What will 5G be? What it will not be is an incremental advance on 4G. The previous four generations of cellular technology have each been a major paradigm shift that has broken backward compatibility. Indeed, 5G will need to be a paradigm shift that includes very high carrier frequencies with massive bandwidths, extreme base station and device densities, and unprecedented numbers of antennas. However, unlike the previous four generations, it will also be highly integrative: tying any new 5G air interface and spectrum together with LTE and WiFi to provide universal high-rate coverage and a seamless user experience. To support this, the core network will also have to reach unprecedented levels of flexibility and intelligence, spectrum regulation will need to be rethought and improved, and energy and cost efficiencies will become even more critical considerations. This paper discusses all of these topics, identifying key challenges for future research and preliminary 5G standardization activities, while providing a comprehensive overview of the current literature, and in particular of the papers appearing in this special issue.

What Will 5G Be

The global bandwidth shortage facing wireless carriers has motivated the exploration of the underutilized millimeter wave (mm-wave) frequency spectrum for future broadband cellular communication networks. There is, however, little knowledge about cellular mm-wave propagation in densely populated indoor and outdoor environments. Obtaining this information is vital for the design and operation of future fifth generation cellular networks that use the mm-wave spectrum. In this paper, we present the motivation for new mm-wave cellular systems, methodology, and hardware for measurements and offer a variety of measurement results that show 28 and 38 GHz frequencies can be used when employing steerable directional antennas at base stations and mobile devices.

Millimeter Wave Mobile Communications for 5G Cellular: It Will Work!

The vision of next generation 5G wireless communications lies in providing very high data rates (typically of Gbps order), extremely low latency, manifold increase in base station capacity, and significant improvement in users’ perceived quality of service (QoS), compared to current 4G LTE networks. Ever increasing proliferation of smart devices, introduction of new emerging multimedia applications, together with an exponential rise in wireless data (multimedia) demand and usage is already creating a significant burden on existing cellular networks. 5G wireless systems, with improved data rates, capacity, latency, and QoS are expected to be the panacea of most of the current cellular networks’ problems. In this survey, we make an exhaustive review of wireless evolution toward 5G networks. We first discuss the new architectural changes associated with the radio access network (RAN) design, including air interfaces, smart antennas, cloud and heterogeneous RAN. Subsequently, we make an in-depth survey of underlying novel mm-wave physical layer technologies, encompassing new channel model estimation, directional antenna design, beamforming algorithms, and massive MIMO technologies. Next, the details of MAC layer protocols and multiplexing schemes needed to efficiently support this new physical layer are discussed. We also look into the killer applications, considered as the major driving force behind 5G. In order to understand the improved user experience, we provide highlights of new QoS, QoE, and SON features associated with the 5G evolution. For alleviating the increased network energy consumption and operating expenditure, we make a detail review on energy awareness and cost efficiency. As understanding the current status of 5G implementation is important for its eventual commercialization, we also discuss relevant field trials, drive tests, and simulation experiments. Finally, we point out major existing research issues and identify possible future research directions.

Next Generation 5G Wireless Networks: A Comprehensive Survey

Millimeter-wave (mmW) frequencies between 30 and 300 GHz are a new frontier for cellular communication that offers the promise of orders of magnitude greater bandwidths combined with further gains via beamforming and spatial multiplexing from multielement antenna arrays. This paper surveys measurements and capacity studies to assess this technology with a focus on small cell deployments in urban environments. The conclusions are extremely encouraging; measurements in New York City at 28 and 73 GHz demonstrate that, even in an urban canyon environment, significant non-line-of-sight (NLOS) outdoor, street-level coverage is possible up to approximately 200 m from a potential low-power microcell or picocell base station. In addition, based on statistical channel models from these measurements, it is shown that mmW systems can offer more than an order of magnitude increase in capacity over current state-of-the-art 4G cellular networks at current cell densities. Cellular systems, however, will need to be significantly redesigned to fully achieve these gains. Specifically, the requirement of highly directional and adaptive transmissions, directional isolation between links, and significant possibilities of outage have strong implications on multiple access, channel structure, synchronization, and receiver design. To address these challenges, the paper discusses how various technologies including adaptive beamforming, multihop relaying, heterogeneous network architectures, and carrier aggregation can be leveraged in the mmW context.

Millimeter-Wave Cellular Wireless Networks: Potentials and Challenges

Communication at millimeter wave (mmWave) frequencies is defining a new era of wireless communication. The mmWave band offers higher bandwidth communication channels versus those presently used in commercial wireless systems. The applications of mmWave are immense: wireless local and personal area networks in the unlicensed band, 5G cellular systems, not to mention vehicular area networks, ad hoc networks, and wearables. Signal processing is critical for enabling the next generation of mmWave communication. Due to the use of large antenna arrays at the transmitter and receiver, combined with radio frequency and mixed signal power constraints, new multiple-input multiple-output (MIMO) communication signal processing techniques are needed. Because of the wide bandwidths, low complexity transceiver algorithms become important. There are opportunities to exploit techniques like compressed sensing for channel estimation and beamforming. This article provides an overview of signal processing challenges in mmWave wireless systems, with an emphasis on those faced by using MIMO communication at higher carrier frequencies.

