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    COVER PAPER
  • COVER PAPER
    License Assisted Access-WiFi Coexistence with TXOP Backoff for LTE in Unlicensed Band
    Salman Saadat, Da Chen, Kai Luo, Mingjie Feng, Tao Jiang*
    2017, 14(3): 1-14.
    Abstract ( )   Knowledge map   Save
    License assisted access (LAA) was proposed as a solution to the challenge of satisfying high throughput requirement in cellular network with limited licensed band. LAA uses long term evolution (LTE) carrier aggregation technique to combine licensed and unlicensed bands, specifically 5 GHz WiFi band, in order to achieve high data rates. However, LAA has several critical concerns for services provision on 5 GHz unlicensed band. In this article, an overview of the techniques concerning the coexistence of LTE and WiFi on the same unlicensed band is presented. We first present several general approaches including power control of LTE evolved Node B (eNB), carrier selection, LTE duty cycling, self clear to send (CTS) and request to send/CTS (RTS/CTS), and listen before talk (LBT). Then, we focus on LBT techniques for LAA-WiFi coexistence and discuss how LBT based coexistence solutions can dynamically respond to the variations in network load and ensure fair coexistence in a distributed manner. Based on the LBT mechanism, we also present a fairness-aware LAA-WiFi coexisting scheme with TXOP (transmitted in a single transmission opportunity) backoff for LAA eNB. Finally, the performances of various LBT solutions for LAA-WiFi coexistence are evaluated using Markov chain analytical model.
    • FEATURE TOPIC: SPACE INTERNET
  • FEATURE TOPIC: SPACE INTERNET
    SPACE INTERNET
    2017, 14(3): 15-16.
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  • FEATURE TOPIC: SPACE INTERNET
    Steady-State Performance Evaluation of Linux TCPs versus TCP Wave over Leaky Satellite Links
    Ahmed Abdelsalam, Cesare Roseti, Francesco Zampognaro
    2017, 14(3): 17-30.
    Abstract ( )   Knowledge map   Save
    Internet access is becoming even more heterogeneous, including different wireless backhauling links, with Ka-band satellites as a possible alternative. Since communication path is unknown a priori, adoption of PEP solutions to optimize TCP performance over satellite is discouraged to allow dynamic network reconfigurations. To opposite, an end-to-end TCP performance evaluation on such a challenging scenario, with possible large latency and transmission losses, is herein considered of paramount importance. Several TCP variants exist to tackle different aspects of communication networks. In Linux, the different TCP congestion control schemes differ from the theoretical formulations and RFC specifications, introducing a varying set of optimizations and options. This aspect makes difficult to identify a standard/reference TCP version for the proposed scenario, while testing with the real protocol stacks is deemed necessary to obtain consistent results. In addition, an innovative end-to-end TCP, namely TCP Wave, is introduced to replace the traditional window-based transmission with a burst-based strategy, representing a valid alternative to Linux TCP. To offer a fair, realistic and comprehensive evaluation, we configured a simulation setup where different Linux TCPs can be run within ns-3 network simulator and compared with TCP Wave.
  • FEATURE TOPIC: SPACE INTERNET
    Non-Orthogonal Multi-Carrier Transmission for Internet via Satellite
    Yang Yang, Lidong Zhu
    2017, 14(3): 31-42.
    Abstract ( )   Knowledge map   Save
    As the important complementary to terrestrial mobile communications, Internet via satellite can extend the coverage of communication and improve the continuity of data services. To build a space-terrestrial integrated communication system is the inevitable trend in the future. Taking into account combination of 5th generation (5G) terrestrial mobile communication system and satellite communication system, it is necessary to evaluate the promising 5G air interface waveform which can be adopted by satellite. In this paper, several non-orthogonal multi-carrier transmission schemes are evaluated and generalized frequency division multiplexing (GFDM) is advised as potential scheme of space-terrestrial integrated communication system. After the overview of GFDM, the implementation of GFDM transceiver is discussed respectively in time-domain and in frequency-domain. By deriving and comparing implementation complexity, GFDM modulation in time-domain is more suitable for satellite communication system. Then the properties of demodulation algorithms are specified. Based on designed pilot subcarriers, a new improved receiving algorithm is proposed in the end of the paper. The improved algorithm solves the problem of inter subcarriers interference (ICI) in matched filtering (MF) receiver and improves the receiving symbol error rate (SER) obviously. The simulation and analysis prove that the proposed algorithm is effective.
