Conservation of paging resources in a mobile switching center

Abstract

A method in one example comprises the steps of receiving a call intended for a designated cellular subscriber unit at a serving MSC, determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message from a border MSC, and transmitting an initial paging message to the designated cellular subscriber unit via an ISPAGE message directed toward said border MSC.

1 . A method comprising the steps of:
 (a) receiving a call intended for a designated cellular subscriber unit at a serving MSC;   (b) determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message from a border MSC; and   (c) transmitting an initial paging message to the designated cellular subscriber unit via an ISPAGE message directed toward said border MSC.   
   
   
       2 . The method in accordance with  claim 1 , wherein the step (b) of determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message further comprises the step of accessing a database that identifies cellular subscriber units that responded to an ISPAGE message from a border MSC. 
   
   
       3 . The method in accordance with  claim 2 , wherein the database comprises a set of records identifying cellular subscriber units that responded to an ISPAGE message in a border MSC, wherein each record includes identifying indicia for the cellular subscriber unit, and identifying indicia for the MSC in which the cellular subscriber unit last responded. 
   
   
       4 . The method in accordance with  claim 3 , wherein each record further comprises a timestamp indicating date and time of last response. 
   
   
       5 . The method in accordance with  claim 3 , wherein the MSC in which the cellular subscriber unit responded is a border MSC of the serving MSC. 
   
   
       6 . The method in accordance with  claim 4 , wherein records are purged from the database periodically, based, at least in part, upon age of the timestamp indicating date and time of last response. 
   
   
       7 . The method in accordance with  claim 6 , wherein records are purged from the database when the timestamp indicates that the record is more than a provisionable number of days old. 
   
   
       8 . The method in accordance with  claim 7 , wherein the provisionable number of days comprises one day. 
   
   
       9 . A method comprising the steps of:
 (a) receiving a call intended for a designated cellular subscriber unit at a serving MSC;   (b) determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message from a border MSC by accessing a database that identifies cellular subscriber units that responded to an ISPAGE message from a border MSC; and   (c) transmitting an initial paging message to the designated cellular subscriber unit via an ISPAGE message directed toward said border MSC.   
   
   
       10 . The method in accordance with  claim 9 , wherein each record includes identifying indicia for the cellular subscriber unit, and identifying indicia for the MSC in which the cellular subscriber unit last responded. 
   
   
       11 . The method in accordance with  claim 10 , wherein each record further comprises a timestamp indicating date and time of last response. 
   
   
       12 . The method in accordance with  claim 10 , wherein the MSC in which the cellular subscriber unit responded is a border MSC of the serving MSC. 
   
   
       13 . The method in accordance with  claim 11 , wherein records are purged from the database periodically, based, at least in part, upon age of the timestamp indicating date and time of last response. 
   
   
       14 . The method in accordance with  claim 13 , wherein records are purged from the database when the timestamp indicates that the record is more than a provisionable number of days old. 
   
   
       15 . The method in accordance with  claim 14 , wherein the provisionable number of days comprises one day. 
   
   
       16 . An apparatus comprising:
 means for receiving a call intended for a designated cellular subscriber unit at a serving MSC;   means for determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message from a border MSC; and   means for transmitting an initial paging message to the designated cellular subscriber unit via an ISPAGE message directed toward said border MSC.   
   
   
       17 . The apparatus of  claim 16 , wherein the means for determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message further comprises means for accessing a database that identifies cellular subscriber units that responded to an ISPAGE message from a border MSC. 
   
   
       18 . The apparatus of  claim 17 , wherein the database comprises a set of records identifying cellular subscriber units that responded to an ISPAGE message in a border MSC, wherein each record includes identifying indicia for the cellular subscriber unit, and identifying indicia for the MSC in which the cellular subscriber unit last responded. 
   
   
       19 . The apparatus of  claim 18 , wherein each record further comprises a timestamp indicating date and time of last response. 
   
   
       20 . The apparatus of  claim 18 , wherein the MSC in which the cellular subscriber unit responded is a border MSC of the serving MSC. 
   
   
       21 . A method comprising the steps of:
 (a) receiving a call intended for a designated cellular subscriber unit at a serving MSC;   (b) determining that the designated cellular subscriber unit, during a recent prior use of the serving MSC, responded to an Intersystem Page (ISPAGE) message from a border MSC;   (c) determining an availability of a cell-based MSC cluster having as an included cell a last seen cell for the designated subscriber unit; and   (d) transmitting an initial paging message to the designated cellular subscriber unit via an ISPAGE message directed toward said border MSC only if the border MSC is included in the cell-based MSC cluster.   
   
   
       22 . The method of  claim 21  including the further step that, upon a determination that the border MSC is not included in the cell-based MSC cluster, transmitting an initial paging message to a location area associated with the serving MSC. 
   
   
       23 . The method of  claim 21  wherein the cell-based MSC cluster is a Cell specific Location Area Cluster (CLAC). 
   
   
       24 . The method of  claim 23  wherein the CLAC is determined by observing which location areas and border MSCs produce page responses when that cell is the Last Seen Cell of a mobile being called.