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Cellular Primer

 Cellular networks are groups of radio transmitters belonging to the same network. The transmission masts are linked together using telephony technologies, which I won’t describe further.

Each mobile tower broadcasts on a range of frequencies. The highest frequency minus the lowest frequency is called the transmission band width. If there are several mobile users within a cell they must all share the transmitters bandwidth. This can be done in a couple of ways. The first way is to use channels i.e each user only transmits on a narrow band width of frequencies which must not overlap with other mobile users. The second way is to make sure that each mobile does not transmit a signal at the same time also known as time division multiplexing. Splitting the bandwidth into channels is a good way of sending signals that exist as streams such as voice communications and video, but it does have its draw backs. Time division multiplexing relies on data being split into packets and transmitted in bursts at scheduled times.

It doesn’t matter which system is used each cell can only have a finite number of cellular users as there will be a limit to as to how many ways signal bandwidth can be split. In cities there can be huge numbers of cellular users within a cell. In these situations a cell can become saturated with mobile users. In order to reduce the number of users within a cell, engineers shrink the size of a cell by reducing the cells transmission power. By reducing the transmission power, mobile cells can be packed together more densely. Using the cell shrinking scheme more subscribers can access the cellular system. Conversely in areas with a low subscriber density it is necessary to have larger cells and higher power transmission. Handset transmission power is limited  so in a larger cell signal may be weak on the handset side. In a larger cell there might be more obstacles in the signals path to attenuate a signal. There may be no service in rural areas the subscriber density might be so low as to make it uneconomical for a phone company to place a transmitter in that location.

 

Cellular Generations Referred to as G(s)

 

Cellular phones and IT technology is improving all the time.

A major limitation as to the amount of data that can be transmitted by a radio transmitter is the bandwidth over which it can operate. Engineers have be working out ways to increase bandwidth over the last twenty years. With each leap forward in transmission capability, a new raft of technologies has become feasible. Investing in these new technologies is expensive and rolled out over a network. This has led to the classification of these technologies being described as their G rating. The G rating reflects the capabilities of the network you are logged into.