As a new way of meeting in the network era, video conferencing can not be replaced by traditional conferencing with its data and image transmission function.With the increasing requirement of tax system for work efficiency and work quality, the construction of video conference system has become an important part of the modern office construction of tax system.With the expansion of the national tax system network, the bandwidth of the wide-area network has been able to meet the tax system's requirements for the expansion of multimedia services such as video conferencing, distance education and telemedicine.Therefore, it is urgent to build a high quality and high definition video conference system covering the national tax system on the private network of the tax system.The construction of video conference system will promote the exchange between tax systems, greatly improve the working efficiency of tax system, save funds, and have good social and economic benefits.
The total business requirement of tax system video conferencing is: to build a national unified planning video conferencing system.Among them, the first level meeting management center of the General Administration, the second level meeting management center of the provincial tax bureau, the first level meeting center of the general Bureau, the second level meeting center of the provincial level, and the third level sub-meeting center of the prefectural level are established.
The tax video conference system can realize the real-time interaction of audio, video and data between the central meeting place, between each sub-meeting place and the central meeting place, as well as between each sub-meeting place, and can carry out data processing conveniently.IP addresses are configured for video terminals in the central venue and each sub-venue.The MCU may initiate an invitation to each terminal, or each terminal may make an application to the MCU.Video conferencing allows multiple sessions to join the same session at different rates for mixed speed meetings.
The existing tax system network is built based on IP platform, so the video conferencing system will adopt the H.323 standard video conferencing technology based on IP as the protocol platform of the video conferencing system.
According to the demand analysis of the tax video conferencing system and combined with zte's rich design experience in similar projects in the past, on the premise of meeting customers' requirements, the design Suggestions of the tax video conferencing system should follow the following design ideas：
· Principle of progressiveness
Video coding technology adopts the current advanced video compression algorithms h.261, H.263 and H.264 applicable to a variety of bandwidth conditions, achieving high definition picture quality and high fidelity sound quality, while the delay time can be controlled within 300ms, fully ensuring the high quality of video conference.The advanced H.323 protocol platform is adopted in the video communication protocol, which not only meets the bandwidth requirements of wan, but also meets the demand of video service on the network.
· Compatibility principle
By adopting standard H.261, H.263, H.264 and other compression coding standards and H.320/H.323 fully compatible architecture, it can interoperate and control with other video systems well.
· Principle of extensibility
In addition to fully ensuring the high quality and high reliability of traditional video conferencing, this scheme also strives to greatly expand the application scope and content of video conferencing, which fully reflects the trend and direction of networked video applications.In addition to video conferencing, this scheme should also realize monitoring image transmission, distance education, digital video recording, video on demand, video call and other functions.
· High reliability principle
This scheme requires the video conferencing system to run continuously for a long time.The conference terminal and THE MCU also have an automatic recovery chain.During the meeting, if the line problem causes instantaneous break, it can be restored in a very short time without affecting the normal operation of the meeting.The conference terminal and THE MCU are also adaptive.When network congestion occurs, the terminal meeting priority to ensure the audio stream, so as to ensure the continuity of the meeting.
· The manageability principle
The system should have a graphical interface of the video conference management system, which can intuitively and conveniently realize the whole system network management, greatly reducing the maintenance difficulty.The system provides logs to record abnormal information during operation.Administrators and engineers can keep track of device health by querying the run log.In addition, the network management also has alarm management function, the alarms in the running process of the device are immediately reflected in the interface of the network management client to notify the client, and the alarm information is also recorded in the alarm log database for the client to query.Support Chinese interface.
· High safety principle
Video terminals should support access control of system Settings, Web management and other password authentication.In this way, the security of the system is strengthened and the illegal access and operation of the video terminal equipment is effectively prevented.The system should adopt multi-level password management mechanism to make the whole system under multiple security protection, effectively prevent illegal access and operation of all aspects, so that customers can use the video conferencing system more securely.
realization of the plan
The video conferencing system of the State Administration of Taxation was built by ZTE, and the network structure was designed with IP wide area network. The video conferencing system network structure was established on the basis of the existing tax private network, and was divided into three star structures of the General Administration, provincial tax bureau and prefecture-level tax bureau.The system structure is shown in the figure below：
The main equipment selection and configuration of tax video conference system include：
· The multi-point control unit MCU selects ZTE's fully compatible intelligent video server ZXMVC8900
· ZXMVC4050, zte's group video conferencing terminal, was selected as the video conferencing terminal
· ZTE corporation ZXMS80 is selected as the video conference management system
Mapping a product
The main equipment in the video conference system of The State Administration of Taxation includes ZXMVC4050 group video conference terminal of ZTE's video conference system and ZXMVC8900, a fully compatible intelligent video server located in the network center.
