Satellite Backhaul History


Due to the asymmetric nature of Internet services, historically most ISP backbone links via satellite were asymmetric in nature, such as:

  • 8Mbps/2Mbps
  • 34Mbps/8Mbps

The reason for these specific rates was because satellite modems existed to support these G.703 interfaces, as they equate to E1 (2Mbps), E2 (8.448Mbps) and E3 (34.368Mbps) SDH and PDH infrastructure services which had historically been used for voice applications.

As high speed serial (HSSI) satellite modems became more widely used, these allowed asymmetric operation of satellite links that were not restrained by specific fixed data rates and could be configured in 1bps increments. Despite this added flexibility, for some time these HSSI satellite modems were simply used as an easier solution to these traditional asymmetric data rates (8/2Mbps & 34/8Mbps).

More recently it has become possible to measure usage levels and therefore the amount of bandwidth required for a given application, and to predict what future satellite capacity is required.With satellite capacity charged based on bandwidth, this has meant an increase in "odd" data rates as end users purchase only the satellite bandwidth that is required.

Typically this would be in 1Mbps increments, and so Metrodata introduced in 2000 a HSSI Module for our Access Processor platform that supported fixed rate asymmetric clocking in 1Mbps increments. This was followed in 2001 with the current HSSI Module for the Access Processor which supports 1bps increments, or can be locked directly to the satellite modems, and so we can match clocking to the satellite network, thereby offering guarantees of no bit slips, and removing any wastage of satellite capacity.

As applications have developed the flexibility of the Access Processor has made it the product of choice for backhaul solutions, and with the following satellite modem interfaces now supported:

  • HSSI (up to 100Mbps)
  • ECL (up to 100Mbps)
  • EIA530 (up to 20Mbps, to match the maximum operating speed of EIA530 encrypters)
  • G.703 - T1, E1, E2, E3 and DS3
  • ASI (up to 52Mbps)
  • RS232 (up to 256kbps)

Metrodata are the only manufacturer in the world who specialises in backhaul equipment for satellite networks and all the different common satellite modem interfaces are supported. Metrodata are also the only company that can match the flexibility of data rate of satellite modems. We also support the following modes of operation:

  • Asymmetric
  • Simplex, uni-directional with alarm masking
  • Multicast infrastructures
  • Symmetric full duplex

Often our equipment is used to backhaul over transatlantic DS3 and OC-3 circuits, but these might just as easily be local fiber optic links.

Networking The World Since 1989