KR102296343B1 - Demodulating method and demodulator using expansion of reference symbol - Google Patents

Abstract

According to the present invention, a demodulation method includes the steps of: a receiving step of receiving a signal coded with a bi-phase-space line or a bi-phase-mark; and a correlation operation step of calculating a correlation value of an extension signal and a signal extending the front and rear half periods of a period of a reference symbol for the correlation operation. According to the demodulation method according to the present invention, it is possible to expect a double performance improvement only by extending the reference symbol without changing a structure of the existing demodulator, and demodulation performance can be greatly improved only by changing a setting value through means such as firmware update according to configuration of hardware already implemented.

Description

DEMODULATING METHOD AND DEMODULATOR USING EXPANSION OF REFERENCE SYMBOL

The present invention relates to a demodulation method and a demodulation apparatus, and more particularly, to improve performance through extension of a reference symbol in the process of demodulating a coded signal having a characteristic that the phase is always inverted at a symbol boundary. It relates to a demodulation method and a demodulation apparatus.

In communication, the modulated wave changed according to the data signal is loaded on the carrier and transmitted, and the receiver takes the modulated wave from the high-frequency current and restores the original signal. This is called demodulation.

The demodulation method differs depending on the modulation method. In the case of amplitude modulation, a rectifier or other non-linear circuit is used. In the case of frequency modulation or phase modulation, demodulation is performed by combining a frequency discriminator and a demodulator during amplitude modulation.

1 is a block diagram illustrating a demodulator of a conventional technique. As shown in FIG. 1, the conventional demodulator is performed in such a way that an output decision is formed after correlating a received signal r(t) using a plurality of reference symbols. In general, the correlation operation using the reference symbol is performed on the region from the start point to the end point of one cycle of the symbol.

In the case of digital communication, if an error occurs, it may be impossible to acquire information due to fatal data damage. However, since all data of the digital signal are arranged in 1s and 0s, the recovery method is easier than in the analog case, and the methods are very diverse. By adding bits to correct the error, you can find the location of the error and correct the wrong 0s and 1s.

In the M-ary modulation scheme, if the number of states M is increased, the number of bits per symbol increases, so the transmission rate increases. Since a signal-to-noise ratio (SNR) must be increased in order to maintain a low bit error probability, the number of bits per symbol cannot be increased blindly.

In the digital modulation method, performance is evaluated by the probability that an error occurs in the bit determination of the receiving side. Instead of the average SNR, Eb/No, which is the SNR per bit, is used, and the bit error rate (BER) is used. The performance of the digital modulation method is mainly expressed as a BER-Eb/No graph representing the relationship between Eb/No and BER, which is called a BER curve.

2 shows a BER curve in a general modulation scheme. The BER curve shown in FIG. 2 is used to compare the performance of various digital modulation schemes, and it can be said that the modulation scheme with a low BER has better performance when the Eb/No of bits are the same, and when Eb/No is raised, BER is lowered. However, since more energy is consumed during transmission, there is a problem in that it is uneconomical.

In particular, FIG. 2A is a graph comparing BER performance of FM0 and Miller codes in an ideal additive white Gaussian noise (AWGN) and Rayleigh channel. It can be seen that when the signal-to-noise ratio is large, the BER in the AWGN channel decreases faster than in the Rayleigh channel. In AWGN, ^{an SNR of about 12 dB is required to maintain a 10 -3} bit error rate, and an SNR of about 25 dB is required on the Rayleigh channel when using FM0 encoding. In addition, it can be inferred that the BER decreases as the Miller subcarrier order increases, but it has a disadvantage in that the data rate decreases. In order to increase the performance of the demodulator, it is necessary to find a way to dramatically reduce the BER.

Korean Patent Publication No. 10-1512441 (Registered on Apr. 9, 2015)

It is an object of the present invention to provide a demodulation method and demodulation apparatus capable of improving performance without changing the structure of the prior art.

A demodulation method for achieving the above object, the receiving step of receiving a signal coded in a bi-phase space line (Bi-phase-space line) or bi-phase mark (Bi-phase-mark); and a correlation operation step of calculating a correlation value between an extension signal extending before and after half a period of a period of a reference symbol for correlation operation and the signal.

The method may further include determining a signal having the highest degree of correlation by comparing the first to nth correlation calculation results calculated in the correlation calculation step.

Also, the energy of the correlation operation result by the extension signal may correspond to twice the energy of the correlation operation value by the reference signal.

In addition, the integration period of the extension signal may correspond to twice the period of the reference signal.

