System and method for subscriber-controlled call back on busy in a cellular network

[0002] 1. Field of the Invention

[0003] The present invention relates generally to cellular telecommunications systems and methods, and specifically to providing a call back on busy feature to mobile subscribers.

[0004] 2. Background of the Present Invention

[0005] Cellular telecommunications is one of the fastest growing and most demanding telecommunications applications today. There are an increasing number of supplementary services being offered by cellular network operators to further the desirability of cellular communications. For example, one such supplementary feature is the call back on busy feature, which enables a calling mobile subscriber, encountering a busy signal at the called subscriber, to have the call completed when the called subscriber becomes idle, without having to make a new call attempt.

[0006] The European Telecommunications Standards Institute (ETSI) has set forth certain standards for Implementing the call back on busy feature within cellular networks in the GSM 02.93 version 6.0.1 Technical Specification, which was released in 1997. In this Technical Specification, when a calling mobile subscriber encounters a busy indication at the called subscriber, the calling mobile subscriber can activate the call back on busy feature against the called subscriber.

[0007] Upon activation, the network retains the call information and informs the calling mobile subscriber that the call back on busy feature has been activated. When the activation of a call back on busy request is accepted, the network initializes a network-defined callback on busy duration timer. During the time period defined by the duration timer, the network constantly monitors the called subscriber for becoming idle by attempting call setups to the called subscriber.

[0008] If, before the expiration of the network retention timer, the network determines that the called subscriber has become idle, the network waits a short time in order to allow the called subscriber to make any necessary outgoing calls. If the called subscriber does not make any outgoing calls within this time period, the network automatically recalls the calling mobile subscriber and alerts the calling subscriber that the call is a recall to the called subscriber. When the calling mobile subscriber answers, the network automatically generates a call to the now idle called subscriber.

[0009] However, under the current standards, during the time that the called subscriber is busy, the network is spending unnecessary resources in retrying the call setup until the previously busy called subscriber becomes idle. In addition, the duration timer for retrying the call is set by the network, which does not allow the calling mobile subscriber to specify the maximum waiting period after which the call back is not attempted.

[0010] The present invention is directed to telecommunications systems and methods for allowing a calling mobile subscriber to activate a call back on busy feature and specify the maximum waiting period after which the call back is no longer attempted. In addition, during the call back process, the network does not spend unnecessary resources in retrying the call setup. This is achieved through changes in the processing and signaling mechanisms at the Mobile Switching Center/Visitor Location Register (MSC/VLR) nodes in the cellular network. Upon reception of a busy indication at the original MSC/VLR serving the calling mobile subscriber, the original MSC/VLR plays an announcement to the calling mobile subscriber to collect the time interval beyond which the network should cease to attempt the call back.

[0011] Upon reception of this subscriber-defined time interval, the original MSC/VLR sends a message containing calling subscriber identification information, an indication that the call back on busy feature has been activated and the subscriber-defined time interval over which the call back on busy feature is active to the destination MSC/VLR serving the previously busy called mobile subscriber. In response to receipt of this information, the destination MSC/VLR stores the received data in a database therein, initializes a timer with the subscriber-defined time interval and acknowledges reception of the information back to the original MSC/VLR. Thereafter, the original MSC/VLR releases the resources seized by the calling mobile subscriber, which allows the calling mobile subscriber to access other services while waiting for the call back to occur.

[0012] When the destination MSC/VLR determines that the previously busy called mobile subscriber has become idle, e.g., when a traffic channel for the called mobile subscriber is released, the destination MSC/VLR sends a call setup message to the original MSC/VLR, using the information stored in the database. An indication that the call setup message is a result of a call back requested by the calling mobile subscriber is also sent in the call setup message. The original MSC/VLR uses this indication to alert the calling mobile subscriber that the incoming call is a call back from the previously busy called mobile subscriber. Thereafter, a call between the calling and called mobile subscribers is established, as normal.

