3G Powered 3G-324M Protocol

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1 3G Powered 3G-324M Protocol

2 NOTICE 2002 RADVISION Ltd. All intellectual property rights in this publication are owned by RADVISION Ltd. and are protected by United States copyright laws, other applicable copyright laws and international treaty provisions. RADVISION Ltd. retains all rights not expressly granted. No part of this publication may be reproduced in any form whatsoever or used to make any derivative work without prior written approval by RADVISION Ltd. No representation of warranties for fitness for any purpose other than what is specifically mentioned in this guide is made either by RADVISION Ltd. or its agents. RADVISION Ltd. reserves the right to revise this publication and make changes without obligation to notify any person of such revisions or changes. RADVISION Ltd. may make improvements or changes in the product(s) and/or the program(s) described in this documentation at any time. If there is any software on removable media described in this publication, it is furnished under a license agreement included with the product as a separate document. If you are unable to locate a copy, please contact RADVISION Ltd. and a copy will be provided to you. Unless otherwise indicated, RADVISION registered trademarks are registered in the United States and other territories. All registered trademarks recognized. For further information contact RADVISION or your local distributor or reseller. 3G-324M Protocol version 1.0, August, 2002 Publication 1

3 CONTENTS Vision of 3G 1 Scope of 3G-324M 1 3G-324M Enabled Services 2 3G-324M Market Drivers 2 Potential Products 3 Technology Concepts 3 3G-324M Architecture 5 H.324 The Base Protocol 5 H.223 The Multiplex Protocol 6 H.245 The Control Protocol 8 RADVISION 3G-324M Toolkit 9 3G-324M Toolkit Architecture 9 Software Modules 10 Toolkit Modules 10 User Applications 11 3G-324M Toolkit API 11 Contents iii

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5 3G POWERED 3G-H.324M PROTOCOL VISION OF 3G SCOPE OF 3G- 324M 3G technologies offer an endless suite of services that will greatly expand the horizon of communication capabilities. Video-conferencing in a taxi, watching clips from your favorite soap opera in a train, multimedia dating, sharing your vacation experience in multimedia fashion, or playing multimedia games with friends virtually anywhere all from the palm of your hand are just few examples. Many commodity and non-commodity products, such as cellular voice phones, radios, televisions, music players, voice recorders, GPS devices, digital cameras, video cameras, personal computers, internet devices, data storage and more will be included in one handheld, tiny box called a 3G Cell Phone. 3G cell phones will have high quality color displays and camera attachments, built-in MP3 music, video, and JPEG still picture players, and mini hard drives with gigabyte capacities. In short, the future will bring many more features, better quality, faster DSL-like communication speeds, and lighter weights. Convenient and affordable, these phones have the potential to initiate a huge market for many years to come. There are two 3G standardization organizations: 3rd Generation Partnership Project (3GPP) supporting UMTS technology with WCDMA 3G Air interface. 3rd Generation Partnership Project 2 (3GPP2) supporting CDMA2000 technology. Both bodies have defined 3G-324M as a solution for conversational communication over Circuit Switched (CS) networks. CS networks are heavily deployed by carriers, mature, well managed, and smoothly operated. Enabling 3G conversational services over existing infrastructures of circuit switched networks was a standardization challenge met by the 3GPP group. As the result of this standardization effort, the 3GPP defined 3G-324M to enable multimedia communication services. 3G-324M operations are divided into two major phases call setup using the 3G Air interface (3G TS ) and operations occurring when the call is established (3G TS ). The 3GPP TS working group defined the call setup procedure for WCDMA. The TS G Powered 3G-H.324M Protocol 1

