Abstract:
In order to reduce the traffic on the paging channel, the system for reducing paging channel occupancy for message waiting indication in mobile switching centers allows the Message Waiting Notification process to determine a last zone in which the Mobile Subscriber was located and only transmit the Message Waiting Indication to the cells within that zone. This eliminates message transmission on the paging channel of cells which are not likely to have the Mobile Subscriber Station residing in their service area. Multiple retries can be attempted and if the last retry is being activated, the paging can be extended to cover all zones in the Mobile Switching Center. The sharing of information about when a mobile has responded to a message waiting count between the Serving MSC and the Home MSC also reduces the paging channel occupancy. The method of not sending a message waiting notification when a mobile has already acknowledged the message count greatly reduces the impact of Message Waiting Notification on the paging channel occupancy. In particular, border cell areas where the Mobile Subscriber Station can bounce between MSCs is where the biggest benefit can be derived.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application is a continuation-in-part of U.S. patent application Ser. No. 10/610,174, filed Jun. 30, 2003 and titled “System For Providing Message Waiting Indication Updates In A Cellular Communication Network”. 
     
    
     FIELD OF THE INVENTION  
       [0002]     This invention relates to cellular communication networks and in particular to a system that provides message waiting notification update messages to Mobile Subscriber Stations that roam among a number of Mobile Switching Centers within the cellular communication network.  
       PROBLEM  
       [0003]     It is a problem in cellular communication networks to efficiently utilize the paging channel, also known as the forward control channel. The paging channel is a critical resource, which is used for a multitude of purposes, including call origination, call delivery, and the delivery of message waiting indications to the Mobile Subscriber Station. The number of calls that a Mobile Switching Center can handle is determined by the capacity and the present occupancy of the paging channel. Therefore, any reduction in the use of the paging channel results in a significant performance improvement for the Mobile Switching Center.  
         [0004]     In order to reduce the effective occupancy of the paging channel, Mobile Switching Centers divide their coverage area into a plurality of zones, each of which contains a plurality of cells. As the Mobile Subscriber Station moves from one zone to another in the Mobile Switching Center, it accesses the Mobile Switching Center via an autonomous registration process which indicates to the Mobile Switching Center that the Mobile Subscriber Station has moved to a different zone. This process limits the number of cells to which call delivery pages are transmitted and thereby the traffic on the paging channel for the remaining cells in the Mobile Switching Center.  
         [0005]     However, while the use of zones provides an improvement in the utilization of the paging channel, the use of this channel for message waiting indications has a far more significant impact on the Mobile Switching Center. In cellular communication networks, a Mobile Subscriber subscribes to have calls delivered to their Mobile Subscriber Station. In addition, the Mobile Subscriber can receive additional features, including Calling Party Number Identification (Caller-ID), Call Forwarding, and Voice Mail. For example, the Mobile Subscriber may not be available to answer an incoming call or may decide not to answer an incoming call based on the Caller ID. In this situation, the calling party is redirected to a Voice Mail system, which stores messages for the Mobile Subscriber, as input by the calling parties. Each time a calling party leaves a message in the Voice Mail system, data that identifies the number of messages residing in the Voice Mail system is updated and the Voice Mail system creates an incall message or other signaling message containing data that notes the number of messages waiting for retrieval for the Mobile Subscriber. This data is transmitted to the Mobile Subscriber&#39;s Home System, which then attempts to deliver a notification to the Mobile Subscriber listing the number of messages waiting for retrieval for the Mobile Subscriber. This notification is delivered by the Mobile Switching Center broadcasting a Message Waiting Notification in a signaling message to the Mobile Subscriber over all paging channels in the Mobile Switching Center. All of the paging channels of all of the cells in the Mobile Switching Center carry this notification, even though the Mobile Subscriber Station is presently served by only one of these cells. These Message Waiting indication messages are twice the size of call delivery pages and run at a higher priority, resulting in incoming calls being dropped when the message waiting indication traffic overloads the paging channel.  
