Using modems to exchange information can be inefficient. Suppose you use a 9.6 K

Question

Using modems to exchange information can be inefficient. Suppose you use a 9.6 Kbps modem to do an on-line chatting from your home computer to a friend's computer. During this transmission, a telephone connection is established. Suppose you are trying to send a long message to your friend. Assume that you are a fast typist, you can type 400 characters per minute where the data size of 1 character is 1 byte. Show that you are using less than 0.6% of the bandwidth capacity of the modem connection. (This example reveals a problem of the dedicated resource assignment in circuit-switching networks.)

Explanation / Answer

Here typing speed is 400 characters per min with a character taking 1 byte.

1 byte = 8 bits

Hence typing speed in bits per min = 400*8= 3200 bits per min= 3.2 Kilobits per min

Note: Approximating 1Kb=1000b instead of 1024b for easier calculation

Typing speed in bits per sec = 3.2/60 Kbps which is the information transmission rate for this case

Speed of modem = 9.6Kbps

Bandwidth Capactity being used = Information Transmission Rate/ Modem speed= (3.2/60)/9.6=1/180=0.005555556

To give it in %age, multiply this with 100.

Bandwidth Capactity being used=0.005555556*100=0.5555556

Hnce proved we are using lss than 0.6% of the bandwidth capacity.

Considering this modem is used for typing purpose only, the rest of the bandwidth will be useless. This is the issue with dedicated resources.

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