JPH0232637A - Frame synchronizing system by synchronous packet - Google Patents

Abstract

PURPOSE:To easily identify a data packet from a synchronous packet by setting at least one bit in an error detecting code at 0 in the case of setting all bits at 1s and at 1 in the case of setting all bits at 0s when all the header parts of the data packet are set at 1s by using the values 1 or 0 of all bits in the synchronous packet. CONSTITUTION:A data packet forming part 2 forms the data packet by attaching the error detecting code corresponding to a header at an error detection code generating part 3, and synthesizes the output of the error detection code generating part 3 and information data at a synthesizing part 4, and outputs it to a transmission path via the transmission part 6 of the packet. When the header of a formed data packet is the pattern of a part equivalent to the header of the synchronous packet, the error detection code generating part 3 generates the pattern in which no coincidence with the part corresponding to the error detecting code of the synchronous packet is obtained. Since the pattern of the synchronous packet is supplied to a reception part 8 in advance, it is compared with the pattern. In such a way, it is possible to identify whether a reception packet is the synchronous packet or the data packet.

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) This invention relates to a frame synchronization method using synchronization packets that realizes synchronization packets in a transmission system that establishes frame synchronization using fixed-length synchronization packets. Regarding.

(Prior Art) An example of a frame format in a conventional packet transmission system is shown in FIG. In the conventional frame synchronization method, frame bits having synchronization information are periodically outputted onto a transmission path, and frame synchronization is established by detecting the frame bits. That is, as shown in Figure 3, the transmitting side repeatedly sends the values 1 and 0 as synchronization information periodically, and the receiving side transmits the values at the three locations shown in the figure at the same frame period as the transmitting side. The receiving side determines that synchronization has been achieved by shifting the bits in order, and when repeating bit information of 0, 1.0, for example, appears.

This frame period, the error rate on the transmission path, and the transmission efficiency are closely related, and once the error rate on the transmission path is determined, the frame period that maximizes the transmission efficiency is uniquely determined. but,
Conventional frame synchronization systems have a fixed frame period, so they have the disadvantage of not being able to respond to changes in error rates. Therefore, the method establishes frame synchronization by putting information for frame synchronization in packets (packets with this synchronization information will be referred to as synchronization packets from now on) instead of in synchronization bits, and transmitting these synchronization packets at certain intervals. is possible. In this method, it is possible to change the frame period by changing the transmission interval of synchronization packets, but in such cases, the same bit string as the synchronization packet may exist in the information packet. arise. It was difficult to determine whether a received packet was a synchronous packet.

(Problems to be Solved by the Invention) As described above, frame synchronization can be achieved using synchronization bits or synchronization packets. In order to accommodate changes in the error rate, when synchronizing frames using synchronization packets, it is possible to vary the frame period. However, if an information packet used for information contains the same bit string as a synchronous packet, even if it is an information packet, this bit string is judged to be a synchronous packet, making it difficult to distinguish between an information packet and a synchronous packet. .

The present invention has been made in view of these points, and it is an object of the present invention to provide a frame synchronization method that allows easy identification of synchronization packets and information packets.

[Structure of the Invention] (Means for Solving the Problems) In order to achieve the above object, the present invention includes a data packet forming unit that forms a fixed length packet consisting of a header, an error detection code, and information data; In a fixed-length packet transmission system including a synchronization packet forming unit that forms a synchronization packet for establishing frame synchronization with the same fixed length as the long packet, the synchronization packet formation unit sets the value of all bits of the synchronization packet to 1. If all the header values of the fixed-length packet formed by the data packet forming unit are 1, the data packet forming unit sets at least one bit of the error detection code that detects an error in the header to 0. It is characterized by this.

Another aspect of the present invention provides a data packet forming unit that forms a fixed length packet consisting of a header, an error detection code, and information data, and a synchronization packet that has the same fixed length as the fixed length packet and establishes frame synchronization. In a fixed-length packet transmission system comprising a synchronous packet forming unit that forms a If all the values are 0, the data packet forming unit uses error υ to detect header errors.
This is characterized in that at least one bit of the detection code is '11'.