An Overview of Signal Processing Techniques for Millimeter Wave MIMO Systems

It is forecasted that mobile data traffic will increase 1000-fold from 2010 to 2020. As a result, the network must evolve to meet the large and rapidly growing data demand. An effective approach for increasing network capacity is to use additional spectrum. In Rel-13, LTE deployment in unlicensed spectrum is being considered. This feature is called Licensed-Assisted Access (LAA) using LTE. Unlicensed band is attractive due to the large amount of available spectrum. In this paper, we provide an overview of LAA including standardization progress and potential changes. A fairness mechanism for LAA coexistence is also presented. Downlink system performance is analyzed for multi-operator LAA deployment. Three representative scenarios are considered — indoor hotspot, indoor office, and outdoor small cell. It is shown that LAA can offer significant additional capacity to the network. Analysis shows that a co-existence mechanism such as listen-before-talk is needed in co-channel multi-operator deployment to ensure that all users can receive service. With listen-before-talk, co-existence is not an issue even in dense deployment.

LTE in unlicensed spectrum using licensed-assisted access

Availability of large untapped spectrum resources in the millimeter wave (Mmwave) band is suitable for providing a gigabit experience with true local feel using high capacity small cells. Unlike traditional cellular systems, millimeter wave transmissions do not benefit from diffraction and dispersion making it difficult for them to propagate around obstacles thus resulting in higher shadowing loss. They also have less favorable link budgets due to lower power amplifier (PA) output powers and greater pathloss at these higher frequencies. Also, current costs of the Mmwave circuits are higher, but the costs will become much lower when the technology becomes mainstream. One advantage of millimeter wave, however, is that the smaller wavelengths allow for the fabrication of antenna arrays having a much higher number of antenna elements in a much smaller area than is typical at microwave bands. In this article, we outline a framework for Beyond-4G (B-4G) local area network in the millimeter wave band for both access and backhaul including air-interface, antenna-arrays and IC technology. It is shown that Mmwave B-4G small cell technology can provide peak and cell edge rates greater than 10 Gbps and 100 Mbps respectively with latency less than 1msec for local area network.

Moving Towards Mmwave-Based Beyond-4G (B-4G) Technology

In an Orthogonal Frequency Division Multiplexing communication system, a user equipment reports channel quality information that is sufficient to construct a fading profile of a frequency bandwidth and that does not consuming the overhead resulting from the reporting of CQI for every sub-band of the frequency bandwidth. In the communication system, the frequency bandwidth may be represented by multiple sub-band levels, wherein each sub-band level comprises a division of the frequency bandwidth into a number of sub-bands different from the number of sub-bands of the other sub-band levels. The user equipment measures a channel quality associated with each sub-band of a sub-band level of the multiple sub-band levels, selects a sub-band of the sub-band level based on the measured channel qualities, and reports channel quality information associated with the selected sub-band to a radio access network.

Method and apparatus for providing channel quality feedback in an orthogonal frequency division multiplexing communication system

A method includes, in a carrier aggregation system having multiple component carriers, utilizing an air interface based collision avoidance procedure on at least one component carrier that is associated to a cellular radio access technology to check that a radio resource in the at least one component carrier is available; and thereafter communicating on the radio resource using the cellular radio access technology only if the check reveals that the radio resource is available.

Radio operations in a carrier aggregation system

The Internet of Things will bring about billions of connected devices. In the cellular space, machine type communications using LTE is under consideration by many operators. LTE, however, was designed to provide broadband high-speed data service with very low latency. Machine type communications, on the other hand, have a different set of requirements, namely low-rate, low-overhead, low-power-consumption, and low-cost. To address these requirements and also to minimize impact from machine traffic to human traffic, 3GPP has been working on numerous LTE features such as power saving, overload control, signaling reduction, complexity reduction, and coverage enhancement. This paper will provide an overview of LTE enhancements for machine type communications. The paper will also present LTE capacity analysis for machine traffic as well as the battery life of the devices.

Rapeepat Ratasuk

Papers

LTE in unlicensed spectrum using licensed-assisted access

Moving Towards Mmwave-Based Beyond-4G (B-4G) Technology

Method and apparatus for providing channel quality feedback in an orthogonal frequency division multiplexing communication system

Radio operations in a carrier aggregation system

Overview of LTE enhancements for cellular IoT