         [0006]     A further problem with the present Message Waiting Notification service in cellular communication networks is that it is difficult to efficiently utilize the network resources when the Mobile Subscriber Station roams among various call coverage areas. In particular, when a Mobile Subscriber Station registers with a visited (serving) Mobile Switching Center, the subscriber&#39;s Home Location Register (HLR) transmits information to the serving Mobile Switching Center indicative of the number of messages waiting for retrieval by the subscriber at the Mobile Subscriber Station. The serving Mobile Switching Center uses the forward control (paging) channel to transmit this message waiting data to the Mobile Subscriber Station. The Mobile Subscriber Station acknowledges receipt of the message received on the forward control channel and the presence of the unread message waiting information. The Visited Location Register in the serving Mobile Switching Center is updated to indicate that the Mobile Subscriber Station has been notified about the presence of unread messages.  
         [0007]     When the Mobile Subscriber Station roams to the call coverage area of another Mobile Switching Center and performs either an autonomous registration or a call origination/termination, the new serving Mobile Switching Center accesses the subscriber&#39;s Home Location Register to obtain subscriber information to authorize the provision of service to this subscriber. As part of this process, the subscriber&#39;s Home Location Register again transmits the message waiting information, indicative of the number of messages waiting for retrieval by the subscriber at the Mobile Subscriber Station, to the new serving Mobile Switching Center. The new serving Mobile Switching Center is unaware of the previous message exchange noted above and uses the forward control (paging) channel to again transmit this data to the Mobile Subscriber Station. The Mobile Subscriber Station acknowledges receipt of the message received on the forward control channel and the presence of the unread message waiting information. The Visited Location Register in the new serving Mobile Switching Center is updated to indicate that the Mobile Subscriber Station has been notified about the presence of unread messages.  
         [0008]     This process can continue seriatim as the subscriber roams through various call coverage areas, since each Mobile Switching Center is unaware of the acknowledgement transmitted by the Mobile Subscriber Station to the original Mobile Switching Center and any other previously contacted Mobile Switching Centers. In a highly congested cellular communication network or a cellular communication network with many border cells, the number of forward control channel message transmissions becomes excessive and serves to congest the forward control channel with unnecessary messages. Ultimately, the forward control channel congestion can result in the loss of new call originations and call deliveries.  
       SOLUTION  
       [0009]     The above-described problems are solved and a technical advance achieved by the present system for reducing paging channel occupancy for message waiting indication in mobile switching centers (termed “message waiting indication system” herein). In order to alleviate the traffic on the paging channel, the present message waiting indication system allows the Message Waiting Notification process to determine a last zone in which the Mobile Subscriber was located and only transmit the Message Waiting Indication to the cells within that zone. This eliminates message transmission on the paging channel of cells which are not likely to have the Mobile Subscriber Station residing in their service area. Multiple retries can be attempted and if the last retry is being activated, the paging can be extended to cover all zones in the Mobile Switching Center.  
         [0010]     Many Mobile Switching Centers are divided into paging or registration zones, which are areas where multiple cells are located and which broadcast similar information to the mobile. These zones provide a mechanism to limit a page for an incoming call to a subset of the Mobile Switching Center. The paging/registration zone identification is stored in memory for each of the mobiles and is used for paging messages to alert the Mobile Subscriber Station of the presence of an incoming call. The existing process which updates the HLR and/or the VLR with new message waiting counts broadcasts this information over every paging channel in a Mobile Switching Center to the Mobile Subscriber. The present message waiting indication system used the paging/registration zone data that is stored for each Mobile Subscriber Station in combination with the message waiting count update to reduce the traffic on the paging channel across an entire Mobile Switching Center by directing the message waiting indication messages to only the paging channels where it is most likely to locate the Mobile Subscriber Station.  
         [0011]     The present message waiting indication system is described herein in conjunction with the message waiting indication update feature described in U.S. patent application Ser. No. 10/610,174. However, the present message waiting indication system is not limited to this application and can be used in any cellular communication network configuration; the present description provides a framework to simplify the comprehension of the present message waiting indication system. The above-noted patent application describes a system which comprises a number of processes that execute in the various Mobile Switching Centers of the cellular communication network and functions to use the Inter-System Page (ISPAGE) message to enable the exchange of message waiting indication information between the Home Location Register, the serving Mobile Switching Center and the Mobile Subscriber wireless communication devices served by the Mobile Switching Centers. In particular, the serving Mobile Switching Center, upon receipt of a message waiting acknowledgement from the Mobile Subscriber wireless communication device, updates the local copy of the Subscriber&#39;s data in the Visited Location Register and forwards this information to the Subscriber&#39;s Home Location Register via a message, such as an ANSI-41 Registration Notification Invoke, with the qualification information code being set to NO INFO (or Registration Cancellation return result) and the number of the messages in the message waiting queue being acknowledged. The Home Location Register stores this received data in the Subscriber&#39;s Home Location Register entry for use when the next successive Registration Notification Invoke is received from a new serving Mobile Switching Center or in response to the Subscriber initiating a local access.  
