Obtaining data for calls made by a specific/cellular mobile station

[0002] This invention relates to arrangements for obtaining data for calls made by a selected mobile station.

[0003] 1. Problem

[0004] The control of a cellular mobile switching system is necessarily highly distributed between a centralized mobile switching center and a plurality of base stations, each for communicating with mobile stations in a surrounding area (cell). Tracking down software problems, or problems associated with incorrect data at a base station, is particularly difficult in such a distributed system, wherein a mobile station is moving unpredictably among many base stations. A powerful diagnostic tool for detecting such problems and obtaining information necessary to suggest a correction, is the obtaining of all call data for calls made by a particular mobile station which has given indications that the processing of calls for that station is not proceeding smoothly. An example of such an indication is the rejection of a hand-off request initiated by a requesting base station by the requested base station.

[0005] In the prior art, all such information about calls made from, or to, a selected mobile station are obtained by having a flag associated with that station in all base stations that may serve that mobile station. Since the mobile station is unfettered in its movements, a problem of the prior art is that setting up of such flags without missing base stations that may control calls for the selected mobile station is cumbersome, and likely to set an excessive number of flags. Each flag must be checked on every message from a base station in order to insure that data is collected only for a selected mobile station. In most cases, the number of selected main stations is quite small, but the effect on processing capacity of having to check for every such message whether the mobile station of the message is a flag station, is substantial and adverse. A problem of the prior art is that there is no efficient method of obtaining all or most of the data for a mobile station.

[0006] 2. Solution

[0007] Applicant has further analyzed this problem, and has recognized that it is only necessary to maintain a flag, or monitor indication, in a base station for a selected mobile station whenever that base station is actually controlling actions of the mobile station.

[0008] Applicant has solved the above problem, and has made a contribution over the prior art by his invention, wherein a monitor indication is created in a base station whenever the selected mobile station is registered in, or is controlled by that base station; when a mobile station is handed off from one base station to another, the hand-off message set includes an indication that the mobile station being handed off is a selected mobile station whose call record data is being monitored. Advantageously, only the base stations actually controlling a call of the selected mobile station have an indicator for that mobile station, and the search to determine whether a mobile station is being monitored is expedited. Advantageously, such an arrangement minimizes software changes in order to implement Applicant's invention.

[0009] In accordance with one alternate embodiment of Applicant's invention, the flag indicator is transmitted in one bit of a proprietary protocol message, during the process of handing off a mobile station from one base station to another.

[0010] FIG. 1 illustrates a mobile switching system, and shows the key messages for implementing Applicant's invention; and

[0011] FIGS. 2-3 are flow charts illustrating the method of Applicant's invention.

[0012] FIG. 2 is a block diagram illustrating the operation of Applicant's invention. Mobile switching center 10 controls and switches for a plurality of base stations, two of which are BS1 and BS2, as shown in the diagram. MSC 10 maintains a monitor list 9, of mobile stations whose call processing actions are being recorded for analysis. Each base station has a controller, such as controller 30 of base station 1, and within that controller is maintained a monitor list 33, of the mobile stations being monitored. MSC 10 is connected to a data and switching network 11, comprising a CCS 7 data network for transmitting signaling information and data, and a public switched telephone network for transmitting communication signals to other switching systems, (not shown). Connected to the network 11, is an operation support system 12, for controlling operations, administration, and maintenance for MSC 10 and its' base stations. The operations support system 12, can be the source of a request to monitor a particular mobile station. Also shown, is a mobile station 20, which is initially in radio contact with base station 1, but which subsequently, moves to the area of base station 2, and is subsequently, in radio contact with base station 2. The radio contact between mobile station 20 and base station 1, is shown by the broken line, 21.

[0013] Also shown, on FIG. 1, are four types of messages. Message 15 is a message from operation support system 12 to MSC 10, requesting that a particular mobile station be monitored. The message includes the identification of the mobile station 16, and a request that this station be monitored, 17.

