JP7446604B2 - Wireless communication signal detection device and wireless communication signal detection method - Google Patents

Description

The present invention relates to a wireless communication signal detection device and a wireless communication signal detection method.

The frequency band used in wireless communication is limited, and with the spread of mobile terminals that perform wireless communication, there is a need for a method to use the frequency band more efficiently. From this perspective, techniques for allocating the same frequency band to multiple wireless communication systems are being considered.

Here, in order to prevent interference, for example, when it is detected that a wireless communication system with a higher priority using a predetermined frequency band has started wireless communication, it is necessary to use the same frequency band. Control that stops wireless communication in a wireless communication system with a lower level is considered.

Examples of wireless communication systems with higher priority include wireless relay transmission systems for television broadcasting, wireless communication systems related to disaster prevention or defense, and the like. Furthermore, examples of wireless communication systems with lower priority include wireless communication using mobile phones, smartphones, etc., particularly wireless communication using carrier aggregation that uses multiple frequency bands in a bundle.

However, in order to determine which wireless communication system the observed wireless communication signal belongs to, demodulating it in synchronization with the wireless communication signal requires a relatively expensive sensor device. Further, if a large number of sensor devices are arranged over a wide area and each sensor device is used to observe wireless communication signals, an even larger budget will be required.

In connection with the above, Non-Patent Document 1 (Albin Svensson and Andreas Jakobsson, “Adaptive Detection of a Partly Known Signal Corrupted by Strong Interference ", IEEE SIGNAL PROCESSING LETTERS, VOL. 18, NO. 12, published December 2011) discloses a method for detecting a single signal in the presence of noise and interference in a mixed signal environment. This method is based on the idea of Generalized Likelihood Ratio tests and does not utilize the characteristics of the time waveform.

Albin Svensson and Andreas Jakobsson, “Adaptive Detection of a Partly Known Signal Corrupted by Strong Interference”, IEEE SI GNAL PROCESSING LETTERS, VOL. 18, NO. 12, Published December 2011

A wireless communication signal detection device and a wireless communication signal detection method that can be realized at relatively low cost are provided. Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

Below, means for solving the problem will be explained using the numbers used in (Detailed Description of the Invention). These numbers are added to clarify the correspondence between the claims and the detailed description. However, these numbers must not be used to interpret the technical scope of the invention stated in the (claims).

According to one embodiment, the wireless communication signal detection device (1) includes a sensor device (15), an average power calculation section (121), a characteristic period detection section (122), and a determination section (124). Be prepared. A sensor device (15) monitors the received power of a wireless communication signal included in a predetermined frequency band. The calculation unit (121) calculates the length of the first period of the received power derived from the first wireless communication signal that is included in the wireless communication signal and has periodicity according to a predetermined first period, based on the observation result of the received power. An average frame is calculated having an average value among a plurality of frames, each having a certain value. A characteristic period detection unit (122) detects a characteristic period, which occurs a plurality of times in a first period and has a predetermined characteristic, in the first wireless communication signal, based on the average frame. The determining unit (124) determines detection or non-detection of a second wireless communication signal, which is included in the wireless communication signal and is different from the first wireless communication signal, based on the received power in the characteristic period of the observation result and the average frame. Judgment based on

According to one embodiment, the wireless communication signal detection method includes: observing the received power of the wireless communication signal included in a predetermined frequency band (S02); and detecting the wireless communication signal based on the observation result of the received power. calculating an average frame having an average value among a plurality of frames each having a length of a first period of received power derived from a first wireless communication signal included and having periodicity according to a predetermined first period; (S03). The wireless communication signal detection method further includes detecting, based on the average frame, a characteristic period of the first wireless communication signal that occurs a plurality of times in the first period and has a predetermined characteristic (S04). The wireless communication signal detection method detects or non-detects a second wireless communication signal, which is included in the wireless communication signal and is different from the first wireless communication signal, based on the received power in a characteristic period of an observation result and an average frame. The method further includes making a determination based on the information (S06).

According to the embodiment, a wireless communication signal detection device and a wireless communication signal detection method can be realized relatively inexpensively.

