Cable and Satellite Systems

Cable System Advantages

•	Cable is a closed system – it can make use of many frequencies that can’t be used for TV over the air
•	Cable can offer many channels by multiplexing its channel
o	Analog, 70 to 80 channels
o	Digital, several hundred channels
•	Divides the bandwidth of the coax into many channels
•	No problems that plague broadcasting such as ghosting and interference
•	With all-digital systems, many more channels and services are possible

Cable System Disadvantages

•	Cable systems are very cost-intensive – require a tremendous amount of money to build and maintain
•	The signal requires constant amplification all through the system
•	The cables are either strung on poles or buried, both of which are costly propositions
•	These costs are passed along to the consumer

Cable System Design

•	All the programming is assembled at the cable headend
•	It comes in via broadcast, microwave, and satellite systems
•	The headend equipment processes the signals, moves them to the appropriate frequencies for transmission through the system and then propagates the signal
•	The entire system is called a tree-and-branch pattern
•	Large trunk cables branch to neighborhood feeder cables that lead to drop cables that go to houses, much like the phone system works

Satellites 

•	Geosynchronous or Geostationary
o	Idea originated by Arthur C. Clarke
o	22,300 miles above the Earth
•	Low Earth Orbit (LEOs)
o	Orbits at varied altitudes
o	Constant coverage requires multiple satellites
•	Footprint – area covered by the satellite's signal – can be as large as one third of the earth's surface
•	Very Small Aperture Terminal (VSAT)
o	The ultimate business solution
•	C-band – 4 and 6 gigahertz
•	Ku-band – 11 and 14 gigahertz
•	K-band – 12 to 18 gigahertz (DBS)
•	Ka-band – 20 to 30 gigahertz
•	S-band – 2 gigahertz (NASA)
•	X-band – 7 to 9 gigahertz (military)
•	Dish sizes –  (largest to smallest) – C, Ku, VSAT, DBS, Ka (antenna)
•	Bypass:
o	is the use of private facilities or services to go around the local telephone exchanges and commercial broadband providers.
o	one form of bypass in some large cities is the teleport.
o	teleports are extensive earth station and satellite antenna complexes constructed to serve large volume users in metropolitan areas.
•	Bypass is only attractive to very large subscribers with heavy traffic volumes, particularly among their own company locations.