Cable TV Networking Technical Documents

Technology

Data Bandwidth in Cable networks.

The recommended Bandwidth in fiber networks is 100 Mb per home. This can be achieved in Point to Point networks. However, because of its structure this is not always possible in Point to Multipoint networks. In existing and new coaxial networks the maximum Band width under EURO-DOCSIS 1 and 1.1 was a maximum of 56 MB per home .

This has changed with DOCSIS 3 where data bandwidths of over 1 Gb per home over coaxial cable networks is possible. It therefore can more than meet the fast increasing demand on band width. In comparison to coaxial systems fiber networks are still expensive. There are World wide still many existing coaxial cable based Cable TV networks where a change to fiber is for cost reasons not viable.

This is where DOCSIS 3 can fill the gap as a cost effective alternative. It can be used over new and existing cable networks (also fiber) and provides data bandwidths which in the past ware only possible in P to P fiber networks. It can easily guarantee the recommended 100 Mb per subscriber.

A further advantage is that DOCSIS 3 is backward compatible, meaning that the current Cable Modems will not be obsolete and will still work in the new, upgraded system.

THE 4 METHODS FOR SAT IF AND
TERRESTRIAL SIGNAL DISTRIBUTION IN CABLE NETWORKS

The matrix switching system

Standard DSTV decoders can be used in default configuration. Multi polarity is possible. Special models allow the throughput of data with return path. Speak to our specialist for equipment and system design.

One wire IF systems

Pros: Standard DSTV decoders can be used, single cable design and components are more cost effective than matrix system.

Cons: requires special decoder settings.

Signal Multiplexing over fiber

This is the most elegant version which provides the satellite signals in both polarities in sat IF together with the terrestrial frequency spectrum and data to the home. DSTV decoders can be connected in their default setting.

Cons.: price

64 and 128 QAM Transmodulation

  • Pros: This is an economic way of transporting large numbers of digital services over coaxial cable TV networks.
  • Pros: The transmodulation technique converts the QPSK satellite signals to 64 to 128MHz QAM modulated signal in the terrestrial frequency spectrum. The software driven, modular Head End System has a re-programmable NIT table and transponder split facility (enables the digital information of one heavily modulated transponder to be split over 2 x 8MHz channels).
  • Con: Requires QAM Decoders (not supported by Multichoice)
  • A further possibility is the re modulation into IP TV . In this method all TV and data signals are transported over the data stream.
  • Cons.: This requires a set top box with Ethernet, AV and/or HDMI output

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