Seven ways for the conference call system to access the network. For most users, the most important factors for the teleconferencing system are the following: audio phone quality, system price, system security and scalability. There are two main situations in the current ubiquitous network environment. One is based on circuit-switched networks, such as ISDN, DDN, and PSTN. The other is a packet-switched network such as ATM, IP, Frame Relay, and so on.
Using ISDN lines
For most individual users and small business users, access to ISDN lines is a more economical option. ISDN utilizes a public telephone network to provide end-to-end digital channel connections to users for carrying various telecommunication services, including voice and non-voice. Conference television is transmitted over the ISDN channel using ISDN lines at rates ranging from 384 kb/s to 2 Mb/s. Since ISDN performs communication charging according to the B channel (64 kb/s) used, the domestic communication rate of the 1B channel is equivalent to the ordinary telephone communication rate (the most widely used circuit switching method).
For users with less communication and shorter communication time, the cost of using ISDN is much lower than the cost of renting DDN line or frame relay circuit, and it has the characteristics of high speed, low investment, convenient networking, etc. System application requirements. However, the national ISDN network is still in the process of continuous upgrading, and the reliability and stability are still insufficient compared to the dedicated line.
Rent a DDN line
Large enterprises and institutions often have high requirements for telephone effects. At this time, the access mode of the DDN line can be selected. The DDN dedicated line has high transmission quality, small network delay, high circuit reliability, high network security, and convenient networking. Although DDN has the above advantages, the digital circuit provided by DDN is a semi-permanent connection, that is, the connection is maintained regardless of whether the user transmits data, so the cost is relatively high, which is not suitable for users with short communication time, but only for long Time-to-point and multi-point-to-point communication connections because the DDN line charges for the number of peer-to-peer. If some subordinate departments of the group users are connected to the company headquarters, they can use the multi-point-to-point DDN line networking. However, if subordinate departments need to communicate frequently, if they take a point-to-point connection, the company's subordinate departments will form a mesh. Net, so the cost of the user is too high.
System using PSTN
For ordinary individual users, if you want to try a conference call, you can try PSTN access. The PSTN public telephone network is currently the most widely used network system, and its advantages are wide coverage, easy to use, low price, and easy networking. However, the network speed can only reach 56 kbps, the line quality is poor, and the transmission rate is low, which is not enough for the voice and image transmission of the conference call. The software-based teleconferencing system can achieve an image transmission rate of 4f/s. The biggest disadvantage is that the image quality is too poor, which will greatly affect the quality of the conference, and is generally used rarely.
Using an ATM network
If you want a good phone effect and access to the ATM network is very convenient, the ATM network access method is also an option. ATM is an asynchronous transfer mode that combines the advantages of circuit switching and packet switching to deliver wideband signals at any rate that can carry voice, data, image and telephony signals. The biggest feature of this technology is QoS guarantee. This scheme is recommended for units with line conditions and high quality requirements. It is characterized by good image quality and convenient networking (no need to connect all video conference terminal lines to MCU), high reliability. However, the equipment costs are high and an ATM network is required for access.
IP network based system
The easiest way to access is the IP network. IP-based networks use packet switching technology because packet switching does not guarantee order and fixed delays, so there is no guarantee of fixed latency and bandwidth. In order to better solve the service quality of real-time communication, protocols such as UDP/IP, RTP, RTCP, and RSVP are adopted. The teleconferencing system applied to broadband IP networks such as ADSL and FTTB+LAN has achieved good results. Today, IP networks are ubiquitous, and this method is convenient and inexpensive. However, since the packet-switched IP network follows the principle of best effort delivery, the conference call effect of this access method is worse than that of ISDN and DDN. However, its good cost performance has been favored by more and more users, especially for small and medium-sized enterprises and individuals with sufficient network bandwidth.
Use satellite access
Satellite network has the performance advantage that the ground network can't match in the long-distance teleconference. It can cover remote areas such as sea and mountains, with high transmission rate and good security. It is flexible and convenient for the construction and relocation of the venue. It is a multinational company. A good choice, the satellite broadband teleconferencing system supports the integrated delivery of multi-party conference calls, files and data. The disadvantage of this scheme is that it is expensive. In addition to the channel fee for renting satellites, the construction cost of each satellite ground station is about 200,000 yuan. At the same time, satellite communication has a large delay and is not suitable for teleconferencing systems with high real-time requirements.
Frame relay mode
The frame relay access mode is also a professional conference access method. The frame relay technology is mainly used to transmit data services. The frame relay frame is suitable for encapsulating data units of a local area network and transmitting burst services. It is a way of wide area network communication. The network has high efficiency, large network throughput, low communication delay, and the access rate of frame relay users ranges from 64 kbit/s to 2 Mbit/s, and even reaches 34 Mbit/s. Frame Relay-based networks are expensive, but the phone is good.
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