Page 43 - DCAP406_DCAP_207_Computer Networks

Computer Networks/Networks

Notes
Figure 3.4: Coaxial Cable Configurations

General Properties of Coaxial Cable

Gauge: The gauge of coaxial cable is thicker than the twisted pair. While this increases the
available bandwidth and the distance of transmission, it also increases the cost. Traditional
coaxial cable is quite thick, heavy and bulky of which Ethernet LAN 10Base5 is an example.
Ethernet LAN 10Base2 is of much lesser dimensions but offers less in terms of performance.

Configuration: Coaxial cables consist of a single, two-conductor wire, with a centre
conductor and an outer shield/conductor, which is of solid metal. Sometimes braided or
stranded metal is used. Twin axial cables contain two such configurations within a single
cable sheath. As the centre conductor carries the carrier signal and the outer conductor
generally is used for electrical grounding. Coaxial cable connectivity can be extended
through the use of twisted pair with a BALUN (BALanced/UNbalanced) connector serving
to accomplish the interface.

Bandwidth: The effective capacity of coaxial cable depends on several factors, including
the gauge of the centre conductor, the length of the circuit, and the spacing of amplifiers
and other intermediate devices. The available bandwidth over coaxial cable is very
significant; hence it is used in high capacity applications, such as data and image
transmission.
Error Performance: Coaxial cable performs exceptionally well, due to the outer shielding.
As a result, it is often used in data applications.

Distance: Coaxial cable is not as limited as UTP, although amplifiers or other intermediate
devices must be used to extend high frequency transmissions over distances of any
significance.
Security: Coaxial cable is inherently quite secure. It is relatively difficult to place physical
taps on coaxial cable. Radiation of energy is also minimal hence interception of it is not
easy.
Cost: The acquisition, deployment, and rearrangement costs of coaxial cables are very
high, compared with UTP. In high capacity data applications, however, that cost is often
outweighed by its positive performance characteristics.

Applications: Coaxial cable’s superior performance characteristics make it the favored
medium in many short hauls, bandwidth-intensive data applications. Current and
continuing applications include LAN backbone, host-to-host, host-to-peripheral and CATV.

Self Assessment

State whether the following statements are true or false:
6. Twisted pair (both unshielded and shielded), coaxial and fiber optic cable systems fall into
guided transmission media category.

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