According to the Cellular Telecommunications Industry Association, approximately a half million 911 calls are placed over U.S. cellular networks each month. With the cellular subscribers growing at an annual rate of 48 percent, the number of cellular 911 calls is increasing, creating a serious problem for public-safety response organizations.
In most metropolitan areas around the country, Enhanced 911 (E911) systems are in place that automatically provide the Public Safety Answering Point (PSAP) dispatcher with the phone number and location of 911 callers using wireline phones. Billions of dollars have been invested nationwide in E911 systems. These systems make it possible for emergency calls to be immediately routed to the appropriate PSAP and for assistance to be dispatched to the proper location whether or not the caller is able to communicate his location. Automatic Location Information (ALI) also speeds up the interrogation and dispatching process.
Cellular networks today can not support E911, as there is no way to accurately locate the caller. By some estimates, up to 25 percent of cellular 911 callers are unable to identify their location. With the number of U.S. cellular, PCS and enhanced specialized mobile radio subscribers projected to grow to 55 million or 60 million by the year 2000, public-safety organizations are concerned the substantial investment in E911 systems will become obsolete and the level of emergency service will be degraded.
Looking for answers
In response to this growing problem, a number of public-safety organizations, telecommunications standards bodies and trade associations are seeking to find ways to support E911 service over wireless networks.
In late 1992, the National Emergency Number Association Inc. and the Association of Public-Safety Communications Officials International Inc. submitted comments to the Federal Communications Commission on the proposed rulemaking for personal communications services. These comments emphasized the need for PCS to provide Automatic Location Information.
NENA’s comments proposed the use of cell or cell segment identification in the near term for approximating the caller’s location and a more precise approach in the future.
As a result of NENA and APCO’s comments, the FCC, in its September 1993 Second Report and Order amending PCS rules, stated the following: “The industry and standards-setting bodies should direct particular attention to offering an emergency 911 capability that would work with enhanced 911 systems (E911) and, to the extent feasible, permit locating a caller in situations where the caller is unable to state his location. We are particularly concerned that unless an E911 capability is designed into PCS systems, dialing 911 from a PCS telephone will not be equivalent to dialing 911 from a traditional wired telephone.”
The FCC further stated, “Accordingly, we contemplate initiating a proceeding in the future to address E911 and related issues with regard to PCS, cellular, and any other relevant mobile services. While we are not in a position at this time formally to require E911 capability for PCS on the basis of the record before us, this is a matter of serious concern and we will closely monitor developments in standards-setting bodies and elsewhere regarding PCS and E911.”
In December 1993, a Petition of Reconsideration was submitted to the FCC by the Texas attorney general’s office on behalf of the Texas Advisory Commission on Emergency Communications and supported by 911 program authorities in several other states. Among the items in this petition was a request that the FCC amend its rules on PCS to require transmission of 911 caller location or, alternatively, initiate a proceeding to address the need for all wireless services to provide 911 calling party number and location.
In June 1994, the State of California Telecommunications Division and APCO commissioned C.J. Driscoll & Associates to conduct a study of location systems and technologies that could be used to locate wireless 911 callers.
The purpose of the study was to establish whether it is viable for the FCC to require that wireless networks provide 911 caller location. The study was also intended to contribute to the efforts of the standard-setting bodies in establishing realistic standards for wireless 911 emergency services.
The study, entitled “Survey of Location Technologies to Support Mobile 911” covers location systems and technologies developed by some 20 companies. These include network-based location systems, which consist of an overlay to an existing wireless network, and systems which are based on external radiolocation systems, such as the Global Positioning System (GPS). The study includes a description of each system along with the status of system development, accuracy estimates, performance in dense urban environments and indoors, and projected deployment cost, where available.
Systems developed by Associated Communications Corp., Engineering Research Associates (E-Systems) and Terrapin Corp. are among those covered in the study. An expanded version of the initial study is available from C.J. Driscoll & Associates, Rancho Palos Verdes, Calif.
Based, in part, on the above location system study, the TR45 Committee of the Telecommunications Industry Association, responsible for establishing U.S. cellular communications standards, concluded it is reasonable to establish a near-term goal of 400-foot accuracy for 911 cellular caller location and a long-term goal of 40-foot accuracy. Altitude information is desirable for indoor calls in order to identify the floor from which the call was placed.
The Personal Communications Industry Association and the National Association of State Nine-One-One Administrators (NASNA), along with NENA and APCO, have issued an Emergency Access Position Paper.
This paper recommends a migration path for 911 caller location, to begin with a requirement that the location of the base station to which the wireless handset was communicating be identified and progress toward the ability to locate an individual wireless handset in a three-dimensional environment, as location technology and the cost of implementing such a technology become attainable.
The paper suggests the standards organizations determine if a minimum geographic location accuracy of 400 feet can be achieved both technically and economically. A much higher level of location accuracy should be considered in urban environments where it will be necessary to determine the precise location of a caller within a multi-story structure.
A Joint Experts Meeting on Wireless Support of 911 and E911 Emergency Services will be held Oct. 11-14 in Reston, Va. Among the purposes of the meeting are to define PSAP requirements, identify current and developing technologies that can support PSAP service and identify the need for standards.
The FCC plans to issue a proceeding on wireless E911 in the September-October time frame. It is anticipated this will be a Notice of Proposed Rule Making covering cellular, PCS and other relevant mobile services.
The TR45 Joint Experts Meeting report and the PCIA/ NASNA/ NENA/APCO Emergency Access Position Paper have been submitted to the FCC to represent the positions of these organizations for consideration in the forthcoming proceeding. It is anticipated the proceeding will address the issue of wireless 911 caller location along with other wireless 911 issues.
System applications
Deploying location systems to support wireless 911 will not occur immediately as wireless network standards may be impacted and standards for incorporating caller location, number and other information into the PSAP will have to be developed by public-safety organizations such as NENA.
However, if these location systems are deployed over the next few years, they will be applied to a wide range of services, in addition to 911. These services include deterring fraudulent use of wireless phones, stolen vehicle recovery, roadside assistance, routing travelers to their destinations and fleet vehicle location.
The accuracy requirements of these services vary. Accuracy of 400 feet, for example, will not be adequate for real-time routing requirements in which the driver needs to be advised that he is approaching an intersection at which he must turn. However, location systems that can achieve accuracies of 100 feet or better would meet the requirements for most intelligent vehicle highway system (IVHS) related services and other applications which require identifying the location of mobile users.
Therefore, it is anticipated that deploying wireless location systems will not only enhance public-safety, but will generate revenue from a wide range of services, which will help defray the cost of these systems.
Clement Driscoll is principal of C.J. Driscoll & Associates of Rancho Palos Verdes, Calif., which provides consulting on automatic vehicle location (AVL) and mobile communications to corporate and government clients. He has written numerous articles for industry publications.
