The Texas Trial – From BarbedWire to No Wire
by John R. Melcher
December was a mighty fine month to be a Texan.The sky was blue, birds were singing, the climate wasunseasonably warm, history was made, and the dawn of a new era inpublic safety filled the morning sky. Now, before you succumb tothe nausea you are beginning to feel, take a minute to putyourself in the little pickup truck in that South Dakotablizzard, wondering why men have walked on the moon but you’vejust spent the last thirty-eight hours shivering and praying. Whydid this poor woman endure such a harrowing experience? They saythat timing is everything, and so it strikes me as ironic thatthis highly publicized tragedy-turned-happy-ending comes duringthe weeks between the Texas and New Jersey 9-1-1 wirelessintegration demonstrations. Thanks to the efforts of a localwireless carrier and a couple of F-16 fighter jets, this poorwoman will live to be a keynote speaker at some NENA conference.
I’m proud to relay some of our experiences inapplying a fix to this very type of problem. A team of experts inthe fields of public safety, telecommunications and governmentfinally pulled off what so many said would take years toaccomplish. Even to the amazement of some of the team members,the integration of two wireless carriers, location technology, adigital network and high tech PSAP equipment proved to beachievable. We knew that the two-phase FCC mandate 94-102 was notonly achievable, but that its goals could easily be surpassed.Our objectives were pretty straightforward. We set out to conquersome fire-breathing dragons and through sheer tenacity, ended upaccomplishing our goals:
?Selectively route wireless 9-1-1 calls to the appropriatePSAP
?Deliver the ten-digit telephone number ofthe calling party (even roamers)
?Locate the caller within 125 meters RMSlevel of accuracy
?Display the caller’s location on a standardPC-based mapping application
?Graphically depict the estimated accuracyof the location given
?Demonstrate the ability to transfer thecall to a neighboring PSAP and
?Demonstrate compatibility with embeddedbase networks and PSAPS
I am honored to have worked with such a pool of talent as thisproject brought together. My project co-chair is Beth Ozanich,formerly of Tarrant County 9-1-1 District and now of SCC employ,and our facilitator of bureaucracy, Carey Spence of the Texas9-1-1 Commission. It all started two years ago when GreaterHarris County 9-1-1 decided to prove that integrating wirelessand 9-1-1 wasn’t going to take rocket science. But I knew weshould not try this alone. I learned that Beth Ozanich possessedmore knowledge about mapping and geospatial data (I love thatterm!) than anyone in the public safety arena, and that my skillsand discipline in documenting were no match for hers.
We sought the blessing of our bosses (surely youknow our bosses, NENA officers Bill Munn and Laverne Hogan) whothen allowed us to approach the Texas Advisory Commission onState Emergency Communications for some funding assistance. TheCommission’s own Carey Spence saw quickly that if we could trulypull this thing off, the impact would be statewide, or bigger.She believed in us when so many did not. Mary Boyd fought a fewbattles for us before she left the Commission, as well. WhyHarris County 9-1-1, Tarrant County 9-1-1, and the State 9-1-1Commission would spend so much time, money and effort on this”star wars stuff” and not buy more call loggingrecorders was beyond the comprehension of some of our detractors.Those same detractors later came and asked us for copies of theproject documentation. God Bless the naysayers! They sometimesprovide valuable motivation.
We split the project into two segments in anattempt to follow the FCC report and order. Phase One requiredthat caller ANI be delivered. Our team included some pretty heavyplayers. We had the participation of GTE Mobilenet, NORTEL,Southwestern Bell, Combix Corp and several others. I’ll try notto wax technical or philosophical, but the scheme went somethinglike this:
GTE Mobilenet assigned pseudo-ANI to all cellsectors in our test area. This is a common practice for mostagencies today. Call delivery was via a dedicated T-1 provided bySouthwestern Bell and our “goddess of customer service”and full time account manager, Cindy Clugy. The calls were sentto our own NORTEL Meridian One PBX switch, which is of the Option61C flavor. When using the Feature Group D signaling scheme youget two telephone numbers along with the voice call. Callingparty number (CPN) and called party number are delivered at noextra charge. For 9-1-1 purposes, we translated the called partynumber of 9-1-1 to a usable telephone number known as pseudo-ANI.Pseudo-ANI is nothing more than a concocted telephone number usedto uniquely identify a cell site or sector.
The Meridian One served as our selective routing tandem bypassing the pseudo-ANI and the caller’s ANI. The M1 would passthe pseudo-ANI to a data base for routing instructions, thenwould deliver the call to the appropriate PSAP based on thatlookup. It should be noted that both PSAPs in the phase oneportion of the project were hanging off the Option 61. Thecaller’s phone number was displayed to the call taker on thetelephone set as well as NORTEL’s VISIT ENR® workstation.Additionally, a map of the radio frequency coverage area of thedelivering cell sector was displayed so that the call taker coulddetermine the neighborhood from whence came the call. Thechampagne cork on this demonstration popped in May of 1996.
