Access Network Method Comparison in video conferencing

There are still many access networks in the video conference. Here we will introduce common access methods in section 7, including using ISDN lines, renting ddnleased lines, and using PSTN systems. Most users are most concerned about Video Conferencing Systems in the following aspects: audio and video quality, system price, system security, and scalability. 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.

Using ISDN lines
For most individual users and small enterprise users, using the ISDN line access network is a more economical and practical choice. ISDN uses the public telephone network to provide end-to-end Digital Channel connections for various telecommunication services, including voice and non-voice. Using an ISDN line, a conference TV can be transmitted over an ISDN channel at a rate of KB/s to 2 Mb/s. Because ISDN is billed Based on the used channel B (64 KB/s), the domestic communication rate of channel 1B is equivalent to the general 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.

Ddnleased line
Large enterprises and institutions usually have high requirements on video effects. In this case, you can select the access method of the ddnleased line. 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 a point-to-point connection is adopted, the various departments of the company constitute a mesh network, so that the user cost is too high.

Systems Using PSTN
For ordinary personal users, if you want to try a video conference, you can try the PSTN access network method. PSTN Public Telephone Network is currently the most widely used network system. It has the advantages of wide coverage area, easy to use, low price, and easy networking. However, the network speed can only reach 56 kbps, the line quality is poor, the transmission rate is low, and the sound and image transmission of video conferencing is far from enough. The software-based video conferencing system can reach the image transmission rate of 4f/s. The biggest drawback is that the image quality is too poor, which will greatly affect the quality of the conference, which is rarely used.

Use an ATM Network
If you want a good video effect and it is convenient to access the ATM network, 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 signals. The biggest feature of this technology is QoS Assurance. We recommend this solution for organizations with high line conditions and high quality requirements. It features good image quality, convenient networking without connecting all the television Conference terminal lines to the MCU), high reliability. However, the cost of the device is high and an ATM network is required for access.

IP Network-Based System
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 enterprises and individuals with sufficient network bandwidth.

Satellite access
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 of multi-channel Conference videos, files and data broadcast. 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.

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.

1. Overview of broadband wireless access technology
2. Full explanation of Broadband Access Network Technology
3. Detailed description of the development history of Broadband Access Networks
4. Development of Fixed Wireless Access Networks
5. In-depth analysis of core technology of Optical Fiber Access Network