Journal on Communications

Narrowband interference suppression in vector OFDM systems

Guo-mei ZHANG,Shi-hua ZHU

2008, 29(1): 1-6. doi:1000-436X(2008)01-0001-06

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The effect of narrowband interference on the performance of vector OFDM (VOFDM) was analyzed and a narrowband interference suppression method for VOFDM was proposed.By modifying the received vector sequences,the reception over vector channels in a VOFDM system was converted to the detection in a MC-CDMA system.Then the minimum mean-square error combining (MMSEC) technique was adopted to suppress the narrowband interference.Performance analysis and simulation results show that the proposed receive method can improve the system robustness to narrowband interference.When signal-interference-ratio (SIR) is 15dB and the target bit error rate is 10^-2,the proposed method can obtain 8dB gain compared to the least square (LS) detection with the vector length being 16.

Syntax-based reordering model for phrasal statistical machine translation

Yong-zeng XUE,Sheng LI,Tie-jun ZHAO,Mu-yun YANG

2008, 29(1): 7-14. doi:1000-436X(2008)01-0007-08

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To deal with the long-distance reordering,a linguistically syntax-based reordering model was presented for phrasal statistical machine translation.In this model,the syntax structure was decomposed according to the phrase segmentation to avoid the inconsistence between phrase and syntax.The reordering sequence of the sub-structures of a parse tree was decided by the word and phrase alignments.The reordering probability of the sub-structure was calculated on the reordering probabilities of the inside nodes,which was defined as a feature function of the log-linear statistical translation model.Experimental results show that the BLEU scores of the translation results were significantly improved compared with a conventional statistical phrase-based model.Therefore,it is effective to introduce the linguistic syntax for phrase reordering.The presented reordering model is able to efficiently incorporate the syntax into the translation process of phrases.

Analysis of forwarding equipment delay upper bound by effective arrival envelop

Zhen-meng OU,Guang-zhao ZHANG,Jun-min LIU,Shao-ji HU

2008, 29(1): 15-21. doi:1000-436X(2008)01-0015-07

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In order to allocate bandwidth accurately,forwarding equipment statistical delay upper bound was explored.Effective arrival envelop was constructed via optimizing traffic sample number and violation probability,the delay upper bound was derived.Numerical result demonstrates the delay upper bound based on effective arrival envelop is much more accurate and system bandwidth utilization can be improved.

Multicell adaptive power allocation scheme based on game theory in OFDMA systems

Tian-kui ZHANG,Zhi-min ZENG,Ying-ying ZHANG

2008, 29(1): 22-29. doi:1000-436X(2008)01-0022-08

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A multicell power coordinated allocation scheme was proposed for downlink orthogonal frequency division multiple access (OFDMA) cellular systems.Transmit power levels of co-subchannels were coordinated among inter-cell,consequently inter-cell interference was mitigated and channel capacity was increased.Game theory was employed in the multicell power allocation.A multicell non-cooperative power allocation game framework was presented via pricing.The existence and uniqueness of Nash equilibrium of this game framework was analyzed,and a distributed algorithm for this game was proposed.The performance of the proposed scheme is verified by simulation in the single cell and multiple cell scenario respectively,as well as the influence of pricing factor on system performance.Simulation results show that the multicell power coordinated allocation scheme proposed will improve radio resource efficiency,increase throughput of the system,and reduce the average transmit power.

Recovery of image blocks using the method of edge orientation projections

Shi-ming GE,Yi-min CHENG,Dan ZENG,Bing-bing HE

2008, 29(1): 30-38. doi:1000-436X(2008)01-0030-09

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In compressed image transmission,channel interference often results in data missing in image blocks.A method was presented based on edge orientation projections for recovery of missing image blocks.The missing block was classified through edge orientation information of the surrounding neighborhood,and was recovered using POCS algorithm by combining frequency and spatial domain information according the class.The proposed method can restore image edge and complex texture satisfactorily.Experimental comparison with RIBMAP shows obvious improvement of the proposed method in restored image quality and robustness.

