Showing papers in "IEEE Wireless Communications in 2014"

Evolution Towards 5G Multi-tier Cellular Wireless Networks: An Interference Management Perspective

Abstract: The evolving fifth generation (5G) cellular wireless networks are envisioned to overcome the fundamental challenges of existing cellular networks, for example, higher data rates, excellent end-to-end performance, and user-coverage in hot-spots and crowded areas with lower latency, energy consumption, and cost per information transfer. To address these challenges, 5G systems will adopt a multi-tier architecture consisting of macrocells, different types of licensed small cells, relays, and device-to-device (D2D) networks to serve users with different quality-of-service (QoS) requirements in a spectrum and energy-efficient manner. Starting with the visions and requirements of 5G multi-tier networks, this article outlines the challenges of interference management (e.g. power control, cell association) in these networks with shared spectrum access (i.e. when the different network tiers share the same licensed spectrum). It is argued that the existing interference management schemes will not be able to address the interference management problem in prioritized 5G multi-tier networks where users in different tiers have different priorities for channel access. In this context a survey and qualitative comparison of the existing cell association and power control schemes is provided to demonstrate their limitations for interference management in 5G networks. Open challenges are highlighted and guidelines are provided to modify the existing schemes in order to overcome these limitations and make them suitable for the emerging 5G systems.

An overview of load balancing in hetnets: old myths and open problems

Abstract: Matching the demand for resources (?load?) with the supply of resources (?capacity?) is a basic problem occurring across many fields of engineering, logistics, and economics, and has been considered extensively in both the Internet and wireless networks. The ongoing evolution of cellular communication networks into dense, organic, and irregular heterogeneous networks (HetNets) has elevated load awareness to a central problem, and introduces many new subtleties. This article explains how several long-standing assumptions about cellular networks need to be rethought in the context of a load-balanced HetNet: we highlight these as three deeply entrenched myths that we then dispel. We survey and compare the primary technical approaches to HetNet load balancing: (centralized) optimization, game theory, Markov decision processes, and the newly popular cell range expansion (a.k.a. biasing), and draw design lessons for OFDMA-based cellular systems. We also identify several open areas for future exploration.

Heterogeneous cloud radio access networks: a new perspective for enhancing spectral and energy efficiencies

Abstract: To mitigate the severe inter-tier interference and enhance the limited cooperative gains resulting from the constrained and non-ideal transmissions between adjacent base stations in HetNets, H-CRANs are proposed as cost-efficient potential solutions through incorporating cloud computing into HetNets. In this article, state-of-the-art research achievements and challenges of H-CRANs are surveyed. In particular, we discuss issues of system architectures, spectral and energy efficiency performance, and promising key techniques. A great emphasis is given toward promising key techniques in HCRANs to improve both spectral and energy efficiencies, including cloud-computing-based coordinated multipoint transmission and reception, large-scale cooperative multiple antenna, cloud-computing-based cooperative radio resource management, and cloud-computingbased self-organizing networks in cloud converging scenarios. The major challenges and open issues in terms of theoretical performance with stochastic geometry, fronthaul-constrained resource allocation, and standard development that may block the promotion of H-CRANs are discussed as well.

Key elements to enable millimeter wave communications for 5G wireless systems

Abstract: Current cellular spectrum at below 3 GHz bands is experiencing severe shortage and cannot keep up with the dramatic proliferation of mobile traffic in the near future, requiring the search for innovative solutions to enable the 5G era. mmWave communications, with a possible gigabit-per-second data rate, have attracted great attention as a candidate for 5G broadband cellular communication networks. However, a complete characterization of mmWave links for 5G wireless networks still remains elusive and there are many challenges and research areas that need to be addressed. In this work we discuss several key elements to enable mmWave communications in 5G: · Channel characteristics regarding mmWave signal attenuation due to free space propagation, atmospheric gaseous and rain are explained. · The hybrid (digital plus analog) beamforming architecture in mmWave system is discussed. · The blockage effect in mmWave communications due to penetration loss and possible approaches are presented. · The application of mmWave transmission with narrow beams in non-orthogonal device-todevice communication is proposed. · mmWave transmission in the booster cell of heterogeneous anchor-booster networks. · mmWave transmission for small cell backhaul is further discussed.

