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.
This was just a guess on my part because the congestion in this suburban area lasted well into the evening. The only time I was able to make phonecalls on my mobile was when I took a bus out of the area. I planned to travel away from the city to get away from mobile congestion but the phone started working again before I had gotten any further from the centre. However I had moved a km or two from the hospital. Later, I returned home and lost the ability to use the mobile even as late as 11:30 p.m.
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.
This, I understand. But it doesn't explain why this area would have suffered such a prolonged problem.
When it gets really bad the random access channel gets clogged and all mobile- intiated communication, including SMS, is dead in the water.
I never had a problem sending or receiving SMS other than the long delays. The people on the other end were near Aldgate on the edge of central London so even there, SMS was still functioning. It was an interesting experience which seems to show that it is better to have several completely different communications channels to choose from. In my case I had lost landline and DSL Internet access due to moving house, and I lost mobile voice access due to congestion. But SMS still functioned. I haven't heard of any Internet outages caused by the attacks although everyone who has travelled on the tube knows that there are lots of cables in the tunnels. Presumably, there are so many tunnels with cables that breaks in three places are easily covered by protection switching. --Michael Dillon