Originally, 3G was conceived as an 'all-IP' system by both 3GPP and 3GPP2. But today, it isn't. Experience has shown that the 3G multimedia applications"”those like video teleconferencing that differentiates 3G from 2.5G"”can not effectively operate over an IP network. And until IP networks are upgraded so that they can deliver delay-sensitive applications, 3G service providers have turned to a 'throwback' standard to provide acceptable 3G services: 3G-324M.
Fundamentally, 3G-324M supports real-time streaming of multimedia communications over a time division multiplexing, circuit-switched channel, thereby providing a low-fixed-delay path for the data. In fact, the 3G-324M standard is a derivative of ITU's H.324 standard, which was developed for the PSTN and the V.34 modem protocol.
3G-324M does not use addressing and only comes into play after a mature E.164 addressing method is used by the 3G system to locate the parties and the call is being set up between the two call peers. It also include a number of sub-protocols and technologies to facilitate call control and multimedia channels operation: H.223 for multiplexing and demultiplexing, H.245 for the call control channel, adaptive multi-rate (AMR) and G.723.1 codecs for the voice channel, and H.263 and MPEG-4 simple profile codes for the video channel.
3G services based on 3G-324M started in Japan (FOMA) and are now incorporated into a large number of systems throughout Europe and Asia as well. This month 3 Hong Kong launches the world's first user-self-enabled video conference service, which allows up to four 3 customers to participate in a video conference anytime and from different parts of the world. The underlying video services platform is Radvision's Scopia. It supports the video communications between the 3G H.324M-enabled mobile phones and multiple IP video conferencing end points using the 3G H.324M standard.
Radvision is also one of several companies that provide testing solutions for 3G-324M-based services.
Radvision's Prolab 3G-324M is a comprehensive 3G testing solution. Actually, it's part of Radvision's Prolab Test Management Suite, which provides both 3G-324M and SIP testing. Prolab 3G-324M can be used by 3G handset developers and manufacturers for development and manufacturing test, and it can be used by 3G network equipment vendors and service providers to simulate a wide range of real-world network conditions, monitor the performance of network components, and validate the quality of the multimedia applications running on a network.
As mentioned earlier, 3G-324M includes a number of sub-protocols and technologies. Prolab 3G-324M's architecture is also partitioned along similar lines. Its Call Manager administers established calls on the network. It provides the cohesion between the H.245 control object, the H.223 Multiplexer/Demultiplexer object, and the transport layer.
The H.223 Module is responsible for communication with the bit-stream drivers, whether it be W-CDMA, ISDN, serial, or TCP/IP. Furthermore, the H.223 Module contains the Adaptation Layers for handling error detection according to the traffic content of each of the logical channel (voice, video, data, and call control).
Prolab 3G-324M supports the three Adaptation Layers (AL1, AL2, and AL3), and supports the H.223 Annexes A and B.
Last year Dilithium, another supplier of test solutions, entered into agreement with two distributors to sell their Dilithium Network Analyzer (DNA) into the China market, now that 3G-324M has been adopted by TD-SCDMA as well.
Dilithium claims that DNA was the first 3G-324M protocol analysis tool on the market.
It is designed for diagnosing, analyzing and monitoring all aspects of video telephony calls including call control, connection setup and tear down, and voice and video codec quality. DNA provides both terminal and network monitoring functions.
In terminal mode, DNA can emulate 3G-324M terminals and be used for troubleshooting, protocol analysis, IOT, as well as end-to-end service tuning. In network monitoring mode, DNA can be used to sniff the traffic between two 3G-324M terminals, analyze traffic and decode/play the media.
Tektronix has added troubleshooting support for 3G-324M to its k15 Protocol Analyzer. And by integrating the K15 Version 2.10 with Tektronix's MTS4EA Video Elementary Stream Analyzer, the resulting system provides a video quality analysis test solution.
By tracking video calls, the system is able to calculate H.324M key performance indicators, thereby speeding up troubleshooting activities. The system is also able to extract the H.324M video/audio stream to assess its quality; to look and listen at video calls to assess the customer perceived quality of service; and to extract the video stream in .3gp format for subsequent in-depth off-line video quality analysis.
It will be a few years before IP can truly support 3G video applications. In the meantime, a testable alternative -- 3G-324M -- will provide the mainstay for supporting 3G's video applications.