System and Method of Routing Emergency Services Calls in a Radio Telecommunications Network

1. Technical Field of the Invention

This invention relates to radio telecommunication systems and, more particularly, to a system and method of routing emergency service (e.g., 9-1-1) calls from a mobile station to a Public Safety Answering Point (PSAP).

2. Description of Related Art

In existing radio telecommunications networks, there are several methods of routing emergency services calls (for example, 9-1-1 calls) initiated by a mobile subscriber to the appropriate PSAP. The appropriate PSAP may be determined, for example, based on time-of-day and/or geographic considerations. For example, an emergency call from a mobile station traveling on a highway may be routed to different PSAPs, depending on the location of the MS. In addition, some PSAPs may be operational only during certain hours.

FIG. 1 is a message flow diagram illustrating a first existing method of routing emergency calls in deployed cellular networks. When a mobile station 11 originates an emergency call at 12, the serving mobile switching center (MSC) 13 performs an analysis at 14 of the called number and determines that the call is an emergency services call. The serving MSC then determines an approximate location of the mobile station based, for example, on the location of the serving cell or sector. An appropriate PSAP 15 is then selected, based on either location or time-of-day, and a trunk is established to the selected PSAP at 16. However, other factors which could influence the choice of PSAP are not considered, and the PSAP has no advanced warning that the call is coming.

FIG. 2 is a message flow diagram illustrating a second existing method of routing emergency calls in deployed cellular networks. TIA/EIA/PN3581 (J-STD-034), which is hereby incorporated by reference herein, utilizes a selective router node 21 in the cellular network. The selective router 21 may be located outside the serving MSC and is typically located outside of any associated home location register (HLR). When the mobile station 11 originates an emergency call at 22, the serving MSC 13 performs an analysis of the called number at 23, and determines that the call is an emergency services call. The serving MSC then determines an approximate location of the mobile station. A call setup signaling message 24 is then utilized to provide the selective router 21 with routing digits which identify the cell or sector where the calling mobile station 11 is located. In Phase I of J-STD-034 implementation, the granularity of the location information is defined down to the cell or sector level. In Phase 2 of J-STD-034 implementation, the granularity of the location information will be defined down to 125 meters, 65 percent of the time, in both the X and Y directions.

The selective router 21 then identifies the PSAP 15 which corresponds to the identified cell or sector at 25, and a trunk is established to the selected PSAP at 26. However, factors other than location which could influence the choice of PSAP are not considered, and the PSAP has no advanced warning that the call is coming.

In order to overcome the disadvantage of existing solutions, it would be advantageous to have a system and method of routing an emergency services call which provides an intelligent choice of PSAPs, warns the PSAP that an emergency call is coming, and provides the PSAP with advanced information regarding the context of the call.

Although there are no known prior art teachings of a solution to the aforementioned deficiency and shortcoming such as that disclosed herein, U.S. Pat. No. 5,239,570 to Koster et al. (Koster) and U.S. Pat. No. 5,598,460 to Tendler (Tendler) discuss subject matter that bears some relation to matters discussed herein. Koster discloses a 9-1-1 switched access system in which shared lines are made as reliable as dedicated lines. Thus, Koster does not teach or suggest a method of routing an emergency services call which provides an intelligent choice of PSAPs, warns the PSAP that an emergency call is coming, and provides the PSAP with advanced information regarding the context of the call.

Tendler discloses a system for enhancing the reliability of rescue services by providing a 9-1-1 back-up system in which the termination of an emergency call is sensed, followed by dialing the telephone number of a predetermined dispatch office. The dispatch office then calls back the nearest PSAP to ascertain whether or not rescue personnel are on their way. Thus, Tendler does not teach or suggest a method of routing an emergency services call which provides an intelligent choice of PSAPs, warns the PSAP that an emergency call is coming, and provides the PSAP with advanced information regarding the context of the call.

Review of each of the foregoing references reveals no disclosure or suggestion of a system or method such as that described and claimed herein.

In one aspect, the present invention is a method of routing an emergency services call from a mobile station to a selected Public Safety Answering Point (PSAP) in a radio telecommunications network. The method includes intelligently selecting the PSAP from a plurality of PSAPs, warning the selected PSAP that the emergency services call is coming prior to routing the call to the selected PSAP, and providing the selected PSAP with advanced information regarding the context of the call.

In another aspect, the present invention is a system for routing an emergency services call from a mobile station to a selected Public Safety Answering Point (PSAP) in a radio telecommunications network. The system comprises means for intelligently selecting the PSAP from a plurality of PSAPs, means for warning the selected PSAP that the emergency services call is coming prior to routing the call to the selected PSAP, and means for providing the selected PSAP with advanced information regarding the context of the call. The means for intelligently selecting the PSAP from a plurality of PSAPs may include a PSAP selector which selects the PSAP based on such information as, for example, the location of the mobile station, the Local Access and Traffic Area (LATA) in which the mobile station is located, the time-of-day, and the day-of-week.

