Cellular concepts
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There are multiple concepts behind mobile phones, including the physics behind the network and towers that connect the cellular phones.
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[edit] The concept
The concept of cellular radio can be used to explain the differing receptions at various locations.
An area to be supplied with radio service is divided into cells. Each of these cells is assigned a range of frequencies (f1 - f6) and they each have corresponding radio base stations. The group of frequencies can be reused in other cells bearing in mind that it is not reused in adjacent cells as that will cause co-channel interference. Co-channel inteference results when frequencies are reused in adjacent neighbouring cells. A reuse distance, D is calculated as
where R is the cell radius and N is the number of cells per cluster. cells may vary in radius in the ranges (1 km to 30 km). The shape of the cells can be hexagonal, circular or some other undefined irregular shapes. The boundaries of the cells can also overlap between adjacent cells. [1]
[edit] Structure of the cellular network
A simple structure of the cellular mobile-radio network consists of the following:
- RBS : Radio base station
- MSC : Mobile Switching Centre
- PSTN: Public switched telephone network
The concept of cells consists of mobile network equipment providing a cellular network for mobile station (MS) and PSTN users. This network is the foundation of the GSM system network. There are many functions that are performed by this network in order to make sure telephone customers get the desired service; some of them include mobility management, registration, call set up, and handover. Any MS connects to the network via an RBS in the corresponding cell which in turn connects to the MSC. The MSC allows the connection of other networks apart from mobile networks. The link from an MS to the RBS is called an uplink while that from a RBS to the MS is termed downlink; for more information, see GSM.
Radio channels effectively use tranmission medium through the use of the following multiplexing schemes: frequency division multiplex (FDM), time division multiplex (TDM), code division multiplex (CDM), and space division multiplex (SDM). Corresponding to these multiplexing schemes are the following access techniques: frequency division multiple access (FDMA), time division multiple access (TDMA), code division multiple access (CDMA), and space division multiple access (SDMA). [2]
[edit] Notes
- ^ J. E. Flood. Telecommunicattions Networks. Institution of Electrical Engineers, London, UK, 1997. chapter 12.
- ^ Bernhard H. Walke. Mobile Radio Networks: Networking, protocols and traffic perfomance. John Wiley and Sons, LTD West Sussex England, 2002. Chapter 2.
[edit] References
- P. Key, D. Smith. Teletraffic Engineering in a competitive world. Elsevier Science B.V., Amsterdam Netherlands, 1999. Chapter 1 (Plenary) and 3 (mobile).
