What is an IP phone?

The IP (Internet Protocol) phone started at 1995. The so-called IP phone is an application that transmits voice information in real time through TCP/IP protocol on IP network. The original IP telephone technology is just a computer-to-computer voice transmission technology. Both users must be connected to the Internet and have a set of IP phone software, sound card, microphone and speakers. So although you can talk, the range is very limited, and it is not a real IP phone. The real IP phone appeared in1March, 1996. An American company launched the service of transmitting international long-distance calls through the Internet, which realized the transformation of IP phone from ordinary phone to ordinary phone. At present, IP telephone has connected the Internet with the traditional telephone network through the gateway. As long as users have a telephone, they can make international calls online like ordinary telephone users, and the call cost is much lower than that of international calls. At present, IP phones can be divided into four types in form: PCmpC, telephone queue PC-phone, telephone -phone, and their business types also include IP fax (real-time and store/forward) and Web phone.

Second, the shortcomings and problems of IP phone

... the internet is not a real-time communication network. Although the utilization rate of the line is improved by using packet switching, the problem of "time delay" appears. "Time delay" refers to the time from the speaker to the receiver. If the delay exceeds the limit, people will feel unnatural. Generally speaking, if the delay exceeds 250m8, it will be unbearable. Traditional telephone communication callers do not know the time delay. IP phone needs to convert the voice signal of the calling party into a digital coded signal, group and package the digital signal, and transmit it in a store-and-forward way. At the receiving end, decoding, synthesis, recovery, etc. Are needed, so many delays (such as encoding, decoding, buffering, etc. ) is added. If the circuit is crowded, waiting for forwarding may lead to a long delay, and even lead to packet loss, so that the receiver can't hear or understand the speaker. During the period of 1999, China Telecom conducted an IP telephone test in 25 cities across the country. Its basic positioning is telephone voice service, which is specially designed for calls. Compared with the IP phone that uses the computer to surf the Internet, the connection rate and call quality have been obviously improved, and it is still being tested.

Third, the development of IP telephone.

Internet is a computer internet, and the early research on IP telephone technology mainly focused on telephone communication between computers and computer networks. The current research is mainly to solve the problem of combining with telephone network. This is because telephone network is still the largest, most widely distributed and most user-friendly communication network in the world. In recent years, although the number of computer users has increased rapidly, it is still much less than that of telephone users. Even in developed countries, there are several times more telephone users than computer users. If only computer users who surf the Internet can use IP phones, the scope of use will be greatly limited. In order to expand the use range of IP telephone, so that ordinary telephone users can also use IP telephone, it needs to be combined with telephone network. The main equipment connecting telephone network and Internet is voice gateway. At present, many large telephone exchange manufacturers have developed various new products.

With the rapid development of IP telephone, some people even estimate that "by the year 2000, international long-distance calls will be made through the Internet". Although this estimate is overdone, the emergence of IP phone has really affected the traditional telephone service through more and more Internet phones.

Extraordinary intellectual property rights

First, why can IP phones save phone bills?

The reason why IP telephone develops rapidly and attracts people's attention is that IP telephone can save a lot of money when making long-distance calls, especially international long-distance calls. Because ordinary long-distance calls are transmitted through the telephone network and IP calls are transmitted through the Internet, it can save a lot of money compared with ordinary long-distance calls. There are great differences between telephone network and Internet transmission (see attached table for main differences). List the differences between telephone network and Internet transmission.

Processing signal analog language signal digital data signal

Transmission mode circuit-switched packet switching

The charging method is based on the number of calls, time and distance, timely payment (such as monthly fee) and access rate.

At present, there is a complete set of organizational management.

The telephone network is established for telephone communication. Building a large number of telephone lines and wireless channels for telephone communication requires a series of switching equipment, transmission equipment and relay equipment, as well as corresponding operation and maintenance institutions and facilities, so the cost of telephone communication is very high. The charging method is calculated according to the number of calls, call distance and call duration. Internet is the Internet of computers. It was originally an academic network funded by the state, and its use was free. 1995 is only transformed into a commercial internet, and networking needs to be charged, but it still contains some public welfare attributes, and the charges are relatively low. The charging method is on schedule (for example, monthly) and according to the access rate.

As far as transmission technology is concerned, the telephone network adopts circuit-switched mode, that is, once the telephone communication circuit is connected, the telephone user occupies a channel, and whether the user is talking or not, as long as the user does not hang up, the channel will always be occupied. Under normal circumstances, one party is always talking, the other party is listening, and the listening party does not speak and occupies the channel, and there is always a pause in the process of speaking. So when using circuit switching, the line utilization rate is very low, and at least 50% of the time is wasted. The information transmission on the Internet adopts packet switching. The so-called packet switching is to convert digitized information. "grouping" and "packaging" according to a certain length; Each "packet" with address identification and control information is transmitted in a "store-and-forward" way in the network, that is, when the circuit is defective, it does not occupy a fixed circuit or channel for transmission, so it is called a "connectionless" way. This way can provide multiple information paths on one channel; In addition, data compression technology is usually used to transmit information on the Internet. After arriving at the destination, the compressed voice packets are recovered and synthesized into original voice signals to be sent to the receiving end users. Therefore, using the Internet to transmit voice information is many times more efficient than using the telephone network to transmit voice, which is also an important reason for greatly reducing telephone costs.

Second, the characteristics of IP phone

IP phone refers to the application of real-time transmission of voice information through TCP/IP protocol on the Internet, that is, VoIP.

... IP phone started at 1995 and was originally used only for voice transmission between computers. Both parties must be networked and equipped with corresponding software and multimedia equipment to talk. The real thousand-person telephone appeared in March, 1996. It combines the Internet with the telephone network through the gateway, enabling users to talk between ordinary telephones.

IP phone is transmitted through the Internet, so it takes up less resources and costs less than ordinary long-distance calls, especially when making international long-distance calls. The charging standard is: 0.30 minutes for domestic long distance; International call 4.8 yuan/min; Hong Kong, Macao and Taiwan, 2.5 yuan/min. In addition, due to the use of IP phones, local access fees need to be paid.

At present, the call quality of IP telephone is not satisfactory, and there will be some phenomena such as unclear voice, dropped call, delay and echo. However, with the improvement of Internet connection speed and technology, its voice quality will be further improved.

At present, the Ministry of Information Industry has approved several companies, such as China Telecom, China Unicom and China Jitong, to carry out IP phone trials based on the principles of active testing, timely opening and standardized management, and each company will launch calling IP phones and IP calling cards one after another.

There are three types of IP calling cards: prepaid cards (A), prepaid cards (B) and savings cards (C). At present, the experiment has opened a savings card. Each card has a different face value and a specified period of use. Every time I make a phone call, I will automatically deduct the phone bill.

The use of IP phone is similar to the current 200,300 calling cards, that is, users can get a private account and password after purchasing IP calling cards. When using it, they can dial the company's IP access number on any dual-tone phone, then enter the private account number and password according to the voice prompt, and then dial the called number.

In a word, IP telephone is the product of technological progress and has great development potential in the current communication field. I believe that with the update of technology and the standardization of the market, its prospects will get better and better!

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