On the other hand, the demodulation apparatus according to the present invention for achieving the above object is a receiver for receiving a signal; and a correlation calculator that calculates a correlation value between an extension signal extending before and after half a period of a period of a reference symbol for correlation calculation and the signal, wherein the correlation operator performs a correlation operation using the following equation carry out

[Equation]

(k is an integer, r(t) is the received signal, S _n (t) is the extended signal, and t is the time)

Also, the signal received by the receiver may be a signal coded with a bi-phase-space line or a bi-phase-mark.

The method may further include a determiner configured to determine a signal having the highest degree of correlation by comparing first to n-th operation result values calculated by the correlation calculator.

Also, the energy of the correlation calculation result by the extension signal may correspond to twice the energy of the correlation calculation value by the reference signal.

According to the demodulation apparatus and demodulation method according to the present invention, it is possible to expect double performance improvement only by extending the reference symbol without changing the structure of the existing demodulator, and through means such as firmware update according to the hardware configuration already implemented. Demodulation performance can be greatly improved only by changing the setting value.

1 is a block diagram illustrating a demodulator of a conventional technique.
2 shows a BER curve in a general modulation scheme.
3 is a diagram for explaining a signal used in a demodulation method and a demodulation apparatus according to the present invention.
4 is a view for explaining a signal applicable to a demodulation method and a demodulation apparatus according to the present invention.
5 is a diagram for explaining a demodulation method according to the present invention.
_{6 shows a first extension signal S 1} extended by using a schematic diagram of a pattern transition before and after the first symbol and signal characteristics.
_{7 shows a second extension signal S 2} extended by using a schematic diagram of a pattern transition before and after the second symbol and signal characteristics.
_{8 shows a third extended signal S 3} extended using a schematic diagram of pattern transition before and after the third symbol and signal characteristics.
_{9 shows a fourth extended signal S 4} extended by using a schematic diagram of pattern transition before and after the fourth symbol and signal characteristics.
10 is a block diagram showing the configuration of a demodulator according to the present invention.
11 is a graph showing the effect of the demodulation method according to the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0012] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS [0013] Reference is made to the accompanying drawings, which show by way of illustration specific embodiments in which the present invention may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the present invention. It should be understood that the various embodiments of the present invention are different but need not be mutually exclusive. For example, certain shapes, structures, and characteristics described herein may be embodied in other embodiments without departing from the spirit and scope of the invention with respect to one embodiment. In addition, it should be understood that the location or arrangement of individual components within each disclosed embodiment may be changed without departing from the spirit and scope of the present invention. Accordingly, the detailed description set forth below is not intended to be taken in a limiting sense, and the scope of the invention, if properly described, is limited only by the appended claims, along with all scope equivalents to those claimed. Like reference numerals in the drawings refer to the same or similar functions throughout the various aspects.

3 is a diagram for explaining a signal used in a demodulation method and a demodulation apparatus according to the present invention. The signal shown in FIG. 3 exemplifies a Bi-phase-space line coded signal. 3, an FM0 basis function and an FM0 generator state diagram are shown in the upper part of FIG. 3, and an FM0 symbol and an FM0 sequence are shown in the lower part.

Bi-phase space coding refers to coding in which one transition is made for one bit when the signal to be modulated is 0, and when the signal to be modulated is 1, two transitions are made during one bit.

Referring to the FM0 sequence of FIG. 3 , when the biphase space line coding signal is 00, 01, 10, or 11, the phase is always inverted at the boundary of the symbol. In other words, it has a characteristic that the phase is inverted in all of 0→0, 0→1, 1→0, and 1→1.

4 is a view for explaining a signal applicable to a demodulation method and a demodulation apparatus according to the present invention. Like the bi-phase-space line coded signal described with reference to FIG. 3 , the bi-phase mark coded signal also has a characteristic that the phase is always inverted at the boundary of the symbol.

4, when the data sequence is 1100100011, in all of 1→1, 1→0, 0→0, 0→1, 1→0, 0→0, 0→0, 0→1, and 1→1 phase is reversed. This is based on the characteristics of the symbols of a bi-phase-space line coded signal and a bi-phase mark coded signal, and the present invention provides a bi-phase-space line (Bi-phase-space) line. line) A method and apparatus for improving demodulation performance by doubling the amount of energy used for symbol decision when using a coded signal and a bi-phase mark coded signal as a received signal. suggest

5 is a diagram for explaining a demodulation method according to the present invention. First, a signal r(t) is received through an antenna. As mentioned above, the received signal r(t) is preferably a signal coded with a bi-phase-space line or a bi-phase-mark.