Efficiency centric reliable communication mechanism for wireless sensor networks

Xi-yuan ZHANG,Hai ZHAO,Pei-gang SUN,Jiu-qiang XU,Jian ZHU

2008, 29(1): 39-45. doi:1000-436X(2008)01-0039-07

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Reliable transfer mechanism was needed for wireless sensor network's communication link to ensure end-to-end reliability.After pointing out that traditional MAC protocol can not provide energy efficient reliable transfer,a new group-based acknowledgement mechanism,which was efficiency centric,was brought forward.And then surrounding the EPB of communication link,mathematic method was adopted to compare the performance between the new and traditional mechanisms.And the theory analysis proves that the new mechanism can reduce energy cost obviously.Meanwhile,the new mechanism requires a smaller buffer for sensor nodes through overhearing technique.Finally,performance of the group-based acknowledgement mechanism has been tested through experiment on Micaz platform,which proves that this mechanism is more suitable for the application of resource limited sensor networks.

Robust dead-beat synchronization of discrete chaotic systems and application to secure communications

Yu-xian LI

2008, 29(1): 46-50. doi:1000-436X(2008)01-0046-05

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A robust dead-beat synchronization method was presented for discrete chaotic systems using adaptive channel blind equalization and dead-beat chaotic synchronization.This method utilizes chaotic synchronization error as the energy function and evolutionary programming to train the RNN,whose output was used as the driving signal for the chaotic receiver.Furthermore,based on the robust dead-beat synchronization method,a new secure communication method was proposed.

Application of Lagrangian multipliers method in multiuser detection

Wen-long LIU,Xiao-hong MA

2008, 29(1): 51-55. doi:1000-436X(2008)01-0051-05

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The quadratic optimization problem with binary constraints was transformed into an equivalent quadratic optimization problem with equation constraints,and applied Lagrangian multipliers method to solve optimization problem with equation constraints,the relationship among the Lagrange multipliers,user information codes and channel noises was derived.Considering the special features of multiuser detection problem,a method of estimating Lagrange multipliers was presented,whereby a new multiuser detector was obtained.The numerical experiments show that the bit-error-ratio (BER) of new detector is close to that of the optimum multiuser detector and less than that of sub-optimum multiuser detectors.

Combine multi-dimension Bloom filter for membership queries

Kun XIE,Zheng QIN,Ji-gang WEN,Da-fang ZHANG,Gao-gang XIE

2008, 29(1): 56-64. doi:1000-436X(2008)01-0056-09

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Based on the analysis of multi-dimension Bloom filter(MDBF) presented before,a combine multi-dimension Bloom filter(CMBE) was presented.CMDBF adds a combine Bloom filter (CBF) to MDBF to assist in representing the whole element.When representing or querying an element,CMDBF needs two steps,the first step is representing or querying every attribute of the element with MDBF,the second step is combining all attributes to further represent or query the whole element with combine Bloom filter for further validation.Both theoretical analysis and experiment show that the CMDBF can support concise representation and approximate membership query of data set from multiple attribute dimensions and CMDBF outperforms MDBF in false positive.

Analysing nonlinear oscillation and chaos using fundamental-wave balance principle

Bing-hua HUANG,Xin-min HUANG,Shan-ge WEI

2008, 29(1): 65-70. doi:1000-436X(2008)01-0065-06

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The fundamental-wave current I_s1can be found by the theory of fundamental harmonic balance.Its flow direction represents profit and loss of active and reactive power in order to maintain self-oscillation,when the exciting source applied to the network is cut off.And it is powerfull basis of judging stability and self-excited oscillation shape and properties.Oscillation frequencyω_sand amplitude U_mof fundamental- wave solution can be found,when active and reactive power of the network obtain balance synchronously.The respective periodic solution exist inevitably.The universality of the conclusion can be spread to third-order nonlinear differential equation.It is expounded that a differential equation possessing multiple periodic solutions is the important reason of generating chaotic oscillation.Its correctness can be verified by the Simulink.

Attack simulation and signature extraction of low-rate DDoS

Zhi-jun WU,Dong ZHANG

2008, 29(1): 71-76. doi:1000-436X(2008)01-0071-06

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LDDoS (low-rate distributed denial-of-service) was a new type of DDoS attack.It had small traffic and covered by normal network traffic.LDDoS attack was so stealthy that the detection and defense approaches of traditional DDoS could not be effective.Experiments show that LDDoS attack traffic exhibit strong periodicity.Based on the periodical feature of LDDoS attack,the signatures of LDDoS attack are extracted through analyzing the cache queue of target router for the purpose of detection and defense of LDDoS attack.Statistics on the percentage of normal and attack flow in total traffic show that LDDoS attack has two signatures.Experiments on the two signatures in NS-2 platform have been conducted to detect LDDoS attack,tests result show that the extracted two signatures can reduce false positives of LDDoS attack detection schemes.