         [0012]     When the serving Mobile Switching Center receives a Registration Notification Invoke message from the Subscriber&#39;s Home Location Register to update the Subscriber&#39;s information and the message waiting indication count is the same as the count previously sent to the Home Location Register, the serving Mobile Switching Center does not have to transmit a message waiting indication over the forward control channel to the Mobile Subscriber wireless communication device, thus reducing the message traffic on the forward control channel.  
         [0013]     When a Mobile Subscriber&#39;s wireless communication device registers with a Mobile Switching Center in the cellular communication network, the Mobile Subscriber may have messages queued in their voice messaging system. When this occurs, the serving Mobile Switching Center provides data to the Mobile Subscriber&#39;s wireless communication device via the radio frequency communication link to indicate the number of messages waiting for the Mobile Subscriber. However, the Mobile Subscriber may not receive this information because in the interim they have roamed into the coverage area of another Mobile Switching Center, where a base station subsystem served by that Mobile Switching Center has the strongest signal. The Mobile Subscriber&#39;s wireless communication device may be locking on to this signal or have already locked on to this signal. There is, therefore, a need to forward the message waiting indication data to Mobile Switching Centers whose service areas overlap with the service area of the Mobile Switching Center presently serving this Mobile Subscriber&#39;s wireless communication device. In this manner, any one of these Mobile Switching Centers can update the Mobile Subscriber with regard to message waiting indications, even though that updating Mobile Switching Center does not presently handle the communication connection with the Mobile Subscriber&#39;s wireless communication device. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0014]      FIG. 1  illustrates in block diagram form the present message waiting indication system and a typical environment in which it operates, including the exchange of messages among the various elements in the cellular communication network;  
         [0015]      FIGS. 2A and 2B  illustrate in flow diagram form the operation of the message waiting notification update system to provide message waiting notification during an initial Mobile Subscriber Station registration;  
         [0016]      FIG. 3A and 3B  illustrate in flow diagram form the operation of the message waiting notification update system to provide subscriber profile updates to the Visited Location Register in the serving Mobile Switching Center;  
         [0017]      FIGS. 4A and 4B  illustrate in flow diagram form the operation of the message waiting notification update system in response to a Registration Cancellation process;  
         [0018]      FIG. 5  illustrates a typical assignment of zones in a Mobile Switching Center for use in paging/registration and delivery of message waiting indication messages; and  
         [0019]      FIGS. 6A and 6B  illustrate in flow diagram form the operation of the present message waiting indication system. 
     
    
     DETAILED DESCRIPTION  
       [0020]      FIG. 1  illustrates in block diagram form the present message waiting indication system and a typical environment in which it operates, including the exchange of messages among the various elements in the cellular communication network. A cellular communication network  100  consists of a plurality of Mobile Switching Centers  101 - 103 , each of which serves one or more base station subsystems (not shown) that provide the radio frequency links to the plurality of Mobile Subscriber Stations  120  that are operational in each call coverage area (termed cell) (not shown) provided by the associated base station subsystem. One Mobile Switching Center  101  is typically termed the Subscriber&#39;s Home Mobile Switching Center and it maintains the subscriber&#39;s identification, authentication, and call services definition data in an associated Home Location Register  111 . Other Mobile Switching Centers  102 ,  103  maintain their own Home Location Registers (not shown) and Visited Location Registers  112 ,  113  to store call authorization data for subscribers who roam out of their home service area to the call coverage area of the visited Mobile Switching Centers  102 ,  103 . Alternatively, the Home Location Register could be a Standalone Home Location Register (SHLR), thus not part of a Mobile Switching Center.  
