Journal of Xidian University 2012 Vol.39
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Modeling and optimization of access opportunity in cognitive radio
HAN Weijia;LI Jiandong;YAO Junliang;LI Zan
J4    2012, 39 (1): 1-6.   DOI: 10.3969/j.issn.1001-2400.2012.01.001
Abstract1789)      PDF(pc) (572KB)(1256)       Save

This paper proposes jointly optimizing the access opportunity and spectrum sensing to achieve the maximum efficiency of spectrum utilization for the secondary user. In cognitive radio, the opportunistic access interwinded with spectrum sensing plays a key role in determining the performance of the secondary system. However, current related research neglects the relationship between primary user and secondary user in the spatial domain, which leads to incorrect evalution of the quantity of avaliable access opportunity for the secondary user. To deal with this problem, a closed-form function is derived to calculate the secondary medium access probability with regard to the impact of spectrum sensing and user spatial distribution. By using this derived closed-form function, the secondary user can obtain the optimum sensing configuration to ensure the efficient spectrum utilization of the secondary system. Simulation results show the correctness of the closed-form function and the efficiency of the related optimization.

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Accelerated life testing for the ring laser and the method  for calculating the characteristic life
WU Xin;SHI Shunxiang;LIU Jifang;MA Lin;SUN Yanling
J4    2012, 39 (1): 7-10+97.   DOI: 10.3969/j.issn.1001-2400.2012.01.002
Abstract1141)      PDF(pc) (415KB)(973)       Save

Constant-stress accelerated Life test is a rapid and effective method for obtaining the failure data and making life prediction of the electric component. This paper first applies this method for the He-Ne ring laser. A new prior distribution function based on the distribution of the life test data of the He-Ne ring laser is introduced. According to accelerated life equations, formulation of life prediction of the He-Ne ring laser is obtained and test data of the He-Ne ring laser are also analyzed.This method which was proved by experimentation not only precisely estimates the life of the He-Ne ring laser, but also considerablely shortens the test cyclebut.

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Lattice-reduction-aided detection in spatial correlated MIMO channels
LI Jiandong;CHEN Rui;LI Changle;LIU Wei;CHEN Dan
J4    2012, 39 (1): 11-16+22.   DOI: 10.3969/j.issn.1001-2400.2012.01.003
Abstract1466)      PDF(pc) (612KB)(1103)       Save

To overcome the drawback that the diversity order of the traditional linear MMSE detection algorithm decreases with the increase of the correlation coefficient, a lattice-reduction-aided MMSE (LRA-MMSE) detection algorithm is proposed for spatial correlated MIMO channels. The LRA-MMSE detection algorithm considers the effect of spatial correlation in the algorithm design and takes advantage of the complex Lenstra-Lenstra-Lovász (LLL) algorithm so that its BER (bit error rate) is several orders of magnitude smaller than that of the traditional linear MMSE detection at a high SNR (signal to noise ratio). Theoretical analysis and simulation results show that with QPSK modulation and the MMSE channel estimator at the receiver, the uncoded BER of the LRA-MMSE detector is lower than that of the traditional linear MMSE detector if the bit SNR (Eb/N0) is greater than 18dB, while the coded BER of the LRA-MMSE detector is lower than that of the traditional linear MMSE detector if Eb/N0 is greater than 16dB when (2,1,3) convolutional channel coding and Viterbi decoding are adopted under the Kronecker correlated flat fading channel. Furthermore, the diversity order of the LRA-MMSE detector in the correlated MIMO channel is equal to the number of the receive antenna N.

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Cited: Baidu(2)
Fast OFDM modulated signal recognition algorithm
ZHU Yanrui;TIAN Bin;AN Jinkun;SUN Yongjun;YI Kechu
J4    2012, 39 (1): 17-22.   DOI: 10.3969/j.issn.1001-2400.2012.01.004
Abstract1406)      PDF(pc) (595KB)(1099)       Save

The intrinsic time-scale decomposition (ITD) method is a novel algorithm for time-frequency analysis, which can express the dynamic information of non-stationary signals with precise instantaneous parameters. An OFDM modulation recognition algorithm is proposed based on the ITD and the circular data analysis methods. The algorithm extracts three parameters as a co-feature vector to distinguish the OFDM from single carrier modulations. The impact of the carrier frequency, symbol rate and sampling rate on the recognition performance is also considered. The intermediate frequency signal can be processed directly, avoiding the carrier recovery process. Simulation results show that the algorithm can distinguish the OFDM from single carriers successfully even under a low SNR, and that it is also robust to system parameters.

