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2015 Vol. 12, No. 9
Published: 13 September 2015

Guest Editorial
COMMUNICATIONS SYSTEM DESIGN
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       Guest Editorial

Social-Aware Cooperation Among Mobile Terminals for Wireless Downlink Transmission

Mao Hongliang, Feng Wei, Ge Ning
China Communications, 2015, 12(9): 1-10
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This paper investigates the social-aware cooperation (SAC) among mobile terminals (MTs), motivated by the fact that modern smart devices have much improved context awareness. Aware of the social ties, the cooperative network contains two layers of property: social and physical. In order to observe how the social awareness benefit the cooperation performance, we first formulate the social ties between MTs into parameters that can describe the cooperative behaviors by taking the mobility feature into account, defined as the conviction-approval-suspicion (CAS) model. Limited by the processing capability, partner selection is of great practical significance. To this end, the social-aware partner selection strategy is analyzed, and a significant superiority is observed compared to social-unaware selection. By analyzing the cooperative throughput, an explicit relationship between the degrees-of-freedom gain and the social-physical property is finally derived. Simulation results validate the theoretical analysis.
       Guest Editorial

Modeling and Mining the Temporal Patterns of Service in Cellular Network

Sun Weijian, Qin Xiaowei, Wei Guo
China Communications, 2015, 12(9): 11-21
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Recent emergence of diverse services have led to explosive traffic growth in cellular data networks. Understanding the service dynamics in large cellular networks is important for network design, trouble shooting, quality of service (QoE) support, and resource allocation. In this paper, we present our study to reveal the distributions and temporal patterns of different services in cellular data network from two different perspectives, namely service request times and service duration. Our study is based on big traffic data, which is parsed to readable records by our Hadoop-based packet parsing platform, captured over a week-long period from a tier-1 mobile operator’s network in China. We propose a Zipf’s ranked model to characterize the distributions of traffic volume, packet, request times and duration of cellular services. Two-stage method (Self-Organizing Map combined with kmeans) is first used to cluster time series of service into four request patterns and three duration patterns. These seven patterns are combined together to better understand the fine-grained temporal patterns of service in cellular network. Results of our distribution models and temporal patterns present cellular network operators with a better understanding of the request and duration characteristics of service, which of great importance in network design, service generation and resource allocation.
       Guest Editorial

Improving Low Bitrate Video Coding via Computation Incorporating A Priori Information

Tao Xiaoming, Dong Linhao, Li Shaoyang, Li Yang, Ge Ning, Lu Jianhua
China Communications, 2015, 12(9): 22-34
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The growing number of mobile users, as well as the diversification in types of services have resulted in increasing demands for wireless network bandwidth in recent years. Although evolving transmission techniques are able to enlarge the network capacity to some degree, they still cannot satisfy the requirements of mobile users. Meanwhile, following Moore’s Law, the data processing capabilities of mobile user terminals are continuously improving. In this paper, we explore possible methods of trading strong computational power at wireless terminals for transmission efficiency of communications. Taking the specific scenario of wireless video conversation, we propose a model-based video coding scheme by learning the structures in multimedia contents. Benefiting from both strong computing capability and pre-learned model priors, only low-dimensional parameters need to be transmitted; and the intact multimedia contents can also be reconstructed at the receivers in real-time. Experiment results indicate that, compared to conventional video codecs, the proposed scheme significantly reduces the data rate with the aid of computational capability at wireless terminals.
       Guest Editorial

Cyclostationary Feature Detection Based Spectrum Sensing Algorithm under Complicated Electromagnetic Environment in Cognitive Radio Networks

Yang Mingchuan, Li Yuan, Liu Xiaofeng, Tang Wenyan
China Communications, 2015, 12(9): 35-44
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This paper focuses on improving the detection performance of spectrum sensing in cognitive radio (CR) networks under complicated electromagnetic environment. Some existing fast spectrum sensing algorithms cannot get specific features of the licensed users’ (LUs’) signal, thus they cannot be applied in this situation without knowing the power of noise. On the other hand some algorithms that yield specific features are too complicated. In this paper, an algorithm based on the cyclostationary feature detection and theory of Hilbert transformation is proposed. Comparing with the conventional cyclostationary feature detection algorithm, this approach is more flexible i.e. it can flexibly change the computational complexity according to current electromagnetic environment by changing its sampling times and the step size of cyclic frequency. Results of simulation indicate that this approach can flexibly detect the feature of received signal and provide satisfactory detection performance compared to existing approaches in low Signal-to-noise Ratio (SNR) situations.
       Guest Editorial

