On the Road to 6G: Visions, Requirements, Key Technologies and Testbeds

Fifth generation (5G) mobile communication systems have entered the stage of commercial development, providing users with new services and improved user experiences as well as offering a host of novel opportunities to various industries. However, 5G still faces many challenges. To address these challenges, international industrial, academic, and standards organizations have commenced research on sixth generation (6G) wireless communication systems. A series of white papers and survey papers have been published, which aim to define 6G in terms of requirements, application scenarios, key technologies, etc. Although ITU-R has been working on the 6G vision and it is expected to reach a consensus on what 6G will be by mid-2023, the related global discussions are still wide open and the existing literature has identified numerous open issues. This paper first provides a comprehensive portrayal of the 6G vision, technical requirements, and application scenarios, covering the current common understanding of 6G. Then, a critical appraisal of the 6G network architecture and key technologies is presented. Furthermore, existing testbeds and advanced 6G verification platforms are detailed for the first time. In addition, future research directions and open challenges are identified for stimulating the on-going global debate. Finally, lessons learned to date concerning 6G networks are discussed

High Capacity Fiber-Connected Wireless MIMO Communication

There will be more and more users while beyond-5G (B5G) and 6G bring more wireless applications. Current cellular communication networks assign specific serving boundaries for each radio, which becomes a limitation when too many users work with one radio simultaneously. By physically distributing radios. user’s service can be more uniform. Radio-over-fiber is a promising enabling technology for distributed antenna systems.To have several tens of Gbit/s data rate, we need to apply millimeter-wave (mm-wave) frequency band in radio-over-fiber (RoF). However, mm-wave signals have weak penetration and high propagation loss. Hence, beamforming and/or multiple-input-multiple-output (MIMO) technology become necessary for mm-wave RoF to overcome those drawbacks.This thesis introduces an automatic distributed MIMO (D-MIMO) testbed with a statistical MIMO capacity analysis for an indoor use case. Raytracing-based simulations also predicts the indoor case to make a comparison. The statistical MIMO capacity analysis shows that D-MIMO has a higher and more uniform capacity than co-located MIMO (C-MIMO) in measurements and simulations.Next, a mm-wave sigma-delta-over-fiber (SDoF) link architecture is proposed for MIMO applications. In the implementation of this link, a QSFP28 fiber link connects a central unit with a remote radio unit with four bandpass sigma-delta-modulation (BPSDM) bitstreams. The remote radio unit generates four mm-wave signals from four BPSDM signals and feeds a linear array antenna. The measurement characterizes the remote radio head at each stage and concludes that this proposed link can reach 800 Msym/s data rate with -0.5 dBm output bandpower.Furthermore, the proposed link is demonstrated with digital beamforming and multi-user MIMO (MU-MIMO) functionalities. The digital beamforming function reaches 700 Msym/s with -25 dB error vector magnitude (EVM) results by improving the received bandpower in comparison to (single-input-single-output) SISO results. The MU-MIMO function serves two independent users at 500 Msym/s symbol rate and satisfies 3GPP requirements at 1 m over-the-air distance.In conclusion, this thesis proves that D-MIMO has a higher and more uniform capacity than C-MIMO by statistical analysis from measurements and simulations. The proposed novel mm-wave SDoF link can pave the way for future D-MIMO applications

5G-PPP Technology Board:Delivery of 5G Services Indoors - the wireless wire challenge and solutions

The 5G Public Private Partnership (5G PPP) has focused its research and innovation activities mainly on outdoor use cases and supporting the user and its applications while on the move. However, many use cases inherently apply in indoor environments whereas their requirements are not always properly reflected by the requirements eminent for outdoor applications. The best example for indoor applications can be found is the Industry 4.0 vertical, in which most described use cases are occurring in a manufacturing hall. Other environments exhibit similar characteristics such as commercial spaces in offices, shopping malls and commercial buildings. We can find further similar environments in the media & entertainment sector, culture sector with museums and the transportation sector with metro tunnels. Finally in the residential space we can observe a strong trend for wireless connectivity of appliances and devices in the home. Some of these spaces are exhibiting very high requirements among others in terms of device density, high-accuracy localisation, reliability, latency, time sensitivity, coverage and service continuity. The delivery of 5G services to these spaces has to consider the specificities of the indoor environments, in which the radio propagation characteristics are different and in the case of deep indoor scenarios, external radio signals cannot penetrate building construction materials. Furthermore, these spaces are usually “polluted” by existing wireless technologies, causing a multitude of interreference issues with 5G radio technologies. Nevertheless, there exist cases in which the co-existence of 5G new radio and other radio technologies may be sensible, such as for offloading local traffic. In any case the deployment of networks indoors is advised to consider and be planned along existing infrastructure, like powerlines and available shafts for other utilities. Finally indoor environments expose administrative cross-domain issues, and in some cases so called non-public networks, foreseen by 3GPP, could be an attractive deployment model for the owner/tenant of a private space and for the mobile network operators serving the area. Technology-wise there exist a number of solutions for indoor RAN deployment, ranging from small cell architectures, optical wireless/visual light communication, and THz communication utilising reconfigurable intelligent surfaces. For service delivery the concept of multi-access edge computing is well tailored to host virtual network functions needed in the indoor environment, including but not limited to functions supporting localisation, security, load balancing, video optimisation and multi-source streaming. Measurements of key performance indicators in indoor environments indicate that with proper planning and consideration of the environment characteristics, available solutions can deliver on the expectations. Measurements have been conducted regarding throughput and reliability in the mmWave and optical wireless communication cases, electric and magnetic field measurements, round trip latency measurements, as well as high-accuracy positioning in laboratory environment. Overall, the results so far are encouraging and indicate that 5G and beyond networks must advance further in order to meet the demands of future emerging intelligent automation systems in the next 10 years. Highly advanced industrial environments present challenges for 5G specifications, spanning congestion, interference, security and safety concerns, high power consumption, restricted propagation and poor location accuracy within the radio and core backbone communication networks for the massive IoT use cases, especially inside buildings. 6G and beyond 5G deployments for industrial networks will be increasingly denser, heterogeneous and dynamic, posing stricter performance requirements on the network. The large volume of data generated by future connected devices will put a strain on networks. It is therefore fundamental to discriminate the value of information to maximize the utility for the end users with limited network resources

