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 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

The ever growing traffic explosion in mobile communications has recently drawn increased attention to the large amount of underutilized spectrum in the millimeter-wave frequency bands as a potentially viable solution for achieving tens to hundreds of times more capacity compared to current 4G cellular networks. Historically, mmWave bands were ruled out for cellular usage mainly due to concerns regarding short-range and non-line-of-sight coverage issues. In this article, we present recent results from channel measurement campaigns and the development of advanced algorithms and a prototype, which clearly demonstrate that the mmWave band may indeed be a worthy candidate for next generation (5G) cellular systems. The results of channel measurements carried out in both the United States and Korea are summarized along with the actual free space propagation measurements in an anechoic chamber. Then a novel hybrid beamforming scheme and its link- and system-level simulation results are presented. Finally, recent results from our mmWave prototyping efforts along with indoor and outdoor test results are described to assert the feasibility of mmWave bands for cellular usage.

Millimeter-wave beamforming as an enabling technology for 5G cellular communications: theoretical feasibility and prototype results

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

In the near future, i.e., beyond 4G, some of the prime objectives or demands that need to be addressed are increased capacity, improved data rate, decreased latency, and better quality of service. To meet these demands, drastic improvements need to be made in cellular network architecture. This paper presents the results of a detailed survey on the fifth generation (5G) cellular network architecture and some of the key emerging technologies that are helpful in improving the architecture and meeting the demands of users. In this detailed survey, the prime focus is on the 5G cellular network architecture, massive multiple input multiple output technology, and device-to-device communication (D2D). Along with this, some of the emerging technologies that are addressed in this paper include interference management, spectrum sharing with cognitive radio, ultra-dense networks, multi-radio access technology association, full duplex radios, millimeter wave solutions for 5G cellular networks, and cloud technologies for 5G radio access networks and software defined networks. In this paper, a general probable 5G cellular network architecture is proposed, which shows that D2D, small cell access points, network cloud, and the Internet of Things can be a part of 5G cellular network architecture. A detailed survey is included regarding current research projects being conducted in different countries by research groups and institutions that are working on 5G technologies.

A Survey of 5G Network: Architecture and Emerging Technologies

An apparatus and method for selecting an RS using an RS preamble signal in a multi-hop relay BWA communication system are provided, in which a BS sends preamble channel allocation information to at least one RS, the at least one RS sends a preamble to an MS according to the preamble channel allocation information, the MS measures the signal strength level of the preamble received from the at least one RS and reports the signal strength level to the BS, and the BS selects an RS for providing a relay service to the MS according to the signal strength level.

Apparatus and method for selecting relay station using relay station preamble signal in a multi-hop relay broadband wireless access communication system

An upper node is provided for use in a wireless communication system using a relay scheme. The upper node includes means for transmitting, upon a request of a lower relay station for an initial connection of the lower relay station, downlink section information for communication with the lower relay station for a relay service to the lower relay station; and means for transmitting, after the initial connection with the lower relay station, frame configuration information for communication with the lower relay station for a relay service to the lower relay station through the downlink section. The downlink section information includes configuration information of the downlink section for communication with the lower relay station for a relay service.

Apparatus and method for transmitting frame information in multi-hop relay broadband wireless access communication system

A method of feeding back channel information by a receiver in a communication system beam forming is provided. The method includes determining an optimum reception beam using intensities of reference signals received through transmission beams of a base station for a first period through a first path for mapping analog beams of an input signal, and determining an optimum transmission beam of the transmission beams using intensities of reference signals received through the optimum reception beam for a second period through a second path for mapping analog beams of the input signal, and transmitting channel information measured by using a reference signal received through the optimum transmission beam and the optical reception beam to a transmitter.

Method and apparatus for measuring and feeding back channel information in communication system using beam forming

The method for multiple TDD systems coexistence comprising steps of: a newly deployed system calculating a relative time offset Δt for a corresponding frame; the newly deployed system transmitting uplink and downlink signals based on a time reference information obtained by a summation of the relative time offset Δt and a time reference of an existing system. With the method proposed in present invention, uplink and downlink interference from adjacent frequency bands and from adjacent carriers in the same frequency band can be greatly reduced and a transmission time utility can be guaranteed for a newly deployed system.

Method for multiple tdd systems coexistence

A method and apparatus for using a guard band as a data subcarrier in a communication system supporting frequency overlay are provided. In a method of operating mobile station for using a guard band as a subcarrier for signal transmission in a communication system supporting frequency overlay, the method includes searching for a first center frequency located at a position corresponding to an integer multiple of a subcarrier spacing, after searching for the first center frequency, receiving information indicating the numbers n1 and n2 of first additional subcarriers, and performing a first network entry process by using all subcarriers including the first additional subcarriers.

Jae-Weon Cho

Papers

Apparatus and method for selecting relay station using relay station preamble signal in a multi-hop relay broadband wireless access communication system

Apparatus and method for transmitting frame information in multi-hop relay broadband wireless access communication system

Method and apparatus for measuring and feeding back channel information in communication system using beam forming

Method for multiple tdd systems coexistence

Apparatus and method for using guard band as data subcarrier in communication system supporting frequency overlay