1. Introduction
There are various cellular systems in the world such as GSM and CDMA. The design of these cellular systems is complicated, but the architecture of most cellular systems can be broken down into six basic components.
In this article, I will illustrate the six basic components that can be found in most cellular systems.
2. Six basic components of Cellular Systems
The architecture of most cellular systems can be divided into the following six components:
a) Mobile Station (MS)
A mobile station is basically a mobile/wireless device that contains a control unit, a transceiver and an antenna system for data and voice transmission. For example, in GSM networks, the mobile station will be composed of the mobile equipment (ME) and the SIM card.
b) Standard air interface
There are three main air interface protocols or standards: frequency division multiple access (FDMA), time division multiple access (TDMA), and code division multiple access (CDMA). These standards are basically the medium access control (MAC) protocols that define the rules for entities to access the communication medium.
These air interface standards allow many mobile users to simultaneously share the finite number of radio channels.
c) Base Station (BS)
A base station is a fixed station in a mobile cellular system that is used for radio communications with mobile units. They consist of radio channels and transmitting and receiving antennas mounted on a tower.
d) Databases
Another integral component of a cellular system is databases. Databases are used to keep track of information such as billing, caller location, subscriber details, etc. There are two main databases called the Home Location Register (HLR) and the Visitor Location Register (VLR). The HLR contains the information of each subscriber residing in the same city as the mobile switching center (MSC). The VLR temporarily stores the information of each visiting subscriber in the coverage area of an MSC. Therefore, the VLR is the database that supports the roaming capability.
e) Security Mechanism
The security mechanism is to confirm that a particular subscriber can access the network and also to authenticate billing.
There are two databases used for the security mechanism: Equipment Identification Registry (EIR) and Authentication Center (AuC). The EIR identifies stolen or fraudulently altered phones that transmit identity data that does not match the information contained in the HLR or VLR. The AuC, on the other hand, manages the actual encryption and verification of each subscriber.
f) gateway
The last basic component of a cellular system is the Gateway. The gateway is the communication link between two wireless systems or between wireless and wired systems. There are two logical components within the Gateway: the Mobile Switching Center (MSC) and the Internetworking Function (IWF).
The MSC connects the cellular base stations and mobile stations to the public switched telephone network (PSTN) or another MSC. Contains the EIR database.
The IWF connects the cellular base stations and mobile stations to the Internet and performs protocol translation if necessary.
3. Conclusion
This article aims to provide an introductory guide to the architecture of a typical cellular system and to identify the six basic components found in most cellular systems. This article provides an idea of how a cellular system is designed, although different cellular systems may have variations on their own implementations.