KR20070091984A - Method and apparatus for radar signal detection in wireless lan using 5ghz - Google Patents

Abstract

A method and an apparatus for detecting a radar signal in a wireless LAN using 5GHz are provided to detect the radar signal by adding a simple signal processor to an present wireless LAN device. A first determination process is performed to determine possibility of a radar signal within a received signal according to the intensity of the received signal(1,2). The first determination process includes a process for measuring the intensity of the received signal, a process for determining the possibility of the radar signal within the received signal according to a first manner when the intensity of the received signal exceeds a predetermined reference value, and a process for determining the possibility of the radar signal within the received signal according to a second manner when the intensity of the received signal exceeds a predetermined reference value. A measurement process is performed to measure a parameter of the received signal(3,4). A second determination process is performed to determine whether the radar signal is included in the received signal on the basis of the measured parameter or not(6,7).

Description

Method and apparatus for detecting radar signal in wireless LAN using 5 ＧHｚ {Method and apparatus for radar signal detection in wireless lan using 5 Hz}

1 is a flowchart of a radar signal detection method according to an exemplary embodiment of the present invention.

FIG. 2 is a detailed flowchart of a method (step 2) for determining whether the radar signal shown in FIG. 1 is likely to be included in accordance with a preferred embodiment of the present invention.

3 is a diagram illustrating a positional relationship between a predetermined signal and a WLAN signal in a received signal according to an exemplary embodiment of the present invention.

FIG. 4 is a first preferred embodiment showing determination of the wireless LAN reception state (step 24) shown in FIG.

FIG. 5 is a second preferred embodiment showing determination of the wireless LAN reception state (step 24) shown in FIG.

6 is a diagram illustrating a method (step 6) of analyzing signal parameter values shown in FIG. 1 according to an exemplary embodiment of the present invention.

FIG. 7 is a diagram illustrating a dynamic frequency selection (DFS) execution method defined in IEEE 802.11h according to an embodiment of the present invention.

8 is a diagram illustrating an apparatus for detecting radar signals according to an exemplary embodiment of the present invention.

The present invention relates to a method and apparatus for detecting a radar signal in a wireless LAN, and more particularly, to a method and apparatus for efficiently detecting a radar signal without expensive equipment in the frequency band of 5 GHz.

In order to overcome the inconvenience of wired communication, in which communication technology is developed and wire is always required for communication, various wireless communication methods are used. The Institute of Electrical and Electronic Engineers (IEEE) 802.11 series of wireless LANs is one of them. IEEE 802.11 is divided into a / b / g / (n) according to the frequency and method used. Among them, IEEE 802.11a transmits and receives a frequency band of 5 GHz using orthogonal frequency division multiplexing (OFDM). . However, this 5GHz band is already used by military radars, weather, radionavigation and satellite radars, and not only the International Telecommunications Union-Radiocommunications (ITU-R) but also the European Telecommunications Standards Institute (ETSI). ) And the Federal Communications Commission (FCC) are aware that wireless LANs using this band pose serious problems for radars, and to address these issues, we've adopted 'DFS (Dynamic Frequency Selection)' and 'TPC'. In order to minimize the effects on the radar signal, a method called 'Transmit Power Control' is used. Dynamic Frequency Selection (DFS), which detects radar signals and avoids the channel on which they are located, resumes communication on a new channel, as defined in IEEE 802.11h. It is a mechanism to notify the members of the network after being recognized and to move the channel. However, since active frequency selection (DFS) does not include information on how to actually detect radar signals, there is a problem in that radar signals generated from radars must be detected to detect radars. Therefore, in order to solve this problem, although a radar signal may be detected by using an expensive and precise device, in order to perform active frequency selection (DFS), it is not necessary to detect the radar signal in the WLAN and interpret the signal. Since radar signal detection capability is unnecessary, there is a problem that it is inefficient to use in actual cases.

The technical problem to be achieved by the present invention is to detect the radar signal used in the active frequency selection (DFS, Dynamic Frequency Selection), add a simple signal processing to the existing wireless LAN device without adding an expensive device to add a radar signal To provide an apparatus and method for detecting. Further, the present invention provides a computer-readable recording medium having recorded thereon a program for executing the above method on a computer.