Thereafter, a correlation value for the received signal is calculated. At this time, in the present invention, the first to nth reference signals (s ₁ (t) to s _n (t)) have extended signals S ₁ (t) to S _n (t)) and A correlation operation is performed to calculate a correlation value of the received signal. The first to nth reference signals s ₁ (t) to s _n (t) (demodulation reference signal, reference function) are integrated after being multiplied with the received signal by a multiplier, and the integration period is always extended to 2T. That is, the integration period of the extension signals S ₁ (t) to S _n (t) corresponds to twice the period of the _{reference signals s 1} (t) to s _{n (t).} This is because, instead of the reference signals s ₁ (t) to s _n (t), the extended signals S ₁ (t) to S _n (t) having an extended front and rear half period are used.

_{Specifically, in the present invention, the correlation operation is performed on the extension signals S 1} (t) to S _n (t), the region of which is extended from the previous half cycle to the subsequent half cycle of the cycle of the first to nth reference signals, and the bi-phase space This is achieved by correlating a received signal coded with a line (Bi-phase-space line) or a bi-phase-mark (Bi-phase-mark). In this way, the amount of energy used for symbol decision is doubled.

In general, the energy of a signal can be defined as in Equation 1 below. At this time, if the signal function is a square wave having a maximum value of a, it has an energy of ^{a 2 T.}

는 신호 함수의 에너지, t는 시간, T는 주기)(g(t) is the pulse function,

is the energy of the signal function, t is time, T is period)

When correlation is taken using the extension signal Sn extended from the previous half cycle to the next half cycle as in the present invention, instead of the conventional correlation using a reference signal having one cycle, the cycle is doubled (2T). As it expands, the amount of energy is also doubled.

As a result, the energy of the correlation operation result by the _{extension signals S 1} to S _n corresponds to twice the energy of the correlation operation value by _{the first to n-th reference signals s 1} to s _{n before the expansion.} do. In this case, the sample output time may also be extended to 2 kT (refer to FIG. 5) in the present invention, compared to the kT time of the prior art (refer to FIG. 1).

_{6 shows a first extension signal S 1} extended by using a schematic diagram of a pattern transition before and after the first symbol and signal characteristics.

As shown in FIG. 6 , when there are a second symbol and a third symbol before and after the first symbol, respectively, when there are a second symbol and a fourth symbol before and after the first symbol, respectively, a fourth symbol before and after the first symbol When there is a symbol and a third symbol, in both cases where there is a fourth symbol and a fourth symbol before and after the first symbol, it is represented by _{the first extension signal S 1 having the same waveform even when the front and rear half-cycles are extended} can be That is, if the period of the symbol before the extension is T, the first extension signal S ₁ may be extended by a first half period (-1/2T) and a second half period (1/2T).

_{7 shows a second extension signal S 2} extended by using a schematic diagram of a pattern transition before and after the second symbol and signal characteristics.

As shown in FIG. 7 , when there is a second symbol and a first symbol before and after the second symbol, respectively, when there are a second symbol and a second symbol before and after the second symbol, respectively, a fourth symbol before and after the second symbol, respectively When there is a symbol and a first symbol, in both cases where there is a fourth symbol and a second symbol before and after the second symbol, it is represented by _{the second extension signal S 2 having the same waveform even when the front and rear half-cycles are extended} can be That is, if the period of the symbol before the extension is T, the second extension signal S ₂ may be extended by a first half period (-1/2T) and a second half period (1/2T).

_{8 shows a third extended signal S 3} extended using a schematic diagram of pattern transition before and after the third symbol and signal characteristics.

As shown in FIG. 8 , when there is a first symbol and a third symbol before and after the third symbol, respectively, when there is a first symbol and a third symbol before and after the third symbol, respectively, a third symbol before and after the third symbol When there is a symbol and a third symbol, in both cases where there is a third symbol and a third symbol before and after the third symbol, it is represented _{by a third extension signal (S 3 ) having the same waveform even when the front and rear half-cycles are extended} can be That is, if the period of the symbol before the extension is T, the third extension signal S ₃ may be extended by a first half period (-1/2T) and a second half period (1/2T).

_{9 shows a fourth extended signal S 4} extended by using a schematic diagram of pattern transition before and after the fourth symbol and signal characteristics.

As shown in FIG. 9 , when there is a first symbol and a first symbol before and after the fourth symbol, respectively, when there is a first symbol and a second symbol before and after the fourth symbol, respectively, a third symbol before and after the fourth symbol When there is a symbol and a first symbol, in both cases where there is a third symbol and a second symbol before and after the fourth symbol, it is represented _{by a fourth extension signal S 4 having the same waveform even when the front and rear half-cycles are extended} can be That is, if the period of the symbol before the extension is T, the fourth extension signal S ₄ may be extended by a first half period (-1/2T) and a second half period (1/2T).

