KR101822755B1 - System and Method for increasing Anti-Jamming and Low Probability of Intercept for Wireless Communication Systems - Google Patents

Abstract

The present invention relates to wireless communication system technology and, more specifically, relates to anti-jamming and low probability of intercept (AJ/LPI) increase system and method to improve AJ/LPI performance. According to the present invention, when assuming that a hostile army has a receiver and transmitter based on chirp to intercept or disturb signals of a friendly army, it is possible to increase AJ/LPI performance in consideration of chirp rate sensitivity of a chirp spread spectrum (CSS) system.

Description

Technical Field [0001] The present invention relates to an AJ / LPI enhancement system and method for a wireless communication system,

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to wireless communication system technology, and more particularly, to an AJ / LPI enhancement system and method capable of improving Anti-Jamming and Low Probability of Intercept (AJ / LPI) performance for a wireless communication system.

동안 각 사용자에게 서로 다른 처프율(Chirp Rate)을 할당하는 기법이다. 이를 개념적으로 보여주는 도면이 도 1에 도시된다. 도 1에 도시된 바와 같이, 총 5명의 사용자가 있을 때, 최대 확산 대역

내에서 각 사용자에게 서로 다른 처프율(Chirp Rate)을 할당함으로써 전체 시스템의 전송률을 높일 수 있다. In general, a multiple single linear chirp technique for multiple access is known. This multi-linear linear chirp technique uses a chirp sweeping time

While assigning different chirp rates to each user. A diagram showing this conceptually is shown in Fig. As shown in Fig. 1, when there are a total of five users,

It is possible to increase the transmission rate of the entire system by assigning a different chirp rate to each user.

However, in the case of the multiple single linear chirp technique, a fairness problem may occur due to the allocation of different bandwidths to each user.

를 균일하게 분할하여 각 사용자에게 서로 다른 Chirp Rate를 할당하는 기법이다. In addition, a multiple multi-linear chirp technique is generally known for multiple access. This multiple multi-linear chirp technique is based on the sweeping time of the chirp

And assign different chirp rates to each user.

(여기서는 초기 주파수

가 1kHz이고, 2.5kHz까지 Sweeping 하는 것이기 때문에 1.5kHz임)를 얻기 위해 스위핑(Sweeping) 시간

를 균일하게 분할하여 각 사용자에게 서로 다른 처프율(Chirp Rate)을 할당한다.As shown in FIG. 2, when there are eight users in total, the multiple multi-linear chirp

(Here, the initial frequency

Is 1.5 kHz because it is 1 kHz and sweeping to 2.5 kHz), the sweeping time

And allocates a different chirp rate to each user.

In addition, a Frequency-Hopped Multi-user Chirp Modulation (FH / M-CM) technique is generally known. Frequency-Hopping Spread Spectrum (FH / SS) technology is robust to interference and multipath attenuation because of its large processing gain. The purpose of the FH / M-CM technique is to improve the transmission performance of the system in the multipath attenuation channel by applying frequency-hopping (FH) to the Multi-user Chirp Modulation (M-CM) Thereby reducing multiple-access interference (MAI) between users. A PN (Pseudo Noise) sequence is used to hop the center frequency of the FH / M-CM in the same manner as the general FH technique.

) PN 코드 길이

인 [110111101011101]을 생성한다. 주파수(Frequency)가 호핑(Hopping)될 수 있는 개수

이 8 (0~7)이기 때문에 호핑(Hopping) 주파수를 결정하기 위한 PN 코드는 각 호핑(Hopping) 시간마다 3비트씩 필요하다. 3비트의 PN 코드마다 해당 Frequency를 이용하는데 각 사용자마다 MLC의 처프율(Chirp Rate)이 결정되어 있고, 각 사용자가 "1" 비트를 전송할 때는 업-처프(Up-Chirp), "0" 비트를 전송할 때는 다운-처프(Down-Chirp)를 이용한다.Figure 3 shows an example of a diagram of an FH / M-CM signal using one PN sequence. A total of 7 users coexist, and each user transmits 5 bits. To generate a PN sequence for determining the Hopping pattern of the FH, a Stage of the Code Generator

) PN code length

Quot; 110111101011101 ". The number of times the frequency can be hopped

Since this is 8 (0 to 7), the PN code for determining the hopping frequency is 3 bits for each hopping time. The chirp rate of the MLC is determined for each user using the corresponding frequency for each 3-bit PN code. When each user transmits a "1" bit, the up-chirp, A down-chirp is used.