According to another aspect of the present invention, there is provided a method of detecting a radar signal, the method comprising: determining that a radar signal may be included in the received signal according to the strength of a signal received from the outside; Measuring a parameter of the signal according to the determined result; And determining whether a received signal is included in the received signal based on the statistical value of the measured parameter.

In order to solve the above other technical problem, the present invention provides a computer-readable recording medium that records a program for executing the above-described radar signal detection method on a computer.

According to another aspect of the present invention, there is provided a radar signal detection apparatus, including: a determination unit determining whether a radar signal may be included by comparing an intensity of a signal received from the outside with a predetermined reference; A measuring unit measuring a parameter of the signal according to a result of the determining unit; And an analysis unit to determine whether the radar signal is based on the statistical value of the measured parameter.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flowchart of a radar signal detection method according to an exemplary embodiment of the present invention.

Referring to FIG. 1, the radar signal detection method according to the present embodiment includes the following steps. In particular, the radar signal detection method according to the present embodiment is composed of steps that are processed in time series at the receiving end of the wireless LAN shown in FIG. Therefore, even if omitted below, the above descriptions of the receiver shown in FIG. 1 also apply to the radar signal detection method according to the present embodiment.

In step 1, the receiving end receives the first signal from the outside.

In step 2, the receiving end determines whether the radar signal may be included in the received first signal. In other words, it is determined whether the radar signal is likely to be included, and if there is a possibility, the received first signal is transmitted in three stages, and if there is no possibility, the process returns to the first stage again to receive another second signal and the radar signal may be included. Repeat the step to determine if there is.

FIG. 2 is a detailed flowchart of a method (step 2) for determining whether the radar signal shown in FIG. 1 is likely to be included in accordance with a preferred embodiment of the present invention.

Referring to FIG. 2, according to the present embodiment, a method of determining whether a radar signal corresponding to step 2 of FIG. 1 may be included may include the following steps. In particular, the method for determining whether or not the radar signal according to the present embodiment may be included is composed of steps that are processed in time series at the receiving end shown in FIG. Therefore, even if omitted below, the above descriptions of the receiver shown in FIG. 2 also apply to a method of determining whether a radar signal according to the present embodiment may be included.

In step 21, the receiving end compares the magnitude of the received signal strength index (RSSI) of the received first signal with the magnitude of the interference detection criterion to compare the received signal strength index (RSSI) of the received first signal. It is determined whether the size of the indication is larger than the interference detection reference size. At this time, the size of the interference detection reference may be set to -62 dBm or -64 dBm according to ETSI (European Telecommunication Standard Institute) 301 893. If the received signal strength index (RSSI) of the received first signal is greater than the interference detection criterion, the process proceeds to step 22. If the received signal strength index is smaller than the interference detection criterion, the radar signal may be included in the received first signal. Judge that there is no and exit.

In step 22, the receiving end determines whether a WLAN packet is detected in the received first signal. If it is determined that the WLAN packet is detected, step 23 is performed. If the WLAN packet is not detected, step 25 is performed. At this time, the detection of the WLAN packet can be known through the preamble of the received WLAN packet.

3 is a diagram illustrating a positional relationship between a predetermined signal and a WLAN signal in a received signal according to an exemplary embodiment of the present invention. Depending on whether the WLAN packet is detected, it is possible to know whether the WLAN signal is received by overlapping the received first signal shown in FIG. 2.

Referring to FIG. 3, when the receiving end detects the WLAN packet, it may be estimated whether the WLAN signal is received by overlapping the received first signal.

Section 1 is a section in which the WLAN packet 40 is not detected and is composed of a channel idle section in which no actual transmission is made and a section between the WLAN packet. In this way, the pulse wave 30 received in the interval 1 in which the WLAN packet 40 does not exist can be detected because it does not overlap the WLAN packet 40. In this case, the pulse wave 30 is not affected by the WLAN signal at all. Therefore, it is possible to measure the received signal strength index (RSSI) of the pulse wave 30, and to compare the measured received signal strength index (RSSI, Received Signal Strength Indication) with the reference interference magnitude of the radar, You can check the drop occurrence and measure the pulse width.