1. Group video conferencing terminal -ZXMVC4050 series
Support IP, E1 and ISDN interfaces, and h. 320, H.323 protocols;Performance features are as follows：
· Advanced image processing technology
· Excellent audio processing technology
· Powerful meeting control capability
· Flexible and convenient data capability
· Full Chinese kernel with advanced system architecture
· At the same time support handheld infrared remote control and external PC console control, customers can choose according to different applications
· From power-on to dial-up connection, the actual startup time of the system is very short, which really realizes the startup and ready-to-use
· The terminal supports dual stream function and video stream multicast function
· All kinds of system data will be saved automatically. It will not cause any fault to the system if it is shut down casually or the system unexpectedly loses power. It will be restored to the original state immediately after restarting
· Comprehensive networking ability
ZXMVC4050 provides V.35, BRI, LAN, E1 interface, to meet the various needs of customers networking
· Maintenance and diagnosis
Start - up automatic detection of channel interface type
Support remote software upgrade
Real-time monitoring of channel status
2. Fully compatible intelligent video server -ZXMVC8900
Zte ZXMVC8900 Multi-point Control Unit (MCU) is a fully compatible broadband conference server, fully supporting ITU-T H.323, H.320 protocols, fully compatible access to various dedicated lines, ISDN, IP and even HIGH-DEFINITION conference terminals;The system supports the separation of media and control and can evolve smoothly to the next generation network.Each function module can be flexibly upgraded and expanded.The built-in protocol gateway can access customer terminals through IP, ISDN, DDN, SDH, ATM and other different networks to participate in the video conference.The system features are as follows：
· The hardware structure of the equipment: it adopts telecom rack hardware structure, non-PC structure, special operating system, front contact plugboard, 17 universal slots, supporting online hot plugging, power module, switching of various functional boards, remote monitoring and other functions;Support continuous uninterrupted boot operation;MCU power supply adopts double power thermal redundancy backup.
· Video: It supports ITU-T H.323 and H.320 standards and can complete the access, video exchange and audio mixing capability of H.323 and H.320 video terminals.Support h. 225, H.245, RTP, RTCP, T.120 standard protocols.Supported image codec: H.261, H.263, H.263+, H.264;Supported video formats: QCIF, CIF, 4CIF, SQCIF.Supports all levels of meetings ranging from 64K to 1920kbps (support 384kbps, 768kbps, 1024kbps, 1536kbps, 1920kbps).
· Audio: Support ITU-T's G.711, G.722, G.728 and other audio protocols, through the control terminal can choose to determine the audio codec format.In the same meeting, the function of multi-channel voice mixing can be carried out.Can realize the remote end closed sound, the remote mute.
· Meeting control management: Support the control mode of the meeting, including speech incentive control, chairman control and director control, etc.
· MCU cascade: The system is capable of level 3 and higher level networking and control.
· Multirate blend: The ability to support terminals of different speeds to participate in a conference at the same time (e.g., 384kbps, 512kbps, 768kbps, 1024kbps, 1536kbps, 1920kbps).
· Network management: MCU has perfect remote maintenance capability, remote configuration, dynamic resource configuration, bandwidth management, voice resources and quality management, image resources and quality management, maintenance and monitoring.
· MCU working mode: THE MCU adopts the mode of distributed switching.
After the opening of the state Administration of Taxation video conference system, the operation is stable, and the image and sound quality can fully meet the needs of the daily meeting of the tax system.During the implementation of the scheme, the problems of system stability and reliability, information security, video and audio quality and delay of video conferencing on IP network are mainly solved.The following are detailed below：
1. Stability reliability problem
ZTE MCU ZXMVC8900 and VIDEO terminal ZXMVC4050 adopt the most advanced architecture and design concept in the industry: control unit (MC) and processing unit (MP) are separated;New distributed switching architecture, processing capacity and stable reliability improved, system reliability should reach 99.99%.All hardware modules support hot plugging and software can be upgraded online.The equipment has extremely high stability, no fault in the network and equipment, call success rate reaches 99.9%, drop rate is less than 0.005 times/square/hour, it can ensure the quality of the national tax system video conference.
2. information security issues
The security of the equipment in the video conferencing system is an important factor to ensure the security of the system. Below we will elaborate on the security measures of the equipment in the tax video conferencing system：
· Operating system security
Network management, GK server support in Windows/Unix/Linux operating systems, with good cross-platform, the use of business and media separation technology, very convenient for the system into the NGN next generation system.
· MCU security features
（1） MCU adopts hardware embedded design with high security。
（2） Encryption technology is used.Support external encryption and internal encryption two ways: external encryption, can be connected with a variety of line or business based encryption machine, video conference business can be normal operation through the encryption machine;In terms of internal encryption, MCU supports hardware encryption based on DES algorithm, which is fast and suitable for real-time data flow encryption.