[0014] Message 40 is a similar type of message sent from base station 1 to base station 2, at the time mobile station 20 is handed off to base station 2. Message 40 includes the mobile station identifier 41, and the monitor request, 42. Message 45 is transmitted from a base station serving a monitored mobile station, to report the monitoring data. Message 45 comprises the mobile station identifier 46, and the call data being transmitted, 47. This call data can subsequently, be transmitted to the operation support system, 12.

[0015] FIG. 2 illustrates the operations performed in a mobile switching center. The MSC receives, or generates, a monitor request, (Action Block 201). The MSC can receive the monitor request from operation support system 12, or it may detect some condition under which the monitoring of the mobile station involved in the call is automatically initiated. The MSC places the mobile station of the request on its monitor request list, (Action Block 203). Subsequently, the MSC receives a mobile station origination request, or call termination request, (Action Block 205). Test 207 is used to determine whether the mobile station of Action Block 205 is on the monitor request list. If so, then the MSC transmits a monitor request message, such as message 35, to the base station serving the mobile station that originated. If the monitor station is not on the request list, or following the execution of Action Block 209, the call is processed as in the prior art, (Action Block 211).

[0016] If the MSC receives or generates an indication that monitoring of a mobile station is to be abandoned, (Action Block 221), then the mobile switching center removes the mobile station from the monitor request list, (Action Block 223). The request that monitoring is to be abandoned is likely to come from operation support system 12.

[0017] The MSC receives call data message for monitored mobile stations, (Action Block 230). This information is received in messages such as message 45. The MSC places the call data message in a record for the mobile station of the call data message, (Action Block 232). Subsequently, periodically, the MSC transmits call record data to the operation support system, (Action Block 234). Action Blocks 230, 232, and 234 are in the prior art.

[0018] FIG. 3 illustrates actions performed in the base station. The base station receives a monitor request message, (Action Block 301), such as message 35, or message 40, from the MSC or another base station, respectively. It will receive the monitor request message from the MSC upon origination of a call by the identified mobile station; it will receive the request from another base station as part of a hand-off procedure. The base station places the mobile station in its own monitor request list, (Action Block 303).

[0019] Subsequently, when the base station detects a reportable event for a mobile station, (Action Block 305), it will test whether that mobile station is on the monitor list, (Test 307). If the result of Test 307 is positive, then the message is sent to the MSC reporting the reportable event, (Action Block 309). Following the execution of Action Block 309, or if the mobile station is not on the monitor list, processing of the call proceeds as in the prior art, (Action Block 311), until the base station detects another reportable event, (Action Block 305). Action Blocks 305, 307, 309, and 311 are in the prior art.

[0020] When the base station hands off a call to another base station, (Action Block 321), it tests whether the mobile station of that call is on the monitor list, (Action Block 323). If so, then the base station sends a monitor request message to the handed off base station, (Action Block 325), and removes the mobile station from its monitor list, (Action Block 327). Following the execution of Action Block 327, or if the mobile station is not on the monitor list, then the call is processed as in the prior art, (Action Block 329). When the mobile call is terminated, (Action Block 341), a test is made whether the mobile station is on the monitor list of this base station, (Test 343). If so, the mobile station is removed from the monitor list for that base station, (Action Block 345). Following the execution of Action Block 345, or if the mobile station is not on the monitor list, the call is processed as in the prior art.

[0021] In this particular embodiment, separate messages are used to request that a mobile station be monitored by a base station. In alternative embodiments, this information can be transmitted as part of an originating request message from the MSC, or as part of a hand-off message from another base station through the use of a dedicated single bit indicator, to indicate whether or not monitoring is requested. The single bit indicator would, of course, be sent along with a message, which either directly or indirectly specified the identity of the mobile station.

[0022] In another alternative embodiment of Applicant's invention, an indication of whether a call is being monitored is maintained in the call record for that call. Advantageously, such an arrangement means that no supplementary list need be checked in order to determine whether a reportable event is to be reported to the MSC.

[0023] The above is a description of one preferred embodiment of Applicant's invention. Many other arrangement will be apparent to those of ordinary skill in the art, without departing from the scope of Applicant's invention. Applicant's invention is, therefore, only limited by the attached Claims.