Section 2 is a section in which the WLAN packet 40 is detected. As such, when the pulse wave 30 is received within the section in which the WLAN packet 40 is detected, the WLAN signal may not be smoothly received due to the presence of the pulse wave 30. In this case, a signal error, a frame check sequence (FCS) error, an EQ_SNR (Equalized_Signal-to-Noise Ratio) drop, or the like may occur depending on which portion of the WLAN signal data frame is located in the pulse wave 30. Through a phenomenon in which wireless LAN reception is not smooth, it may be determined that a radar signal may be included in a received signal.

Referring back to FIG. 2, in step 23, the wireless LAN of the receiver is operated.

In operation 24, when the WLAN is operated, the reception state of the WLAN signal is examined to determine whether the radar signal may be included. In case of wireless LAN signal error such as FCS (Frame Check Sequence) error or SIGNAL error when receiving wireless LAN, the reception state of wireless LAN signal is smoothly, such as when EQ_SNR (Equalized_Signal-to-Noise Ratio) drop occurs. If not, the receiver assumes that other pulse waves are also received when the WLAN signal is received, and determines that the radar signal may be included in the received signal. However, when the WLAN signal is received at the receiving end without any error, the reception state of the WLAN signal is considered to be smooth. In this case, when the wireless LAN reception state is smooth, no other signal is received together with the wireless LAN signal, and it is determined that the radar signal is not likely to be included in the received signal.

FIG. 4 is a first preferred embodiment showing determination of the wireless LAN reception state (step 24) shown in FIG.

Referring to FIG. 4, when a SIGNAL error or a frame check sequence (FCS) error occurs in a WLAN signal according to the first exemplary embodiment in which the WLAN reception state shown in FIG. 2 is not smooth, It is a figure which shows positional relationship.

A brief description of the data frame 50 of the WLAN signal may include a preamble field 60, a data field 70, and a frame check sequence (FCS) field 80 as shown in FIG. 4. When the data frame 50 and the pulse wave of such a WLAN signal overlaps, the reception of the WLAN signal is not smooth. Looking at each of the WLAN signal data frame 50 sections in detail as follows. When the pulse wave 30 is received in the preamble field 60 section of the WLAN signal data frame 50, a signal error in which signal information is not received correctly occurs. In addition, when the pulse wave 30 is received in the DATA field 70 section or the FCS (Frame Check Sequence) field 80 section, an FCS (Frame Check Sequence) error occurs in which data content is not correctly received. . As described above, the occurrence of a signal error or an FCS error occurs when the WLAN signal and the pulse wave are overlapped with each other. Therefore, when a signal error or an FCS error occurs due to a poor reception of the WLAN signal, it is possible to estimate that the pulse wave 30 is overlapped with the WLAN signal. Therefore, a signal error or a frame check sequence (FCS) can be estimated. From the occurrence of the error, the existence of the pulse wave 30 which may be a radar signal is known.

FIG. 5 is a second preferred embodiment showing determination of the wireless LAN reception state (step 24) shown in FIG.

Referring to FIG. 5, an EQ-SNR (Equalized_Signal-to-Noise Ratio) DROP occurs in a WLAN signal according to a second embodiment in which the WLAN reception state is not smooth.