Emerging technologies and research challenges for 5G wireless networks

Abstract: As the take-up of Long Term Evolution (LTE)/4G cellular accelerates, there is increasing interest in technologies that will define the next generation (5G) telecommunication standard. This article identifies several emerging technologies which will change and define the future generations of telecommunication standards. Some of these technologies are already making their way into standards such as 3GPP LTE, while others are still in development. Additionally, we will look at some of the research problems that these new technologies pose.

Game-theoretic resource allocation methods for device-to-device communication

Abstract: Device-to-device communication underlaying cellular networks allows mobile devices such as smartphones and tablets to use the licensed spectrum allocated to cellular services for direct peer-to-peer transmission. D2D communication can use either one-hop transmission (i.e. D2D direct communication) or multi-hop clusterbased transmission (i.e. in D2D local area networks). The D2D devices can compete or cooperate with each other to reuse the radio resources in D2D networks. Therefore, resource allocation and access for D2D communication can be treated as games. The theories behind these games provide a variety of mathematical tools to effectively model and analyze the individual or group behaviors of D2D users. In addition, game models can provide distributed solutions to the resource allocation problems for D2D communication. The aim of this article is to demonstrate the applications of game-theoretic models to study the radio resource allocation issues in D2D communication. The article also outlines several key open research directions.

An architecture for software defined wireless networking

Abstract: Software defined networking, characterized by a clear separation of the control and data planes, is being adopted as a novel paradigm for wired networking With SDN, network operators can run their infrastructure more efficiently, supporting faster deployment of new services while enabling key features such as virtualization In this article, we adopt an SDN-like approach applied to wireless mobile networks that will not only benefit from the same features as in the wired case, but will also leverage on the distinct features of mobile deployments to push improvements even further We illustrate with a number of representative use cases the benefits of the adoption of the proposed architecture, which is detailed in terms of modules, interfaces, and high-level signaling We also review the ongoing standardization efforts, and discuss the potential advantages and weaknesses, and the need for a coordinated approach

Toward a standardized common M2M service layer platform: Introduction to oneM2M

Abstract: At present, most M2M solutions in different industries use proprietary systems that often comprise all layers, from physical to application, to provide their specialized M2M services to customers. These proprietary systems make it difficult to extend systems to support new services, integrate new data, and interoperate with other M2M systems. This issue motivated various standard organizations to establish a new partnership project, the "oneM2M Global Initiative," to standardize a common M2M service layer platform for globally applicable and access-independent M2M services. This article presents a snapshot of the latest progress in oneM2M standardization such as the requirements, agreed architecture, candidate protocols, security aspects, and device management and abstraction technologies.

TeraNets: ultra-broadband communication networks in the terahertz band

Abstract: Terahertz Band communication is envisioned as a key technology to satisfy the data rate requirements of future wireless communication networks, and enable new applications both in classical networking domains as well as in novel nanoscale communication paradigms. Major recent advancements in THz Band technologies are helping to finally close the so called THz Gap and bring practical THz Band communication networks one step closer. This paper surveys the state of the art in THz Band device technologies, and highlights the challenges and potential solutions from the communication and networking perspective as well as in terms of experimental testbeds. Ultimately, a roadmap is defined for the development of THz Band systems as the new frontier in wireless communications.

Device-to-device communications achieve efficient load balancing in LTE-advanced networks

Abstract: In LTE-Advanced networks, besides the overall coverage provided by traditional macrocells, various classes of low-power nodes (e.g., pico eNBs, femto eNBs, and relays) can be distributed throughout the macrocells as a more targeted underlay to further enhance the area?s spectral efficiency, alleviate traffic hot zones, and thus improve the end-user experience. Considering the limited backhaul connections within lowpower nodes and the imbalanced traffic distribution among different cells, it is highly possible that some cells are severely congested while adjacent cells are very lightly loaded. Therefore, it is of critical importance to achieve efficient load balancing among multi-tier cells in LTEAdvanced networks. However, available techniques such as smart cell and biasing, although able to alleviate congestion or distribute traffic to some extent, cannot respond or adapt flexibly to the real-time traffic distributions among multi-tier cells. Toward this end, we propose in this article a device-to-device communicationbased load balancing algorithm, which utilizes D2D communications as bridges to flexibly offload traffic among different tier cells and achieve efficient load balancing according to their real-time traffic distributions. Besides identifying the research issues that deserve further study, we also present numerical results to show the performance gains that can be achieved by the proposed algorithm.