FIG. 1 is a diagram illustrating a configuration example of an environment in which a wireless communication signal detection device according to an embodiment is used. FIG. 2A is a block circuit diagram illustrating a configuration example of a wireless communication signal detection device according to an embodiment. FIG. 2B is a functional block circuit diagram illustrating a configuration example of a wireless communication signal detection device according to an embodiment. FIG. 3 is a flowchart illustrating a configuration example of a wireless communication signal detection method according to an embodiment. FIG. 4A is a diagram illustrating an example of a frame structure of a TD-LTE signal. FIG. 4B is a diagram illustrating a configuration example of a subframe of a TD-LTE signal. FIG. 4C is a diagram illustrating an example of the correspondence between subframes of a TD-LTE signal and temporal changes in received power. FIG. 4D is a diagram illustrating a configuration example of a special subframe of a TD-LTE signal. FIG. 4E is a diagram illustrating a more detailed configuration example of a special subframe of a TD-LTE signal. FIG. 4F is a diagram illustrating an example of the correspondence between special subframes of a TD-LTE signal and temporal changes in received power. FIG. 5A is a diagram for explaining an example of a target of folded average according to one embodiment. FIG. 5B is a diagram illustrating a method for calculating a folded average value according to an embodiment. FIG. 5C is a diagram illustrating an example of a calculation result of a folded average value according to an embodiment. FIG. 6A is a diagram for explaining deviation correction according to one embodiment. FIG. 6B is a diagram for explaining deviation correction according to one embodiment. FIG. 6C is a diagram for explaining deviation correction according to one embodiment. FIG. 6D is a diagram for explaining deviation correction according to one embodiment. FIG. 6E is a diagram for explaining deviation correction according to one embodiment. FIG. 7 is a diagram illustrating an example of a calculation result of a highly accurate aliasing average of received power for one frame, according to an embodiment. FIG. 8A is a diagram illustrating an example of a waveform before noise removal according to one embodiment. FIG. 8B is a diagram illustrating an example of a waveform after noise removal according to one embodiment. FIG. 8C is a diagram illustrating an example of a waveform after performing a moving average according to an embodiment. FIG. 9 is a diagram for explaining an error in detection accuracy of a no-communication period according to an embodiment. FIG. 10 is a diagram showing an example of the position of the DwPTS immediately before the no-communication period, which is included in the special subframe of the TD-LTE signal.

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a wireless communication signal detection device and a wireless communication signal detection method according to the present invention will be described below with reference to the accompanying drawings.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration example of an environment in which a wireless communication signal detection device 1 according to an embodiment is used. In this embodiment, in an environment where wireless signals used in two types of wireless communication systems arrive in a superimposed manner, a case where a wireless signal from a wireless communication system that has higher priority among these two types of wireless communication systems is detected. I will explain about it.

The basic operating principle of the wireless communication signal detection device 1 and the wireless communication signal detection method according to this embodiment may be as follows, for example. That is, by utilizing the structure of a wireless communication signal including a period of no communication that occurs periodically in the first wireless communication system, when the received power during this period of no communication exceeds a predetermined threshold, the second wireless communication It is determined that a wireless signal of the communication system has been detected.

In the environment of FIG. 1, a wireless communication signal detection device 1, a first base station 21, first terminals 22A and 22B, a second base station 31, and a second terminal 32 are arranged. Hereinafter, if there is no need to distinguish between the first terminals 22A and 22B, they may be simply referred to as the first terminal 22.

The first base station 21 and the first terminal 22 belong to a first wireless communication system. Hereinafter, a case will be described in which the first wireless communication system performs wireless communication using the TD-LTE (Time Division Long Term Evolution) method, but this is just an example and does not limit the present embodiment. . In this case, the first terminal 22 may be, for example, a mobile terminal such as a mobile phone or a smartphone. Further, the total number of first terminals 22 is not limited, and there may be a plurality of first base stations 21.