On the other hand, an FH / M-CM multiple access technique using two PN sequences is known. Figure 4 shows an example of a diagram of an FH / M-CM signal using two PN sequences. A total of two users coexist, and each user transmits 5 bits.

Since multiple users coexist, the PN code must be set differently for each user. In the example of FIG. 4, the PN code of User A is set to [110111101011101] and the PN code of User B is set to [011111001011110].

이 8 (0~7)이기 때문에 Hopping 주파수를 결정하기 위한 PN 코드는 각 Hopping 시간마다 3비트씩 필요하다. 3비트의 PN 코드마다 해당 Frequency를 이용하는데 각 사용자마다 MLC의 처프율(Chirp Rate)이 결정되어 있고, 각 사용자가 "1" 비트를 전송할 때는 업-처프(Up-Chirp), "0" 비트를 전송할 때는 다운-처프(Down-Chirp)를 이용한다. The number of frequencies that can be hopped in the same way

Since this is 8 (0 to 7), the PN code for determining the hopping frequency is 3 bits every hopping time. The chirp rate of the MLC is determined for each user using the corresponding frequency for each 3-bit PN code. When each user transmits a "1" bit, the up-chirp, A down-chirp is used.

Since the PN codes are assigned to one PN code for each user (two PN codes in total in the system), the PN codes are the same in the second (transmission bits are the same, both are Up-Chirp but different in Chirp Rate) Correlation will occur at different transmission bits (the direction of the chirp is different and the chirp rate is different because of different transmission bits). However, the transmission performance can be improved because the effect is small and the patterns are different.

와 확산 대역

를 파악할 수 있게 된다. 이 때 전송된 처프(Chirp) 신호에 정합되는 Chirp 신호를 역으로 생성하여 신호를 수신할 수 있음으로써 CSS(Chirp Spread Spectrum) 시스템의 AJ(Anti-Jamming)/LPI(Low Probability of Intercept) 성능이 저하될 수 있다. However, in the case of a multiple single linear chirp scheme for multiple access, if a single linear chirp rate is assigned to each user, in the worst case, the interceptor Interceptor) determines the center frequency of a particular chirp signal

And spread spectrum

. (Chirp Spread Spectrum) system's anti-jamming / LPI (Low Probability of Intercept) performance can be achieved by generating a chirp signal that is matched to the transmitted chirp signal and receiving the signal. Can be degraded.

Here, considering the worst case in the case of a friend, the definition of LPI may include the concept of Low Probability of Detection (LPD), in which a friend's signal is detected by the enemy's interceptor. However, if the LPD and LPI are strictly divided, the enemy group can detect the allied signal, extract the parameters of the allied signal, and demodulate through the LPI.

Therefore, it differs from the general LPD concept. Therefore, a technology capable of improving AJ / LPI performance is required.

In the case of Frequency-Hopped Multi-user Chirp Modulation (FH / M-CM) technology, since chirp is fixedly assigned to each user, AJ / LPI performance may be deteriorated have.

1. Korean Patent Publication No. 10-2014-0025264 (entitled " Training sequence and channel estimation method for spread spectrum based system "

1. Kang, Kyung-Min et al., "Improvement of Fairness of Wireless Mesh Network through Traffic Shaping", Proceedings of KISEM, 2008.11, p785-788 2. "Performance Analysis of LPI and AJ in Chirp Method", Journal of Korea Institute of Military Science and Technology, Vol. 5 No. 1, pp.119-126

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems,

The object of the present invention is to provide a system and method for increasing AJ / LPI (Anti-Jamming and Low Probability of Intercept) which can not accurately demodulate even if a mismatch is detected in the case of enemy forces.