Dynamic spectrum access in cognitive radio networks with RF energy harvesting

Abstract: Spectrum efficiency and energy efficiency are two critical issues in designing wireless networks. Through dynamic spectrum access, cognitive radios can improve the spectrum efficiency and capacity of wireless networks. On the other hand radio frequency (RF) energy harvesting has emerged as a promising technique to supply energy to wireless networks and thereby increase their energy efficiency. Therefore, to achieve both spectrum and energy efficiencies, the secondary users in a cognitive radio network (CRN) can be equipped with the RF energy harvesting capability, and such a network can be referred to as an RF-powered cognitive radio network. In this article we provide an overview of the RF-powered CRNs and discuss the challenges that arise for dynamic spectrum access in these networks. Focusing on the trade-off among spectrum sensing, data transmission, and RF energy harvesting, we then discuss the dynamic channel selection problem in a multi-channel RF-powered CRN. In the RF-powered CRN a secondary user can adaptively select a channel to transmit data when the channel is not occupied by any primary user. Alternatively, the secondary user can harvest RF energy for data transmission if the channel is occupied. The optimal channel selection policy of the secondary user can be obtained by formulating a Markov decision process (MDP) problem. We present some numerical results obtained by solving this MDP problem.

IEEE 802.11AH: the WiFi approach for M2M communications

Abstract: M2M communications are positioned to be one of the fastest growing technology segments in the next decade. Sensor and actuator networks connect communication machines and devices so that they automatically transmit information, serving the growing demand for environmental data acquisition. The IEEE 802.11ah Task Group is working on a new standard to address the particular requirements of M2M networks: a large number of power-constrained stations; a long transmission range; small and infrequent data messages; low data rates; and a non-critical delay. This article explores the key features of this new standard, especially those related to the reduction of energy consumption in the medium access control layer. Given these requirements, a performance assessment of IEEE 802.11ah in four common M2M scenarios, i.e. agriculture monitoring, smart metering, industrial automation, and animal monitoring, is presented.

Spatial modeling of the traffic density in cellular networks

Abstract: Modeling and simulation of a cellular network typically assumes that the target area is divided into regular hexagonal cells and mobile stations (MSs) are uniformly scattered in each cell. This implies a statistically uniform distribution of traffic load over space, but in reality the spatial traffic distribution is highly non-uniform across different cells, which calls for actual spatial traffic models. In this article, we first present the analysis of traffic measurements collected from commercial cellular networks in China, and demonstrate that the spatial distribution of the traffic density (the traffic load per unit area) can be approximated by the log-normal or Weibull distribution depending on time and space. Then we propose a spatial traffic model which generates large-scale spatial traffic variations by a sum of sinusoids that captures the characteristics of log-normally distributed and spatially correlated cellular traffic. The proposed model can be directly used to generate realistic spatial traffic patterns for cellular network simulations, such as performance evaluations of network planning and load balancing.

Direct mobile-to-mobile communication: paradigm for 5G

Abstract: Direct mobile-to-mobile communication, also known as device-to-device (D2D), is expected to be a part of LTE-A in 3GPP Release 12. Direct communication will improve spectrum efficiency, overall system throughput, and energy efficiency, and decrease the delay between devices. It will enable new peer-to-peer and location-based applications and services. Introducing D2D poses many challenges and risks to the longstanding cellular architecture, which is centered on the base station. Therefore, in this article we explain the architectural and technical challenges for D2D communication in the 3GPP standard, and at the end of the article we also highlight the real-life applications and use cases for D2D communication. It is clear that D2D can offer a palette of interesting colors that can paint new business opportunities for mobile stakeholders, promoting its candidacy for next generation wireless communication system.