6 3G-324M Enabled Services working group reused ITU-T H.324M for multimedia conferencing over CS networks and added voice and video codecs with mandatory requirements for bit-error handling defined in optional ITU-T H.223 annexes. For 3G CDMA2000 based networks, 3GPP2 added optional compatibility requirement to 3G-324M systems (3GPP2 S.R0022, Version 1.0, July 10, 2000). 3G-324M ENABLED SERVICES 3G-324M MARKET DRIVERS VoIP defined new levels of communication services. 3G-324M enables these services using the current CS infrastructure to become a reality. The following are examples of such services: Video Conferencing Point-to-point or multipoint sessions between mobiles or with office video conferencing systems. Video streaming Cell phone TV with multiple live TV channels, video-on-demand for content such as news and movies. Multi-Media Multi party gaming playing in real time with other remote users. 3G-324M enables 3G conversational services by gluing a new, proven technology with an existing, well-deployed legacy technology. All other common IP services, such as web browsing and , are enabled by reusing the cell phone as a modem to connect with an ISP, similar to the method used with 2G cell phones today. From the users point of view, a new adventure world of conversational services is becoming available with the 3G-324M. The cost and risk of replacing a whole infrastructure with new equipment is almost impossible for most Service Providers and raises a risk of operation maturity and return on investment. Hence, a minimal investment model for new, attractive and differentiated services now appears much more appealing. When reusing the CS network, the following is achieved with no risk to existing infrastructures: Addressing is well defined (reusing the phone E.164 numbering scheme) Subscriber authentication is well defined and operational Fixed acceptable latency Successful management (authentication, authorization, accounting, monitoring, redundancy, recovery, billing) Robustness and five 9 s service availability grade Scalability nationwide operational infrastructure operates well 2 3G Powered 3G-H.324M Protocol

7 Potential Products POTENTIAL PRODUCTS The following are three 3G-324M technology-based product types: 3G-324M HANDHELD AND PDA DEVICES Wireless 3G handheld and PDA devices are expected to be a mass-market product. They are developed over chipsets to enable a low price solution and can be integrated with other software toolkits. 3G handheld devices are expected to integrate several protocols and technologies to maximize the handheld value in the eyes of the consumers. 3G-324M GATEWAYS AND MEDIA SERVERS 3G-324M gateways provide the interworking between 3G-324M mobile devices and other VoIP or PSTN terminals. The type of gateways will be carrier class, since they are required for handling the high loads of call sessions of the wireless handheld devices. The carrier class gateway may use H.248 for media processing decomposition and H (H.323/SIP and 3G-324M interworking). Such a gateway should provide connectivity between a 3G handset and an IP LAN/WAN or ISDN terminal and content servers. When operating also as a media server, the gateway might allow 3G services, such as on-line web meeting. The gateway should enable conversational communication including voice, video and data between VoIP and 3G-324M terminals according to the 3GPP standard. VIDEO STREAMING SERVERS Video streaming for services, such as video-on-demand and cell phone TV, are important differentiators for the 3G services suite. The streaming server should be a running scalable streaming video solution. Today web-based services are well known for providing news, movie promotions and other entertainment services. TECHNOLOGY CONCEPTS 3G-324M makes an interesting technology mix. Call signaling and addressing is done in the TDM-based method that has proved itself for decades. The legacy addressing methods (phone numbers) are reused, while the service management (provisioning, monitoring, accounting, redundancy and recovery) remains as is. However in addition to this, after establishing a call, a bit stream channel is carried between the call participants. On this bit stream the new Call Control (H.245) IP technology and multimedia streams can reliably operate. A 3G-324M enabled phone consists of 4 parts: 3G Powered 3G-H.324M Protocol 3

8 Technology Concepts Modem or other bit-stream generator this part is an embedded software/hardware that allows the connection between two different phones. Signaling Channel this channel is used for the exchange of capabilities and opening of video, audio and data channels between two different phones. The signaling channel is defined by the H.245 Protocol. See H.245 Module on page 10. Data this is the audio and video codecs and other data channels. These channels are actually what the phone users see or hear. They are also encapsulated in various standards (such as the widely-known MPEG-4). Most of these solutions include software and hardware. Multiplexer this software unit multiplexes and de-multiplexes the signaling and data channels together to send and receive them through the modem. The multiplexer is defined by the H.223 Protocol. See H.223 Module on page G Powered 3G-H.324M Protocol

