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

Massive multiple-input multiple-output (MIMO) systems hold the potential to be an enabling technology for 5G cellular. Uniform planar array (UPA) antenna structures are a focus of much commercial discussion because of their ability to enable a large number of antennas in a relatively small area. With UPA antenna structures, the base station can control the beam direction in both the horizontal and vertical domains simultaneously. However, channel conditions may dictate that one dimension requires higher channel state information (CSI) accuracy than the other. We propose the use of an additional one bit of feedback information sent from the user to the base station to indicate the preferred domain on top of the feedback overhead of CSI quantization in frequency division duplexing (FDD) massive MIMO systems. Combined with variable-rate CSI quantization schemes, the numerical studies show that the additional one bit of feedback can increase the quality of CSI significantly for UPA antenna structures.

Exploiting the preferred domain of FDD massive MIMO systems with uniform planar arrays

Method for transmitting and receiving reference signal in wireless communication system

A method of receiving a signal by a receiver in a mobile communication system is provided. The method includes: receiving a reference signal from a transmitter; determining first channel information based on the received reference signal; receiving a data signal based on the first channel information; and determining second channel information based on the received data signal and the first channel information. Iterative channel estimation is performed to reduce channel estimation errors by determining errors of signals received from a turbo decoding unit and using symbol information as pilots even in subcarriers where the pilot signals are not transmitted, and to increase the accuracy of LLR calculation through an iteration process such as a detection and decoding process in comparison with the conventional technology, thereby increasing the reception performance of the turbo decoding unit and improving communication efficiency.

Method and apparatus for estimating communication channel in mobile communication system

A method of forming a beam-link by a Base Station (BS) in a wireless communication system using a beamforming scheme includes determining at least one downlink beams to be used for downlink transmission and/or reception, transmitting a reference signal to a Mobile Station via the at least one downlink beam, receiving the reference signal via an uplink beam from the Mobile station, and updating the at least one downlink beam to increase a Signal-to-Noise Ratio (SNR). Accordingly, a beam-link using an initial beam-link between the BS and the MS and adaptive beamforming can be rapidly constructed in a high frequency band BDMA cellular system.

Method and apparatus for fast beam-link construction in mobile communication system

The present disclosure relates to a 5G or pre-5G communication system for supporting a higher data rate beyond a 4G communication system such as LTE. According to an embodiment of the present invention, a method for transmitting a synchronization signal by a base station in a filter bank multi carrier (FBMC) system and a base station using the same may be provided, the method comprising the steps of: generating a frequency-domain quadrature amplitude modulation (QAM) symbol sequence having a length of k for a synchronization signal; mapping the QAM symbol sequence to a sub-carrier of a filter bank on the basis of the correlation characteristic of the synchronization signal; generating a quadrature amplitude modulation-filter bank multicarrier (QAM-FBMC) symbol including the synchronization signal on the basis of the mapping, and transmitting the generated QAM-FBMC symbol. In addition, a terminal communicating with the base station and an operation method for the terminal may be provided.

Ji-Yun Seol

Papers

Exploiting the preferred domain of FDD massive MIMO systems with uniform planar arrays

Method for transmitting and receiving reference signal in wireless communication system

Method and apparatus for estimating communication channel in mobile communication system

Method and apparatus for fast beam-link construction in mobile communication system

Synchronization method and apparatus in mobile communication system