sing IMS are highlighted in this section. Additionally, a number of vendors and applications developers are adopting IMS Application Development Programs to develop compatible services and applications that can work with their IMS solutions: Push to Talk over Cellular (PoC): PoC enables real-time one to one and one-to-many voice service in any cellular network. PoC offers the benefits of two-way radio across different parts of the world. For operators, PoC is a service that has a high appeal to both businesses and consumers. OMA has standardized PoC but currently several operators are using pre-standard versions of push-to-talk. Push- to-X experience extends the evolution of PoC to add unique applications like email. Using IMS, the Push-to-X can be connected to any IP based fixed or mobile access network. Messaging: Instant Messaging is a form of real-time communications between two or more people based on typed text. IM has been enhanced in IMS SO that messages can be associated with existing sessions. IM server can be summed into an IMS Unified Messaging system which can further include SMS, voice mail, and SO on, servers. IMS enhances voice mail service by incorporating features like personalized greetings, message forwarding and more. It enables operators to offer a more customized experience for each user. Voice over IP (VoIP): IMS will enhance VoIP service by making it access independent and providing seamless mobility. IMS allows VoIP systems to interface with the PSTN and existing cellular systems. Next Generation Mobile Communications Ecosystem Presence: Presence application allows users to know when others are willing or able to communicate, as well as where and with which media type they prefer to be in touch. Just by looking up a contact's name in the handset directory a user can quickly see if the contact is available for a voice call or text message. The presence solution can be easily integrated with other services such as VoIP, PoC, Instant Messaging, and SO on. Presence provides subscribers with 