[0013] In an alternative embodiment, the called subscriber can be a wireline subscriber. In this embodiment, the original MSC/VLR sends the information to an end office associated with the called subscriber. When the end office determines that the called subscriber is idle, e.g., when circuits are released for the called subscriber, the end office sends the call setup message to the original MSC/VLR to establish a call connection between the calling mobile subscriber and the called wireline subscriber.

[0014] The disclosed invention will be described with reference to the accompanying drawings, which show important sample embodiments of the invention and which are incorporated in the specification hereof by reference, wherein:

[0015] FIG. 1 is a block diagram of a conventional cellular network;

[0016] FIG. 2 is a block diagram illustrating the activation of a call back on busy feature for a called mobile subscriber in accordance with preferred embodiments of the present invention;

[0017] FIGS. 3A and 3B are flow charts illustrating the steps for activating the call back on busy feature shown in FIG. 2 of the drawings;

[0018] FIG. 4 is a block diagram illustrating the activation of a call back on busy feature for a called wireline subscriber in accordance with alternative embodiments of the present invention; and

[0019] FIGS. 5A and 5B are flow diagrams illustrating the steps for activating the call back on busy feature shown in FIG. 4 of the drawings.

[0020] The numerous innovative teachings of the present application will be described with particular reference to the presently preferred exemplary embodiments. However, it should be understood that this class of embodiments provides only a few examples of the many advantageous uses of the innovative teachings herein. In general, statements made in the specification of the present application do not necessarily delimit any of the various claimed inventions. Moreover, some statements may apply to some inventive features but not to others.

[0021] With reference now to FIG. 1 of the drawings, there is illustrated a sample cellular network 10 in the Public Land Mobile Network (PLMN), which in turn is composed of a plurality of areas 12, each with a Mobile Switching Center (MSC) and an integrated Visitor Location Register (VLR) (MSC/VLR) 14 therein. The MSC/VLR 14 provides a circuit switched connection of speech and signaling information between a Mobile Station (MS) 20 and the PLMN 10. This can be through one of a plurality of interfaces 21a, 21bor 21c, in which the interface 21cbetween the MS 20 and the MSC/VLR 14 signifies that communication between the MS 20 and he MSC/VLR 14 can be through any network 2D or other type of connection. The MSC/VLR areas 12, in turn, include a plurality of Location Areas (LA) 18, which are defined as that part of a given MSC/VLR area 12 in which the MS 20 may move freely without having to send update location information to the MSC/VLR 14 that controls the LA 18. Each LA 18 is further divided into a number of cells 22. The MS 20 is the physical equipment, e.g., a car phone or other portable phone, used by mobile subscribers to communicate with the cellular network 10, each other, and users outside the subscribed network, both wireline and wireless.

[0022] The MSC/VLR 14 s in communication with at least one Base Station Controller (BSC) 23, which, in turn, is in contact with at least one Base Transceiver Station (BTS) 24. The BTS 24 is the physical equipment, illustrated for simplicity as a radio tower, that provides radio coverage to the cell 22 for which it is responsible. It should be understood that the BSC 23 may be connected to several BTS's 24, and may be implemented as a stand-alone node or integrated with the MSC/VLR 14.

[0023] With further reference to FIG. 1, the PLMN Service Area or cellular network 10 also includes a Home Location Register (HLR) 26, which is a database maintaining all subscriber information, e.g., user profiles, current location information, International Mobile Subscriber Identity (IMSI) numbers, and other administrative information, for subscribers registered within that PLMN 10. The HLR 26 may be co-located with a given MSC/VLR 14, integrated with the MSC/VLR 14, or alternatively can service multiple MSC/VLRs 14.

[0024] With reference now to FIG. 2 of the drawings, in accordance with preferred embodiments of the present invention, a calling MS 20ahas the ability not only to activate a call back on busy feature 40, but also to specify a time interval 60 after which the call back is no longer attempted. To activate the call back on busy feature 40, the calling MS 20amust have a subscriber property 35 associated with it that identifies the calling MS 20aas being capable of requesting activation of the call back on busy feature 40. For example, when the calling MS 20afirst enters the area associated with the serving original MSC/VLR 14a, this property 35 can be downloaded to the MSC/VLR 14afrom a subscriber record 30 within the HLR 26 associated with the calling MS 20a.