The WLAN signal is composed of 54 sub-carriers 90, and the sizes of different sub-carriers 90 are equally adjusted, which is equalized by EQ-SNR. noise ratio). At this time, if the received pulse wave 30 overlaps the sub-carriers 91 and 92 of some of the sub-carriers 90, the sub-carriers 91 and 92 become different sub-carriers. Unlike the Sub-Carrier 90, the SNR drops sharply due to the higher specific noise ratio, and when the SNR drops sharply in the sub-carrier where EQ-SNR (Equalized_Signal-to-Noise Ratio) is achieved. EQ_SNR (Equalized_Signal-to-Noise Ratio) Drop occurred. That is, when the sub-carriers 91 and 92 and the received pulse wave 30 overlap each other, EQ-SNR (Equalized_Signal-to-Noise Ratio) DROP occurs in the sub-carrier 90. In this case, as shown in FIG. 4, a frame check sequence (FCS) error or a signal error is also determined by which part of the radio data frame is received, that is, depending on the position of the radio data frame and the pulse wave 30. Occurs. Referring to FIG. 5, a signal error occurs simultaneously with EQ-SNR (Equalized_Signal-to-Noise Ratio) in subcarrier 91 and FCS simultaneously with EQ-SNR (Equalized_Signal-to-Noise Ratio) in subcarrier 92. (Frame Check Sequence) An error occurred. As such, when EQ-SNR (Equalized_Signal-to-Noise Ratio) DROP occurs in the subcarrier 90 of the WLAN, it can be seen that another pulse wave 30 overlaps the WLAN signal. Therefore, the existence of the pulse wave 30 can be known from the generation of the EQ-SNR (Equalized_Signal-to-Noise Ratio) DROP of the WLAN signal, and since the pulse wave 30 is likely to be a radar signal, the EQ of the WLAN signal is high. Equalized Signal-to-Noise Ratio (SNR) It may be determined that the radar signal may be included from the DROP generation.

Referring back to FIG. 2, in step 25, the receiving end detects a pulse wave by measuring whether a sudden power rise occurs in the received first signal.

In step 26, the receiver determines whether a power drop has been made in the detected pulse wave and measures the value. Here, the power drop means a phenomenon in which a sudden increase in pulse waves suddenly decreases again. If the power drop is made from the detected pulse wave, the process proceeds to step 27. If the power drop is not made, it is determined that there is no possibility that the radar signal is included and ends.

In step 27, the receiving end measures the pulse width based on the difference between the power rise occurrence time measured from the detected pulse wave and the measured power drop occurrence time interval.

In step 28, the receiving end compares the measured pulse width with the radar reference value, and if there is a match, determines that the radar signal may be included, and if the measured pulse width does not match the radar reference value, the radar signal may be included. It is judged that there is no and ends. At this time, the radar reference value is present in various ways due to the characteristics of the radar, and may be set to 0.5 s by the European Telecommunications Standards Institute (ETSI), but is not limited thereto.

Referring back to FIG. 1, in step 3, the receiver measures a parameter of the first signal received in step 2. Here, the parameter refers to a value that can represent the periodic characteristics of the signal well, and includes, but is not limited to, the time at which the signal is generated, the interval with the next signal, and the pulse width. The parameter measurement is performed in the same manner without making a difference whether or not the WLAN signal overlaps the received first signal. Even when the WLAN signal overlaps the received first signal, the received first signal is measured with respect to the radar signal. Correlation the DCT (Discrete Cosine Transform) with the coefficients shows the result. If the radar signals are overlapped, the correlation value is increased to determine that the radar signals are present.

In step 4, the receiver stores the parameter of the signal measured in step 3 in the buffer for each item.

In step 5, the receiver determines whether the parameter of the signal exceeds the capacity of a buffer that can be stored. If the buffer can store more parameters of the signal measured in step 4, go back to step 1, receive another second signal, repeat the step of determining the potential radar signal, and measure in step 4 beyond the capacity of the buffer. If the parameters of one signal can no longer be stored, proceed to step 6.

In step 6, the receiver statistically analyzes the parameter of the signal stored for each item in the buffer.

6 is a diagram illustrating a method (step 6) of analyzing signal parameter values shown in FIG. 1 according to an exemplary embodiment of the present invention.

The radar signal can be known through a method of statistically analyzing data storing parameters of each signal, and is not limited to the method shown in this figure. Assuming that the first signal received is composed of five pulse waves 30 as shown in the figure, when the receiving terminal lists each pulse wave 30 in the order received from the left, the pulse wave 30 is P1, P2. , P3, P4, and P5 are listed in this order. In the pulse waves 30 listed in this order, the interval between each pulse wave 30 and the neighboring pulse wave 30 is measured based on the time at which each pulse wave is generated, and the average is generated so that the difference between these values is close to zero. The time reference can be determined. (T = T (PP) -T (PP), T = T (PP) -T (PP), TT0) The average occurrence times R1, R2, R3, R4, When comparing with reference to R5), if the position of each pulse wave actually occurred is within the error range relatively small with the position of average occurrence time (R1, R2, R3, R4, R5), the signal is a periodic signal. Able to know. In this case, the accuracy of the period can be determined by comparing the difference between the respective pulse waves P1, P2, P3, P4, P5 and the average occurrence time R1, R2, R3, R4, R5. It can be seen that the signal received by the method shown in FIG. 6 is a periodic signal. When the similarity is obtained by comparing the period of the periodic signal with the radar signal, it can be seen that the radar signal has a similar period to the radar signal. .

