-->[OO]:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: -->]OO[::[ Wireless E-9-1-1 ]::::::::[OO--[ by digiphreq ]------------------- -->]OO[:::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::: Wireless Enhanced 9-1-1 Service- Architecture and future. By Digiphreq Darkcyde Communications 5/8/99 darkcyde.8m.com "A nerd is somebody who's life is focused on computers and technology. A geek is somebody who's life is focused on computers and technology and likes it that way." Ye Ol'' Table of Contents I. Introduction II. A Bit of History III. FCC Regulations on Wireless 9-1-1 IV. Common Wireline 9-1-1 Service V. Issues on How to Make Wireless 9-1-1 Work 1. Stage 1 2. Stage 2 VI. Long Term & Conclusion I. Introduction: As you probably very well know Enhanced 9-1-1(E9-1-1) is the most common for of 9-1-1 these days. It is possible to find B9-1-1, if you live in the middle of no where... Anyway today wireline E9-1-1 relays all the important info on you. Location, name, and the telephone number to the dispatch telecommunicator which then accurately routes your call to the proper Emergency Dispatch Station. In theory this makes the whole process faster, as to get you help quicker. Which is often not the case. With the current day workings of wireless networks, E9-1-1 isn't really possible. They have begun to incorporate technologies to support it though. This is all because of a bunch of new regulations which the FCC placed on wireless communications, which called for an improvement of the use of E9-1-1. Originally in 1996 they created a two stage time line, which I will be explaining later. A quick overview is that Stage one will require wireless networks to provide the user's call back number and the location including which cell sector they are in. Stage two allows for a more precise pin point of the caller's location, which requires a bit more hardware and technology. I will touch on a brief history of Wireline E9-1-1 service, Wireless E9-1-1 service operations(how it should work), and a more detailed overview of the Two stage process involved in upgrading the current Wireless system. II. A bit of History: The first 9-1-1 service, was introduced in Alabama in 1968. It's also known as Basic 9-1-1 or B9-1-1. This was a very primitive version of E9-1-1 which only routed your call to a local police station. In the 1980's B9-1-1 was enhanced and there was the introduction of E9-1-1. Database Automatic _ Management Location / \ System Info | / \ | | _____ | | : : Emergency | : : Service | :_____: Adjunct | | | | | | | | | | | 5ESS switch | Central E9-1-1 | Office _________selective_____________PSAP router \ (routes Ani) \___ Displays: Location Call back # Mapping Location As you can see (sort of) when a residential or commerce line dials 911, there call goes to the central office switch which routes their call to a E9-1-1 selective router. Which then routes the call to the correct PSAP based on the user's telephone number. The phone number is passed from the PSAP to the Customer Premises Equipment (CPE), which it uses to look up an Automatic Location Information (ALI) database for the user's name and address. On top of all this the user's line number is then used as the call back number in case the caller accidentally hangs up(Ex. the killer hangs up the phone for them...) or the PSAP dispatcher needs to call the user back. III. FCC Regulations on Wireless 9-1-1 (This Was Borrowed) Points of Interest in the FCC Ruling Over Wireless 9-1-1 -Wireless carriers must support call routing based on cell sector, and they must also convey information sufficient to enable the PSAP to call back the 9-1-1 caller(that is transmit the calling party number) within 18 months of the ruling's effective date. This requirement is sometimes called Stage 1. -Carriers must support deployment of technology to determine a caller's location within 125m of accuracy for 67% of all wireless 9-1-1 calls within five years effective date. Support of a specific location determination, which will require PSAPs to be able to handle coordinates rather than street addresses, is sometimes called Stage 2. -The FCC will entertain waivers on a case by case basis for not complying with the rules. -Any call from a handset having a MIN must be transmitted to 9-1-1 even if the handset no longer has valid service. The call may not be intercepted or blocked. The local PSAP may decide whether or not to receive calls from non-MIN telephones, for example phones that were never service activated. if a PSAP requests these calls, the carrier is supposed to provide them. -The ruling applies to cellular, broadband PCS, and geographic area SMR providers (meaing SMRs that provide mass market services). Systems provided by movile satellite communications vendors, such as Motorola's Iridium, are not covered by this ruling.Because it is not a federal issue, the FCC has determined that localities and states should plan for cost recovery at their levels. Details of subsidization for deployment and nonsubscriber calls must be negotiated on local level (State or municipality, similar landline 9-1-1 subsidization). Funding should be available for both basic and enhanced 9-1-1. Conditions for Compliance: 1. PSAPs must request and be ready to handle wireless location information. 