Contextual Beamforming: Exploiting Location and AI for Enhanced Wireless Telecommunication Performance

The pervasive nature of wireless telecommunication has made it the foundation for mainstream technologies like automation, smart vehicles, virtual reality, and unmanned aerial vehicles. As these technologies experience widespread adoption in our daily lives, ensuring the reliable performance of cellular networks in mobile scenarios has become a paramount challenge. Beamforming, an integral component of modern mobile networks, enables spatial selectivity and improves network quality. However, many beamforming techniques are iterative, introducing unwanted latency to the system. In recent times, there has been a growing interest in leveraging mobile users' location information to expedite beamforming processes. This paper explores the concept of contextual beamforming, discussing its advantages, disadvantages and implications. Notably, the study presents an impressive 53% improvement in signal-to-noise ratio (SNR) by implementing the adaptive beamforming (MRT) algorithm compared to scenarios without beamforming. It further elucidates how MRT contributes to contextual beamforming. The importance of localization in implementing contextual beamforming is also examined. Additionally, the paper delves into the use of artificial intelligence schemes, including machine learning and deep learning, in implementing contextual beamforming techniques that leverage user location information. Based on the comprehensive review, the results suggest that the combination of MRT and Zero forcing (ZF) techniques, alongside deep neural networks (DNN) employing Bayesian Optimization (BO), represents the most promising approach for contextual beamforming. Furthermore, the study discusses the future potential of programmable switches, such as Tofino, in enabling location-aware beamforming

6G Radio Testbeds: Requirements, Trends, and Approaches

The proof of the pudding is in the eating - that is why 6G testbeds are essential in the progress towards the next generation of wireless networks. Theoretical research towards 6G wireless networks is proposing advanced technologies to serve new applications and drastically improve the energy performance of the network. Testbeds are indispensable to validate these new technologies under more realistic conditions. This paper clarifies the requirements for 6G radio testbeds, reveals trends, and introduces approaches towards their development

Design and implementation of a positioning service in the context of smart cities

In recent decades, cities have become the global hubs of commerce, culture, science and society, being also the largest consumers of energy and the largest carbon emitters. With the objective of solving this problem, sustainable cities or "Smart Cities" are one of the objectives to be fulfilled in the 2030 Agenda. With this objective in mind and in the context of the project "Navigation and GNSS in Smart Cities -Testbed Concept Definition" (HANSEL), the student intends to design and develop a service in charge of sensor positioning based on GNSS and Cellular technologies for the subsequent treatment of the information generated for various purposes, such as the detection and location of sources of interference or GNSS and Cellular hybridization, obtaining hybrid positions, more precise than those of each system separately. This system or service is intended to be accessible to the general public via Internet (as a Software as a Service orSaaS), and takes advantage of the all the features cloud computing has to offer, both at performance and energy consumption level.En les últimes dècades, les ciutats s'han convertit en els nuclis mundials de comerç, cultura, ciència i societat, sent també les majors consumidores d'energia i les més grans emissores de carboni. Amb l'objectiu de solucionar aquesta problemàtica, les ciutats sostenibles o "SmartCities" són un dels objectius a complir en l'Agenda 2030. Amb aquest objectiu en ment i en el context del projecte "Navigation and GNSS in Smart Cities - Testbed Concept Definition"(HANSEL), l'estudiant pretén dissenyar i desenvolupar un servei a càrrec del posicionament de sensors basats en tecnologies GNSS i cel·lular per al posterior tractament de la informació generada per a diverses finalitats, com la detecció i localització de fonts d'interferència o la hibridació GNSS i cel·lular, donant lloc a posicions híbrides, més precises que les de cada sistema per separat. Aquest servei pretén ser accessible mitjançant Internet al públic general (com un Software com a servei o SaaS), i aprofita els avantatges que la computació en el núvol és capaç d'oferir tant a nivell de prestacions com a nivell d'estalvi d'energia respecte als dispositius de navegació actuals.En las últimas décadas, las ciudades se han convertido en los núcleos mundiales de comercio, cultura, ciencia y sociedad, siendo también las mayores consumidoras de energía y las más grandes emisoras de carbono. Con el objetivo de solucionar esta problemática, las ciudades sostenibles o "Smart Cities" son uno de los objetivos a cumplir en la Agenda 2030. Con este objetivo en mente y en el contexto del proyecto "Navigation and GNSS in Smart Cities - Testbed Concept Definition" (HANSEL), el estudiante pretende diseñar y desarrollar un servicio a cargo del posicionamiento de sensores basados en tecnologías GNSS y celular para el posterior tratamiento de la información generada para diversos fines, como la detección y localización de fuentes de interferencia o la hibridación GNSS y celular, dando lugar a posiciones híbridas, más precisas que las de cada sistema por separado. Dicho servicio pretende ser accesible mediante Internet al público general (como un Software como servicio o SaaS), y aprovecha las ventajas que la computación en la nube es capaz de ofrecer tanto a nivel de prestaciones como a nivel de ahorro de energía con respecto a los dispositivos de navegación actuales