Chapter 1 - Introduction

Last updated Apr 30, 2022

• Type note
• Status good
• On networks
• On 5 g
• Source book

• A Mobile Telecommunication System, officially known as Public Land Mobile Network (PLMN), is run by a network operator.
  • It has four main components:
    • The Core Network (CN)
    • The Radio Access Network (RAN)
    • The Management System
    • The User’s Device ( Mobile/ User Equipment (UE))
• The core network transports traffic between the mobile and one or more external networks, such as the public switched telephone network (PSTN) or the Internet. It also controls the mobile’s communications with those external networks, and stores information about the network operator’s subscribers.
• The radio access network handles the network’s radio communications with the mobile.
  • It communicates with the core network over an interface known as the backhaul, and with the mobile over the air interface, also known as the radio interface.
  • On that interface, the direction from network to mobile is known as the downlink (DL) or forward link, and the direction from mobile to network is the uplink (UL) or reverse link.
• The network is controlled by a separate management system. Its tasks include
  • configuring the various components of the core and radio access networks,
  • monitoring their performance,
  • reporting any faults to the network operator,
  • and billing the user.
• 

# Internal Architecture of the Mobile

• It has two main components:
  • Mobile Equipment (ME)
    • It is the actual communication device.
    • It can also be divided into two parts:
      • Mobile Termination (MT)
        • It handles all the communication functions.
      • Terminal Equipment (TE)
        • It terminates the data streams.
  • Universal Integrated Circuit Card (UICC)
  • It runs an application known as the Universal Subscriber Identity Module (USIM), which stores user-specific data such as the home network identity and carries out security-related calculations using secure keys that the smart card stores.

• The most important component of the radio access network is the base station.
  • On the air interface, it transmits and receives using one or more radio frequencies, each of which is known as a carrier frequency.
  • Around each carrier, the radio signal occupies a certain amount of radio spectrum, which is known as the bandwidth.
  • It usually operates in licensed spectrum, in which the network operator has purchased an exclusive license to carry out radio communication from the corresponding national regulator.
  • In case of unlicensed spectrum, the transmitters have to use a low power so that they do not cause undue interference to other receivers in the same band.
• The base station controls one or more cells.
  • A cell is a radio transmission with a particular carrier frequency and bandwidth, which spans a particular coverage area.
  • On any one frequency, a base station can control multiple cells, known as sectors, by transmitting in different directions.
    • There are typically three sectors per base station, with each one spanning an arc of $120 \degree$.
  • The base station can also control multiple cells in the same direction, by using different radio frequencies to ensure that the radio signals do not interfere.

• There are two main limits on a cell’s performance:
  • Each cell has a coverage limit.
    • A coverage limit is the maximum distance at which the receiver can successfully hear the transmitter.
  • Each cell has a capacity limit.
    • A capacity limit is the maximum combined data rate of all the mobiles that are communicating through the cell.
• Based on these limits, cells can be divided into different classes:
  • Macrocells
  • Microcells
  • Picocells
  • Femtocells

• In older networks, the core network contains two domains:
  • The circuit-switched (CS) domain
    • It transports fixed-rate traffic such as voice.
    • It does that using a technique known as circuit switching, which sets aside a dedicated two-way connection for each individual phone call.
  • The packet-switched (PS) domain
    • It transports variable rate traffic such as web pages.
    • It does that using a different technique, known as packet switching, in which a data stream is divided into packets, each of which is labelled with the address of the required destination device. Within the network, routers read the destination addresses of the incoming data packets, and forward them towards those destinations by following the instructions in internal routing tables.
    • This is more efficient than circuit switching.
  • Recently, with the widespread use of data, circuit switching is abandoned in favor of packet switching.