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Cited: Baidu(6)
Design and performance analysis of symbol interleaved  serially concatenated continuous phase modulation
SUN Jinhua;WU Xiaojun;XIANG Xi
J4    2012, 39 (1): 23-27+61.   DOI: 10.3969/j.issn.1001-2400.2012.01.005
Abstract1064)      PDF(pc) (597KB)(910)       Save

Serially concatenated continuous phase modulation (SCCPM) is a kind of constant envelope concatenated coding and modulation with high power efficiency and bandwidth efficiency. SCCPM with symbol-wise interleaving is studied in this paper. Compared with the traditional bit-wise interleaving scheme, SCCPM with symbol-wise interleaving has a better performance in convergence threshold but a higher error floor. The influence of system parameters such as outer code, iteration number, interleaver length, baseband shaping pulse on the system performance is given through theoretical analysis and simulation. Finally this paper presents some design rules for SCCPM with symbol-wise interleaving.

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Research on Bayesian radar adaptive detection
ZHOU Yu;ZHANG Linrang;LIU Nan
J4    2012, 39 (1): 28-33.   DOI: 10.3969/j.issn.1001-2400.2012.01.006
Abstract1199)      PDF(pc) (530KB)(1010)       Save

We consider the problem of detecting a signal of interest in the presence of Gaussian noise with the unknown covariance matrix (CM). The traditional approach relies on modeling CM as a deterministic parameter, and its maximum likelihood (ML) estimation is derived when designing the adaptive detector. The ignorance of prior distribution incurs performance loss when there are only a few training data. In this paper, a different approach is proposed which models CM as a random parameter with inverse Wishart distribution. Under this assumption, the maximum a-posteriori (MAP) estimation of CM is derived. The MAP estimate is in turn used to yield the Bayesian version of the Rao and Wald detector. And the importance of the a priori knowledge can be tuned through the scalar variable. The devised detectors remarkably outperform the non-Bayesian Rao and Wald test in the presence of strongly heterogeneous scenarios (where a very small number of training data are available).

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Cited: Baidu(5)
New image super-resolution restoration method by NSCT
YANG Zhenping;NIU Haijun;DING Lei
J4    2012, 39 (1): 34-37+85.   DOI: 10.3969/j.issn.1001-2400.2012.01.007
Abstract1401)      PDF(pc) (1697KB)(1243)       Save

Based on the multi-scaled and multi-directional properties of Nonsubsampled Contourlet Transform (NSCT), an image super-resolution restoration algorithm is proposed. The algorithm includes image registration and image restoration. First sub-pixel image registration is applied. Then a fused image can be obtained from the registered images by performing NSCT and the inverse NSCT. After the low frequency and high frequency of the fused image are interpolated, a high-resolution image can be obtained by performing the inverse NSCT. Experimental results show that the proposed algorithm outperforms the traditional algorithms in terms of both visual quality and objective evaluation criteria.

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Cited: Baidu(11)
New method for removing the hidden face in  the MOM-PO hybrid method
DANG Xiaojie;YUAN Haobo;WANG Nan;LIANG Changhong
J4    2012, 39 (1): 38-41.   DOI: 10.3969/j.issn.1001-2400.2012.01.008
Abstract1342)      PDF(pc) (1103KB)(918)       Save

It is necessary to judge the lit region and the shadow region in the PO area when we use the MOM-PO hybrid method. This paper proposes a highly efficient method to complete this hidden face removal. First of all, it divides all the triangles in the geometric model into groups by the commonly-used Z-Buffer method, thus decreasing the time-expenditure. And then a strict method is adopted to find the lit triangles with high accuracy. Finally, we apply the domain decomposition method to decrease the memory requirement. A numerical experiment shows this new method can obtain a more accurate result than the Z-Buffer method by 18.6% at the expense of only a little more time and memory.

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Delay-independent asynchronous dynamic priority arbiter  for the network on chips
YANG Yanfei;ZHU Zhangming;ZHOU Duan;YANG Yintang
J4    2012, 39 (1): 42-48+110.   DOI: 10.3969/j.issn.1001-2400.2012.01.009
Abstract1450)      PDF(pc) (819KB)(1055)       Save

This paper proposes a delay-independent asynchronous dynamic priority arbiter to improve the quality of service in the asynchronous router of the general-purpose network on chips. In an arbitration period, by comparing the priority of the data packets with request signals, the arbiter will output the data packets in the sequence of descending priority. The packets with equal priority are outputted serially so that it resolves the problems of requests with fixed priority in conventional static arbiters, and improves the scalability of the arbiter and router. The arbiter is implemented based on 0.18μm standard CMOS technology. Results have shown that the average response time is 0.92ns, and that the average dynamic power consumption is 0.75mW per request, which can be used for the asynchronous router of the general-purpose network on chips.

