Open source strategy
One of the main objectives of EMYNOS is to produce some open-source working prototypes for next generation emergency services supporting unified communications through open standardized protocols and architectures (e.g. SIP, IMS). The EMYNOS open source strategy aims at enabling users/developers (industry, academia) to test their Next Generation emergency services solutions or to develop emergency applications on top of the EMYNOS framework.
Development on a solid basis
In developing the IP based emergency support, the EMYNOS consortium has chosen (and extended) well-known and stable software components among the ones already existing in the open source VoIP area. For instance, Linphone has been extended to initiate emergency calls, Kamailio which is a SIP proxy being used by a lot of VoIP providers, has been extended to behave as an ESRP, and Asterisk which is a well know PBX software has been extended to handle calls in the PSAP.
Interoperability and collaboration building
It is important to mention that most of the EMYNOS components being made open source were also tested successfully against industrial solutions. This was achieved through the participation of the EMYNOS consortium to the consecutive ETSI NG112 plugtests™ events in 2016 and 2017.
NG112 and NG911
Although the EMYNOS implementation has been targeting NG112 (Next Generation Emergency Services in Europe), this implementation can also be used in the context of NG911 (North America. For more details, we refer to the specifications documents EENA NG112 LTD and NENA i3 architecture.
The VoIP software Linphone is extended in the context of EMYNOS as follows:
- Initiating emergency calls with audio/ video/ real-time text
- Supporting emergency URNs
- Supporting several location configuration protocols (DHCP, HELD, LLDP-MED)
- Accepting emergency calls and visualizing location information
Interactive Voice Response system (IVR)
The IVR is used, for instance, in case all the call takers are busy. It is based on the Asterisk VoIP software. Here, the emergency call is forwarded to an IVR system where an audio file will be played and an Instant Message (with necessary information to be used by the caller) will be sent to the caller’s VoIP client.
Emergency Support for the IP Multimedia Subsystem (IMS)
The IP Multimedia Subsystem (or shortly IMS) is the key enabler in the mobile world for providing rich multimedia services to the end-users. It was standardized by the Third Generation Partnership Project (3GPP) (IMS Release 6) and uses the IETF standard (SIP) for session management. Although originally designed for mobile networks, IMS has been considered as a core component for NGN fixed networks. This vision is supported by the standardization bodies 3GPP, ETSI TISPAN and 3GPP2/LTE. The IMS architecture specifies three layers,
- Transport or Access layer: responsible for media processing and interaction with end systems
- Control (or IMS) layer: responsible for registration and SIP signaling routing
- Service or Application layer: hosting the call control applications and Value Added Services (VAS)
The objective of 3GPP was also to develop the necessary elements to enhance IMS with the support of emergency services while using as much as possible the protocols specified by IETF. The 3GPP work about emergency services was decomposed into several stages and described in corresponding documents: 3GPP TS 22.101 (for the requirements), 3GPP TS 23.167 (for the architecture), and 3GPP TS 24.229 (for the protocols and interfaces). For more details, we refer to these documents.
The architecture of the emergency services support for IMS is depicted in the figure above. Two main components were added to the IMS framework: (1) the Emergency CSCF (E-CSCF) which is the entity in charge of routing the emergency requests to the appropriate PSAPs, and the Location Retrieval Function (LRF) which is in charge of retrieving the location information of the user’s terminal that has initiated an IMS emergency session. For more details, we refer to the 3GPP document TS 23.167.