Common Access Network Methods in video conferencing

There are still many ways to learn about the access network. Here we mainly introduce the main access network methods of video conferencing. Most users are most concerned about Video Conferencing Systems in the following aspects: audio and video quality, system price, system security, and scalability. This article compares the problems raised by the above users from the perspectives of access network methods, software and hardware solutions of applications, and other video conferencing products on the market.

It provides some reference for users to build an efficient, flexible, and easy-to-use video conferencing system based on their actual needs. There are two common network environments: one is a circuit switching network, such as ISDN, DDN, and PSTN. Another type is packet-switched networks, such as ATM, IP, and frame relay.

1. Access through ISDN lines

For most individual users and small enterprise users, using ISDN line access is a more economical and practical choice. ISDN (Integrated Service Digital Network) provides end-to-end Digital Channel connections to users using public telephone networks to carry various telecom services including voice and non-voice. A conference TV is transmitted over an ISDN channel at a rate of 384kb/s to 2 Mb/s. Because ISDN is billed Based on the used B channel (64 KB/s), and the domestic communication rate of channel 1B is equivalent to the ordinary telephone communication rate (based on the most widely used circuit switching mode ),

For users with less traffic and shorter communication time, the cost of using ISDN is much lower than that of renting a ddnleased line or frame relay circuit. It also features high speed, low investment, and convenient networking, meeting the application requirements of basic conference and television systems. However, the national ISDN network is still in the upgrading phase, and the reliability and stability are insufficient compared with the leased line.

2. Rent a ddnleased Line System

Large enterprises and institutions usually have high requirements on video effects. In this case, you can select the access method of the ddnleased line. DDN is a data transmission network that uses digital channels to transmit data signals. It is mainly used to provide users with digital data transmission channels with permanent and semi-permanent connections, which can be used for communication between computers, it can also be used to transmit digital fax, digital voice, digital image signals, or other digital signals. The ddnleased line features high transmission quality, low network latency, high circuit reliability, high network security, and convenient networking. Although DDN has the above advantages, because the digital circuit provided by DDN is semi-permanent connection, no matter whether the user transmits data, this connection remains, so the cost is relatively high, it is not suitable for users with short communication time, but only for long-time point-to-point and multi-point communication connections, because the ddnleased line charges fees based on the number of point-to-point connections. If some subordinate departments of a group user are connected to the company's headquarters, you can use a multi-point-to-point ddnleased line network. However, if the subordinate departments also need to communicate with each other, if point-to-point connections are adopted, the various departments of the company constitute a mesh network, so that the user cost is too high.

3. PSTN system

For ordinary personal users, if you want to try the video conferencing experience, you can try PSTN access. PSTN Public Telephone Network is currently the most widely used network system. It has the advantages of wide coverage, ease of use, low price, and easy networking. However, the network speed is only 56 kbps, the line quality is poor, and the transmission rate is low. Sound Image Transmission for video conferencing is far from enough. software-based video conferencing systems can achieve image transfer rates of 4f/s. The biggest drawback is that the image quality is too poor, this will greatly affect the quality of the Meeting, which is rarely used.

4. Use an ATM Network

If you want to achieve a good video effect and access the ATM network is convenient, the access method of the ATM network is also an option. ATM is an asynchronous transmission mode. It combines the advantages of circuit switching and group switching. It can transmit broadband signals at any rate and transmit voice, data, images, and video services. The biggest feature of this technology is QoS Assurance. We recommend this solution for organizations with high quality requirements due to line conditions. This solution features good image quality, convenient networking (no need to connect all the video conferencing terminal lines to the MCU), high reliability. However, the cost of the device is high and an ATM network is required for access.

5. Video Conferencing System Based on IP Network

The most simple access method is the IP network. IP-based networks adopt the group switching technology. Because group switching does not guarantee ordering and fixed latency, it cannot guarantee a fixed delay and bandwidth. UDP/IP, RTP, RTCP, And RSVP protocols are used to better solve the service quality of real-time communication. Video conferencing systems applied on Broadband IP networks such as ADSL, FTTB, and LAN have achieved good results. As IP networks are everywhere today, this method is easy to build and cheaper. However, the IP address based on Packet Switching follows the best delivery principle. Therefore, the video conferencing effect of this access network mode is inferior to that of leased lines such as ISDN and DDN. However, its cost-effectiveness is favored by more and more users, especially for small and medium-sized enterprises and individuals with sufficient network bandwidth.

6. systems connected by satellites

Satellite Networks have incomparable performance advantages in the area of remote video conferencing. They can cover remote areas such as the sea and mountains, with high transmission rate and high security, moreover, Venue Construction and relocation are flexible and convenient, making it a good choice for multinational companies. The "satellite broadband video conferencing system" supports the integrated transmission and broadcasting of multi-channel Conference videos, files and data. The disadvantage of this scheme is that it is expensive. Except for the satellite channel fee, the construction cost of each satellite ground station is about 0.2 million yuan. At the same time, satellite communication has a high latency and is not suitable for video conferencing systems with high real-time requirements.

7. Frame Relay Mode

The frame relay access network is also a professional conference access network. Frame transfer technology is mainly used to transmit data services. frame transfer is suitable for encapsulating LAN data units and sending burst services. It is a way of Wan communication. This type of network is highly efficient, with high network throughput and low communication latency. The access rate of Frame Relay users ranges from 64 kbit/s to 2 Mbit/s, and can even reach 34 Mbit/s. The network cost based on frame relay is high, but the video effect is good.