Description of the device and functioning of the fifth generation network deployed on the basis of the fourth generation

The fourth generation cellular networks can be built on the basis of two technologies - LTE (Long Term Evolution) and WiMAX (Worldwide Interoperability for Microwave Access). Both of these technologies are similar, but have different developers and appearance times. WiMAX, based on the IEEE 802.16 standard (developed by the Institute of Electrical and Electronics Engineers, Institute of Electrical and Electronics Engineers) uses OFDM technology to transmit data in both directions (for uploading and downloading), which leads to high peak factors, i.e., large coefficients loads on the power supplies of the final equipment (in other words, the phone’s battery will wear out and discharge faster when using OFDM for outgoing speed). Unlike WiMAX, Long Term Evolution technology uses SC-FDMA technology for outgoing speed,

LTE technology was developed by the 3GPP (The 3rd Generation Partnership Project) forum, which is designed to solve the problems of using GSM and CDMA2000 (UMTS) technologies, which are respectively the technologies of the second and third generations of cellular communications. In Kazakhstan, for the operation of cellular networks, they first used GSM technology (EDGE), then CDMA2000, so the introduction of cellular communications based on LTE Advanced (LTE Realize 12) technology was advisable. Accordingly, fifth-generation networks in Kazakhstan should be deployed based on LTE Advanced networks.

The fifth generation (5th Generation) of cellular communications should solve issues related not to improving the quality of voice transmission, but to the problem of Internet access and increasing the speed of data transfer. Currently (February 2019), 5G standards are not developed, but by December 2019, the International Telecommunication Union will introduce the IMT-2020 standard, which describes the technologies for building and accessing the network. Since the technologies of all previous generations of communication were based on previous ones, that is, to use the services of the 3G network, it was not necessary to buy a new device, and to use LTE Advanced it was only necessary to replace the SIM card in an outdated phone, the author assumes that the first release of the IMT standard 2020 will be based on LTE Advanced technology with non-orthogonal frequency diversity channels, Non-OFDM.

Despite the architecture similar to LTE Advanced, 5G networks must use a wider frequency spectrum to increase speed, and since fourth-generation networks occupy a decimeter or centimeter frequency range (LTE Advanced operates in the range from 2500 to 2690 MHz when loaded, for example, the domestic operator “ Altel ”uses a frequency band of 1800 MHz.), Then for the fifth generation networks, most likely, frequencies in the millimeter range (60 - 100 GHz) will be allocated. Accordingly, to use the millimeter range, it will be necessary not only to increase the number of base stations in our country, but also to increase the power of the power supply units of these base stations.

Another hallmark of 5G networks will be the introduction of cloud technology. The use of "clouds" is necessary to relieve the load on the base stations, it is assumed that they will only transmit the signal without processing, as happens in 4G networks (in LTE networks, signal processing occurs on the side of the end device and base station, mobility management unit, MME , transmits only service information, not user traffic, it is the base station that is engaged in its transmission, therefore, with an increase in the number of connected devices, they will not be able to cope with the load).

Since the fifth generation networks will operate on the basis of the fourth generation, first you need to explain how the LTE Advanced network functions, then derive assumptions about the architectural differences of the fifth generation networks.

An LTE network consists of two systems - a core network, System Architecture Evolution or Evolved Packet Core, consisting of Mobility Management Entity blocks, User Plane Entity blocks, service and packet gateways, and a radio access network (evolved UMTS Terrestrial radio access network, E-UTRAN) consisting of base stations only. In the previous generation of communication, the radio access network architecture included a radio network controller, Radio Network Controller, whose functions included the process of establishing and interrupting subscriber connections, the process of handover (transferring a subscriber from one base station to another), encrypting user data, determining the level of quality control. In LTE networks, all these functions are assigned to base stations.