(Operation) A synchronization packet that has the same length as the fixed length packet formed by the data packet formation section and is used to fully establish frame synchronization is formed in the synchronization packet formation section. Values of the same sign are used for the values of all bits of this synchronization packet. That is, the values of all bits may be set to 1 or 0. If the header and information data are formed in the data packet forming section and the bit pattern of the header matches the bit pattern of the part corresponding to the header in the synchronization packet, the error detection code in the synchronization packet A synchronization packet consisting of an error detection code, a header, and information data set so that the bit pattern of a corresponding part and the bit pattern of an error detection code of a fixed-length packet do not match is formed and formed.

That is, when all the values of the header of the fixed-length packet are 1, at least one bit of this error detection code is set to O, or the value part of the header of the fixed-length packet is controlled.

(Example) Hereinafter, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows an example of a transmission system to which the frame synchronization method of the present invention is applied. On the transmitting side in FIG. 1, a synchronization packet forming unit 5 stores a synchronization packet pattern, refers to the pattern, periodically forms a synchronization packet, and transmits the packet via the packet transmission unit 6. Output on the transmission path. As a pattern for a synchronous packet, consider, for example, a pattern in which all bits are '1' and a pattern in which all bits are '0'. Therefore, periodically on the transmission path, all these bits are '1'. When a packet whose bits are 1'' appears, a packet whose bits are all 0 appears. On the other hand, when the header and information data are input to the data packet forming section 2, the data packet forming section 2 adds an error detection code corresponding to the header to the error detection code generating section 3 to form a data packet. The output of the error detection code generating section 3 and the information data are combined in the combining section 4 and outputted onto the transmission path via the packet transmitting section 6. If the formed data packet has a pattern in which the header corresponds to the header of a synchronous packet, that is, if all bits are "1", the error detection code generation unit 3 generates an error detection code of the synchronous packet. A pattern that does not match the corresponding part, ie, a pattern in which at least one bit of the error detection code is "0", is generated.

The packet receiving unit 8 on the receiving side that receives packets on the transmission path is given a synchronous packet pattern in advance, and by comparing it with the pattern, it is possible to determine whether the received packet is a synchronous packet or a data packet. identification. Then, within the receiving side 7, the frames are synchronized and the information data is processed.

Next, the structure of these packets will be explained using FIG. 2. FIG. 3(a) shows one structure of a data packet. This packet consists of an error detection code section for detecting errors in the header section and bottom section, and an information data section. Figures (b) and (c) show one structure of a synchronization packet. The data packet and synchronization packet have the same length. The same figure (bl is one in which all bit values are 1, and the same figure (C
) uses all bit values of 0. Frame synchronized packet communication is performed using these data packets and synchronization packets.

〔Effect of the invention〕

As described in detail above, according to the present invention, if all bits are 1 or all bits are 0 in a synchronization packet, and the head of the data packet is all 1, an error can be detected. By setting at least one bit of the detection code to 0 in the former case and 1 in the latter case, it is possible to prevent synchronization packets and data packets from being confused, and to make data packets and synchronization packets easily distinguishable. .

Furthermore, compared to the conventional frame synchronization method, the frame period can be easily varied according to the length of the synchronization packet.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of the present invention, FIG. 2 is a diagram showing one configuration of a packet of the present invention, and FIG. 3 is a diagram showing a conventional packet configuration. 2... Data packet forming unit, 3... Erroneous detection code generating unit, 5... Synchronous packet forming unit. Agent: Patent Attorney: Nori Chika Rent: Hikaru Matsuyama

Claims (2)

[Claims] (1) A data packet forming unit that forms a fixed length packet consisting of a header, an error detection code, and information data, and a synchronization packet formation unit that forms a synchronization packet for establishing frame synchronization with the same fixed length as the fixed length packet. In the fixed-length packet transmission system, the synchronous packet forming section sets the value of all bits of the synchronous packet to 1, and sets all the values of the header of the fixed-length packet formed by the data packet forming section to 1. is 1, the data packet forming unit sets to 0 at least one bit of the error detection code for detecting an error in the header of the fixed-length packet. method. (2) A data packet forming unit that forms a fixed length packet consisting of a header, an error detection code, and information data, and a synchronization packet formation unit that forms a synchronization packet for establishing frame synchronization with the same fixed length as the fixed length packet. In the fixed-length packet transmission system comprising: If all of them are 0, the data packet forming unit sets at least one bit of the error detection code to 1 to detect an error in the header of the fixed-length packet. Synchronous method.