Cooperative Anti-Interference Spectrum Sharing with Secondary User Selection

PENG Hong, ZHU Yufei, LU Weidang, LIU Xin, HUA Jingyu
China Communications, 2015, 12(9): 45-52
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In this paper, we propose a cooperative anti-interference spectrum sharing strategy with secondary user selection where the secondary system can gain spectrum access along with the primary system. Specifically, secondary user STb and STq are selected to transmit the primary and secondary signal through different bandwidth in the second transmission slot which occupies 1-tb fraction of the time. Thus, the primary and secondary systems will not interfere with each other. We study the joint optimization of time and bandwidth allocation such that the transmission rate of the secondary system is maximized, while guaranteeing the primary system to achieve its target rate. Simulation results confirm efficiency of the proposed spectrum sharing strategy, and the significant performance improvement of the cognitive system.
       Guest Editorial

Low Complexity Multiuser Detection with Recursively Successive Zero-Forcing and SIC Based on Nullspace for Multiuser MIMO-OFDM System

Zhang Chengwen, Wang Bin, Li Danli, Tan Xuezhi
China Communications, 2015, 12(9): 53-63
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To improve the spectrum efficiency, this paper considers the multiuser detection with the MU-MIMO technology for multiuser MIMO-OFDM system uplink with the same subcarrier shared by multiple users. A low complexity multiuser detection algorithm with recursively successive zero-forcing and successive interference cancellation (RSZF-SIC) based on nullspace is proposed. The RSZF process based on the block diagonalization (BD) technique eliminates the co-channel interference (CCI) by a recursive method based on the nullspace orthogonal theorem. The SIC process detects the user signals respectively with the reasonable user detection sequence based on the results of the RSZF process. The computational complexity of the proposed algorithm is effectively reduced by reducing the total number of singular value decomposition (SVD) operations and the dimension of the SVD matrix in the recursive procedure. The performance of the proposed algorithm is improved in terms of bit error rate and sum capacity of the system, especially in the high-SNR regime.
       Guest Editorial

Anomalous Cell Detection with Kernel Density-Based Local Outlier Factor

MIAO Dandan, QIN Xiaowei, WANG Weidong
China Communications, 2015, 12(9): 64-75
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Since data services are penetrating into our daily life rapidly, the mobile network becomes more complicated, and the amount of data transmission is more and more increasing. In this case, the traditional statistical methods for anomalous cell detection cannot adapt to the evolution of networks, and data mining becomes the mainstream. In this paper, we propose a novel kernel density-based local outlier factor (KLOF) to assign a degree of being an outlier to each object. Firstly, the notion of KLOF is introduced, which captures exactly the relative degree of isolation. Then, by analyzing its properties, including the tightness of upper and lower bounds, sensitivity of density perturbation, we find that KLOF is much greater than 1 for outliers. Lastly, KLOF is applied on a real-world dataset to detect anomalous cells with abnormal key performance indicators (KPIs) to verify its reliability. The experiment shows that KLOF can find outliers efficiently. It can be a guideline for the operators to perform faster and more efficient trouble shooting.
       Guest Editorial

Guaranteeing Wireless Communication Secrecy via a WFRFT-Based Cooperative System

Fang Xiaojie, Sha Xuejun, Mei Lin
China Communications, 2015, 12(9): 76-82
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In this paper, a weighted fractional Fourier transform (WFRFT) based cooperative overlay system, aiming to guarantee physical layer (PHY) security, is proposed. The paper elaborates how WFRFT and physical layer properties of the wireless medium are collaborated to guarantee the secrecy of wireless transmissions. In the proposed system, WFRFT is first preform on the secret data, such that the transmitted signal is distorted and can only be neutralized by inverse-WFRFT with the same parameter. And then two streams of the transformed sequences that bearing different messages are cooperatively and simultaneously transmitted to two legitimate receivers via a beamforming-liked method, respectively. In general, both the rapid spatial decorrelation property and the inherent security features of WFRFT are leveraged, such that only the eavesdropper’s is degraded, and hence, the wireless communication secrecy is reliably guaranteed. Numerical simulations are conducted to evaluate the performance of the proposed system in terms of the average bit error rate and the secrecy capacity.
       Guest Editorial

