Video Conference

With the popularization of video conferencing systems, users have more comprehensive and in-depth requirements for their functions. On the basis of providing basic functions, video conferencing systems should also meet the growing user needs, such as the increase in the number of interactive objects, the improvement of video quality, and the enhancement of security and confidentiality. This also poses further requirements for improving the environment (technical conditions) required for implementing video conferencing systems. Only under more perfect technical conditions can video conferencing provide higher-quality audio-visual interaction services and promote the further popularization of video conferencing system applications.

Bottlenecks in the current application environment of video conferencing systems

1. Lack of guarantee for network service quality (QoS)
   The real-time interactivity of video conferencing systems places QoS requirements on the network, including basic bandwidth, packet loss rate, latency (time delay), and jitter. Without the guarantee of these quantified QoS indicators, obstacles will occur in our real-time audio and video communication: connection loss, indistinguishable images, interrupted sound, significant signal lag, discontinuous pictures, etc. So far, the underlying support network for video conferencing systems has mainly been the IP network, which is also the development trend of communication networks. However, traditional IP networks do not provide QoS guarantees. They were initially designed for simple data communication, are open and shared, and are characterized by "best-effort" service. To provide a large amount of real-time multimedia communication services on such a network environment, some additional measures must be taken.

At present, there are already some relatively mature solutions. RSVP (Resource Reservation Protocol) operates on the IP protocol. Its basic idea is to achieve end-to-end service quality guarantee through the reservation of end-to-end resources. RTP/RTCP (Real-time Transport Protocol/Real-time Transport Control Protocol) is also one of the real-time transmission measures on the IP network. RTP is a protocol running on UDP, which encapsulates data; the RTCP control protocol is used in conjunction with the RTP data protocol, providing feedback information on data transmission quality so that the application system can adopt corresponding strategies and processing. DiffServ (Differentiated Services) defines a method to achieve IP QoS: based on the classification and identification of the data carried by the IP layer, different processing strategies are given to different types of data, achieving a certain level of QoS guarantee for different levels. To fundamentally solve the problem of network QoS, the field of network communications has also carried out a large amount of research, preparing to fully guarantee the quality of network services on the next-generation IP network (IPv6). In this way, video conferencing systems will have a more perfect network environment.

1. Bandwidth problem of the access network
   The bandwidth resources of the communication network required by video conferencing systems encounter bottlenecks at the access network. The bandwidth of the backbone transmission network is generally on the order of Gb/s or Tb/s, which is quite abundant, while the access network at the user terminal is relatively tight. At present, the main access methods for network users include dial-up access, xDSL (Digital Subscriber Line), optical fiber access or HFC (Hybrid Fiber-Coaxial) access, and wireless access. The data transmission rates of optical fiber or HFC access are relatively high (about 10 Mb/s), but the prices are relatively high, and the application is not yet widespread; xDSL is relatively popular, such as ADSL (with an upstream rate of 128 - 768 kb/s and a downstream rate of 2 - 8 Mb/s); dial-up is gradually fading out of the market as its capacity is limited (within 56 Kb/s). Now let's look at the bandwidth requirements of video conferencing systems. Ignoring the data occupation, a voice signal requires 6 Kb/s (refer to ITU-T G.723 specification), and an image signal requires 64 Kb/s (refer to MPEG-4 standard). A video conferencing system terminal requires about 80 Kb/s of upstream bandwidth and N×80 Kb/s of downstream bandwidth, where N is the number of users participating in the communication. From this, it can be seen that although ADSL can support the application of video conferencing systems, the number of users participating in the interaction is limited to one person. For video conferencing systems to become tools for people's daily work and life, there should not be such a limitation. Therefore, optical fiber access is the inevitable development trend of access technology.

2. Network access obstacles
   Video conferencing systems need to transmit various types of information such as voice, images, data, and control signals, requiring a large amount of network resources, such as establishing connections, obtaining real IP addresses, and using multiple ports. However, facilities such as firewalls, proxy servers, and routers in the actual network impose numerous restrictions on the operation of network resources.