Problems of implementing 5 G networks in transport systems Natalia Kononovaa, Dmitry Vinokurskya, Mihail Kononova and Elena Krahotkinaa a Federal State Autonomous Educational Institution of Higher Education North-Caucasus Federal University, Stavropol, 355009, Russia Abstract This article provides an overview of the challenges to transport networks introduced by 5G and provides a first analysis of the key challenges to 5G transport in terms of capacity, flexibility and costs. Different use cases are discussed as well as technology options and control plane concepts. The three main transport challenges are identified: huge aggregated traffic volumes, on-demand provisioning of very high capacity in specific geographical locations, need for fast reconfigurability of the transport resources. Keywords Wireless access, transport systems, virtualization, 5G generation networks 1. Introduction - 1000 times faster wireless zone throughput and more versatile service options; In the coming era of the massive 5G Internet of - сreation of a secure, reliable Internet with "zero perceived" downtime for the provision of Things (mloT), we are expected to have 1000 services; devices connected to each person, and these - 100 times higher user data transfer rate; devices will be components of the «5G operating - 10x the battery life for massive IoT devices; system» for our smart cities, smart homes, smart - 5 times decrease in end-to-end delay; transportation, smart healthcare, and more. - Diverse requirements such as higher speeds 5G networks are expected to serve about 7 for enhanced mobile broadband (eMBB), ultra- trillion diverse connected sites. Compared to the reliable and low-cost communications (URLLC), and higher density and long battery life for previous generation of mobile communications, the machine-type mass communications (mMTC) [2]. 5G infrastructure we are building now should reach Based on the challenges for wireless access the luggage, people decided to apply them in practice main transport challenges are defined. Possible this scale while still delivering the following solutions addressing these challenges are also metrics: presented and discussed. We find that the transport infrastructure for future 5G deployment needs to both accommodate high traffic volumes over Models and Methods for Researching Information Systems specific geographical areas and provide transport in Transport, Dec. 11-12, St. Petersburg, Russia resources in a flexible manner. This quality will be EMAIL: knv_fm@mail.ru (A. 1); dlvinokursky@gmail.com (A. 2); mikhail_kononov_2014@mail.ru (A. 3); elena-stv@ya.ru (A. 4) indispensable for operational purposes but also to ©️ 2020 Copyright for this paper by its authors. Use permitted under Creative Commons License Attribution 4.0 International (CC BY 4.0). limit as much as possible deployment costs without CEUR Workshop Proceedings (CEUR-WS.org) 47 48 compromising the quality of experience of the actuators with stringent energy efficiency and various provisioned services. transmission constraints [4]. In order to understand the 5G transport A 5G transport network can be divided in two challenges one must understand how 5G may different segments, i.e., small cell transport and evolve the radio access segment. Among the metro (aggregation). The small cell transport various initiatives that are looking into 5G, the EU segment aggregates the traffic to (from the wireless project METIS defines 5G in terms of scenarios small cells towards the metro) aggregation which the next generation wireless access networks segment. Different solutions in terms of technology will have to support. A total of five future scenarios (optics, wireless) and topology (tree, ring, mesh) have been defined, namely amazingly fast, great are possible [5] depending on the specific wireless service in a crowd, ubiquitous things access scenario. The metro (aggregation) segment, communicating, super real time and reliable on the other hand, connects different site types connections, and best experience follows you. Each (macro and/or small cells) among themselves and of these scenarios introduces a challenge. Three of to the core network, the latter via the service edge these challenges are more traditional in the sense (service node for the interconnection among that they are related to continued enhancement of different network domains). For the metro user experience and supporting increasing traffic (aggregation) segment one promising solution is volumes and mobility. Two emerging challenges, represented by a dense-wavelength-division very low latency and very low energy, cost and multiplexing (DWDM) - centric network [6]. In massive number of devices, are associated with the such a network, packet aggregation takes place at application of wireless communications to new the edges of the network (at the small/macro cells areas. Future applications may be associated with sites and at the service edge), while at the center one or several of these scenarios imposing different (between access and metro rings) switching is done challenges to the network. In METIS twelve completely in the optical domain thanks to active specific test cases were defined and mapped onto optical elements such as wavelength selective the five scenarios. The selected test cases switches (WSSs) and reconfigurable optical add- essentially sample the space of future applications. drop multiplexers (ROADMs) [7]. It has already Once technical enablers that fulfill the been demonstrated that DWDM-centric solutions requirements for these test cases are defined, it is have the potential to offer high capacity (in the expected that other applications subject to the same order