All elements of LTE networks are interconnected using interfaces (an interface is a set of standardized connections connecting various equipment, for example, the interface is called the connecting cables of the computer motherboard and peripheral devices - RS-232, USB, HDMI). The interface connecting the base stations is called X2 and is responsible for keeping the subscriber in the network during the transition from one base station to another. The base stations are connected to the mobility management unit using the S1 interface; the interface itself is divided into two types: S1-C, transmitting service information for the base station through the Serving GW gateway; S1-U, transmitting user information through the Packet Data Network GW packet gateway. Also, in addition to S1, there are other interfaces, such as: S2 (for connecting to networks in which the 3GPP forum was not a developer), S3 (connects the packet network node for subscribers of second and third generation networks and MME, is responsible for the transfer of service data between LTE and previous generations), S4 (connects the SAE core network and the previous generation packet network node SGSN, Serving GPRS Support Node), S5 (connects the core network and Packet Data Network GW packet gateway), S6 (connects the mobility management unit and the subscriber data server, is responsible for authentication in the LTE network). The totality of the network equipment of the core network, the radio access network and the connecting interfaces is the physical structure of the LTE, LTE Advanced networks. S4 (to connect the SAE core network and the previous generation SGSN packet network node, Serving GPRS Support Node), S5 (connects the core network and Packet Data Network GW packet gateway), S6 (connects the mobility management unit and the subscriber data server, is responsible for authentication in LTE network). The totality of the network equipment of the core network, the radio access network and the connecting interfaces is the physical structure of the LTE, LTE Advanced networks. S4 (to connect the SAE core network and the previous generation SGSN packet network node, Serving GPRS Support Node), S5 (connects the core network and Packet Data Network GW packet gateway), S6 (connects the mobility management unit and the subscriber data server, is responsible for authentication in LTE network). The totality of the network equipment of the core network, the radio access network and the connecting interfaces is the physical structure of the LTE, LTE Advanced networks.

Logically, the LTE network structure is divided into two parts: a radio access layer, Access Stratum and a non-access layer, Non-Access Stratum. The radio access layer includes all the equipment of the radio access network and the basic packet network; the layer without access includes methods for controlling (or managing) mobility, EMM, EPC Mobility Management.

Networks based on LTE Advanced provide access to high-quality network services - calls, high speed of downloading multimedia data, free use (excluding traffic) of some applications (mainly messengers). Unfortunately, due to the large number of devices and the improvement in the quality (and therefore size) of multimedia information, LTE networks will soon be unable to cope with the heavy load. In particular, the decimetric frequency spectrum used by LTE will not be able to provide access to resources with the necessary quality level (Qos), and then the device may simply disconnect from the network (base station refuses to serve a cell phone).

It is in order to prevent bandwidth saturation and in the future to release the decimeter spectrum for devices that consume few resources, by 2025 in Europe they plan to switch to the introduction of fifth generation networks (5G). Each generation of cellular communications should be different from the other: the first from the second - the transition from analog to digital modulation modes; the second from the third - the advent of additional services, such as high-speed Internet access; the fourth from the third - the transition from channel switching (distribution of incoming data) to packet and the implementation of IP-addressing, as in wired networks. The fifth generation from the fourth should differ in two parameters: the used frequency of the spectrum, that is, the transition to ultrashort waves, as well as the removal of load from base stations by transferring their functions to virtual machines. The inclusion of virtualization and cloud technology in the 5G architecture means more flexible and faster configuration, as well as cheaper deployment, since there can be many virtual machines on one physical machine. By flexible settings, the author understands the creation of individual conditions for using communication services: personal tariff plans that are tailored to the needs of each subscriber; control the amount of data consumed by all applications.

So, according to the specification 3GPP TS 38.300 version 15.3. 1 Release 15, the general device of the fifth generation networks is based on New Radio technology and will be divided into two parts, like the previous generation: 5GC (Core Network) i.e. the core network and NG-RAN (Next Generation Radio Access Network), then there is a next generation radio access network. The core network should consist of two main devices that separate utility and user functions. These devices are called “functions”: AMF (Access and Mobility Management Function), a function responsible for providing access and controlling the maintenance of a network signal when moving a subscriber; UPF (User Plane Function), responsible for the transmission of user traffic.

