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Telecommunications Overview

Telecommunications Overview. Richard Selby. Local Access Network. The link between the customer and the Local Exchange (or “Switch”) Sometimes called the “Local Loop” could be: Copper Cable (Overhead or underground) Coaxial cable (with cable TV) Wire-less Local Loop (WLL).

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Telecommunications Overview

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  1. Telecommunications Overview Richard Selby

  2. Local Access Network • The link between the customer and the Local Exchange (or “Switch”) • Sometimes called the “Local Loop” • could be: • Copper Cable (Overhead or underground) • Coaxial cable (with cable TV) • Wire-less Local Loop (WLL)

  3. Overhead Copper Cable • Connected to customers from poles “Drop Wires” • sometimes shared with other users eg: power companies • Possible danger of electrocution to installers • Quick and easy to install

  4. Underground Copper Cable • Usually installed when new development is built • More secure • Longer to connect a new line

  5. Coaxial Cable • Supplied with Cable TV, providing the Regulator permits it • Overhead or underground coaxial cable from local distribution cabinet

  6. Wire-less Local Loop • Connection is through a centrally located “Base Station” at a high point in the area • Customer must have “Line of Sight” to the Base Station • Customer must have an antenna on his house, and additional equipment inside house • No local cable to maintain - so cheaper

  7. Local Exchange • Digital • solid state - computer controlled • Analogue • electro-mechanical

  8. Junction Network • Connects from Local Exchange to Trunk Exchange • Usually Fibre Cable for Digital equipment • Usually Coaxial Cable for Analogue

  9. Trunk Network • Connects trunk exchanges together • Could be: • Coaxial Cable • Microwave Radio • Optical Fibre • Domestic Earth Stations

  10. Coaxial Cable • Copper centre conductor surrounded by copper tube. Each separated by an insulator • Carries High Frequency “Multiplexed” signals over long distances. • Requires “Repeaters” to amplify the signal • Noise distortion introduced at each Repeater

  11. Microwaves • Frequency Range about 3GHz upwards • Travel in straight lines (through a uniform medium) • Can be reflected (eg: by water or flat metal roofs) • CAN BE DANGEROUS! - remember your microwave oven!

  12. Microwave Radio • Can be Analogue or Digital • Requires “Line of Sight” between antennae • “Dish” antennae are very directional • Antennae are usually fitted at high level (eg on a Tower, Mast or tall building)

  13. Optical Fibres • Only used with Digital systems - high bandwidth • Made of very thin, pure glass - flexible • Secure • Low attenuation • Can carry digital signals over long distances before “Regeneration” is required

  14. Optical Fibres (2) • Considerable traffic can be carried through each fibre - works out cheaper than copper • Requires laser energy to produce “optical” signal. • Laser energy used is not visible - AND CAN BURN! • remember the surgeon!

  15. Satellite • Communication Satellites in Geostationery Orbit (36000km) • Large Antennae required • Special rceiving equipment required • Not secure • Compliments Fibre & Coax • Staffing issues • Sun Interference

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