Iterative channel estimation based on the Turbo principle for UWB system

Peng-wei TENG,Yi-ming WANG,Hong-bo ZHU

2008, 29(1): 77-82. doi:1000-436X(2008)01-0077-06

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An iterative channel estimation algorithm and receiver structures based on Turbo principle were proposed for estimating channel parameters in a TH-UWB system under the realistic UWB channel model from IEEE 802.15.In each iteration,the soft-output of decoder is fed back to the channel estimation module,and used as the prior information,which means no training sequences are used.The performance of the proposed iterative channel estimation algorithm in UWB dense multipath channels is evaluated.The numerical results show that the new algorithm can efficiently estimate channel parameters,and moreover,can efficiently track the time-variant of the channel.

Role-based fine-grained delegation constraint framework in collaborative environments

Wei LIU,Jia-yong CAI,Ye-ping HE

2008, 29(1): 83-91. doi:1000-436X(2008)01-0083-09

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A role-based delegation constraint method was introduced by separating role into two parts for fine-grained controlling.Three types of delegation constraints were analyzed,including temporal,prohibition and obligation.Using these constraints,conditional delegation and constrained usage was described.The former protected accepted delegation under certain conditions against diffuseness and abuse.The later constrained the usage of permission to avoid abuses of delegated permissions.An algorithm based on the graph theory for verifying the consistency of delegation constraints was presented,which had the time complexity of O(n²).

Fair mobile payment protocol based on PPV

Fang-wei LI,Jie PAN

2008, 29(1): 92-96. doi:1000-436X(2008)01-0092-05

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A new fair pay-per-view protocol was proposed for mobile communication by integrating on the new idea of CEMBS,which satisfyied the feature of mobile communication.The protocol introduces CEMBS method in the request service phase,implements authentication and key agreement and achieves establishment on service request between two distrusted parties without the trusted network operator.The parties are undeniable,and the whole course only need three messages.The payment phase assures fair exchange between parties.The protocol satisfied fairness,non-repudiation,atomic,authentication,and security.It is also simpler,and suitable for a wide range of application.

Efficient smoothing algorithm for VBR-encoded videos

Kai-hui LI,Zhi-mei WU,Yuan-hai ZHANG,Chang-qiao XU

2008, 29(1): 97-103. doi:1000-436X(2008)01-0097-07

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Using VBR encoded media files could obtain better video quality.However,it produced traffic burst and unbalanced resource utilizations.A novel algorithm BSBS-VBR (buffer sharing and bandwidth smoothing of VBR streams) was proposed.Through computing the minimum size of a video prefix to be prefetched in advance and prefetching them on request,it allowed video server to obtain and transmit a VBR-encoded stream at a fixed rate.Through interval caching,it could keep the balance allocation of the resources,as which allocated resources for each request according to the available cache and disk bandwidth,and adjusted buffer size at run-time according to the current request distribution and available resources dynamically.With BSBS-VBR,the peak requirements of the resources can be reduced,the utility of the resources can be improved,and more users can be served.These conclusions are proved by comparing with several existing methods experimentally.

Energy consumption analysis for WLAN discovery schemes in converged networks

Jun-feng JIANG,Zhi-gang CAO

2008, 29(1): 104-108. doi:1000-436X(2008)01-0104-05

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The terminal energy consumption of WLAN discovery schemes was considered for wireless heterogeneous networks,which were the integration of 3GPP (third generation partnership project) cellular networks and WLAN (wire-less local area network).Utilizing the terminal energy consumption model proposed,the energy consumption of paging based WLAN discovery scheme and the other four WLAN discovery schemes was analyzed.Analysis results indicate that paging based scheme consumes least energy of all the schemes.The scheme that keeps the terminal periodically scanning in the cells with WLAN consumes the second least energy.It is also shown that the scheme that keeps the terminal periodic scanning in the cell with WLAN and that keeps the terminal periodic scanning in all zones consume comparable energy.

