5G Mobile Communications

Mobile Internet and IoT (Internet of Things) are the two main market drivers for 5G. There will be a massive number of use cases for Mobile Internet and IoT, such as augmented reality, virtual reality, remote computing, eHealth services, automotive driving and so on. All these use cases can be grouped into three usage scenarios, i.e., eMBB (Enhanced mobile broadband), mMTC (Massive machine type communications) and URLLC (Ultra-reliable and low latency communications). Eight key capabilities including peak data rate, latency and connection density, etc., are defined to meet the requirements of usage scenarios. Based on the usage scenarios, several typical deployment scenarios including indoor hotspots, dense urban, urban macro, rural and high-speed scenarios are specified, together with the detailed technical requirements for 5G. Both the deployment scenarios and technical requirements are essential guidance for 5G technical design.

In 5G vision, the spectrum issue is one of the most important parts. Governments, agencies, standardization organizations and research institutions from many countries pay high attention to the 5G spectrum strategies. The appeals for international harmonized spectrum and full band spectrum access are intense, the range of which are possibly from 0-100GHz. This chapter addresses the current spectrum for mobile communications, the future spectrum demand, possible candidate frequency bands and spectrum management considerations. Information from international and regional telecommunications such as ITU, CEPT, APT, and also from different countries are collected and analyzed. Some academic views are also provided for future work.

Spectrum sharing for 5G is motivated by the fact that significantly more spectrum and much wider bandwidths than what is available today will be needed in order to realize the performance targets of 5G. First, spectrum sharing scenarios, i.e. vertical sharing and horizontal sharing, are summarized for different type of spectrum. Second, a thorough review of current spectrum sharing techniques are provided including coordination protocol, GLDB, DSA and MAC-based collision avoidance. Then spectrum sharing is analyzed specific to 5G design and one general architecture to enable 5G spectrum sharing is proposed. Finally, it is concluded that spectrum sharing becomes more and more important for 5G systems as a complementary way of using spectrum.

Every new network generation needs to make a leap in area data throughput, to manage the growing wireless data traffic. The Massive MIMO technology can bring at least ten-fold improvements in area throughput by increasing the spectral efficiency (bit/s/Hz/cell), while using the same bandwidth and density of base stations as in current networks. These extraordinary gains are achieved by equipping the base stations with arrays of a hundred antennas to enable spatial multiplexing of tens of user terminals. This chapter explains the basic motivations and communication theory behind the Massive MIMO technology, and provides implementation-related design guidelines.

Mobile communications in millimeter wave (mmWave) bands have recently attained a wide range of research due to the available ultra-broad spectrum bands. In this chapter, we introduce the key technologies of mmWave communications based on pioneering researches. Channel measurement and modeling as a fundamental issue is presented in Sect. 2. Beam-tracking technique based on large-scale antenna array is studied in Sect. 3. Network architecture, particularly considering unified access and backhaul, is presented in Sect. 4. Current prototypes are introduced in Sect. 5. Finally we summarize the chapter in Sect. 6.

Radio access technologies for cellular mobile communications are typically characterized by multiple access schemes, e.g., frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and OFDMA. In the 4th generation (4G) mobile communication systems such as Long-Term Evolution (LTE) (Au et al., Uplink contention based SCMA for 5G radio access. Globecom Workshops (GC Wkshps), 2014. doi:10.​1109/​GLOCOMW.​2014.​7063547) and LTE-Advanced (Baracca et al., IEEE Trans. Commun., 2011. doi:10.​1109/​TCOMM.​2011.​121410.​090252; Barry et al., Digital Communication, Kluwer, Dordrecht, 2004), standardized by the 3rd Generation Partnership Project (3GPP), orthogonal multiple access based on OFDMA or single carrier (SC)-FDMA is adopted. Orthogonal multiple access was a reasonable choice for achieving good system-level throughput performance with simple single-user detection. However, considering the trend in 5G, achieving significant gains in capacity and system throughput performance is a high priority requirement in view of the recent exponential increase in the volume of mobile traffic. In addition the proposed system should be able to support enhanced delay-sensitive high-volume services such as video streaming and cloud computing. Another high-level target of 5G is reduced cost, higher energy efficiency and robustness against emergencies.

