Table of Content

30 March 2015, Volume 33 Issue 2

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Communication Engineering

Joint Decoding Algorithm for IRA Code Combined with Network Coding in Cooperative Communications

DAI Cui-qin, RAN Hai-xia

2015, 33(2):  105-116.  doi:10.3969/j.issn.0255-8297.2015.02.001

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By combining multiple information copies from different source nodes at the destination node in a cooperative relay network, we propose a joint irregular repeat accumulate (IRA) code and network coding modified decoding (JI-NMD) algorithm. We first demodulate the modulation information with soft demodulation information of each link, and extract the information copies from the relay node at the destination. This is done according to the functional relationships between the network coding at relay node and the original information in the direct link. We then update the soft demodulation information
of the two copies from the direct and cooperative links in the IRA decoder, and construct a new decoding decision method. We further obtain a simplified log-likelihood ratio (LLR)method. Finally, we analyze the outage probability and spectral efficiency. Simulationresults show that the JI-NMD algorithm has lower bit error rate for QPSK and 16QAM.

Unsupervised Feature Analysis and Classification of Video Streams

YAO Li-tao, DONG Yu-ning

2015, 33(2):  117-128.  doi:10.3969/j.issn.0255-8297.2015.02.002

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 For recognition of flow statistical features based on machine learning, the key is
to select distinguishable features of different traffic flows. This paper presents several QoSrelated
statistical features that can well discriminate video traffics. To make full use of the
advantages of hierarchical clustering algorithm, this paper uses a flexible feature selection
strategy to mark the network video streaming of different levels. Experiments are performed
on a large scale real network video data. The results show that the proposed method can
achieve significantly higher classification accuracy compared to existing methods.
Keywords: video streaming, statistical features, QoS, traffic classification, hierarchical
clustering

Resource Allocation for Machine-to-Machine Communications with Multiple Access in Cellular Networks

LIN Qi-zhong, ZHANG Dong-mei, XU Kui, XIE Wei

2015, 33(2):  129-141.  doi:10.3969/j.issn.0255-8297.2015.02.003

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 An increasing number of machine-to-machine (M2M) devices are accessing upstream
of the cellular network, while the resource is limited. This paper analyzes the
resource allocation problem when M2M devices multiple access upstream with time division
multiple access (TDMA) or frequency division multiple access (FDMA). An algorithm
is proposed to allow sleep mode to dynamically allocate resource. By dropping a small
fraction of arrivals from the devices farther out near the cell edge, the base station can
increase its maximum load. While allowing dormancy and relating remaining energy with
sleep mode, both the base station centrally dynamically allocating resource and devices’
distributed opportunistic uploading can achieve a network lifetime longevity compared with
no sleep mode.

Intensity and Expansion of Partially Coherent Beam Propagating in Slant and Horizontal Atmospheric Turbulence

KE Xi-zheng, WANG Wan-ting

2015, 33(2):  142-154.  doi:10.3969/j.issn.0255-8297.2015.02.004

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 Based on the generalized Huygens-Fresnel principle, we derive the cross-spectral
density function using the modified von Karmon spectrum and atmospheric refractive-index
structure constant issued by ITU-R. We also derive analytic expressions of intensity distribution
and beam width of partially coherent Gaussian-Schell beam propagating in the
atmosphere along slant and horizontal paths. The impact on the beam propagating in
the two ways due to turbulence intensity, zenith, coherence length of the beam and other
parameters are discussed. They are compared respectively from the perspective of normalized
intensity distribution and relative expansion. The results show that the normalized
intensity distribution of the beam in a free space along a horizontal path is the same as
that along a slant path. The normalized intensity distribution is more concentrated, with
the peak much stronger when zenith is smaller, while the effects of the turbulence become
weaker. Impact on the zenith expansion, turbulence, coherence of the beam is almost consistent
with the slant path.

Accurate and Low Overhead Mechanism for Measuring Available Bandwidth

ZHOU Yi-qiu1, CHEN Bing1, QIAN Hong-yan1, Lü Zong-lei2

2015, 33(2):  155-166.  doi:10.3969/j.issn.0255-8297.2015.02.005

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The available end-to-end bandwidth is an important specification in network
measurement. Most tools need to spend much time in measuring and analyzing before
calculating the available bandwidth. This paper proposes a low overhead mechanism for
accurate and fast measurement of the available bandwidth by analyzing the cross traffic
effect in the Internet. A model is established to reflect the relationship between utilization
and the sending rate of probe packets, which is combined with an extended Kalman filter to
obtain the new available bandwidth. This mechanism does not require any prior knowledge
of the bottleneck link capacity and can reduce the effect of accuracy. Besides, the sending
rate of probing packets can be much lower than the available bandwidth. Performance
of the mechanism is verified numerically, showing fast response to burst cross traffic, low
estimation error, and short convergence time.

