Network Telephony Application of network development

Network Telephony Application of network development

First, the original telephone communication introduction

We are familiar with the telephone communication methods, generally there are two kinds. One is a wired landline, the other is a wireless mobile phone (where I see wireless landline phones as a landline). Although the two kinds of telephone communication in different ways, but all in people's communication life plays an important role, and there is no good or bad points.

(i), Cable fixed telephone

As the earliest generation of telephone communication, the cable phone since the generation of the technology and fixed-line appearance has more changes, but the basic principle of wireline communication still applies to now.

Next, I use a graph to illustrate the principle of wired fixed-line communication, see Figure 1.1:

Figure 1.1 Wired fixed-line communication schematic diagram

As shown, the user wired landline is connected through the switch, of course, there are many switches connected to each other and then to the different switches belong to the wired fixed communication between, here for the sake of simplicity, I only drew a switch.

The most important 5 functions of wireline fixed-line communication are as follows: acoustic and electro-acoustic conversion function, off-hook recognition function, the function of transmitting dialing signal, ringing function, and the function of electric connection between switches. It can be said that these 5 major functions are connected with the whole wired fixed-line communication process. Next, I use an example to illustrate the entire communication process of a wired landline.

We assume that user A wants to talk to User B, first of all, user A needs to do is dial to B, so a to send a dial signal to the switch, the switch is able to communicate with the user landline, because the switch provides 48v (national standard wired fixed voltage) voltage, through the current and the cable fixed contact. After the switch has received a dial signal, it is recognized that user A wants to make a call and will see if the dialed User B is idle, and if the User B is free, it sends a ringing signal to User B, so that User B hears the bell and then makes a call with a, so that through the switch, User A and B establish a special communication channel, so that the call connection is established, a and B call voice through the sound charge electro-acoustic conversion function to be transmitted, so the call was successful.

(b), Wireless mobile phone

Wireless mobile phone, without special instructions, the following we refer to the wireless mobile phone is what we often call mobile phones. As the product of cable fixed-line, wireless mobile phone has gradually become an important way of people's telephone communication because of its movable characteristics.

For the classification of wireless mobile, we can be divided into wireless mobile phone communication: Simplex Wireless mobile phone (of course, the single-work can be divided according to the frequency of the same frequency simplex and differential simplex), duplex wireless mobile phone. For simplex and duplex communication methods as shown in the following two diagram

Figure 1.2 schematic diagram of the same-frequency single-work communication

Fig. 1.3 Schematic diagram of duplex communication

The communication process of wireless mobile phone and its application technology are more complicated than the telephone communication, it contains the application of wireless communication technology, the multi-access technology of mobile communication (CDMA, TDMA, etc.), the voice coding technology of mobile communication system, the digital modulation and demodulation technology of mobile communication system, The continuous technology of mobile communication. Here I simply explain the communication principle process of mobile phone. The principle of mobile phone communication is as follows:

Figure 1.4 Mobile phone communication schematic diagram

For each mobile phone we call the MS (Mobile station), whether it is the same region (under the same base station) MS, or different regions of the communication between the MS, is to be connected through the BTS (Base station system), which is the mobile phone and fixed and walkie-talkie one of the main differences.

User A calls User B, first the user a dials to User B, the call signal is transmitted transparently to the MSC (SPC) via BTS and BTC (Base station control system), and when the MSC receives the signal, it analyzes the signal and passes the MSISDN ( The number in the public Telephone Network interchange network number plan uniquely identifies the mobile user number in the first few can analyze the number attribution, and then can be determined by the caller B in which HLR (location register, which holds the number resources and user information, is a large database), in HLR The database contains the MSC to which the number belongs, and the MSC is used to locate User B under that attribution, so that a connection can be made between users A and B to make a call.

For the contents of HLR database, we can refer to the schematic diagram given by Nokia, as shown in:

Figure 1.5 HLR DATABASE structure diagram

Second, Internet telephony (VOIP)

For the new way of telephone communication, Internet telephony has hooked up the golden period of the development of computer network, such as: SKYPE, UUCALL, shutter, forex, micro-meeting and so on. The most intuitive understanding of VoIP is the connection of the PSTN (Public switched telephone system) to the Internet and the transmission of the PSTN's voice data over the Internet.