The second base station 31 and the second terminal 32 belong to a second wireless communication system different from the first wireless communication system. Hereinafter, a case will be described in which the second wireless communication system performs wireless communication using an FPU (Field Pickup Unit) method, but this is just an example and does not limit the present embodiment. In this case, the second terminal 32 may be, for example, a relay van for television broadcasting. The total number of second base stations 31 and the total number of second terminals 32 are not limited.

Here, consider a case where the first wireless communication system and the second wireless communication system use the same frequency band. In such a case, in order to prevent interference, when one wireless communication system performs wireless communication, the wireless communication of the other wireless communication system may be stopped.

As an example, consider a case where the second wireless communication system starts wireless communication for a short period of time while the first wireless communication system is constantly performing wireless communication. In such a case, control may be considered to give priority to the second wireless communication system and stop the wireless communication of the first wireless communication system until the wireless communication of the second wireless communication system ends.

Note that if the first wireless communication system supports a technology such as carrier aggregation that bundles and uses multiple frequency bands, even if the use of one of these multiple frequency bands is stopped, By continuing to use the remaining frequency bands, there is no need to worry about the wireless communication itself stopping even if the communication speed decreases.

The wireless communication signal detection device 1 according to this embodiment is placed in such an environment. However, information indicating whether wireless communication is being performed using the desired frequency band is not received from either the first wireless communication system or the second wireless communication system. Even under such conditions, the wireless communication signal detection device 1 according to the present embodiment can detect the wireless signal of the second wireless communication system while the first wireless communication system is constantly performing wireless communication. This will be explained below.

The components of the wireless communication signal detection device 1 according to this embodiment will be explained. FIG. 2A is a block circuit diagram showing a configuration example of the wireless communication signal detection device 1 according to an embodiment. The wireless communication signal detection device 1 in FIG. 2A includes a bus 10, an input/output interface 11, an arithmetic unit 12, a storage device 13, an external storage device 14, and a sensor device 15.

The connection relationship of the components shown in FIG. 2A will be explained. The bus 10 is electrically connected to an input/output interface 11 , an arithmetic unit 12 , a storage device 13 , an external storage device 14 , and a sensor device 15 . In other words, the input/output interface 11, the arithmetic device 12, the storage device 13, the external storage device 14, and the sensor device 15 are electrically connected to each other via the bus 10. In addition, the external storage device 14 is removably connected to the recording medium 141.

The operation of the components shown in FIG. 2A will be explained. Bus 10 mediates electrical communication between other components, either directly or indirectly. The input/output interface 11 performs wired or wireless communication with the outside. The arithmetic device 12 realizes arbitrary functions by reading and executing programs stored in the storage device 13. The storage device 13 readably stores programs and data used by the arithmetic device 12 . The storage device 13 may store data obtained as a result of the arithmetic device 12 executing a program. The external storage device 14 reads programs and data from the recording medium 141 and writes programs and data to the recording medium 141. The sensor device 15 monitors the received power of a wireless communication signal included in a predetermined frequency band.

The components of the wireless communication signal detection device 1 according to the present embodiment will be described from a functional standpoint. FIG. 2B is a functional block circuit diagram showing a configuration example of the wireless communication signal detection device 1 according to an embodiment. The wireless communication signal detection device 1 in FIG. 2A includes a bus 10, an input/output interface 11, an average power calculation section 121, a characteristic period detection section 122, a threshold determination section 123, a determination section 124, a storage device 13, an external storage device 14, and a sensor. A device 15 is provided.

Here, the average power calculation unit 121, the characteristic period detection unit 122, the threshold value determination unit 123, and the determination unit 124 perform a plurality of functions that are realized by the arithmetic unit 12 in FIG. 2A executing programs in the storage device 13. It is expressed as a functional part. Therefore, the average power calculation section 121, the characteristic period detection section 122, the threshold value determination section 123, and the determination section 124 are connected to the bus 10 in the same way as the arithmetic device 12.

Note that the bus 10, input/output interface 11, storage device 13, external storage device 14, and sensor device 15 shown in FIG. 2B are the same as in the case of FIG. 2A, so further detailed explanation will be omitted.

