MXPA99010362A - Proactive communication of mobile station position information following inter-exchange handoff - Google Patents

Abstract

The present invention comprises a system and method for proactively conveying mobile station position information with a network. In the context of completing an inter-exchange handoff of a mobile station communication, a request for facilities (such as a communications traffic channel) (126) is made by an anchor mobile switching center (18(1)) of a serving mobile switching center (18(2)). This request for facilities includes an indication that the anchor mobile switching desires to be kept up-to-date on mobile station position. In particular, the indication asks the serving mobile switching center to monitor mobile station position (142) as well as changes thereto, and inform (148) the anchor mobile switching center when the monitored position changes (146) by a request specified predetermined degree. In response to the indication, the serving mobile switching center detects mobile station position, compares the detected position against a prior detected position, and reports the current position to the anchor mobile switching center if the current and prior positions differ by at least the predetermined degree.

Description

"PROACTIVE COMMUNICATION OF POSITION INFORMATION OF MOBILE STATION AFTER DELIVERY OF INTER-EXCHANGE" BACKGROUND OF THE INVENTION TECHNICAL FIELD OF THE INVENTION The present invention relates to locating the geographical position of a mobile station operating within a cellular telephone network and, in particular, to proactively provide geographic position information after inter-exchange delivery.

DESCRIPTION OF THE RELATED TECHNIQUE Conventional cell phone technology, by itself, does not include the ability to accurately indicate, with any reasonable or useful degree of accuracy, the location of the mobile subscriber. For example, using a conventional cellular telephone network, the degree of accuracy of the typically available position information is to identify the cell within which a mobile station is located. Some cells, however, have a coverage radius in excess of one kilometer. In this way, the identification of cell location provides correspondingly very little in case of some help to actually locate the position of the subscriber. Accordingly, a number of systems have been proposed to assist in the determination of the location and to provide more accurate position information. A system uses a triangulation or curvature process to determine an approximate location of the caller through an analysis of signal strength measurements and / or propagation delay times of cellular communications. Another system uses the existing Global Positioning System (GPS) with a GPS receiver attached to the cell phone to obtain geo-coordinates for the mobile station. Although many systems have been proposed to more accurately identify the location of a mobile station, it is equally important that position information determined as independent of its accuracy is provided and distributed through the network when necessary. Consider, for example, the situation where an agency to enforce the law wants to know the location of either a mobile station or the person using the mobile station. In this way, for a mobile station placed in a stolen vehicle, the law enforcement agency would like to monitor the location of the mobile station, and therefore the stolen vehicle itself, to help apprehend the thief. Alternatively, an agency to enforce the law may have an interest in monitoring not only cell phone communications made by the suspect of having subscribed to the cellular service but also the locations from which those calls are occurring. It is then necessary for the agency to enforce the law to be able to send instructions to the cell phone network to make a determination of the position in a specific mobile station and to transmit that information again to be used to track the suspect. In addition, cellular subscribers now frequently use their mobile stations to be emergency calls (911). Unlike conventional landline phones, mobile stations do not have a fixed address related to a location that can be obtained through the public safety answering point (PSAP) when an emergency call is made. It is therefore necessary that the public safety answering point be able to instruct the cell phone network to provide updated position information on a specific mobile station from which an emergency call originates and to pass that information back to be used in the dispatch of an emergency service help. In yet another example, with the implementation of an Intelligent Network (IN) architecture, a number of new service features that require knowledge of the position of the mobile station are being provided. For example, with the sending of the call that depends on the location, the number C to which a call is transferred depends on where the network of the called mobile station is placed. The management of the network that depends on the location is also becoming a matter with respect to the service actions taken by other network nodes such as the home location register (HLR). It is also necessary then that a network node, such as a service control point in an Intelligent Network or a home location register, be able to send signals to the cell phone network to provide the updated position information in a specific mobile station and transfer the information again to be used to activate or complete the provision of the service. In conventional call handling situations, obtaining the location information does not present a significant problem since the requesting entity (node to enforce the PSAP or network node) can make a request from the mobile switching center that serves a cellular call for location information. The process of obtaining location information is significantly complicated, however, when an inter-exchange delivery of the cellular call occurs. The requests in this case can not be directed to the mobile switching center that gives recent service. The reason for this is that the mobile switching center that originally serves (that is, the anchor) that handles the calls remains in the call connection after the delivery occurs, and the knowledge of this mobile switching center that gives Service currently can not be obtained easily. There is a need then for a mechanism that allows the mobile service switching center to provide location information for anchoring the mobile switching center after an inter-exchange entry.