[0025] With reference now to the steps listed in FIG. 3A of the drawings, which will be described in connection with FIG. 2 of the drawings, when the calling MS 20ainitiates a call to a called MS 20b(step 300), the original MSC/VLR 14aqueries the HLR 26 associated with the called MS 20bfor a temporary routing number to connect the call to the called MS 20b(step 305). Thereafter, the HLR 26 queries the destination MSC/VLR 14bserving the called MS 20 for the routing number (step 310). The destination MSC/VLR 14bdetermines if the called MS 20bis busy and, if so, returns a busy indication back to the original MSC/VLR 14a(step 315) It should be noted that the HLR 26 that stores the subscriber record (not shown) for the called MS 20bcan be different than the HLR 26 that stores the subscriber record 30 for the calling MS 20a.

[0026] Upon reception of the busy indication, if the calling MS 20ahas the subscriber call back on busy property 35 associated with it (step 318), the original MSC/VLR 14aaccesses an announcement machine 50 and sends an announcement 55 to the calling MS 20athat inquires whether the calling MS 20awould like to activate the call back on busy feature 40 (step 320). Otherwise, the original MSC/VLR 14adisconnects the call (step 330).

[0027] In response to receiving the announcement 55 (step 320), if the calling MS 20aindicates that the call back on busy feature 40 is not needed (step 325), e.g., by the depression of one or more keys on the calling MS 20a, which causes the calling MS 20ato send a decline message (not shown) to the original MSC/VLR 14a, the original MSC/VLR 14adisconnects the call (step 330). If the calling MS 20aindicates that the call back on busy feature 40 should be activated (step 325), e.g., by sending an accept message (not shown) to the original MSC/VLR 14a, the original MSC/VLR 14asends another announcement 58 requesting a time interval 60 from the calling MS 20athat the call back on busy feature 40 should be active (step 335).

[0028] Once the calling MS 20 sends a response message including the time interval 60 (step 340), the original MSC/VLR 14asends a message 70 to the destination MSC/VLR 14b, which includes calling subscriber identification information 72, e.g., the IMSI number for the calling MS 20a, an indication 74 that the call back on busy feature 40 has been activated and the time interval 60 over which the call back on busy feature 40 should remain active (step 345). The destination MSC/VLR 14bstores the received information 72, 74 and 60 in a database 80 therein. It should be noted that the message 70 may also be transited through the HLR 26, as is indicated in FIG. 3A.

[0029] Thereafter, the destination MSC/VLR 14binitializes a duration timer 90 with the received time interval 60 and acknowledges reception of the information back to the original MSC/VLR 14a(step 355). When the original MSC/VLR 14areceives the acknowledgment message, the original MSC/VLR 14areleases the resources seized by the calling MS 20a, which allows the calling MS 20ato access other services even while waiting for the call back to occur. If the calling MS 20awarts to later abort the call back on busy feature 40 invocation, the calling MS 20acan initiate a transaction with the original MSC/VLR 14a, which results in the original MSC/VLR 14amarking that call back on busy feature 40 is not needed anymore.

[0030] Thus, in this case, if the called MS 20bdoes become free later, the original MSC/VLR 14awill not setup a call back to the calling MS 20a.

[0031] With reference now to FIG. 3B (step 358), if the called MS 20bdoes not become idle before the expiration of the duration timer 90 (step 360), the destination MSC/VLR 14bdeactivates the call back on busy feature 40 (step 365). However, if during the duration timer 90 period (step 360), the called MS 20bdoes become idle (step 370), e.g., the destination MSC/VLR 14breleases a traffic channel previously assigned to the called MS 20b, the destination MSC/VLR 14binitiates a delta timer 95 stored within the destination MSC/VLR 14b(step 375), which requires the destination MSC/VLR 14bto wait for a predetermined period of time to allow the called MS 20bto access any necessary services, such as initiating an emergency call, etc.

