Journal on Communications

Several practical coding schemes for a block of integers

Sheng-tian YANG,Pei-liang QIU

2005, 26(7): 1-7. doi:1000-436X(2005)07-0001-07

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Four coding schemes for a block of integers were proposed based on Golomb codes and extended Gamma codes.These schemes enhanced the compression performance on integer sequences with low entropy and still enjoy the simplicity of integer codes.By applying these coding schemes,a compression algorithm based on Burrows-Wheeler transform was designed.Experimental results of this algorithm indicate lossless coding rates better than those achieved by BWT-based compression algorithms using integer codes.

IPv4/IPv6 dual-stack quaternary-search routing lookup algorithm and implementation

Zhen-xing WANG,Yan-xiao ZHANG,Jiang-xing WU

2005, 26(7): 8-15. doi:1000-436X(2005)07-0008-08

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IPv4/IPv6 dual-stack core routers need high-performance integrative routing lookup.Traditional prefix-length binary-search algorithms need as more as 7 search stages to do once IPv6 routing lookup.While single-stage TCAM schemes used in core routers demand that entries be stored in prefix-length descending order relative to TCAM addresses.The operations to keep orders have disadvantageous affections to the entry updating speed and lookup continuity.Different from those algorithms based on prefix-length binary-search or single-stage TCAM,a novel prefix-range quaternary-search routing lookup algorithm was provided and a QSPE scheme was implemented with 3 stages of TCAMs in this paper.It needs only 3 search stages to complete one IPv4/IPv6 routing lookup,and does not demand to keep entries order any more.Its lookup speed is high,entry updating completes fast,and lookup continuity was enhanced.It achieves OC-768 (40Gbit/s) ports' wire-speed forwarding and satisfies IPv4/IPv6 dual-stack core routers.

New beamforming method based on fractional lower order covariance matrix

Dai-feng ZHA,Tian-shuang QIU

2005, 26(7): 16-20. doi:1000-436X(2005)07-0016-05

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Conventional array signal processing methods based on Gaussian noise assumption and second order statistics degraded under impulsive noises conditions.After introducing the statistical characteristics of stable distribution briefly,a new beamforming method based on the fractional lower order covariance matrix under alpha-stable noises conditions was proposed.The simulation results showed that the proposed method exhibited better signal to interference plus noise rate and beamforming performances.The method is more robust under both Gaussian and fractional lower order stable distribution environments than conventional method.

Optimization strategy of the resource management in grid computing based on virtual organization

Ru-chuan WANG,Guang-fa HAN,Hong-wei CHEN

2005, 26(7): 21-26. doi:1000-436X(2005)07-0021-06

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In order to improve resource manage power based on grid computing,according to the resource manage method of grid computing based on virtual organization,the traditional method's defaults were analysed,supported the concept to ameliorate the resource management with mobile agent and gave the ameliorated resource management model based on virtual organization.It gives the methodology of ameliorating resource management based on virtual organization and the way to put it into fact.

Cramér-Rao bound for blind,semi-blind and non-blind channel estimation in OFDM system

Zi LI,Yue-ming CAI,You-yun XU

2005, 26(7): 27-32. doi:1000-436X(2005)07-0027-06

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Based on the matrix formulation of OFDM signals,the CRB for blind,semi-blind and non-blind channel estimation in OFDM system was derived.The CRB for semi-blind channel estimation was a generic expression,which could be extrapolated to the CRB for blind and non-blind channel estimation.It was proved that the CRB under the linear constraint and the quadratic constraint was the same for the blind channel estimation.The performance of the channel estimation in two different OFDM systems such as CP-OFDM and ZP-OFDM were simulated.In the simulations,The correctness of the CRB and evaluate some channel estimation methods using the CRB were validated.

Signal detection for space-time block coded MC-CDMA system based on dimension-reduced blind channel estimation

Bing HU,Ping-an LI,Bian-zhang YU

2005, 26(7): 33-37. doi:1000-436X(2005)07-0033-05

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Blind signal detection for a space-time block coded multicarrier CDMA (MC-CDMA) system was considered.A decorrelating filter was applied to the receiving data vectors.Dimension-reduced signal of each user's odd and even time without multiuser access interference (MAI) were got.Blind channel estimation could be obtained by the rank-one approximation of whitened dimension-reduced data matrix.The complex scalar ambiguity was solved by exploiting the finite alphabets set of user's transmit information symbol.After estimating the channel response of all users,the least squares algorithm was applied to performing signal detection.Simulation results show the effectiveness of the proposed algorithms.

Analysis of the intermerometric noise at en/decoder in OCDMA system

Yong-jun ZHANG,Speidel J.,Wan-yi GU

2005, 26(7): 38-43. doi:1000-436X(2005)07-0038-06

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The model of each part of DS-OCDMA system would be given,the origin of interferometric noise would be introduced.Based on the thermal characteristic of the optical devices used in optical en/decoders,the reason of the interferometric noise was analyzed.Then the affect of this noise would be simulated.From the results of the outputs at optical and electronic en/decoders,it can be obtained that the interferometric noise can be reduced or even avoided,when electronic encoder and decoder are used.