of tens to hundreds of Gbps) and lower fundamental challenges, will successfully be energy consumption than their packet-centric supported. As a consequence, defining technical counterparts (with packet aggregation at the center enablers for the 5G test cases means also defining of the network) [8]. For this reason the DWDM- technical solutions to the 5G challenges. centric metro/aggregation concept may represent a Today, 4G offers consumer data rates in megabytes good candidate for future 5G transport networks. order, latency in milliseconds order and device For the dedicated small cell transport segment it is density for approximately 2000 connected devices not possible to define a single best candidate technology because of the variety of the small cell per square kilometre worldwide, which has deployments which are test-case dependent. The supported the introduction of Internet of Things main options can be categorized in copper, fiber (IoT). Despite such capabilities and due to an and wireless-based technologies [9]. Wireless exponential increase of the demand and the new based solutions are attractive where cost of mobile telecommunication innovations, 4G would deploying wired transport infrastructure is be replaced with the next generation (5G) by the prohibitively high. Copper-based options are able start of the next decade, as stated in [3]. to offer rates in the order of a few Gbps over relatively short distances and therefore can be The 5G era will bring network and service preferred in the areas where there is a large capabilities not previously available. It will ensure installed base of copper that can be reused. Optical continuity, higher data rate, lower latency, massive transmission technologies are able to provide high simultaneous connections and ubiquity of network data rates over long distances in an energy-efficient across the world even in challenging situations for way. Fiber-based solutions are seen as a good and current 4G such as high mobility and in very dense long term candidate for 5G small cells transport or sparsely populated areas. In addition, 5G will be networks [10]. The table is organized in terms of: a key enabler for a real IoT, providing a platform transport services that can be supported and to connect a massive number of sensors and technology maturity. 48 49 The graph shown in Figure 1 shows that the dedicated small cells transport network and transport solutions used in modern networks, in provides the overall transport controller with an terms of their throughput, correspond to the level abstract and simplified view of this network segment. The overall transport controller is in of development of transmission technologies at the charge of managing all the transport resources and end of the 80s. last century. providing connectivity services to the other controllers. The controllers interact via the orchestrator, which possesses an abstract and simplified view of all the resources and performs end-to-end provisioning and optimization. Long-term economic prospects show that prosperity among urbanites will also grow, and therefore the demand for public and individual transport will increase. Consequently, car ownership is likely to continue its rapid rise. China alone gained an additional 17 million new cars in 2014, taking ownership to a Figure 1. Growth of channel capacity of transport record 154 million. As an obvious consequence, road traffic congestion can be expected to become networks. more intricate, further exacerbating already high For some test cases, like the open air festival, negative environmental, social and economic optical based small cell transport may not be impacts. preferable, due to high deployment costs. In these Information and communications technology can cases, wireless-based solutions may represent a mitigate these impacts. Applications of information better alternative, mainly because they are usually and communications technology in the transport easier, faster, and cheaper to deploy. Modern sector, have led to the development of so-called wireless transport technologies are able to provide “intelligent transport systems” (ITS). ITS improve very high capacities over short and medium traffic efficiency and safety, with positive distances, thanks to the introduction of new outcomes for sustainable development. Though transmission paradigms, such as MIMO, and the driven initially mostly by the more advanced opening of new spectrum ranges. countries (United States, Japan, and some The use of dynamic resource sharing and NFV European countries), ITS are increasingly being puts requirements on the control plane. A software- used by developing countries, which are defined networking (SDN) [11] based control plane confronted with urgent needs to improve traffic in with programmable control of network resources rapidly growing cities. ITS are also becoming and end-to-end orchestration could provide a increasingly tailored to the specific needs of framework for such a scenario. It could enable developing countries, and recent evolutions in dynamic optimization of the use of transport information and communications technology such network resources and provide a framework for as the analytical power offered by open and big interaction with other controllers [12]. On the other data further raise the prospects for ITS to be hand, the design and implementation of such a designed within developing countries in response complex control plane introduces several to their specific needs. challenges. A main challenge is the definition of an Even though 5G technologies have not yet hit the orchestration entity able to keep track of the market, there is a great expectation