A wireless communication signal detection device 1 according to this embodiment, that is, a wireless communication signal detection method according to this embodiment will be described. FIG. 3 is a flowchart illustrating a configuration example of a wireless communication signal detection method according to an embodiment. The flowchart in FIG. 3 includes a total of eight steps from the first step S01 to the eighth step S08.

When the flowchart of FIG. 3 starts, a first step S01 is executed. In the first step S01, initial conditions related to the wireless communication signal detection method may be set. After the first step S01, a second step S02 is executed.

In the second step S02, the sensor device 15 observes the received power of a wireless communication signal included in a predetermined frequency band. The sensor device 15 may perform observation under the control of the arithmetic device 12 that executes a predetermined program.

The sensor device 15 does not need to have enough accuracy to demodulate the wireless communication signal based on the result of observing the received power. By doing so, in the wireless communication signal detection device 1 according to this embodiment, it is possible to use a relatively inexpensive sensor device 15.

Here, a case will be described in which the first wireless communication system regularly performs wireless communication using the TD-LTE method, and the second wireless communication system does not perform wireless communication. Furthermore, the wireless signal of the first wireless communication system from which the received power observed by the sensor device 15 in such a case is derived will be explained.

The TD-LTE system is a type of time division multiplexing system, and consists of an uplink period in which terminals communicate from the base station to the base station, a downlink period in which communication occurs from the base station to the terminal, and an idle period in which neither communication occurs. Wireless communication is performed by periodically repeating the period included in the communication period at a constant period. This cycle is called a frame.

The period during which the sensor device 15 observes the received power is preferably several times the length of one frame or more. Let this coefficient be an integer N greater than or equal to 2. Hereinafter, a case where the coefficient N is 4 will be described, but this is just an example and does not limit the present embodiment. Note that the coefficient N may be set in the first step S01 as an initial condition. The observation results may be stored in the storage device 13 in any data format.

Here, an example of the configuration of a wireless communication signal of the TD-LTE system will be described.

FIG. 4A is a diagram illustrating a configuration example of frame 4 of a TD-LTE signal. In the present embodiment, a case will be described in which the length of the frame 4 is 10 ms (milliseconds), but this is just an example and does not limit the present embodiment.

Frame 4 in FIG. 4A is divided into 10 consecutive subframes from 0th subframe 400 to 9th subframe 409 in the order of these numbers. Each of subframes 400-409 has the same length. In the present embodiment, a case will be described in which each of the subframes 400 to 409 has a length of 1 ms, but this is just an example and does not limit the present embodiment.

Each of subframes 400 to 409 is set as an uplink subframe, a downlink subframe, or a special subframe. During the uplink subframe, the first wireless communication system performs uplink communication from the first terminal 22 to the first base station 21 . During the downlink subframe, the first wireless communication system performs downlink communication from the first base station 21 to the first terminal 22. The special subframe includes a period for downlink communication, a no-communication period, and a period for uplink communication. Details of the special subframe will be described later.

In this embodiment, a case will be described in which a total of seven types of configurations are set as combinations of settings related to the configuration of subframes, but this is just an example and does not limit the present embodiment.

Note that these configurations in the TD-LTE system are standardized and known. The following description will be made on the premise that information regarding these configurations is stored in the storage device 13 of the wireless communication signal detection device 1 according to this embodiment.

FIG. 4B is a diagram illustrating a configuration example of a subframe of a TD-LTE signal. A total of seven types of configurations are shown in the vertical direction from the 0th configuration #0 to the 6th configuration #6. A total of 10 subframes from the 0th subframe 400 to the 9th subframe 409 are shown in the horizontal direction. At the intersection of each configuration and each subframe, the type of subframe in the combination of the two is indicated by "U," "D," or "S." Here, "U" indicates an uplink subframe, "D" indicates a downlink subframe, and "S" indicates a special subframe.

Here, it should be noted that in combinations in which the downlink subframe is switched to the uplink subframe after the downlink subframe, a special subframe is arranged between the two. Further, the period of these configurations is 10ms for the third configuration #3 to the sixth configuration #6, while it is 5ms like the zeroth configuration #0 to the second configuration #2. I would also like to draw your attention to the good things.