         [0000]     Initial Roaming Mobile Subscriber Station Registration with Notification  
         [0021]     As illustrated in flow diagram form in  FIG. 2 , in the cellular communication network  100 , when a Mobile Subscriber Station  120  registers with a visited (serving) Mobile Switching Center  102  by transmitting a service request and the MIN/ESN of the Mobile Subscriber Station  120  to the serving Mobile Switching Center  102  via path  1 , the serving Mobile Switching Center  102  must validate the subscriber&#39;s authorization to receive service. This is accomplished at step  201  by transmitting a Registration Notification message to the subscriber&#39;s home Mobile Switching Center  101  over path  2  to retrieve data from the subscriber&#39;s Home Location Register (HLR)  111 . The subscriber&#39;s Home Location Register (HLR)  111  at step  202  determines whether the identified Mobile Subscriber Station  120  is a valid subscriber and if not, returns an Access Deny message to the serving Mobile Switching Center  102  at step  203  via path  3 , the service request from Mobile Subscriber Station  120  is denied, and the process ends at step  204 .  
         [0022]     If the identified Mobile Subscriber Station  120  is a valid subscriber, the Home Location Register (HLR)  111  creates a Registration Notification Return Result message that contains the necessary subscriber service authorization data at step  205  and determines at step  206  whether the subscriber has voice mail service. If the subscriber does not have voice mail service, processing advances to step  207 , as described below. If the subscriber does have voice mail service, at step  208  the Home Location Register  111  retrieves data from its memory indicative of the number of unread messages that are stored in memory for the subscriber and also formats a new MSGS ACK parameter and sets the value to the number of these unread messages that have been previously acknowledged by the Mobile Subscriber Station  120 . For the purpose of this example, assume that new messages have arrived for the subscriber and no notification has previously been transmitted to the Mobile Subscriber Station  120  to alert the subscriber of the presence of these unread messages. Then, at step  207  the Home Location Register  111  inserts this data into the previously generated Registration Notification Return Result message and transmits this message over path  3  to the serving Mobile Switching Center  102  indicative of the number of messages waiting for retrieval by the subscriber at the Mobile Subscriber Station  120 . The serving Mobile Switching Center  102  receives the Registration Notification Return Result message at step  209  and at step  210  creates or updates the Visited Location Register  112  with the subscriber profile data contained in the Registration Notification Return Result message and processes the service request for the Mobile Subscriber Station  120  in well known fashion. At step  211 , the serving Mobile Switching Center  102  compares the message waiting information contained in the Registration Notification Return Result message with the message waiting data stored in the Visited Location Register  112  for this subscriber. Processing ends at step  212  if the number of unread messages and acknowledgements identified by the subscriber&#39;s Home Location Register  111  matches the data stored in the Visited Location Register  112  for the number of unread messages acknowledged by the Mobile Subscriber Station  120 . If the serving Mobile Switching Center  102  determines the presence of unacknowledged unread messages, then at step  213  the serving Mobile Switching Center  102  uses the forward control (paging) channel of the radio link (path  4 ) to the Mobile Subscriber Station  120  to transmit this message waiting data to the Mobile Subscriber Station  120 . The Mobile Subscriber Station  120  at step  214  acknowledges receipt of the message received on the forward control channel via path  5  and the presence of the unread message waiting information.  
         [0023]     If the serving Mobile Switching Center is the subscriber&#39;s home location as determined at step  215 , then at step  216 , the subscriber&#39;s Home Location Register is updated to reflect the new number of unread messages acknowledged and processing ends at step  221 . In the present case, the subscriber is roaming and at step  217  the Visited Location Register  112  in the serving Mobile Switching Center  102  is updated to indicate that the Mobile Subscriber Station  120  has been notified about the presence of unread messages. At step  218 , the serving Mobile Switching Center  102  determines whether the message acknowledgement data should be updated in the subscriber&#39;s Home Location Register  111 . If no update is necessary, processing exits at step  221 . If an update is required, at step  219  the serving Mobile Switching Center  102  generates a Registration Notification Invoke message with the qualification information code contained therein set to NOINFO(0) and containing data indicative of the number of messages acknowledged by the Mobile Subscriber Station  120 . At step  220 , the serving Mobile Switching Center  102  transmits this message over path  6  to the subscriber&#39;s Home Location Register  111  via the subscriber&#39;s home Mobile Switching Center  101 . The serving Mobile Switching Center  102  then terminates processing at step  221 .  
