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    Guest Editorial
  • Guest Editorial
    Joint User Association and Resource Allocation for Self-Backhaul Ultra-Dense Networks
    LIU Yanping, FANG Xuming
    2016, 13(2): 1-10.
    Abstract ( )   Knowledge map   Save
    In order to meet the exponentially increasing demand on mobile data traffic, self-backhaul ultra-dense networks (UDNs) combined with millimeter wave (mmWave) communications are expected to provide high spatial multiplexing gain and wide bandwidths for multi-gigabit peak data rates. In self-backhaul UDNs, how to make the radio access rates of small cells match their backhaul rates by user association and how to dynamically allocate bandwidth for the access links and backhaul links to balance two-hop link resources are two key problems on improving the overall throughputs. Based on this, a joint scheme of user association and resource allocation is proposed in self-backhaul ultra-dense networks. Because of the combinatorial and nonconvex features of the original optimization problem, it has been divided into two subproblems. Firstly, to make the radio access rates of small base stations match their backhaul rates and maximize sum access rates per Hz of all small cells, a proportional constraint is introduced, and immune optimization algorithm (IOA) is adopted to optimize the association indicator variables and the boresight angles of between users and base stations. Then, the optimal backhaul and access bandwidths are calculated by differentiating the general expression of overall throughput. Simulation results indicate that the proposed scheme increases the overall throughputs significantly compared to the traditional minimum-distance based association scheme.
  • Guest Editorial
    User Association in Heterogeneous Network with Dual Connectivity and Constrained Backhaul
    WU Zhouyun, XIE Weiliang, YANG Fengyi, BI Qi
    2016, 13(2): 11-20.
    Abstract ( )   Knowledge map   Save
    A novel user association model for heterogeneous network (HetNet) with dual connectivity (DC) and constrained backhaul is proposed in this paper, where not only the best combination of serving macro cell and small cell for each user to associate is selected but also the optimal traffic split between the macro cell and small cell is determined to enhance both radio resource efficiency and backhaul capacity utilization. To solve this optimization problem, an intuitive algorithm based on iteratively solving two sub-problems is proposed. One sub-problem is a binary integer programming problem and a corresponding greedy algorithm is proposed, while the other sub-problem is a simple linear programming problem and can be easily solved. Numerical results show that the proposed model and algorithm can achieve better radio resource efficiency and backhaul capacity utilization compared with user association in HetNet without DC, which validate the capacity enhancement potentials of radio resource coordination in HetNet with DC.
  • Guest Editorial
    Enhanced Power Allocation Scheme in Ultra-Dense Small Cell Network
    GAO Yuehong, CHENG Lei, ZHANG Xin, ZHU Yajun, ZHANG Yunfei
    2016, 13(2): 21-29.
    Abstract ( )   Knowledge map   Save
    A feasible design of ultra-dense Small cell network involves an effective solution to the interference coordination especially in cell edge. In this paper, we propose a channel state and interference aware power allocation scheme (PAG) as an enhanced solution to improve the system performance, especially for the cell-edge users. Cournot model in Non-cooperative game is employed for power adjustment in Small cell clusters to increase cell-edge users’ throughput by considering the power limitation and interference coordination. Additionally, we take iterative Water Filling scheme as a comparison to clarify that the PAG scheme has struck a favorable balance between system efficiency and fairness. Simulation results show that the proposed scheme contributes to the enhancement of edge users’ throughput and cells’ coverage. Moreover, the scheme is observed to show a stronger adaptability in denser Small cell networks.
  • Guest Editorial
    Ultra Dense Network: Challenges, Enabling Technologies and New Trends
    HAO Peng, YAN Xiao, Yu-Ngok Ruyue, YUAN Yifei
    2016, 13(2): 30-40.
