Information Technology Reference
In-Depth Information
Presently we observe that the mobile networks are in increased demand
for using a packet switching network in order to meet their heavy demand
of internet and multimedia applications. These bulky multimedia contents
have eventually caused a largely growing traffic load over both mobile phone
and internet networks. Moreover, as mentioned earlier, cell phones are now
being used to transmit and receive not only voice but high quality real-time
video and bulky data. From these observations we realized that in the next
generation of networking, 3G and beyond wireless networks, and cross net-
work multimedia service delivery will assume an increasingly important
role. A multimedia gateway that facilitates establishing service sessions and
delivery of multimedia services to users and terminals of differing capa-
bilities is highly recommended. In this case, the supporting gateway must
be giant, robust, and efficient enough for call handling. Otherwise the gate-
way faces not only the loss of QoS, but also a severe hazard of performance
bottleneck.
There have already been some practical developments of gateways that
successfully bridge the gaps among the traditional landline phone, 3G mobile,
and internet networks in order to fulfill many advanced application aspects.
The ITU-T provides the standards H.245, H.223, H.324M, and 3GPP's 3G-324M
standards are the building blocks of an up-to-date multimedia gateway. There
are some commercially available 3G gateways in the market. Radvision has
developed a 3G gateway called Scopia. The Scopia 3G video gateway sup-
ports video telephony as well as video streaming between 3G-324M based
mobile handsets or devices and IP-based video media servers. In the mean-
time, Tandberg and Dilithium have also developed similar gateways.
During this research, we have developed our own 3G-324M- and SIP-based
3G-IP gateway in the City University of Hong Kong. We aim at developing a
gateway that is robust enough to meet the challenge of handling large num-
bers of calls concurrently and at the same time to ensure a good QoS to all
the subscribers. In our research, we have given emphasis on efficient imple-
mentation of the H.245 protocol so as to enhance the efficiency and robust-
ness of the gateway that can smoothly handle high traffic conditions with a
satisfactory level of QoS.
3.4.2 Background
According to ITU-T standards, H.245 is a control channel protocol capable
of conveying information for multimedia communication. In voice and
video telephony as well as in VoIP, this subprotocol (of 3G-324M) is basically
responsible for call initialization, setup, and for continuing the conversa-
tion. This protocol manages information exchange through a set of pre-
defined messages. Some members of this message set are vital for the call
initialization and setup, while some are responsible for continuing the con-
versation. So any attempt to improve the performance of the H.245 procedure
is nothing but handling the message exchange process efficiently. As this
