With the development of Beidou satellite application technology in our country, the number of end users of Beidou satellite is also increasing in a large scale. In military, industrial and civil fields, Beidou communication terminals are deployed in large quantities to provide positioning and communication functions. Beidou Short Message Channel is a very narrow channel. Beidou Communication Terminal controls the size of sending a short message data between tens of bytes and hundreds of bytes according to the level of Beidou User Card, and Beidou Communication Terminal has the control of sending interval when sending short message data, thus making a single Beidou Communication Terminal. Sending short messages requires a second-to-level interval. Limited to the above conditions, it can be seen that when using a single Beidou short message channel to transmit large data, the data need to be subcontracted and sent at intervals according to the level of the card. Under this condition, coupled with the unreliability of the wireless signal itself, the transmitted data can not guarantee its accuracy and timeliness. 。 Based on this situation, we need a technology to expand the use of existing Beidou communication terminals, so as to share the Beidou Short Message Channel. In view of the problems raised in the introduction, this paper designs a data forwarding controller based on Beidou communication terminal, hereinafter referred to as Beidou data forwarding controller.
Beidou Data Forwarding Controller is mainly used to receive and forward short messages from Beidou in many directions.
It connects with the data serial port of Beidou communication terminal. At the same time, thermostatic element it will provide two kinds of data interfaces for external access: data serial port and network port. Beidou Data Forwarding Controller retains the conventional access means of Beidou Communication Terminal, that is, Beidou Short Message Use Equipment directly uses serial port to connect Beidou Communication Terminal, according to this way, it can still receive and receive conventional Beidou Short Message; Beidou Data Forwarding Controller supports the use of this mode while maintaining its use. External Ethernet network ports and data serial ports are connected to other devices or networks to realize the sharing of Beidou communication terminals and the expansion of data interface types. Beidou Data Forwarding Controller has the control functions of adding or deleting packet headers and priority permissions. It can realize the transmission strategy control of different data sources and different priority data messages. Beidou Data Forwarding Controller receives and forwards Beidou Short Message of all external data interfaces, and adds and deletes packet headers to process data, so that data can be transmitted in serial ports and networks. When the data message carries priority level information, the forwarding controller stores the data in Beidou short message sending queue, and sends the data in the queue first. When receiving the Beidou short message message without priority level information, the forwarding controller first determines whether there is priority level information in the queue, if not, it will send the normal short message, if not, it will discard the short message.
Beidou data forwarding controller sends short message data to Beidou communication terminal through Beidou serial port after data processing. Beidou Data Forwarding Controller receives Beidou Short Message and forwards it from all external serial ports. The application example of Beidou Data Forwarding Controller is shown in Figure 1. The Beidou serial port of Beidou Data Forwarding Controller is connected with the serial port of Beidou Communication Terminal. The Beidou Data Forwarding Controller will query the basic information of Beidou Card ID, data transmission frequency and card grade of Beidou Communication Terminal through Beidou General Management Protocol. Beidou data transponder will determine the maximum message length and transmission time interval of sending a single Beidou short message message by card frequency and level. All Beidou short messages need to be sent to meet this condition, otherwise they will be filtered out, and the failure status information will be sent back to the sending source to the controller. The process of data processing for sending short messages through network ports is shown in Figure 2. (a) Beidou Data Forwarding Controller receives Beidou Short Message Data Message from the network port, matches the port and address of the message, and checks the data format of the message if it meets the request identification of Beidou Short Message. B) When the message is checked correctly, the controller will extract the priority level information field of the message. If there is a priority level information field, the Beidou short message sending queue of the current Beidou Data Forwarding Controller will be rearranged according to the size of the field, and the length of the queue will be fixed, and the data with the lowest discarding order will be kept.
C) The forwarding controller sends data through Beidou serial port according to Beidou General Protocol. Data Serial Port Short Message Processing. Beidou Data Forwarding Controller receives Beidou Short Message Data Message from data serial port, and then forwards the data directly from Beidou according to Beidou General Management Protocol. Data serial port receives short message data processing process. Beidou data forwarding controller receives Beidou short message data from Beidou serial port and sends data from data serial port. The Beidou data forwarding controller will not process the data message. It directly forwards the short message data from the data serial port. Network serial port receives short message data processing process. Beidou Data Forwarding Controller receives Beidou Short Message Data from Beidou serial port and sends data from network port. Beidou Data Forwarding Controller will add multicast IP header to the short message data, and then send it from network interface, so that the monitoring terminals in LAN where the network interface is located can receive the data.
Beidou short message information with IP header. The main purpose of Beidou Data Forwarding Controller designed in this paper is to receive and forward short messages of Beidou in multiple directions, so as to realize the shared use of Beidou communication terminal and the expansion of access interface type.
The control function of Beidou Data Forwarding Controller in this paper is to add and delete data header and priority permission. It can realize the forwarding of different data sources and the transmission strategy control of different priority data messages.
By implementing the message priority permission control service of Beidou Communication Terminal, it ensures the transfer of high-level permission short message data.
Send processing meets the transmission strategy control of personalized network.