Additionally, other “functions” are included in the network architecture: SMF (Session Management function), a session management function, distributes IP addresses for user devices, manages and monitors traffic passing through the user plane function, selects UPF to move traffic to its destination; AUSF (Authentication Server Function), user device authentication server function; UDM (Unified Data Function), is a repository of registration data, security information and various subscriptions of the subscriber; PCF (Policy Control Function), a policy management function that controls a single network behavior policy and the behavior policy of each network plane (user and service); AF (Application Function), an application function that queries the session management function,

The radio access network consists of two types of base stations: gNBs operating in the fifth generation network and ng-eNBs operating in the fourth (E-UTRAN) or previous generation network. Both types of base stations must be connected by the Xn interface, and the connection of base stations with function blocks by the NG interface. As with LTE networks, the NG interface is different for devices that communicate with each other. In total, the specification of 3GPP TR 23.799, released in December 2016, defines 15 types of NG interfaces, with numbers from 1 to 15. It is not possible to describe all 15 types of communication systems in the article, so the author will only give five of them. So, NG1 is a "reference point" between the user device and AMF, NG2 - connects the base station with AMF; the base station is also connected via the NG3 interface to the user plane function, which, in turn, is connected via the NG4 interface to the session management function, and Internet access and operator services are provided through the NG6 interface. The AF application function is connected to the session management function via the NG5 interface.

Concepts such as user and control planes have been transferred from LTE networks in the 5G network, therefore NG interfaces associated with the user, like LTE, denote NG-U and, accordingly, NG-C for the control plane, therefore protocol levels (Stacks) of interfaces are also divided only into user and service. User plane interfaces connect the base station to the UPF, and control plane interfaces (NG-C) connect to the AMF. It should be noted here that NG-U provides non-guaranteed delivery (when the user device sends a protocol data element (PDU) and does not wait for a delivery report in response; guaranteed delivery is a confirmation in the form of a report that the data element is received), which significantly saves time data transmission.

The Xn and NG interfaces must have open specifications available for all manufacturers to interact with various base stations. It should be noted here that some groups of scientists working on the development of 5G requirements and standards, in particular, the NGMN (Next Generation Mobile Networks) forum, in their reports adhere to the opinion that all technologies are completely open, that is, the entire network device, starting with the physical and ending with the application level should be accessible to all users. NGMN also believes that the design and construction of a 5G network should not be carried out separately by each operator, but jointly by all operators of the regions.

The process of working in the fifth generation network is approximately the following: the user device detects the network using the built-in antenna (this stage has remained unchanged since the second generation and GSM technology), the network, that is, the AMF, through the base station, requests telephone service data.

The user device sends its registration data through the base station to the access and mobility management (AMF) function, this function compares the registration data of the device with a server on which the data of all subscribers is stored and if the provided data matches, access to the network is allowed. After registration, the user device gains access to the UPF, and through it to the services of the network.
Another difference of the fifth generation network - service virtualization and data processing in cloud operating systems - added another concept to the definition of architecture: in addition to “Plane” - “plane”, the concept of “Slicing” - “slice”, meaning different settings (or characteristics) networks) for individual users and groups, as well as for equipment. It is assumed that the 5G network provider will create special templates - virtual machines (NST, Network Slice Template), and users will be able to optimize these templates for themselves, that is, connect the required services, rent software. The architecture of the slices should not be open, since virtual machines that work remotely (in the "cloud", that is, in the Data Storage Center of the 5G provider) can be from different manufacturers. For instance,

