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