9 Technology Concepts 3G-324M ARCHITECTURE Figure 2-1 illustrates the architecture of the 3G-324M Protocol. Out Band Scope of 3G TS Call Control NW Interface In Band Scope of 3G TS Video I/O Video Coding H.263 MPEG-4 Video Coding Voice I/O Voice Coding AMR Multimedia Multiplexing/ Demultiplexing H.223 Annex B NW Interface Third Generation Mobile Communications Network System Control Control Protocol H.245 CCSRL NSRP Standard Coverage Figure 2-1 3G-324M Components Each protocol component is described below. H.324 THE BASE PROTOCOL H.324 terminals can carry real-time voice, video and data (or any combination of the three), including videotelephony. H.324 terminals can be integrated into personal computers or implemented in stand-alone devices such as videophones. Other recommendations in the H.324-Series include H.223 Multiplex and H.245 Call Control. 3G-324M makes use of the logical channel signaling procedures of Recommendation H.245, in which the content of each logical channel is described when the channel is opened. Procedures are provided for the expression of receiver and transmitter capabilities, so that transmissions are limited to what receivers can decode, and so that receivers may request a 3G Powered 3G-H.324M Protocol 5

10 Technology Concepts particular desired mode from transmitters. H.324 terminals can be used in multipoint configurations through MCUs, and can interwork with H.320 terminals on the ISDN, as well as with terminals on wireless networks and various VoIP protocols, such as H.323 and SIP. ANNEX A ANNEX C H.223 THE MULTIPLEX PROTOCOL H.324 uses H.245 as the control protocol, as mentioned above. This protocol requires a reliable link layer for operation. Annex A defines two ways for reliable transmission of the MultimediaSystemControl PDU one is by Simple Retransmission Protocol (SRP), which is mandatory. (Annex C later changes this definition and requires the use of NSRP.) The second is LAPM/V.42, which is optional. The key difference between these two methods is that in SRP, after sending an SRP command, a response must arrive before the next command can be sent. In LAPM/V.42, on the other hand, multiple commands can be sent before receiving any responses. Annex C defines an extension for applications to work in error-prone networks, and is referred to as H.324M. Four different H.223 Multiplexer levels are defined offering increasing robustness, but increasing complexity and overhead. Annex C also defines the procedure for level setup and for dynamic change between levels during a session. Annex C provides Control Channel Segmentation and Reassembly Layer (CCSRL) for the transmission of the control channel (H.245) and defines mandatory use of Numbered SRP Response Frames (NSRP). The H.223 Protocol consists of the Multiplex/Demultiplex layer and the Adaption layer. The Multiplex/Demultiplex layer multiplexes the logical channels and the control channel into a single bit-stream that can be sent over the physical layer. The multiplex layer does not perform any error control on the logical and control channels. The Adaption layer handles error detection according to the traffic content of each logical channel. The three formats of the adaptation layer are: AL1 used by the H.245 control channel and data channels AL2 used by audio/video channels AL3 used by video channels The control channel requires a reliable link, which is provided by the Simple Retransmit Protocol (SRP), Numbered SRP (NSRP), or Link Access Procedure for Modems (LAPM). The H.223 Protocol specifies a packet-oriented multiplexing protocol for low bit rate multimedia communication. This protocol can be used between two low bit rate multimedia terminals, or between a low bit rate multimedia terminal and a multipoint control unit or an interworking 6 3G Powered 3G-H.324M Protocol

