999 / 112 / 911

Dear, Lyle!
As I know (from en.wikipedia.org/wiki/MTPAS), MTPAS differs from ACCOLC only by organisation procedures (On what level decision is taken) and more flexible assignment of access class on local level. MTPAS and ACCOLC are British internal procedures, based on standard GSM Access Class Control.
MS Access Class is stored on SIM and I am doubting that all British people want to re-programme their SIM (more so this hardly possible). And if however 1-2 malicious subscribers will preprogramm SIM, it not will cause a global network congestion.

Also in UK operators use part of IMSI to identify subscriber’s Access Control Class to prevent accidental or malicious alteration of the data in SIM EFACC allocation.

Lyle, ACCOLC and MTPAS are British internal procedures as Pan mentioned.

ACCOLC (Access Overload Control) is being phased out in 2009. Where the ACCOLC event occurs the cell and necessary surrounding cells are taken out of use to deal with emergency. 999 or 112 calls MIGHT still be made isf the a mobile phone is “within radio range” of other cells not affected by the ACCOLC is imposed. ACCOLC is not a radio dampening procedure it merely prevents access to the network using network blocking of unprioritized non-ACCOLC register
SIM users. Also the Access Control Classes 0-9 and 11-15 were more emphasized. Also certain types of emergency were assigned Gold Silver and Bronze Command authority and priority. Read: (en.wikipedia.org/wiki/Gold_Silver_Bronze_command_structure), how this authroity comes from a centralised authority and then implemented locally.

MTPAS (Mobile Telecommunication Privileged Access Scheme) is similar to ACCOLC but priority is given to privileged users as opposed to ordinary (unprivileged users). Unlike ACCOLC, a MTPAS cannot disable the network but increases resources to MTPAS privileged users. But 999 and 112 calls can still be made by unprivileged users in parallel to an MTPAS event happening.
The network is left to implement MTPAS the best way possible. Gold Commander actions MTPAS events with the network at the local level.

For US issues for 911 look to: (en.wikipedia.org/wiki/P25) and
(en.wikipedia.org/wiki/Enhanced_911)

Additional to Pan, I check a ‘UK’ emergency response how MTPAS stated in manual for local level emergency. It say:

2.3.1 Mobile Telecommunications Privileged Access Scheme (MTPAS)
MTPAS (previously Access Control Overload- ACCOLC) permits the major mobile
phone companies to reserve exclusive channels for use by the Emergency Services
and Local Authorities in the event of a major incident. However it should be noted:
• The facility is rarely invoked and is very expensive.
• Decision to activate MTPAS is made by the mobile phone companies on the
request of the Police only.
• MTPAS would only be activated for limited ‘cells’ normally the immediate vicinity
of the scene of the incident.
• Facility disrupts normal subscribers who may be involved in the incident and need
to contact emergency services.

The last point under 2.3.1 say ‘disrupt’ meaning affects (stops) contacting emergency services (999/112 calls) when MTPAS deployed on cells.

Pan you made me laugh with what you say 🙂