JPS6041832A - Arq system - Google Patents

Abstract

PURPOSE:To attain retransmission request in block unit or bit unit by applying decoding of data by means of the maximum likelihood method at the data reception side and utilizing a likelihood function or a likelihood function difference calculated in the decoding as the decision of the retransmission request. CONSTITUTION:A signal transmitted from a data transmitter 4 is received by a receiver 6 and given to a maximum likelihood decoder 7 of the next stage at the reception side. The maximum likelihood decoder 7 operates the likelihood function based on a prescribed formula, compares the level and outputs the largest likelihood function among the likelihood functions and a data corresponding thereto to a deciding device 8. The device 8 compares the likelihood function outputted from the maximum likelihood decoder 7 with a predetermined deciding level. When the inputted likelihood function is larger than the deciding level in this case, the inputted data is stored in a prescribe address of a data buffer 9, and when the inputted data is smaller than the deciding level, the address of the inputted data is transmitted to the data transmission side via a transmitter 10 as a retransmission request signal.

Description

DETAILED DESCRIPTION OF THE INVENTION According to the present invention, input data is encoded with an error detection code on the data transmitting side and then transmitted, data errors are detected on the data receiving side, and the data at the location of the detected error is A RQ ('au
This relates to the tomaticrequest) method.

This type of conventional method encodes input data with an error detection code such as a block code, detects errors on the data receiving side, and requests the data transmitting side to retransmit the block in which the error was detected. Therefore, there are problems such as it is impossible to request retransmission for errors that exceed the detection ability of the error detection code, and retransmission requests are made in block units, making it difficult to request retransmission in bit units. Ta.

In view of the above-mentioned circumstances, the present invention performs maximum likelihood decoding of data using a maximum likelihood decoding method on the data receiving side, and determines a retransmission request based on the likelihood function or likelihood function difference calculated during the decoding. Therefore, it is an object of the present invention to provide an ARQ method that solves the problems of the conventional method.

The maximum likelihood decoding method adopted in the present invention is a type of so-called error correction method.To explain its basic principle, first, input data is encoded using a convolutional code etc. on the data transmitting side, and this is used for data reception. Send to the side. On the data receiving side, a likelihood function LF expressed by the following equation is calculated.

LF=P(1'1A)=7(yl l a: ) (1
) Here, Y is the received data sequence vector Y-(Jl
+3'21..., Vi...)+A is the first output input data sequence vector determined by the encoder provided on the data transmitting side, and A== (a:, αyu,...α)...
・).

In other words, the likelihood function of Equation 11 is calculated for all received data sequences determined by the encoder provided on the data transmitting side, and the calculated likelihood function LF and all of the corresponding received data sequences are calculated. Store it on the data receiving side.

After calculation of a certain length, the received data sequence corresponding to the largest likelihood function LFK among the stored likelihood functions LF is sequentially output as demodulated data. In other words, the maximum likelihood decoding method is a method in which the data receiving side selects the data sequence that is considered to be closest to the transmitted data sequence. It is clear from the above tII formula that the value becomes smaller if . From this, it can be seen that the likelihood function is a function representing the decoding quality of received data. By applying the properties of such a likelihood function, it becomes possible to request retransmission for all kinds of errors without being limited by the detection ability of the error detection code, and it becomes possible to request retransmission not only in units of blocks but also in units of bits. The present invention is characterized in that retransmission requests are determined by applying the properties of the likelihood function.

An embodiment of the present invention will be described in detail below with reference to the drawings.

-1 data buffer 1vC input data on data sending side
Store and add an address to all data here,
Thereafter, the stored data is sequentially supplied to the encoder 3 through the retransmission request determiner 2 in address order. The encoder 3 then encodes the signal using a convolutional code or the like, and sends it to the transmitter 4 for transmission. On the data receiving side, a receiver 6 receives the signal transmitted from the transmitter 4 and supplies it to a maximum likelihood decoder 7 at the first stage.

This maximum likelihood decoder 7 uses the FII formula to obtain a likelihood function LF7.
After calculating, a magnitude comparison is performed and the largest likelihood function among the likelihood functions and the data corresponding thereto are output to the determiner 8. This determiner 8 compares the likelihood function output from the maximum likelihood decoder 7 with a predetermined determination level. In this case, if the input likelihood function is larger than the judgment level, the input data is stored in a predetermined address of the data buffer 9, and if it is smaller than the judgment level 2, the address of the input data is retransmitted. Data is transmitted and received as a request signal via the transmitter 1o, and the retransmission request determiner 2
The data stored in the data buffer 1 at the address sent is read out and output to the encoder 3. If there is no retransmission request, the manual data is sequentially output from the data buffer 1 to the encoder 3 via the retransmission request determiner 2, and the same operation is repeated until all input data is output from the data buffer 1. be.

Note that since the likelihood function LF calculated by the maximum likelihood decoder 7 is calculated for each demodulated bit, a retransmission request can be made bit by bit. Furthermore, when making a retransmission request in units of blocks, it is preferable to calculate the average value of the likelihood functions included in the block and make a determination based on the average value of the likelihood functions included in the block. Furthermore, in the likelihood function sequence calculated by the equation 1 above, the difference between the likelihood function that is the first dog and the likelihood function that is the second dog has the property that the more errors there are, the smaller it becomes. Therefore, if this likelihood function difference is output from the maximum likelihood decoder 7 to the determiner 8, a retransmission request can be determined based on the likelihood function difference.

As detailed above, the present invention decodes data using the maximum likelihood decoding method on the data receiving side, and uses the prior function or the prior function difference calculated during decoding to determine a retransmission request. Therefore, retransmission requests can be made on a block-by-block or bit-by-bit basis without being limited by error detection capability.

This is highly effective in expanding the range of error control and improving decoding quality.

[Brief explanation of the drawing]

The drawing is a block diagram showing an embodiment of the ARQ system according to the present invention. ], 9...Data buffer, 2...Retransmission request determination patent applicant Director of Technology Research Headquarters, Defense Agency Patent applicant Japan Radio Co., Ltd. (word)

Claims (1)

[Claims] The data transmitting side encodes input data, the data receiving side detects errors in the data, and in response to the errors, requests the data transmitting side to retransmit the data. In a method in which data that has been requested for retransmission is sent again to the data receiving side to correct data errors. AR characterized in that the data receiving side performs maximum likelihood decoding of data using a maximum likelihood decoding method, and the retransmission request is determined based on a likelihood function or a likelihood function difference calculated during the decoding.
Q method.