Method for presence information subscription in a group communications system

Abstract

In a group communications system, a group watcher module subscribes to presentities of interest for a particular group by communicating, to at least one presence server module, a set of subscriptions to a plurality of presentities, wherein each subscription contains a set of event notification criteria for a presentity. When the group watcher module detects a change in presence information for the set of subscriptions, it determines current members of the group and distributes the change in presence information to the current members.

1 .- 17 . (canceled) 
     
     
         18 . A method for providing presence information to a group comprising a plurality of members, the method comprising:
 at a group watcher module:
 communicating, to at least one presence server module, a set of subscriptions to a plurality of presentities, wherein the group watcher module is subscribed to the plurality of presentities by the set of subscriptions and wherein each subscription contains a set of event notification criteria for a presentity; 
 detecting a change in presence information for the set of subscriptions; 
 in response to detecting the change in presence information, retrieving, from a group server, group membership information; 
 determining current members of the group based on the group membership information; and 
 distributing the change in presence information to each of the current members based on the determination of the current members of the group and without receiving, from any of the determined current members, a subscription that identifies one or more of the plurality of presentities. 
   
     
     
         19 . The method of  claim 18 , further comprising the group watcher module modifying the set of subscriptions by one or more of:
 changing the set of event notification criteria for at least one subscription, which causes different presence information to be sent to the members of the group;   adding or removing a presentity from the plurality of presentities, which causes different presence information to be sent to the members of the group; and   adding a subscription to the set of subscriptions or deleting a subscription from the set of subscriptions, which causes different presence information to be sent to the members of the group.   
     
     
         20 . The method of  claim 18 , wherein a sub-set of the plurality of presentities is identified by a Presence Resource List. 
     
     
         21 . The method of  claim 18 , wherein the communicating uses a Session Initiation Protocol (SIP) SUBSCRIBE method. 
     
     
         22 . The method of  claim 18 , wherein the distributing uses a SIP NOTIFY method. 
     
     
         23 . The method of  claim 18 , wherein communicating to at least one presence server module comprises sending the set of subscriptions to a plurality of presence servers wherein each presence server receives a sub-set of the subscriptions. 
     
     
         24 . The method of  claim 18 , wherein the set of subscriptions comprises a first event notification criteria for a first presentity and a second event notification criteria that is different from the first event notification criteria for a second presentity that is different than the first presentity. 
     
     
         25 . The method of  claim 18 , wherein determining the current members of the group comprises retrieving identifiers for the current members from a group server. 
     
     
         26 . The method of  claim 18 , wherein determining the current members of the group comprises:
 storing identifiers for members of the group; and   updating the identifiers for the members of the group upon detecting that a new member is added to the group or an existing member is removed from the group.   
     
     
         26 . The method of  claim 18 , wherein the group watcher module is included in a presence server. 
     
     
         27 . The method of  claim 18 , wherein the group server is a Push-to-Talk server. 
     
     
         28 . A presence server comprising:
 a processing device that is configured to:   receive a set of subscriptions to a plurality of presentities, wherein each subscription contains a set of event notification criteria for a presentity;   detect a change in presence information for the set of subscriptions;   in response to detecting the change in presence information, retrieve, from a group server, group membership information;   determine current members of the group based on the group membership information; and   distribute the change in presence information to each of the current members based on the determination of the current members of the group and without receiving, from any of the determined current members, a subscription that identifies one or more of the plurality of presentities.   
     
     
         29 . The presence server of  claim 28 , wherein the group server is a Push-to-Talk server.