KR20150062706A

KR20150062706A - Method and apparatus for spectrum sensing in frequency hopped communication systems

Info

Publication number: KR20150062706A
Application number: KR1020130147648A
Authority: KR
Inventors: 오혁준
Original assignee: 오혁준
Priority date: 2013-11-29
Filing date: 2013-11-29
Publication date: 2015-06-08

Abstract

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for spectral sensing of a frequency hopping signal, which calculates the energy of a received signal with respect to a carrier position and a temporal position in all cases, A method of estimating a frequency hopping pattern by judging the point where the frequency hopping starts and the point where the frequency hopping starts from the existing carrier to the new carrier using the characteristic of the signal as the magnitude of the average energy difference value in the specific two hours And apparatus.

Description

TECHNICAL FIELD [0001] The present invention relates to a method and apparatus for spectral sensing of a frequency hopping signal,

A method and apparatus for estimating and tracking a frequency hopping pattern in a time domain and a frequency domain of a corresponding signal in real time through spectral sensing even if the unknown frequency hopping pattern is unknown in a wireless communication system that performs random frequency hopping communication .

In wireless communication systems, frequency hopping is performed for the purpose of security to prevent eavesdropping or to improve performance through spreading gain. The frequency hopping is to change the carrier used by the communication system periodically or non-periodically to another counter-clockwise transmission. Therefore, if information on the position of the carrier to be changed is not known every time, communication is impossible. In addition, by using all of the frequency bands that are hopping in frequency, the spreading effect can be obtained because of the spread spectrum effect.

For communication in this frequency hopping environment, it is necessary to know the frequency hopping pattern. Although the frequency hopping patterns may already be known to each other at the transmitting and receiving end, in a situation where security is important, the receiving end demodulates the frequency hopping pattern by estimating the frequency hopping pattern without knowing the frequency hopping patterns.

The frequency hopping pattern to be estimated has a two-dimensional pattern characteristic such as frequency hopped carrier position (frequency domain) and time (frequency domain) where frequency hopping is performed to another carrier position on the current carrier.

FIG. 1 shows a frequency hopping signal on a two-dimensional display in a frequency domain (vertical axis) and a time domain (horizontal axis). There are a total of M frequency hopping carriers divided by the desired carrier resolution unit, and similarly, the resolution of the time domain is determined according to a cycle for determining the presence or absence of a signal at a specific frequency. In this case, one of the squares for determining whether there is a signal for one carrier and one specific time in FIG. 1 is defined as a grid. A black rectangle indicates the time and frequency location of the current signal. As shown in FIG. 1, a plurality of lines can be observed. The length of the line depends on the frequency hopping period, which is proportional to the time it takes to stay on a carrier. The position of the line on the vertical axis is the carrier position.

As shown in FIG. 1, in order to estimate the frequency hopping pattern, it is necessary to determine the position of the frequency where the signal exists periodically. That is, in FIG. 1, it is determined whether or not a signal exists at a specific frequency at a specific time, and a two-dimensional pattern as shown in FIG. 1 should be created. That is, a two-dimensional pattern must be completed through spectrum sensing. However, when the signal-to-noise ratio of the signal is small due to the characteristic of the transmission channel including the noise included in the received signal, it is determined that the signal does not exist even though the signal exists at the corresponding frequency position, .

A method for determining the presence or absence of a signal at a specific time or at a specific frequency is to extract only the signal at the corresponding frequency using a narrowband bandpass filter and calculate the energy of the extracted signal to calculate the energy It is judged that a signal exists at the corresponding frequency of the corresponding time.

However, as described above, this method has a problem that the presence or absence of a signal is erroneously determined when the signal-to-noise ratio is low depending on the characteristics of noise and transmission channel. In order to solve this problem, error correction is performed through post-processing. As described above, the received frequency hopping signal has a long horizontal line shape in a two-dimensional space as shown in FIG. 1, which is proportional to the frequency hopping period. Therefore, a pattern having a continuous line shape of a certain length or more should be displayed. If the noise-to-signal ratio is low depending on the characteristics of noise and transmission channel using this feature, the presence or absence of the signal may be mistakenly judged. If the length of the continuous line is short or discontinuous, The post-processing is performed through a correction operation in which the length of a line longer than a certain length is displayed by reversing the region where the correction is performed.

