Cellphone Spectrum

[person]

I heard that the Canadian government is auctioning 105MHz of spectrum for wireless providers. And 40MHz of the spectrum is reserved for new entrants. I'm just wondering what does this mean? I thought MHz is just a frequency, so how can they divide up 105MHz into 65MHz and 40MHz??

[Tony]

MHz is indeed used to measure frequency, but here they are talking about the spectrum.

For example, consider two waves with frequency of 100 MHz and 205 MHz. Any wave in between (that is, faster than 100 but slower than 205) fill fall onto the spectrum defined by those two extremes. The difference between the bounds, and thus the size of the spectrum is 205 - 100 = 105 MHz. The use of the unit could be kind of confusing when taken out of context.

The point is, since frequency is a continuous measurement (that is, you could have a frequency of 100.123... MHz), they are licensed out in bulk.

[person]

Does this mean that each cell phone emits its own frequency?

[Tony]

In a way, but not really. Your cellphone's frequency just has to be unique just from others in the area, to avoid interference. As you physically move from one "cell" to another, the frequencies that your cellphone uses might change.

[md]

Actually that's not true; you can indeed use the same frequency for multiple devices with some advanced signal filtering and timing.

Wifi for instance uses a single frequency for each channel; and yet you can have multiple devices on each channel.