    Abstract ( )   Knowledge map   Save
    5G sets an ambitious goal of increasing the capacity per area of current 4G network by 1000 fold. Due to the high splitting gain of dense small cells, ultra dense network (UDN) is widely considered as a key component in achieving this goal. In this paper, we outline the main challenges that come with dense cell deployment, including interference, mobility, power consumption and backhaul. Technologies designed to tackle these challenges in long term evolution system (LTE) and their deficiencies in UDN context are also analyzed. To combat these challenges more efficiently, a series of technologies are introduced along with some of our initial research results. Moreover, the trends of user-centric and peer-to-peer design in UDN are also elaborated.
    • Channel characterization and Modeling
  • Channel characterization and Modeling
    Independent Component Analysis Based Blind Adaptive Interference Reduction and Symbol Recovery for OFDM Systems
    LUO Zhongqiang, ZHU Lidong, LI Chengjie
    2016, 13(2): 41-54.
    Abstract ( )   Knowledge map   Save
    To overcome the inter-carrier interference (ICI) of orthogonal frequency division multiplexing (OFDM) systems subject to unknown carrier frequency offset (CFO) and multipath, this paper develops a blind adaptive interference suppression scheme based on independent component analysis (ICA). Taking into account statistical independence of subcarriers’ signals of OFDM, the signal recovery mechanism is investigated to achieve the goal of blind equalization. The received OFDM signals can be considered as the mixed observation signals. The effect of CFO and multipath corresponds to the mixing matrix in the problem of blind source separation (BSS) framework. In this paper, the ICA-based OFDM system model is built, and the proposed ICA-based detector is exploited to extract source signals from the observation of a received mixture based on the assumption of statistical independence between the sources. The blind separation technique can increase spectral efficiency and provide robustness performance against erroneous parameter estimation problem. Theoretical analysis and simulation results show that compared with the conventional pilot-based scheme, the improved performance of OFDM systems is obtained by the proposed ICA-based detection technique
  • Channel characterization and Modeling
    Cross-Layer Framework for Fine-Grained Channel Access in Next Generation High-Density WiFi Networks
    ZHAO Haitao, ZHANG Shaojie, Emiliano Garcia-Palacios
    2016, 13(2): 55-57.
    Abstract ( )   Knowledge map   Save
    Densely deployed WiFi networks will play a crucial role in providing the capacity for next generation mobile internet. However, due to increasing interference, overlapped channels in WiFi networks and throughput efficiency degradation, densely deployed WiFi networks is not a guarantee to obtain higher throughput. An emergent challenge is how to efficiently utilize scarce spectrum resources, by matching physical layer resources to traffic demand. In this aspect, access control allocation strategies play a pivotal role but remain too coarse-grained. As a solution, this research proposes a flexible framework for fine-grained channel width adaptation and multi-channel access in WiFi networks. This approach, named SFCA (Sub-carrier Fine-grained Channel Access), adopts DOFDM (Discontinuous Orthogonal Frequency Division Multiplexing) at the PHY layer. It allocates the frequency resource with a sub-carrier granularity, which facilitates the channel width adaptation for multi-channel access and thus brings more flexibility and higher frequency efficiency. The MAC layer uses a frequency-time domain backoff scheme, which combines the popular time-domain BEB scheme with a frequency-domain backoff to decrease access collision, resulting in higher access probability for the contending nodes. SFCA is compared with FICA (an established access scheme) showing significant outperformance. Finally we present results for next generation 802.11ac WiFi networks.
    • Commnuications System Design
  • Commnuications System Design
    A QoS-Aware Packet Scheduling Mechanism in Cognitive Radio Networks for Smart Grid Applications
    XU Siya, WEI Lei, LIU Zhu, GUO Shaoyong, QIU Xuesong, MENG Luoming
    2016, 13(2): 68-78.
    Abstract ( )   Knowledge map   Save
    Cognitive radio sensor network is applied to facilitate network monitoring and management, and achieves high spectrum efficiencies in smart grid. However, the conventional traffic scheduling mechanisms are hard to provide guaranteed quality of service for the secondary users. It is because that they ignore the influence of diverse transition requirements in heterogeneous traffic. Therefore, a novel QoS-aware packet scheduling mechanism is proposed to improve transmission quality for secondary users. In this mechanism, a QoS-based prioritization model is established to address data classification firstly. And then, channel quality and the effect of channel switch are integrated into priority-based packet scheduling mechanism. At last, the simulation is implemented with MATLAB and OPNET. The results show that the proposed scheduling mechanism improves the transmission quality of high-priority secondary users and increase the whole system utilization by 10%.
