GPRS, EDGE support

historical

Well, at least voice and SMS is not affected and works just great. GPRS uses only an open power control, no closed loop, maybe it has to do with this? At the moment I do not have other hardware for  comparison, so digging deeper into this may be not so useful. The issue is discussed on the OpenBTS mailing list, with no clear results at the moment.

Ralph.

From: Sipos Csaba [mailto:dchardware at gmail.com] 
Sent: Thursday, 23 January, 2014 22:01
To: Ralph A. Schmid, dk5ras
Cc: 'Don Fanning'; openbsc at lists.osmocom.org
Subject: Re[4]: GPRS, EDGE support

Thanks for the info!

At least now I know, that the GPRS/EDGE is part of the OpenBTS code, so any hardware is OK for packet data which can run OpenBTS. That is good news.

Anyway, it is just an educated guess, but don't you think your problem with GPRS is related to timing? My experience with real life networks clearly shows that even a slight timing related problem or inaccuracy can led to something like that.

My other experience is with R&S CMW500, which I used with a little external antenna and encountered the same problem. After a few meters even the voice calls started to drop with -60 RSSI. The reason was obvious: the device lacks any filters on the input chain (it is designed for production mode), and when all the received RF energy hits the receiver from all the bands, it causes problems like that. And the packet data was way more sensitive to this than voice calls. After installing proper filters, the problem is gone.

BR,

Csaba

OpenBTS supports GPRS, but at least for me it does not work very reliably, I consider this only a proof of concept. While voice/SMS range is up to 200m, GPRS breaks down after 5m (!) distance, and the connection stalls after a while, requiring a restart of OpenBTS. I am using an USRP1 with WBX board.

Ralph.

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