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New model decomposed method to simulate the  crosstalk between vias
SHEN Zhenning;ZHUANG Yiqi;ZENG Zhibin
J4    2012, 39 (1): 49-55+104.   DOI: 10.3969/j.issn.1001-2400.2012.01.010
Abstract1154)      PDF(pc) (1550KB)(1117)       Save

A model decomposed method is proposed for efficient simulation of crosstalk between vias in high speed circuits. The 3D interconnect structure is first decoupled into a power-ground plane pair and a microstrip line structure which are coupled in the vias, then we solve each parts by using different methods, and finally, the equivalent circuits of each part are integrated to simulate the system performance. Compared with full wave simulation, the simulation time is reduced from 187 minutes to 4 minutes with considerable accuracy. The structure of the printed circuit board and vias that affect the system performance are analyzed carefully, and it is found that the crosstalk coefficient is approximately proportional to the magnitudes of transform impedance in the location of vias in the frequency domain. Some engineering implications on reducing crosstalk noise in practical PCB, such as using a thin dielectric layer, adding decoupling capacitors and adjusting the locations of the vias, are discussed through a series of simulation. The time domain simulation result shows that the magnitude of crosstalk noise is reduced by over 98% when the interconnect structure is designed properly.

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Stable and efficient NURBS MOM-PO method
HE Zhili;HUANG Kai;JIANG Xiaobo;LIANG Changhong
J4    2012, 39 (1): 56-61.   DOI: 10.3969/j.issn.1001-2400.2012.01.011
Abstract1151)      PDF(pc) (824KB)(1006)       Save

An efficient stable moments-physics optics (MOM-PO) hybrid method is proposed to calculate the disturbed pattern of an antenna around an electrically large platform modeled with Non Uniform Rational B Spline (NURBS) surfaces. Modifying the impendence matrix is used to implement the interaction of the MOM region and PO region for avoiding the convergence issue. The stationary phase method (SPM) is used to calculate the integral of the induced current. Both grouping of MOM regions and interpolation of stationary points are used to accelerate the present approach. Results obtained by this method agree well with that from the traditional Triangle MOM-PO. Comparison of execution times of each method demonstrates that the present method is accurate enough and much more efficient.

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Cited: Baidu(4)
Fast convex optimization method for passivity enforcement of macromodels
GAO Song;LI Yushan;YAN Xu
J4    2012, 39 (1): 62-66+121.   DOI: 10.3969/j.issn.1001-2400.2012.01.012
Abstract1222)      PDF(pc) (1576KB)(975)       Save

In the traditional convex optimization based method, the number of free variables is large, which will lead to demanding computations. Based on this consideration, a fast convex optimization method is proposed in this paper. The initial value of the energy matrix is determined before optimization with only some degrees of freedom. This procedure can reduce 60% of the number of free variables, which can greatly increase the efficiency of the method. Numerical examples show that the simulation time required by the proposed method is less than 1/30 that of the traditional method with high accuracy.

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Cited: Baidu(2)
Study of a new track correlation algorithm in data fusion
QUAN Yining;JIANG Zhen;HUANG Xiaodong;LI Weifeng
J4    2012, 39 (1): 67-74.   DOI: 10.3969/j.issn.1001-2400.2012.01.013
Abstract1483)      PDF(pc) (579KB)(1095)       Save

Because of being highly dependent on the threshold and lacking the consideration of global solutions, the Nearest Neighbors Algorithm(NNA) will make some mistakes when the density of targets is high. To solve this problem, global search strategy, gating and dynamic programming are used to build a new correlation algorithm-the Global Best Track Correlation Algorithm(GBTCA). In two experiments, both of the two algorithms are run and compared to NNA, GBTCA, which shows that the new algorithm has a higher correct correlation rate and is less dependent on threshold values.

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Cited: Baidu(5)
Novel SG-CRLH transmission line and its application to the UWB dual-band bandpass filter
QIANG Li;ZHAO Wei;QIN Hongbo
J4    2012, 39 (1): 75-78.   DOI: 10.3969/j.issn.1001-2400.2012.01.014
Abstract1323)      PDF(pc) (1645KB)(937)       Save

An ultra-wide band (UWB) dual-band bandpass filter is presented using a simplified general composite right/left-handed (SG-CRLH) structure. Each cutoff frequency is controllable by the values of elements. To enhance the spurious passband suppression, periodical complementary split-ring resonators (CSRRs) are introduced to form an extra transmission zero. Finally, an UWB dual-band bandpass filter (2.2~4.0GHz, 4.8~9.3GHz) is designed, fabricated and tested. The fractional bandwidths of the first and second passbands are 58% and 63.8%, respectively. The good agreement between measurement and simulation is observed.

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Cited: Baidu(2)
Novel hand motion tracking system
MA Yinghong;YANG Jiawei;HUI Leifang;LI Ye;MAO Zhihong;SUN Mingui
J4    2012, 39 (1): 79-85.   DOI: 10.3969/j.issn.1001-2400.2012.01.015
Abstract1557)      PDF(pc) (1644KB)(1186)       Save

Most existing hand tracking systems have restrictions on human motion. This paper presents a wireless, wearable, and unobstructive wrist-finger tracking system, which uses a small magnet affixed on each fingernail as a position marker and a set of small magnetic sensors attached to an electronic wristband as a detector array. As the wrist and the finger move, the combined magnetic field from all magnets is detected by each sensor at a specific wrist location. The detected data are fed into a hand posture estimator to inversely calculate the hand posture based on a mathematical system model. The measurability and trackability of hand movements in the system are validated, respectively, by measurement and hand tracking experiments.