  • Commnuications System Design
    A Probabilistic Rating Prediction and Explanation Inference Model for Recommender Systems
    WANG Hanshi, FU Qiujie, LIU Lizhen, SONG Wei
    2016, 13(2): 79-94.
    Abstract ( )   Knowledge map   Save
    Collaborative Filtering (CF) is a leading approach to build recommender systems which has gained considerable development and popularity. A predominant approach to CF is rating prediction recommender algorithm, aiming to predict a user’s rating for those items which were not rated yet by the user. However, with the increasing number of items and users, thedata is sparse.It is difficult to detectlatent closely relation among the items or users for predicting the user behaviors. In this paper,we enhance the rating prediction approach leading to substantial improvement of prediction accuracy by categorizing according to the genres of movies. Then the probabilities that users are interested in the genres are computed to integrate the prediction of each genre cluster. A novel probabilistic approach based on the sentiment analysis of the user reviews is also proposed to give intuitional explanations of why an item is recommended.To test the novel recommendation approach, a new corpus of user reviews on movies obtained from the Internet Movies Database(IMDB) has been generated. Experimental results show that the proposed framework is effective and achieves a better prediction performance.
    • Network Technology And Application
  • Network Technology And Application
    Maximum Data Collection Rate in Rechargeable Wireless Sensor Networks with Multiple Sinks
    GAO Demin, LIN Haifeng, LIU Yunfei, WU Guoxin
    2016, 13(2): 95-108.
    Abstract ( )   Knowledge map   Save
    In rechargeable wireless sensor networks, a sensor cannot be always beneficial to conserve energy when a network can harvest excessive energy from the environment due to its energy replenished continually and limited energy storage capacity. Therefore, surplus energy of a node can be utilized for strengthening packet delivery efficiency and improving data collection rate. In this work, we propose an algorithm to compute an upper data generation rate that maximizes it as an optimization problem for a network with multiple sinks, which is formulated as a linear programming problem. Subsequently, a dual problem by introducing Lagrange multipliers is constructed, and subgradient algorithms are used to solve it in a distributed manner. The resulting algorithms are guaranteed to converge to an optimal data generation rate, which are illustrated by an example in which an optimum data generation rate is computed for a network of randomly distributed nodes. Through extensive simulation and experiments, we demonstrate our algorithm is efficient to maximize data collection rate in rechargeable wireless sensor networks.
  • Network Technology And Application
    Research on Services Modeling in LTE Networks
    LIU Qi, SHI Yameng, LI Fuchang, FAN Bin
    2016, 13(2): 109-120.
    Abstract ( )   Knowledge map   Save
    Service modeling offers fundamental guidance to the construction and operation of mobile telecommunication networks. As the domestic LTE networks have been deployed massively, the refined LTE services model needs to be established urgently. In this paper, we firstly extract characteristic parameters of services from statistical data in 3G networks, especially in time, space and user dimension. Secondly, the development trends of LTE services are analyzed. And the refined LTE service model is established. Finally, prediction results of LTE service development in China is given, which could provide efficient support for networks’ optimization and evolution.
  • Network Technology And Application
    A Secure-Efficient Data Collection Algorithm Based on Self-Adaptive Sensing Model in Mobile Internet of Vehicles
    LIANG Wei, RUAN Zhiqiang, TANG Mingdong, LI Peng
    2016, 13(2): 121-129.
