Point to point SMS

there is a detailed explanation here

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Point-to-point SMS refers to the business form of sending and receiving text messages between mobile phones. The forms of peer-to-peer short messages include intra-network short messages, inter-network short messages and international short messages. Point-to-point SMS is an independent user communication tool in the abstract. This communication tool may be a mobile phone, a client software, a PDA, etc. But no matter what the point is, the most basic purpose of point-to-point SMS is to realize the mutual communication between two or more points, which is what people usually call chatting.

the basic function of point-to-point short message service is chat, which can be classified into point-to-point chat, industry/enterprise application (point-to-multipoint in nature), self-written short message, inter-network communication and international communication.

As a brand-new and relatively independent interactive mode, SMS has become another way for people to obtain information. With the deepening of short message culture, point-to-point short message has become one of the main ways for people to chat remotely. Point-to-point short message combines the characteristics of convenience, wide range of use, storability and retransmission of mobile phones, and has the advantages of low price and no loss of information when turned off. It is short and convenient, and can be said to be an "electronic note". At present, SMS is the only service in GSM network and CDMA network that does not require the establishment of end-to-end service path, and it can be transmitted even if the mobile station is in complete circuit communication. Short message communication is limited to one message, in other words, the transmission of a message constitutes a communication. Therefore, the service is asymmetric, and it is generally believed that mobile initial short message transmission and mobile terminal short message transmission are two different things. This does not hinder real-time conversation, but the system thinks that different messages are independent of each other, and the transmission of messages is always relayed by the Short Message Service Center (SMSC) outside GSM. Messages have destinations or origins, but they are only related to users and SMSC, and have nothing to do with other GSM infrastructures.

The convenience and quickness of point-to-point short messages are mainly manifested in the following aspects: from the perspective of communication, communication means are more convenient and communication speed is accelerating, which actually brings about the increase of communication frequency and the expansion of communication content. The effect of communication can get immediate feedback. People can communicate at any time, no matter big or small, from "talking in a few words" about something in the past to exchanging jokes and exchanging views. From the perspective of interpersonal communication, most famous enterprises are using SMS to communicate with their members and customers in time, which helps to form a stronger communication relationship. Compared with traditional communication methods, the advantage of SMS is that it can be communicated at any time, any place and with any topic. It is more casual than making phone calls and more mobile than chatting online. As a communication based on wireless network, short message has the advantage of unknown internet communication: you can meet new friends through wireless QQ or mobile short message chat services opened by major websites under the premise of privacy.

Early point-to-point short messages were limited to the same operator's network. However, with the rapid development of point-to-point short message services, the increasing number of users and the dispersion of user groups among different operators, it put forward practical requirements for short message exchange between different operators, so operators gradually reached an agreement to allow short message exchange between their respective systems. This is what people often say. In 22, China Mobile and China Unicom reached an agreement, and the two companies realized wireless short message service nationwide. The two competitors finally joined hands to cross a hurdle in China's telecom history, which made their short message business turnover soar rapidly. From the perspective of user experience, there is no difference between peer-to-peer short message service and peer-to-peer short message service in the network, except that a module called interworking gateway is added between systems of different operators, which is responsible for protocol conversion. With the diversified development of value-added services, short message interworking has gradually developed into mobile-Unicom interworking, mobile-fixed network interworking, mobile-PHS interworking, domestic-international short message interworking and so on.

The implementation of point-to-point SMS is a transaction, which is a complete transaction from the initiation of one user to the successful reception of another user. Simply put, if any link fails in this process, the whole link fails. Figure 1.1 illustrates the sending of a short message. My father sends a short message, and the information to be input includes the message content and the number of the receiver (in early mobile phones, the user also needs to set the number of the SMS center of the operator), and the message is transmitted to Xiaoqiang's mobile phone through the communication network. During transmission, the message can be stored and forwarded, and when Xiaoqiang's mobile phone can't receive it, the message can be temporarily stored; If the sending fails, the father will get a receipt of the sending failure; If Xiaoqiang receives the message, he can get the number of the receiver and the content of the message, so that a peer-to-peer transaction is over. When Xiaoqiang replied to the text message, it was actually the beginning of another peer-to-peer transaction. Technically speaking, in the transaction of point-to-point SMS, message sending is divided into two categories: MO/MT. MO means the message goes up, that is, people often say sending letters, and MT means going down, that is, people often say receiving letters.

figure 1.1 example of point-to-point SMS

the processing flow of point-to-point service is shown in figure 1.2. When a user sends a short message to the SMS platform, the platform first authenticates the numbers of the sender and the receiver, including the sender's fee status and the receiver's status. If the sender is in arrears, it is forbidden to distribute; If the receiver cannot receive it temporarily, store and forward it; If all the authentication conditions are met, send a short message. After the message is successfully issued, a billing bill is issued to the sender's number, and the charging information is transmitted to the accounting system, and the accounting system charges the user. In addition, SMS system should provide users with perfect customer service, including short message value-added services to be mentioned later.