SU605325A1 - M-sequence synchronising method - Google Patents

Description

(54) METHOD FOR SYNCHRONIZING M-SEQUENCE

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The invention relates to radio engineering and can be used in radio receiving devices of broadband signals.

There is a known method for synchronizing the M-sequence, which consists in analyzing () the characters of the received M-sequence, where n is the number of information symbols, k is the number of check symbols, forming the reference M-sequence, determining the value of the cross-correlation function of the reference and received M- sequence and then comparing the obtained value of the cross-correlation function with a given threshold and changing the phase of the reference M-sequence 1.

However, in the known method, a large time of entry into synchronism.

The purpose of the invention is to reduce the time taken to synchronize.

To do this, in the method of synchronization of the M-sequence, which consists in analyzing () the characters of the received M-sequence, where n is the number of information symbols, k is the number of check symbols, forming the reference M-sequence, determining the value of the mutual correlation function of the reference and received M-sequence and with the subsequent comparison of the obtained value of the cross-correlation function with a given threshold and phase change of the reference M-sequence, before analyzing () the characters of the received M-sequence on the shaft n clock each

the symbol of the received M-sequence is compared with a predetermined threshold level, while the symbol of the received M-sequence that exceeds the predetermined threshold level is remembered, and the symbol that does not exceed the predetermined threshold level is reconstructed by modulo two two corresponding stored symbols of the received M -sequences, moreover, the reference M-sequence is formed by extracting n continuously the next characters of the received M-sequence, and on the interval of 5 cycles, where m is the number of groups of n characters, select any n continuously followed by each other characters of the received M-sequence, which form the reference M-sequence, the phase of which is combined with the phase of the received M-sequence.

The drawing shows a structural electrical circuit of the device implementing the method.

The device contains a threshold unit 1, a logic circuit 2, a switch 3 of the operating mode of the M-sequence generator, a shift register 4, an M-sequence generator 5, an adder b modulo two.

The device works as follows.

The received sequence is fed to the input of the threshold unit 1. Some of the characters that do not exceed the threshold are erased; the inputs of logic circuit 2 receive implementations that have values that exceed the threshold.

At the beginning of reception, the symbols exceeding the threshold pass through logic 2 to the input of the switch 3 of the generator operation modes.

The switch 3 in its initial state passes the sequence coming to it from logic circuit 2 to the input of the first bit of shift register 4, which enters the 5 M-sequence generator.

Simultaneously with the recording of the characters of the received sequence in the shift register 4 in the logic circuit, the bits of the register in which the information characters are written are fixed.

After the first n characters are received, logic circuit 2 is included in the operation of checking equations and restoring (determining) the values of the erased characters.

If the information symbol arrives from the threshold block 1 to the input of the logic circuit 2 and there is no fixed record in / C + 1-OM nor in the n-th bit, then the information in the shift register 4 is shifted, for the first time A symbol of information will be written, and logic circuit 2 will record the presence of a symbol in this bit.

If, at the same time as the threshold is exceeded (by the presence of the information symbol at the input of the logic circuit), the presence of information symbols is recorded in K + l-oM and n-th bits, then a recurrence equation connecting these symbols is checked. If the equation is not fulfilled, the reception of the character exceeding the threshold is not fixed and at the same time the presence of the received symbol is removed (after shifting the information according to the beat) in the | - | 2th digit of the 4 shift.

When the equation is executed, the reception of the symbol is fixed and its value is written to the 1st bit of the shift register 4.

If simultaneously with the presence of a symbol at the input of logic circuit 2, the presence of the received symbol in one of the bits of register 4 shift to + 1st, or nth is fixed, then write to the 1st bit of register 4 shift and simultaneous fixation in logic 2, the received information symbol. If, at the same time, the reception of a new symbol occurred in the presence of fixation of the received symbol of information in the nth digit of the de 4 register shift, then at the same time, a new (restored) symbol defined by the logic circuit was again written to the K + 2d digit of the register received and stored in the nth de reg register 4 shift the symbol value with simultaneous fixation by logic circuit 2 of the presence of reception of this symbol.

If the threshold is not exceeded and characters are present in the 4th and 4th bits of the 4th shift register, the value calculated by the adder 6 is fixed in the logic circuit 2 and, using switch 3, is recorded into the first bit of the 4th shift register.

Erasing a character is fixed in the case

when the threshold is not exceeded and the presence of an information symbol is not recorded in K + l and n-th bits, or the presence of a symbol in one of them is fixed. The threshold reception process continues.

until the logical scheme records the presence of the recorded values of the received symbols in all bits of the 4-shift register. After that, the logic circuit 2 at the control input 7 switches the switch 3 of the generator 5 operating mode, the switch disconnects the input 8 and connects the input 9 to the input of the 1st bit of the shift register 4. Generator 5 M-sequence goes

in the mode of formation of the local M-sequence. The M-sequence from the output of the adder 6 is fed to the logic circuit 2, where it is correlated for a given period of time with the received sequence received at the input 10 of the logic circuit 2.

If, during the analysis, the value of the mutual correlation function does not exceed the specified threshold, then logic circuit 2 at control input 7 switches switch 3 and again switches the device to the threshold reception mode.

If the threshold is exceeded, generator 5 will continue to form a local sequence, which is evidence of synchronism.

Claims (2)

1. The synchronization method of the M-sequence, which consists in analyzing (n + k) characters of the received M-sequence (where n is the number of information symbols, k is the number of check characters), forming the reference M.-sequence, determining the value of the cross-correlation function the reference and the received M-sequence and then comparing the obtained value of the cross-correlation function with a given threshold and changing the phase of the reference M-sequence, characterized in that, in order to reduce the time of entry into synchronism, red analysis () characters of the received M-sequence on the interval of n cycles each symbol of the received M-sequence is compared with the specified threshold level, while the symbol of the received M-sequence that exceeds the specified threshold level is memorized, and the character that does not exceed the specified threshold level is restored by modulo two two corresponding memorized characters of the received M-sequence; moreover, the reference M-sequence is formed by selecting n continuously following characters of the received M-sequence of 2. A method according to claim 1, characterized in that on the interval of the η-th cycles, where m is the number of groups of π symbols, select any η continuously following each other characters of the received M-sequence, which form the reference M- sequence, the phase of which is combined with the phase of the received M-sequence. Sources of information taken into account during the examination 1. Certificate of authorization number 356807, MKI N 04L 7/02, 1969.