In 1996, the FCC issued a Report and Order requiring all wireless carriers
and cell phone manufacturers to provide the capability for automatically identifying to
emergency dispatchers the location from which a wireless call is being made. At that time,
implementation of the E911 requirements was divided into two phases. Phase I required
wireless carriers to deliver to the emergency dispatcher
the telephone number of a wireless handset originating a 911 call, as well as the location of
the cell site or base station receiving the 911 call, which provides a rough indication of
the caller's location. This phase was implemented by the end of 1998.
Phase II requires carriers to deliver more specific latitude and
longitude location information, known as Automatic Location Identification (ALI), to the
dispatcher. There were a number of interim milestones for full implementation of this phase,
beginning in March 2001 and ending with complete implementation by the end of 2005. These requirements were not
fully met, and the FCC has fined a number of national operators in recent years for failure to meet their E-911 obligations.
Rapidly evolving and mixed technologies, geographical terrain differences, infrastructure issues, and the increase in the
number of people using mobile phones to meet more of their communication needs all added to the difficulty in implementing this requirement.
In September 2007, the FCC issued a new E-911 location decision and ordered operators to meet
interim and annual benchmarks during the next five years to ensure full compliance with these new requirements by September 11, 2012.
These regulations, which require location of emergency callers within 50-300 yards depending on the technology used, are not entirely
workable given the difficulties in geography and systems. Several companies banded together and obtained a stay on implementation
of this decision in the courts pending the outcome of litigation. At the end of August 2008, the FCC has agreed to voluntarily
withdraw the new regulations, citing the Public Safety community's agreement that more lax regulations will meet their needs.
Federal telecom policymakers want to examine whether there should be one, technology-neutral standard for wireless E-911 accuracy,
which could give substantial commercial advantages to some of the companies that have been working on technology that could meet
such a standard.
Providing the E911 service in a manner that is economically feasible for the carriers has proven
to be quite a challenge! The headaches aren't over yet -- for example, many of the location technologies
use GPS. This causes lots of concern over the use of UWB (ultra wideband), and possible concerns with
interference between UWB devices and GPS. You can read about this
issue in depth, and find out more about GPS in our UWB and GPS pages listed under
Related Information on SSS Online below.
Take some time to explore the articles, resources, references
and links below to learn more about this rapidly evolving subject!
Articles from SSS Online's Technical Briefings Archive
ADOBE Acrobat (.pdf) Files Relating to E911:
e911.pdf
Various Authors, Paper -- "Providing Universal Location Services Using a Wireless
E911 Location Network" -- (~135K) -- (Thanks IEEE!).
radioloc.pdf
Caffery and Stuber's April 1998 Paper (Georga Institute of Technology) -- "Overview of
Radiolocation in CDMA Cellular Systems" -- (~88K) -- (Thanks IEEE!).
1cellular.pdf
Prof. Randy H. Katz' (UCB) Briefing -- "CS294-7: Cellular Telephony" -- (~489K).
1dsss_intro.pdf
Phil Flikkema's (USF) Briefing -- "Introduction to Spread Spectrum" -- (~110K).
FCC's E911 Home Page. This page has press
releases, text of the FCC documents, implementation reports from wireless carriers, presentations,
and more.
Wireless 911 Information.
An excellent, up-to-the minute presentation of the current status of implementation of E911, putting
it all in perspective and providing lots of interesting links. This one is a must see!
MicroDATA GIS -
a company that specializes in E911 wireless software
Locate Networks -- this company integrates
ReFLEX wireless networks with advanced GPS to enable the signal to reach small, portable devices,
even indoors and in urban canyons, where ordinary GPS does not operate. A location request is
initiated through a Web site and forwarded onto the wireless network. The device captures and
calculates GPS data and sends it to Locate Networks servers via the wireless network. Their
Wide Area Reference Network (WARN) data enhances the accuracy of the GPS information.
The data is then calculated, translated into a street address range, and mapped.
TruePosition, Inc. -- their products use
TDOA location identification technology. They
advertise that their U-TDOA technology works with all existing and future wireless phones
without modification and accurately locates calls made in all environments, including dense
urban and indoor areas.
U.S. Wireless -- Their propietary location
pattern-matching technology known as RadioCamera did not require line-of-sight triangulation
involving multiple cell sites. The system was one of the first to pass FCC E911 testing in April 2001,
but the company went bankrupt in August of that year and all its assets, including the RadioCamera technology,
were purchased in December 2001 by TrafficMaster.
The TrafficMaster website lists products for vehicle navigation, traffic congestion information,
and vehicle tracking. There is no mention of RadioCamera.
Teletrac, Inc. -- Another vendor using proprietary TDOA
for location-identification, primarily for vehicle tracking systems. The advertise that their products
are also compatible with GPS and CDPD systems. Their principal product is called Fleet Director, and is aimed at
commercial fleet management. This company went bankrupt in 2001 and is now a wholly owned subsidiary
of TrafficMaster.
Cell-Loc, Inc. --
Another vendor using TDOA for location - see their
explanation of this technology written for the layman.
LoJack Corp. -- The stolen car locator company is
looking at using their AOA system for E911 applications.