Distributed scheduling algorithm for real-time network

Qin-zhou NIU,Lie-ping ZHANG,Heng-zhou YE

2005, 26(7): 44-48. doi:1000-436X(2005)07-0044-05

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According to the characteristic of real-time network based on master-slave architecture,put forward a kind of distributed assignment scheduling algorithm for real-time network,which based on EDF and executed in master nodes.It also pointed out the sufficient conditions for the approvable scheduling with this kind of scheduling algorithm.Simulation test results shows that this kind of algorithm can meet real time constraint,well adapted to scheduling for real-time network based on master-slave architecture.

Research on Parlay Gateway architecture with mutil-view of model

Xiao-qing WANG,Fang-chun YANG,Shu-bo ZHAN

2005, 26(7): 49-55. doi:1000-436X(2005)07-0049-07

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Since the shortage of practical research on Parlay Gateway architecture,a comprehensive view of it was described fully and clearly based on “ 4+1 ” view model .The logic view captured the conception and analyzed main roles and logic entities involved in Parlay Gateway.Using the thoughts of object-oriented,component-based,loosely-coupled,the development view model described the static organization of main functional component such as standard SCF API,protocol adaptation etc.The process and the physical view took into account various nonfunctional aspects of concurrency,redundancy,security and consistency.The deployment view discussed issues especially of its interconnection to the existing network.The scenario view,which combined with the others view organically,described some typical mechanisms of SCF registering,AS discovering,Framework authenticating and the third party application executing.

Group location update scheme and performance analysis for location management in mobile network

Fu-rong WANG,Lai TU,Zai-lu HUANG

2005, 26(7): 56-61. doi:1000-436X(2005)07-0056-06

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The group location update scheme in which a group location update was performed by a leader mobile terminal instead of individual update by every normal mobile terminal has been proposed.A stochastic service system model was also built to analyze the group location update scheme and individual location update scheme in the view of channel access cost.Compared with individual location update scheme,group location update scheme obviously increases channel capability and system throughput due to a significant reduction in signaling cost per update and the number of location updates.As user mobility increases or the number of users in the group increases,the advantage of the group update scheme improves.

DWT-based color image watermarking scheme of embedding watermark into the green components

Lian-shan LIU,Ren-hou LI,Qi GAO

2005, 26(7): 62-67. doi:1000-436X(2005)07-0062-06

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The scheme of embedding a scrambled watermark into the green component of the color image was proposed.The embedding process was implemented in the discrete wavelet transformation(DWT) domain.The original binary watermark image was firstly encrypted through scrambling technique,and then spread with two orthogonal pseudo-random sequences whose means were equal to zero,finally embedded into the DWT low frequency sub-band of green components.The coefficients whose energies were larger than the others were selected to hide watermark,and the hided watermark strength was determined by the energy ratio between the selected coefficients energies and the subband's mean energy.The retrieving watermark algorithm and the blind detecting algorithm were designed in accordance with the embedding scheme.The experimental results demonstrate that the proposed watermarking scheme is very robust to the attacks such as additive noise,low-pass filtering,scaling,cropping image,rows(or column) deleting and JPEG compression.

Design and implementation of a kind of disaster tolerance middleware

Shu-peng WANG,Xiao-chun YUN,Xiang-zhan YU,Ming-zeng HU

2005, 26(7): 68-75. doi:1000-436X(2005)07-0068-08

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A disaster tolerance middleware (DTM) was designed and implemented on the basis of analysis over the characters of large distributed applications and the obstacle to establish disaster tolerance systems.DTM realized the transparency of disaster tolerance efficiently.In addition,failure detection component was added into DTM,and the existing failure detector algorithm was improved.Experiments prove that the improved algorithm can improve the accuracy of failure detection.The DTM does well in practice.

GPS signal C/A code phase measurement using FFT and circular convolution

Guo-hui GONG,Si-kun LI

2005, 26(7): 76-81. doi:1000-436X(2005)07-0076-06

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A method combining FFT and circular convolution proposed could resolve this problem.The method calculated the coarse C/A code phase under low sampling rate using FFT firstly,then increased the sampling rate and calculated the fine C/A code phase using circular convolution,so as to accurately measure the GPS signal C/A code phase with lower computational burden.The method is applicable to assisted SPS receivers and high precision DSSS range acquisition.

Synchronization of spatiotemporal chaos by an exterior stochastic signal and its applications

Wei-ping JIN,Xin-long WANG

2005, 26(7): 82-88. doi:1000-436X(2005)07-0082-07

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It was shown that a unidirectionally-coupled spatiotemporal chaos system could be synchronized by an exterior stochastic signal driving a single site,and the synchronized chaos could be successfully applied to multichannel data encryption and secures information storage in which the driving random signal was used as the secret key.The effect of the periodicity of the driving signal was analyzed,and the average bit error rate caused by the multi-user interference was evaluated.An example demonstrating the secure transformation of 2D data was given with 2D-spatiotemporal chaos systems.The effectiveness,practicability and security of the proposed method for secure communication are demonstrated.