[0032] If the called MS 20binvokes any service before the expiration of the delta timer 95 (steps 380 and 385), the called MS 20bis marked as busy and the destination MSC/VLR 14bdefers the call back until the called MS 20bonce again becomes idle during the duration timer 90 period (step 360 and 365). It should be noted that the duration timer 90 is not interrupted during the delta timer 95 period, so that if the called MS 20bdoes invoke a service during the delta timer 95 period, and the duration timer 90 has expired at the invocation of the service, the destination MSC/VLR 14bwill deactivate the call back on busy feature 40 (step 365).

[0033] If the called MS 20bdoes not invoke any services before the expiration of the delta timer 95 (step 380), the destination MSC/VLR 14bqueries the HLR 26 associated with the previous calling MS 20afor a routing number for the calling MS 20a, using the calling subscriber information 72 stored in the database 80 (step 390). At the same time, the destination MSC/VLR 14bmarks the called MS 20bas busy (step 391). Upon receipt of the routing information, the destination MSC/VLR 14binitiates a call setup message 100 to the now serving MSC/VLR 14aof the previous calling MS 20a, which in this case is still the original MSC/VLR 14a(step 392). Included within the call setup message 100 is also an indication 110 that the call setup message 100 is the result of a call back requested by the calling MS 20a. As discussed above, if the original MSC/VLR 14ahas stored an indication of cancellation of the call back on busy feature 40, the call back is canceled.

[0034] If the calling MS 20ais now busy (step 393), based on the indication 110 included in the call setup message 100, the original MSC/VLR 14acan choose to disconnect the call or allow the calling MS 20ato choose whether to release any existing calls and accept the call back call (step 394). For example, the original MSC/VLR can alert the calling MS 20athat the call back has arrived using a specific alerting tone. The calling MS 20acan either release the ongoing call or place the ongoing call on hold to accept the call back or ignore the call back, which results in the original MSC/VLR disconnecting the call back call (steps 395 and 330).

[0035] If the previous calling MS 20ais not busy (step 393) or chooses to accept the call back call (step 394), the original MSC/VLR 14amarks that the call back is in progress and uses the indication 110 sent in the call setup message 100 to alert the calling MS 20ain a special manner so that the calling MS 20ais aware that the incoming call is due to the previously requested call back (step 396). For example, the original MSC/VLR 14acan use a specific alert, e.g., a tone, different from the one used for a normal call, for the indication of a recall. Alternatively, the original MSC/VLR 14acan send the indication 110 that the call is a recall or send the indication 110 as part of caller ID information, if the calling MS 20ahas subscribed to the caller ID feature.

[0036] When the calling MS 20aanswers the call back, the original MSC/VLR 14ainforms the destination MSC/VLR 14bthat the connection to the previous calling MS 20ahas been established. Thereafter, the destination MSC/VLR 14bpages the called MS 20band establishes a call connection between the calling MS 20aand the called MS 20b(step 398).

[0037] With reference now to FIG. 4 of the drawings, which will be described in connection with the steps listed in FIGS. 5A and SB of the drawings, in an alternative embodiment, the called subscriber could be a wireline subscriber. In this case, when the calling MS 20 initiates a call to a destination terminal within the Public Switched Telephone Network (PSTN) 15 (step 500), the MSC/VLR 14 serving the calling MS 20 routes the call to a Gateway Mobile Switching Center (GMSC) 150 within the PLMN 10 (step 505). The GMSC 150 determines that the call is to the PSTN 15 and routes the call to an end office 160 connected to the destination terminal 170 (step 510).

[0038] If the destination terminal 170 is busy, e.g., involved in another call, the end office 160 returns a busy indication to the MSC/VLR 14 via the GMSC 150 (step 515). Upon reception of the busy indication, if the calling MS 20 has the subscriber call back on busy property 35 associated with it, the MSC/VLR 14 accesses the announcement machine 50 and plays the announcement 55 to the calling MS 20 that inquires whether the calling MS 20 would like to activate the call back on busy feature 40 (step 520).