  • FEATURE TOPIC: SPACE INTERNET
    Statistical Modeling of the High Altitude Platform Dual-Polarized MIMO Propagation Channel
    Mingchuan Yang, Shuo Zhang, Xinye Shao, Qing Guo, Wenyan Tang
    2017, 14(3): 43-54.
    Abstract ( )   Knowledge map   Save
    In order to investigate the benefit of multiple-input multiple-output (MIMO) technique applying to the high altitude platform (HAP), a 2×2 MIMO statistical model, which can accurately describe the channel between HAP and high-speed train, is presented. And dual polarization diversity is particularly considered. Based on first-order three-state Markov chain, the single-input single-output (SISO) channel, a subset of the MIMO channel is first established. The ray tracing approach applied to the digital relief model (DRM) which covers the railway between Xi’an and Zhengzhou is usedto obtain the state probability vector and matrix of the state transition probability. The proposed model considers both Doppler shift and temporal correlation, and the polarization correlation and spatial correlation statistical properties of large-scale fading and small-scale fading are analyzed. Moreover, useful numerical results on the MIMO HAP channel outage capacity are provided based on which, significant capacity gains with respect to the conventional SISO case are illustrated. Such statistical channel model can be applied to the future wireless communication system between HAP and high-speed train.
  • FEATURE TOPIC: SPACE INTERNET
    A Power Reduction Method for Pilot Channel of LEO Satellite Based on Dynamic Compensation
    Yong Zhang, Yongning Zhuo, Jian Wang, Siyuan Jiang
    2017, 14(3): 55-65.
    Abstract ( )   Knowledge map   Save
    Since the lower power requirement of code division multiple access (CDMA) than that of other multiple access, the CDMA technology is suitable to be used in low earth orbit (LEO) satellite communication system whose space power is limited due to the small size of satellite. The pilot channel of CDMA technology is very important for earth mobile station (EMS) in LEO system to recover carrier and code, but the power requirement of pilot channel is very higher than that of other channels. In this paper, a power reduction method for pilot channel is proposed. By the new method, the power of pilot channel transmitted from LEO satellite is reduced to a lower level. For improving the signal to noise ratio (SNR) of pilot channel with lower power, coherent integration is employed in EMS at the pre-processing stage. Considering the high dynamic situation of LEO satellite, the long period of time for integration will deteriorate the receiving performance of EMS, therefore, a dynamic compensation module is added to carrier tracking loop against the high dynamic. Meanwhile, the transfer function of the new tracking loop and the condition for steady-state zero error are deduced. Numerical examples are provided to demonstrate effectiveness of the proposed approach.
    • COMMUNICATION THEORIES & SYSTEMS
  • COMMUNICATION THEORIES & SYSTEMS
    Energy Efficiency Optimization for D2D Communications Based on SCA and GP Method
    Xiaozheng Gao, Hangcheng Han, Kai Yang, Jianping An
    2017, 14(3): 66-74.
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    In this paper, we propose an energy-efficient power control scheme for device-to-device (D2D) communications underlaying cellular networks, where multiple D2D pairs reuse the same resource blocks allocated to one cellular user. Taking the maximum allowed transmit power and the minimum data rate requirement into consideration, we formulate the energy efficiency maximization problem as a non-concave fractional programming (FP) problem and then develop a two-loop iterative algorithm to solve it. In the outer loop, we adopt Dinkelbach method to equivalently transform the FP problem into a series of parametric subtractive-form problems, and in the inner loop we solve the parametric subtractive problems based on successive convex approximation and geometric programming method to obtain the solutions satisfying the Karush-Kuhn-Tucker conditions. Simulation results demonstrate the validity and efficiency of the proposed scheme, and illustrate the impact of different parameters on system performance.
  • COMMUNICATION THEORIES & SYSTEMS
    High Performance Compressed Sampling for OFDM-UWB Systems
    Lijun Ge, Hua Zhang, Hui Guo, Hong Wu
    2017, 14(3): 75-86.
