There is considerable pressure to define the key requirements of 5G, develop 5G standards, and perform technology trials as quickly as possible. Normally, these activities are best done in series but there is a desire to complete these tasks in parallel so that commercial deployments of 5G can begin by 2020. 5G will not be an incremental improvement over its predecessors; it aims to be a revolutionary leap forward in terms of data rates, latency, massive connectivity, network reliability, and energy efficiency. These capabilities are targeted at realizing high-speed connectivity, the Internet of Things, augmented virtual reality, the tactile internet, and so on. The requirements of 5G are expected to be met by new spectrum in the microwave bands (3.3-4.2 GHz), and utilizing large bandwidths available in mm-wave bands, increasing spatial degrees of freedom via large antenna arrays and 3-D MIMO, network densification, and new waveforms that provide scalability and flexibility to meet the varying demands of 5G services. Unlike the one size fits all 4G core networks, the 5G core network must be flexible and adaptable and is expected to simultaneously provide optimized support for the diverse 5G use case categories. In this paper, we provide an overview of 5G research, standardization trials, and deployment challenges. Due to the enormous scope of 5G systems, it is necessary to provide some direction in a tutorial article, and in this overview, the focus is largely user centric, rather than device centric. In addition to surveying the state of play in the area, we identify leading technologies, evaluating their strengths and weaknesses, and outline the key challenges ahead, with research test beds delivering promising performance but pre-commercial trials lagging behind the desired 5G targets.

5G : A tutorial overview of standards, trials, challenges, deployment, and practice

This paper presents a novel ultrawideband wireless spread spectrum millimeter-wave (mmWave) channel sounder that supports both a wideband sliding correlator mode and a realtime spread spectrum mode, also known as wideband correlation or direct correlation. Both channel sounder modes are capable of absolute propagation delay (time of flight) measurements with up to 1 GHz of radio frequency null-to-null bandwidth, and can measure multipath with a 2-ns time resolution. The sliding correlator configuration facilitates long-distance measurements with angular spread and delay spread for up to 185 dB of maximum measurable path loss. The real-time spread spectrum mode is shown to support short-range, small-scale temporal, and Doppler measurements (minimum snapshot sampling interval of 32.753 μs) with a substantial dynamic fading range of 40 dB for human blockage and dynamic urban scenarios. The channel sounder uses field programmable gate arrays, analog-to-digital converters, digital-to-analog converters, and low-phase-noise rubidium standard references for frequency/time synchronization and absolute time delay measurements. Using propagation theory, several methods are presented here to calibrate and verify the accuracy of the channel sounder, and an improved diffraction model for human blockage, based on the METIS model but now including directional antenna gains, is developed from measurements using the channel sounder. The mmWave channel sounder described here may be used for accurate spatial and temporal raytracing calibration, to identify individual multipath components, to measure antenna patterns, for constructing spatial profiles of mmWave channels, and for developing statistical channel impulse response models in time and space.

A Flexible Millimeter-Wave Channel Sounder With Absolute Timing

With the rapid development of marine activities, there has been an increasing number of Internet-of-Things (IoT) devices on the ocean. This leads to a growing demand for high-speed and ultrareliable maritime communications. It has been reported that a large performance loss is often inevitable if the existing fourth-generation (4G), fifth-generation (5G), or satellite communication technologies are used directly on the ocean. Hence, conventional theories and methods need to be tailored to this maritime scenario to match its unique characteristics, such as dynamic electromagnetic propagation environments, geometrically limited available base station (BS) sites and rigorous service demands from mission-critical applications. Toward this end, we provide a survey on the demand for maritime communications enabled by state-of-the-art hybrid satellite-terrestrial maritime communication networks (MCNs). We categorize the enabling technologies into three types based on their aims: 1) enhancing transmission efficiency; 2) extending network coverage; and 3) provisioning maritime-specific services. Future developments and open issues are also discussed. Based on this discussion, we envision the use of external auxiliary information, such as sea state and atmosphere conditions, to build up an environment-aware, service-driven, and integrated satellite-air-ground MCN.

