Cellular wireless networks are now supporting wireless Internet access and other unguided data networking apart from mobile telephony. A cellular system is based on the principle of using an extensive geographical area which is separated into small regions known as the cells. Each cell is assigned a band of frequencies which is rendered by a base station made up of a transmitter, receiver, and control unit. Stallings outlines that adjacent cells are allocated dissimilar frequencies to avoid crosstalk or attenuation. However, a frequency band can be shared by multiple cells or number of users, hence multiple access (2005).
The Global System for Mobile Communication (GSM) is a worldwide protocol used for digital cellular transmissions among other multi access systems such as the Code Division Multiple Access (CDMA). GSM network functions in the 1800 to 1990MHz frequency range and make use of Time Division Multiple Access (TDMA) concept. According to the International Engineering Consortium (IEC), the three functional components or systems that constitute the GSM architecture are: the network and switching system (SS), the base station system (BSS), and the operation and support system (OSS).
The network and switching system performs call dispensation and subscriber-related tasks. The major element of the switching subsystem is the Mobile Services Switching Center (MSC). It acts as a telephony switching center that controls the calls to and from other receivers and data systems, thus providing all the tasks needed to satisfy a mobile subscriber: registration, handovers, validation and call routing to a straying subscriber. The Home Location Register (HLR) element contains all the details about a subscriber to the GSM network, together with the locality of the mobile– it acts as a database; this location is actually in form of the address used for signaling by Visitor Locator Register (VLR) linked with the mobile station. The Equipment Identity Register (EIR) holds the information, thus the IMEI identifies the mobile station.
The Base Station System (BSS) is made up of two components; the Base Transceiver Stations (BTSs) and base Station Controllers (BSCs) which controls all the radio- associated tasks (International Engineering Consortium). The BTS holds the interface of the radio to the mobile station. It constitutes the transceivers and antennas of the radio device which is required to operate each cell in the GSM network. BSC manages a group of BTSs. The BSC handles the resources of radio for one or several BTSs.
The third primary entity of a GSM network is the operation and support system (OSS). This component enables a centralized process, planning and maintenance of the other GSM sub modules. The purpose of this system is to present customers with cost-effective management and operational activities required in the network. The OSS is made up of the Authentication Center (AUC) and the Operational and Maintenance Center (OMC). The AUC generates parameters that are unique to the users through the VLR request and in turn store the various authentication arguments used for mobile validation and user data encryption within the GSM network. The OMC on the other hand, has the capability to control radio and network subsystems.
Both GSM and CDMA are the competing cellular networks. The dominance of one over the other depends on the needs of customers in respect to data transfer speed, coverage and roaming. For data transfer speed, the CDMA is faster than the GSM. But in coverage, GSM can present international roaming and calls, while CDMA which are not-card enabled are difficult to offer this service; hence GSM users are many as compared to CDMA users. Because bandwidth is a major problem in contemporary times, the CDMA possesses itself as superior over the GSM. The available channels that can be assigned to users in a certain bandwidth are higher for CDMA than for GSM. And even the set up cost for CDMA is lesser.
References
- Stallings, W. (2005). Business Data Communications. (5th edition). Upper Saddle River, NJ: Pearson Prentice Hall.
- International Engineering Consortium. (2007). Global System for Mobile Communication (GSM).