2. A cost recovery mechanism (negotiated at the local level) must be in place. PSAP Choices: Because of the two conditions for compliance PSAPs effectively choose implementation dates. PSAPs also get to choose whether they want to handle calls from handsets without MINs. Further Rulings for the Future: - Tightening of location accuracy requirements to 40 feet 90% of the time, - Availability of altitude information, - Performance criteria on time for calling completion, - Consumer Education programs for wireless 9-1-1, - Possible reconsideration of issues of PSAP choice, and - Possible requirement that the strongest signal must carry the 9-1-1 call. IV. Common Wireline 9-1-1 Service Today in most areas wireless communication networks have the ability to run off of B9-1-1. This is because of the AUTOPLEX 1000 System. Basically a caller can dial 9-1-1 and be connected to the proper ASAP based on the location of the serving cell. Location routing is accomplished with a digit by digit method. Which allows Automatic Number Identification (ANI) for Centralizing Automatic Message Accounting (CAMA) signaling to field a number corresponding to the serving cell. Upon arrival at the E9-1-1 selective router the field issued to show the PSAP for that area. The call is then routed. An alternative to this would be to populate the ANI field with a 7-digit dial-back number as opposed to the location information. The E9-1-1 selective router then assigns the incoming trunk one of four NPAs. The remaining seven NPAs complete the 10-digit dial-back number. V. Issues on How to Make Wireless 9-1-1 Work: There are several wireless problems which limit the use of E9-1-1. First CAMA trunk signaling transmits one 8-digit telephone number to the PSAP. This causes problems because it can only have 4 NPAs, and therefore cannot give caller identification while wireless subscribers are roaming. Second the caller's telephone number cannot be used to route a wireless E9-1-1 call since the caller's location depends on the Mobile Directory Number (MDN). Since a real street address cannot be associated with a MDN, the dispatcher cannot dispatch emergency services. So while this could seem kind of hopeless its really not. A lot of other ways have been devised to handle this all. Which commonly involve in band analog MultiFrequency (MF) signaling. I'll start out with some bad idea's then explain the good one. There was the Group D signaling solution. It was first intended for equal access upon long distance calls. It was able to support both a 10-digit ANI and a 10-digit dialed-digits field. Essentially the dialed-digits field could be used for the location information. The problem with this method(and you knew the would be a problem...) is that it cannot support an interface between a Mobile Switching Center (MSC) to the selective router as does Signaling System 7 (SS7). Next there was a method which used a conversion to CAMA from Group D signaling. This method is fairly complicated and really is degrading with performance, which makes it a bad choice... here goes an explanation. With the idea that MSC cannot provide SS7 connectivity with the PSTN and the 9-1-1 selective router cannot support SS7 or Group D signaling for 9-1-1 call processing. With a Group D to CAMA translation device between MSC and the selective router, it could provide signaling conversion. The translation device has a third field which sends the 10-digit dial-back number and location information to the ALI database during call set up. The device send s a special 7-digit key value in the ALI field to the selec tive router. Basically then this key would represent the cell from which the call was placed to the router. Then the 7-digit key field is routed to the PSAP during the setup. Meanwhile the ALI runs a check by the PSAP using this keys value or field, then it would return the real 10-digit MDN. Next we have a expanded CAMA signaling solution which has no practical reason for existing. It just won't work. I'll explain it anyway. The existing CAMA interswitch 9-1-1 signaling maybe built upon to support a 10-digit ANI and 10-digit location number. This requires some modifications to be made to the current PSAP hardware and the 9-1-1 selective router. This would cause a degradation of the performance due to extra MF signaling involved. Finally we have the practical solution which is what was used mainly for the Stage 1 process. Which is a solution through SS7, which should make hybrid's day. He just can't seem to get enough on SS7. The use of SS7 will be explained in my explanation of what Stage 1 was. Stage 1: Basically an entirely new architecture is needed. The common setup was to distribute the service processing across the AUTOPLEX System 1000 MSC, 5ESS-2000 Switch, Emergency Services Adjunct (ESA), ALI database, associated database management system, and the PSAP CPE. The MCS used ISDN- UP Signaling to convey a 10-digit dial-back number in the charge number parameter, as well as location information in the caller party number. The 9-1-1 selective router uses the location information to route the call to the appropriate PSAP. An ISDN PSAP is required to receive and use both the 10- digit dial-back number and the location information. Some major improvements to the AUTOPLEX System 1000 were