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Cited: Baidu(1)
Higher-order nonlocal variational model
LI Yafeng;FENG Xiangchu
J4    2012, 39 (1): 86-91.   DOI: 10.3969/j.issn.1001-2400.2012.01.016
Abstract1272)      PDF(pc) (8378KB)(956)       Save

To describe the nonlocal structure of images better and remove noise, this paper proposes a higher-order nonlocal variational model by defining a new weighted function. Theoretical analysis and numerical experiments are presented to demonstrate the performance of the proposed model, which is better than the original in terms of both PSNR and visual perception. As a result, the new model keeps the advantages of the nonlocal variational model, while it can preserve image features better.

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Cited: Baidu(7)
Routing algorithm for deep space networks with  a maximum throughput
LI Hongyan;YANG Guangxiang;WANG Wenlong
J4    2012, 39 (1): 92-97.   DOI: 10.3969/j.issn.1001-2400.2012.01.017
Abstract1369)      PDF(pc) (558KB)(1118)       Save

The deep space network has several characteristics not commonly seen in terrestrial wireless networks. Important among them are the long delays and seldom continuous end-to-end paths which make conventional table-driven routing algorithms work inefficiently. To overcome these problems, a routing algorithm focusing on a maximum throughput is proposed. The algorithm constructs multiple end-to-end paths for non-real-time data delivery by utilizing the store-and-forward mechanism. According to intermittent connectivity phases and throughput of links, the available time intervals for data transmission of each link in a path are obtained which aims at maximizing the usage of link connectivity phases. The throughput of each path is calculated based on link available time intervals. The path with a maximum throughput is selected as the end-to-end route. Theoretical analysis and simulation results show that the routing algorithm is capable of supporting end-to-end communication with intermittent links and constructs the route with a maximum throughput.

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Research on the localized routing mechanism for the PMIPv6
TANG Jun;PEI Changxing;SU Bo
J4    2012, 39 (1): 98-104.   DOI: 10.3969/j.issn.1001-2400.2012.01.018
Abstract1083)      PDF(pc) (687KB)(1030)       Save

The Proxy Mobile IPv6 (PMIPv6) is a network based mobility management protocol, but the transmission efficiency is affected by the requirement that all the data packets   traverse the Local Mobility Anchor. In this paper, a novel localized routing scheme is proposed. Based on various topology infrastructures in the actual applied scenario, the appropriate LR-initiator is selected dynamically and the decision rules of LR are made reasonably. In addition, the signaling transmission is optimized in order to reduce the protocol overhead. Theoretical analysis and simulation results indicate that the proposed scheme can obviously shorten the response time of LR compared with a classical protocol called LRP, and overcome the defect that the solution of LR cannot be provided in some special scenario when using LRP.

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Cited: Baidu(3)
Fast super-resolution reconstruction algorithms for multi-frame images with random shifts
NING Beijia;JI Feng;GAO Xinbo
J4    2012, 39 (1): 105-110.   DOI: 10.3969/j.issn.1001-2400.2012.01.019
Abstract1396)      PDF(pc) (3178KB)(945)       Save

The traditional multi-frame super-resolution (SR) reconstruction methods are computationally expensive and only applicable to offline processing cases. To reduce the workload of SR fusion for real-time applications, three algorithms, i.e., neighborhood combination interpolation (NCI), neighborhood expansion interpolation (NEI) and global two-direction linear interpolation (GTDLI), are proposed in this paper under the condition of multiple sparsely-sampled lower resolution images with global random shifts. Simulation results illustrate the effectiveness of these proposed algorithms and the advantages in speed over classic SR algorithms. Finally, the applicable fields for the three algorithms are concluded through theoretical analysis and experimental comparison.

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Cited: Baidu(2)
Definition and construction of K-time programs
MA Guojun;PEI Qingqi;CHEN Yuan;JIANG Xiaohong
J4    2012, 39 (1): 111-114+127.   DOI: 10.3969/j.issn.1001-2400.2012.01.020
Abstract1229)      PDF(pc) (383KB)(901)       Save

Based on the study of one-time programs, we describe the characters of K-time programs by a formal definition and study the condition and method for the construction of the K-time program based on the definition to make up the lack of the theoretical study of the characters and construction of K-time programs. We provide a theoretical basis for the K-time program construction by presenting a necessary condition for the K-time program construction with a definition of the programs that can not be converted into K-time programs and a definition of the programs that can be converted into K-time programs along with a one time program based construction of this kind of programs and proof.