         [0024]     The subscriber&#39;s Home Location Register  111  receives the Registration Notification message at step  222  and at step  223  determines whether the message contains data indicative of the number of unread messages acknowledged by the Mobile Subscriber Station  120 . If this data is not contained in this message, processing exits at step  224 ; otherwise, at step  225 , the subscriber&#39;s Home Location Register  111  updates the subscriber&#39;s profile to reflect the new number of unread messages acknowledged by the Mobile Subscriber Station  120 . The subscriber&#39;s Home Location Register  111  then blocks the Qualification Directive message (as described below) from being transmitted to the serving Mobile Switching Center  102  and processing exits at step  224 .  
         [0025]     Thus, the message waiting notification update system maintains an accurate count of the number of unread messages waiting for a subscriber and the number of unread messages acknowledged by the Mobile Subscriber Station. The serving Mobile Switching Center, upon receipt of a message waiting acknowledgement from the Mobile Subscriber Station, updates the local copy of the subscriber&#39;s data in the Visited Location Register and forwards this information to the subscriber&#39;s Home Location Register where this received data is stored in the subscriber&#39;s Home Location Register entry for use when the next successive Registration Notification is received from a new serving Mobile Switching Center or in response to the subscriber initiating a local access.  
         [0000]     Subsequent Roaming Mobile Subscriber Station Registrations Notification  
         [0026]     In the case where the Mobile Subscriber Station  120  roams to a new Mobile Switching Center  103 , as illustrated by the dotted line in  FIG. 1 , the Mobile Subscriber Station registration process is initiated at the new Mobile Switching Center  103  over path  8  and this becomes the serving Mobile Switching Center  103 . The registration process triggers the registration cancellation process described later. The registration process is implemented as described above over paths  8  and  9  and the unread message and message acknowledgement data from the subscriber&#39;s profile in the Home Location Register  111  is written into a new entry in the Visited Location Register  113 . For the purpose of this description, assume that the subscriber has not read the unread messages described above. If no new messages have arrived for the subscriber since the previous registration, then at step  211  the number of messages previously acknowledged matches the number of unread messages queued for the subscriber and the message waiting notification process exits at step  212 . If new messages have arrived for the subscriber since the previous registration, then at step  214  data indicative of the updated number of unread messages is transmitted to the Mobile Subscriber Station  120  and processing proceeds as described above.  
         [0027]     Thus, the new registration process does not result in use of the forward control (paging) channel of the radio link to the Mobile Subscriber Station  120  to transmit message waiting data indication to the Mobile Subscriber Station  120 , unless a data update is required. The serving Mobile Switching Center does not have to transmit a message waiting notification over the forward control channel to the Mobile Subscriber Station, thereby conserving this resource.  
         [0000]     Qualification Directive Notification  
         [0028]     When the subscriber&#39;s Home Location Register  111  is updated and there is a serving Mobile Switching Center  102  that is providing service to the Mobile Subscriber Station  120 , the updated data written into the subscriber&#39;s Home Location Register  111  is propagated to the Visited Location Register  112 .  FIG. 3  illustrates in flow diagram form the operation of the present message waiting notification update system to provide subscriber profile updates to the Visited Location Register in the serving Mobile Switching Center.  
         [0029]     The process is initiated at step  301  when the subscriber&#39;s Home Location Register  111  updates a subscriber&#39;s profile. This could be either by a subscriber using a feature code to change a feature, personnel changes the subscriber&#39;s data, or an external entity, such as a voice mail system, initiates a change to the subscriber&#39;s data. At step  302 , the subscriber&#39;s Home Location Register  111  determines whether the subscriber is registered at another Mobile Switching Center, for example, the serving Mobile Switching Center  102 . If the subscriber is not registered at another Mobile Switching Center, at step  303 , the subscriber&#39;s home Mobile Switching Center  101  reviews the message waiting information stored in subscriber&#39;s profile in the Home Location Register  111 . If the number of unread messages and acknowledgements identified by the subscriber&#39;s Home Location Register  111  matches, processing ends at step  304 . If the number of unread messages and acknowledgements identified by the subscriber&#39;s Home Location Register  111  fail to match, the subscriber&#39;s home Mobile Switching Center  101  transmits message waiting data to the Mobile Subscriber Station  120  using the forward control (paging) channel of the radio link as described above. The Mobile Subscriber Station  120  acknowledges receipt of the message received on the forward control channel and the presence of the unread message waiting information and processing exits at step  304 .  
