agreed to a revision of a Recommendation that experts say is an important step
towards solving the problem of lengthy call setups in 3G video telephony. Seen
as a key issue to address, the resolution of this issue may help accelerate the
market for 3G.
According to SG 16 sources the standard has been successfully tested in
products and many mobile operators and handset manufacturers have started
The revised ITU-T Recommendation H.324 speeds the initiation of 3G video
sessions through the streamlining of the call set-up signalling that is
necessary to establish the connection between two handsets and between a
handset and a media server.
Previously setting up a typical video session required each end to send up to
ten messages to the other terminal, each time waiting for a message to be
received and acknowledged before sending the next one. And, if a message was
not received, the sending device had to wait and finally time out before
retransmitting. The delay introduced in this process led to long video call
The new method eliminates the message queuing and time out issues. Now, all
signalling is sent as a single batch to be processed by the receiving device.
Missed messages, due for example to network errors, are immediately detected by
the receiving device and retransmission requests are spontaneously generated.
This leads to much quicker call setup times, bringing video connectivity close
to the same level of service as traditional telephony.
Key for many operators is that implementation will not require manufacturers to
recall phones, also meaning that services may work on existing devices. Other
advantages of the new approach include the fact that it is protocol and network
independent, enabling connectivity with any other device, even if it is
IP-based (e.g. IP video streaming server or a PC-based video terminal) and
meaning that it does not interact with underlying network protocols or codecs,
enabling devices using the standard to operate even when roaming in other