Two-Dimensional DOA Estimation for Planar Array via Reduced-Dimension Capon

JIANG Chi|ZHANG Xiao-fei|ZHANG Li-cen

2015, 33(2):  167-177.  doi:10.3969/j.issn.0255-8297.2015.02.006

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This paper discusses estimation of two-dimensional (2D) direction of arrival
(DOA) for a planar array, and derives a reduced-dimension Capon (RD-Capon) algorithm.
The first parameter is obtained by searching the spectrum peak of transformation of the
covariance matrix, obtained from the received signal. The second parameter is estimated
using least squares. The algorithm uses one-dimensional global search to achieve a joint estimation
of 2D DOA. This algorithm based on one-dimension local searches can avoid high
computational cost within 2D-Capon algorithm by spectrum peak search, with the performance
close to the 2D-Capon algorithm. The proposed algorithm can obtain automaticallypaired
2D DOA estimation for planar array. It works well for the sources with the same
azimuth (or elevation). Simulation results verify the usefulness of the algorithm.

Blind Recognition of Self-Synchronized Scrambler Based on Linear Block Code

ZHANG Min1,2, Lü Quan-tong1,2, ZHU Yu-xuan3

2015, 33(2):  178-186.  doi:10.3969/j.issn.0255-8297.2015.02.007

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A blind recognition method of self-synchronous scrambler based on the linear
block code with unbiased information source is proposed. Different run characteristics of
the linear block code and random sequence are analyzed, leading to the conclusion that the
run feature of correctly extracted scrambler sequence differs from that of the wrong one.
A polynomial of the scrambler is determined with maximum value search in all possible
Euclidean distances between the run ratios of extracted and random sequences. Experiments
and simulation results show correctness of the theoretical analysis. Blind recognition
of self-synchronous scrambler after the linear block code with unbiased information source
can be realized, useful in engineering application.

Adaptive Speech Enhancement for Microphone Array

XU Jin1,2, ZHAO Yi-bo1,2, GUO Ye-cai1,2

2015, 33(2):  187-193.  doi:10.3969/j.issn.0255-8297.2015.02.008

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In a complex speech environment, microphone array speech enhancement techniques
can effectively extract target speech signals and eliminate noise. In a conventional
microphone array, the beam forming weighting coefficients are fixed. To flexibly control
the beam forming direction of the microphone array and eliminate residual noise due to
side-lobes, this paper presents an adaptive enhancement technique for microphone array
speech. A microphone array with an adaptive filter is used to form a controllable generalized
sidelobe canceller (GSC), followed by improved spectral subtraction with a Chebyshev
window function. Simulation results show that the proposed method can effectively remove
noise, improving the performance by about 3.5 dB with respect to the ordinary GSC.

ISSR Model of Message Propagation in Microblog Networks

LU Jing1,2,3, YU Xiao-qing1,2, WAN Wang-gen1,2

2015, 33(2):  194-202.  doi:10.3969/j.issn.0255-8297.2015.02.009

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 We divide microblog users into three types: uninformed, forwarder and rejecter,
and propose an uninformed-spreader-spreader-rejecter (ISSR) model based on the
real situation of message propagation in a microblog network and the classical epidemic
model susceptible-infectious-removed (SIR). The transmission mechanism is described in
detail. We also give a steady-state analysis of the mean-field equations of the model. The
network evolution model corresponding to the statistical property of real networks is built
based on the crawled information from Sina microblog users in Shanghai’s typical universities.
Dynamics of the networks is analyzed. Simulation results show a larger retweeting
rate  and a smaller rejecting rate  may improve the spreading range of the microblog
message. Meanwhile, the multiple retweeting rate
 has a certain influence on the density of spreaders.

Computer Science and Applications

AdaBoost Algorithm with Classification Belief

YAN Chao, WU Yue, YUE Xiao-dong

2015, 33(2):  203-214.  doi:10.3969/j.issn.0255-8297.2015.02.010

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Ensemble learning is widely accepted and used in machine learning. This paper
proposes a multi-class ensemble learning algorithm named AdaBoost belief. The algorithm
improves AdaBoost·SAMME by attaching weights to classes in every weak classifier. These
weights, called class beliefs, are computed based on class accuracy collected in each round
of the iteration. We compare the algorithm with AdaBoost·SAMME in many aspects including
learning accuracy, generalization ability, and theory support. Experimental results
indicate that the proposed method has a competitive learning ability and high prediction
accuracy in Gaussian sets, several UCI sets, anda number of log-based intrusion detection
applications. When the class number increases so that prediction of classes becomes
more difficult, the prediction error rate of the proposed algorithm increases slower than
AdaBoost·SAMME.

Design of Alliance Identity Authentication Scheme in Cloud Computing Environment

WANG Chong-xia1, DING Yan2, LIU Qian2, ZHOU Xian-wei2

2015, 33(2):  215-222.  doi:10.3969/j.issn.0255-8297.2015.02.011

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 This paper presents a “contract”-related certification protocol in a cloud computing
alliance environment. With a signature algorithm of combined public and private
data, “contract” trust relationship is built among alliance clouds. By taking advantage of
the trust relationship, distributed management of user identity information and “contract”
related certification are realized in the cloud alliance. The proposed protocol uses bulletin
board, time stamp, signature, and anti-collision hash function to reduce information interaction,
effectively preventing data tampering, replay, and middle attack. Theoretical
analysis shows that the proposed protocol is secure and efficient. It requires less computation
and communication overhead, and provides a concise and security solution for alliance
identity authentication in a cloud environment.