Low-speed data packaging method embedded into high-speed Ethernet frame structure

Abstract

The invention discloses a low-speed data encapsulation method based on a high-speed Ethernet frame format. Multiple paths of low-speed data adopt a high-speed sampling data acquisition mode, are packaged into a short frame format through a CPLD (Complex Programmable Logic Device) or an FPGA (Field Programmable Gate Array), and are embedded into a normal high-speed Ethernet code stream for long-distance transmission. And the first bit of the SFD of the Ethernet frame is used for distinguishing and judging the low-speed data frame and the Ethernet frame. The frame length of the low-speed data can be defined according to the number of channels of the low-speed data needing to be transmitted, and each bit position in Ethernet bytes can transmit one path of low-speed data. The insertion frequency of the low-speed data frame depends on the overall transmission bandwidth of the low-speed data. The low-speed data frame designed by the invention occupies the idle period of the normal Ethernet frame, and the insertion mechanism is shown in the attached drawing, so that the synchronous transmission of the low-speed data and the Ethernet data is realized. According to the method, the residual bandwidth resources in the Ethernet frame format are effectively utilized, and meanwhile, the bandwidth, the baud rate and the content safety and reliability of the low-speed data are ensured.

Description

Technical Field

[0001] The invention relates to a low-speed data encapsulation method based on a high-speed Ethernet frame format, belonging to the technical field of integrated multi-service transmission, Ethernet data transmission and low-speed data transmission. Background Art

[0002] In integrated multi-service networks and Ethernet data networks, it is usually necessary to transmit low-speed data simultaneously with Ethernet data packets, such as RS232, RS422 or some monitoring alarm channels. There are two common solutions. (1) Encapsulate low-speed data into IP packets, transmit them through the network, and then parse the IP packets at the receiving end to restore them to low-speed data signals. In this way, each low-speed data channel needs to occupy an independent IP address and port, and it needs to be set up with complex network settings and low-speed data format settings before it can work. It is difficult to achieve completely transparent transmission. The technical implementation of this method requires more complex software and more processor operations, so the implementation cost is relatively high. (2) It is implemented through the time division multiplexing method of traditional optical terminals. This method requires the use of high-speed serial-to-parallel and parallel-to-serial conversion chips, which has a high implementation cost. In addition, the optical fiber interface is a private protocol and cannot be connected with equipment from other manufacturers, which greatly limits the compatibility and interoperability of Ethernet services. Summary of the invention

[0003] In order to solve the many shortcomings of low-speed data transmission in the existing Ethernet data network, a low-speed data encapsulation method is invented. The present invention uses Ethernet as the transmission channel, and uses the Ethernet link 1000Base-FX interface in optical fiber mode when the transmission distance is long. The multi-channel low-speed data is collected by high-speed sampling, and then the data is encapsulated into a short frame format using a CPLD or FPGA circuit, and embedded into a normal Ethernet service code stream for remote transmission. At the receiving end, the sampling value in the Ethernet data short frame is restored to the original low-speed data, thereby completing the remote transmission of low-speed data through high-speed Ethernet.

[0004] In order to achieve the above object, the present invention adopts the following technical solutions: The signal processing process and system functions are shown in Figure 1.

[0005] The format of the data frame complies with the protocol requirements of the Ethernet physical layer, and is divided into PREAMBLE (preamble), data frame identifier, and sampling value. The preamble PREAMBLE is an 8-bit sequence 10101010, which is the bit sequence required by the Ethernet physical layer to synchronize Ethernet frames. The following bit is defined as the data frame identifier. When its value is 0, it indicates low-speed data. This bit is actually the first bit of SFD in the Ethernet frame. When its value is 1, it indicates Ethernet data. Therefore, according to the value of this bit, it can be determined whether the current frame is a data frame or an Ethernet frame, thereby realizing code stream separation on the receiving side. In the sampling value part, the length can be customized according to the number of data channels to be transmitted. Each bit position in the byte can transmit one low-speed data. If a data byte is defined, 8 low-speed data can be transmitted. The total number of bits of the preamble, identifier, and data in a data frame should be an integer multiple of the byte. The preamble, identifier, and data sampling values ​​of each channel in the data frame format are as follows: Figure 2 shown.

[0006] The insertion frequency of data frames depends on the transmission bandwidth requirements of low-speed data. Generally, a frequency of 1.25MHz or 2.5MHz can meet the transmission requirements of low-speed data at a baud rate of at least 115200. When Ethernet is fully loaded, its frame gap is small and it is not suitable to insert more data frames.

[0007] There is an idle period of at least 12 bytes between normally transmitted Ethernet frames. The data frame designed by the present invention is inserted into the idle period of the normal Ethernet frame, so that it can be transmitted together with the Ethernet service without affecting each other. The low-speed data frame insertion mechanism is as follows: Figure 3 As shown in the figure, each data frame or data frame and Ethernet frame must meet the minimum interframe gap (IFG) requirement.

[0008] The beneficial effect of the present invention is that, based on the transmission channel of high-speed Ethernet, low-speed data is transmitted by embedding low-speed "data frames", the method is simple, reliable and cost-saving. The present invention does not need to configure and occupy valuable IP addresses and ports, does not need to configure the equipment, is plug-and-play, and is convenient for engineering installation, activation and maintenance. The present invention is completely transparent to the content, baud rate and format of low-speed data and has good compatibility. When the system is connected to an ordinary Ethernet fiber optic interface or cable interface, although low-speed data cannot communicate, Ethernet services can still maintain normal transmission, and the Ethernet connection will not fail due to the embedding of low-speed data. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 Signal processing process and system functions. Figure 2 Preamble, identifier, and data sampling values ​​of each channel in the data frame format. Figure 3: Low-speed data frame insertion mechanism.

Claims

1. A low-speed data encapsulation method embedded in a high-speed Ethernet frame structure, characterized in that: Low-speed data is collected through high-frequency data and embedded into high-speed Ethernet code stream for long-distance transmission.

2. According to claim 1, it is characterized in that The SFD byte of the high-speed Ethernet frame is used to distinguish low-speed data frames from normal Ethernet frames through its first bit value, thereby achieving code stream separation.

3. The low-speed data encapsulation method according to claim 1, characterized in that Low-speed data frames occupy the idle bits between high-speed Ethernet frames.

4. The low-speed data encapsulation method according to claim 1, characterized in that The length of the low-speed data frame can be defined according to the number of low-speed data channels that need to be transmitted, and any bit position in the byte can transmit one low-speed data channel.

5. The low-speed data encapsulation method according to claim 1, characterized in that The minimum interframe gap (IFG) requirement must be met between each low-speed data frame or between a low-speed data frame and a high-speed Ethernet frame.

6. The low-speed data encapsulation method according to claim 1, characterized in that The embedding frequency of the low-speed data frame depends on the overall transmission bandwidth of the low-speed data.

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