JPH0318141A - Synchronization method in spread spectrum communication - Google Patents

Abstract

PURPOSE:To shorten a communication time and to improve reliability put on a line by reducing the transmission time of a preamble to a prescribed value when no error exists, and extending the transmission time when the error exists. CONSTITUTION:The reception signal of an antenna 1 is demodulated with a receiver 2, and error detection is performed at a detection circuit 4 by utilizing an error correction code. A detection result is supplied to a microprocessor 3 and an error counter circuit 5 as error status. When the value exceeds the prescribed number of count of the error, a preamble length change instruction is issued to the processor 3. The processor 3 changes a transmission protocol, and transmission data in which preamble length is changed is transmitted via a transmitter 6. At such a case, the transmission time of the premable is reduced to the prescribed value, and that time of the preamble is extended until the error is eliminated when the error exists.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field J This invention relates to a synchronization method for ensuring synchronization of spectrum spreading communications used in wireless communications. [Prior Art] Spread spectrum communication is a communication method that has been researched in recent years.This is a method in which a signal modulated using a normal method is further spread over a wide band using a spreading code for communication. ．． When converting this signal into fst key, the receiving side generates the same spreading code as the spread code 5 generated on the transmitting side.
At this time, it is necessary to synchronize the spreading codes on both the transmitting and receiving sides.6 Normally, for this synchronization, special data called a synchronization preamble is added before the transmitted data to facilitate synchronization acquisition. ．． This synchronization preamble is transmitted for a sufficiently long time compared to the time required by the receiver to acquire synchronization, ensuring reliable synchronization. [Problem to be solved by the invention] However, if the time to transmit the preamble is longer than necessary, redundancy increases and unnecessary waiting time occurs, so the preamble time must be set to an optimal value. However, this optimal time varies depending on communication distance and noise conditions, and cannot be determined uniformly. For this reason, in the past, emphasis was placed on synchronization acquisition and a long time was set, which resulted in wasted waiting time when communication conditions were good.However, in preparation for when communication conditions deteriorate, this time was I couldn't make it shorter. [Hands-on to solve the problem] In order to solve this problem, this invention shortens the transmission time of the preamble when there is no error, and extends the transmission time of the preamble when there is an error. This is what I did.

[Operation] When an error occurs, the preamble transmission time is extended by a predetermined value, and this time extension continues until the error disappears. On the other hand, when there is no error, the flow of the brieample (g
The time is gradually reduced until it reaches a certain value. [Embodiment] FIG. 1 is a diagram for explaining an embodiment of the present invention, and assumes 1:1 communication as an example. There are two transmitters, one is A. The @ side is called B, and they communicate with each other. First, side A sends a message, and when B receives it,
The B side notifies the AfllN of the presence or absence of data errors (determination of errors is done using a commonly used error correction code).The first transmission was sent with a preamble of 500 ms, but when the B side received it, an error occurred. Since there was no error, A(ll) is notified of this fact. At this time, the A side counts if there is no error and sets the count to 1. If there is no error even if the 500ms preamble is sent from the A side again, On the A side, the count without error becomes 2. In this example, when the count reaches 2, the preamble transmission time is shortened by 10%, the transmission time is set to 450ms, and the results counted so far are reset. do.

The third time is 450, which is the preamble transmission time set first.
ms, and if there is no error at this time, the A side sets the count to l. Preamble for the 4th time too 4 5 0
ms is transmitted, and if there is no error at this time, the All count becomes 2, and in the fifth transmission, the preamble transmission time is further shortened by 10% to 400 ms, and the counter is reset.

If an error occurs in reception on the B side, this will be reported to the A side and a retransmission request will be made. Therefore, the A side sets the count to 1 and retransmits the 5th transmission content with an all-round length of 400 mS. At this time, if an error is detected in the B measurement, a retransmission request is made to the A side again. As a result, the count on the A side becomes 2, so the preamble is set to 10.
% and resend the fifth transmission for 450ms. If an error does not occur here, set that time and perform communication for a certain number of times in a row (for example, 30
Once the communication is completed without errors, the operation to shorten the preamble begins again. By configuring synchronization between A and B in this way, the optimal time is set. Figure 2 is a block diagram of the circuit that performs this operation. The signal received by the antenna 1 is demodulated by the reception [l2], and an error is detected by using the error correction code used in the error detection circuit 4. This result is supplied as an error status to the microprocessor 3 and also to the error count circuit 5. When a predetermined error count is exceeded, a preamble length change command is issued to the microprocessor 3. In response to this, the microprocessor 3 changes the transmission protocol using software or the like, and the transmission data with the changed preamble length is supplied to the transmitter 6 and transmitted. [Effects of the Invention] As explained above, in this invention, when there is no error, the preamble transmission time is shortened to a predetermined value, and when there is an error, the preamble transmission time is extended until the error disappears. , the preamble transmission time is determined according to the communication condition, and the communication time is reduced.
It also has the effect of improving line reliability.

[Brief explanation of the drawing]

FIG. 1 is a diagram for explaining this invention, and FIG. 2 is a block diagram showing an embodiment of this invention. 2... Receiver, 3... Microprocessor, 4... Error detection circuit, 5... Error count circuit, 6 - Transmitter.

Claims (1)

[Claims] In a synchronization method in spread spectrum communication that secures synchronization using a synchronization preamble when communicating in both directions, the synchronization preamble transmission time is shortened when there is no error, and the synchronization preamble transmission time is shortened when there is an error. A synchronization method in spread spectrum communication characterized by extending the .