A Learning-Based Channel Model for Synergetic Transmission Technology

Liang Chen, Li Haihan, Li Yunzhou, Zhou Shidong, Wang Jing
China Communications, 2015, 12(9): 83-92
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It is extensively approved that Channel State Information (CSI) plays an important role for synergetic transmission and interference management. However, pilot overhead to obtain CSI with enough precision is a significant issue for wireless communication networks with massive antennas and ultra-dense cell. This paper proposes a learning- based channel model, which can estimate, refine, and manage CSI for a synergetic transmission system. It decomposes the channel impulse response into multiple paths, and uses a learning-based algorithm to estimate paths’ parameters without notable degradation caused by sparse pilots. Both indoor measurement and outdoor measurement are conducted to verify the feasibility of the proposed channel model preliminarily.
       Guest Editorial

A High Spectral Efficiency System Enabled by Free Window with Full Duplex

FENG Cheng, CUI Hongyu, MA Meng, JIAO Bingli
China Communications, 2015, 12(9): 93-99
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This paper studies the capacity issues of a wireless communication system that implements single channel full duplex (SCFD) communication at the base station (BS), thereby the mobile stations share the channel via time division duplex (TDD). The system makes use of the same setup as has been used in previous studies of SCFD, but unlike these previous systems, the new system uses water-filling to maximize the spectral efficiency of the uplink channel. The concept of a free window is introduced to the duplex model for measuring, intuitively, the effective bandwidth of the bi-directional communication. The capacity gain is calculated and numerical results show the advantage of the proposed system over that of conventional TDD.
       Guest Editorial

A Resource Scheduling Scheme for Spectrum Aggregation in Cognitive Radio Based Heterogeneous Networks

Fu Yunhai, Ma Lin, Xu Yubin
China Communications, 2015, 12(9): 100-111
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In spectrum aggregation (SA), two or more component carriers (CCs) of different bandwidths in different bands can be aggregated to support wider transmission bandwidth. The current resource scheduling schemes for spectrum aggregation are not optimal or suitable for CR based heterogeneous networks (HetNets). Consequently, the authors propose a novel resource scheduling scheme for spectrum aggregation in CR based HetNets, termed as cognitive radio based resource scheduling (CR-RS) scheme. CR-RS has a three-level structure. Under a dynamic traffic model, an equivalent throughput of the CCs based on the knowledge of primary users (PUs) is given. On this basis, the CR users data transmission time of each CC is equal in CR-RS. The simulation results show that CR-RS has the better performance than the current resource scheduling schemes in the CR based HetNets. Meanwhile, CR-RS is also effective in other spectrum aggregation systems which are not CR based HetNets.
       Guest Editorial

Energy Efficiency Analysis of Cellular Networks with Cooperative Relays via Stochastic Geometry

Zhang Zhiwei, Li Yunzhou, Huang Kaizhi, Zhou Shidong, Wang Jing
China Communications, 2015, 12(9): 112-121
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Cooperative relaying is a promising technology that can improve the spectral and energy efficiency of cellular networks. However, the deployed relays consume a lot of energy and system resources. To improve the energy efficiency of the relay-assisted cellular networks, this paper considers the use of energy harvesting (EH) on relay nodes. A random sleeping strategy is also introduced in macro base stations (MBS) as a possible method to reduce energy consumption. In this paper, an analytical model is proposed to investigate the energy efficiency of cellular networks with EH relays and sleep mode strategy. Numerical results confirm a significant energy efficiency gain of the proposed networks comparing to the cellular networks with non-EH relays and MBSs without sleep mode strategy. The effects of the density and transmit power of MBSs on energy efficiency are also given through simulations.
       Guest Editorial

Synchronization for the Environment of OFDM Cooperative Communications Based on Preamble Design and Phase Rotation

Wang Xue, Qian Zhihong, Fu Yu
China Communications, 2015, 12(9): 122-132
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Timing and carrier frequency offset estimation are critical issue for OFDM cooperative communications. In view of the complexity and high accuracy requirement, 1/2 and 1/4 pilot symbol cycle CAZAC sequence structures are defined as the pilot frequency sequence. Estimation within one symbol cycle is carried out through averaging samples of two neighboring symbol cycles, after which the operation is expanded to all the symbol cycles in one band group. Taking multipath effect into account, the concept of phase rotation is proposed for a further step. Adjust the phase difference of estimated symbols by phase rotation, and cross estimation could be done. Meanwhile, timing scheme works within one cycle training sequence. Theoretical and simulation analysis indicate that CRLB does not only relate to estimation symbol length, but also be influenced by phase difference of estimation symbols seriously. In the condition that the length of estimation is fixed, the bigger the phase rotation angle is, the smaller the CRLB is. The complexity of proposed algorithm is less than full cycle average estimation method for almost 50%. Meanwhile, the estimation accuracy is approximate with the full cycle average estimation method as well. Timing scheme with the defined preamble structure is also proposed. Simulation proves its efficiency.
       COMMUNICATIONS SYSTEM DESIGN