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Performance analysis and optimization of censoring  based cooperative spectrum sensing
LI Meiling;YUAN Chaowei;TIAN Xinji;LI Lin
J4    2012, 39 (1): 115-121.   DOI: 10.3969/j.issn.1001-2400.2012.01.021
Abstract1216)      PDF(pc) (593KB)(900)       Save

In cognitive radio networks, the control channel bandwidth is limited while implementing the cooperative spectrum sensing. Besides, the severe tail sensing problem exists due to the imperfect reporting channels. A censoring based cooperative spectrum sensing scheme is analyzed in this paper, which reduces the control bandwidth by decreasing the average number of sensing bits reported to the fusion center and also the dependence of the detection performance on the cognitive user number. The sensing performance of the proposed scheme is analyzed under both imperfect sensing channels and reporting channels, which indicates that the tail sensing problem could be effectively solved and that the false alarm probability could also be decreased. An optimal cooperative spectrum sensing algorithm is further proposed for maximizing the spectrum access chance of the secondary user by looking for the optimal party of the number of cognitive users and the detection threshold under a certain protective level to the primary user. Simulation results validate the theoretical analysis.

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Bandwidth allocation based on multi-bid auction in  HFC access networks
HAN Rui;ZENG Xuewen;SUN Peng
J4    2012, 39 (1): 122-127.   DOI: 10.3969/j.issn.1001-2400.2012.01.022
Abstract1100)      PDF(pc) (607KB)(942)       Save

In order to solve the problem of bandwidth allocation on a single channel and load balancing in a channel group in HFC access networks, we propose a bandwidth allocation scheme based on multi-bid auction. Service agents submit their bids to the edge resource manager who runs the auction. The bandwidth is allocated by the improved multi-bid auction scheme. Multimedia services' QoS is guaranteed by admission control and bandwidth reservation. Load balancing can be achieved by service agents' user assignment scheme. Theoretical analysis and experimental results demonstrate that the proposed approach allocates bandwidth efficiently with little communication overhead and low time complexity. It also balances the load in a channel group.

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Quantized optimal throughput analysis model of  wireless multi-hop Ad hoc networks
SU Jingfang;WU Muqing;ZHANG Qinjuan
J4    2012, 39 (1): 128-134.   DOI: 10.3969/j.issn.1001-2400.2012.01.023
Abstract1336)      PDF(pc) (557KB)(987)       Save

Knowing the systematic throughput of a wireless network is an important thing before it can be efficiently used. Researches on the maximum throughput of a wireless network are mainly based on the fundamental network architecture in which nodes usually access the access point via one hop. The optimum throughput of the multi-hop Ad hoc network is related to network topology, node density, carrier sense range, hidden node effect and capture function and so on; so, the accurate estimation of it is a complicated job. An integrated analytical model which takes all the above factors into consideration is presented here. The modeling process involves the collision probability caused by both the hidden nodes and the nodes within the carrier sensing range; besides, it considers the capture function’s existence, which makes the analytical model more accurate. Through numerical analysis and network simulation, the newly deduced analytical model is proved to be able to match the practical results very well.

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Carrier frequency offset estimation algorithm in MC-CDMA systems with Walsh-code spreading
LIU Licheng;HU Rui
J4    2012, 39 (1): 135-140.   DOI: 10.3969/j.issn.1001-2400.2012.01.024
Abstract1199)      PDF(pc) (517KB)(944)       Save

Aiming at the multiple carrier frequency offset (CFO) problem in the uplink of MC-CDMA systems, a pilot algorithm based on Walsh-code spreading is proposed. The all “1” Walsh-code as the specific spreading code is used to spread two identical pilots of the interested user. At the receiver, by exploiting the different mean value properties between the specific pilot symbols spreading code and data symbols spreading codes, the received interested user's pilot signal components can be approximately extracted and accordingly the CFO of the interested user can be obtained with the phase-angle extraction method. Simulation results show that compared with the subspace decompose based ATS algorithm, the proposed estimator has similar CFO estimation performance with lower computation complexity under the frequency fading channel, and is especially suitable for the scenario where CFO needs tracking during the process of data transmission.

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Cited: Baidu(2)
Buffer schedule algorithm combined with epidemic routing
TANG Lijun;LI Yun;CHAI Yi;WANG Xiang
J4    2012, 39 (1): 141-145.   DOI: 10.3969/j.issn.1001-2400.2012.01.025
Abstract1384)      PDF(pc) (555KB)(1004)       Save

The Delay-Tolerant network(DTN) is a wireless network, in which links between nodes may be disconnected frequently. In DTNs, packets are mainly delivered in a “store-carry-forward” manner, which is different from the “store-and-forward” method used in conventional networks. However, due to the short contact duration between nodes in network and the limited buffer size of the nodes,the packets in the forwarding path may be easily lost without considering an effective buffer schedule policy. For the above characteristics of the network itself, in this paper we propose a buffer schedule algorithm to forward data in the nodal buffer in order of the average contact frequency between the current node's neighbor nodes and the corresponding packet's destination node combined with the epidemic routing protocol. And the performance of the proposed algorithm is evaluated on the NS-2 simulation platform. Final simulation results show that its performance metrics, including the increase in data delivery rate, decrease in end-to-end delay and reduction of network overhead, are improved significantly with limited network resources.

