June 4, 2007 4:00 AM PDT

Homing in on a plan for cellular 911

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The FCC supports a proposal from the Association of Public Safety Communications Officials International (APCO) that specifies accuracy should be tested at the public safety answering point, or PSAP, level instead of on a statewide or regional basis. In a recent report, APCO reported that if accuracy were measured from the PSAP level, about 71 percent of tests made in seven sample regions would have failed to meet the FCC's standard for accuracy.

The cell phone industry opposes these new requirements. In a letter filed with the FCC, Verizon Wireless, T-Mobile USA, Dobson Communications and the Rural Cellular Association (RCA) said that changing the requirement would be "unwise" and "unlawful." They also fear that establishing stricter requirements would be too expensive, especially for carriers operating in rural areas.

"Rural carriers are doing everything they can to improve accuracy of E911," said Clay Dover, executive director for the RCA. "But in some of these areas you only have one cell tower, and you can't mandate companies build out a network for E911 compliance if it's cost-prohibitive."

Indeed, location accuracy can be especially problematic for carriers using GSM (Global System for Mobile Communications) technology. These carriers, which include AT&T and T-mobile, use a network-based technology that uses signals from multiple cell phone towers to determine a caller's location. But in some sparsely populated regions where there is only one cell phone tower, it's impossible to triangulate signals to get an accurate location. And putting up additional towers is too expensive.

"Carriers have limitations in terms of the technology that is available to them...but I think it's clear that in some areas of the country people are not getting the services they expect."
--Wanda McCarley, president, APCO

Carriers that use CDMA (Code Division Multiple Access) technology have their own challenges. These carriers, which include Verizon Wireless and Sprint Nextel, have embedded GPS receiver chips in handsets to track devices by satellite. This solution works well in a rural or suburban area where there is a direct line of sight between the satellite and the device, but it isn't as effective in cities where tall buildings can block satellite signals.

Both the network-based technology and the handset solutions can have trouble locating people inside large buildings, because some signals can't penetrate walls.

Due to these technology limitations, the FCC has applied two different sets of standards for accuracy compliance. Carriers using GPS-enabled handsets must be able to locate callers within 150 meters 95 percent of the time and within 50 meters about 67 percent of the time. Mobile operators using a network-based solution only need to locate individuals within 300 meters 95 percent of the time and within 150 meters 67 percent of time.

In an effort to address these issues, the FCC also has proposed looking at new technologies to improve accuracy. For example, it is currently seeking public comments on whether it should mandate the use of hybrid solutions that would combine network-based triangulation technology with handset-based satellite technology.

Verizon Wireless said it is already using a hybrid solution to help improve E911 accuracy as well as to provide location and navigation services to its subscribers. The way it works is that the system first uses a GPS receiver to get the location of the handset. If the signal isn't strong enough, the system then uses data from cell sites combined with satellite information to get a location. And if that doesn't work, it can use cell site data, which is similar to triangulation used on GSM networks, said Debra Lewis, a spokeswoman for Verizon.

Regardless of which rules, if any, the commission eventually adopts, Wanda McCarley, president of APCO, said it is important that the cell phone industry and public safety groups move forward to improve location accuracy, because it's what the public expects.

"Carriers have limitations in terms of the technology that is available to them," she said. "We understand that. But I think it's clear that in some areas of the country people are not getting the services they expect. We need to deal with that and fix it."

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9 comments

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gps
dont cell phone already have GPS on them. used for chosing what cell tower or towers the cell phone uses.
Posted by mongoose13223 (2 comments )
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Re: gps
Some cell phones have GPS receivers, but these are used for positioning (especially for E911 use). Not all handsets have GPS, and GPS is not used for choosing a cell tower.

Tower choice is determined by signal strength (the handset uses the tower from which it receives the strongest signal). This is not 100% accurate, since the handset should give preference to towers belonging to its carrier for business reasons. However, given two towers of equal cost, the handset will most certainly connect to the tower with the best signal.

