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    25 March 2015, Volume 13 Issue 1
    Special Topic
    5G Wireless:Technology, Standard and Practice
    Fa-Long Luo, Alexander S. Korotkov
    2015, 13(1):  1-2. 
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    5G Wireless: Technology, Standard and Practice Fa-Long Luo and Alexander S. Korotkov Guest Editorial G wireless technology is developing at an explosive rate and is one of the biggest areas of research within academia and industry. With 2G, 3G and 4G, the peak service rate is the dominant metric that distinguishes these three generations. 5G will significantly increase the peak service rate but will also dramatically increase energy efficiency, frequency efficiency, spectral efficiency, and efficiency of other resources. It will dramatically increase flexibility, capacity, coverage, compatibility and convergence. In this way, it will satisfy the increasing demands of emerging big-data, cloud, machine-to-machine, and other applications. The successful development and deployment of 5G technologies will be challenging and will require huge effort from industry, academia, standardization organizations, and regulatory authorities.

    This special issue deals with the application, technology, and standardization of 5G and aims to stimulate research and development of 5G by providing a unique forum for scientists, engineers, broadcasters, manufacturers, software developers, and other related professionals. The topics addressed in this special issue include system architecture, protocols, physical layer (downlink and uplink), air interface, cell acquisition, scheduling and rate adaption, access procedures, relaying, and spectrum allocation. The call-for-papers for this special issue attracted a number of excellent submissions. After two-round reviews, six papers were selected for publication. These papers are organized in two groups.

    The first group comprises three overview papers that outline technical aspects of 5G.

    The second group comprises three papers that provide new algorithms and theoretical analyses that can be used in the development of 5G wireless systems. The first paper,“5G: Vision, Scenarios and Enabling Technologies,”presents an excellent vision for 5G wireless communications systems, which are expected to be standardized around 2020. The paper states that service ubiquity is the key requirement of 5G from the end-user’s prospective and is necessary to support a vast mesh of connections for human-to-human, human-to-machine, and machine-to-machine communications in an energy-efficient way. This paper discusses various technologies designed to improve radio link efficiency, expand operating bandwidth, and increase cell density. With these technologies, 5G systems can accommodate a massive volume of traffic, and this is fundamental for service ubiquity and supporting a massive number of connections, as outlined in the 5G vision of this paper. This paper also discusses the transition to intelligent cloud, in particular, cloud coordination of network access, which enables a flatter architecture. The second paper,“Towards 5th Generation Wireless Communication Systems,” discusses the targeted 5G system, including its driver, requirements, and candidate technologies that might help achieve its intended goals. Drawing on recent results obtained by the author’s research team, the author discusses detection of and access to free spectrum over bands of a heterogeneous nature, extreme densification of March 2015 Vol.13 No.1 ZTE COMMUNICATIONS 01 ? Alexander S. Korotkov Alexander S. Korotkov is a professor and head of the Integrated Electronics Department, St. Petersburg Polytechnic University, Russia. Professor Korotkov is a dedicated university lecturer, offering courses such as Circuits of Wireless Communications. On several occasions, he has been ranked one of the best professionals in evaluations carried out by St. Petersburg State Polytechnic University. He is a supervisor of the international master’s degree program in microelectronics of telecommunications systems. His research interests include areas of circuits and systems for wireless communications, integrated circuit theory and design, and integrated circuit computer simulation. From 2003 to 2005, Professor Korotkov was an associate editor of IEEE Transactions on Circuits and Systems, Pt II . Currently, he is an associate editor ofRadio Electronics and Communications Systems (Ukraine) and St. Petersburg State Polytechnic University Journal, Journal of Computer Science, and Telecommunication and Control Systems (Russia). Professor Korotkov has authored two books and published about 170 papers and reports. Guest Editorial 5G Wireless: Technology, Standard and Practice Fa-Long Luo and Alexander S. Korotkov networks (mass base station deployments), extreme increase in the number of antennas in transmitter arrays and their interaction with a novel waveform, integration of both wireless and optical sides of telecom networks, and design of wireless networks from the perspective of complex systems science.