In step 7, the receiving end identifies the periodic characteristics of the signal based on the data analyzed in step 6, and compares the similarity with the radar signal to determine whether it is a radar signal. If it is determined that it is a radar signal, the process proceeds to step 8, and if it is determined that the radar signal is not, the process proceeds to step 9.

In step 8, the receiver performs dynamic frequency selection (DFS) on the received signal determined as the radar signal.

FIG. 7 is a diagram illustrating a dynamic frequency selection (DFS) execution method defined in IEEE 802.11h according to an embodiment of the present invention.

Referring to FIG. 7, it can be seen that DFS (Dynamic Frequency Selection) is performed after the radar signal is determined. As shown in FIG. 7, after measuring the radar, the station management entity (SME) of the STA (Station) A decides to change the channel (Decision to switch channel). A channel change is performed through a procedure transferred from a MAC sublayer management entity (MAC) to a MAC sublayer management entity (MLME) of STA (Station) B. At this time, the transfer of the matter regarding the channel change is not limited to the STA (Station) B, it can be delivered to all STA (Station) existing in the same BSS (Basic Service Set).

Referring back to FIG. 1, in step 9, the receiver operates a timer based on a time when it is determined that the received signal is not a radar signal.

In step 10, the receiving end determines whether the operation time of the timer has passed the reference time. If the operation time does not exceed the reference time, the receiver performs step 9 again. If the reference time has elapsed, the receiver returns to step 1 again and performs another second signal. Repeat the step of receiving and determining the potential radar signal. In this case, the reason for operating the timer in steps 9 and 10 is to adjust the load in consideration of the capacity of a general WLAN device. Therefore, the timer operation time can be determined according to the performance of the WLAN device. If there is no load, the timer operation time can be set to “0” because there is no need to operate the timer.

8 is a diagram illustrating an apparatus for detecting radar signals according to an exemplary embodiment of the present invention.

Referring to FIG. 8, the receiving end 1000 of the wireless LAN according to the present exemplary embodiment includes a determining unit 100, a measuring unit 200, a buffer 300, an analyzing unit 400, and a transmitting unit 500.

The determination unit 100 is composed of a receiver 110, a comparator 120, a frame analyzer 130, and a detector 140.

The receiver 110 of the determiner 100 receives a signal from the outside and transmits the signal to the comparator 120. The comparator 120 compares the strength of the signal received from the receiver 110 with the size of the interference detection criterion. In this case, the size of the interference detection criterion may be set to -62 dBm or -64 dBm according to ETSI 301 893.

As a result of comparing the intensity of the signal received from the receiver 110 and the magnitude of the interference detection criterion by the comparator 120, if the signal strength is greater than the size of the interference detection criterion, the radar signal may be included. The received signal is transmitted to the frame analyzer 130, and if not, the signal is returned to the receiver 110 to receive a new signal. The frame analyzer 130 determines whether a WLAN packet is detected from the received signal. If the WLAN packet is not detected, the received signal is transmitted to the detector 140. The detector 140 detects a pulse wave through whether a sudden power rise or power drop occurs in the signal received from the frame analyzer 130, and transmits the pulse wave to the measurement unit 200 when the pulse wave is detected.

The measurement unit 200 receiving the pulse wave from the detection unit measures a parameter. Here, the parameter refers to a value that can represent the periodic characteristics of the signal well, and includes, but is not limited to, the time at which the signal is generated, the interval with the next signal, and the pulse width. The parameters obtained through the measurement unit are stored in the buffer 300.

In the buffer 300, the parameters received from the measurement unit 200 are continuously stored within the limit not exceeding the capacity of the buffer 300, and if the parameters exceed the capacity of the buffer 300, the parameters stored in the buffer 300. Is transmitted to the analysis unit 400.