11 Technology Concepts adapter. H.223 allows the transfer of any combination of digital voice/audio, digital video/image and data information over a single communication link. This protocol provides low delay and low overhead by using segmentation and reassembly, and by combining information from different logical channels in a single packet. ANNEX A ANNEX B Annex A specifies the protocol that handles the light bit error prone channel (Level 1) of the mobile H.223 extensions, as described in Annex C of H.324. The Annex modifies the MUX-PDU framing scheme, leaving the H.223 adaptation layer unchanged. In the basic mode, which is mandatory in Level 1, a MUX-PDU should be delimited by a 16 bit flag. In addition, this Annex also defines an optional double flag mode in which the MUX-PDU should be delimited by two consecutive 16-bit flags. Annex B specifies the protocol that handles the medium bit error prone channel (Level 2) of the mobile H.223 extensions, as described in Annex C of H.324. Annex B modifies the MUX-PDU framing scheme, leaving the H.223 adaptation layer unchanged. Annex B defines the usage of the basic mode of Annex A, but requires that the double flag of Annex A will not be used. Instead it defines a different stuffing scheme in case the transmitter has nothing to send. The MUX-PDU format includes a 3 Octet header and 0-n information fields. Figure 2-2 illustrates an H.223 Annex B multiplexing frame. Multiplexing information, Frame length information Synchronization flag Header information Optional field Payload Proposal: Extracting multiplexing information from the immediately preceding frame header Figure 2-2 Annex B Multiplexing Frame 3G Powered 3G-H.324M Protocol 7

12 H.245 The Control Protocol ANNEX C ANNEX D Annex C specifies the Level 3 Protocol of the mobile H.223 extensions as described in Annex C of H.324. Annex C deals with multimedia telephone terminals over highly error-prone channels. This Annex changes both the multiplex layer and the adaptation layer of Recommendation H.223. These adaptation layers defined in Annex C include options for the following: Error detection and correction Sequence numbering Automatic repeat request Retransmission capabilities (hybrid ARQ-type I & II) Segmentation procedure for transmitting frames that are transmitted unframed H.223 Annex D defines an operation mode for 3G-324M on ISDN circuits, at bit rates ranging from 56 kbit/s to1920 kbit/s. In Annex D, an optional Level 3 Protocol of the H.223 mobile extensions is specified. In order to maintain compatibility, the basic features of the Level 3 Protocol described in H.223 Annex C are included. H.245 THE CONTROL PROTOCOL The H.245 Recommendation specifies the Call Control Protocol. The H.245 channel is used by endpoints for exchanging audio and video capabilities and for performing master/slave determination. H.245 is also used to signal the opening and closing of logical channels, and for sending the Multiplex Table of each party. The H.245 channel remains open during the call to carry various control messages. H.245 messages are encoded in ASN.1 using PER. The messages are grouped into three categories Capability, Channel Management and Channel Operations. The Capability messages describe the multimedia capability of the endpoints and determine their master/slave relationship. The Channel Management messages manage the local channels between endpoints and the Channel Operations messages use the logical channel number to specify the channel on which the operation takes place. 8 3G Powered 3G-H.324M Protocol

13 RADVISION 3G-324M Toolkit Each of the above categories has four types of messages Request, Response, Command and Indication. A Request message results in an action and a response from the remote endpoint. A Command message results in an action with no response from the remote endpoint. An Indication message does not result in an action or a response from the remote endpoint. RADVISION 3G-324M TOOLKIT 3G-324M TOOLKIT ARCHITECTURE The RADVISION 3G-324M Protocol Toolkit is a set of software development tools intended for the development of 3G-324M-capable software and hardware. The 3G-324M Protocol Toolkit provides 3G-324M services for opening the H.245 control channel and media channels including H.223 and H.324-related Annexes. The Toolkit is compliant with 3GPP TS Figure 2-3 illustrates the RADVISION 3G-324M Toolkit Architecture. Application H.245v7 CCSRL NSRP CM Call Manager Codecs, AMR, MPEG4,... H.223 Control Error Handling H.223/Annex A & B Adaption Layers MUX DEMUX Transport (Driver Adaptor) 3G Air Interface Drive (such as WCDMA) Figure 2-3 3G-324M Toolkit Architecture 3G Powered 3G-H.324M Protocol 9

