By: Mark J. Fletcher, ENP
Chief Architect Public Safety Solutions – AVAYA
In PART Two of this blog, we discussed the Emergency Call
Network, that segment of the PSTN dedicated to emergency calling and connecting the PSAPs together on a regional basis. In this section, we’ll cover the mobility that modern networks provide to Enterprise users, and clearly one of the most challenging pieces of information for 9-1-1 call takers to obtain.
We learned that the Selective Router in the E911 Tandem office was responsible for connecting callers to the right PSAP. That decision is made based on the Caller ID presented with the call. Initially, this was a very valid best practice, as the network was well documented, and changes were well controlled and performed by the service provider.
One Number – One Address
Telephone numbers rarely were co-located in multiple locations (with a few
exceptions) therefore the telephone number was an excellent data point usable for determining the location of a device, and the network was designed around this fact. In the mid 80’s, the Northern Telecom DMS 100 was introduced as a digital central office platform, and AT&T introduced the ESS 5 with similar capabilities.
With these new digital switching platforms, the layout inside the Central
Office radically changed from one that was mechanical stepper-motor-based to one that used a digital switching matrix, and with this automation fewer and fewer CO’s were staffed with technicians, as the building role became merely a wire center with a cross connection point for dial tone to street pairs. With the digital evolution these switches brought was a new series of custom calling features.
A Star is Born
Customers did however get some very new features, like Caller ID and feature ‘STAR-codes.’
Missed a call? Dial *69 to be connected with the last number that called. *72
along with a telephone number would forward any calls to the new destination, and depending on the services provisioned in the CO, various other features became available to customers. Many of these features took advantage of Caller ID information that was now available with the call. For the very first time, the called person could know the identity of the caller displayed on their telephone device. Caller ID (better known as Automatic Number Identification or ANI) now provided 911 centers with information about who was calling, or at least the number they were calling from. Now, if a silent call came in, or there was a question about the address and location, the original color could be easily reached. 911 centers also played games with the electrical properties on the phone lines, and it was common practice not to pass any answer or disconnect supervision from the PSAP. This providing for a simple way to keep the line open simply by
not hanging up on the public safety end.
Location, Location, Location
Without a service address, it’s impossible to send any help at the time of an
emergency. To solve this problem, 911 centers begin taking the ANI (phone
number) they were receiving with calls, in making a query back into the carrier network database that routed the call. This ALI Automatic Location Information added location to the context for wireline calls, however the cellular industry didn’t catch up, and continued to report only Phase 1 location information, which was the latitude and longitude of the radio tower the cell phone happened to connect through. With the white density of cell towers, compared to today, the effective service areas were quite large spending several miles. When cellular towers were installed on mountaintops they often lined up with political borders, once again exasperating the location problem if you’re located across the state lines hitting a remote tower due to height and proximity. This problem remained for many years, and only began to be solved as devices started to contain GPS radio receivers, but there was still an underlying problem at the network layer level.
Can You SEE Me Now?
As the density and placement of cellular towers increased, Basic radio
coverage and interoperability became commonplace. Carriers started to
interoperate with each other, and cellular handoff became a commonplace feature spanning the entire coast. Making a call with simple, but making a 911 call remained problematic. Don’t get me wrong, calls could be received and routed quite simply, however since the 911 network is a legacy analog based network, and no data channel exists to pass information on, 911 centers went into making a query to the cellular carrier asking them what visibility was available out of their network. Despite the device itself having an excellent location awareness, due to Wi-Fi fingerprints, access points, cellular towers, as well as a GPS signal when outside, the location of you what is the network looking in, and what the device had (known as handset-based location accuracy) was simply unavailable to the PSAPs, and no mechanism existed to communicate anything other than a voice path between the caller and the call taker.
Google Can Find Me . . .
Yes, I am well aware that Google, Domino’s Pizza, and a plethora of other
services are you able to locate your cellular device with incredible accuracy; in the first responders at 911 that are trying to save your life, cannot. The primary reason behind this is that because the device is utilizing an application. Also, the application has access to the device-based location information held in the memory. This particular location information uses all of the data points that we discussed earlier, and that information is communicated back over the Internet to the host application. Once again, this is where the train goes way off the rails.
The information that is contained within the device is like having a trans-Atlantic Ocean liner that is landlocked in a lake in the middle of Kentucky. Regardless of the level of luxury, the number of passengers it holds, or the amazing abilities contained within the ship, without any use cases or access to the ocean, you’re going to have a rusting pile of steel in just a few years.
Unfortunately, this is the exact state at our Legacy PSTN network exists in
today. Consumer-based technology, the information age of the Internet, and the digital transformation that has occurred in commercial businesses, have connected the world at levels never before conceived. The devices we carry our hands and our pockets, are capable of blinding fast speeds and connectivity levels never dreamed of before. I can call, I can video, I can text, and I can email anyone on the planet; except 9-1-1. My daughter, halfway around the world on a beach in Waikiki with her boyfriend can transmit real-time high definition video from her handheld device to my handheld device 4,882 miles away with practically zero latency, but if she had a medical emergency and needed help, she would be stuck with a voice call and location inaccuracy about half mile or more if she called 911.
In any commercial enterprise space, despite be vast amount of digital
information we have available about the emergent event, the situational
awareness about the emergency, or even lifesaving information about the caller, no matter what the technology is at the origination point, the network in the receiving agency are relegated too low fidelity text based information. Why? I’m not sure I’ve gotten a good answer to that . . . . yet. But I know a few young entrepreneurs that took the problem head-on, and drove a paradigm shift change in an industry that was half a century old and very much stuck in its ways.
In Part Four of this series, we will dive into over-the-top applications, that
utilize the Internet in the open connectivity that exists nearly everywhere to take a short cut around the technology roadblocks that lay between citizens who need help, in the public safety first responders that can provide that help.
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