FIG. 4C is a diagram illustrating an example of the correspondence between subframes of a TD-LTE signal and temporal changes in received power. FIG. 4C includes an upper graph and a lower table. The graph in FIG. 4C shows an example of the waveform of the received power of the wireless signal observed by the sensor device 15. The table of FIG. 4C shows an example of the configuration of subframes 400-409 corresponding to the waveform of FIG. 4C.

The horizontal axis common to the graph and table of FIG. 4C indicates time t, whose unit is s (second). The vertical axis of the graph in FIG. 4C indicates received power, and its unit is dBm (decibel milliwatt). In the table of FIG. 4C, "U", "D", and "S" respectively indicate an uplink subframe, a downlink subframe, and a special subframe, as described above. Here, "0.000", which is the start time of the horizontal axis in FIG. 4C, is the time when the value on the graph rapidly increases from about -70 dBm to about -45 dBm, and time t ₀₀ is set to match this time. has been done. After this, time t ₀₁ to time t ₁₀ are successively set every 1 ms, which is the length of a subframe.

In the graph of FIG. 4C, the period from time t ₀₀ to time t ₀₃ has a relatively high upper limit of received power and corresponds to a downlink subframe in which the first base station 21 outputs a wireless signal. Similarly, the period from time t ₀₅ to time t ₀₈ also corresponds to a downlink subframe. The period from time t ₀₄ to time t ₀₅ corresponds to an uplink subframe in which the lower limit of received power is relatively low and the first terminal 22 outputs a wireless signal. Similarly, the period from time t ₀₉ to time t ₁₀ also corresponds to an uplink subframe. The remaining period from time t ₀₃ to time t ₀₄ and period from time t ₀₈ to time t ₀₉ have the characteristics of a relatively high upper limit and a relatively low lower limit of received power, and are special subframes. corresponds to

From these correspondences, it can be read that in the example of FIG. 4C, the observed wireless signal of received power corresponds to the second configuration #2 shown in FIG. 4B. However, it should be noted that the subframe from time t ₀₀ to time t ₀₁ in FIG. 4C corresponds to the third subframe 403 or the eighth subframe 408 of the second configuration #2 shown in FIG. 4B. I want to be Since switching of configurations is relatively rare in the TD-LTE system, the wireless communication signal detection device 1 according to the present embodiment does not need to change the configuration currently used by the first wireless communication system even if it knows in advance the configuration currently used by the first wireless communication system. good.

The configuration of the special subframe 41 will be explained. FIG. 4D is a diagram showing a configuration example of the special subframe 41 of the TD-LTE signal. Special subframe 41 corresponds to any one of subframes 400 to 409 shown in FIG. 4A. Therefore, the length of the special subframe 41 is 1 ms.

The special subframe 41 is divided into three time regions. These three time domains are DwPTS (Downlink Pilot Time Slot) 42, GP (Guard Period) 43, and UpPTS (Uplink Pilot Time Slot) 44, respectively. , are arranged on the time axis in this order.

During the DwPTS 42, the first wireless communication system performs downlink communication from the first base station 21 to the first terminal 22. During UpPTS 44, the first wireless communication system performs uplink communication from the first terminal 22 to the first base station 21. GP 43 is a non-communication period, and no wireless communication is performed between the first base station 21 and the first terminal 22.

A more detailed configuration of the special subframe 41 will be explained. FIG. 4E is a diagram illustrating a more detailed configuration example of a special subframe of a TD-LTE signal. As in the case of FIG. 4B, a total of 10 configurations from the 0th configuration #0 to the 9th configuration #9 are shown in the vertical direction. Also, a total of 14 time slots from the first time slot to the 14th time slot are shown in the horizontal direction. At the intersection of each configuration and each time slot, the type of time slot in the combination of the two is indicated by "D", "G", or "U". Here, "D" indicates DwPTS 42, "G" indicates GP 43, and "U" indicates UpPTS 44.

