why cellular phone are called cellular

They are called such because they are used within a cellular network

Chris

The reason I asked is that my college professor told us a story concerning Best Buy 'experts' and cordless phones. He had asked one of the associates about the 5.8 GHz phones and he was told that they can 'communicate further' because of the higher frequency when compared to the 2.4 GHz phones. He told us that 'that is not true' but never went into detail about it. By the time I got around to figure out why this is so a semester later he had moved on.

I figured it would have something to do with the atmosphere, obstacles, clarity, bandwidth, and of commerical reasons for the increasing frequency range. Thanks for the explanation.

It involves refraction. Lower frequencies (longer wavelength) pass around obstacles that are much smaller than their wavelength with little loss or reflection. When a wave encounters an object larger than its wavelength, it tends to be absorbed by the object, or reflected by it, or some combination of those two. Little of it will continue on behind the obstacle.

So, going straight up, the distance capability is pretty independent of wavelength, except for atmospheric absorption and reflection at some resonance frequencies. But along the ground, where the waves propagate through trees, buildings and lots of other obstacles, the short wavelengths get lost much closer to the source.

There were mobile, and even portable, phones before cellphones came along. But it meant connecting with one (or a few) central stations (and usually required an operator at that station to do the actual dialing), and relatively high power was needed. Only a handful of frequencies were assigned to mobile phone use, and only one person could use a given frequency at a time in most locations. Thus it could never be a system for the masses, and the cost was quite high.

Cellphones change all that. They got a slew of frequencies. More important, the "base stations" are spread out all over town. This means power levels are much lower, at the base and in the cellphone. If you're in area A, someone across town in area X can use the same frequency because the frequencies are high enough in the radio spectrum so they won't travel far, and the power levels additionally limit the range of the signals. This means the frequencies can be reused throughout a city, just making sure that adjacent cell "bases" don't use the same ones. As someone moves along, they will move into a new cell, and the network will automatically switch them over to the next one (ie change the frequency, and pass them on to the next cell, so the user never notices that anything has changed. The cellphones are a lot "smarter" than the old mobile phones, that had nothing but the radio transmitter and receiver.

Michael

You would find the site 'howstuffworks' very helpful for these sort of questions

David

"neeraj snipped-for-privacy@yahoo.co.> i want to know why celllular phone are called so and other details like

lower frequencies tend to pass arround and through obstacles, higher frequencies thend to be absorbed or reflected by them.

Bye. Jasen

visible light is strictly line of sight :)

Because if you map the coverage areas of multiple transceiver towers, their ranges are each adjoining roundish objects resembling cells (such as organism tissues under a microscope).