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FCC E911 Requirements for Providing Mobile Phone Geographic Locations
From Wikipedia, the free encyclopedia

Requirements
The U.S. Federal Communications Commission (FCC) has several requirements applicable to wireless or mobile telephones:[3]
Basic 911: All 911 calls must be relayed to a call center, regardless of whether the mobile phone user is a customer of the network being used.
E911 Phase 1: Wireless network operators must identify the phone number and cell phone tower used by callers, within six minutes of a request by a PSAP.

E911 Phase 2: 95% of a network operator's in-service phones must be E911 compliant ("location capable") by December 31, 2005. (Several carriers missed this deadline, and were fined by the FCC.[4])
Wireless network operators must provide the latitude and longitude of callers within 300 meters, within six minutes of a request by a PSAP.[5] Accuracy rates must meet FCC standards on average within any given participating PSAP service area by September 11, 2012 (deferred from September 11, 2008).[6]

Location information is not only transmitted to the call center for the purpose of sending emergency services to the scene of the incident, it is used by the wireless network operator to determine to which PSAP to route the call.


Technology
A second phase of Enhanced 911 service is to allow a wireless or mobile telephone to be located.

To locate a mobile telephone geographically, there are two general approaches. One is to use some form of radiolocation from the cellular network; the other is to use a Global Positioning System receiver built into the phone itself. Both approaches are described by the Radio resource location services protocol (LCS protocol).

Radiolocation in cellular telephony uses base stations. Most often, this is done through triangulation between radio towers. The location of the caller or handset can be determined several ways:
Angle of arrival (AOA) requires at least two towers, locating the caller at the point where the lines along the angles from each tower intersect.

Time difference of arrival (TDOA) works like GPS using multilateration, except that it is the networks that determine the time difference and therefore distance from each tower (as with seismometers).
Location signature uses "fingerprinting" to store and recall patterns (such as multipath) which mobile phone signals are known to exhibit at different locations in each cell.

The first two depend on a line of sight, which can be difficult or impossible in mountainous terrain or around skyscrapers. Location signatures actually work better in these conditions however. TDMA and GSM
networks such as T-Mobile 2G use TDOA.[7] AT&T Mobility initially advocated TDOA, but changed to embedded GPS in 2006 for every GSM or UMTS voice-capable device due to improved accuracy.

Code division multiple access (CDMA) networks tend to use handset-based radiolocation technologies, which are technically more similar to radionavigation. GPS is one of those technologies. Alltel, Verizon Wireless, T-Mobile 3G, and Sprint PCS use Assisted GPS.[7]

Mobile phone users may also have a selection to permit location information to be sent to non-emergency phone numbers or data networks, so that it can help people who are simply lost or want other location-based services. By default, this selection is usually turned off, to protect privacy. In areas such as tunnels and buildings, or anywhere else that GPS is not available or reliable, wireless carriers can deploy enhanced location determination solutions such as Co-Pilot Beacon for CDMA networks and LMU's for GSM networks.
Note: Italics and bolding added for emphasis by Webmeister.

http://en.wikipedia.org/wiki/Enhanced_9-1-1

True and False!

Several Urban Myths perpetuate perceived problems with the use of cell phones for emergency communication in the backcountry:
1. Your emergency call to 911 may fail because it may go to the wrong 911 call center. Wrong, these 911 call center folks are smarter than that!

2. Not all cell phone service providers maintain 100% "location capability". True, but the 95% compliance required since 1995 is pretty good!

3. The geographic locations are unreliable and can be way off. Partly true, but most locations in practice, are within shouting distance!

4. The cell phone battery may fail. Partly true, but if the backcountry traveler is informed, the freshly charged battery, kept warm in a pants pocket, will last for hours. If companions all carry their own personal common cell phones, this is false concern!

5. The cell phone is a "yuppie 911 device" and it is immoral to carry it in the Wilderness. False, the ordinary cell phone can help take the Search out of Search and Rescue! This myth may have caused the deaths of many individuals since the original article went viral. Deschutes County Sherriff's Search and Rescue volunteers note that "searches are down and rescues are up" with the advent of new technologies.

6. You can call 911 from any cell phone. False, if your cell phone can not "see" cell towers, it can not connect. Example: Verizon has CDMA cell tower coverage of most of our local Three Sisters Wilderness and GSM cell phones can not see the towers. Do you have a GSM technology based cell phone?

7. My plan has roaming coverage with Verizon, so I can call 911 from all locations in the Three Sisters Wilderness. Wrong, see #6. above.

8. I pay monthly for a navigation application in my phone. It works great in Bend! It shows detailed topography and trails in the backcountry. Wrong, navigation programs are designed for cars and motor homes, not for hikers. Your phone customer service sales person may have never seen a USGS 1:24,000 Quad topo map. "He who knows naught, knows not that he knows naught."

9. A cell phone takes the place of a SPOT-2 GPS Satellite Messenger. False, Read More.

10. More soon!

The rest of the story

Deschutes County Sheriffs Search and Rescue Volunteer Coordinator Al Hornish, a 12 year veteran of DCSAR, stated the following in an interview published on January 26, 2012 in the Bend Oregon Source Weekly: "We have grown a lot over the past decade." "The nature of missions has changed as well. There are more Rescues and less Searches, mostly because of the better technology available." Read More. --Robert Speik, January 26, 2012

FIFTEEN WEEKS
Wednesday, July 7, 2010, or nearly four months since my fall off Mount Temple. After so much time, there is much to dwell on. The negatives: the pain of so many fractures, the sleeplessness, the drugs and the messed up things they do to you. It’s easy to get stuck in the negative; yet some part of me is drawn there by some morbid fascination.
How big am I then? Not very. I made a mistake, a pretty small mistake. Or more honestly, I made a series of pretty small mistakes. I almost died for these transgressions. I would have died if it had not been for a cell phone and the chain of events it was able to put into motion. (I’ve owned a cell phone for barely six years.) I might not have died that very day, March 25, 2010, but from where we were, we were a long, long way from the medical care my injuries demanded: a trained trauma surgeon in an Emergency Room. Perhaps I would have lasted one night. Maybe not. It changes my perspective about what a day means. Carpe diem no longer seems some frat-boy cry to party. Today, means everything.  The Steve House Training Blog

Deschutes County Sheriff's Search and Rescue Deputy Jim Whitcomb, assistant SAR coordinator reports on a recent 911 "false alarm". He notes that the inadvertent activation happened in a pack with an older SPOT-1 device. Whitcomb said it was a first-generation version that’s easier to accidentally set off while in a pack. “It is important to remember that technology can be a great asset, but can just as easily be a liability,” the deputy said in a news release, urging users of such devices to regularly monitor such gear. SAR will respond to all SPOT activations, treating them as an emergency, unless contact can be made with whoever is carrying the device, to confirm otherwise, Whitcomb said. Read More,
--Robert Speik, July 22, 2012