of all the availability of different type of resources and possible applications that will arise thanks to their perform end-to-end optimization. A centralized qualities, in many cases improving the services orchestration entity leads also to scalability issues, presented by the previous networks but in other which could be addressed through the adoption of cases bringing new and more innovative services a multilayer control architecture and resources never seen before. abstraction models. Different multi-layer SDN- The emerging concepts of the Internet of Things, based control architectures are possible depending Smart Cities, and Intelligent Transportation on how the controllers of different segments are Systems are three of the main paradigms that will expected to interact. The dedicated small cells be promoted with the appearance of 5G transport controller manages the resources in the technologies. At the moment it has been possible to reach a basic level of services based on IoT due to 49 50 the limitations of 4G technologies, but thanks to the - virtual reality (VR) office, possibilities of network availability anywhere, at - open air festival. any time with a higher data rate, we could finally The analysis highlighted that the use of a common have a real connectivity among a dense population DWDM centric access metro network combined of mobile devices. with a dedicated small cell transport can be an The particular case of Intelligent Transport where efficient choice for the future 5G transport. In vehicles are seen as intelligent mobile devices addition, a SDN-based transport controller, able to capable of connecting to the network to share efficiently perform dynamic resource sharing and information of their environment is a topic with a NFV, helps in achieving high resource utilization great impact within the intelligent planning of and in reducing deployment costs. 5G mobile resources into a Smart City. In fact, for communications is seen as the enabler for the governments and modern economic development networked society where connectivity will be in general is vital to improve the transportation available anywhere and anytime to anyone and management system and promoting sustainability. anything. The details of 5G are the subject to The optimization of the transportation system will ongoing research and debate, mostly focused on result in a reduction of the environmental impact understanding radio technologies that can enable and energy saving, as well as time and money. the 5G vision. Despite all the great advantages that show the Let's define a list of potential problems of the coming of the 5G era and of the IoT, there are still transport network for 5G and label each of them as problems to face in the technological field. There serious, moderate, or minor (ranking in descending are also social and ethical problems related to the order according to the percentage). inclusion of new services that will not be easy for 1. Major challenge: the population to assimilate, as it is the case of self- - meeting ultra-low latency requirements – 57% driving vehicles inside the city and possible undue - costs of extending wireline connectivity to new access to personal information of the users due to cell sites (densification)- 40% the fact that all our data will be shared in the cloud. - achieving RAN capacity requirements – 39% Such problems are related to security, but seen - meeting timing and synchronization from the side of avoiding fatal accidents in one case requirements – 36% and in the other hand seen as protection of private - costs of upgrading existing RANs – 35% information. - network automation – 31% - implementing network slicing in the transport 2. Conclusion network – 28% - implementing cloud/virtualization of BBU This article provides an overview of the challenges functions – 21% to transport networks introduced by 5G and - compatibility of new and legacy protocols (i.e., provides a first analysis of the key challenges to 5G MPLS/segment routing/EVPN) – 19% transport in terms of capacity, flexibility and costs. 2. Moderate challenge: Different use cases are discussed as well as - meeting timing and synchronization technology options and control plane concepts. The requirements – 51% three main transport challenges are identified: - network automation – 51% - huge aggregated traffic volumes, - implementing network slicing in the ransport - on-demand provisioning of very high capacity network - 51% in specific geographical locations, - achieving RAN capacity requirements – 48% - need for fast reconfigurability of the transport - compatibility of new and legacy protocols (i.e., resources. MPLS/segment routing/EVPN) – 44% Two approaches for designing and dimensioning a - implementing cloud/virtualization of BBU future 5G transport network have been considered. functions – 43% One is based on over-provisioning of transport - costs of extending wireline connectivity to new resources while the second is based on dynamic cell sites (densification) – 37% resource sharing and network function - costs of upgrading existing RANs – 37% virtualization (NFV) aided by a software defined - meeting ultra-low latency requirements – 33% network (SDN)-based controller. These two 3. Minor challenge: approaches have been compared in two specific 5G - compatibility of new and legacy protocols (i.e., test cases: MPLS/segment routing/EVPN) – 32% 50 51 - implementing cloud/virtualization of BBU [3] Alabady, S.; Al-Turjman, F.; Din, S. A Novel functions – 29% Security Model for Cooperative Virtual - costs of upgrading existing RANs – 23% Networks in the IoT Era. Int. J. 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