（3） WAN layer: Support firewalls and H.323 agents over THE WAN, so that terminals in different network segments and different H.323 domains can be reasonably secured, and the intrusion of illegal customers can be prevented.
（4） LAN layer: On LAN or in the same network segment, MCU devices are equipped with relevant security protection and authentication functions through the preset mode of IP address, port number, alias and terminal number.
（5） Customer level: Provides three levels of security protection.1. The meeting shall be held with a password, which must be used to enter the meeting;2. Authorized customer name and password are required for meeting control;3. Authorized customer name and password are required for network management and equipment management.
· Video terminal security features
（1） The terminal adopts hardware embedded design with high security.
（2） The password adopts DES encryption algorithm which is widely used in the world.
（3） In the remote login of the terminal, the system will require the logon user to enter the login customer name and password, in order to identify whether the management is a legitimate customer, in order to ensure the security requirements of customers in use.
（4） When logging in locally, the system will require the logon user to enter the login customer name and password to identify whether it is a legitimate customer for management, in order to ensure the security requirements of customers when using.
3. Audio and video quality problems
ZTE video conferencing system USES professional-grade codec chip, supports H.261, H.263, H.264 video coding protocol, provides 720×576 (PAL) /25 frames of high-definition image, the image has CIF, QCIF, 4CIF coding format, completely solve the traditional video conferencing system image resolution is low, weak to the motion image processing capacity.
When the packet loss rate of network is 3%, the subjective assessment of image and sound quality reaches "4" or above.End-to-end delay of video transmission is less than 250ms.When the sound and image are transmitted to the remote venue, the high quality effect of lip sync can be achieved. The error should be imperceptible. The relative delay of audio and video is less than 40ms.
4. Time delay problem
ZTE video conferencing system has a certain ability to resist delay.In the case of network delay, the video conferencing system can hold the meeting continuously and effectively.Within 130ms of network delay, the device (MCU, terminal) configured in this system has a delay of less than 250ms.
After the completion of the state Administration of Taxation video conference system, the scheme has the following main features：
· high compatibility
The system adopts standard H.261, H.263, H.264 and other compression coding standards and H.320/H.323 architecture, which can interoperate and control well with other video systems and ensure the quality requirements of conference service.
· good security
Video terminals should support access control of system Settings, Web management and other password authentication.In this way, the security of the system is strengthened and the illegal access and operation of the video terminal equipment is effectively prevented.Zte MCU ZXMVC8900, VIDEO terminal equipment ZXMVC4050 and ZTE video conference management system ZXMS80 all adopt multi-level password management mechanism, so that the whole system is under multiple security protection, effectively prevent all aspects of illegal access and operation, so that customers can use the video conference system more safely.
· Good scalability
In addition to fully ensuring the high quality and high reliability of traditional video conferencing, this scheme also strives to greatly expand the application scope and content of video conferencing.In addition to video conferencing, this scheme can also realize monitoring image transmission, distance education, digital video recording, video on demand, video calling and other functions.When the system needs to be expanded, the total capacity can be expanded simply by increasing the number of corresponding interface boards.
The video coding technology in this scheme adopts the current advanced video compression algorithms H.261, H.263 and H.264 that can be applied to a variety of bandwidth conditions. It is compatible with the image encoding and decoding technology, which can achieve high definition picture quality and high fidelity sound quality. Meanwhile, the delay time can be controlled within 300ms, fully guaranteeing the high quality of video conference.The advanced H.323 protocol platform is adopted in the video communication protocol, which not only meets the bandwidth requirements of wan, but also meets the demand of video service on the network.
· ease of manageability
The system has a graphical interface of the video conference management system, the system can be intuitive and convenient to realize the whole network management, greatly reducing the maintenance difficulty.The system provides logs to record abnormal information during operation.Administrators and engineers can keep track of device health by querying the run log.In addition, the network management also has alarm management function, the alarms in the running process of the device are immediately reflected in the interface of the network management client to notify the client, and the alarm information is also recorded in the alarm log database for the client to query.Support Chinese interface.
· Industry pertinence
The scheme is systematically optimized for the tax industry. For example, the security of the system is specially customized according to the special requirements of the tax industry, and the system compatibility and expansibility of equipment from other manufacturers may be selected by the tax system in the future are fully considered.It has guiding significance to the construction of video conference network for tax industry and other government and industry customers.
The performance-price ratio of the overall scheme is analyzed: ZTE video conferencing equipment is cost-effective, modular design and embedded operating system are adopted to ensure the security and expansibility of the system, and its good compatibility and expansibility realize real investment protection, providing a guarantee for future upgrade and expansion.