Powering mobile networks with green energy

Abstract: Explosive mobile data demands are driving a significant growth in energy consumption in mobile networks, and consequently a surge of carbon footprints Reducing carbon footprints is crucial in alleviating the direct impact of greenhouse gases on the earth environment and the climate change With advances of green energy technologies, future mobile networks are expected to be powered by green energy to reduce their carbon footprints This article provides an overview on the design and optimization of green energy enabled mobile networks, discusses the energy models for the analysis and optimization of the networks, and lays out basic design principles and research challenges on optimizing the green energy powered mobile networks

Bluetooth: a viable solution for IoT? [Industry Perspectives]

Abstract: The news that Qualcomm is buying the dominant Bluetooth chip vendor, CSR, is creating speculation in the industry that Qualcomm is betting Bluetooth for Internet of Things (IoT) applications. Bluetooth, the technology once pronounced dead by a trade magazine journalist in 2003 [1], has enjoyed popularity and prosperity in the last 10 years for audio communications and stereo streaming. ABI Research predicts that over 3 billion Bluetooth enabled devices will be shipped in 2014, and over 10 billion Bluetooth enabled devices will be on the market by 2018. With the maturity of the technology and its strong presence in the marketplace, the Bluetooth industry is working on expanding the applications of the technology to short-range wireless communication markets other than audio and stereo communications, such as the Internet of Things (IoT) and machine-to-machine (M2M) communications. Currently, it is being used for M2M applications such as credit card readers [2]. For Bluetooth to be suitable for M2M and IoT applications, it needs to reduce power consumption so that it can be used in batterypowered devices for a longer period of time or even the lifetime of the device. To achieve that, the Bluetooth Special Interest Group (SIG) introduced Bluetooth Low Energy (BLE), which was first specified in Bluetooth 4.0 [3] and further improved in Bluetooth 4.1 [4]. In addition, the Bluetooth stakeholders also expanded work on it, with the Internet Engineering Task Force (IETF) working on the standardization effort of facilitating Bluetooth in exchanging IP packets.

Communicating in the real world: 3D MIMO

Abstract: Spectrum efficiency has long been at the center of mobile communication research, development, and operation. Today it is even more so with the explosive popularity of the mobile Internet, social networks, and smart phones that are more powerful than our desktops used to be not long ago. The discovery of spatial multiplexing via multiple antennas in the mid-1990s has brought new hope to boosting data rates regardless of the limited bandwidth. To further realize the potential of spatial multiplexing, the next leap will be accounting for the three-dimensional real world in which electromagnetic waves propagate. In this article we discuss fundamentals and key technical issues in developing and realizing 3D multi-input multi-output technology for next generation mobile communications.

Challenges of massive access in highly dense LTE-advanced networks with machine-to-machine communications

Abstract: Machine-to-machine wireless systems are being standardized to provide ubiquitous connectivity between machines without the need for human intervention. A natural concern of cellular operators and service providers is the impact that these machine type communications will have on current human type communications. Given the exponential growth of machine type communication traffic, it is of utmost importance to ensure that current voice and data traffic is not jeopardized. This article investigates the limits of machine type communication traffic coexisting with human communication traffic in LTE-A networks, such that human customer churn is minimized. We show that under proper design, the outage probability of human communication is marginally impacted whilst duty cycle and access delay of machine type communications are reasonably bounded to ensure viable M2M operations.

Toward carrier cloud: Potential, challenges, and solutions

Abstract: Mobile operators are in need of means to cope with the ever increasing mobile data traffic, introducing minimal additional capital expenditures on existing infrastructures, principally due to the modest average revenue per user. Network virtualization and cloud computing techniques, along with the principles of the latter in terms of service elasticity, on-demand, and payper-use, could be important enablers for various mobile network enhancements and cost reduction. This article discusses the recent trends the mobile telecommunications market is experiencing, showcasing some of the emerging consumer products and services that are facilitating such trends. The article also discusses the challenges these trends present to mobile network operators. It also demonstrates the possibility of extending cloud computing beyond data centers toward the mobile end user, providing end-to-end mobile connectivity as a cloud service. The article introduces a set of technologies and methods for on-demand provision of a decentralized and elastic mobile network as a cloud service over a distributed network of cloud computing data centers. The concept of Follow-Me-Cloud, whereby not only data but also mobile services intelligently follow their respective users, is also introduced. The novel business opportunities behind the envisioned carrier cloud architecture and service are also discussed, considering various multi-stakeholder scenarios.