It is another object of the present invention to provide an AJ / LPI enhancement system and method for a wireless communication system in which signal transmission is less intercepted for an enemy group while improving transmission performance of a friend group.

In order to achieve the above-mentioned object, the present invention provides an anti-jamming and low-probability (AJ / LPI) algorithm for generating a chirp mismatch in an enemy receiver so that an enemy group can not accurately demodulate a chirp signal of Intercept < / RTI >

The AJ / LPI (Anti-Jamming and Low Probability of Intercept)

An AJ / LPI (Anti-Jamming and Low Probability of Intercept) enhancement system for a wireless communication system,

A modulator for modulating a received signal to generate a modulated signal;

A spreader for generating a first chirp signal by applying a first chirp rate pattern to the modulated signal;

A jamming adder for adding a jamming signal to the first chirp signal to generate a jamming output signal;

A despreader for generating a second chirp signal by applying a second chatter rate pattern to the jamming output signal;

A demodulator for demodulating the second chirp signal to generate a demodulation signal;

An integrator for integrating the demodulated signal to generate a final output signal;

A determining unit determining a signal to be transmitted using the final output signal; And

And a cull rate generating module for generating the first cull rate pattern and the second cull rate pattern.

In this case, the coding rate generation module may include a PN sequence generator for generating a PN (pseudo noise) sequence and a coding rate pattern generator for generating various coding rates according to the PN sequence.

The first cull pattern or the second cull pattern may be formed by dividing a specific time in advance.

In addition, the first cull pattern or the second cull pattern may be divided into two distinct portions according to the PN sequence.

The first cull pattern pattern or the second cull pattern pattern may be divided into quadrants, and the four patterns are transmitted according to the combination of the PN sequences.

The first chirp signal and the second chirp signal may be SLC (Single Linear Chirp) or MLC (Multiple Linear Chirp).

The chirp rate of the front chirp and the back chirp of the MLC is different from the chirp rate of the front chirp and the back chirp of the SLC . ≪ / RTI >

시간까지

MHz 대역폭을 사용하고, PN 시퀀스가 0일 때에는

시간까지

MHz 대역폭(여기서,

는 스위핑 시간을 나타내고,

과

는 각 처프의 대역폭을 나타낸다)을 사용한 것을 특징으로 할 수 있다.Further, when the PN sequence of the MLC is 1

By time

MHz bandwidth, and when the PN sequence is 0

By time

MHz bandwidth,

Represents the sweep time,

and

Represents the bandwidth of each chirp).

On the other hand, another embodiment of the present invention is an AJ / LPI (Anti-Jamming and Low Probability of Intercept) enhancement method for a wireless communication system, comprising: (a) modulating a received signal to generate a modulated signal step; (b) a diffuser applying a first chirp rate pattern to the modulated signal to generate a first chirp signal; (c) adding a jamming signal to the first chirp signal to generate a jamming output signal; (d) a despreader applying a second chatter rate pattern to the jamming output signal to generate a second chirp signal; (e) demodulating the second chirp signal to generate a demodulation signal; (f) integrating the demodulation signal by an integrator to generate a final output signal; And (g) determining a signal to be transmitted using the final output signal, wherein the step (b) and the step (d) comprise the steps of: And generating a second coding rate pattern based on the first coding rate and the second coding rate.

According to the present invention, considering the chirp rate sensitivity of the CSS (Chirp Spread Spectrum) system, assuming that the enemy unit has a receiver and a transmitter based on a chirp for intercepting or disturbing a friend's signal Thereby increasing the AJ / LPI (Anti-Jamming and Low Probability of Intercept) performance.

As another effect of the present invention, it can be seen from the simulation results that if the chirp rate and pattern matching the proposed technique are not known, it can be confirmed that the enemy army can not water the friend's signal .

Another advantage of the present invention is that transmission performance can be guaranteed because the enemy group can not generate the same chirp rate as the enemy group and can not be disturbed.

In addition, another advantage of the present invention is that it is easy to apply to a chirp spread spectrum direct modulation (CSS-DM) transmission technique using a chirp as a spreading code.