put in to affect for Stage 1. The CAMA signaling is replaced with ISDN-UP which has the obvious advantages of being able to transmit both dial-back number and the location information as opposed to CAMA signaling 8-digit information. Also CAMA signaling only supported a 7-digit calling party number unique with one of four area codes, where as ISDN-UP will support the full 10-digit calling party number. Another major change was in MSC, which was to then use ISDN-UP signaling as well. Which could convey a 10-digit dial-back number in the charge field and a 10-digit routable Directory Number (DN) which represents the cell location and originating service provider in the called party number field. Basically this is used to reach roaming customers. The use of a DN allows a call to be routed through the PSTN to the E9-1-1 selective router grouped with the PSAP without direct connection trunks. The E9-1-1 selective router then selects the appropriate PSAP based on the serving cell, call type, and some other less important criteria. To support this, the dialed-digit routing capability must be integrated with the 5ESS-2000 switch E9-1-1 feature, thus allowing these calls to be routed using the called party number rather than the ANI. Location information, dial back number, and service provider are forwarded to the PSAP via ISDN during call setup. An ISDN PSAP is required to receive and use both the dial back number and location information encoded in the dialed digits. In the case where the PSAPs cannot support ISDN and enhanced adjunct processor interface (API) will provide the ability to support existing PSAP CPE, which uses CAMA in-band signaling. The information received via enhanced SS7 ISDN-UP from the MSC to the 5ESS-2000 will be forwarded over the API when the ESA queries made for routing information. The information will then be forwarded to the ALI over a new ESA to ALI interface. The 5ESS switch will then pass a unique 7-digit key value to the PSAP in the ANI field. When the ALI is queried by the PSAP with this value, the location, service provider and dial back number is returned to the PSAP. The PSAP equipment would need to be enhanced to provide the caller's location to the telecommunicator using a textual method whereby the called party number is used to query the ALI database, which provides location and identification of the cell/sector. Alternatively, Geographic Information Systems (GIS) can be used to provide a geographic representation of a caller's approximate location on a computer-generated map. The PSAP GIP map displays provide the dispatcher with visual identification of the caller's location (their cell/sector) in perspective of other important geological locations. The displays can pinpoint roads, addresses, buildings, houses, ems dispatch vehicles, fire hydrants, cell sites, and the service boundaries to emergency services. Ok so since this was originally put to use back in 96 and was to last as a period for approximately 18 months, it has for the most part gone in to affect in most areas. It's hard to say though, depending on the area.... Stage 2: Stage 2 is basically just an architectural build on what was created in Stage 1. The implementation was to last near 5 years. Stage 2 would bring new GIS capabilities along which would work better with the wireless E9-1-1 system. During this stage the geolocation system was required to meet the FCC's 5 year requirements for wireless E9-1-1. So the wireless system could communicate with the geolocation system to determine the position of a target mobile terminal (which has dialed 9-1-1). Alternatively, if the wireless system recognizes a mobile telephone equipped with GPS the mobile terminal could provide its current location via new air interface messages. Several technologies have been proposed to meet the FCC's long term mobile locating requirements for wireless E-9-1-1 systems. To meet the needs of the 9-1-1 community that is to those who provide the emergency response service to the public, the existing base of mobile phones must be supported without modification. Promising technologies proposed for this purpose include time difference of arrival and direction of arrival triangulation systems. Each has its advantages depending on the physical environment in which it is targeted to be deployed. In addition, advances in GPS receiver technology have made it possible to integrate GPS with wireless telephones. Which has been recently brought somewhat into the commercial market. If the mobile terminal knows its location, it makes sense to use this information for the E9-1-1 system because the GPS is potentially much more accurate than a location determined by means of time difference of arrival and direction of arrival triangulation. The geolocation information (latitude, longitude, altitude, and accuracy) will be integrated in an SS7/ISDN-UP and ISDN call set-up message for the 9-1-1 call. At this point in the evolution, SS7/ISDN- UP and the Transaction Capabilities Application Part (TCAP) signaling protocols will be modified to support transmission of the location information from the wireless system to the selective router. ISDN-UP will be used for delivery of location information with call set-up while TCAP messages will be used to support caller location