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    In order to solve the problem of high-speed sampling in OFDM based ultra wide band (UWB) systems, this paper first gives analysis on the applicability of existing compressed sampling methods. Then, on the basis of an established segmented observation model, it presents an optimized parallel segmented compressed sampling (OPSCS) scheme based on Hadamard matrix. The orthogonal Hadamard matrix is adopted to construct the segmented measurement matrix with any dimensions, thus orthogonal or quasi-orthogonal multiplex observation sequences are obtained, and the restricted isometry property is improved. The optimized orthogonal matching pursuit algorithm is also used for the known sparsity avoiding iterative operation. Researches show that the proposed method can effectively reduce the sampling rate in OFDM-UWB systems, and also has a good ability of noise resisting that it achieves a high system performance better than the existing schemes of compressed sampling and even Nyquist rate sampling.
  • COMMUNICATION THEORIES & SYSTEMS
    Spectrum Allocation for Cognitive Radio Networks with Non-Deterministic Bandwidth of Spectrum Hole
    Jie Huang, Xiaoping Zeng, Xiaoheng Tan, Xin Jian*, Yuan He
    2017, 14(3): 87-96.
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    The spectrum allocation for cognitive radio networks (CRNs) has received considerable studies under the assumption that the bandwidth of spectrum holes is static. However, in practice, the bandwidth of spectrum holes is time-varied due to primary user/secondary user (PU/SU) activity and mobility, which result in non-determinacy. This paper studies the spectrum allocation for CRNs with non-deterministic bandwidth of spectrum holes. We present a novel probability density function (PDF) through order statistics as well as its simplified form to describe the statistical properties of spectrum holes, with which a statistical spectrum allocation model based on stochastic multiple knapsack problem (MKP) is formulated for spectrum allocation with non-deterministic bandwidth of spectrum holes. To reduce the computational complexity, we transform this stochastic programming problem into a constant MKP through exploiting the properties of cumulative distribution function (CDF), which can be solved via MTHG algorithm by using auxiliary variables. Simulation results illustrate that the proposed statistical spectrum allocation algorithm can achieve better performance compared with the existing algorithms when the bandwidth of spectrum holes is time-varied.
  • COMMUNICATION THEORIES & SYSTEMS
    Transmission Capacity Analysis for Linear VANET under Physical Model
    Xinxin He, Hang Zhang, Weisen Shi, Tao Luo, Norman C. Beaulieu
    2017, 14(3): 97-107.
    Abstract ( )   Knowledge map   Save
    In this study, the transmission capacity of VANETs in a highway scenario is analysed on the basis of a 1D line model and the carrier sense multiple access with collision avoidance (CSMA/CA) protocol. We describe the CSMA/CA protocol used in IEEE802.11p from the perspective of the geometric relationship amongst simultaneous transmitters. The desired channel and interfering channels are assumed to experience the same amount of path-loss and Rayleigh fading. On the basis of the proposed model, we analyse the attempted transmission probability of each road segment and the maximum intensity of active transmitters, including their theoretical values. Then, we employ the physical model to obtain the outage probability and derive the upper bound of the transmission capacity of a VANET, which is defined as the average spatial density of successful transmissions in the network. Simulation results indicate that the theoretical value offers a good bound on network capacity.
  • COMMUNICATION THEORIES & SYSTEMS
    The Novel Spectrum Allocation Algorithm in Cognitive Radio System
    Xiangqian Che, Yupeng Xie, Ye Tian, Qijing Zhang, Guizhi Sun
    2017, 14(3): 108-117.
    Abstract ( )   Knowledge map   Save
    In order to reduce the disturbance on an authorizing user and lower the competition between cognitive users, assure the normal communication of a cognitive radio system, reliability theory is applied to describe if a channel can be used by a cognitive user or not and the probability that the channel is continually used for a period. Three aspects including space, time domain and frequency domain are united for the research on the distribution of frequency spectrum. The simulation result shows that, in the space domain, time domain, frequency domain algorithm, the transmitted data volume and the total throughput of the system are superior to those in greedy algorithm and time domain—frequency domain algorithm, the novel algorithm is helpful to reduce the disturbance caused by a cognitive user to an authorizing user and lower the competition between cognitive users, this simulation result shows that the proposed algorithm is effective.