14 Software Modules SOFTWARE MODULES TOOLKIT MODULES CALL MANAGER This section provides a high-level description of the functions that each module performs, the interface of each module to the other modules, and the data and control flow of the system. Following is a description of the Toolkit modules. The Call Manager is responsible for the creation and destruction of calls. The Call Manager is actually the glue between the H.245 Control object of the call and the H.223 Multiplexer/Demultiplexer object of the call. The Call Manager provides access to H.245 operations of the Toolkit, including creation and deletions of channels. The channels in this module contain their H.223 information for the H.223 multiplexer. H.245 MODULE The H.245 Module is responsible for performing the H.245 procedure and for opening and closing the logical channels. The Capabilities Exchange and Master/Slave Determination procedures are the first to be performed during the H.245 control process. The Toolkit sends the capabilities in one of two modes automatic or manual. The mode of operation is determined in the configuration of the Toolkit. The Master/Slave determination procedure is as follows: 1. The Toolkit sends two parameters to the remote entity the terminal type and a random number. 2. The Toolkit receives the two parameters of the remote entity. 3. The master/slave status is determined by comparing these parameters (as defined in the H.245 Standard). 4. The application is notified of the results by using the callback function, cmevcallmasterslavestatus(). As with the capability exchange procedure, the master/slave determination procedure can be either automatic or manual. Similarly, the choice is determined in the configuration of the Toolkit. After both Capability Exchange and Master/Slave Determination are completed, the user may start sending and receiving open logical channel messages using the APIs and callback functions of the Toolkit. Following the completion of this procedure, the user will request the Toolkit to send it s Multiplex Table and the Toolkit will receive the Multiplex Table of the remote party. H.223 MODULE The H.223 Multiplexer/Demultiplexer module is responsible for communication with the modem. This module replaces the TCP/IP interface used in VoIP protocols. 10 3G Powered 3G-H.324M Protocol

15 3G-324M Toolkit API The H.223 module has two sets of interfaces: APIs for the various channels (H.245 and codecs). APIs for the modem interface. USER APPLICATIONS USER APPLICATION AUDIO/VIDEO CODECS BIT STREAM DRIVER INTERFACE Following are modules that are out of scope of the Toolkit and should be provided by application developers. The user application uses the Call Manager of the Toolkit to open calls and deal with video and audio channels. The user application is also responsible for dealing with the actual codecs that will be used in the call. Codecs are out of the scope of the Toolkit. Application developers can choose their preferable codecs in accordance with 3GPP TS Since the handling of bit stream drivers is different between various operating systems and hardware interfaces, and since using a bit stream driver requires the development of operating system drivers in most cases, a bit stream driver interface (such as an Air interface or a modem) is not supplied in the Toolkit. Application developers should provide a bit stream driver that can interface with the H.223 module. An example of a basic driver is supplied as part of the Test Application that is provided with the Toolkit. 3G-324M TOOLKIT API The 3G-324M Toolkit is made up of the following API groups: Call API The Call API is responsible for the construction and destruction of calls. This API is responsible for opening an H.223 object and linking it with an H.245 object. It also provides automatic capabilities and master/slave exchange, and handles the opening and closing logical channels. H.245 API The H.245 API is responsible for the management of H.245 messages and the opening of logical channels. It provides manual operations on these types of objects. Configuration API The Configuration API is responsible for holding the configuration information. This module includes two configuration sub-trees: 3G324mConfiguration H245Configuration 3G Powered 3G-H.324M Protocol 11

16 3G-324M Toolkit API PVT/PST API The PVT/PST API is responsible for the manipulation of PVT trees. The PVT database is used to hold ASN.1 messages, which is the way the H.245 messages are defined. For more information, see the RADVISION documentation. 12 3G Powered 3G-H.324M Protocol