SUMMARY OF THE INVENTION In the context for completing an inter-exchange delivery of a communication from the mobile station, a request for ease of communication (such as a communications traffic channel) is issued from an anchor exchange to a service exchange recently. This request further requests that the service exchange monitor the position of the mobile station as well as the changes thereto, and informs the exchange of the anchor when the supervised position changes by means of a specified predetermined degree request. In response to this, the service exchange monitors the position of the mobile station, compares a current position against a previous position, and discloses the current position to the anchor exchange if the current and previous positions differ by at least the request of predetermined degree specified.

BRIEF DESCRIPTION OF THE DRAWINGS A more complete understanding of the method and apparatus of the present invention can be obtained by referring to the following Detailed Description when taken in conjunction with the accompanying Drawings, wherein: Figure 1 is a cell diagram illustrating an exemplary cell configuration for a cellular telephone network wherein the present invention can be implemented. Figures 2A-2B are diagrams of network operation and message flow illustrating the operation of the network of Figure 1 in relation to an inter-exchange delivery; and Figure 3 is a diagram of network operation and message flow illustrating the operation of the network of Figure 1, in relation to a proactive communication of the position information of the mobile station after a delivery of data. exchange.

DETAILED DESCRIPTION OF THE DRAWINGS Reference is now made to Figure 1 wherein a cell diagram illustrating an exemplary cell configuration for a cellular telephone network 10 in which the present invention can be implemented is shown. The cellular telephone network 10 operates in accordance with one of a number of known air interface types including, for example, a frequency division multiple access protocol (FDMA) or a time division multiple access protocol (TDMA) ), which provide means for the use of at least one control channel and a plurality of traffic channels per cell 12. In network 10, a base station 14 is provided for each of the cells 12. The stations 14 The base stations are coupled in simultaneous communications with the multiple mobile stations 16 operating more or less within the area of the associated cell 12. The control channel assigned to each cell 12 is used to carry system control messages between the base station 14 and the mobile stations 16 placed in proximity and also aids in the network with the reselection of the cell of the mobile station. These control messages include call origins, radiolocation signals, radiolocation response signals, location registration signals, traffic channel assignments, maintenance instructions, and cell selection or re-selection instructions. The traffic channels provided in each cell 12 are used to carry the subscriber's voice or data communications between the base station 14 and the mobile stations 16 placed next to each other. The base stations 14 also communicate via signal sending links and voice trunks 22 with a central control station, which is commonly referred to as the mobile switching center 18, which functions to control the operation of the network 10. The mobile switching centers 18 are interconnected with each other and with the public switched telephone network (PSTN) 20 by the signal sending links and the voice trunks 22. The mobile switching centers 18 operate for selectively connecting the subscriber's voice and data communications with the mobile stations 16 through their base stations 14. In this way, the mobile switching centers 18 control the operation of the system through and in response to the transmission of the control messages through the control channels to establish in the traffic channels the calls that are originated by or are given by completed in mobile stations 16. The mobile switching centers 18 further control, through and in response to the control and traffic channel transmissions, the delivery of a subscriber communication from a traffic channel of a cell 12 to a traffic channel of another custom-made cell. that the mobile station 16 of the subscriber is routed through the cellular service area during a running communication. As the mobile stations 16 move within the service area of the network 10, cases arise where a mobile station passes between two cells 12 served by the same mobile switching center 18 or a cell served by a first center. 18 (1) mobile switching to another cell served by a second mobile switching center 18 (2). When moving between the cells 12 in any case, the mobile stations 16, together with the information of the base station 14 and the orders exchanged with and between the mobile switching centers 18, have an opportunity through the delivery to change the base station through which cellular radio communications are being carried out. Reference is now made in conjunction with Figures 1 and 2A-2B where Figures 2A-2B are network flow and operation flow diagrams illustrating the operation of network 10 of Figure 1, in relation to the delivery of interchange of a mobile station 16 (1) from a cell 12 (1) served by a first mobile switching center 18 (1) to a cell 12 (2) served by a first mobile switching center 18 (2). The mobile station 16 (1), which operates if capable, in accordance with the delivery principles aided by the known mobile station (MAHO), periodically measures 100 resistance of the downlink signal in the traffic channel (from the cell 12 (1) served by a first mobile switching center 18 (1) that is currently being used, and also periodically makes measurements 102 of the resistance of the downlink signal in the control channels of the cells 12 identified by the network, including the cell 12 (2) served by a second mobile switching center 18 (2), which is adjacent to the cell 12 (1). These resistance or signal strength measurements are disclosed 104 to the base station 14 (1) for the cell currently serving 12 (1). The base station 14 (1) simultaneously carries out measurements 106 of the intensity or