    Abstract ( )   Knowledge map   Save
    Existing research on data collection using wireless mobile vehicle network emphasizes the reliable delivery of information. However, other performance requirements such as life cycle of nodes, stability and security are not set as primary design objectives. This makes data collection ability of vehicular nodes in real application environment inferior. By considering the features of nodes in wireless IoV, such as large scales of deployment, volatility and low time delay, an efficient data collection algorithm is proposed for mobile vehicle network environment. An adaptive sensing model is designed to establish vehicular data collection protocol. The protocol adopts group management in model communication. The vehicular sensing node in group can adjust network sensing chain according to sensing distance threshold with surrounding nodes. It will dynamically choose a combination of network sensing chains on basis of remaining energy and location characteristics of surrounding nodes. In addition, secure data collection between sensing nodes is undertaken as well. The simulation and experiments show that the vehicular node can realize secure and real-time data collection. Moreover, the proposed algorithm is superior in vehicular network life cycle, power consumption and reliability of data collection by comparing to other algorithms.
  • Network Technology And Application
    A Dynamic Load Balancing Method of Cloud-Center Based on SDN
    WANG Yong, TAO Xiaoling*, HE Qian, KUANG Yuwen
    2016, 13(2): 130-137.
    Abstract ( )   Knowledge map   Save
    In order to achieve dynamic load balancing based on data flow level, in this paper, we apply SDN technology to the cloud data center, and propose a dynamic load balancing method of cloud center based on SDN. The approach of using the SDN technology in the current task scheduling flexibility, accomplish real-time monitoring of the service node flow and load condition by the OpenFlow protocol. When the load of system is imbalanced, the controller can allocate globally network resources. What’s more, by using dynamic correction, the load of the system is not obvious tilt in the long run. The results of simulation show that this approach can realize and ensure that the load will not tilt over a long period of time, and improve the system throughput.
    • Security Schemes And Solutions
  • Security Schemes And Solutions
    MP-WFRFT and Constellation Scrambling Based Physical Layer Security System
    FANG Xiaojie, SHA Xuejun, LI Yue
    2016, 13(2): 138-145.
    Abstract ( )   Knowledge map   Save
    In this paper, a multiple parameters weighted fractional Fourier transform (MP-WFRFT) and constellation scrambling (CS) method based physical layer (PHY) security system is proposed. The proposed scheme is executed by two steps. In the first step, MP-WFRFT, implemented as the constellation beguiling (CB) method, is applied to change the signal’s identity. In the second step the additional pseudo random phase information, regarded as the encryption key, is attached to the original signal to enhance the security. Typically, the pseudo random phase information can be removed effectively by the legitimate receiver. In contrast to the cryptography based encryption algorithms and the conventional PHY secrecy techniques, the main contribution of the proposed scheme is concentrated on the variation in signal’s characteristics. Simulation results show that the proposed scheme can prevent the exchanging signal from eavesdroppers’ classification or inception. Moreover, the proposed scheme can guarantee the BER performance at a tolerate increasing in computational complexity for the legitimate receivers.
  • Security Schemes And Solutions
    Attribute-Based Access Control for Multi-Authority Systems with Constant Size Ciphertext in Cloud Computing
    CHEN Yanli, SONG Lingling, YANG Geng
    2016, 13(2): 146-162.
    Abstract ( )   Knowledge map   Save
    In most existing CP-ABE schemes, there is only one authority in the system and all the public keys and private keys are issued by this authority, which incurs ciphertext size and computation costs in the encryption and decryption operations that depend at least linearly on the number of attributes involved in the access policy. We propose an efficient multi-authority CP-ABE scheme in which the authorities need not interact to generate public information during the system initialization phase. Our scheme has constant ciphertext length and a constant number of pairing computations. Our scheme can be proven CPA-secure in random oracle model under the decision q-BDHE assumption. When user’s attributes revocation occurs, the scheme transfers most re-encryption work to the cloud service provider, reducing the data owner’s computational cost on the premise of security. Finally the analysis and simulation result show that the schemes proposed in this thesis ensure the privacy and secure access of sensitive data stored in the cloud server, and be able to cope with the dynamic changes of users’ access privileges in large-scale systems. Besides, the multi-authority ABE eliminates the key escrow problem, achieves the length of ciphertext optimization and enhances the efficiency of the encryption and decryption operations.