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Hybrid Satellite-Terrestrial Communication Networks for the Maritime Internet of Things: Key Technologies, Opportunities, and Challenges

Millimeter-wave (mmWave) will be used for fifth-generation (5G) wireless systems. While many recent empirical studies have presented propagation characteristics at mmWave bands, macrodiversity and Coordinated Multipoint (CoMP) have not been carefully studied. This paper describes a large-scale mmWave base station diversity measurement campaign at 73 GHz in an urban microcell (UMi) in downtown, Brooklyn, NY, USA, and provides the first detailed analysis of CoMP and macrodiversity performance based on extensive measurements. The research employed nine different base station locations in a 200 m by 200 m area and considered 36 individual transmitter–receiver combinations for extensive co- and cross-polarized varying directional beam channel impulse response measurements. From the measured data, hypothesis testing with cross-validation shows that large-scale shadow fading of directional path loss at an RX from multiple base stations can be modeled as being independent. To consider life-like human blockage in CoMP and macrodiversity analysis, simulated human blockage traces are superimposed on the directional measurements to quantitatively show that a user that is served by multiple base stations undergoes dramatically less outage in the presence of rapid fading events, compared to a single serving base station. Moreover, the base station diversity measurements are used to determine the effectiveness of downlink precoding techniques for mmWave CoMP. While results show that the coordination can improve network performance by suppressing interference when it exists, nearly half of the 680 000 directional CoMP measurements (~43%) result in no interference for either user, meaning that macrodiversity alone may offer sufficient link and capacity improvement and that CoMP may not be necessary for interference coordination at mmWave when narrow directional beams are used.

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Millimeter-Wave Base Station Diversity for 5G Coordinated Multipoint (CoMP) Applications

With the rapid development of marine activities, there has been an increasing number of maritime mobile terminals, as well as a growing demand for high-speed and ultra-reliable maritime communications to keep them connected. Traditionally, the maritime Internet of Things (IoT) is enabled by maritime satellites. However, satellites are seriously restricted by their high latency and relatively low data rate. As an alternative, shore & island-based base stations (BSs) can be built to extend the coverage of terrestrial networks using fourth-generation (4G), fifth-generation (5G), and beyond 5G services. Unmanned aerial vehicles can also be exploited to serve as aerial maritime BSs. Despite of all these approaches, there are still open issues for an efficient maritime communication network (MCN). For example, due to the complicated electromagnetic propagation environment, the limited geometrically available BS sites, and rigorous service demands from mission-critical applications, conventional communication and networking theories and methods should be tailored for maritime scenarios. Towards this end, we provide a survey on the demand for maritime communications, the state-of-the-art MCNs, and key technologies for enhancing transmission efficiency, extending network coverage, and provisioning maritime-specific services. Future challenges in developing an environment-aware, service-driven, and integrated satellite-air-ground MCN to be smart enough to utilize external auxiliary information, e.g., sea state and atmosphere conditions, are also discussed.

This paper presents outdoor field experimental results showing the achievement of 3-Gbps throughput performance based on 400-MHz bandwidth transmission when applying carrier aggregation with 4 component carriers and 4-by-4 single-user multiple-in multiple-out multiplexing in the 15-GHz frequency band in the downlink of 5G cellular radio access. A new radio interface with time division duplexing and radio access based on orthogonal frequency-division multiplexing is implemented in a 5G testbed to support ultra-high speed transmission with low latency. Experimental results in an outdoor open-space parking area show that the peak throughput is 2.8 Gbps in front of a base station (BS) antenna with a high reference signal received power (RSRP) although rank 2 is selected due to the high antenna correlation. The results also show that the average throughput of 2 Gbps is achieved 120 m from the BS antenna. In a courtyard enclosed by building walls, 3.6 Gbps is achieved in an outdoor-to-outdoor environment with a high RSRP and in an outdoor-to-indoor environment where the RSRP is lower due to the penetration loss of glass windows, but a multipath rich environment contributes to actualizing a low antenna correlation.