However, since this method restores based on the continuity of lines rather than accurately determining the presence or absence of actual signals even through post-processing, the accuracy of restoration can not be assured in a situation where the length of the line is not precisely known. It becomes severe. In order to find the discontinuity of the line and perform the inversion process, the 2-dimensional frequency hopping pattern made only by the initial energy magnitude comparison is repeatedly read and post processed, and the modified 2-dimensional pattern is stored again, It is necessary to perform an operation to perform post-processing on the pattern, so that the required memory size is increased, the overall complexity including the computational complexity is greatly increased, and the initial two-dimensional pattern is repeatedly read and written in the post- There is a problem that the real time property is degraded due to the long processing time that occurs.

Therefore, it is an object of the present invention to provide a method and apparatus for spectral sensing of a frequency hopping signal that has a real-time property and can greatly improve the estimation performance of a frequency hopping pattern while having a low complexity.

The objects of the present invention are not limited to the above-mentioned objects, and other objects and advantages of the present invention which are not mentioned can be understood by the following description, and will be more clearly understood by the embodiments of the present invention. It will also be readily apparent that the objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.

In order to achieve the above object, the present invention proposes a method of extracting only a starting point and a finishing point of a certain line, which occurs when a frequency hopping signal is present in FIG. 1, As shown in FIG.

As shown in FIG. 2, according to the present invention, an average of energy measurement values for N grids having the same carrier adjacent to the corresponding grid is obtained for two grids spaced apart at regular intervals having the same carrier, Is determined as the starting point when the absolute value of the difference value of the energy average value is greater than the specific threshold value and the difference value of the two average values is positive, and if the difference value is negative, it is determined as the end point.

According to the present invention having such a configuration, since there is no need for an additional post-processing process, there is no delay due to this, real-time property is ensured and storage of the transitional two-dimensional frequency hopping pattern generated in the post- There is an advantage that no memory is required. In addition, in determining the presence or absence of a signal with respect to a specific frequency at a specific time, an energy value of a grid adjacent to the grid is averaged to increase the signal-to-noise ratio, thereby enhancing the performance of determining whether a signal exists at a specific time or at a specific frequency have.

1 shows a general frequency hopping pattern in which a frequency domain is a vertical axis and a time domain is a horizontal axis.
Figure 2 shows the energy of the signal at each grid for a particular carrier at the start and end of frequency hopping.
3 is a method and apparatus for spectral sensing of a frequency hopping signal proposed by the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS The above and other objects, features and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings, It can be easily carried out. In the following description, well-known functions or constructions are not described in detail since they would obscure the invention in unnecessary detail. Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

3 is a method and apparatus for spectral sensing of a frequency hopping signal proposed by the present invention. After separating the received signal by each of the carrier waves through the filter bank 300, the energy of the separated signal for each carrier is obtained (301).

Next, an average energy of M grids adjacent to each other on the time axis is obtained (302), and an average energy of M grids adjacent to the grid spaced apart by N grid intervals on the past time axis is obtained (303).

Next, the difference between the two values is obtained by subtracting the energy obtained from the apparatus 303 from the average energy obtained from the apparatus 302 of FIG. 3 (304). The absolute value of the difference is compared with a threshold value ) &Lt; / RTI > If the size of the difference value is greater than the threshold value and the sign is positive, the frequency hopping start point is set and stored in the memory. If the difference value is negative, the frequency hopping end point is set and stored in the memory.

Next, a final two-dimensional frequency hopping pattern is stored (308) by making a line connecting the frequency hopping start point stored in the device 307 of FIG. 3 and the frequency hopping end point.

Claims

Dividing the received signal by each of the carriers through a filter bank and obtaining the energy of the separated signal for each carrier; obtaining average energy for M grids adjacent to each other on the time axis; Obtaining a mean energy of M grids adjacent to a grid spaced apart by N grid intervals on a time axis; comparing differences between the two average energy values; comparing an absolute value of the difference values with a threshold value; If the difference value is greater than the threshold value and the sign of the difference is positive, the frequency hopping start point is set as a start point of the frequency hopping and stored in the memory; if the difference value is negative, And a pattern that connects the stored frequency hop start and end points with a line. And storing the final two-dimensional frequency hopping pattern.