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Cited: Baidu(4)
Effective method for RCS computation of large and deep cavities
ZHANG Hongxia;ZOU Yanlin;SU Donglin
J4    2012, 39 (1): 146-150.   DOI: 10.3969/j.issn.1001-2400.2012.01.026
Abstract1123)      PDF(pc) (571KB)(983)       Save

To reduce the too high requirements when the RCS of electrically large and deep cavity is computed, an effective method based on the Finite Element-Boundary Integration (FE-BI) technique is presented. By utilizing the unique features of the matrix elements and excited vectors when the FE-BI technique is utilized to compute the cavity scattering, and introducing the idea of generalized Gaussian elimination, we can divide the deep cavity into some layers along its depth and perform the calculation layer by layer. The required maximum memory is dependent only on the cavity cross section size and independent of its depth. By fully exploiting the characteristics of the presented method, the delivering scheme between adjoined layers and matrix operations can be optimized, and then the computational efficiency is improved significantly. Numerical results show that the presented method can realize the RCS computation of deep cavities fast and accurately.

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Cited: Baidu(5)
Improved super-exponential iteration blind equalization algorithm for carrier phase recovery in underwater acoustic channels
NING Xiaoling;LIU Zhong;LUO Yasong;GONG Li;FU Xuezhi
J4    2012, 39 (1): 151-156.   DOI: 10.3969/j.issn.1001-2400.2012.01.027
Abstract1656)      PDF(pc) (3254KB)(1016)       Save

An improved super-exponential iteration decision feedback blind equalization algorithm with the second order digital phase-locked loop (NMSEI-DFE-2DPLL) is proposed in order to overcome the problem of the ill convergence performance of the super-exponential iteration decision feedback algorithm in the underwater acoustic communication system. Based on the analysis of the modified super-exponential iteration error function, a new fast convergence error function is presented which increases carrier recovery ability; a second order digital phase-locked loop is introduced in decision feedback equalization to track and compensate phase rotation, carrying out the transmitted sequence recovery. Computer simulations of the new algorithm about convergence and carrier recovery ability are carried out respectively under two underwater acoustic channels, using two modulation signals. Simulation results demonstrate that the mean square error and convergence rate of the proposed algorithm have been improved to a large extent compared with the SEI-DFE algorithm in mixed phase channel environment, and the phase rotation has been compensated and carrier recovery ability has been improved greatly in channel environment with phase rotation.

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Cited: Baidu(19)
Data compression of wireless sensor networks in  the heritage monitor
WANG Ju;FANG Dingyi;CHEN Xiaojiang;XING Tianzhang;ZHANG Yuan;GAO Baojian
J4    2012, 39 (1): 157-162.   DOI: 10.3969/j.issn.1001-2400.2012.01.028
Abstract1642)      PDF(pc) (575KB)(1099)       Save

The heritage monitoring data structure with features of monotony, large redundancy and high tolerance. These features make data compression of the wireless sensor network (WSN) in the existing algorithms a high computational complexity and great computational energy consumption. In this paper the improved Swing Door Trending (SDT) algorithm is applied to the compression of WSN for heritage monitoring. In the case of a large-scale heritage monitor, we analyse the relationship between data compression and network energy consumption. Experiments show that the improved SDT's calculational energy consumption is less then 73% compared with the DWC. And when the compression ratio is less than 25%, the improved compression algorithm SDT can be comparable with the DWC. Under the long-term, large-scale heritage monitor the improved SDT algorithm Data compression is more suitable for WSN.

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Recognition and localization of car whistles using the microphone array
LIU Jianping;ZHANG Yiwen;LIU Ying
J4    2012, 39 (1): 163-167.   DOI: 10.3969/j.issn.1001-2400.2012.01.029
Abstract1369)      PDF(pc) (609KB)(955)       Save

Sound data collected by the microphone array is processed to realize the recognition and localization of car whistles in real time. Firstly,an algorithm based on the product of energy and frequency is adopted to detect whistles from noise. And the characteristics of the whistle signal are used to decide whether the received signal is car whistles or not. Secondly, a table-searching method can be designed to recognize the meanings of several kinds of whistles, and then enables intelligent cars to exchange some simple information in the whistle language. Finally, the deference of time delay along with the structure of the microphone array can estimate the angle of the whistles. Computer simulations show that the whistles can be recognized with high accuracy of 90%, and the error of the angle estimate is less than 3°.

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Cited: Baidu(5)
Novel low energy consumption MAC protocol for the wireless sensor networks
LI Yanxiao;ZHANG Yueling;GUAN Hua;LIU Dongyang
J4    2012, 39 (1): 168-171.   DOI: 10.3969/j.issn.1001-2400.2012.01.030
Abstract1573)      PDF(pc) (584KB)(1004)       Save

Because of the limited power supply of nodes, wireless sensor network energy efficiency research is gaining more and more attention. The energy consumption of the MAC layer is analyzed. Based on the S-MAC protocol and PD-MAC protocol a novel algorithm AP is proposed. In simulations, the proposed protocol is evaluated in comparison with S-MAC and PD-MAC in the aspects of energy efficiency and accuracy of packets sink received. The result shows that collision probability can be reduced reasonably; that energy consumption can be reduced in a better way and that the network longevity can be enhanced efficiently.

