Chapter 13 - Emergency Calls on the Internet pptx

Chapter 13

Emergency Calls on the Internet

13.1 Introduction

This chapter is devoted to the complex topic of IP-based emergency calls. What makes IP￾based emergency calls a complex issue? First of all, an emergency call needs to be routed

to the closest Public Safety Answering Point (PSAP). This requires the call to be routed to

the PSAP based on the caller’s location, which in turns requires the caller’s location to be

determined roughly. Furthermore, it also requires a mechanism to translate the location into

the real URI of the PSAP. All of these issues make IP-based emergency calls complex in

comparison with regular IP-based calls using SIP.

There are three different types of emergency communications, of which this chapter

covers just the first.

Citizen-to-authority communications. This type of communication refers to users dialling

an emergency number, such as 112 in Europe or 911 in the USA. Usually these are

referred to as emergency calls.

Authority-to-citizen communications. This typically refers to national emergency centers

broadcasting alerting information related to emergency situations. For example, in the

case of a rough weather condition, such as a hurricane or a tsunami, an alert can be

issued to the population providing instructions for their safety. In some cases, this

type of emergency communication may require warning messages or instructions to be

launched to all citizens or a group of them who are located in a determined geographical

area, e.g., where a disaster has taken place.

Authority-to-authority communications. This refers to the type of communication that

takes place between two authorities during an emergency situation. This might be

the communication that takes place between a national emergency coordination center

and the police, fire brigade, or hospitals. Typically, this type of communication has

higher priority than the rest of the calls, and it might pre-empt existing calls.

When users want to make an emergency call, they simply dial the local emergency number

(e.g., 112, 911), and the call is connected to the closest emergency center, which will dispatch

the requested emergency service (e.g., an ambulance). This process is simple from the user’s

point of view, because the user just needs to dial the local emergency number. However, the

process can be split into the following building blocks.

ıa- ´ Martın´

The 3G IP Multimedia Subsystem (IMS): Merging the Internet and the Cellular Worlds Third Edition

Gonzalo Camarillo and Miguel A. Garc

© 2008 John Wiley & Sons, Ltd. ISBN: 978- 0- 470- 51662- 1