Interfacing G.703 / COAX


Metrodata offer products that operate at fixed rates such as Nx64kbps, E1, T1, E2, E3, DS-3 and OC-3 and provide serial conversion to G.703/coax/BNC or fiber.

Metrodata also offer solutions to work at flexible or "odd" data rates such 9.123Mbps or 266.67kbps converting to G.703 or fiber using the Access Processor.

Despite the fixed rate implementation of G.703 satellite modems, there are still numerous applications that exist for them. The most common application that Metrodata see is for G.703 to HSSI conversion, where the client wants to connect the G.703 satellite modem to a HSSI router port, since HSSI router interfaces are typically cheaper and more flexible to use than G.703 interfaces.

Metrodata developed the first HSSI to 8Mbps G.703 converter in 1994 for Intelsat, the FM4850. Intelsat had received one of the first Cisco HSSI routers [4000 series] and wanted to use it with their G.703 satellite modems. This application is covered in the Intelsat document on Internet Over Satellite, called ITLAN-003.

There are plenty of ways of interfacing G.703 satellite modems, as follows:

  • G.703 satellite modem at 2.048Mbps to X.21 router - DC1000
  • G.703 satellite modem at Nx64kbps to X.21 or V.35 router - FM4000
  • G.703 satellite modem at 8.448Mbps to HSSI router - FM4850
  • G.703 satellite modem at 34.368Mbps to HSSI router - DC3445, FM4900
  • G.703 satellite modem at 44.736Mbps to HSSI router - DC3445, FM4950
  • Asymmetric G.703 satellite modems to HSSI router - e.g. typically 34.368Mbps and 8.448Mbps - FM4900 & FM4850
  • G.703 satellite modem at 2.048Mbps to Ethernet - WC1000
  • G.703 satellite modem at 34Mbps to Ethernet - WC3445
  • G.703 satellite modem at 45Mbps to Ethernet - WC3445
  • G.703 satellite modem at various speeds to ATM - Access Processor

Another area where G.703 fixed rate interfaces are widely used is on ATM Switches. For example you might have an E2 8.448Mbps satellite link and need to connect it into an ATM Switch. There are very few [if any] ATM switches other than the Metrodata Access Processor that support E2 interfacing, which Metrodata developed for Stratacom, to allow the connection of their DS3 ATM equipment to E2 8Mbps G.703 leased line services. The Access Processor range is a modular chassis that supports many other interface options, and allows the convergence of multiple disparate applications.

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