FIG. 1 is a conceptual diagram showing a method of allocating a chirp rate according to a general multiple single linear chirp technique.
FIG. 2 is a conceptual diagram showing a method of assigning a chirp rate according to a general multi-linear chirp technique.
3 is a conceptual diagram showing an example of a diagram of an FH / M-CM signal using a general PN (Pseudo Noise) sequence.
FIG. 4 is a conceptual diagram showing an example of a diagram of a frequency-hopped / multi-user chirp modulation (FH / M-CM) signal using two general PN sequences.
5 is a graph showing an example of a PSD (Power Spectral Density) that can be detected by a general interceptor.
FIG. 6 is a block diagram of an anti-jamming and low probability of intercept (AJ / LPI) enhancement system 600 for a wireless communication system according to an embodiment of the present invention.
FIG. 7 is a graph illustrating a time-frequency relationship between a chirp signal transmitted from a local transmitter and a chirp signal used for demodulating in an enemy's interceptor according to an exemplary embodiment of the present invention.
8 is a graph showing two chirp rate patterns 810 according to PN (Pseudo Noise) and four chirp rate patterns 820 according to PN (pseudo noise).
FIG. 9 is a graph showing time-frequency characteristics when a general SLC (Single Linear Chirp) and an MLC (Multiple Linear Chirp) have the same sampling rate.
10 is a graph showing chirp waveform over time when the general SLC and MLC have the same chirp rate.
11 is a graph showing the PSD (Power Spectral Density) of SLC (Single Linear Chirp) and MLC (Multiple Linear Chirp) when the general SLC and MLC have the same sampling rate.
12 is a graph showing cross correlation characteristics when the general SLC and MLC have the same culling rate.
FIG. 13 is a graph showing time-frequency characteristics when the front chirp rate according to an embodiment of the present invention is smaller than the back chirp rate.
14 is a graph showing a chirp waveform over time when the front culling rate according to an embodiment of the present invention is smaller than the backing rate.
15 is a graph showing the PSD (Power Spectral Density) of SLC and MLC when the front culling rate according to an embodiment of the present invention is smaller than the backing rate.
16 is a graph showing cross-correlation characteristics when the front culling rate according to an embodiment of the present invention is smaller than the backing rate.
17 is a graph showing a time-frequency characteristic when the front chirp rate according to another embodiment of the present invention is larger than the back chirp rate.
18 is a graph showing a chirp waveform over time when the front culling rate according to another embodiment of the present invention is larger than the backing rate.
19 is a graph showing the PSD of the SLC and the MLC when the front culling rate according to another embodiment of the present invention is larger than the backing rate.
20 is a graph showing cross-correlation characteristics when the front culling rate according to another embodiment of the present invention is larger than the backing rate.
FIG. 21 is a graph showing a time-frequency relationship between an SLC and an MLC according to another embodiment of the present invention.
22 is an exemplary table showing bandwidth allocation according to an embodiment of the present invention.
23 is a graph showing a case where the enemy group demodulates a signal using the entire bandwidth.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Like reference numerals are used for similar elements in describing each drawing.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component. The term "and / or" includes any combination of a plurality of related listed items or any of a plurality of related listed items.

Unless otherwise defined, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Should not.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an AJ / LPI (Anti-Jamming / Low Probability of Intercept) enhancement system and method for a wireless communication system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Generally, a receiver (not shown) accurately demodulates a signal transmitted through a matched filter for a chirp signal transmitted from a transmitter (not shown). Generally, a matched filter is greatly influenced by a cross-correlation characteristic. When a mismatched filter is applied to a transmitted chirp signal, cross-correlation is performed. The transmission performance is degraded due to the influence.

In the case of a friend, it is possible to distinguish transmitted signals by using different matched filters. In this case, a signal capable of improving matching characteristics can improve the transmission performance. However, in case of mismatch, it is impossible to accurately demodulate the signal even if the signal is detected. That is, if a unique chirp rate pattern is used, the signal is not intercepted by the enemy, while improving the transmission performance of the ally.