There are many factors that affect the signal strength between a handset and a tower. Distance is a significant factor, but shadowing (large objects like buildings or mountains between handset and tower) and multi-path fading (multiple copies of same signal interfering due to reflection) can have significant impact on signal strength. Considering the effect of these other factors, position is too unreliable a metric for choosing a tower.

Capacity can also determine the choice of tower. If the tower with the best signal cannot handle any more connections, the mobile will have to choose another, if possible
Posted by silenthorn (5 comments )
Link Flag
GPS and location tech
In a quick word, No. Not all cell phones have GPS and it is not used for deciding which tower to use. The actual strength of the cell phone signal is what determines the tower.

There are two location solutions. GPS and network. The GPS requires being able to get a signal from several satellites. Network needs at least three antennas for triangulation. The FCC is on the right path to require the use of both.

The author of the article was only partly right about the cost. It will be a lot. But, the cost to the cell providers may not be as great as most folks think. In many places the providers are given "cost recovery" from the local state governments; which means the actual cost for the deployment of whichever technology is used is paid by the cell phone users from the tax on their phone.

Many state legislatures, in an effort to be seen as lowering taxes, are cutting the cell phone taxes. Another reason they don't tax the same as a wired phone is their view that a cell phone is a add-on luxury to a wired phone at home or the office; which is already paing the 9-1-1 tax. They have no clue there is a large percentage of folks who have only cell.

The cost recovery issue is going to be the thing that will virtually stop the program in many states. The states simply won't be able to afford it everywhere.

In my county there are about 200,000 people. 85% live in 25% of the county. It is an area replete with street signs and reasonable means of identifying the location. But, the area where the technology is most important the 75% that is rural and sparsely populated; and every hill looks alike.

The focus in the nation has been on the more populous areas.

If the FCC is going to mandate, they should also establish a funding method to accomplish. And make it something the state lawmakers can't tinker with.
Posted by GEBERWEIN (75 comments )
Link Flag
more orwellian overtones
So the wireless industry would like to give authorities a better location of our daily activates, conveniently through the smokescreen of ?better emergency response?

How long do you think it would take for a smart upstart to mine all that location data for some privatized use?
Posted by krunkandjunk (1 comment )
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E911 fees
What happen to the E911 fees we been paying that the cell phone company says it's "mandated" that they collect the fees?? Where have all those money went? In the pocket of all the big boss??
Posted by busterbunnytech (1 comment )
Reply Link Flag
Yeah, we have the technology
but can we afford it?

Thinking of the bozo that stepped down from aT&T with a $33 Million golden handshake, I wonder if he was really worth it?

As one who bailed out of Ma Bell years ago after 10 years seniority, I rather doubt it.

But haha, reading another Cnet story on how Chinese managers and CEOs earn significantly less, American companies could find not only tech jobs being outsourced, but their own.
Posted by NoVista (274 comments )
Link Flag
Costs incredible
In March a very small two position Enhanced 9-1-1 center, located over 100 miles from the switching server, cost total of $163,000 for equipment, installation and dedicated network.

The entire state network administration office (including the big boss' salary) is less than 2% of the amount of the tax collected.

The money goes into the network operation, equipment maintenance and upgrade to keep the system current with technology. Entire new networks had to be built to accommodate the wireless and VoIP technology demands that are erupting with volcano like force.

By the way, on my phone I can turn off the GPS for all but 9-1-1. So much for Orwell.

If this is taken out of the tax relm and not funded by the feds we can kiss any location or network goodbye. THe local politicos won't fund a dime. If they won't buy new phones for the local cop shop, what makes anyone think they will fund a calling network.
Posted by GEBERWEIN (75 comments )
Link Flag
Location not as pervasive as you might think
The CDMA networks (Verizon & Sprint primarily) already use GPS
in their handsets. AT&T primarily uses a network technology,
but accuracy is not good. Both solutions have been in place for
about 10 years, since the original FCC mandate.

Problem is, it doesn't work in certain places like densely
populated areas, inside buildings and other places where people
regularly make 911 calls.

A good blog about this <a class="jive-link-external" href="http://www.e911blog.com" target="_newWindow">http://www.e911blog.com</a>
Posted by karneson99 (1 comment )
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