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TV Video Signals

a. A cable TV company delivers video signals over coaxial cable to individual houses. Video signals occupy a bandwidth of 6 MHz and are stacked in frequency from 50 MHz to 656 MHz without guard bands. There are 100 video channels numbered 1 through 100. Is this system using FDM or FDMA?

b. When NTSC analog TV signals are sent over the cable, the video portion of the signal occupies the lower 5.7 MHz of the 6 MHz channel as a VSB-AM signal and an FM audio signal with a bandwidth of 100 kHz is located between 5.8 and 5.9 MHz. Are the channels using FDM or FDMA to deliver the video and audio portions of the TV signal?

c. A broadcast TV station would like to transmit the same 100 analog TV channels described in part (b) above that the cable TV company distributes via coaxial cable. The radio spectrum available to this station lies between 470 MHz and 840 MHz. Give two reasons why the TV station cannot transmit 100 TV channels.

d. A direct broadcast satellite television (DBS-TV) company competes with the cable TV company to transmit the same 100 TV channels to all households in the US using a large geostationary satellite. The TV transmissions are digital and one transponder on the satellite can transmit eight pre-recorded TV signals or four live TV signals in an RF bandwidth of 30 MHz. The 100 TV channels include 12 live TV signals and 88 pre-recorded signals
How many transponders are needed on the satellite? If guard bands of 6 MHz are needed between the RF signals, what is the total RF bandwidth occupied by the 100 TV channel?

Solution Preview

a.
This is an FDMA system for the reasons specified below:
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Please see attachment for the rest of the solution.

A cable TV company delivers video signals over coaxial cable to individual houses.
a. A cable TV company delivers video signals over coaxial cable to individual houses. Video signals occupy a bandwidth of 6 MHz and are stacked in frequency from 50 MHz to 656 MHz without guard bands. There are 100 video channels numbered 1 through 100. Is this system using FDM or FDMA?

This is an FDMA system for the reasons specified below
Each TV carrier comprises an FDM signal each of which consists of multiple low bandwidth signals (eg video baseband, audio baseband component signals) multiplexed onto carriers at the physical layer. These multiple and unique FDM constructed carriers are then grouped and provide the components of the multiple access network, the network by which customers select individual TV stations which forms part of the data link layer. This type of access is known as Frequency Division Multiple Access, FDMA for short, as unique streams (services) are selected and accessed via unique frequency carriers.
Characterisation and differences between FDM and FDMA ...

Solution Summary

TV video signals are examined.

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