The invention will be better understood and its numerous objects and advantages will become more apparent to those skilled in the art by reference to the following drawing, in conjunction with the accompanying specification, in which:

FIG. 1 (Prior Art) is a message flow diagram illustrating a first existing method of routing emergency calls in deployed cellular networks;

FIG. 2 (Prior Art) is a message flow diagram illustrating a second existing method of routing emergency calls in deployed cellular networks;

FIG. 3 is a message flow diagram illustrating the routing of emergency calls in a cellular network in accordance with the teachings of the present invention; and

FIG. 4 is a simplified block diagram of the system of the present invention.

FIG. 3 is a message flow diagram illustrating the routing of emergency calls in a cellular network in accordance with the teachings of the present invention. A mobile station 41 originates an emergency call at 42. The mobile station may include an indication in the message sent over the air interface that the call is an emergency services call. A serving MSC 43 then determines that the call is an emergency services call at 44 in one of several ways. The serving MSC may perform an analysis of the called number, the MSC may receive an indication via the air interface from the mobile station, or by other means. The serving MSC then sends a message 45 such as, for example, a location request (LOCREQ) Invoke message, an origination request (ORREQ) Invoke message, or another message dedicated for this purpose to an SCP 46. The serving MSC adds parameters identifying refined cell or sector information or the latitude and longitude coordinates of the calling mobile station 41, as well as the analog voice channel or digital traffic channel by which the mobile station is served. The SCP 46 recognizes the call as an emergency services call because (1) SCPs do not normally receive LOCREQ messages, (2) the presence of the mobile station parameters and cell location parameters in the message 45, (3) the usage of the dedicated message, or (4) by recognizing the digits 9-1-1 in the DialedDigits parameter of the LOCREQ or ORREQ messages.

If the SCP 46 has received refined cell or sector information from the serving MSC, the SCP then utilizes this information and internal service logic at 47 to determine the mobile station location. Otherwise, the SCP utilizes the received mobile station location information and internal mapping functions to determine the appropriate PSAP 48. The choice of PSAP may be based on a number of factors including, for example, the mobile station location, the mobile station telephone number, the health status of the mobile station's subscriber, the Local Access and Traffic Area (LATA) in which the mobile station is located, the time-of-day, and day-of-week. Additional factors may also be considered. Information such as the health status of the mobile station's subscriber may optionally be obtained by the SCP at 49 by querying a subscriber database in which critical health conditions such as epilepsy or heart conditions may be recorded. The SCP may then send an alert signal 51 to the selected PSAP 48. The alert signal warns the PSAP that the call is coming, and includes a tag for the call, and further information about the call and the subscriber. The SCP 46 then sends a Return Result message 52 (LOCREQ, ORREQ, or other message, as appropriate) to the serving MSC 43 and includes the tag along with the mobile station location and the identity of the selected PSAP 48. The serving MSC performs a called number analysis at 53 and determines the routing number for the PSAP 48 identified by the SCP, and then connects a trunk at 54 to the PSAP.

The present invention provides an intelligent choice of PSAPs for routing the call. Additionally, the invention sends an alert signal to the selected PSAP warning the PSAP that an emergency call is coming. The invention also provides the PSAP with advanced information regarding the context of the call.

FIG. 4 is a simplified block diagram of the system of the present invention. With reference to FIGS. 3 and 4, the mobile station 41 may place an emergency call via radio signals to a base station 61 which is connected to the serving MSC 43. An emergency call designator 60 includes an indication that the call is an emergency services call. The serving MSC includes an emergency services call analyzer 62 which may be, for example, a called number analyzer, a receiver that receives the indication from the mobile station that the call is an emergency services call, or other call analyzer. The serving MSC then sends the LOCREQ, ORREQ, or other Invoke message 45 to the SCP 46 with the parameters identifying refined cell or sector information of the calling mobile station 41 as well as the analog voice channel or digital traffic channel by which the mobile station is served. This information is received in the SCP and passed to a mobile station location analyzer 63 and an intelligent PSAP selector 64.

The intelligent PSAP selector 64 also receives inputs from a LATA identifier 65, a time-of-day clock 66, a day-of-week calendar 67, and a subscriber database 68. The subscriber database 68 may include information such as the health status of the calling party. The SCP then generates the alert signal 51 which is sent to the selected PSAP 48. A call tagger 69 places a tag identifying the call in the alert signal. The SCP 46 then sends a Return Result message 52 (LOCREQ, ORREQ, or other message, as appropriate) to the serving MSC 43.

It is thus believed that the operation and construction of the present invention will be apparent from the foregoing description. While the method, apparatus and system shown and described has been characterized as being preferred, it will be readily apparent that various changes and modifications could be made therein without departing from the spirit and scope of the invention as defined in the following claims.