Therefore, in an embodiment of the present invention, a chirp rate pattern based on a PN (pseudo noise) that can increase the mismatch sensitivity of chirp is used to calculate an anti-jamming / low probability Intercept) to improve performance.

FIG. 6 is a block diagram of an anti-jamming and low probability of intercept (AJ / LPI) enhancement system 600 for a wireless communication system according to an embodiment of the present invention. 6, the AJ / LPI (Anti-Jamming and Low Probability of Intercept) enhancement system 600 includes a modulator 600 for modulating a received signal d (t) to generate a modulated signal s (t) A diffuser 620 for applying a first chirp rate pattern to a signal to generate a first chirp signal x (t), and a jamming output signal y (t) for a first chirp signal x (t) A despreader 640 for generating a second chirp signal r (t) by applying a second chatter rate pattern to the jamming output signal y (t), a second chirp signal r (t) A demodulator 650 for generating a demodulation signal, an integrator 660 for integrating the demodulation signal to generate a final output signal, a coding rate generating module 670 for generating a first coding rate pattern and / or a second coding rate pattern, And a determination unit 680 for determining the transmitted signal by comparing the magnitudes of the output signals.

The churn rate generation module 670 includes a PN sequence generator 671 for generating a PN (Pseudo Noise) sequence, a chatter rate pattern generator 672 for generating various chatter rate patterns according to the PN sequence, and the like .

FIG. 7 is a graph illustrating a time-frequency relationship between an alien transmitter and an enemy interceptor according to an embodiment of the present invention. Referring to FIG. Referring to FIG. 7, considering a worst case, a single chirp rate is assigned to each user in the case of a user 1 (Single Linear Chirp; "SLC"), and a center frequency and a band are assigned to an interceptor If detected, the enemy communication signal can be intercepted because the enemy arm can reverse the Chirp signal based on the same center frequency and band as the user.

와 확산 대역

를 정확하게 알지 못하게 하는 것이 AJ/LPI의 핵심이라고 할 수 있다. 즉, 도 7의 Time-Frequency 특성의 예시와 같이, 전송된 처프(Chirp) 신호에 완벽하게 정합되는 Chirp 신호를 역으로 생성할 수 없게 하는 것이 본 발명의 차이점이다.Therefore, in order to give the most general mismatching characteristic, by dividing the specific time such as the Multiple Linear Chirp (MLC) in the user 2 and changing the chirp rate pattern,

And spread spectrum

It is the core of AJ / LPI that it does not know accurately. That is, it is a difference of the present invention that, as an example of the time-frequency characteristic of FIG. 7, it is impossible to inversely generate a Chirp signal perfectly matched to a transmitted chirp signal.

In general, the frequency-hopped multi-user Chirp Modulation (FH / M-CM) scheme is used to improve the access and transmission performance for multiple users. We propose a new technique.

If the existing FH / M-CM scheme uses PN for frequency hopping, PN may be used to change the Chirp Rate in an embodiment of the present invention. There are two main ways of using the PN sequence. FIG. 8 is a view showing these two.

를 균등하게 분할하여 PN 시퀀스(Sequence)에 따라 2개의 처프(Chirp)로 전송한다. 좌표로 생각할 경우, X축인 Sweeping 시간

의 균등 시간 (

)은 고정, Y축인 Frequency

가 가변이다.8 is a graph showing two chirp rate patterns 810 according to PN (Pseudo Noise) and four chirp rate patterns 820 according to PN (pseudo noise). Referring to FIG. 8, in the case of two chirp rate patterns 810 according to pseudo noise (PN), a sweeping time

And transmits them to two chirps in accordance with the PN sequence. When considering the coordinates, the sweep time

Equivalent time of

) Is a fixed, Y-axis frequency

Is variable.

를 4등분으로 분할하여 PN 시퀀스(Sequence)의 조합에 따라 4개의 Chirp으로 전송한다. 좌표로 생각할 경우, X축과 Y축 모두 가변이다. In the case of four chirp rate patterns 820 according to PN (Pseudo Noise), the sweeping time

Is divided into four equal parts and transmitted to four chirps according to the combination of the PN sequences. When considered in terms of coordinates, both the X and Y axes are variable.