VoIP Network Telephone (also known as IP phone or VoIP) is based on the IP technology of packet, digital transmission technology, the basic principle is: Through the speech compression algorithm to the voice data compression encoding processing, and then these voice data by IP and other related protocols to package, after IP The network transmits the packet to the receiving place, and then the voice packets together, after decoding decompression processing, restores the original voice signal, thus achieves the purpose which transmits the voice by the IP network. This is shown in schematic 2.1.

    In the realization of network telephony GW (Network Telephony Gateway) is the most critical part, so to speak of the realization of VoIP, it is in the GW to solve the conversion between voice data and digital data, so that the PSTN voice data in the form of computer network data transmission in the Internet, Then turn the Internet network data into PSTN voice data and establish voice calls.

Figure 2.1 Schematic diagram of the network telephony communication process

Above is just the basic communication principle of network telephony process, different network telephony products also have different means of communication, here we might as well see two more familiar with the network phone. So as to explain the different network telephone communication methods.

Here I list easy letter (NetEase and China Telecom cooperation products) and micro-games (more play the company developed products, of course, its voice service also with the help of YY voice technology) two VoIP products. The two ways of talking are completely different, especially the micro-meeting, which uses the callback method. Through the host server callback method to achieve free calls on both sides. The caller dials the caller's phone through a micro-dial, and the server dials the phone to the caller, and the caller calls the callee, and then chooses to listen after the call, and the two sides establish communication. During the call, both parties are in the receiving phone status. The communication process is as follows:

Figure 2.2 Micro-communication process diagram

Both are declared free on the phone, but both are VoIP phones, and dial-up needs to be done in a network environment, so this is free of charge, and the free way for both is very different. Micro-dial needs to connect to the server, this process is to consume about 1kb of traffic to send dialing information to the server. The entire process of its call is free of charge and does not require consumption of traffic. Forex has experienced the easy-to-believe user calls need to consume traffic to call the transition, it is different from the micro-meeting is the operator-China Telecom's voice route, which undoubtedly enhance the quality of its voice calls, because we know that the network phone transmission is actually used UDP, although the timeliness of UDP is better, But because it is unreliable connection, so it is easy to drop packets, resulting in poor voice signal quality and so on. Therefore, in contrast to the micro-meeting, the credibility of the call quality in China Telecom's strong basic support accounted for the advantage.

Third, the advantages and disadvantages of network telephony

Internet telephony compared with the original telephone communication, it can be said that each has advantages and disadvantages, the future of telephone communication will likely appear three strong situation. Below we can use a table to illustrate the advantages and disadvantages of the network phone and the original two kinds of telephone.

call mode	call quality	cost fee	call charges	can I ext	can I machine multiple numbers	flexibility	security
fixed phone	best	less	less	Yes		poor	Better
mobile phone	Better (external environmental impact)	less	less	no	no	best
Internet telephony	Poor (network environmental impact)	At least	No (some products are subject to roaming charges)	Whether	Whether	Good (some products are also mobile phone-side)	The network is open to the outside, relatively poor

Table 3.1 Comparison of network telephone and original telephone mode

Iv. Summary

Internet telephony has such a big advantage, and even can do free calls, that future VoIP will replace the original call mode? I personally think that while VoIP has created a new model for telephone calls to some extent, it is not enough to replace the original calling method. The shortcomings of the above also said that, in addition, operators can not be justified, especially the traditional telephone communication operators (China Mobile, Unicom, Chinese telecom, etc.), they really will give up the cost of the call to profit? I personally think that the reason why VoIP operators make free calls, to a certain extent, more strategic significance, user resources will sometimes determine the future survival of a product.

However, the network phone does bring us convenience, but also promote the development of telephone communications, therefore, network telephony will be the future of network development is another important direction.

Network Telephony Application of network development