[asterisk-users] OT - Is handover included in DECT GAP ?

[Robert Lister]

On Thu, Jan 10, 2008 at 11:22:29AM +0100, Olivier wrote:
> Hi,
> 
> Do you if a DECT-GAP (or DECT-CAP) compliant handset MUST or MAY support
> roaming and handover and are these functions transparent for handset (then,
> these functions are implemented in DECT base stations) ?

Yes. It is a capability of the handset, where, as the user is moving about, 
the handset is continually scanning for the best channel/frequencies 
available from the base station. If a better signal than the one the user is 
currently using becomes available, (perhaps they have gone into a different 
room or moved behind a tree etc. meaning the current channel is weaker, then 
the handset will switch to using the better channel during the call.)

There are a few systems out there that support multiple base stations which, 
to the handset, all look like the same registered base. (i.e, the handset 
only registers/authenticates once with the system (and not every base 
station) and then as the user moves about the handset, by virtue of always 
looking for the best channel, will hop from one base to the next. It does 
require that the system in the middle manage the database of registrations 
etc.)

I've seen such capability on Siemens HICOM and Bosch PBXs, for example. All 
the DECT base stations are wired back to a central card in the system.
 
I don't know if there is a standalone DECT IP offering supporting similar.

The timing/clocking to support seamless roaming between the base stations is 
complicated and has to be very precise, so I imagine that such a system 
would need to have one central controller (and the SIP gateway function) 
with DECT base stations all wired out from there, rather than lots of 
independent DECT bases with Ethernet, that talk to a central unit over IP 
and somehow hand off the call.

So to span multiple buildings you would probably need dedicated copper pairs 
or fibre to connect in the remote base stations to the central system. 

That is certainly the way it worked when I was last tinkering with DECT 
stuff. Although the Siemens switches could have multiple remote shelves 
connected over fibre to different buildings, the DECT bases all had to be 
connected via copper cables (and be powered on by) a central card in the 
main shelf, and could not be connected to a card in a remote shelf. (Or, you 
could have multiple PBXs and handsets roaming between different systems, but 
that starts to get expensive for maybe 10 users!)

I have some detailed specs on it somewhere if you want more technical info.

Rob