On content-centric wireless delivery networks

Abstract: The flux of social media and the convenience of mobile connectivity have created a mobile data phenomenon that is expected to overwhelm mobile cellular networks in the foreseeable future. Despite the advent of 4G/LTE, the growth rate of wireless data has far exceeded the capacity increase of mobile networks. A fundamentally new design paradigm is required to tackle the ever growing wireless data challenge. In this article, we investigate the problem of massive content delivery over wireless networks, and present a systematic view of content-centric network design and its underlying challenges. Toward this end, we first review some of the recent advancements in information-centric networking, which provide the basis of how media contents can be labeled, distributed, and placed across the networks. We then formulate the content delivery task into a content rate maximization problem over a shared wireless channel, which, in contrast to the conventional wisdom that attempts to increase the bit rate of a unicast system, maximizes the content delivery capability with a fixed amount of wireless resources. This conceptually simple change enables us to exploit the content diversity and network diversity by leveraging the abundant computation sources (through application-layer encoding, pushing and caching, etc.) within the existing wireless networks. A network architecture that enables wireless network crowdsourcing for content delivery is then described, followed by an exemplary campus wireless network that encompasses the above concepts.

Spectrum sharing using licensed shared access: the concept and its workflow for LTE-advanced networks

Abstract: Spectrum sharing between an existing incumbent spectrum user and an LTE/LTEAdvanced network with conditions that resemble exclusive licensing have become an appealing solution for mobile network operators to respond to the growing traffic and spectrum demand in a timely manner. While traditional exclusive licensing continues to be the preferred option for MNOs, the new sharing- based licensed shared access (LSA) concept is receiving growing interest in research, regulation and standardization. When applied to mobile communications, the LSA concept would allow an MNO to share spectrum from another type of incumbent spectrum user under a regulator?s supervision with predetermined rules and conditions that guarantee operational certainty for both MNO and incumbent. This article reviews different types of spectrum bands for LTE/LTE-Advanced and beyond networks, and focuses on the LSA concept as a spectrally efficient solution for spectrum access in the future. The article identifies the key stakeholders, including the incumbent spectrum user, the MNO, and the regulator, and their roles in the LSA concept. The key elements in the LSA concept are reviewed, and a work flow for the life cycle of the LSA concept is proposed, consisting of LSA preparation, licensing, deployment, and release phases. The tasks of the key stakeholders in the different phases of the LSA work flow are discussed. The LSA concept can offer a complementary approach to traditional exclusive licensing and license-exempt operations with features that benefit all involved stakeholders. It can be realized with reasonable modifications to the existing network infrastructure and regulatory framework with two new elements for managing the varying spectrum availability: the LSA Repository and LSA Controller.

Full dimension mimo (FD-MIMO): the next evolution of MIMO in LTE systems

Abstract: Full dimension MIMO has attracted significant attention in the wireless industry and academia in the past few years as a candidate technology for the next generation evolution toward beyond fourth generation and fifth generation cellular systems. FD-MIMO utilizes a large number of antennas placed in a 2D antenna array panel for realizing spatially separated transmission links to a large number of mobile stations. The arrangement of these antennas on a 2D panel allows the extension of spatial separation to the elevation domain as well as the traditional azimuth domain. This article discusses features and performance benefits of FD-MIMO along with the ongoing standardization efforts in 3GPP to incorporate FD-MIMO features in the next evolution of LTE. Furthermore, a design of a 2D antenna array, which plays a key role in the implementation of FD-MIMO, is also discussed. Finally, in order to demonstrate the performance benefits of FD-MIMO, system-level evaluation results are provided.