[0039] If the calling MS 20 indicates that the call back on busy feature 40 is not needed (step 525), the MSC/VLR 14 disconnects the call (step 530). Otherwise, the MSC/VLR 14 plays another announcement 58 requesting a time interval 60 from the calling MS 20 that the call back on busy feature 40 should be active (step 535). Once the MSC/VLR 14 receives the timer interval 60 from the calling MS 20 (step 540), the MSC/VLR 14 sends a message 70 to the end office 160, which includes calling subscriber identification information 72, e.g., the IMSI number for the calling MS 20, an indication 74 that the call back on busy feature 40 has been activated and the time interval 60 over which the call back on busy feature 40 should be active (step 545). The end office 160 stores the received information 72, 74 and 60 in a database 80 therein. Thereafter, the end office 160 initializes the duration timer 90 with the received time interval 60, and acknowledges reception of the information back to the MSC/VLR 14 (step 555). As stated above, when the MSC/VLR 14 receives the acknowledgment message, the MSC/VLR 14 releases the resources seized by the calling MS 20, which allows the calling MS 20 to access other services while waiting for the call back to occur. f the calling MS 20 wants to later abort the call back on busy feature 40 invocation, the calling MS 20 can initiate a transaction with the original MSC/VLR 14, which results in the original MSC/VLR 14 marking that call back on busy feature 40 is not needed anymore. Thus, in this case, if the called terminal 170 does become free later, the original MSC/VLR 14 will not setup a call back to the calling MS 20.

[0040] With reference now to FIGURE SB (step 558), if the destination terminal 170 does not become idle before the expiration of the duration timer 90 (step 560), the end office 160 deactivates the call back on busy feature 40 (step 565). However, if, during the duration timer 90 period (step 560), the destination terminal 170 becomes idle (step 570), e.g., the end office 160 releases circuits previously assigned to the destination terminal 170, the end office 160 initiates the delta timer 95 (step 575) in order to allow the destination terminal 170 to access any necessary services, such as initiating an emergency call, etc.

[0041] If the destination terminal 170 invokes any service before the expiration of the delta timer 95 (steps 580 and 585), the end office 160 defers the call back until the destination terminal 170 once again becomes idle during the duration timer 90 period (steps 560 and 570). Otherwise, at the expiration of the delta timer 95 (step 580), the end office 160 sends a call setup message 100 including the indication 110 to the GMSC 150, using the calling subscriber information 72 stored in the database 80 (step 590). The GMSC 150 queries the HLR 26 associated with the previous calling MS 20 for a routing number for the calling MS 20 (step 591), and upon receipt of the routing information, routes the call setup message 100, including the indication 110, to the MSC/VLR 14 of the calling MS 20 (step 592). As discussed above, if the original MSC/VLR 14 has stored an indication of cancellation of the invocation of the call back on busy feature 40, the call back is canceled.

[0042] If the calling MS 20 is now busy (step 593), based on the indication 110 included in the call setup message 100, the MSC/VLR 14 can choose to disconnect the call or allow the calling MS 20 to choose whether or not to release any existing calls and accept the call back call (step 594). If the calling MS 20 is not busy (step 593) or chooses to accept the call back call (step 594), the MSC/VLR 14 marks that the call back is in progress and uses the indication 110 sent in the call setup message 100 to alert the calling MS 20 in a special manner so that the calling MS 20 is aware that the incoming call is due to the previously requested call back (step 596). Otherwise, the MSC/VLR 14 disconnects the call back call (step 595).

[0043] When the calling MS 20 “answers” the call, the MSC/VLR 14 informs the end office 160 via the GMSC 150 that the connection to the calling MS 20 has been established. Thereafter, the end office 160 rings the destination terminal 170 and establishes a call connection between the calling MS 20 and the destination terminal 170 (step 598).

[0044] As will be recognized by those skilled in the art, the innovative concepts described in the present application can be modified and varied over a wide range of applications. Accordingly, the scope of patented subject matter should not be limited to any of the specific exemplary teachings discussed, but is instead defined by the following claims.