         [0030]     If the subscriber is registered at another Mobile Switching Center, for example the serving Mobile Switching Center  102 , then at step  305  the subscriber&#39;s home Mobile Switching Center  101  creates a Qualification Directive message from the data stored in the subscriber&#39;s profile in the subscriber&#39;s Home Location Register  111 . At step  306 , the subscriber&#39;s home Mobile Switching Center  101  determines whether the subscriber has voice mail service. If the subscriber does not have voice mail service, processing advances to step  307 , as described below. If the subscriber does have voice mail service, at step  308  the Home Location Register  111  retrieves data from its memory indicative of the number of unread messages that are stored in memory for the subscriber and also formats a new MSGS ACK parameter and sets the value to the number of these unread messages that have been previously acknowledged by the Mobile Subscriber Station  120 . For the purpose of this example, assume that new messages have arrived for the subscriber and no notification has previously been transmitted to the Mobile Subscriber Station  120  to alert the subscriber of the presence of these unread messages. Furthermore, at step  308  the Home Location Register  111  inserts this data into the previously generated Qualification Directive message and then at step  407  transmits this message to the serving Mobile Switching Center  102  indicative of the number of messages waiting for retrieval by the subscriber at the Mobile Subscriber Station  120 . The serving Mobile Switching Center  102  receives the Qualification Directive message at step  309  and at step  310  determines whether there is a profile data entry for this subscriber. If there is no profile data entry for this subscriber, the serving Mobile Switching Center  102  at step  312  transmits a Qualification Directive Return Error message to the subscriber&#39;s Home Location Register  111  and processing in the serving Mobile Switching Center  102  exits at step  313 . If there is profile data entry for this subscriber, the serving Mobile Switching Center  102  at step  311  transmits an empty Qualification Directive Return Result message to the subscriber&#39;s Home Location Register  111  and at step  314  updates the Visited Location Register  112  with the subscriber&#39;s profile data contained in the Qualification Directive message. At step  315 , the serving Mobile Switching Center  102  compares the message waiting information contained in the Qualification Directive message with the message waiting data stored in the Visited Location Register  112  for this subscriber. Processing ends at step  313  if the number of unread messages and acknowledgements identified by the subscriber&#39;s Home Location Register  111  matches the data stored in the Visited Location Register  112  for the number of unread messages acknowledged by the Mobile Subscriber Station  120 . If the serving Mobile Switching Center  102  determines the presence of unacknowledged unread messages, then at step  316  the serving Mobile Switching Center  102  uses the forward control (paging) channel of the radio link to the Mobile Subscriber Station  120  to transmit this message waiting data to the Mobile Subscriber Station  120 . The Mobile Subscriber Station  120  acknowledges receipt of the message received on the forward control channel and the presence of the unread message waiting information. The processing of this transaction at the serving Mobile Switching Center  102  then exits at step  313 .  
         [0000]     Registration Cancellation  
         [0031]      FIG. 4  illustrates in flow diagram form the operation of the present message waiting notification update system in response to a Registration Cancellation process. In the case where the Mobile Subscriber Station  120  roams from serving Mobile Switching Center  102  to a new Mobile Switching Center  103 , as illustrated by the dotted line in  FIG. 1 , the Mobile Subscriber Station registration process is initiated at the new Mobile Switching Center  103  and this becomes the serving Mobile Switching Center  103 . The registration process is implemented as described above.  
