a) Your city has 100 cells in one of its second-generation cellular telephone sy

Question

a) Your city has 100 cells in one of its second-generation cellular telephone systems. As a rough rule of thumb, you can divide the number of cells by seven and get the average number of times you can reuse each channel throughout the system. In other words, if you have 21 cells, you can reuse each frequency about three times on average. There also is a 3:1 compression ratio for voice conversations relative to what a channel would be able to carry without compression. There are 2,500 channels in the frequency spectrum allotted for this service. On average, subscribers will only be using their cellphones 3% of the time, but call this 5% to be on the safe side. Consequently, each channel can support 20 subscribers and still give good service. How many subscribers can the system support? Show your work. Hint: The answer is about two million. (b) Redo your calculation for a first-generation system with 20 cells. Your calculation should reflect other differences between first-generation and second-generation systems. Hint: This system can serve only about a tenth as many subscribers.

Explanation / Answer

For Second Generation!

There are 100 cells/city. Calculating channel reuse (100/7) i.e. 14 channels.

We have number of channels-2500, so effective channels will be (2500*14) i.e. 35000.

Considering the compression of 3:1, the channels will be 1,05,000 i.e (35000*3)

So number of subscibers will 2,000,000.

For First Generation

Cells per city is 20. So channel reuse will be (20/7) i.e. around 3 channels.

So toal number of effective channels (2500 * 3), 7500 channels. Since first generation has no compression, so effective channels remain same 7500. and Total subscribers will be around 200000. :)

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