Mobile Video Telephony
The first multimedia services in mobile phone started at 2004 with the introduction of MMS. The multimedia applications are carried out by specific protocols and each protocol has their own specifications. Specific protocols are designed to solve certain problems and provide a new service by combining the existing protocol. The different types of protocol used in mobile multimedia are
• 3G H.324M
• Session Initiation Protocol (SIP)
• Real Time Streaming protocol (RTSP)
• SIP/JSR-180
To enable rich applications such as mobile TV, location-based services, and voice over IP (VoIP), these applications needs to support the end-to-end mobile infrastructure. Reliable and assured transport is essential to achieve the required user experience.
3G H.324 protocol:
The 3G-324M protocol operates over an established circuit switched connection between two communication peers. 3G-324M is an umbrella specification to enable conversational multimedia communication over Circuit Switched (CS) networks. H.324 is a specification for multimedia conferencing over Circuit switched networks and it is a proven solution for conversational multimedia based on 3G mobile Network services. (H324 videophones standard, 2007)
Mobile Video Telephony:
Mobile Video Telephony uses the 3G H.324 and SIP protocol for the audio and video transmission. The two possibilities of offering video telephony in mobile networks are to use circuit switched mobile core network or packet network. The circuit switched networks provides the limited bandwidth to transmit the uncompressed audio and video signal. Though packet switched network provides a larger bandwidth compared to circuit-switched, the immaturity in development affects the reliability of the user. Hence at present H.324 protocol over circuit switched networks provides a good quality of service with a fixed-delay. Packet Switched network with the SIP protocol will definitely rule the mobile video telephony system in future. Until the packet network infrastructure is proven and mature, circuit switched approach is wise to use. (Myers, 2005)
The H.324 uses 33,600 bps modem connection between the callers. This is same type of modem connection used to connect pc-users to the internet. Once the connection is established, an H.324 standard compresses and converts the voice and video into digital signal. The digital signal will be controlled by the H.324 to fit into the corresponding screen and bandwidth. The voice will be compressed to 6,000 bps and video is also compressed and uses the rest of the bandwidth.
Reference:
(2007). H324 videophones standard. Retrieved November 24, 2007, from Elextronika Web site: http://www.elextronika.com/tvphone/h324.htm
Myers, David (2005). Mobile Video Telephony. Retrieved November 24, 2007, from mobile computing Web site: http://searchmobilecomputing.techtarget.com/searchMobileComputing/downloads/Mobile_Video_Telephony_Ch01.pdf