Cognitive radio resource management for future cellular networks

Abstract: The heterogeneous network (HetNet) architecture, device-to-device (D2D) communications, and coexistence with existing wireless systems have been regarded as new communication paradigms introduced in LTE-A/LTE-B cellular networks. To facilitate these paradigms, considerable research has shown promise of the cognitive radio (CR) technology, particularly the cognitive radio resource management (CRRM) on the top of resource allocation to control Layer-1 and Layer-2 radio operations, thus eliminating the concerns of potential system impacts and operation unreliability to bridge the gap between cellular and CR technologies. To support diverse communication paradigms with different challenges, a variety of CRRM schemes have been recently proposed, which however significantly perplexes the system implementation. To provide a general reconfigurable framework, in this article, we reveal a software-defined design of the CRRM. Through proper configurations, this software- defined design is able to adapt to diverse communication paradigms in LTE-A/LTE-B, and provides transmission reliability in terms of quality- of-service guarantees via the optimum control of the design. Supporting diverse CRRM schemes, this design substantially simplifies the system realization to bring the development of the CRRM to the next stage of practice for the fifth generation (5G) cellular network.

MAC protocol identification using support vector machines for cognitive radio networks

Abstract: Cognitive radio is regarded as a potential solution to address the spectrum scarcity issue in wireless communication. In CR, an unlicensed network user (secondary user) is enabled to dynamically/adaptively access the frequency channels considering the current state of the external radio environment. In this article, we investigate the medium access control protocol identification for applications in cognitive MAC. MAC protocol identification enables CR users to sense and identify the MAC protocol types of any existing transmissions (primary or secondary users). The identification results will be used by CR users to adaptively change their transmission parameters in order to improve spectrum utilization, as well as to minimize potential interference to primary and other secondary users. MAC protocol identification also facilitates the implementation of communications among heterogeneous CR networks. In this article, we consider four MAC protocols, including TDMA, CSMA/CA, pure ALOHA, and slotted ALOHA, and propose a MAC identification method based on machine learning techniques. Computer simulations are performed to evaluate the MAC identification performance.

Intelligent access network selection in converged multi-radio heterogeneous networks

Abstract: Heterogeneous multi-radio networks are emerging network architectures that comprise hierarchical deployments of increasingly smaller cells. In these deployments, each user device may employ multiple radio access technologies to communicate with network infrastructure. With the growing numbers of such multi-radio consumer devices, mobile network operators seek to leverage spectrum across diverse radio technologies, thus boosting capacity and enhancing quality of service. In this article, we review major challenges in delivering uniform connectivity and service experience to converged multiradio heterogeneous deployments. We envision that multiple radios and associated device/infrastructure intelligence for their efficient use will become a fundamental characteristic of future 5G technologies, where the distributed unlicensed-band network (e.g., WiFi) may take advantage of the centralized control function residing in the cellular network (e.g., 3GPP LTE). Illustrating several available architectural choices for integrating WiFi and LTE networks, we specifically focus on interworking within the radio access network and detail feasible options for intelligent access network selection. Both network- and user-centric approaches are considered, wherein the control rests with the network or the user. In particular, our system-level simulation results indicate that load-aware usercentric schemes, which augment SNR measurements with additional information about network loading, could improve the performance of conventional WiFi-preferred solutions based on minimum SNR threshold. Comparison with more advanced network-controlled schemes has also been completed to confirm attractive practical benefits of distributed user-centric algorithms. Building on extensive system-wide simulation data, we also propose novel analytical space-time methodology for assisted network selection capturing user traffic dynamics together with spatial randomness of multi-radio heterogeneous networks.

Large-scale study of city dynamics and urban social behavior using participatory sensing

Abstract: The ubiquitous availability of computing technology such as smartphones, tablets, and other easily portable devices, and the worldwide adoption of social networking sites make it increasingly possible for one to be connected and continuously contribute to this massively distributed information publishing process. In this scenario, people act as social sensors, voluntarily providing data that capture their daily life experiences, and offering diverse observations on both the physical world (e.g., location) and the online world (e.g., events). This large amount of social data can provide new forms of valuable information that are currently not available on this scale via any traditional data collection methods, and can be used to enhance decision making processes. In this article, we argue that location-based social media systems, such as Instagram and Foursquare, can act as valuable sources of large-scale sensing, providing access to important characteristics of urban social behavior much more quickly than traditional methods. We also discuss different applications and techniques that can exploit the data shared in these systems to enable large-scale and near-real-time analyses and visualization of different aspects of city dynamics.

