scope:

This European Telecommunication Standard (ETS) defines functional blocks specific to the Digital Radio Relay System (DRRS) which use the Synchronous Digital Hierarchy (SDH) for transmitting sub-STM-1 (Synchronous Transport Module-1) rate (51,84 Mbit/s) signals.

Considering that:

- ITU-T Recommendations G.707 [5] describe the multiplexing structure for the 51,84 Mbit/s transport rate;

- ITU-R Recommendation F.750 [4] defines a synchronous Radio Relay Reference Point (RR-RP) to be used as transport capacity for sub-STM-1 SDH radio system and states that RR-RP shall not be considered a Network to Network Interface (NNI);

- ETS 300 147 [3] on SDH multiplexing structure recognizes the Administrative Unit-4 (AU-4) based STM-N multiplexing structure and does not allow direct mapping of AU-3s into an Administrative Unit Group (AUG) to form a STM-1 transport module which is on the contrary provided by ITU-T Recommendations G.707 [5] and ITU-R Recommendation F.750 [4];

- ITU-T Recommendation G.783 [6] describes the characteristics of SDH equipment functional blocks;

and also considering that: 

- ETS 300 417 [1] defines a library of basic building blocks and a set of rules, by which they may be combined to describe SDH digital transmission equipment.

This ETS describes radio specific functional blocks using the methodology specified in ITU-T Recommendation G.783 [6], in order to give a generic description of a sub-STM-1 SDH DRRS to be used within the ETSI standardized, AU-4 based, synchronous network.

This ETS defines:

- the functional blocks specific to sub-STM-1 SDH DRRS.

This ETS does not define:

- the information model for radio relay network elements;

- the protocol stack to be used for message communication;

- the network level management processes;

- the functional block specific to other systems or equipment already defined by ITU-T Recommendation G.783 [6];

- the radio specific management of performance monitoring requirements.

The equipment functionality is consistent with SDH multiplexing structure given in ETS 300 147 [3].

Equipment developed prior to this ETS may not comply in all details with this ETS.