Correlation calculation decrypting for BSS-based image cryptosystem

Qiu-hua LIN,Jie DANG,Fu-liang YIN

2008, 29(1): 109-114. doi:1000-436X(2008)01-0109-06

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For a blind source separation (BSS) based method for encrypting multiple images,the multiple decrypted images by BSS may have changed order and reversed pixel values.In addition,decorrelation preprocessing must be performed prior to decryption of strongly correlated images.To solve the two problems,a novel method for image decryption was proposed based on correlation calculation since the key images are known for legal users and are independent of the original images.Specifically,the correlation matrix between the encrypted images and the key images was calculated according to the encryption equation,the decrypted images are then obtained by ignoring the smaller correlation matrix between the original images and the key images.The results of computer simulations and performance analyses demonstrate that the proposed method can provide much higher quality and much faster speed compared to the BSS decryption,and also can directly decrypt varied images.

Handover algorithm using fast DAD mechanism for hierarchical mobile IPv6

Wei-xin CHEN,Guo-dong HAN,Hong-bo LIU,Hui CAI

2008, 29(1): 115-120. doi:1000-436X(2008)01-0115-06

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To solve the problem that the duplicate address detection (DAD) in hierarchical mobile IPv6 (HMIPv6) links too time consuming,a handover algorithm based on fast DAD mechanism for HMIPv6 was proposed.By introducing the IP address allocation management (IAAM) module to establish the DAD-lookup and initiative address-generation mechanism,the proposed algorithm can greatly speed up the DAD course and be implemented easily.Simulation results showed the HMIPv6 optimized by the algorithm (F-DAD-HMIPv6) could reduce intra-domain handover delay and inter-domain handover delay to 202ms,339ms respectively and was superior to MIPv6 and HMIPv6.

Research and implement of embedded wireless mobile communication system

Xiao-nian TONG,Xing-ya AN,Xiao-pang LAN,Jiang-qing WANG

2008, 29(1): 121-124. doi:1000-436X(2008)01-0121-04

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In order to reduce hardware cost of embedded wireless mobile communication system and improve developing efficiency of embedded network protocol,the embedded wireless mobile communication terminal based on 8-bit basic MCU was proposed.Furthermore,according to software engineering principle,the general frame was designed to generate embedded network protocol by UML state machine technology.The frame converted UML state figure into implementing codes of embedded network protocol.The experiment result shows that embedded wireless mobile communication system not only reduces hardware expense but also incarnates standard and efficiency for development of embedded system software by UML state machine technology.

Modeling and power analysis for uplink of laser communication between airplane and satellite

Chun-yi CHEN,Hua-min YANG,Shou-feng TONG,Hui-lin JIANG

2008, 29(1): 125-131. doi:1000-436X(2008)01-0125-07

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Aiming at the uplink of laser communication between airplane and satellite,the factors including the ambient light,the loss of laser propagating in atmosphere,the receiving efficiency of receiver and the laser intensity fluctuation,which all can affect the link performance,were theoretically modeled and analyzed.On the basis of the modeling and analyzing,a link bit error rate (BER) model was proposed by considering on-off-keying (OOK) modulation and direct-detection combined with the Webb-Gaussian approximation of avalanche photodiode detector (APD).A numerical simulation was performed and the relationship between BER and signal laser power incident on APD was got.It shows that BER decreases while the laser power increases and an approximately log-linear relationship between decreasing speed of BER and laser power can be obtained.Finally,the minimal transmitting power,0.873W,at transmitter was computed as link could achieve 10^-7BER.

Coder selection based on context for wavelet image compression algorithm

Ying-hong ZHOU,Zheng-ming MA

2008, 29(1): 132-140. doi:1000-436X(2008)01-0132-09

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A wavelet image coding algorithm based on context selection was proposed:compares the ideal average coding cost of arithmetic coding,fixed run-length coding and variable run-length coding in the case of independently-identically distribution; analyses the increase of actual coding cost due to the existence of error of estimated probability and time-varying probability ; builds a new context template; chooses arithmetic coding,fixed run-length coding or variable run-length coding based on the proposed context model.Experimental results show that speed-up results are achieved in the new algorithm,for example,at 0.25bit/pixel,the proposed scheme saves 20% above coding time compared with arithmetic coding scheme; the proposed algorithm improves 0～0.28dB over embedded block coding with optimized truncation(EBCOT) in terms of PSNR and especially suits for low bit rate compression application.

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