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Innovation Briefing Issue 9 | Calling 999

  • 5 minute read
  • Published by Crispin Moller on 20 Jun 2022
  • Last modified 8 Jun 2022
A 999 call is a call like no other. Its special nature means mobile operators have to handle it in a distinct way. Any mobile network offering voice services needs to comply.

September 9th is 999 day. It celebrates the emergency services. The three digits have been baked into the British psyche since a house fire in 1935 led to the service being established.

The pan-European standard of 112 also works, but to most people it’s 999 which is special.

And it is special. It’s a number which comes with legal obligations for the mobile networks.

You can call 999 from a phone with no credit. In other parts of the world you can even call without a SIM card, but the UK operators declined the invitation to support this.

There are some devices which have a method for automatically triggering an emergency call. Doro mobile phones, aimed at the older generation and the Buddi fall sensors and Lone Worker protection phones make calls to a predefined number when a button on the back or a fall is detected. This can be to any number, and the recomendation is not to use the emergency number as it can lead to false calls, but people often choose to use 999 as one of the numbers in the call list.

All 999 calls are answered by BT, even those through Vodafone, Three and Virgin Media O2.  When a phone user calls 999 the network identifies it as an emergency call and bypasses the usual authentication and billing systems. All 999 calls are free and the cost is borne by the mobile network. BT bills the operator for the call handling.

A map indicates where the call is coming from. This can be a general as the area covered by the cell site, or more accurate, thanks to Advanced Mobile Location technology, which uses the GPS in a smartphone to locate the call down to a few metres.

As part of the call routing the mobile operator needs to append five digits to the number passed to the emergency services. The first two digits define the mobile operator and the next three the location. So 503 is Cambridgeshire, 514 is Greater London and 579 is Orkney.  These are based on administrative areas rather than the size or population covered and are different for the different operators.

The administrative area is used to determine which Emergency Service centre receives the call. The receiving centre. Once the call arrives, the emergency centre systems interrogate the mobile networks’ Mobile Operators Location Enabling Server, or MOLES, using the mobile number to retrieve the location of the user. This determines where the user is by knowing the base station the handset is connected to. When the emergency call is made the network requests the location information from the handset. It’s a comprehensive database. It may contain information on where small pico cells are located in a building, or information about the device, such as whether it has GPS capability. It may have subscriber information such as their home address. Whenever a new cell site is installed the system at the emergency services centres needs to be updated with the site location.

All this is designed to give the call handler as much information as possible when the call is connected. To provide this, the mobile network operator needs to work closely with BT. It needs to be issued with an identification number, known as an II, and have a secure server connected to the BT system.  Dedicated IP addresses need to be established and exchanged.

A contract with BT Wholesale is necessary for this arrangement to be made and paid for. This means that a private network, in say a university campus which does not buy any other services from BT will nevertheless need a logistically challenging agreement if only to cover the emergency calling.

There is an obligation on the part of the operator to test the connection. When the major MNOs connect a new cell they will test each sector with a 999 call. The field engineer doing the testing has special permisison and a script for working with the call centre.

If this seems complicated, that’s just the voice services. There are different classes of data services.

Text messaging to 999 must also be supported, for use in a situation where the person in trouble is unable to speak. The 999 SMS service requires registration, so it’s vitally important that you know ahead of time that you are likely to be held kidnapped in a bank robbery before the incident occurs.

A more recent addition to emergency calling is eCall. This allows your car to call for help in the event of an accident. Standard on all new cars sold in the European Union since April 2018, the system reacts to actions such as the airbags being triggered and reports the accident. Again a private network such a university campus may need to support this too.

Support for 999 isn’t just an obligation.It’s something that makes people feel good about having their mobile with them. When many people associate their mobile network with call drop outs, unexpected bills and long waits for customer service, it’s something that makes people feel good about their mobile operator. 

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