MOBILE VIDEO TELEPHONY

3RD Generation Technology

What is 3G and why 3G?

3G is the third generation development in mobile telephony technology. It succeeded the two earlier technologies.i.e. 1st & 2nd generation.

The International Telecommunication Union (ITU-T) defined the third generation technology to increase the bandwidth (data carrying capacity), support more diverse applications e.g. mobile video telephony, and to facilitate revenue growth for telecom operators.

Mobile Video Telephony?

Mobile video telephony is the mobile visual communication with video sequences and speech transmitted simultaneously over the telecommunication network.

It is a real-time system of the conversational type in which the playback of continuous media such as audio and video occur in an isochronous fashion.

This system involves 3G enabled video telephone and 3G mobile network. 3G enabled telephone comprises of a video camera pointing at the user and a video screen transmitting pictures taken by the other user’s camera. The speech and video content are created in a live fashion from the microphone and camera input. These are encoded in real-time by the mobile devices and transmitted in uplink direction towards the network and the other end user.

Speech and video data in the opposite direction (downlink) is conveyed from the network to source mobile device, which performs data decoding and display/playback of video and speech data.

The mobile network carries conversational multimedia and control traffic in the uplink and downlink directions, allowing real-time communication between the two mobile phone users.

IMPLEMENTATIONTo implement mobile video telephony both CS and PS bearer channel can be used.

The specification for CS mobile video telephony are based on the ITU-T H.324 standard for video telephony terminals over circuit switched channels. The specification for PS mobile video telephony are based on the IETF SIP standard for video telephony over packet-switched channels.

3G-324M is an umbrella protocol that support real time multimedia services over a wireless CS network. The architecture comprises of several sub-protocols that handle error correction, multiplexing and de-multiplexing, encoding and decoding of speech and video.

The speech codec used is Adaptive MultiRate (AMR) that operate at different rate between 4.75kbps and 12.2kbps to provide best speech quality, while the video codec are H.263 and MPEG-4.

Session Initiation Protocol (SIP) in PSThis is an application layer control protocol for creating, modifying, and terminating sessions with one or more participants. It performs the logical bound between the media streams of two video telephony terminals. The protocol stack for PS includes:

Audio & video codec: for speech and video encoding and decoding (AMR,H.263 & MPEG-4). RTP: for real-time media data delivery. RTCP: for QoS monitoring.SDP: for session properties description.UDP/TCP: SIP run on them to perform logical bound between the media streams.IPv4/v6: RTP runs on it for packet sequence number & time stamping.

Benefits of Mobile Video Telephony

1.) It affords the deaf people the opportunity of using sign language to communicate in video call.2.) It aids the delivery of medical services over telecommunication network (tele-medical).3.) It helps in distance learning (tele-educational services).4.) In business live video telephony can be used as a powerful tool to increase efficiency. e.g. monitoring of work in progress on a site of ongoing construction.