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Cited: Baidu(5)
Design and analysis of the light-weight mutual  authentication protocol for RFID
LI Huixian
J4    2012, 39 (1): 172-178.   DOI: 10.3969/j.issn.1001-2400.2012.01.031
Abstract1206)      PDF(pc) (506KB)(1133)       Save

In order to solve the weakness in security and privacy and the poor performance of the existing RFID authentication protocols, a Hash-based mutual authentication protocol for RFID is proposed and its security is proved by using the provable security model, with the privacy and security features of the proposed protocol analyzed. Compared with several RFID authentication protocols with the similar structure, the proposed protocol can effectively solve the privacy and security issues of the RFID system and has significant performance advantages, because it greatly reduces the amount of storage and computation of tags, and particularly improves the search efficiency of the server database.

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Trust model of software behaviors based on  check point risk assessment
LIU Yuling;DU Ruizhong;FENG Jianlei;TIAN Junfeng
J4    2012, 39 (1): 179-184+190.   DOI: 10.3969/j.issn.1001-2400.2012.01.032
Abstract1708)      PDF(pc) (496KB)(1048)       Save

In the credible research on current software, risk factors are often ignored. For improving the accuracy and reasonableness of the credible research, by insetting a number of checkpoints into the software behavior tracks, we propose a trust model called (CBRA-TM) which is based on checkpoint behavioral risk assessment. This model can determine the credibility of the software behavior by using risk assessment strategies to determine a suspected risk checkpoint, accumulate multiple checkpoints which are suspected and calculate the credibility of software behavior through the reward or punishment mechanism. Simulation results show that the model can identify potential risks and calculate the credibility accurately, which verifies the validity and feasibility of the model.

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Detection and control of the node capture attack in WSN
ZHOU Jie;GUO Yuanbo;HU Lingyan
J4    2012, 39 (1): 185-190.   DOI: 10.3969/j.issn.1001-2400.2012.01.033
Abstract1370)      PDF(pc) (525KB)(1101)       Save

Aiming at the disadvantage of node capture attack that exists in the WSN(Wireless Sensor Network), we presents a node capture detection method using SPRT(Sequential Probability Ratio Test) to detect capture nodes, and regulate the network by control theory tools. The optimal control sequence is accessed by optimal control of discrete system quadratic performance index. Simulation results show that this method can detect the capture nodes, and that the network status becomes asymptotically stable through continuous implementation of network control.

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Cited: Baidu(3)
Method for extracting the tumor gene based on  the support vector machine
QIN Chuandong;LIU Sanyang;ZHANG Shifang
J4    2012, 39 (1): 191-196.   DOI: 10.3969/j.issn.1001-2400.2012.01.034
Abstract1287)      PDF(pc) (506KB)(1119)       Save

According to the characteristics of the colon cancer gene expression profiles with high dimension, small sample and great noise,a method is proposed to measure the tumor gene with the Bhattacharyya distance and remove the genes irrelevant to the classification task. The method extracts the tumor gene for the second time by utilizing the sensitivity of the tumor gene on the model. Simultaneously, a weight is added to the important genes depending on the normalization of the sensitivity and a new sample dataset is built. Finally a support vector machine is used to analyze and test the feature genes on the new sample dataset. Experimental results show that this method improves the accuracy of tumor diagnosis.

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Generation of optical single sideband with carrier signals using the  dual-parallel Mach-Zehnder modulator in the radio over fiber system
LIU Xiangling;HAN Kun;LI Jiandong;YUE Peng
J4    2012, 39 (2): 1-7.   DOI: 10.3969/j.issn.1001-2400.2012.02.001
Abstract1723)      PDF(pc) (1588KB)(1350)       Save

In the radio over fiber(RoF) system, the difference in power between optical carrier and optical sideband is large using the conventional optical single sideband with carrier(OSSB+C) modulation, resulting in lower receiver sensitivity. An improved method to generate OSSB+C signals is thus proposed based on the dual-parallel Mach-Zehnder modulator(MZM). By adjusting the direct current voltage of the MZM, the balanced power between the optical carrier and optical sideband is obtained for any modulation index, i.e., the value of the carrier-to-sideband ratio(CSR) is 0dB which is optimum. Simulation results show that the receiver sensitivity could be improved by as large as 7.8dB for the small modulation indexes, while about 0.7dB to 1.1dB for the medium and large modulation indexes. In addition, the influence of the drift of direct current bias voltage on the CSR and receiver sensitivity is also analyzed by simulation. The results show that if the bias drift is controlled within the range of 5%, the receiver sensitivity degrades a little, and the RoF system based on the proposed technique has the better robustness.

