In the Next Generation Network (NGN), all networks are speculatively expected to be converged to create a ubiquitous communicating environment that will enable one to avail seamless multimedia communication from any internet connectivity enabled device to another in any network.
In this convergence, gateway is the key element in the network to enable ubiquitous communication. This thesis discusses about the special effort for the design and implementation of a unique PC-to-3G video call gateway for universal multimedia communication along with its supporting soft reduced-SIP (Session Initiation Protocol) client.
In 3G circuit switched network, 3G-324M umbrella protocol stack has been adopted by 3GPP for supporting video conversation. 3G-324M consists of two core components ITU-T H.245 (for call control) and ITU-T H.223 (for packet multiplexing/demultiplexing). Meanwhile, SIP is the commonly used session initiation protocol for multimedia communication in IP network performing similar functions as H.245.
The thesis particularly aims at designing a 3G-IP gateway which is robust and efficient enough to support both IP and 3G technologies and to handle incredibly high call traffic. Although 3G-324M protocol stack is sufficiently efficient enough for handling a single call session, translating H.245 messages into PER binary stream (and vice versa) and performing media packets multiplexing and demultiplexing consume quite a huge amount of system resources if 3G-324M is merged in a gateway environment (for handling many calls concurrently).
These avoidable operations decrease the whole system performance and create a performance bottleneck and also leave rooms for researchers to solve these problems. In order to fulfill the requirements of building a highly robust and efficient gateway and overcoming the mentioned performance bottleneck, some innovative ideas have been proposed and analyzed in the thesis. These ideas are briefly introduced as follow:
- A novel approach uses precompile-store-lookup process based on the nature of H.245 message is proposed for H.245 call control module so as to shorten the call setup time and to reduce the demand of system resources for each call session.
- An efficient direct data dispatching is proposed for H.223 multiplexing/demultiplexing procedure to speed up the message multiplexing and demultiplexing.
- Reduced-SIP is proposed to enable a rapid development of simple SIP-capable communication tools. By integrating the reduced-SIP to the gateway, cross 3G-324M and SIP communication become possible.
The efficient 3G-IP gateway has been successfully designed and tested and is also robust enough to handle ONE Million calls without any problem. It is also experimentally verified that the gateway provides the feature of invariant call setup time (typically 5 to 7s for 3G video call initiation) while the conversation quality and after all the QoS is claimed to be guaranteed. In the meantime, the SIP-based soft client also gives a good interoperability through a series of intensive experimental tests.
It is widely believed that, by launching this system to the market, the revenue of service provider will increase by providing handy, creative multimedia services (e.g. mobile TV, video tour guide, etc.) to end mobile users.
Source: City University of Hong Kong
Author: Tso, Fung Po Posco
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