    The third paper,“Signal Processing Techniques for 5G: An Overview,”gives an overview of the main signal - processing techniques being developed for 5G wireless communications. At the beginning of this paper, the author reviews six orthogonal and non-orthogonal waveform-generation and modulation schemes: generalized frequency - division multiplexing (GFDM), filter bank multi-carrier (FBMC) transmission, universal filtered multicarrier (UFMC) transmission, bi - orthogonal frequency division multiplexing (BFDM), sparse code multiple access (SCMA) and non-orthogonal multiple access (NOMA). Then, the author discusses spatial signal processing algorithms and implementations of massive multiple-input multiple-output (massive MIMO), 3D beamforming and diversity, and multiplexing based on orbital angular momentum (OAM). The author also briefly reviews aspects of signal processing for other emerging techniques in 5G, such as millimeter wave, cloud radio access networks, full duplex mode, and digital RF processing.

    The fourth paper,“Energy-Efficient Large-Scale Antenna Systems with Hybrid Digital-Analog Beamforming Structure,” provides both theoretical analysis and simulations on the design of a large-scale antenna system (LSAS) with beamforming (BF), which is believed to significantly increase energy efficiency (EE) and spectral efficiency (EE) in a 5G wireless system. The paper investigates the optimal antenna configuration in an N × M hybrid BF structure, where N is the number of transceivers, and M is the number of antennas per transceiver. In such a structure, analog BF is introduced for each transceiver, and digital BF is introduced across N transceivers. The emphasis of this paper is EE-SE optimization when NM is fixed and when N and M are independent. The EE-SE relationship at“green”points is first investigated, then the effect of M on EE at a given SE is analyzed. In both cases, the authors show that there is an optimal M that provides the best EE for a given SE. The authors also discuss the optimal M when there is severe inter-user interference. These proposed analyses and results will be very useful in designing and deploying such LSAS for 5G.

    The fifth paper,“An Optimal Lifetime Utility Routing for 5G and Energy-Harvesting Wireless Networks,”looks at wireless sensor networking as a representative of all the different kinds of links involved in 5G. This paper also addresses energy efficiency. The authors propose an energy-harvest-aware route - selection method that incorporates harvest availability and energy storage capacity into routing decisions. In other words, the harvest-aware routing problem is formulated as a linear programming problem with a utility-based objective function that balances two conflicting routing objectives so that the proposed algorithm extends network lifetime. In addition, the authors investigate the effects of various network factors, such as topology, energy consumption rates, and prediction error, on energy savings.

    The sixth paper,“Interference-Cancellation Scheme for Multilayer Cellular Systems,”discusses interference cancellation, which is a challenging problem in a heterogeneous network that has coexisting multilayer cells, multiple standards and multiple application systems. First, an interference signal model that takes into account channel effect as well as time and frequency error is presented. An interference - cancellation scheme based on this model is then investigated. Following that, a method for compensating the timing and carrier frequency offset of an interference signal is presented. In the last step of processing, interference is mitigated by subtracting the estimation of interference signal. Computer simulation shows that the proposed interference-cancellation algorithm significantly improves performance in different channel conditions.

