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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

Fifth generation (5G) wireless networks face various challenges in order to support large-scale heterogeneous traffic and users, therefore new modulation and multiple access (MA) schemes are being developed to meet the changing demands. As this research space is ever increasing, it becomes more important to analyze the various approaches, therefore, in this paper we present a comprehensive overview of the most promising modulation and MA schemes for 5G networks. Unlike other surreys of 5G networks, this paper focuses on multiplexing techniques, including modulation techniques in orthogonal MA (OMA) and various types of non-OMA (NOMA) techniques. Specifically, we first introduce different types of modulation schemes, potential for OMA, and compare their performance in terms of spectral efficiency, out-of-band leakage, and bit-error rate. We then pay close attention to various types of NOMA candidates, including power-domain NOMA, code-domain NOMA, and NOMA multiplexing in multiple domains. From this exploration, we can identify the opportunities and challenges that will have the most significant impacts on modulation and MA designs for 5G networks.

Modulation and Multiple Access for 5G Networks

From the Publisher:
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Handbook of Neural Network Signal Processing

In this paper we review the waveform design of 4G (based on OFDM) and motivate the need for a redesign for 5G. Both the advent of the Internet of Things (IoT) and the move to user-centric processing are rendering OFDM unfeasible. With FBMC a potential contender has been promoted in recent years. Though FBMC is better suited than OFDM in theory, practical considerations pinpoint many issues of FBMC. Therefore, we have designed a new waveform called Universal Filtered Multi-Carrier (UFMC) collecting the advantages FBMC is promising while avoiding its drawbacks. In contrast to FBMC, UFMC applies a filtering functionality per sub-band instead of per subcarrier.

Waveform contenders for 5G — OFDM vs. FBMC vs. UFMC

Adaptive filter theory: by Simon Haykin, McMaster University, Hamilton, Ontario L8S 4LB, Canada, in: Prentice-Hall Information and System Sciences Series, published by Prentice-Hall, Englewood Cliffs, NJ 07632, U.S.A., 1986, xvii+590 pp., ISBN 0-13-004052-5 025

This paper concentrates on an efficient prototype filter design in the context of filter bank based multicarrier (FBMC) transmission. An advantage of the chosen method, frequency sampling technique, is that near perfect reconstruction prototype filters can be expressed using a closed-form representation with only a few adjustable parameters. The performance of various designs are analyzed using the offset-QAM based FBMC system. Numerical results are provided to characterize different optimization criteria in terms of frequency selectivity of resulting prototype filters and total interference level of the filter bank structure. Furthermore, it is shown what kind of performance trade-offs can be obtained by adjusting those free parameters. In this sense, the presented results offer useful information to a system designer.

Prototype filter design for filter bank based multicarrier transmission

An extension of the field of fast least-squares techniques is presented. It is shown that the adaptation gain, which is updated with a number of operations proportional to the number of transversal filter coefficients, can be used to update the coefficients of a linearly constrained adaptive filter. An algorithm that is robust to round-off errors is derived. It is general and flexible. It can handle multiple constraints and multichannel signals. Its performance is illustrated by simulations and compared with the classical LMS-based Frost (1972) algorithm.

A fast least-squares algorithm for linearly constrained adaptive filtering

An alternative scheme, named frequency spreading filter bank multicarrier (FS-FBMC), is introduced for multicarrier transmission. It is based on the FFT and closely follows the principle of OFDM, while preserving the key advantages of FBMC, namely the absence of guard time and the spectral separation of the sub-channels. It is optimal in the sense that it can provide perfect equalization of the transmission channel without the need for an additional delay and it maximizes the signal-to-noise ratio in the receiver. It generalizes the classical FFT-PPN approach, which, in fact, is a technique to remove some redundancy in the computations.

FS-FBMC: An alternative scheme for filter bank based multicarrier transmission

Future broadband radio systems have ambitious objectives in terms of performance and quality of service. Moreover, new network topologies are likely to be introduced. Therefore, the physical layer has to evolve to meet the new requirements. With this in mind, the filter bank multicarrier (FBMC) technique is proposed as an enhancement to the present OFDM technique. After a brief presentation of the FBMC principle, the adaptation to the radio context is described. Then, the main features which impact radio networks are reviewed with emphasis on the potential benefits of the evolution. The paper provides an overview of the work carried out in the European research project EC-FP7-Phydyas (physical layer for dynamic access and cognitive radio).

Maurice Bellanger

Papers

Adaptive filter theory: by Simon Haykin, McMaster University, Hamilton, Ontario L8S 4LB, Canada, in: Prentice-Hall Information and System Sciences Series, published by Prentice-Hall, Englewood Cliffs, NJ 07632, U.S.A., 1986, xvii+590 pp., ISBN 0-13-004052-5 025

Prototype filter design for filter bank based multicarrier transmission

A fast least-squares algorithm for linearly constrained adaptive filtering

FS-FBMC: An alternative scheme for filter bank based multicarrier transmission

Physical layer for future broadband radio systems