The analysis unit 400 determines whether the received signal has periodic characteristics by using a method of statistically analyzing the parameters stored in the buffer 300. In this case, as the statistical analysis method used, the histogram may be interpreted using a method called Periodgram, and various analysis methods using hardware or software may be used.

When the analysis unit 400 determines that the radar has periodic characteristics as a result of analyzing the parameter, the received signal is transmitted to the outside of the receiver through the transmitter 500.

Meanwhile, the above-described embodiments of the present invention can be written as a program that can be executed in a computer, and can be implemented in a general-purpose digital computer that operates the program using a computer-readable recording medium.

The computer-readable recording medium may be a magnetic storage medium (for example, a ROM, a floppy disk, a hard disk, etc.), an optical reading medium (for example, a CD-ROM, DVD, etc.) and a carrier wave (for example, the Internet). Storage medium).

So far I looked at the center of the preferred embodiment for the present invention. Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. The scope of the present invention is shown in the claims rather than the foregoing description, and all differences within the scope will be construed as being included in the present invention.

According to the present invention, a method for detecting a radar signal in a WLAN using 5GHZ first detects a signal that is likely to be a radar signal in an existing WLAN device without the need for additional expensive equipment, and then detects a parameter value of the detected signal. By implementing the present invention by adding the content of the present invention using the method of statistically analyzing the result and to make the starting point to detect the radar signal and operate the DFS (Dynamic Frequency Selection).

Claims (14)

(a) determining that the radar signal may be included in the received signal according to the strength of a signal received from the outside; (b) measuring a parameter of the signal according to the determination result of step (a); And (c) determining whether a received radar signal is included in the received signal based on the statistical value of the measured parameter. The method of claim 1, Step (a) is (a1) measuring whether the strength of the received signal exceeds a predetermined criterion; (a2) if the intensity of the received signal exceeds a predetermined criterion as a result of the measurement in step (a1), determining whether a radar signal is likely to be included in the received signal by a first method; And (a3) if the intensity of the received signal exceeds a predetermined criterion as a result of the measurement in step (a2), determining whether a radar signal is likely to be included in the received signal by a second method; Radar signal detection method characterized in that. The method of claim 2, In the first method of step (a2), when a WLAN packet is detected from the received signal and a SIGNAL error occurs in which the signal information is not correctly received from the WLAN signal, a radar signal is included in the received signal. Radar signal detection method characterized in that it is determined that there is a possibility. The method of claim 2, In the first method of step (a2), if a WLAN packet is detected from the received signal and EQ_SNR DROP occurs in the WLAN signal, it is determined that the radar signal may be included in the received signal. Radar signal detection method. The method of claim 2, In the first method of step (a2), if a WLAN packet is detected from the received signal, and an FCS error occurs in which the content of data is not correctly received from the WLAN signal, a radar signal is added to the received signal. Radar signal detection method characterized in that it is determined that the possibility of inclusion. The method of claim 2, In the second method of step (a3), if a pulse wave is detected in the received signal and a power drop is made, a pulse width is measured correspondingly. If the measured pulse width is equal to a reference value, a radar signal may be included. Radar signal detection method characterized in that it is determined. The method according to claim 1 or 2, And the parameter of the signal includes a time of occurrence of the signal, a pulse width, and an interval from a previous signal. The method according to claim 1 or 2, And the parameter statistical value of step (c) represents a periodic characteristic. The method of claim 1, If it is determined that the predetermined signal is not likely to be included in the step (a), it is executed again. The method according to claim 1 or 2, And the step (c) executes step (a) again if the parameter is not sufficient to represent a statistical value. The method of claim 1, If it is determined that step (c) does not have a predetermined signal, the timer is operated, and when a predetermined time value elapses, step (a) is executed again. The method of claim 12, And a predetermined time value as "0". A computer-readable recording medium having recorded thereon a program for executing the method of any one of claims 1 to 12. A determination unit which determines whether or not a radar signal may be included by comparing the strength of a signal received from the outside with a predetermined reference; A measuring unit measuring a parameter of the signal according to a result of the determining unit; And an analyzer configured to determine whether the radar signal is based on the statistical value of the measured parameter.

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