Direct Mode - Background

Overview of Direct PP to PP communications
Contributed by Dag Akerberg
Chairman ETSI DECT Project Team A

The direct PT-to-PT communication was introduced in the second edition of the DECT CI standard (EN 300 175-6) during 1996, and in TBR06 (second edition)1997.

EN 300 175-6 described an ARI (access rights identity) class E, which allowed adhoc networking between PPs belonging to a group of up to 100 PPs. All PPs belonging to a networking group shall enter a common random 3-digit group number + a unique member number (00 to 99). Bearer set up in made directly between pairs of PPs where the initiating PP switches over to RFP mode and pages the wanted PP.

TBR06 (second edition) describes the allowed PP carrier stability value for PPs acting as RFPs, and also describes some procedures including timers. (The PPs in a direct PP to PP group are allowed to be frame synchonised to a local FP, but this is not required). Furthermore, it is not required to use the class E ARI, other identity types are allowed from TBR06 perspective. When using ARI class E, the paged PP shall make bearer setup on the duplex bearer where it has been paged. In this way a PP in RFP mode does not need to do receiver scanning nor to send blind slot information.

In the latest edition of the EN 300 175 standard, the ARI E is still in part 6, the setup procedures are in part 3 annex G, and the TBR06 has been substituted by the DECT Harmonized standard EN 301 406.

To provide interoperability, the PP to PP communication mode has to be defined in a Profile, where proper selection of available options is stated.

Distributed communication was introduced first in the summer of 1998 as part of the draft EN 301 650 DMAP (called at that time MMAP). Later on in 1998 the initial proposal was re-written and was introduced to the EN 301 649 DPRS (DECT Packet Radio Service) during 1999. The final version was published in early 2000.

Currently the distributed communication protocol requirements are part of the EN 300 175-5 v 01.05.00 Annex I, and special section on how this should be supported in regard to DPRS is included in EN 301 649 clause 13.