6 to 8 will be described as a general case and a case where an embodiment of the present invention is applied as follows. First, let's look at the AJ / LPI aspect.

(Case # 1) In the general case where SLC (Single Linear Chirp) and MLC (Multiple Linear Chirp) have the same chirp rate

The following parameters are considered to confirm the case where the MLC has the same chirp rate as the SLC.

,

,

-

,

,

시간 동안 0~3.5MHz,

시간 동안 3.5MHz~7MHz까지 Sweeping 하기 때문에

시간 동안 0~7MHz까지 Sweeping 하는 SLC 기법과 동일한 Chirp 파형 특성을 지님-

0 to 3.5 MHz,

Sweeping from 3.5MHz to 7MHz over time

It has the same Chirp waveform characteristics as the SLC technique that sweeps from 0 to 7 MHz over time.

FIG. 9 is a graph showing time-frequency characteristics when a general SLC (Single Linear Chirp) and an MLC (Multiple Linear Chirp) have the same sampling rate. Referring to FIG. 9, there is shown a graph showing a light time-frequency characteristic using two chirp rate patterns considered in FIG. 8 according to a PN sequence. FIG. 9 shows the time-frequency characteristic. It is assumed that the chirp rate of the front chirp and the back chirp of the MLC is the same as that of the SLC.

10 is a graph showing the waveform of chirp over time when SLC and MLC have the same chirp rate. Referring to FIG. 10, a waveform of a chirp according to time is shown, which shows the same waveform as that of a general SLC.

11 is a graph showing the PSD (Power Spectral Density) of SLC (Single Linear Chirp) and MLC (Multiple Linear Chirp) when SLC and MLC have the same sampling rate. Referring to FIG. 11, the PSDs of the SLC and the MLC are shown, and it can be seen that they have the same PSD.

12 is a graph showing cross correlation characteristics when SLC and MLC have the same culling rate. Referring to FIG. 12, the cross-correlation characteristics of the MLC and the SLC are shown. Correlation is also the same because the time-frequency characteristics are the same.

시간에서 MLC의 백 처프(Back Chirp)가 프론트 처프(Front Chirp)와 자연스럽게 이어지지 않지만 동일한 처프율(Chirp Rate)을 지니고 있어 PSD 및 상관(Correlation) 특성이 SLC와 유사하다. 이로 인해 적군이 아군의 신호를 인터셉트하기 쉽다.Therefore, according to Figs. 9 to 12,

At the time, back chirp of MLC does not naturally connect with front chirp, but has the same chirp rate, so PSD and correlation characteristics are similar to SLC. This makes it easier for the enemy army to intercept the friendly army's signal.

(Case # 2) In accordance with an embodiment of the present invention in which SLC and MLC have the same Chirp Rate,

When PN = 0

The parameters for the case of PN = 0 are as follows.

,

,

-

,

,

시간 동안 1.75MHz~5.25MHz까지 Sweeping 하기 때문에

시간 동안은 SLC 보다 느리게 Sweeping하게 되며,

시간 동안 SLC 보다 빠르게 Sweeping 하게 된다.- 0 to 1.75 MHz,

Sweeping from 1.75MHz to 5.25MHz during the time

Sweeping is slower than SLC for a while,

Sweeping is faster than SLC for a while.

13 to 16 show the explanations of the results of applying the above parameters.

FIG. 13 is a graph showing time-frequency characteristics when the front chirp rate according to an embodiment of the present invention is smaller than the back chirp rate. Referring to FIG. 13, the front-chirp of the MLC has a slower chirp rate than that of the SLC, the back chirp has a chirp rate lower than that of the SLC, This is assumed to be fast.

14 is a graph showing the waveform of chirp over time when the front rate is smaller than the back rate. Referring to FIG. 14, the waveform of the chirp according to time is shown. As described above, the front chirp portion has a slower cycle than the normal waveform, and the back chirp portion has a faster cycle than the normal waveform. You can see what you see.