Channel adaptive error control mechanism for wireless video streaming

Xiao-yu XIU,Li ZHUO,Lan-sun SHEN

2005, 26(7): 89-95. doi:1000-436X(2005)07-0089-07

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An adaptive error protecting method for wireless video streaming was proposed.In this method,the fine-grained scalable character of MPEG-4 FGS was considered adequately,the unequal error protection scheme was adopted for different parts of encoded bit-stream according to their importance degree.Meanwhile,the method can optimally allocate channel bandwidth between the source and the channel coders to yield best video reconstruction quality.Experimental results show that,under various network conditions,compared with equal error protection and fixed unequal protection methods,the proposed scheme can always achieve better performance.

Kernel-based machine learning method and the applications to multi-user detection:a survey

Ya-tong ZHOU,Tai-yi ZHANG,Hai-yuan LIU

2005, 26(7): 96-108. doi:1000-436X(2005)07-0096-13

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The major characteristics of the feature space and present alternative methods and corresponding algorithms were analyzed.The steps to construct a novel kernel method and the future research issues were given.Finally the applications to multi-user detection using KM were explored.It is expected to understand KM comprehensively.

Discrete particle swarm optimization algorithm for multi-user detection in CDMA communication system

Yao-hua XU,Yan-jun HU,Yuan-yuan ZHANG

2005, 26(7): 109-114. doi:1000-436X(2005)07-0109-05

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Research it on discrete space,an discrete particle swarm optimization algorithm for the multiuser detection(MUD) problem in code division multiple access(CDMA) communication system was described.This approach using a new select method and search space partition strategy to improve the search quality and efficiency,analyses and simulation results show our approach has low computational complexity,and the BER property of the algorithm is better than the conventional detector,to find a new method to solve the problem of MUD in CDMA.

Downlink frequency-selective fading channel blind estimation for space-time coded MC-CDMA MIMO systems

Ai-feng REN,Qin-ye YIN,Ming LUO

2005, 26(7): 114-119. doi:1000-436X(2005)07-0114-05

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Since inherent characteristic of blind channel estimation algorithm based on subspace method,there existed an ambiguous complex coefficient between estimated channels and real channels.The downlink frequency-selective fading channel estimation problem of the space-time coded (STC) multiple-input multiple-output (MIMO) MC-CDMA systems were focused on.Based on subspace decomposition technique and the subspace orthogonality property,A blind accurate estimation scheme of downlink frequency-selective fading channels for multiuser STC MIMO MC-CDMA systems were derived.Thus,the blind identification method of ambiguous complex coefficient from single carrier systems to multi-carrier MIMO systems were generalized.Monte Carlo simulations show that when the SNR is low,the error of channel estimation is relatively small.

Cryptanalysis of a proxy multi-signature scheme

Xu-hui WU,Qing-hao SHEN

2005, 26(7): 119-122. doi:1000-436X(2005)07-0119-04

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Two forgery attacks presented on a proxy multi-signature scheme based on elliptic curves discrete logarithm problem proposed by Ji and Li.Using these forgery attacks,anyone of original signers can produce a valid proxy multi-signature.Furthermore,a new modified and secure proxy multi-signature scheme based on elliptic curves discrete logarithm problem were proposed.

Cryptanalysis and improvement of two threshold signature schemes

Qi XIE

2005, 26(7): 125-128. doi:1000-436X(2005)07-0123-06

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New threshold signature schemes withstanding the conspiracy attack were proposed by Jan and Gan,respectively.However,it would show that their schemes are insecure by presenting a conspiracy attack.Any set of the group could impersonate another set of members to sign any message without holding the responsibility.In case of disputes later,the designated clerk could open the forgery threshold signature,and all the members who were impersonated have no way to deny the signature.To overcome the weakness,a modification to the proposed schemes could satisfy the security requirement.Further,a variant with traceable signers based on the modified scheme is proposed.

Joint layered and multiple description video coding and its performance over error-prone network

Zhao-peng ZHANG,Jiang-qun NI,Chun-tao WANG

2005, 26(7): 129-135. doi:1000-436X(2005)07-0129-07

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A joint layered and multiple description coding structure for video over error-prone network was presented,which has combined the traits of both layered and multiple description coding.Firstly the characteristic,implementation environment and the transmission advantage of the proposed coding structure were analyzed theoretically.Then in two different ways and with two different layering ratio the coding structure was brought into reality.Finally the performance of the coding structure was evaluated from the result of transmission simulation over error-prone network,from which the merit of this coding structure is proved to be determined by itself,not by any specific implementation methods or the layering ratio.

Position location and direction assisted handoff algorithm in distributed wireless communications system

Zheng LI,Hai-xia WANG,Wei-ling WU

2005, 26(7): 136-139. doi:1000-436X(2005)07-0136-04

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The handoff algorithms in DWCS were divided into two types:handoff between antennas and handoff between antenna sets.It was verified that the latter was more suitable for DWCS.Subsequently,a position location and direction assisted handoff algorithm was presented for achieving better handoff performance,and the simulation has shown that the improved algorithm is not sensitive to location errors within 20m.Thus it is feasible in DWCS.

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