ETSI - PRETS 300 234
Transmission and Multiplexing (TM); High Capacity Digital Radio-Relay Systems Carrying 1 x STM-1 Signals and Operating in Frequency Bands with About 30 MHz Channel Spacing and Alternated Arrangements
|Publication Date:||1 January 1992|
This ETS specifies parameters for digital radio-relay systems with a channel capacity of 1 x STM-1 designed to operate in defined bands up to 15 GHz utilizing approximately 30 MHz between adjacent cross-polar channels.
The parameters specified fall into two categories:
a) those required to provide compatibility between channels from different sources of equipment on the same route, connected either to separate antennas, or to separate polarizations of the same antenna. This category also includes parameters providing compatibility with the existing radio-relay network;
b) parameters defining the transmission quality of the proposed systems.
The task of defining compatibility requirements with analogue and digital systems on the same hop and at nodes is made complex by the fact that analogue systems and some digital systems are not standardized. Compatibility requirements are, therefore, limited to allowing the operation of digital and analogue channels on separate ports of the same antenna.
The standardization concerns two different levels:
- the first deals with Intermediated Frequency (IF)/Radio Frequency (RF) characteristics and BaseBand (BB) characteristics relevant to Synchronous Digital Hierarchy (SDH);
- the second could concern other BB characteristics. Diversity system specification and antenna/feeder system requirements are also considered.
Two possible BB interfaces need to be considered:
- one for Synchronous Transfer Model-level 1 (STM-1) signals; and
- another for 140 Mbit/s signals.
The 140 Mbit/s signal should be carried "open-port", i.e. in a transparent manner independent of their content. They should be mapped into a 155 Mbit/s STM-1 signal as described in CCITT Recommendations G.708 and G.709.
With regard to the STM-1 signal, Section Overhead (SOH) processing should be envisaged. In particular, the SOH bytes reserved for future international standardization are proposed to be used for:
- medium-specific functions;
- wayside traffic.
Details are to be covered by the work within ETSI STC-TM4 SI/TM-4009: "Impact of Synchronous Digital Hierarchy (SDH) aspects on Digital Radio Relay Systems (DRRS)" and the CCIR Recommendations 750  and 750 .