15 is a graph showing the PSD (Power Spectral Density) of SLC and MLC when the front crate ratio is smaller than the back cage rate. Referring to FIG. 15, the PSD of LC and MLC is shown. In case of MLC, accurate center frequency and bandwidth can not be known.

FIG. 16 is a graph showing cross-correlation characteristics when the front culling rate is smaller than the backing rate. Referring to FIG. 16, cross-correlation characteristics between MLC and SLC are shown. In the MLC scheme having the same time-frequency characteristics, a large correlation occurs, and it is confirmed that there is little correlation between SLC and MLC. .

As shown in FIGS. 13 to 16, since the correlation between the MLC-SLCs is small due to the application of the embodiment of the present invention, the demodulation performance of the signal will be deteriorated and the performance of the SLC using the SLC Interception and / or Jamming. [0035]

On the other hand, when PN = 0

The case where the MLC transmits "1" bit is considered, and the parameters are as follows.

,

,

-

,

,

시간 동안 0~5.25MHz,

시간 동안 5.25MHz~7MHz까지 Sweeping 하기 때문에

시간 동안은 SLC 보다 빠르게 Sweeping 하게 되며,

시간 동안 SLC 보다 느리게 Sweeping 하게 된다.-

0 to 5.25 MHz,

Because it sweeps from 5.25MHz to 7MHz over time

Sweeping is faster than SLC for a while,

Sweeping is slower than SLC over time.

Figs. 17 to 20 show the explanations of the results of applying the above parameters.

17 is a graph showing a time-frequency characteristic when the front chirp rate according to another embodiment of the present invention is larger than the back chirp rate. Referring to FIG. 17, a time-frequency characteristic is shown. The front chirp of the MLC is faster than the SLC, the back chirp is faster than the SLC, and the back chirp is faster than the SLC. The chirp rate was assumed to be slow.

18 is a graph showing the waveform of chirp over time when the front rate is larger than the back rate. Referring to FIG. 18, the waveform of chirp according to time is shown. As described above, the front chirp portion has a faster cycle than the normal waveform, and the back chirp portion has a waveform You can see the slow cycle.

19 is a graph showing the PSD of the SLC and the MLC when the front rate is greater than the back rate. Referring to FIG. 19, the PSD of the SLC and the MLC is shown. In the case of the MLC, the accurate center frequency and the bandwidth are unknown.

20 is a graph showing cross-correlation characteristics when the front-cage ratio is larger than the back-cage rate. Referring to FIG. 20, a cross-correlation characteristic between an MLC and an SLC is shown. Correlation is largely generated in an MLC scheme having the same time-frequency characteristics. It can be confirmed that there is little correlation.

In terms of transmission, a typical CSS-DM transmitter transmits only one direction of chirp, and a receiver uses a Chirp matched filter used in the transmitter. In other words, when a transmitter transmits data using an up-chirp, the receiver uses a down-chirp. However, as described above, the signal using the same chirp rate pattern can be intercepted by the enemy group. In order to compensate for this, the chirp rate is assigned differently according to the PN sequence in the embodiment of the present invention.

시간까지

MHz 대역폭을 사용하고, PN 시퀀스가 0일 때에는

시간까지

MHz 대역폭을 사용한다. 21 is a graph showing the time-frequency relationship between SLC and MLC. Referring to FIG. 21, the time-frequency relationship between the SLC and the MLC is shown. When the PN sequence of the MLC is 1

By time

MHz bandwidth, and when the PN sequence is 0

By time

MHz bandwidth.

의 차이

(MHz)에 따른

과

의 값을 정리한 것이다.22 is an exemplary table showing bandwidth allocation according to an embodiment of the present invention. Referring to FIG. 22,

Difference

(MHz)

and

.

The contents and results of the experiments shown in Figs. 9 to 22 are summarized as follows.

를 이용하여 아군의 수신기(Rx)에게 전송하고 있다.In the table of FIG. 22, it is assumed that the allied transmitter (Tx)

To the receiver (Rx).

Also, in the worst case (Worst Case), the enemy group does not know the friendly PN code.