  • Security Schemes And Solutions
    SAFE: a Scalable Filter-Based Packet Filtering Scheme
    LU Ning, HU Wenhao
    2016, 13(2): 163-177.
    Abstract ( )   Knowledge map   Save
    Recently, Denial-of-Service (DoS) attacks have become the mainstream threat to the Internet service availability. The filter-based packet filtering is a key technology to defend against such attacks. Relying on the filtering location, the proposed schemes can be grouped into Victim-end Filtering and Source-end Filtering. The first scheme uses a single filtering router to block the attack flows near the victim, but does not take the factor that the filters are scarce resource into account, which causes the huge loss of legitimate flows; considering each router could contribute a few filters, the other extreme scheme pushes the filtering location back into each attack source so as to obtain ample filters, but this may incur the severe network transmission delay due to the abused filtering routers. Therefore, in this paper, we propose a scalable filter-based packet filtering scheme to balance the number of filtering routers and the available filters. Through emulating DoS scenarios based on the synthetic and real-world Internet topologies and further implementing the various filter-based packet filtering schemes on them, the results show that our scheme just uses fewer filtering routers to cut off all attack flows while minimizing the loss of legitimate flows.
  • Security Schemes And Solutions
    SDSA: A Framework of a Software-Defined Security Architecture
    LIU Yanbing, LU Xingyu, JIAN Yi, XIAO Yunpeng*
    2016, 13(2): 178-188.
    Abstract ( )   Knowledge map   Save
    The fact that the security facilities within a system are closely coupled and the security facilities between systems are unconnected results in an isolated protection structure for systems, and gives rise to a serious challenge to system security integrations and system controls. Also, the need for diversified services and flexible extensions of network security asks for more considerations and contribu¬tions from the perspective of software engineering in the process of designing and constructing security systems. Based on the essence of the virtualization technique and the idea of software-defined networks, we in this paper propose a novel software-defined security architecture for systems. By abstracting the traditional security facilities and techniques, the proposed security architecture provides a new, simple, effective, and programmable framework in which security operations and security controls can be decoupled, and thereby reduces the software module sizes, decreases the intensity of software deve¬lopments, and improves the security extensibility of systems.
    • Ict Management
  • Ict Management
    Decentralized Mobile SNS Architecture and Its Personal Information Management Mechanism
    LIU Zhihan, YUAN Quan, LIU Lu
    2016, 13(2): 189-199.
    Abstract ( )   Knowledge map   Save
    Mobile SNS is one of the most popular topics of mobile Internet. In order to fulfill the user demand for self-maintained independent social network and ensure the privacy of their personal information and resources, the paper proposes system architecture of decentralized mobile SNS.In the temporary scenarios, the system makes use of the existent specification of FOAF (Friend-of-a-Friend) to describe users’ personal information and act as a certificate to be identified by SNS sites. Ticket-based Access Authorization System (TAAS) is provided to grant permission to acquire resources on personal portal. Meanwhile, the mechanism and algorithm are devised for user profile complete deletion when users are going to quit the service for the temporary scenarios.
  • Ict Management
    A New Evaluation Algorithm for the Influence of User in Social Network
    JIANG Wei, GAO Mengdi, WANG Xiaoxi, WU Xianda
    2016, 13(2): 200-210.
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    Online social networks have gradually permeated into every aspect of people’s life.As a research hotspot in social network, user influence is of theoretical and practical significant for information transmission, optimization and integration. A prominent application is a viral marketing campaign which aims to use a small number of targeted influence users to initiate cascades of influence that create a global increase in product adoption. In this paper, we analyze mainly evaluation methods of user influence based on IDM evaluation model, PageRank evaluation model, use behavior model and some other popular influence evaluation models in currently social network. And then, we extract the core idea of these models to build our influence evaluation model from two aspects, relationship and activity. Finally, the proposed approach was validated on real world datasets,and the result of experiments shows that our method is both effective and stable.