resistance of the uplink signal in the traffic channel which is currently being used by the mobile station 16 (1). They are the only measurements 106 made with respect to capable mobile stations 16 that are not MAHO. The base station 14 (1) processes that the mobile station 16 (1) disclosed 104 downlink signal strength measurements (100 and 102), if available, and the base station carried out measurements (106 ) of uplink signal intensity to determine first if a delivery (action 108) is necessary and second, if the answer is yes, to which cell (s) (candidates) could and / or delivery should preferably occur (action 110) ). It is now assumed that the base station 14 (1) determines to deteriorate the measured signal intensities of uplink and / or downlink that a delivery is necessary. It is further assumed that an identification 110 of the cell 12 (2) is made as the preferred candidate cell (of blank) for delivery. A request 112 for delivery including information comprising an identification of cell 12 (1), which currently serves, the traffic channel being used for communication with mobile station 16 (1) in cell 12 (1), and the target cell 12 (2) for delivery, then sent by the base station 14 (1) to the mobile service switching center 18 (1). A delivery if approved in this case would comprise an inter-exchange delivery because the target cell 12 (2) is served by a mobile switching center 18 (2) different from the mobile switching center 18 (1) which gives service to the current cell 12 (1). The foregoing description is only an example of the procedure used to make the determination to institute a delivery. Of course it will be understood that more than one target cell 12 can be identified by the process of action 110, for consideration of additional delivery. In the service mobile switching center 18 (1) currently sends a message 114 to the mobile switching center 18 (2) associated with the target cell 12 (2) requesting verification of the station's communication capacity of base 14 (2) with mobile station 16 (1). It should be understood that multiple messages 114 may be sent if more than one target cell 12 has been identified for consideration of additional delivery. The message 114, similar to the request 112 sent by the base station 14 (1), includes the information comprising an identification of the cell 12 (1) currently serving and the traffic channel that is being used in the communication with the mobile station 16 (1) in cell 12 (1). In response to this, the mobile switching center 18 (2) sends a message 116 to the base station 14 (2) so that the target cell 12 (2) makes a measure of the strength of the verification signal (action 118) in the traffic channel that is currently being used by the mobile station 16 (1) in the current service cell 12 (1). The base station 14 (2) then discloses 120 the results of the verification signal strength measurement to the mobile switching center 18 (2). An evaluation of the intensity measurement of the verification signal is then made (action 121) by the mobile switching center 18 (2) to confirm the location of the mobile station in view of the expected signal strengths. After evaluation, the mobile switching center 18 (2) sends 122 the results of the verification measurement back to the mobile switching center 18 (1). The results are then processed (action 124) by the mobile switching center 18 (1) to determine whether a delivery must be made to the target cell 12 (2). If the determination is affirmative with respect to the target cell 12 (2), and if no other target cell is identified as a better selection, the mobile switching center 18 (1) sends a message 126 to the mobile switching center 18 (2) requesting the assignment (and reservation) of a traffic channel for delivery to target cell 12 (2). A traffic channel is retained (action 128), and then both the base station 14 (2) and the mobile switching center 18 (1) are informed 130 of the assignment by the mobile switching center 18 (2) of the channel of traffic in the white cell 12 (2). The mobile switching center 18 (1) then sends a message 132 to the mobile station 16 (1) via the base station 14 (1) for the current service cell 12 (1) with a delivery command that directs the mobile station to switch to the assigned traffic channel in the target cell 12 (2). The mobile station 16 (1) then tunes in and gives access 134 to the assigned traffic channel. When the base station 14 (2) detects the access of the mobile station (action 136), the mobile switching centers 18 (1) and 18 (2) are informed 138, and the call is switched 140 to the mobile switching center 18 (2) for additional handling to complete the delivery procedure. Reference is now made in combination to the Figures 1 and 3 wherein Figure 3 is a diagram of network operation and message flow illustrating the operation of network 10 of Figure 1 in relation to a proactive communication of the position information of mobile station 16 ( 1) after an inter-exchange delivery. For purposes of this discussion and the illustration of Figure 3, the steps and actions 100-124 of Figures 2A and 2B are incorporated by reference. After a determination that the target cell 12 (2) is the best selection for delivery, the mobile switching center 18 (1) sends a message 126 'to the mobile switching center 18 (2) requesting assignment (and reservation) ) of a traffic channel for delivery to target cell 12 (2). This message 126 'differs from the message 126 of Figures 2A-2B in that it includes additional parameters indicating that the first mobile switching center 18 (1) wishes to be kept updated as to the position of the mobile station 16 (1). If the message 126 comprises the management message of the TIA / EIA IS-41 facilities, the message 126 'may comprise the same message with the related mobile station position parameters included in any of the available or newly created fields. The included parameters not only provide an indication that the first mobile switching center 18 (1) wishes to be kept updated as to the mobile station position 16 (1), but also specifies a degree of change in the position of the mobile station which must occur before the first mobile switching center is to be provided with a position update.