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Application of quantum LDPC codes to quantum key distribution
XIAO Heling;CAI Ning;WANG Xiao
J4    2012, 39 (2): 8-11+23.   DOI: 10.3969/j.issn.1001-2400.2012.02.002
Abstract1412)      PDF(pc) (424KB)(1101)       Save

In this paper, the security of BB84 key distribution protocol is considered. We assume that in the protocol the eavesdropper Eve intercepts/resends photons transmitted between Alice and Bob with probability ε. First, the BB84 key distribution protocol will be made equivalent to a special Wire-tap channel model, where the main channel is a binary symmetric channel with probability of flipping bits 0.25ε and the eavesdropper's channel is a binary erasure channel with probability of erasure 1-ε. Using the coding method and properties of quantum LDPC codes CSS(C1, C2) for secure communication across the Wire-tap channel in the BB84 protocol is an equivalent proof of the security of BB84 protocol. Finally, the tolerable error rate of the BB84 protocol based on quantum LDPC codes can be obtained by calculating the secrecy capacity of this special Wire-tap channel.

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Blind Rake receiver for TH-UWB systems with multi-user interference
KANG Xiaofei;YANG Jiawei;LIU Jian
J4    2012, 39 (2): 12-16+65.   DOI: 10.3969/j.issn.1001-2400.2012.02.003
Abstract1122)      PDF(pc) (571KB)(1033)       Save

A novel blind Rake receiver is proposed in order to suppress both multi-user interference (MUI) and inter symbol interference (ISI) for time-hopping ultra-wideband (TH-UWB) systems. The receiver firstly exploits the properties of the desired user time-hopping sequence to figure out a filter for eliminating partial MUI and ISI, and then uses the PASTd algorithm to estimate the channel and perform maximal ratio combining (MRC) to further improve the signal to interference plus noise ratio (SINR). Simulation results show that the proposed blind Rake receiver achieves a significant performance gain in comparison with the conventional receiver and Rake receiver, and can converge at the steady state rapidly. Furthermore, it requires less priori knowledge and has lower complexity.

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Optimal power allocation of the DF cooperation system over  imperfect Nakagami-m fading channels
ZHANG Nan;GE Jianhua;GONG Fengkui;GAO Ming
J4    2012, 39 (2): 17-23.   DOI: 10.3969/j.issn.1001-2400.2012.02.004
Abstract1237)      PDF(pc) (618KB)(938)       Save

The impacts of power allocation under imperfect channel estimation on the symbol-error-rate (SER) are investigated for a cooperative network with multiple decode-and-forward (DF) relays over Nakagami-m fading. First,the approximate SER and asymptotic SER for M-QAM are provided by using the Theorem of Total Probability and the moment generating function (MGF). Then based on the presented compact asymptotic SER, the optimal power allocation is transformed to a typical convex optimization problem so that the optimal power allocation is reached to minimize the SER under the total power constraints. Simulations show that compared to the uniform allocation scheme, optimal power allocation scheme can significantly improve the performance of the cooperative system at the low to medium SNR, but can not improve the error floor at the high SNR under the imperfect channel estimation.

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Novel low complexity LMMSE channel estimation algorithm
SHI Lei;GUO Baolong;LI Xiaoping;LV Liang
J4    2012, 39 (2): 24-28+50.   DOI: 10.3969/j.issn.1001-2400.2012.02.005
Abstract1191)      PDF(pc) (575KB)(1295)       Save

This paper presents a novel low complexity LMMSE channel estimation algrithom for the OFDM system to reduce computational complexity caused by matrix inverse operation in the MMSE estimator. Correlation bandwidth is used as a criterion to divide the large auto-correlation matrix into a number of sub-matrixs, including the non-overlap and overlap method. The diaglog sub-matrix blocks representing low-frequency important channel information in the channel autocorrelation matrix are preserved while the other sub-matrix blocks are ignored, thus reducing autocorrelation matrix inversion computational complexity. BER and MSE performance of the new algrithom is evaluated in the frequency selective flat fading channel with comparison to the LMMSE, SVD algorithm. Simulation results and complexity anaysis show that low complexity is obtained at the slight cost of performance degradation.

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Cited: Baidu(8)
No-reference video quality assessment over  the IP network based on packet loss
LIU Hechao;CHANG Yilin;YUAN Hui;YANG Jiawei
J4    2012, 39 (2): 29-34.   DOI: 10.3969/j.issn.1001-2400.2012.02.006
Abstract1280)      PDF(pc) (659KB)(1255)       Save

A novel no-reference video quality assessment model is proposed in order to meet the real-time and low cost requirements of video quality assessment over IP networks. The temporal complexity is calculated without decoding, and the effect of different types of frame loss on video quality is considered. In the proposed model, both spatial and temporal error concealment artifacts of the human visual system (HVS) and frame types are taken into account. Video qualities could be assessed without delay by utilizing the proposed model. Experimental results show that the scores obtained by the proposed model highly agree with the subjective assessment scores. Compared with the video quality evaluation model in G.1070, an average performance gain of 6.96% could be achieved by the proposed model in terms of relativity to subjective results.

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