         [0032]     To ensure that there is only one Mobile Switching Center that is presently active as the serving Mobile Switching Center, the subscriber&#39;s Home Location Register  111  cancels the subscriber&#39;s profile entry that was stored in the Visited Location Register  112  in the previous serving Mobile Switching Center  102 . This process is initiated at step  401  when the subscriber&#39;s Home Location Register  111  transmits a Registration Cancellation message to the previous serving Mobile Switching Center  102 , identifying the subscriber as now being active at a new serving Mobile Switching Center  103 . At step  402 , the previous serving Mobile Switching Center  102  determines whether there is a profile data entry for this subscriber. If there is no profile data entry for this subscriber, the previous serving Mobile Switching Center  102  at step  403  transmits an empty Registration Cancellation message to the subscriber&#39;s Home Location Register  111  and processing in the serving Mobile Switching Center  102  exits at step  404 . If there is a profile data entry for this subscriber, the previous serving Mobile Switching Center  102  at step  405  determines whether there is a need to transmit updated data to the subscriber&#39;s Home Location Register (HLR)  111  relating to the number of unread messages acknowledged by the Mobile Subscriber Station  120 . If not, at step  406  the previous serving Mobile Switching Center  102  deletes the profile data entry for this subscriber and processing in the serving Mobile Switching Center  102  exits at step  404 . If there is a need to transmit updated data to the subscriber&#39;s Home Location Register (HLR)  111  relating to the number of unread messages acknowledged by the Mobile Subscriber Station  120 , at step  407  the previous serving Mobile Switching Center  102  formats a Registration Cancellation Return Result message containing data indicative of the number of unread messages acknowledged by the Mobile Subscriber Station  120 . The previous serving Mobile Switching Center  102  at step  408  transmits this message to the subscriber&#39;s Home Location Register  111  via the subscriber&#39;s home Mobile Switching Center  101 , deletes the profile data entry for this subscriber at step  409 , and processing in the serving Mobile Switching Center  102  exits at step  404 .  
         [0033]     The subscriber&#39;s Home Location Register  111  at step  410  receives the Registration Cancellation Return Result message and at step  411  determines whether the message contains data indicative of the number of unread messages acknowledged by the Mobile Subscriber Station  120 . If not, processing advances to step  412  where the subscriber&#39;s Home Location Register  111  processes the Registration Notification Return Result message, as described above at step  207  and shown in  FIG. 2 . If the Registration Cancellation Return Result message contains data indicative of the number of unread messages acknowledged by the Mobile Subscriber Station  120 , at step  414  the subscriber&#39;s profile data in the Home Location Register  111  is updated with the number of unread messages acknowledged by the Mobile Subscriber Station  120 , and at step  415  the Home Location Register  111  formats a Registration Notification Return Result message with the subscriber&#39;s profile data stored in the Home Location Register  111  for this subscriber. At step  416  the Home Location Register  111  inserts data indicative of the number of acknowledgements identified by the previous serving Mobile Switching Center  102  into the previously generated Registration Notification Return Result message and transmits this message to the new serving Mobile Switching Center  103  at step  417 . The processing at the Home Location Register  111  exits at step  413 .  
         [0000]     Message Waiting Indication System  
         [0034]      FIG. 5  illustrates a typical assignment of zones in a Mobile Switching Center for use in paging/registration and delivery of message waiting indication messages, and  FIGS. 6A and 6B  illustrate in flow diagram form the operation of the present message waiting indication system, which serves to reduce the traffic on the paging channel for message waiting indication messages.  
         [0035]     As shown in  FIG. 5 , the Mobile Switching Center  101  serves a plurality of cell sites a-h, each of which has a call coverage area for serving a plurality of Mobile Subscriber Stations, such as Mobile Subscriber Station  120 . As noted above, the Mobile Switching Center  101  is divided into a number of zones (Zones  1 - 3 ) for the purpose of segmenting the service area into a plurality of paging channel service areas. Each Zone includes one or more cell sites and the Mobile Switching Center  101  maintains data in its memory indicative of the zone configuration as well as the presence of Mobile Subscriber Stations in each of the cell sites as well as the corresponding paging zone.  
         [0036]     The message waiting indication process illustrated in  FIGS. 6A &amp; 6B  is implemented in Mobile Switching Center  101  and is initiated at step  601  when the Mobile Switching Center  101  receives a Number of Messages message from an associated Voice Mail System  130  (shown in  FIG. 1 ), which indicates the present count of messages stored in the Voice Mail System  130  for a particular Mobile Subscriber Station  120 . The Mobile Switching Center  101  updates the profile for the Mobile Subscriber Station  120  to reflect this new information and then at step  602  determines whether the Mobile Subscriber Station  120  is registered at the Mobile Switching Center  101  or another Mobile Switching Center  102  (or  103 ). If the Mobile Subscriber Station  120  is registered in Mobile Switching Center  101 , then the Mobile Switching Center  101  at step  603  transmits a Message Waiting Indication message to Mobile Subscriber Station  120  if the present count of waiting messages does not equal the count of the acknowledgements received from the Mobile Subscriber Station  120 . The processing exits if the two counts are equal; otherwise, processing advances to step  614  as described below.  
