Enabler (OMA PoC 1.0). After announcing its PoC 1.0 specifications, OMA held the first interoperability TestFest for OMA PoC 1.0, where six servers and eight cli- The IP Multimedia Subsystem ents deploying OMA PoC 1.0 were tested. Any PoC offerings prior to OMA PoC 1.0 are prestandard. At this time, at least 35 operators are deploying push-to-talk services or trial- ing them. Not all operators deploying push-to-talk are relying on the PoC stan- dard. At least 14 operators are using technology from Kodiak Networks (www. kodiaknetworks.com) that enables push-to-talk via the 2G circuit-switched voice network. A number of handset suppliers are supporting the Kodiak technology. Many in the industry, particularly those who support PoC, feel that the Kodiak technology is threatening the potential market for push-to-talk. QoS is a top priority, particularly as voice, or "talk," is only the first application in the family of push-to-x services. Push-to-talk is destined to be combined with other applications, including presence, picture sharing, and video clips (push-to- view, or streaming video during a PoC session). Although PoC is anticipated to have a strong future, it will not be here for some time. Presence-Based Services Presence-based services are beginning to evolve in the mobile space, although mobile carriers have been slow to offer presence-based services, largely due to con- straints associated with usability and user awareness. The most basic impact of presence services is to allow mobile users to view the availability and communica- tion means of other users. Presence can be a key enabler to stimulate use of ser- vices such as voice, Multimedia Messaging Service (MMS), SMS, instant messaging (IM), push-to-talk, and multiple-player gaming. One of the key advantages of deploying IM is to build on the success of SMS by offering new, more sophisticated messaging services. Presence is expected to get a boost from PoC, as well as from an increasing penetration of mobile phones equipped with Instant Messaging and P