For the purposes of this discussion and the illustration of Figure 3, the steps and actions 128-140 of Figures 2A-2B are also incorporated by reference. After the switching 140 of the call to the mobile switching center 18 (2), the second mobile switching center 18 (2) monitors the position of the mobile station 16 (1) (action 142). This monitoring, for example, may comprise making determinations of the position of the periodic mobile station 16 (1) (action 144). A comparison is then made in the action 146 of whether one of the current determinations of the position determinations differs from an immediately prior one of the position determinations by the degree specified in the message parameters 126 '. If so, a location identification message 148 is generated and sent from the second mobile switching center 18 (2) to the first mobile switching center 18 (1). The process then returns to continue with the supervision 144 of the position of the mobile station 16 (1), together with the determination 146 of the changes of the position of the mobile station in excess of the degree specified in the message 126 '. The determination of the position of the mobile station 16 (1) can be done by the mobile switching center 18 (2) in accordance with any of a number of known methods. For example, one way to determine the position is to depend on the information provided from a transceiver of the Global Positioning System (GPS) connected to the mobile station, with geo-coordinates determined by the system being extracted by the mobile station and transmitted to the center of mobile switching. A second way to determine the position is to use the area of the cell where the mobile target station is currently located, with the cell identification information for the base station that is currently serving the switching center mobile. A third way to determine the position is to use measures (signal strength or time advance) made by the base stations in the vicinity of the mobile station with the acquired measurement information being transmitted to the mobile switching center. A fourth way to determine the position is to use the measurements (signal strength or time advance) made by the mobile station itself, with the acquired measurement information transmitted to the mobile switching center. A fifth way to determine the position is to depend on a determination made by a separate location system, such as the Doppler satellite, LORAN-C, address locators, timing of arrival triangulation processors (curvature), or triangulation processors. signal strength (curvature), with the acquired measurement information being transmitted to the mobile switching center. Once received by the mobile switching center, the measurement information is processed in the manner described above in order to determine the changes of position of the mobile station in excess of the specified degree of the message 126 '. The degree, for example, may comprise a predetermined geographical distance, or a change in the location of the cell. The message 126 'is sent, instead of the message 126 (Figures 2A-2B), through the anchor mobile switching center 18 (1) in those cases where it is aware that it is the position of the current mobile station. For example, such is the case when the call is being monitored by an agency that enforces the law, when a call includes a public service answering point (PSAP) as a party, or when the call can invoke a particularity of service That depends on the location. In this regard, the mobile switching center of the anchor can be programmed to automatically recognize the call situations where the current mobile station is concerned or alternatively it can receive an instruction in relation to the initial call established from the monitoring center of the mobile station. the agency to enforce the law, the public service answer point, the service control point or the home location register, to keep abreast of the position of the mobile station. In response to any situation, message 126 'is sent in connection with a delivery procedure. Even though illustrated in the accompanying Drawings a preferred embodiment of the method and apparatus of the present invention and described in the foregoing Detailed Description, it will be understood that the invention is not limited to the embodiment disclosed but is capable of numerous rearrangements, modifications and substitutions without departing from the spirit of the invention as indicated and defined by the following claims.