This is a bi-phase-space line coding signal or a bi-phase mark (Bi-phase-space line) coded signal having a characteristic that the phase of the received signal used in the demodulation method and the demodulation apparatus according to the present invention is always inverted at the boundary of the symbol. phase mark) because it is a coded signal.

10 is a block diagram showing the configuration of a demodulator according to the present invention. As shown in FIG. 10 , the demodulator 100 includes a receiver 110 , a correlator 120 , and a determiner 130 .

The receiver 110 receives a signal coded with a bi-phase-space line or a bi-phase-mark.

The correlator correlates an extension signal obtained by extending the front and rear half-cycles of the first to n-th reference signals with respect to the signal. In this case, the energy of the correlation calculation result by the extension signal may correspond to twice the energy of the correlation calculation value by the first to nth reference signals. Specifically, the correlation operator performs a correlation operation using Equation 2 below. The integral section of the extended signal is increased to 2T. That is, the integral section of the extended signal is extended from the previous half cycle of one cycle to the next half cycle. Accordingly, as described above, the energy of a signal used for symbol decision is doubled, so that demodulation performance can be improved.

(k is an integer, r(t) is the received signal, S _n (t) is the extended signal, and t is the time)

The determiner 130 compares the first to nth operation result values calculated by the correlation operator 120 to determine the signal having the highest correlation.

11 is a diagram showing the effect of the demodulation method according to the present invention. 11 is a graph illustrating a result of performing Monte Carlo simulation on random bits coded with bi-phase space lines.

11, referring to the BER curves of the conventional demodulator and the demodulator according to the present invention, it was confirmed that the SNR of approximately 3 dB was improved based on ^{BER 10 -3, which} , proves that the demodulation method according to the present invention achieves a superior improvement in demodulation performance compared to the prior art.

According to the demodulation apparatus and demodulation method according to the present invention, it is possible to expect double performance improvement only by extending the reference symbol without changing the structure of the existing demodulator, and through means such as firmware update according to the hardware configuration already implemented. Demodulation performance can be greatly improved only by changing the setting value.

Features, structures, effects, etc. described in the above embodiments are included in one embodiment of the present invention, and are not necessarily limited to one embodiment. Furthermore, features, structures, effects, etc. illustrated in each embodiment can be combined or modified with respect to other embodiments by those of ordinary skill in the art to which the embodiments belong. Accordingly, the contents related to such combinations and modifications should be interpreted as being included in the scope of the present invention.

In addition, although the embodiment has been mainly described in the above, this is only an example and does not limit the present invention, and those of ordinary skill in the art to which the present invention pertains to the above in the range that does not depart from the essential characteristics of the present embodiment. It will be appreciated that various modifications and applications not illustrated are possible. For example, each component specifically shown in the embodiment can be implemented with modification. And differences related to such modifications and applications should be construed as being included in the scope of the present invention defined in the appended claims.

100: demodulator
110: receiver
120: correlation operator
130: crystallizer

Claims (8)

a receiving step of receiving a signal coded with a bi-phase-space line or a bi-phase-mark; and
A correlation operation step of calculating the correlation value of the signal and the extension signal extending the front and rear half periods of the period of the reference signal for the correlation operation;
The extension signal has the same waveform as the reference signal. According to claim 1,
and determining a signal having the highest degree of correlation by comparing first to n-th correlation calculation result values calculated in the correlation calculation step. According to claim 1,
The energy of the correlation operation result by the extension signal corresponds to twice the energy of the correlation operation value by the reference signal. According to claim 1,
The integration period of the extension signal corresponds to twice the period of the reference signal. a receiver for receiving a signal;
Including; and a correlation calculator for calculating the correlation value of the extension signal and the signal extending the front and rear half-cycles of the period of the reference signal (reference symbol) for correlation calculation;
The correlation calculator performs a correlation operation using the following equation,
The signal received by the receiver is a signal coded with a bi-phase-space line or a bi-phase-mark,
The extension signal has the same waveform as the reference signal.
[Equation]

(k is an integer, r(t) is the received signal, S _n (t) is the extended signal, and t is the time) delete 6. The method of claim 5,
and a determiner configured to determine a signal having the highest degree of correlation by comparing first to n-th operation result values calculated by the correlation calculator. 6. The method of claim 5,
The energy of the correlation calculation result by the extension signal corresponds to twice the energy of the correlation calculation value by the reference signal.

Images