In 2016, the NGMN forum released the document “Description of Network Slicing Concept,” which describes the logical structure of slices in three parts (bottom to top): resource level, network segment instance level, and service instance level.
The resource level includes all physical and logical resources. Physical resources are all the components that make up a network: base stations, storage systems, servers, routers, switches, even cross-connect (connecting equipment such as copper or fiber optic cable is a physical resource). Logical resources are physical resources grouped by a certain attribute or for any purpose, for example, logical resources intended for virtual hosting (a service that provides a place to store data on a constantly working, that is located on a network, server computer) : in fact, a server computer with an operating system, a data storage system - a complex consisting of several hard disks connected to each other, switches, routers and connecting cables, as well as software on demand. Network functions are not related to resources; they are part of a slice of a network segment. At the same time, the network segment plan, which is a description of the structure and the required network functions, refers to logical resources.
An instance of a network segment - this is “Slice” - a slice, which is a set of characteristics, settings, allocated resources for deploying the services and services provided by the network operator. For example, a slice designed for data exchange between machines (sensors, counters) does not require a data storage system, only a server, a switch and a router, as well as connecting cables, because sometimes a single bit of data is enough to transfer a signal from device to device - 0 or 1. If we recall the handover procedure (transfer of a user device from one base station to another), then it immediately shows that the base stations and the user device exchange text messages between themselves, yaschimi from one - two words (for example: HO REQUEST, HO RESPONSE and so on). At the same time, the slice for M2M (machine and machine) connections must be extremely reliable, that is, the message must be delivered and the ultra-low delay, that is, the message must be delivered very quickly, for example, if the car remote control program sends a message to the car sensor. Another cut-off model - to provide an Internet TV service, on the contrary, requires a data storage system, several servers, routers and connecting equipment to provide constant access to a multimedia service, which also requires ultra-low latency, but at the same time it is not required to be extremely reliable, as the loss Multiple data packets may not be noticed by the user. that is, the message must be delivered and an ultra-low delay, that is, the message must be delivered very quickly, for example, if the car's remote control program sends a message to the car's sensor. Another cut-off model - to provide an Internet TV service, on the contrary, requires a data storage system, several servers, routers and connecting equipment to provide constant access to a multimedia service, which also requires ultra-low latency, but at the same time it is not required to be extremely reliable, as the loss Multiple data packets may not be noticed by the user. that is, the message must be delivered and an ultra-low delay, that is, the message must be delivered very quickly, for example, if the car's remote control program sends a message to the car's sensor. Another cut-off model - to provide an Internet TV service, on the contrary, requires a data storage system, several servers, routers and connecting equipment to provide constant access to a multimedia service, which also requires ultra-low latency, but at the same time it is not required to be extremely reliable, as the loss Multiple data packets may not be noticed by the user.

A network segment can use various resources, consist of several logically completed subnets, while networks can use resources not only of their own slice, but also of another. The network segment must be deployed in a virtual machine, because, thanks to hypervisors (special programs that divide the physical resources of server computers into several logical components), scalability, that is, an increase in the number of slices (for example, one slice - one virtual machine) will be a very simple procedure.

A service instance level is the end service or program provided to the user. Service instances have long been part of the global network. A classic example of such a service is mail services, for example Gmail, which loads through a browser and is indistinguishable from any other site, but it uses the same network protocols as Microsoft Outlook or another stand-alone program installed on the computer and communicating with the mail service at startup a box through mail protocols.

Fifth generation networks should physically have the same simple structure as LTE networks, that is, consist only of a core network and a radio access network. But logically, 5G is much more complex in structure: the horizontal separation into the user and service planes has been preserved, the vertical separation into slices has been added, the role of computer control has been expanded, new logical elements have been added, such as the session control function or application function.

The author believes that the physical structure of the fifth generation network will be similar to the previous generation for several years, because manufacturers of user equipment (telephones, tablets, and so on) need to ensure the continuity of technology that guarantees operation in different networks, especially since the general scheme of the network device fifth generation indicated two types of base stations. Also, a smooth transition from one generation to another is evidenced by the fact that the 3GPP specifications use Non-OFDM as a modulation method, which is already implemented in LTE Advanced networks.

The fifth generation of communications will provide manufacturers and private users with services that were not provided for in LTE networks or did not function properly, such as interaction between machines, that is, the use of various sensors.

In conclusion, it must be said that for the deployment of fifth-generation networks in Kazakhstan, according to the author, Kazakhtelecom JSC is best suited, which owns 100% of the Altel mobile operator, which provides LTE cellular network services and 75% of the mobile operator’s shares Kcell. " The company offers its customers virtual hosting, has several data centers in different cities of the Republic. If the International Telecommunication Union submits to the international community the approved 5G specifications (IMT-2020) in December 2019, then Kazakhtelecom JSC will be able to commission the fifth generation networks by 2025.

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