    As we conclude the introduction of this special issue, we would like to thank all authors for their valuable contributions, and we express our sincere gratitude to all the reviewers for their timely and insightful comments submitted papers. It is hoped that the contents in this special issue are informative and useful from the aspects of technology, standardization, and implementation.
    5G: Vision, Scenarios and Enabling Technologies
    Yifei Yuan, Xiaowu Zhao
    2015, 13(1):  3-10.  doi:10.3969/j.issn.1673-5188.2015.01.001
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    This paper presents the authors ’vision for 5G wireless systems, which are expected to be standardized around 2020 (IMT-2020). In the future, ubiquitous service will be the key requirement from an end-user ’s prospective, and 5G networks will need to support a vast mesh of human-to-human, human-to-machine, and machine-to-machine connections. Moreover, 5G will need to support these connections in an energy-efficient manner. Various 5G enabling technologies have been extensively discussed. These technologies aim to increase radio link efficiency, expand operating bandwidths, and increase cell density. With these technologies, 5G systems can accommodate a massive volume of traffic and a massive number of connections, which is fundamental to providing ubiquitous services. Another aspect of 5G technology is the transition to an intelligent cloud that coordinates network access and enables flatter architecture.
    Towards 5th Generation Wireless Communication Systems
    Nicola Marchetti
    2015, 13(1):  11-19.  doi:10.3969/j.issn.1673-5188.2015.01.002
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    This paper introduces the general landscape of next?generation wireless communication systems (5G), including the impetus and requirements of 5G and the candidate technologies that might help 5G achieve its goals. The following areas, which the author considers particularly relevant, are discussed: detection of and access to free spectrum over bands of a heterogeneous nature, ex?treme densification of networks (massive base station deployments), extreme increase in the number of antennas in base station ar?rays and their interaction with a novel waveform, integration of both wireless and optical sides of telecom networks, and study of wireless networks from the perspective of complex systems science. The author discusses recent research conducted by his team in each of these research areas.
    Signal Processing Techniques for 5G: An Overview
    Fa-Long Luo
    2015, 13(1):  20-27.  doi:10.3969/j.issn.1673-5188.2015.01.003
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    This paper gives an outline of the algorithms and implementation of the main signal processing techniques being developed for 5G wireless communication. The first part contains a review and comparison of six orthogonal and non-orthogonal waveform-generation and modulation schemes: generalized frequency-division multiplexing (GFDM), filter-bank multicarrier (FBMC), universal filtered multicarrier (UFMC), bi-orthogonal frequency-division multiplexing (BFDM), sparse-code multiple-access (SCMA), and non-orthogo-nal multiple access (NOMA). The second part discusses spatial signal processing algorithms and implementations for massive multiple-input multiple-output (massive-MIMO), 3D beamforming and diversity, and orbital angular momentum (OAM) based multi-plexing. The last part gives an overview of signal processing aspects of other emerging techniques in 5G, such as millimeter-wave, cloud radio access networks, full duplex mode, and digital radio-frequency processing.
    Energy-Efficient Large-Scale Antenna Systems with Hybrid Digital-Analog Beamforming Structure
    Shuangfeng Han, Chih-Lin I, Zhikun Xu, Qi Sun, Haibin Li
    2015, 13(1):  28-34.  doi:10.3969/j.issn.1673-5188.2015.01.004
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    A large-scale antenna system (LSAS) with digital beamforming is expected to significantly increase energy efficiency (EE) and spectral efficiency (SE) in a wireless communication system. However, there are many challenging issues related to calibration, energy consumption, and cost in implementing a digital beamforming structure in an LSAS. In a practical LSAS deployment, hybrid digital-analog beamforming structures with active antennas can be used. In this paper, we investigate the optimal antenna configuration in an N × M beamforming structure, where N is the number of transceivers, M is the number of active antennas per transceiver, where analog beamforming is introduced for individual transceivers and digital beamforming is introduced across all N transceivers. We analyze the green point, which is the point of maximum EE on the EE-SE curve, and show that the log-scale EE scales linearly with SE along a slope of -lg2/N. We investigate the effect of M on EE for a given SE value in the case of fixed NM and independent N and M. In both cases, there is a unique optimal M that results in optimal EE. In the case of independent N and M, there is no optimal (N, M) combination for optimizing EE. The results of numerical simulations are provided, and these results support our analysis.