• The internet’s protocols are designed by the Internet Engineering Task Force (IETF).
• Examples of the communication protocols used by the internet
• The transport layers manages the end-to-end data transmission.
  • Transmission Control Protocol (TCP)
    • Re-transmits the packet if it doesn’t arrive correctly.
    • More reliable.
  • User Datagram Protocol (UDP)
    • No re-transmission.
    • Suitable for real-time transmission.
• In the network layer, the Internet Protocol (IP) sends packets on the correct route from source to destination, using the IP address of the destination device.
• The data link layer manages the transmission of packets from one device to the next.
• The physical layer deals with the actual transmission details.
• At each level of the transmitter’s stack, a protocol receives a data packet from the protocol above in the form of a service data unit (SDU).
  • It processes the packet, adds a header to describe the processing it has carried out, and outputs the result as a protocol data unit (PDU).

• The first-generation (1G) systems used analogue communication techniques which were similar to those in a traditional analogue radio.
• The most popular 2G system was the Global System for Mobile Communications (GSM).
  • GSM was originally designed just for voice, but was later enhanced to support instant messaging by means of the Short Message Service (SMS), and the delivery of packet data to a mobile device by means of the General Packet Radio Service (GPRS).
  • Another enhancement was Enhanced Data Rates for GSM Evolution (EDGE), which modified the air interface so as to increase the available data rate.

• Nowadays, mobile networks are dominated by data, instead of by voice calls.
• Developed markets are saturated with smartphones, and sales have begun to stall.
• Network operators’ income is stalled, because of increasing level of competition, free WIFI access and usage by subscribers, and third-party services for voice and messaging.

• The 3GPP identified several potential markets and use cases for 5G, and grouped those into five families:
  • Enhanced Mobile Broadband (eMBB)
    • Calls for a higher data rate than LTE.
    • Application examples include
      • data downloads and real-time video in an indoor office environment
      • traffic hotspots such as shopping centers and other dense urban environments,
      • public events such as football matches and concerts,
      • and the provision of a consistent mobile broadband experience for consumers in rural areas and on public transport.
    • Although this is the first use-case that 5G is addressing, it appears unlikely to be the key to its long-term success, for two reasons.
      • The long-term revenue does not appear to be sufficient.
      • LTE can already deliver the data rates that are required by the most common mobile applications.
    • Nevertheless, 5G does offer some benefits, particularly in terms of a higher network capacity and a lower consumption of electrical power
  • Massive Machine-type Communications (MTC)
    • Also known as Internet of Things (IoT).
    • This refers to wireless communications between autonomous machine-type devices without any direct human interaction.
    • Application examples include
      • wireless tracking (goods in a warehouse, vehicles in a delivery system, etc.)
      • wireless sensors
      • electronic health (reporting of medical information)
    • The market for MTC has been widely expected to grow.
    • MTC has different performance requirements from mobile broadband.
      • The devices must be cheap, and they require a low power consumption to ensure a long battery life.
      • The devices must also communicate successfully if the received signal is very weak.
    • There are already several technologies for wide-area MTC.
      • GPRS
      • extended coverage GSM (EC-GSM)
      • eMTC and NB-IoT
      • Long Range Wide Area Network (LoRaWAN) and Sigfox
    • At least in the short to medium term, MTC does not appear to be a core use case for 5G.
  • Ultra-reliable Low-latency Communication (URLLC)
    • Also known as critical communication (CriC).
    • It is a use case characterized by the need for very low latency, often in conjunction with very high reliability.
    • Latency is the time required to deliver packets between the mobile and an external server.
  • Vehicle-to-everything Communication (V2X)
    • Vehicle-to-everything (V2X) communication refers to the exchange of information between a road vehicle and the mobile telecommunication network, and with other vehicles and pedestrians that are nearby.
  • Network Operation (NEO)
    • 3GPP defined a final set of internal requirements, which include requirements
      • to optimize and re-route the traffic path in the case of low-latency applications,
      • to interact with a client’s application servers
      • and to reconfigure a network to support new use cases as they arise.

5G does not have to meet all of these requirements at the same time.

# Network Function Virtualization