This chapter presents the fundamentals of Faster-than- Nyquist (FTN) signaling. As originally introduced, FTN increases the bit-rate in the signaling bandwidth by packing symbols closer in time, at the cost of introducing intersymbol interference (ISI). We begin with the Euclidean distance properties of bandwidth efficient pulses at FTN rates and describe receivers that mitigate the severe ISI. The FTN achievable information rate is compared with the Nyquist information rate for practical pulses. We then discuss FTN extension to multicarrier systems with not only time packing but also subcarrier, optimizing both the time and frequency packing.

The next generation of wireless networks will face different challenges from new scenarios. The conventional Orthogonal Frequency Division Multiplexing (OFDM) has shown difficulty in fulfilling all demanding requirements. This chapter presents Generalized Frequency Division Multiplexing (GFDM) as a strong waveform candidate for future wireless communications systems which can be combined with several techniques such as precoding or Offset Quadrature Amplitude Modulation (OQAM) and which offers the flexibility to emulate a variety of other popular waveforms as corner cases. This property suggests GFDM as a key technology to allow reconfiguration of the physical layer (PHY), enabling a fast and dynamic evolution of the infrastructure. Additionally, multicarrier transmission theory is covered in terms of Gabor theory. Details on synchronization, channel estimation algorithms and MIMO techniques for GFDM are presented and a description of a proof-of-concept demonstrator shows the suitability of GFDM for future wireless networks.

The focus of this chapter is on novel multi-carrier communication techniques, which share the common goal of increasing spectrum efficiency in future communication systems. In particular, a technology termed Spectrally Efficient Frequency Division Multiplexing (SEFDM) is described in detail outlining its benefits, challenges and trade-offs when compared to the current state-of-the-art. A decade of research has been devoted to examining SEFDM from different angles; mathematical modelling, algorithm optimisation, hardware implementation and system experimentation. The aim of this chapter is to therefore give a taste of this technology and in doing so, the chapter is organised as follows; first, it is explained how SEFDM fits within the remit of future 5th Generation (5G) communication systems; second, the design principles and implementation trade-offs associated with SEFDM systems are described; third, a number of linear and more sophisticated polynomial detection schemes are compared in terms of performance and complexity; finally, the chapter concludes by outlining a number of experimental testbeds which have been developed for the purpose of evaluating the performance of SEFDM in practical scenarios.

In this chapter, we will introduce Full-Duplex (FD) wireless communications for 5G, which enables simultaneous transmission and reception over the same frequency band. In this way, the spectral efficiency can be improved significantly compared with half-duplex (HD). However, there exists severe self interference (SI), signal leakage from the local transmitter to its own receiver. Three different classes of SI mitigation techniques are presented in this chapter: propagation-domain SI suppression, analog-domain SI cancelation, and digital-domain SI cancelation. Furthermore, the system performance of several FD schemes in several different application scenarios is presented. Theoretically, the spectral efficiency of FD bidirectional and cooperative communications can be doubled, while for cognitive radio networks, the FD-based protocol can achieve much better sensing performance than the traditional HD-based cognitive radio schemes.

This chapter deals with a comprehensive analysis of the challenges behind the introduction of Device-to-Device (D2D) communications in the context of 5th Generation (5G) communications. In fact, although D2D communications have emerged as an efficient solution for local traffic between mobile User Equipments (UEs) in proximity in cellular environments, has recently also attracted attention as a key enabling technology for 5G wireless networks. In details, this chapter addresses an overview of the current standardization, its integration in the cellular system architecture, future challenges and open issues. This chapter also provides a performance analysis, which illustrates the important achievements in terms of data rate in a scenario where the proximity communications between devices in an LTE-A system has been introduced for multicast downloading services.

This chapter provides a summary of the State-of-the-Art and future trends related to wireless connectivity solutions for Machine-to-Machine (M2M) Communications and Machine-Type Communications (MTC) that will be part of 5G networks, and technologies beyond 5G.

In the internet of things age, future communication technologies should provide the necessary bandwidth and latency for the connection of billion devices and the development of ubiquitous applications to improve the quality of life. The design of the prospected mobile communication system needs wide skills in wireless communication, analog circuit design, embedded system, microwave technology, and so forth. System level analyses, design space exploration, performance tradeoffs are some key steps that enable the design of low-cost, energy efficient, ubiquitous and flexible transceiver. This chapter provides comprehensive design techniques for 5G mobile communication in the dark silicon era and using More than Moore technology (MtM).