  • COMMUNICATION THEORIES & SYSTEMS
    Multi-Gradient Routing Protocol for Wireless Sensor Networks
    Ying Qiu, Shining Li, Zhigang Li, Yu Zhang, Zhe Yang
    2017, 14(3): 118-129.
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    Sensor networks tend to support different traffic patterns since more and more emerging applications have diverse needs. We present MGRP, a Multi-Gradient Routing Protocol for wireless sensor networks, which is fully distributed and efficiently supports end-to-end, one-to-many and many-to-one traffic patterns by effectively construct and maintain a gradient vector for each node. We further combine neighbor link estimation with routing information to reduce packet exchange on network dynamics and node failures. We have implemented MGRP on TinyOS and evaluated its performance on real-world testbeds. The result shows MGRP achieves lower end-to-end packet delay in different traffic patterns compared to the state of the art routing protocols while still remains high packet delivery ratio.
    • NETWORKS & SECURITY
  • NETWORKS & SECURITY
    Smart Service System(SSS): A Novel Architecture Enabling Coordination of Heterogeneous Networking Technologies and Devices for Internet of Things
    Yongan Guo, Hongbo Zhu, Longxiang Yang
    2017, 14(3): 130-144.
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    In Internet of Things (IoT), the devices or terminals are connected with each other, which can be very diverse over the wireless networks. Unfortunately, the current devices are not designed to communicate with the collocated devices which employ different communication technologies. Consequently, the communication between these devices will be realized only by using the gateway nodes. This will cause the inefficient use of wireless resources. Therefore, in this paper, a smart service system(SSS) architecture is proposed, which consists of smart service terminal (SST), and smart service network (SSN), to realize the IoT in a general environment with diverse communication networks, devices, and services. The proposed architecture has the following advantages: i) the devices in this architecture cover multiple types of terminals and sensor-actuator devices; ii) the communications network therein is a converged network, and will coordinate multiple kinds of existing and emerging networks. This converged network offers ubiquitous access for various sensors and terminals; iii) the architecture has services and applications covering all smart service areas. It also provides the adaptability to new services and applications. A SSS architecture-based smart campus system was developed and deployed. Evaluation experiments of the proposed smart campus system demonstrate the SSS’s advantages over the existing counterparts, and verify the effectiveness of the proposed architecture.
  • NETWORKS & SECURITY
    Efficient XML Query and Update Processing Using A Novel Prime-Based Middle Fraction Labeling Scheme
    Zunyue Qin, Yong Tang, Feiyi Tang, Jing Xiao, Changqin Huang, Hongzhi Xu
    2017, 14(3): 145-157.
    Abstract ( )   Knowledge map   Save
    XML data can be represented by a tree or graph and the query processing for XML data requires the structural information among nodes. Designing an efficient labeling scheme for the nodes of Order-Sensitive XML trees is one of the important methods to obtain the excellent management of XML data. Previous labeling schemes such as region and prefix often sacrifice updating performance and suffer increasing labeling space when inserting new nodes. To overcome these limitations, in this paper we propose a new labeling idea of separating structure from order. According to the proposed idea, a novel Prime-based Middle Fraction Labeling Scheme (PMFLS) is designed accordingly, in which a series of algorithms are proposed to obtain the structural relationships among nodes and to support updates. PMFLS combines the advantages of both prefix and region schemes in which the structural information and sequential information are separately expressed. PMFLS also supports Order-Sensitive updates without relabeling or recalculation, and its labeling space is stable. Experiments and analysis on several benchmarks are conducted and the results show that PMFLS is efficient in handling updates and also significantly improves the performance of the query processing with good scalability.
  • NETWORKS & SECURITY
    Degree-Based Probabilistic Caching in Content-Centric Networking
    Meng Zhang, Jianqiang Tang, Ying Rao, Hongbin Luo, Hongke Zhang
    2017, 14(3): 158-168.