Energy-Efficient Transceiver Design for Multi-Pair Two-Way Relay Systems

Fei Zesong, Li Na, Xing Chengwen, Gong Shiqi
China Communications, 2015, 12(9): 133-140
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In this paper, we focus on energy-efficient transceiver and relay beamforming design for multi-pair two-way relay system. The multi-antenna users and the multi-antenna relay are considered in this work. Different from the existing works, the proposed algorithm is energy-efficient which is more applicable to the future green network. It considers both the sum-MSE problem and the power consumption problem for the users under the relay power constraint. Based on the optimal condition decomposition (OCD) method, the energy-efficient precoders at the users can be designed separately with limited information exchanged. The proposed relay beamforming algorithm is based on the alternative direction method of multipliers (ADMM) which has simpler iterative solution and enjoys good convergence. Simulation results demonstrate the performance of the proposed algorithms in terms of power consumption and MSE performance.
       COMMUNICATIONS SYSTEM DESIGN

Area-Based Connected Dominating Set Construction and Maintenance Algorithm in Ubiquitous Stub Environment

Guo Shaoyong, Xing Ningzhe, Fu Ning, Shao Sujie, You Fucheng
China Communications, 2015, 12(9): 141-149
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In order to construct and maintain stability Connected Dominating Set over MANET in Ubiquitous Stub Network, this paper proposes a novel area-based CDS construction and maintenance algorithm. The algorithm is divided into three phases: 1) Area Partition; 2) Area Expansion; 3) Area Connection. In additional, maintenance strategy is proposed in each phase respectively to handle node mobility with timer. At last, the simulation is implemented with OPNET and MATLAB and the results are analyzed in detailed with Size of CDS, Message Overhead and other indexes.
       COMMUNICATIONS SYSTEM DESIGN

A Game Theoretic Approach for Inter-Network Interference Mitigation in Wireless Body Area Networks

Du Dakun, Hu Fengye, Wang Feng, Wang Zhijun, Du Yu, Wang Lu
China Communications, 2015, 12(9): 150-161
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Wireless Body Area Network (WBAN) is an emerging technology to provide real-time health monitoring and ubiquitous healthcare services. In many applications, multiple wireless body area networks have to coexist in a small area, resulting in serious inter-network interference. This not only reduces network reliability that is especially important in emergency medical applications, but also consumes more power of WBANs. In this paper, an inter-network interference mitigation approach based on a power control algorithm is proposed. Power control is modeled as a non-cooperative game, in which both inter-network interference and energy efficiency of WBANs are considered. The existence and uniqueness of Nash Equilibrium in the game are proved, and an optimal scheme based on best response is proposed to find its Nash Equilibrium. By coordinating the transmission power levels among networks under interference environment, the total system throughput can be increased with minimum power consumed. The effectiveness of the proposed method has been illustrated by simulation results, where the performance of the proposed approach is evaluated in terms of overall utility and power efficiency and convergence speed.
       REVIEW PAPER

Invited Paper: Antenna Selection in Energy Efficient MIMO Systems: A Survey

Zhou Xingyu, Bai Bo, Chen Wei
China Communications, 2015, 12(9): 162-173
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With the explosive growth and need for high-speed wireless communications, more and more energy is consumed to support the required quality of service. Therefore, energy efficient or green communication has become a very hot topic under the ground of limited energy resource and environmentally friendly transmission schemes. MIMO technique is capable of reducing the transmission power thanks to its diversity and multiplexing gain. Moreover, antenna selection (AS) is an alternative to extract many of the benefits in MIMO systems with a reduced cost of complexity and power. Although many works including several survey papers have investigated AS in MIMO systems, the goal of these works is only the capacity maximization or error rate minimization, which fails to guarantee the optimality of the energy efficiency in MIMO systems. In this paper, we overview the state of the art in the AS schemes in energy efficient MIMO systems, the goal of which is to optimize the energy efficiency of the whole system. Specifically, we introduce energy efficient AS in point-to-point MIMO, cooperative MIMO, multiuser MIMO and large-scale MIMO systems, respectively. Several challenging and practical issues in this area are also addressed.
 
 
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