A survey of converging solutions for heterogeneous mobile networks

Abstract: In 5G systems, the current machine-tomachine communications using Wi-Fi or Bluetooth provide a good opportunity to dramatically increase overall performance. Converged mobile networks can provide M2M communications with significant performance improvements by sharing unlicensed spectrum bands in cellular networks, such as Long Term Evolution-Advanced, by using cognitive radio technology. Thus, the converged mobile network will become one of the most popular future research topics because mobile multimedia content services have been generally accepted among mobile device users. In this article, we provide an overview of converged mobile networks, investigating different types of converged mobile networks, different types of convergence, and the current problems and solutions. This survey article also proposes potential research topics in converged mobile networks.

The role of mobility for D2D communications in LTE-advanced networks: energy vs. bandwidth efficiency

Abstract: Energy efficiency and bandwidth efficiency are two paramount important performance metrics for device-to-device communications. In this work, we investigate how mobility impacts EE and BE in a general framework of an LTEAdvanced network. First, we deploy a simple but practical mobility model to capture the track of the mobile devices. In particular, unlike previous works focusing on mobility velocity, which is difficult to obtain in practical mobile D2D systems, we deploy the parameter of device density to describe the device mobility. Next, we investigate the relationship between EE and BE in a mobile environment, and propose an EE-BE-aware scheduling scheme with a dynamic relay selection strategy that is flexible enough for making the transmission decision, including relay selection, rate allocation, and routing. Subsequently, through rigorous theoretical analysis, we derive a precise EE-BE trade-off curve for any device density and achieve the condition to attain the optimal EE and BE simultaneously. Finally, numerical simulation results are provided to validate the efficiency of the proposed scheduling scheme and the correctness of our analysis.

CONCERT: a cloud-based architecture for next-generation cellular systems

Abstract: Cellular networks are one of the cornerstones of our information-driven society. However, existing cellular systems have been seriously challenged by the explosion of mobile data traffic, the emergence of machine-type communications, and the flourishing of mobile Internet services. In this article, we propose CONCERT, a converged edge infrastructure for future cellular communications and mobile computing services. The proposed architecture is constructed based on the concept of control/data (C/D) plane decoupling. The data plane includes heterogeneous physical resources such as radio interface equipment, computational resources, and software-defined switches. The control plane jointly coordinates physical resources to present them as virtual resources, over which software-defined services including communications, computing, and management can be deployed in a flexible manner. Moreover, we introduce new designs for physical resources placement and task scheduling so that CONCERT can overcome the drawbacks of the existing baseband-up centralization approach and better facilitate innovations in next-generation cellular networks. These advantages are demonstrated with application examples on radio access networks with C/D decoupled air interface, delaysensitive machine-type communications, and realtime mobile cloud gaming. We also discuss some fundamental research issues arising with the proposed architecture to illuminate future research directions.

Characteristics of mobile youtube traffic

Abstract: In this work we present the characterization of the mobile network traffic generated by one of the most relevant social networking applications: YouTube. Understanding its characteristics is of major importance to evaluate its impact on mobile networks and optimize network or application design. For this purpose, we have performed a set of experiments capturing traffic from Apple iOS and Android terminals connected to 3G mobile networks. Our results show that the video formats are 3GP formats, which use lower encoding rates than in other networks. As in accesses from other networks, YouTube servers transfer the video clip with an initial burst and a throttling phase, but they apply different parameters for clients located in mobile networks. Additionally, the mobile terminal can strongly influence the download. Our results with high-end Android terminals show that the client implements a dual-threshold buffer policy that interrupts and resumes the download depending on its buffer occupancy. Our results with iOS terminals show that the video clip download is not interrupted by the client, and a large amount of data may be accumulated at the player buffer. In mid-range Android terminals the TCP receive window may additionally throttle the download if the player buffer is filled up.