In recent years, with the growing popularity of smart device, our daily life has come to revolve around with spectacularly successful mobile Internet services, which lead to the explosion of data traffic in mobile communication networks. The requirement on communication networks has become a critical issue. By 2020, the global mobile traffic volume will have about 1000 times growth compared to that of 2010. Recent research on 5G requirements indicates that the traffic density in crowded city or hotspot area will reach 20~Tbps/Km². Ultra dense network(UDN) has been introduced to meet the traffic capacity requirement of 5G. as a most promising method. Challenges, network architectures, key technologies will be discussed in this section.

This chapter discusses Cloud Radio Access Networks (C-RAN), which has been viewed as one of the key RAN architectures for 5G networks. First, the basic concept and the initially defined architecture of C-RAN are recalled, including the major benefits in terms of acceleration of network deployment, cost reduction and facilitation of 5G technologies. Then the major challenges of C-RAN realization are analyzed. One of the key challenges lies in fronthaul (FH) transportation which may limit C-RAN implementation in 5G. To address the issue, a new FH interface called Next Generation Fronthaul Interface (NGFI) is proposed. The C-RAN architecture itself evolves with the NGFI interface. The design principles for NGFI are presented including decoupling the FH bandwidth from the number of antennas, decoupling cell and user equipment processing and focusing on high-performance-gain collaborative technologies. NGFI claims the advantages of reduced bandwidth as well as improved transmission efficiency by exploiting the tidal wave effect of mobile network traffic. The transmission of NGFI is Ethernet-based to enjoy the benefits of flexibility and reliability. The major impact, challenges and potential solutions of Ethernet-based FH network are also analyzed. In addition, a prototype is developed and presented to verify NGFI.

In order to better meet the future requirements of mobile Internet and Internet of Things, to fulfill multiple user experience requirements, such as low latency, high data rate, high reliability, low energy consumption, is taken as a key goal of 5G system. Therefore, flatter network architecture, flexible functionality and topology, smart user and traffic awareness, high efficient network operation with lower cost, etc. to facilitate the user-centric wireless network becomes the elements of 5G eco-system access part design.

A worldwide challenge for the design of future cellular systems is to meet the increasing energy demand, while, on the other hand, to lower the emission of greenhouse gases for achieving the environment sustainability. A feasible and efficient method to tackle this issue is to let the communication systems harvest energy from renewable energy sources instead of fossil fuels. However, by employing the energy harvesting (EH) technique, the instability of renewable energy resources introduce new challenges on the design of the upcoming 5G systems. In this chapter, we focus on uplink access schemes and power allocations for EH based heterogeneous networks. First, a heterogeneous access model incorporating EH based mobile users is proposed and followed by a throughput maximization framework. Then, by classifying transmission policies into two main categories (i.e., single-channel vs. multi-channel scenarios), the proposed framework is concretized under various practical conditions, including the availability of central control, causality of harvested energy, channel state information, and others. Finally, future research directions and open problems are discussed.

Green energy has become a promising alternative energy source for powering wireless cellular networks by effectively reducing the network operational expenditure (OPEX) and carbon footprints. However, green energy sources such as solar and wind are harvested from the environment and their availability and capacity are by nature unstable, which poses great challenges to achieve sustainable network operation. In this chapter, we study the energy sustainable performance of a green HetNet where the small cell base stations (SBSs) are powered by green energy sources. Specifically, we first develop an analytical framework to study the energy sustainability of each SBS. The energy buffer at each SBS is modeled as a G/G/1 queue with arbitrary patterns of energy charging and discharging. We apply the diffusion approximation to analyze the transient evolution of the energy buffer, and derive the probability distribution of the queue length and the energy depletion time for a given initial energy level. Based on the energy sustainability analysis, we propose a distributed admission control strategy at SBSs striking a balance between high resource utilization and energy sustainability in the green HetNet. Extensive simulations are conducted to validate the analytical framework and evaluate the sustainability performance of the green HetNets using the proposed distributed admission control scheme. The simulation results demonstrate that relaxing the admission control criteria for the SBSs can improve the resource utilization (i.e, power and spectrum) of the system when the energy is abundant, but can significantly degrade the resource utilization instead when the energy comes short due to poor sustainability performance (i.e., frequent depletion of the SBSs).