         [0037]     If at step  602  it is determined that the Mobile Subscriber Station  120  is registered at another Mobile Switching Center, then processing advances to step  604  where the Mobile Switching Center  101  creates a Qualification Directive from the profile data stored for the Mobile Subscriber Station  120 . At step  605  the Mobile Switching Center  101  determines whether the Mobile Subscriber Station  120  has voice mail service, and if not, processing advances to step  606 . If the Mobile Subscriber Station  120  has voice mail service, processing advances to step  607  where a new MSGS ACK parameter is formatted and set to the value of the number of acknowledgements as noted in the profile for the Mobile Subscriber Station  120  as stored in the Home Location register  111 . Processing then advances to step  606  where the Qualification Directive is transmitted to the serving Mobile Switching Center  102  which receives the message at step  608 . At step  609  the serving Mobile Switching Center  102  determines whether there is a profile entry in the Visitor Location Register  112  for the Mobile Subscriber Station  120  and, if not, a Return Error message is generated at step  610  and transmitted to the Home Mobile Switching Center  101 . Processing then exits at step  621 . If a profile entry exists in the Visitor Location Register  112  for the Mobile Subscriber Station  120 , then at step  611  the serving Mobile Switching Center  102  transmits an empty Qualification Directive return result to the Home Mobile Switching Center  101 . At step  612  the serving Mobile Switching Center  102  updates the Visitor Location Register  112  for the Mobile Subscriber Station  120  with the profile data contained in the received Qualification Directive. At step  613  the serving Mobile Switching Center  102  determines if the present count of waiting messages does not equal the count of the acknowledgements received from the Mobile Subscriber Station  120 . The processing exits at step  621  if the two counts are equal; otherwise, processing advances to step  614  as described below.  
         [0038]     At step  614  the serving Mobile Switching Center  102  determines whether the present message waiting indication paging process is a newly initiated process or a retry process. The serving Mobile Switching Center  102  attempts to page the Mobile Subscriber Station  120  a predetermined number of times before terminating the message waiting indication process. If this is a retry process, at step  615  it is determined whether this is the last of the predetermined number of retries and, if so, at step  618  the Message Waiting Indication message is broadcast to all cells served by the serving Mobile Switching Center  102  and then processing exits at step  620 . If the present message waiting indication paging process is a newly initiated process or not the last of the retry processes, then at step  616  it is determined whether a zone-based registration is active. If not, processing advances to step  618  where all cells are paged, as described above. If zone-based registration is active, then at step  617  it is determined whether the provisioned data indicates that only zone-based paging is to be tried and, if not, processing advances to step  618  where all cells are paged, as described above. If zone-based paging is to be tried, then at step  619 , the serving Mobile Switching Center  102  delivers the message waiting indication message only to the cells that are located in the paging/registration zone in which the Mobile Subscriber Station  120  was last located. The paging zone can be implemented as either the paging/registration zone noted above, or can be a mapping table that maintains data indicative of the last cell in which the Mobile Subscriber Station  120  was active. In the latter case, the zone can constitute the last cell in which the Mobile Subscriber Station  120  was active, as well as a number of cells proximate to this cell or within a predetermined distance from this cell. There are numerous ways to manage the population of the zone list and these examples are simply illustrative of the concept. Processing then advances to step  622  where it is determined whether the Mobile Subscriber Station  120  responds to the message waiting indication notification and, if so, processing exits at step  620 . If not, the count of paging retries is updated at step  623  and processing returns to step  614  as described above.  
         [0000]     Summary  
         [0039]     The message waiting notification update system is operable in the serving Mobile Switching Center to maintain an accurate count of the number of unread messages waiting for a subscriber and the number of unread messages acknowledged by the Mobile Subscriber Station. When the serving Mobile Switching Center receives a Registration Notification message return result from the subscriber&#39;s Home Location Register and the message waiting notification count is the same as the count previously sent to the Home Location Register, the serving Mobile Switching Center does not have to transmit a message waiting notification over the forward control channel to the Mobile Subscriber Station.  
         [0040]     Likewise, when a Mobile Subscriber Station returns to the Home MSC service area, if the message waiting notification count is the same as the message waiting acknowledgement count in the HLR record, the Home MSC does not have to transmit the message waiting notification over the forward control (paging) channel to the Mobile Subscriber Station.