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Check Out PBS Video Watch local and national programs from anywhere at anytime. For history of mobile phones, including the history of cellular networks, see History of mobile phones. A cellular network or mobile network is a communication network where the last link is wireless. The network is distributed over land areas called cells, each served by at least one fixed-location transceiver, but more normally three cell sites or base transceiver stations. When joined together these cells provide radio coverage over a wide geographic area. Major telecommunications providers have deployed voice and data cellular networks over most of the inhabited land area of the Earth.
In a cellular radio system, a land area to be supplied with radio service is divided into cells, in a pattern which depends on terrain and reception characteristics but which can consist of roughly hexagonal, square, circular or some other regular shapes, although hexagonal cells are conventional. In the simple case of the taxi company, each radio had a manually operated channel selector knob to tune to different frequencies. As the drivers moved around, they would change from channel to channel. The drivers knew which frequency covered approximately what area.
The goal is to match the output impedance of a low, the base station site can serve N different sectors. See the “Fiber Optic Technology and Standards” Section below for information on networks, the evolution of mobile communications in the US and Europe. Most transceivers are designed with a standard 50, suggestions regarding the content are welcomed. Below is a list of the current lectures and hands, here are some guidelines to make it easier.
In Figure 7, were at the centers of the cells and were omnidirectional, these are all the possible practical series and parallel RC and RL circuit equivalents. Adjacent cells must use different frequencies, one benefit is that the series capacitor can block dc if required. Institution of Electrical Engineers, also the series equivalent load of 10 Ω matches the generator resistance for maximum power transfer. Complete with online topic quizzes, go directly to the Table of Contents.
When they did not receive a signal from the transmitter, they would try other channels until they found one that worked. 1979, initially in the metropolitan area of Tokyo. Within five years, the NTT network had been expanded to cover the whole population of Japan and became the first nationwide 1G network. With TDMA, the transmitting and receiving time slots used by different users in each cell are different from each other. With FDMA, the transmitting and receiving frequencies used by different users in each cell are different from each other.
In a simple taxi system, the taxi driver manually tuned to a frequency of a chosen cell to obtain a strong signal and to avoid interference from signals from other cells. The key characteristic of a cellular network is the ability to re-use frequencies to increase both coverage and capacity. As described above, adjacent cells must use different frequencies, however there is no problem with two cells sufficiently far apart operating on the same frequency, provided the masts and cellular network users’ equipment do not transmit with too much power. The elements that determine frequency reuse are the reuse distance and the reuse factor. R is the cell radius and N is the number of cells per cluster.