Radio link

Current radio links are either E1 connection (European 1st order multiplex) with speed 2048 (ITU G.703) Mbps or 1920 Mbps (ITU G.704).

G.703 is the raw frame of 32 slots of 8kbps @ 8kHz repeat frequency (being 256 bits sent with 8 kHz timing (per 125 µs).

In G.704 two slots are used for signaling (slot 1 and slot 16 -> is still from digital telephony where slot 16 is used for signaling the 30 telephone channels) and slot 1 for error indication. As a result, 128kbps are lost. But even G.704 with 30 slots (instead of 32) has a sufficiently high speed for ETI transport.

The current services (point-to-point E1 connection) are no longer delivered over PDH networks (PDH Plesiochronous Digital Hierarchy) but are implemented and delivered over a SDH fiber network (SDH Synchronous Digital Hierarchy) or over an E1 jet link.

Regarding beam links, one sees more and more E1 emulation over IP links. That is, the beam connection is an IP connection over which E1 is emulated. Which reduces back everything to an IP connection.

An E1 interface can be done in two ways:

  • 75 Ohm BNC connector
  • 120 Ohms twisted pair connection over RJ45 connector (CAUTION: different wiring than Ethernet cables