Field experiments on 5G radio access using 15-GHz band in outdoor small cell environment

This paper presents outdoor field experimental results to clarify the 4x4 MIMO throughput performance from applying multi-point transmission in the 15 GHz frequency band in the downlink of 5G cellular radio access system. The experimental results in large-cell scenario shows that up to 30 % throughput gain compared to non-multi-point transmission is achieved although the difference for the RSRP of two TPs is over 10 dB, so that the improvement for the antenna correlation is achievable and important aspect for the multi-point transmission in the 15 GHz frequency band as well as the improvement of the RSRP. Furthermore in small-cell scenario, the throughput gain of 70% and over 5 Gbps are achieved applying multi-point transmission in the condition of two different MIMO streams transmission from a single TP as distributed MIMO instead of four MIMO streams transmission from a single TP.

Field Experiments on 5G Radio Access Using Multi-Point Transmission

This paper presents indoor and outdoor field experimental results that clarify the 4-by-8 MIMO throughput performance when applying distributed multiple-input multiple-output (MIMO) with a narrow antenna beam tracking in the 15 GHz frequency band in the downlink of a 5G cellular radio access system. The experimental results show that throughput exceeding 15 Gbps is achieved with a high average rank of 4 at an indoor office building lobby and outdoor parking area. As for the distributed MIMO gain in terms of throughput in LoS environments, we achieve throughput gain of 39 % and 105 % in the indoor office building lobby and outdoor parking area, respectively. And also throughput gain of 15 % is achieved in N-LoS environment in office building lobby in multi-path rich environment. We also observe a significant increase of throughput and rank when changing the transmission point (TP) spacing from 0.5 to 1.5 m, while only a limited performance improvement when the TP spacing exceeds 1.5 m. Finally, the throughput performance with various TP positions was tested, and the TP locations when facing each other with a TP spacing of 50 m exhibit excellent performance exceeding 10 Gpbs.

Indoor and Outdoor Experiments on 5G Radio Access Using Distributed MIMO and Beamforming in 15 GHz Frequency Band

The fifth-generation (5G) mobile communication system has attracted much attention to provide various kinds of services and applications for 2020 and later. To verify the feasibility of high presence public viewing service, the world's first maritime 5G experiment is conducted in Windsurfing World Cup 2018. In the experiment, 5G is used for 4K video transmission from a ship to public viewing area at land. This paper briefly reports that downlink and uplink maritime transmission performance of 5G employing 28 GHz band Massive MIMO (Multiple Input Multiple Output) and the success of the public viewing trial.

Maritime 5G Experiment in Windsurfing World Cup by Using 28 GHz Band Massive MIMO

This paper presents indoor experimental results showing the achievement of 14.5 Gbps throughput performance based on 730.5 MHz bandwidth transmission when applying carrier aggregation (CA) with 8 component carriers (CCs) and 4-by-8 single-user multiple-input multiple-output (MIMO) multiplexing in the 15 GHz frequency band in the downlink of 5G cellular radio access. Beam tracking with massive MIMO is implemented in a 5G testbed to support user mobility with a narrow beam. Experimental results in an indoor multi-path rich environment show that the peak throughput is 14.5 Gbps in a line-of-sight (LoS) environment with high mobility-reference signal received power (MRSRP) and low antenna correlation. The results also show that 12.5 Gbps is achieved behind a wall in non-LOS conditions due to ceiling reflections.

Kiichi Tateishi

Papers

Field experiments on 5G radio access using 15-GHz band in outdoor small cell environment

Field Experiments on 5G Radio Access Using Multi-Point Transmission

Indoor and Outdoor Experiments on 5G Radio Access Using Distributed MIMO and Beamforming in 15 GHz Frequency Band

Maritime 5G Experiment in Windsurfing World Cup by Using 28 GHz Band Massive MIMO

Indoor experiment on 5G radio access using beam tracking at 15 GHz band