Device-to-device (D2D) communications technology is currently being investigated as a potential enabler for the fifth generation (5G) communication networks. Significant performance gains are achievable in a cooperative D2D framework, wherein the user equipments (UEs) cooperate with each other to enable a variety of low-latency proximity-based services or to establish indirect communication links with the Base Station (BS) whenever direct service coverage is not possible. This chapter is focused on the throughput gains achievable in the latter scenario, i.e., when few UEs perform relaying operations to provide indirect service coverage to other UEs. In this direction, resource allocation problems are formulated for a variety of system models operating under the orthogonal frequency division multiple access (OFDMA) cellular or cognitive radio (CR) access architectures. The performance of mobile D2D relaying under different scenarios is evaluated. The system models are designed to study the benefits of incorporating additional capabilities at the devices, such as packet storage (using buffers), energy-harvesting, and cognitive spectrum access within the cooperative D2D framework. Depending on the system model, efficient algorithms are proposed to obtain optimal power allocation, subcarrier assignment, subcarrier pairing, and relay-UE selection policies which maximize the system throughput under a variety of system-dependant constraints. Simulation results demonstrate the effectiveness of our proposed algorithms and the performance improvement of mobile D2D-relaying networks over conventional networks.

With smartphones becoming our everyday companions, high-quality mobile applications have become an important integral of people’s lives. The intensive and ubiquitous use of mobile applications have led to explosive growth of mobile data traffics. To accommodate the surge mobile traffic yet providing the guaranteed service quality to mobile users represent a key issue of 5G mobile networks. This motivates the emergence of Fog computing as a promising, practical and efficient solution tailored to serving mobile traffics. Fog computing deploys highly virtualized computing and communication facilities at the proximity of mobile users. Dedicated to serving the mobile users, Fog computing explores the predictable service demand patterns of mobile users and typically provides desirable localized services accordingly. Stitching above features, Fog computing can provide mobile users with the demanded services through low-latency and short-distance local connections. In this chapter, we introduce the main features of Fog computing and describe its concept, architecture and design goals. Lastly, we discuss on the potential research issues from the perspective of 5G networking.

This chapter provides an overview on existing standards in vehicular networking and highlights new emerging trends towards an integrated infrastructure based on the interworking of heterogeneous technologies. Next-Generation Mobile Vehicular Networks are first characterized by providing an insight on relevant stable standards in wireless communications technologies, with a special focus on Heterogeneous Vehicular Networks. Furthermore, the chapter discusses a general framework supporting opportunistic networking scheme and outlines novel application and use cases based on social- and context-awareness paradigms.

Currently, the exponential growth of mobile data traffic has put an increasingly heavy burden on the cellular network, and results in severe overload problem. As a cost-effective Internet access solution, WiFi networks consume a major portion of the global Internet traffic, and greatly offload the cellular network. However, with the increasing demands for WLAN and the deployment of carrier-WiFi networks, the number of WiFi public hotspots worldwide is expected to increase dramatically. To face this huge increase in the number of densely deployed WiFi networks, and the massive amount of data to be supported by these networks in indoor and outdoor environments, it is necessary to improve the current WiFi standard and define specifications for high-efficiency wireless local area networks (HEWs). In this chapter, the emerging HEW technology is introduced and discussed, including typical use cases, environments, and potential techniques that can be applied for HEWs. We first give the typical HEW use cases, and analyze the main requirements from these use cases and environments. Then, potential techniques, including enhanced medium access, and spatial frequency reuse, are presented and discussed.

The Tactile Internet is envisioned to transport touch and actuation in real-time. It will enable unprecedented applications and revolutionize almost every segment of the society. It is expected that the next generation 5G mobile communications networks will enable the Tactile Internet at the wireless edge. The tactile internet creates daunting new requirements for 5G network design. This chapter focuses on the key technological concepts which lay at the intersection of 5G and the Tactile Internet. The chapter outlines the key application areas of the Tactile Internet. This is followed by an end-to-end architecture of the Tactile Internet. The chapter also presents the key technical requirements of the Tactile Internet along with some potential solutions to meet these requirements. Such solutions revolve around protocol-level and system-level innovations.