Claims (12)

CLAIMS:

1. In connection with an inter-exchange delivery of a cellular call from the mobile station from a first exchange to a second exchange, a method for keeping the first exchange updated at the mobile station's position during a call comprising the steps of: sending signals to the second exchange from the first exchange with an instruction to keep the first exchange exchanged at the position of the mobile station; monitor by the second exchange of the position of the mobile station during the call; comparing the second exchange of the position of the current mobile station with a position of the previous mobile station; and sending signals to the first exchange from the second exchange with the position of the current mobile station if the position of the current mobile station differs from the position of the previous mobile station by a predetermined degree. The method according to claim 1, wherein the step of sending signals of the second exchange comprises the step sending signals to the second exchange with the instruction wherein the instruction includes an indication of a predetermined degree whereby the position of the Current mobile station should differ from the position of the previous mobile station. The method according to claim 1, wherein the instruction to maintain the update of the first exchange in the position of the mobile station is embedded with a message addressed to the facilities sent from the first exchange to the second exchange. The method of claim 1, wherein the step of monitoring comprises the step of periodically making position determinations of the mobile station. 5. A method for inter-exchange delivery comprising the steps of: detecting a need for a mobile station cellular communication delivery that is currently being handled through the first exchange; identify a cell served by the second intermediate as a target for delivery; transmitting a message from the first exchange to the second exchange requesting the assignment of a traffic channel in the cell to carry the cellular communication to the mobile station requesting further the message that the second exchange maintains the update of the first exchange as to the position of the mobile station during cellular communication of the mobile station; switching the cellular communication of the mobile station to the assigned traffic channel; and communicating the position of the mobile station from the second exchange to the first exchange during cellular communication of the mobile station. The method of claim 5, wherein the step of communicating the position of the mobile station comprises the steps of: monitoring by the second exchange of the position of the mobile station during cellular communication of the mobile station; compare by means of the second exchange of the position of the current mobile station with a previous mobile station position; and sending signals from the first exchange from the second exchange with the position of the current mobile station if the position of the current mobile station differs from the position of the previous mobile station by a predetermined degree. The method of claim 6, wherein the step of transmitting comprises the step of sending signals to the second exchange with respect to maintaining the update of the first exchange at the position of the mobile station including an indication of the predetermined degree by which the position of the current mobile station should differ from the position of the previous mobile station. The method of claim 6 wherein the step of monitoring comprises the step of periodically making position determinations of the mobile station. 9. The method of claim 5 wherein the message comprises a message to direct facilities or facili- ties sent from the first exchange to the second exchange., with the message including the request to maintain the update of the first exchange in the position of the mobile station. 10. A cellular communication system, comprising: a first exchange through which cellular communication of the mobile station is initially being handled, and from which a request is issued to maintain the update at the mobile station's position; and a second exchange through which cellular communication of the mobile station is currently being handled after an inter-exchange delivery, the second exchange, operates in response to the request issued by the first exchange to monitor the position of the exchange. the mobile station during cellular communication of the mobile station and reporting a position of the current mobile station to the first exchange if the position of the current mobile station differs from the position of the previous mobile station by a predetermined degree. The method of claim 10 wherein the request comprises a message addressed to the facilities sent from the first exchange to the second exchange. The method of claim 10 wherein the request includes an indication of the predetermined degree by which the position of the current mobile station should differ from the position of the previous mobile station.