=7MHz을 알고 있지만 MLC의 패턴을 모르고 있는 경우이다.In addition, the assumptions to be considered in the above experiment are as follows:

= 7MHz, but you do not know the pattern of MLC.

Also, we are trying to verify the BER performance in the enemy receiver assuming that the SLC is used to demodulate the allied signal.

23 is a graph showing a case where the enemy group demodulates a signal using the entire bandwidth. Referring to FIG. 23, the BER transmission performance of the case where the alliance is demodulated by the MLC with respect to the signal transmitted by the MLC (Alliance) and the case where the enemy arm is demodulated by the SLC in the situation where the accurate Chirp Rate pattern is unknown .

600: AJ / LPI (Anti-Jamming and Low Probability of Intercept)
610: Modulator
620: diffuser
630: Jamming adder
640: Despreader
650: Demodulator
660: integrator
670: Churn Rate Generation Module

Claims (8)

1. An AJ / LPI (Anti-Jamming and Low Probability of Intercept) enhancement system for a wireless communication system,
A modulator for modulating a received signal to generate a modulated signal;
A spreader for generating a first chirp signal by applying a first chirp rate pattern to the modulated signal;
A jamming adder for adding a jamming signal to the first chirp signal to generate a jamming output signal;
A despreader for generating a second chirp signal by applying a second chatter rate pattern to the jamming output signal;
A demodulator for demodulating the second chirp signal to generate a demodulation signal;
An integrator for integrating the demodulated signal to generate a final output signal;
A determining unit determining a signal to be transmitted using the final output signal; And
And a culling rate generating module for generating the first culling rate pattern and the second culling rate pattern,
The culling rate generation module comprises a PN sequence generator for generating a PN (Pseudo Noise) sequence and a culling rate pattern generator for generating various culling rate patterns according to the PN sequence,
The PN sequence changes the coding rate of the coding rate pattern,
Wherein the first cull pattern pattern or the second cull pattern pattern is configured differently by dividing a predetermined time in advance to increase the mismatch sensitivity of the chirp.
delete The method according to claim 1,
Wherein the first cull pattern pattern or the second cull pattern pattern divides the specific time equally and transmits the two patterns according to the PN sequence.
The method according to claim 1,
Wherein the first cull pattern pattern or the second cull pattern pattern divides the specific time into quadrants and transmits four patterns according to a combination of the PN sequences.
The method according to claim 1,
Wherein the first chirp signal and the second chirp signal are SLC (Single Linear Chirp) or MLC (Multiple Linear Chirp).
6. The method of claim 5,
The chirp rate of the front chirp and the back chirp of the MLC is different from the chirp rate of the front chirp and the back chirp of the SLC AJ / LPI enhancement system for a wireless communication system.
6. The method of claim 5,
When the PN sequence of the MLC is 1

By time

MHz bandwidth, and when the PN sequence is 0

By time

MHz bandwidth,

Represents the sweep time,

and

Quot; represents the bandwidth of each chirp). ≪ / RTI >
1. A method for increasing AJ / LPI (Anti-Jamming and Low Probability of Intercept) for a wireless communication system,
(a) modulating a received signal by a modulator to generate a modulated signal;
(b) a diffuser applying a first chirp rate pattern to the modulated signal to generate a first chirp signal;
(c) adding a jamming signal to the first chirp signal to generate a jamming output signal;
(d) a despreader applying a second chatter rate pattern to the jamming output signal to generate a second chirp signal;
(e) demodulating the second chirp signal to generate a demodulation signal;
(f) integrating the demodulation signal by an integrator to generate a final output signal; And
(g) determining a signal to be transmitted using the final output signal,
Wherein the step (b) and the step (d) include the step of generating the first cull pattern and the second cull pattern, respectively,
The culling rate generation module comprises a PN sequence generator for generating a PN (Pseudo Noise) sequence and a culling rate pattern generator for generating various culling rate patterns according to the PN sequence,
The PN sequence changes the coding rate of the coding rate pattern,
Wherein the first cull pattern pattern or the second cull pattern pattern is configured differently by dividing a specific time in advance to increase the mismatch sensitivity of the chirp.

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