5G will have to cope with a high degree of heterogeneity in terms of services and requirements. Among these latter, the flexible and efficient use of non-contiguous unused spectrum for different network deployment scenarios is considered a key challenge for 5G systems. To maximize spectrum efficiency, the 5G air interface technology will also need to be flexible and capable of mapping various services to the best suitable combinations of frequency and radio resources. In this work, we propose a comparison of several 5G waveform candidates (OFDM, UFMC, FBMC and GFDM) under a common framework. We assess spectral efficiency, power spectral density, peak-to-average power ratio and robustness to asynchronous multi-user uplink transmission. Moreover, we evaluate and compare the complexity of the different waveforms. In addition to the complexity analysis, in this work, we also demonstrate the suitability of FBMC for specific 5G use cases via two experimental implementations. The benefits of these new waveforms for the foreseen 5G use cases are clearly highlighted on representative criteria and experiments.

This paper presents how to apply order reduction in wide-band digital predistortion (DPD) linearizers using the principal component analysis (PCA) technique. This method is tested in a wireless backhauling transmitter where four 28 MHz adjacent subcarrier transmission of M-QAM signals are considered. The DPD has to counteract not only the PA nonlinear behavior, but also its dynamics. This may results critical when considering wideband signals since the number of coefficients required to model memory effects can grow dramatically. By applying the PCA technique, the number of essential parameters can be significantly reduced. In addition, a strategy to minimize the computational cost of finding the optimal coefficients is also presented. A test-bed for evaluating the DPD linearization performance of the RF subsystem when PCA is applied was deployed and experimental results are presented in this paper.

The Internet of Things (IoT) will facilitate a wide variety of applications in different domains, such as smart cities, smart grids, industrial automation (Industry 4.0), smart driving, assistance of the elderly, and home automation. Billions of heterogeneous smart devices with different application requirements will be connected to the networks and will generate huge aggregated volumes of data that will be processed in distributed cloud infrastructures. On the other hand, there is also a general trend to deploy functions as software (SW) instances in cloud infrastructures [e.g., network function virtualization (NFV) or mobile edge computing (MEC)]. Thus, the next generation of mobile networks, the fifth-generation (5G), will need not only to develop new radio interfaces or waveforms to cope with the expected traffic growth but also to integrate heterogeneous networks from end to end (E2E) with distributed cloud resources to deliver E2E IoT and mobile services. This article presents the E2E 5G platform that is being developed by the Centre Tecnol?gic de Telecomunicacions de Catalunya (CTTC), the first known platform capable of reproducing such an ambitious scenario.

The recent advancements in cellular Vehicle-to-everything (C-V2X) and edge computing paradigms foster novel use cases for connected and automated vehicles that come with strict performance requirements. These guarantees can be provided by network slicing, which is currently enabled by the virtualization and cloudification of mobile networks, following the 5G/6G core service-based approach and the cloud-native Open Radio Access Network (O-RAN) principles. However, a significant challenge arises when considering the movement of end users: ensuring network slice continuity as they transition between different network operators. In this paper, we introduce a novel cloud-native orchestration framework for network slice federation that incorporates well-defined interfaces to exchange federated service and slice resource templates among operators. The proposed framework is fully compliant with i) standardized slice service models, and ii) GSMA efforts that are building the fundamental aspects for Edge Federation to allow the sharing of network resources across mobile operators. To validate our approach, we have designed and deployed a cloud-native federated 5G experimental platform. An extensive series of experiments have been carried out, revealing that the federation implementation directly influences federation time, and the operator's slice deployment strategy significantly impacts both infrastructure and end user performance.

Filter bank multi-carrier (FBMC) is a candidate modulation scheme for 5G cellular mobile broadband networks. A specific domain where FBMC offers a clear advantage over other multicarrier solutions is the efficient occupancy of underutilized and fragmented spectrum. This is due to the rich spectral containment of the FBMC technology, which guarantees superior interference protection to the primary coexisting transmissions. These features of FBMC could play an important role in the economic delivery of 5G services in licensed and unlicensed bands. This article focuses on the public safety domain where existing professional mobile radio (PMR) users plan to add broadband services at the 400 MHz band, aiming to occupy the spectral holes left by current narrowband transmissions. In this respect an agile SDR broadband downlink FBMC system, aimed at exploiting unused licensed PMR spectrum, was developed and experimentally validated. The FBMC frame structure shared key similarities with the LTE specification. Two different SDR design methodologies were used to build the real-time baseband prototype. The level of interference protection offered by a broadband FBMC system to a coexisting primary narrowband PMR transmission was practically demonstrated and compared to that of an equivalent LTE system. This was made feasible by evaluating the performance of a PMR terminal under different mobile channels and FBMC waveform configurations. The applicability of this work to other 5G spectrum cohabitation scenarios is discussed. Finally, the article highlights the need to extend the SDR design paradigm in order to tackle the challenges of real-time baseband processing in 5G broadband cellular systems.