derived. The asymptotic distribution results will play a key role for making statistical inference.

关键词： varying coefficient model, one-step estimation, asymptotic distribution, optimal convergence rate.

IR STUDY ON MONOMOLECULAR PARTICLE AGGLOMERATES OF POLYSTYRENE OBTAINED BY FREEZE-DRYING OF ITS DILUTE SOLUTION

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Chinese Journal of Polymer Science 2002年第4期20卷 381-383页

作者： Song Wang Qing-hua Wang Rong-shi Cheng Research Center of materials Beijing institute of Technology Beijing 100081, china Department of Chemistry nanjing university nanjing 210093, china Research Center of materials Beijing Institute of Technology 北京 100081 Department of Chemistry Nanjing University Nanjing 210093

The monomolecular particle agglomerates of polystyrenes were obtained by freeze-drying of its very dilute solutions of 1.3 x 10(-5)-2.0 x 10(-5) g/mL in benzene:cylcohexane (100:1) solvents, and they were annealed at room temperature for hundred days before use. According to C-13-NMR measurement the polystyrenes should be practically atactic. The number average molecular weights of the samples are 2.80 x 10(3), 2.00 x 10(4), and 1.55 x 10(6), respectively. The freeze-dried aPS with a molecular weight higher than 10(4) show two new IR absorption bands at 1098 and 1261 cm(-1), which are absent in the normal aPS and freeze-dried styrene oligomer. It was also found that the low molecular weight samples can only form powders, whereas the freeze-dried aPS with higher molecular weight form a mixture of powders and fibrils, of which the longer fibrils show a much stronger 1261 cm(-1) band than the shorter fibrils and the powder. It seems that the 1261 cm(-1) band corresponds to the stacking behavior of monomolecular particles.

关键词： monomolecular particles atactic polystyrene FTIR spectroscopy

Ether net Ring Protection for ITU-T G.8032

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china Communications 2012年第11期9卷 87-97页

作者： Wang Bin Wang Wennai College of telecommunications and Information Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 P. R. China Key Laboratory of Broadband Wireless Communication and Sensor Network Technology (nanjing university of posts and telecommunications) Ministry of Education Nanjing 210003 P. R. China

Ethernet Ring Protection (ERP) introduced by ITU-T G.8032 Recommendation is a new type of packet-switched network protection technology, which can provide ring automatic protection switch. However, the Filtering Database (FDB) flush method adopted in the current ERP standard has the drawback of introducing a large amount of transient traffic overshoot caused by flooded Ethernet frames right after protection switching. In this article, we propose a G.8032 ERP scheme that uses FDB flush based on area to resolve this issue and investigate how the proposed scheme deals with the traffic flooding problem. The theoretical analysis and simulation show that the proposed scheme can effectively improve the performance of the Ethernet ring by decreasing the unnecessary FDB flush in comparison with the existing approaches.

关键词： ITU-T 以太网帧环网保护分组交换网络 ERP 保护技术保护开关标准采用

A novel multi-relay cross-layer cooperative communication strategy based on Jackson queuing model

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Science china(Information Sciences) 2010年第4期53卷 842-853页

作者： XU XiaoRong1,2* & ZHENG BaoYu1 1institute of Signal Processing and Transmission, nanjing university of posts and telecommunications, nanjing 210003, china 2College of Telecommunication Engineering, Hangzhou Dianzi university, Hangzhou 310018, china institute of Signal Processing and Transmission Nanjing University of Posts and Telecommunications Nanjing China College of Telecommunication Engineering Hangzhou Dianzi University Hangzhou China

A novel multi-relay cooperative communication strategy based on Jackson queuing model is pro-posed, which is implemented via a cross-layer design between the physical (PHY) layer and the medium access control (MAC) layer. In the PHY layer, we focus mainly on system outage performance by analyzing in detail the relationship between the SNR threshold and the outage probabilities. While in the MAC layer, system model is treated as a Jackson queuing network, and the queue discipline for each node is assumed to be GI/M/1 model. System throughput and delay performance for the proposed strategy are also illustrated. Simulation results of the proposed cross-layer scheme are presented to validate our theoretical derivations. It is revealed that, the number of cooperative nodes influences system outage performance at high spectral efficiency regimes in the PHY layer while the proposed strategy provides a better throughput and delay performance than conventional schemes in the MAC layer.

关键词： multi-relay cooperative communication cross-layer design Jackson queuing model outage prob- abilities GI/M/1 model system throughput delay performance

A Novel Fractal-Based Real Time Video Encoder

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The Journal of china Universities of posts and telecommunications 2000年第3期7卷 53-59页

作者： WU Meng (Department of telecommunications Engineering, nanjing university of posts and telecommunications, nanjing 210003, P.R.china) Department of telecommunications Engineering Nanjing University of Posts and Telecommunications Nanjing 210003 P.R. China

Fractal encoding technique possesses some particular properties which make it as an attractive approach to video sequences compression. In this paper, we propose a novel fractal based encoding method for video signals, which, based on Self Transformation Systems( STS ), is combined with Motion Compensation as well as nonlinear transformation. Experiment of results of realtime image sequences show that the proposed method can achieve a very fast encoding speed and acceptable tradeoff between compression ration and decoding quality.

关键词： visual communication fractal block encoding Motion Compensation STS model

An Improved Cancellation of Nonlinear Intersymbolinter ference for Voiceband Data Transmission

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The Journal of china Universities of posts and telecommunications 1994年第2期1卷 6-22页

作者： Zhang Lijun(Department of telecommunications Engineering .nanjing university of posts and telecommunications ,nanjing , 210003 , . P. R. china )

in this paper ,an imprcoed nonltnear cancellation techn,que is proposed for ,wnioving nonlin-ear intersyde interference for voicel,and data lransmiss,on over dtspersive no,ilinear channels. A newstrecture 'cancellation first ,match and egualization later' is adopled in lhe ,wceiver. A fractionally-spaced equalizer (FSE)behind the nonlinear canceller can perform the functions of both a maitched fil-ter and a linear equalizer,and maximize the oulput signal to noise ralio . so that a perforniance im-provement of 2～ 3 dB is obtained compared with Biglteri's system￣[5].The ftrst order Volterra kernelmeasurement and adaptive recursive algorithms are used for the nonlinear channel eslimulor whichadaptively follws parameters of dispersive nonlinear channels. This approach allews a simple. and ef-fective implementalton ,as less computations are required. Simulation results for 9. 6 kbil/s data trans-mission over dispersive nonlinear channels show thal the nonlinear cancellalion proposed in this papercan reduce the probalelity of btt error by three orders of magnitude for the 16 QAM syuem.

关键词： data transmission nonlinear channel intersymbol interference (ISI ) cancellation ,non-linear channel estimetor volterra kernel