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    Content-Centric Networking is a novel future network architecture that attracts increasing research interests in recent years. In-network caching has been regarded as a prominent feature of Content-Centric Networking since it is able to reduce the network traffic, alleviate the server bottleneck and decrease the user access latency. However, the CCN default caching scheme results in a high caching redundancy, causing an urgent need for an efficient caching scheme. To address this issue, we propose a novel implicit cooperative caching scheme to efficiently reduce the caching redundancy and improve the cache resources utilization. The simulation results show that our design achieves a higher hit ratio and a shorter cache hit distance in comparison with the other typical caching schemes.
  • NETWORKS & SECURITY
    Adaptive Application Offloading Decision and Transmission Scheduling for Mobile Cloud Computing
    Junyi Wang, Jie Peng, Yanheng Wei, Didi Liu, Jielin Fu
    2017, 14(3): 169-181.
    Abstract ( )   Knowledge map   Save
    Offloading application to cloud can augment mobile devices’ computation capabilities for the emerging resource-hungry mobile application, however it can also consume both much time and energy for mobile device offloading application remotely to cloud. In this paper, we develop a newly adaptive application offloading decision-transmission scheduling scheme which can solve above problem efficiently. Specifically, we first propose an adaptive application offloading model which allows multiple target clouds coexisting. Second, based on Lyapunov optimization theory, a low complexity adaptive offloading decision-transmission scheduling scheme has been proposed. And the performance analysis is also given. Finally, simulation results show that,compared with that all applications are executed locally, mobile device can save 68.557% average execution time and 67.095% average energy consumption under situations.
    • SIGNAL PROCESSING FOR COMMUNICATIONS
  • SIGNAL PROCESSING FOR COMMUNICATIONS
    Signal Path Reckoning Localization Method in Multipath Environment
    Junhui Zhao, Lei Li, Hao Zhang, Yi Gong
    2017, 14(3): 182-189.
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    In the wireless localization application, multipath propagation seriously affects the localization accuracy. This paper presents two algorithms to solve the multipath problem. Firstly, we improve the Line of Possible Mobile Device (LPMD) algorithm by optimizing the utilization of the direct paths for single-bound scattering scenario. Secondly, the signal path reckoning method with the assistance of geographic information system is proposed to solve the problem of localization with multi-bound scattering paths. With the building model’s idealization, the proposed method refers to the idea of ray tracing and dead reckoning. According to the rule of wireless signal reflection, the signal propagation path is reckoned using the measurements of emission angle and propagation distance, and then the estimated location can be obtained. Simulation shows that the proposed method obtains better results than the existing geometric localization methods in multipath environment when the angle error is controlled.
  • SIGNAL PROCESSING FOR COMMUNICATIONS
    Direction of Arrivals Estimation for Correlated Broadband Radio Signals by MVDR Algorithm Using Wavelet
    Ying Liu, Chi Xie, Yourun Zhang
    2017, 14(3): 190-197.
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    A theoretical relationship between the wavelet transform and the fast fourier transformation (FFT) methods in broadband wireless signal is proposed for solving the direction of arrivals (DOAs) estimation problem. This leads naturally to the derivation of minimum variance distortionless response (MVDR) algorithm, which combines the benefits of subspace methods with those of wavelet, and spatially smoothed versions are utilized which exhibits good performance against correlated signals. We test the method’s performance by simulating and comparing the performance of proposed algorithm, FFT MVDR and MVDR with correlated signals, and an improved performance is obtained.
  • SIGNAL PROCESSING FOR COMMUNICATIONS
    A Novel Low Density Parity Check Coded Differential Amplitude and Pulse Position Modulation Free-Space Optical System for Turbulent Channel
    Yin Liang, Hua Zhang, Limin Chen, Xiaoping Liu, Xuehong Lin
    2017, 14(3): 198-206.
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    Based on the proposed partly equidifferent mapping and its specific Differential Amplitude and Pulse Position Modulation (DAPPM) demodulation, a modified FSO scheme for turbulent channel is designed and analyzed. The novel Low Density Parity Check (LDPC) coded 4×4 and 4×8 DAPPM Free-Space Optical communication (FSO) system is constructed. The Monte Carlo simulation results show approximately 2dB transmit power reduction against classical LDPC-DAPPM at the identical Bit-Error-Rate in strong turbulent channel. The proposed partly equidifferent mapping is compatible with other modulations, so it enables widespread adoption in other coded FSO systems.