METIS is the EU flagship 5G project with the objective of laying the foundation for 5G systems and building consensus prior to standardization. The METIS overall approach toward 5G builds on the evolution of existing technologies complemented by new radio concepts that are designed to meet the new and challenging requirements of use cases today?s radio access networks cannot support. The integration of these new radio concepts, such as massive MIMO, ultra dense networks, moving networks, and device-to-device, ultra reliable, and massive machine communications, will allow 5G to support the expected increase in mobile data volume while broadening the range of application domains that mobile communications can support beyond 2020. In this article, we describe the scenarios identified for the purpose of driving the 5G research direction. Furthermore, we give initial directions for the technology components (e.g., link level components, multinode/multiantenna, multi-RAT, and multi-layer networks and spectrum handling) that will allow the fulfillment of the requirements of the identified 5G scenarios.

Scenarios for 5G mobile and wireless communications: the vision of the METIS project

Wireless data traffic is projected to skyrocket 10 000 fold within the next 20 years. To tackle this incredible increase in wireless data traffic, a first approach is to further improve spectrally efficient systems such as 4G LTE in bands below 6 GHz by using more advanced spectral efficiency techniques. However, the required substantial increase in system complexity along with fundamental limits on hardware implementation and channel conditions may limit the viability of this approach. Furthermore, the end result would be an extremely spectrally efficient system with little room for future improvement to meet the ever-growing wireless data usage. The second approach is to move up in frequency, into an unused nontraditional spectrum where enormous bandwidths are available, such as at millimeter wave (mmWave). The mmWave option enables the use of simple air interfaces since large bandwidths can be exploited (e.g., 2 GHz) to achieve high data rates rather than relying on highly complex techniques originally aimed at achieving a high spectral efficiency with smaller bandwidths. In addition, mmWave systems will easily evolve to even higher system capacities, because there will be plenty of margin to improve the spectral efficiency as data demands further increase. In this paper, a case is made for using mmWave for a fifth generation (5G) wireless system for ultradense networks by presenting an overview of enhanced local area (eLA) technology at mmWave with emphasis on 5G requirements, spectrum considerations, propagation and channel modeling, air-interface and multiantenna design, and network architecture solutions.

Millimeter-Wave Enhanced Local Area Systems: A High-Data-Rate Approach for Future Wireless Networks

We are in the midst of a major paradigm shift in how we manage radio spectrum. This paradigm shift is necessitated by the growth of wireless services of all types and the demand pressure imposed on limited spectrum resources under legacy management regimes. The shift is feasible because of advances in radio and networking technologies that make it possible to share spectrum dynamically in all possible dimensions—i.e., across frequencies, time, location, users, uses, and networks. Realizing the full potential of this shift to Dynamic Spectrum Sharing will require the co-evolution of wireless technologies, markets, and regulatory policies; a process which is occurring on a global scale. This paper provides a current overview of major technological and regulatory reforms that are leading the way toward a global paradigm shift to more flexible, dynamic, market-based ways to manage and share radio spectrum resources. We focus on current efforts to implement database-driven approaches for managing the shared co-existence of users with heterogeneous access and interference protection rights, and discuss open research challenges.

An Overview of Dynamic Spectrum Sharing: Ongoing Initiatives, Challenges, and a Roadmap for Future Research

The ongoing development of mobile communication networks to support a wide range of superfast broadband services has led to massive capacity demand. This problem is expected to be a significant concern during the deployment of the 5G wireless networks. The demand for additional spectrum to accommodate mobile services supporting higher data rates and having lower latency requirements, as well as the need to provide ubiquitous connectivity with the advent of the Internet of Things sector, is likely to considerably exceed the supply, based on the current policy of exclusive spectrum allocation to mobile cellular systems. Hence, the imminent spectrum shortage has introduced a new impetus to identify practical solutions to make the most efficient use of scarce licensed bands in a shared manner. Recently, the concept of dynamic spectrum sharing has received considerable attention from regulatory bodies and governments globally, as it could potentially open new opportunities for mobile operators to exploit spectrum bands whenever they are underutilized by their owners, subject to service level agreements. Although various sharing paradigms have been proposed and discussed, the impact and performance gains of different schemes can be scenario-specific, and may vary depending on the nature of the sharing players, the level of sharing and spectrum access scheme. In this survey, we study the main concepts of dynamic spectrum sharing, different sharing scenarios, as well as the major challenges associated with sharing of licensed bands. Finally, we conclude this survey with open research challenges and suggest some future research directions.