Phase Two, which included delivery of specificwireless location via location determination technology (LDT – anew acronym for us 9-1-1ers) got really exciting as we moved intothe public switched network. Houston Cellular was our partner forthis portion of the trial, connecting their cellular switch tothe Southwestern Bell selective routing tandem (a Lucent 5ESS).This was a digital connection utilizing SS7 to deliver the callwith both telephone numbers. A fast network, indeed, as weexperienced call delivery times under two seconds.
The Southwestern Bell tandem was connected to anSCC Communications product known as SR/ALI. This is a data baseapplication with call routing capabilities that substituted forthe selective routing process normally associated with a 5Etandem. The SR/ALI box performed a “point-in-polygon”routine that delivered a normal ESN to the tandem. The switchused in this phase was actually the in-service central officethat feeds dial tone to the world renowned Texas Medical Center.The 9-1-1 generic software was loaded and the switch just satthere, fat and happy, doing what a 9-1-1 tandem normally does …take appropriate phone number in, look up phone number in ESNdata base, route call to appropriate PSAP. We didn’t bother totell it that it was talking to a third party data base, and itdidn’t ask or seem to care.
Lou Stilp gift wrapped TruePosition, a company ofThe Associated Group, and provided our LDT. Timed difference ofarrival, or TDOA, was used to determine the caller’s location.This is the old mathematical routine we used to hate in algebraclass. You remember how it works…
A train leaves New York at noon on Thursday,bound for L.A. at a speed of 50 miles per hour. Another trainleaves L.A. bound for New York at a speed of 62 miles per hour.At what time do the trains meet and what color is the caboose?
The same logic applies when measuring radio signals, with a fewother bells and whistles to make it work. The output of thissystem is delivered as a data packet containing the mobiletelephone number, its latitude and longitude, a time stamp and aconfidence level (degree of accuracy).
Since we all know that a tandem looks for an ESNand 9-1-1 call takers look for a street address, we applied theinterpretation skill of SCC’s SR/ALI box. It speaks 9-1-1. TheSR/ALI application takes the latitude/longitude information andplots boundaries, as well, so when the lat/long is plotted, anESN is obtained and fed to a data record that is created “onthe fly.” When the tandem comes calling with a telephonenumber, the SR/ALI shoves an ESN onto the front porch, and amarriage is born.
NORTEL’s Derek Prada provided facilitation,software mods, and our project manager, Chris Ouellette. Thecalls were delivered to one of our three test PSAPs. The PSAP CPEused was again VISIT ENR®. The first PSAP was connecteddigitally to the tandem via Primary Rate Interface (PRI). Theother two were via the conventional CAMA PSAP trunks. PSAP onecould get all ten digits of the caller’s telephone number, evenif they were a roamer! The other two only received the normaleight digit but could retrieve the correct data via the ALIlookup. The VISIT ENR® application can tell the difference andquery the normal ALI data base for wireline calls, or query theSR/ALI data base for the wireless calls. Wireless ALI data camein the conventional format but also contained lat/long and otherinformation. The ENR workstations were integrated with MapInfomapping software. VISIT ENR® was able to call up the appropriatemap and display the caller’s location. Additionally, a circle ofconfidence was automatically drawn around it to depict the levelof confidence, or accuracy of each test call generated. A pictureis truly worth a thousand words and thanks to Rick Maw of CombixCorp., the plotting and display routine occurred in just a coupleof seconds. It should be noted that if one has an accurate streetcenterline file available, lat/long generated by the LDT can betranslated into a street style address, alleviating the need fordesktop mapping installation. ALI could be delivered in thestandard textual form.
GTE Telops provided the services of GTE Labs tolend objective and academic validation of our project and conductstatistical analysis. Remember, no project is really valid untilsome smart person says so.
The project demonstrated that technology is not abarrier for real solutions to the wireless 9-1-1 issue. Wedemonstrated over a two-week period to professionals from theareas of public safety and government, and both wireline andwireless telecommunications. Team work, in the true sense of theword, is the real answer. Don’t tell us it can’t be done, we justdid it! Although there are other ways to slay this dragon, webelieve that good old fashioned American ingenuity will alwaysprevail. Leave your embedded mindset and your politics at thedoor and get busy. It’s time ask for the order. Call yourwireless carrier and do lunch. It will be the best Big Macinvestment you’ll make for a long time.
And, by the way, extensive documentation willsoon be available for distribution on the technical aspects ofthe Texas WIP project, including some discussion of othersuccessful trials accomplished by Clark County, Washington, andthe New Jersey State Police. If you desire a copy of thisdocumentation, call our project manager, Chris Ouellette at905-863-2195. Don’t call Chris until April, though; that’s whenthe document will be ready. And by all means, don’t call mebecause I’ll be at Charter Hospital in their Wireless RecoveryProgram. Now put this down and get to work!
John R. Melcher is Director of Information Systems in theGreater Harris County 9-1-1 Emergency Network. The Network is thelargest 9-1-1 system in Texas and the third largest in the UnitedStates, serving two counties, 47 PSAPs, 900 telecommunicators,and approximately 156 responding agencies including police, fireand EMS for 3 million citizens.