nanog mailing list archives
Re: London incidents
From: Iljitsch van Beijnum <iljitsch () muada com>
Date: Mon, 11 Jul 2005 12:19:10 +0200
On 11-jul-2005, at 11:40, Michael.Dillon () btradianz com wrote:
I had moved the weekend before and my landline was not yet installed. Also, I live near a large hospital. I noticed that my mobile didn't function at all even late on Thursday unless I left home and travelled a kilometer or two from the hospital. Presumably, the cells in this suburban location had also been switched to emergency service.
A hospital using up "emergency mode" GSM capacity doesn't make much sense to me. You're not supposed to use cell phones in many places in hospitals, and the ones that I've seen have an ample supply of fixed lines that are cheaper, more reliable and pose less risk of interference with the equipment.
It's probably just congestion. Cellular networks don't come close to being able to absorb the burstiness of the (potential) usage patterns in situations like this. (The bean counters don't like cell towers that are idle 99% of the time.) When all the time slots on all the sites in range are filled up you can't get through with voice or data, but SMS which just uses signalling still works. When it gets really bad the random access channel gets clogged and all mobile- intiated communication, including SMS, is dead in the water.
(The random access channel is the one not under control of the network: handsets use it to signal their desire to communicate. As such, it is very prone to collisions and congestion collapse under heavy loads.)
Current thread:
- London incidents Neil J. McRae (Jul 07)
- Re: London incidents Brad Knowles (Jul 07)
- RE: London incidents Neil J. McRae (Jul 07)
- Re: London incidents Gadi Evron (Jul 07)
- Re: London incidents Sean Donelan (Jul 09)
- Re: London incidents Spencer Wood (Jul 11)
- Re: London incidents Sean Donelan (Jul 09)
- <Possible follow-ups>
- RE: London incidents Fergie (Paul Ferguson) (Jul 07)
- RE: London incidents Michael . Dillon (Jul 11)
- Re: London incidents Iljitsch van Beijnum (Jul 11)
- Re: London incidents Michael . Dillon (Jul 11)
- Re: London incidents Iljitsch van Beijnum (Jul 11)
- Re: London incidents Jay R. Ashworth (Jul 11)
- RE: London incidents Michael . Dillon (Jul 11)
- RE: London incidents Neil J. McRae (Jul 11)
- Re: London incidents Brad Knowles (Jul 07)
- Re: London incidents Robert E . Seastrom (Jul 11)
- Re: London incidents Steven M. Bellovin (Jul 11)
- Re: London incidents Robert E . Seastrom (Jul 11)
- Re: London incidents Scott W Brim (Jul 11)
- Re: London incidents Jay R. Ashworth (Jul 11)