    An Optimal Lifetime Utility Routing for 5G and Energy-Harvesting Wireless Networks
    Gina Martinez, Shufang Li, Chi Zhou
    2015, 13(1):  35-42.  doi:10.3969/j.issn.1673-5188.2015.01.005
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    Harvesting energy from environmental sources such as solar and wind can mitigate or solve the limited-energy problem in wireless sensor networks. In this paper, we propose an energy-harvest-aware route-selection method that incorporates harvest availability properties and energy storage capacity limits into the routing decisions. The harvest-aware routing problem is formulated as a linear program with a utility-based objective function that balances the two conflicting routing objectives of maximum total and maximum minimum residual network energy. The simulation results show that doing so achieves a longer network lifetime, defined as the time-to-first-node-death in the network. Additionally, most existing energy-harvesting routing algorithms route each traffic flow independently from each other. The LP formulation allows for a joint optimization of multiple traffic flows. Better residual energy statistics are also achieved by such joint consideration compared to independent optimization of each commodity.
    Interference-Cancellation Scheme for Multilayer Cellular Systems
    Wei Li, Yue Zhang, Li-Ke Huang
    2015, 13(1):  43-49.  doi:10.3969/j.issn.1673-5188.2015.01.006
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    A 5G network must be heterogeneous and support the co-existence of multilayer cells, multiple standards, and multiple application systems. This greatly improves link performance and increases link capacity. A network with co-existing macro and pico cells can alleviate traffic congestion caused by multicast or unicast subscribers, help satisfy huge traffic demands, and further extend converge. In order to practically implement advanced 5G technology, a number of technical problems have to be solved, one of which is inter-cell interference. A method called Almost Blank Subframe (ABS) has been proposed to mitigate interference; however, the reference signal in ABS still causes interference. This paper describes how interference can be cancelled by using the information in the ABS. First, the interference-signal model, which takes into account channel effect, time and frequency error, is presented. Then, an interference-cancellation scheme based on this model is studied. The timing and carrier frequency offset of the interference signal is compensated. Afterwards, the reference signal of the interfering cell is generated locally and the channel response is estimated using channel statistics. Then, the interference signal is reconstructed according to previous estimation of channel, timing, and carrier frequency offset. The interference is mitigated by subtracting the estimated interference signal. Computer simulation shows that this interference-cancellation algorithm significantly improves performance under different channel conditions.
    Review
    Big-Data Processing Techniques and Their Challenges in Transport Domain
    Aftab Ahmed Chandio, Nikos Tziritas, Cheng-Zhong Xu
    2015, 13(1):  50-59.  doi:10.3969/j.issn.1673-5188.2015.01.007
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    This paper describes the fundamentals of cloud computing and current big-data key technologies. We categorize big-data processing as batch-based, stream-based, graph-based, DAG-based, interactive-based, or visual-based according to the processing technique. We highlight the strengths and weaknesses of various big-data cloud processing techniques in order to help the big-data community select the appropriate processing technique. We also provide big data research challenges and future directions in aspect to transportation management systems.
    Research Paper
    Utility-Based Joint Scheduling Approach Supporting Multiple Services for CoMP-SU-MIMO in LTE-A System
    Borui Ren, Gang Liu, Bin Hou
    2015, 13(1):  60-66.  doi:10.3969/j.issn.1673-5188.2015.01.008
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    In this paper, we study utility-based resource allocation for users supporting multiple services in a LTE-A system with coordinated multi-point transmission for single-user multi-input multi-output (CoMP-SU-MIMO). We designed Joint Transmission Power Control (JTPC) for the selected clusters for minimizing power consumption in LTE-A systems. The objective of JTPC is to calculate the optimal transmission power for each scheduled user and subcarrier. Moreover, based on the convex optimization theory, we propose the dynamic sector selection method in which the average sector throughput and cell-edge users (UEs) rates are performed to achieve the optimal solution. Simulation results show that the system performance achieved by using the proposed suboptimal algorithm is close to that achieved by the dual decomposition method.
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