Test 911 and E911 Emergency Services

Overview

Emergency services are the backbone of a civilized society. Police, fire, and ambulance are contacted by a single emergency telephone number.  In the US that single number is 911. In other countries, there may be a different unique number or several numbers.  In the European Union, the number is 112, in others 999, and so on. A person at a Public Service Access Point, or PSAP, usually a governmental agency/service close to the location of the emergency answers the call and dispatches 1st Responders as required. PSTN, VoIP, and Wireless carriers have developed methods for voice connection to the right PSAP and to provide accurate location data necessary for dispatch.  The above diagram shows a simplified diagram of the current 911 and E-911 network architecture. 

mainly used for emergency call services: 911 and Enhanced 9-1-1 (E-911). CAMA trunk connects a carrier switch directly to the Selective Router (SR), a special 911 Switch that in turn connects to many PSAPs (Public Safety Access Points).  PSAPs are call centers where agents answer emergency calls and dispatch police, firefighters, and ambulances.  The Selective Router routes the call to the appropriate Public Safety Answering Point (PSAP) based on the calling party’s physical location which is obtained from the Automatic Number Identification (ANI) transmitted using MF tones, i.e. the calling number.  For PSTN lines, a database lookup provides the physical location of callers against the ANI.

Call flow starts with the carrier network routing the voice call to a 911 Selective Router, which in turn routes the call to the responsible PSAP. This routing is based on an 8, 10, 20 digit # or an equivalent “key” provided by the carrier network to the 911 Selective Router. The PSAP attendant in addition to answering the emergency call also uses the 8, 10, or 20 digit # or the equivalent “key” to access many location databases - Selective Router (SR), Master Street Address Guide, or the Automatic Location Identifier (ALI) - that provide more specific location of the caller (street address, building floor, suite, latitude/longitude, etc.). The abbreviated digits/key are termed ANI, pANI, or ESRK/ESQK, depending on if the call is from a PSTN, VoIP, or Wireless carrier.

Automatic Number Identification (ANI) is an 8 or 10-digit landline caller telephone #, that in the conventional PSTN, is an index into the Selective Router (SR) database for the responsible PSAP # and the Master Street Address Guide (MSAG) database for the actual street address of the caller.  Wireless callers have no fixed location, therefore a Pseudo Automatic Number Identification (pANI) is provided.  The pANI is a code for the location of the wireless caller by cell site/sector in the Automatic Location Identifier (ALI) database. VoIP uses something similar called ESRK/ESQK (Enhanced Services Routing Key) for identifying the specific PSAP # and the caller location. Each carrier network is responsible for maintaining location data for their subscribers, updating the ALI database, and nearest PSAP #, all indexed to the ANI, pANI, ESRK/ESQK codes.

In all networks, the SR determines the correct PSAP to connect to, by interrogating databases, and completes the voice connection to PSAP attendant, via analog, T1, FGD-OS, T1/PRI, or SS7 circuits. In the analog, T1, FGD-OS connection cases, ANI, pANI, ESRK/ESQK numbers are transmitted in-band to the PSAP via MF (multi frequency) digits or Enhanced MF if more than 10 digits are required. In the T1/PRI or SS7 connectivity case, these numbers or keys are transmitted via ISDN or ISUP messaging fields.

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911 Test Requirement & Solutions

Over PSTN (Using CAMA, Analog, CAS, and FGD-OS)

Requirement

One of the major PSAP vendor wished to emulate and analyze legacy 911 Emergency calls to test their 911 elements (PSAP, 911 Selective Router) – refere to the typical 911 network main image above.

• Emulate T1 CAMA trunks with CAMA signaling for the purpose of testing 911 Selective Router and/or the PSAP side
• Emulate an analog PSAP trunk – again either 911 Selective Router side and/or the PSAP side
• Analyze T1 CAMA trunks in masse – with CDRs, signaling analysis, digit analysis, and more
• Analyze analog CAMA trunk – with CDR, signaling analysis, digit analysis, and more
• Easy set up via GUI, but also programmability to satisfy slight variations

Solution

GL’s versatile tProbe or any of our T1 E1 rack mount solution can perform all the above functionalities.

• Generate/Receive 911 Emergency CAMA calls over T1 – in bulk, and continue indefinitely
• Follow the CAMA protocol precisely -  MF signaling for “calling #”
• Be the 911 Selective Router or the PSAP end – or both simultaneously
• Generate 911 Emergency CAMA calls over analog FXO or FXS, and continue indefinitely
• Follow the CAMA protocol precisely -  MF signaling for “calling #”
• Reverse Battery
• Be the 911 Selective Router or the PSAP end – or both simultaneously
• Analyze/monitor T1 CAMA trunks for 911 calls, generate CDRs, get precise protocol exchange
• Analyze/monitor an analog CAMA trunk for 911 calls, generate CDRs, get precise protocol exchange

Required GL Hardware, Software, and Accessories

• High End Notebook PC (SA005d),
  
• tProbe T1 (PTE001) with FXO/FXS Card (PTE015)
  
• Software - MAPS FXO/FXS (PTA624), MAPS CAS Emulation (PTA651), CLI support for both MAPS products (PKS170), MAPS SIP (PKS120), RTP Core (PKS102)

CAMA Signaling Simulation and Monitoring is accomplished using GL's MAPS™ CAS Emulator and MAPS™ FXO FXS Emulator hardware and software applications. Similarly, MAPS™ ISDN Emulator  and MAPS™ SS7 Emulator can perform 911 messaging and analysis over ISDN/PRI and SS7.  All of these are strictly over a PSTN/TDM network. MAPS™ SIP emulator and PacketScan™ can perform simulation and analysis over E911 network.

GL's MAPS™ CAS Emulator and MAPS™ FXO FXS Emulator can be used to simulate CAMA trunks connected to the 911 Selective Router. Both analog and digital (T1) CAMA simulations are supported. For Analog simulation, MAPS™ CAS Emulator  requires an additional channel bank specially configured for CAMA. Also, GL's MAPS™ CAS Emulator application can be configured for emulation of 911 services.  

However, Analog CAMA type trunks can be simulated using MAPS™ FXO FXS Emulator on tProbe™ and directly connecting tProbe FXO FXS ports to 911 selective router or PSAP on CAMA-type circuits. CAMA emulation capabilities include - seizure and wink start detection, onhook and offhook detection and MF digit (ANI) generation/detection. MAPS™ FXO FXS Emulator also supports FXO monitoring of CAMA type trunks, where the tProbe™ FXO port is tapped onto CAMA-type circuits for non-intrusive monitoring of 911 service. Monitoring capabilities include seizure and wink start detection, onhook and offhook detection and MF digit (calling party ANI) detection.

Drive Test Voice, and Data Services for Quality (Emergency services)

The Wireless Drive-Test solution includes GL’s VQuad™ with Dual UTA HD supporting call control of variety of mobile device networks – from 2G to 5G, including the capability of sending/recording voice, testing video conferencing, and testing a variety of data over the mobile devices, while analyzing their performance.

A GPS option permits time synchronization between two geographically separated systems as well as location information for drive testing. With an added wireless network connection, all functionality can be remotely controlled, and all results transmitted to remote locations can be accessed on-the-go. You can simply load configurations and start/stop the tests, grab test results and stream files to the command center locations.

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