Licensed Spectrum Sharing Schemes for Mobile Operators: A Survey and Outlook

We propose a new approach based on compressive sensing (CS) for the channel matrix estimation problem for “massive” (or large-scale) multiuser (MU) multiple-input multiple-output (MIMO) systems. The system model includes a base station (BS) equipped with a very large number of antennas communicating simultaneously with a large number of autonomous single-antenna user terminals (UTs), over a realistic physical channel with finite scattering model. Based on the idea that the degree of freedom of the channel matrix is smaller than its large number of free parameters, a low-rank matrix approximation based on CS is proposed and solved via a quadratic semidefine programming (SDP). Our analysis and experimental results suggest that the proposed method outperforms the existing ones in terms of estimation error performance or training transmit power, without requiring any knowledge about the statistical distribution or physical parameters of the propagation channel.

Compressive sensing-based channel estimation for massive multiuser MIMO systems

Mobile communication systems have evolved over the past decades and each new generation brought new experience to the users enabled by technology innovations, while keeping some well established principles from previous generations. This trend continued up to LTE (Long Term Evolution) Advanced, the predominant 4th generation system which has just been standardized in 3GPP and is being rolled out soon. How will this trend continue to future systems which will be deployed in some 10 years from now which will be advanced enough to be called “Beyond 4G” (B4G)? This article presents how such B4G systems will look like and some key technologies they will rely on including versatile numerology, massive virtual MIMO from many base stations, both centralized and distributed architectures using fiber optics as backbone, advanced interference mitigation, cognitive self organization, and wideband RF radios.

Vision for Beyond 4G broadband radio systems

Document Title: Intermediate description of the spectrum needs and usage principles Abstract: This document explains and analyses the expected spectrum scenarios addressed in METIS. In a bottom-up process, several spectrum bands are investigated and potential bands for future mobile communications use are explored. An analysis of spectrum access schemes and authorization regimes is provided, allowing to open up new spectrum usage options and to increase the overall spectrum efficiency. Implementation aspects resulting from these new spectrum authorization regimes are discussed in detail. A "Spectrum Sharing Tool Box" is introduced that provides a framework for the efficient implementation of the defined sharing concepts. In a top-down process, the scenarios and test cases defined in METIS deliverable D1.1 are reviewed from a spectrum need and usage point of view. Linking the test cases to the METIS radio access concepts and horizontal topics that are most promising for their implementation allows a first mapping of the test case specific spectrum needs onto new and existing spectrum options, in particular those that might become available under new spectrum sharing regimes. The analysis clearly highlights the importance of making new spectrum usage options available. Without these new options many of the upcoming applications depending on wireless connectivity cannot be implemented. The analysis also indicates that not only more spectrum and more efficient spectrum usage concepts are required but that the broader range of application requirements will in addition result in new challenges on spectrum engineering with respect to guaranteeing coexistence , compatibility, and coverage. It should be noted that deliverable D5.1 presents initial results of the METIS spectrum investigations, i.e., all aspects presented here are under discussion.

Intermediate description of the spectrum needs and usage principles

For controlling a wireless transmission of a network element of a radio access network where signal propagation is unknown, wherein the network element is configured to inhibit use of a licensed shared access spectrum, interference levels in predefined reservation zones are determined, which are introduced by the network element when using the licensed shared access spectrum. It is checked whether or not the interference levels violate agreed interference levels in the predefined reservation zones of the licensed shared access spectrum, and the network element is configured to allow use of the licensed shared access spectrum in case the interference levels do not violate the agreed interference levels in the predefined reservation zones.

Use of licensed shared spectrum in a radio access network where signal propagation is unknown

The expected increase of the traffic volume in mobile broadband networks and the upcoming spectrum scarcity, require an optimization of the usage of the spectrum. One of the solutions is Authorised/Licensed Shared Access (ASA/LSA) 1 , a new regulatory concept that allows license holders (incumbents) to share spectrum with other service providers, under well-defined conditions, unlocking additional bands which are used only partially in time and/or location. This paper shows the benefits of ASA, considering different methods to optimize the resources, by simulating an LTE network where a Mobile Network Operator (MNO) is allowed to use the 2300 MHz band as an ASA licensee.

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Optimization of Authorised/Licensed Shared Access resources

This study proposes a coordinated dynamic spectrum access (DSA) scheme for LTE based on cognitive radio (CR) technology, where a central entity, a Spectrum Policy Server (SPS), performs the spectrum management in a LTE multi-operator heterogeneous network (HetNet). More specifically, the scenario analyzed is based on a system deployment formed by two Mobile Network Operators (MNOs), each operating a macro cell network and a pico cell network. The spectrum allocation for macro base stations (BSs) is fixed, as it is the case in current deployments, while the spectrum for pico BSs is shared among operators and allocated dynamically. Increased throughput with high spectrum efficiency is demonstrated on this paper and simulation results for this scenario are presented.

Karl-Josef Friederichs

Papers

Vision for Beyond 4G broadband radio systems

Intermediate description of the spectrum needs and usage principles

Use of licensed shared spectrum in a radio access network where signal propagation is unknown

Optimization of Authorised/Licensed Shared Access resources

A cognitive radio based dynamic spectrum access scheme for LTE heterogeneous networks