tracking, which requires location updates during a call. Regardless of the location technology used by a wireless service provider, the location information will be passed through the network and used in a standard way. Therefore, the E9-1-1 communications network infrastructure will remain implemented in the wireless network. Although not required by FCC rule making, the new location information can be used to route a call to a PSAP accurately. Upgrades to support this capability include geolocation routing capabilities that will be integrated into the 5ESS-2000 switch's E9-1-1 feature, the ESA, and the DBMS. Once again, the information is delivered to the PSAP, and computer aided dispatch systems with GIS mapping will used to portray the information in a way that makes it easily understandable by the telecommunicator and responding emergency personnel. In turn, the improved location information will be reflected in the GIS map display with a pinpointed location and associated accuracy representation. A GIS based service administration capability will proceed the ability to define and dynamically change municipal jurisdictional boundaries and emergency service zones via a computerized map interface. This administration system will indirectly maintain the call routing data used by the 9-1-1 selective router. The process will simplify the administration of the 9-1-1 service by eliminating the need to share cell/sector location data among wireless, local exchange, and emergency service providers. In this environment, base station reconfigurations by a wireless service provider will no longer affect the data maintained in the PSTN and PSAP providing the end-to-end E9-1-1 service. Onward to my brief explanation of triangulation and geolocations. Network based triangulation methods of location (TDOA and DOA) require that at least two DOA or three TDOA receivers locate the target mobile terminal and that some technique be available to resolve ambiguities caused by multipath propagation. These requirements may be difficult to meet in many wireless environments causing the accuracy of the locating system to be degraded or making system deployment cost prohibitive. For example, in rural environments, cell sites cover very large geographical areas, often resulting in marginal voice coverage on the fringes of the cells. In such areas, it is unlikely that receivers in multiple cell sites would "see" the mobile terminal, thereby, making it difficult or impossible to establish the caller's location. This problem could be worked around by adding supplementary location receivers, although such deployment might be very costly for rural wireless service providers. Furthermore, in dense urban areas, the effect of multipath propagation becomes a dominant factor in deterioration of the accuracy of the locating system. Multipath propagation refers to multiple copies of the same transmitted signal are received by an antenna. Usually, the first signal arrives via the most direct path from the transmitter. Additional copies of the signal are received at later times, ranging from hundreds of nanoseconds to tens of microseconds later, and they then overlap the first signal. These copies result from the reflection of the original signal from various objects, such as buildings and vehicles. The effects of multipath propagation particularly in cities can degrade the precision of the location estimate to such a point that no added benefit can be gained over visually reporting the serving cell/sector location because urban environments often have relatively dense micro cell grids for their wireless networks. These problems are difficult to overcome without some assistance from the mobile telephone. Whether or not the FCC requirement of 125m accuracy will be technically or economically feasible in such environments is not clear. VI. Long Term & Conclusion Although recent FCC ruling only requires location accuracy of 125m in 67% of all cases, the public safety community often requires even more accurate information. Ideally an emergency unit responding to a 9-1-1 call would know exactly in which room in a skyscraper which the incident is occurring or has occurred(using for instance the ISDN-UP altitude parameter). Clearly this level of accuracy cannot be achieved cost effectively with unmodified wireless phones and today's technology. With new technology and assistance from the mobile terminal, however future land based location systems will be able to provide much better accuracy than that of the FCC Stage 2 requirements. Although such systems are not available today, several concepts have been proposed for example signpost location beacons and specialized signaling schemes optimized for location purposes. Whatever scheme becomes dominant as the technology matures, the pursuit of standard implementations is important. This will insure that the cost as sociated with an improved wireless E9-1-1 system are reduced. Basically really from a safety stand point all this is really fine in my opinion. It will help save other people and possibly yourself one day. Meanwhile this isn't really a cell user's friend. This gives the wireless service providers more control over you with this type of technology, which can be looked at as a very bad thing. Anyway, peace.