In other words, one special subframe 41 is divided into 14 time slots on the time axis, some time slots including the first 1st time slot are DwPTS 42, and the last 14th time slot The number of time slots containing UpPTS 44 and at least one time slot located between them is GP 43.

FIG. 4F is a diagram illustrating an example of the correspondence between special subframes of a TD-LTE signal and temporal changes in received power. FIG. 4F includes an upper graph, a middle table, and a lower table. The graph in FIG. 4F is a part extracted from the graph in FIG. 4C, and is an example of the waveform of the received power of the wireless signal observed by the sensor device 15, mainly from time t ₀₂ to time t ₀₅ . A portion corresponding to the special subframe from time t ₀₃ to time t ₀₄ and portions before and after that are shown. The middle table in FIG. 4F is a portion extracted from the bottom table in FIG. 4C, and shows the portion from time t ₀₂ to time t ₀₅ . The table in the lower part of FIG. 4F is obtained by transforming the diagram in FIG. 4D on the time axis so that the widths corresponding to DwPTS 42, GP 43, and UpPTS 44 correspond to the respective number of time slots.

In the graph of FIG. 4F, the period from time t ₀₃ to time t ₀₃₁ is the DwPTS 42 of the special subframe 41. Further, the period from time t ₀₃₁ to time t ₀₃₂ is GP 43 of the special subframe 41. Further, the period from time t ₀₃₂ to time t ₀₄ is UwPTS 44 of the special subframe 41.

In the graph of FIG. 4F, the period from time t ₀₃ to time t ₀₃₁ includes characteristic periods 51, 52, and 53 characterized in that the upper limit of received power is relatively high. Furthermore, in the graph of FIG. 4F, the period from time t ₀₃₁ to time t ₀₃₂ includes a characteristic period 54 characterized in that the lower limit of received power is relatively low. In the third step S03 of this embodiment, a characteristic period 54, which is a no-communication period, is detected. Note that detecting the characteristic periods 51, 52, and 53 will be described later as a second embodiment.

The ratio of the lengths of DwPTS 42, GP 43, and UpPTS 44 in the example of FIG. 4F corresponds to the first configuration #1 shown in FIG. 4E. Since it is relatively rare to change the configuration in the TD-LTE system, the wireless communication signal detection device 1 according to the present embodiment knows in advance the configuration currently used by the first wireless communication system. It's okay.

In this way, in the TD-LTE system, the position of the GP 43 in frame 4 is standardized for each configuration. Therefore, the wireless communication signal detection device 1 according to the present embodiment grasps each configuration in advance, or estimates it from the waveform of the result of observing the received power of the wireless signal in the fourth step S04, which will be described later. GP 43 as a characteristic period in each frame can be detected. Here, referring to the flowchart of FIG. 3, after the second step S02, a third step S03 is executed.

In the third step S03, the average power calculation unit 121 calculates the average value of the received power between the plurality of frames 4 among the wireless communication signals originating from the first wireless communication system, and has this average value. Calculate the average frame.

In this embodiment, in order to calculate with higher accuracy the average value of the received power observed by the relatively inexpensive sensor device 15, the average of the received power is calculated between N frames 4. FIG. 5A is a diagram for explaining an example of a target of folded average according to one embodiment.

FIG. 5A includes a graph showing an example of the result of observing received power in the second step S02. The horizontal axis of the graph in FIG. 5A indicates time t, whose unit is s. The vertical axis of the graph in FIG. 5A indicates received power s(t), and its unit is dBm.

Time t ₀ is set to match "0.00" which is the start time on the horizontal axis in FIG. 5A. Time t ₀ may be the time when observation is started. Thereafter, the period from time t ₁ to time t 4 is set every 10 ms, which is the period T of frame ₄ . Time _tE , which is the time when the observation ended, is placed after time _t4 . In other words, in the example of FIG. 5A as well, the period during which the sensor device 15 observed the received power is four times or more the period T of frame 4. In other words, in this embodiment, the coefficient N, which is an integer of 2 or more, is set to 4, and the period in which the sensor device 15 observes the received power is the coefficient of the frame period T in which GP 43, which is the characteristic period, occurs. N=4 times longer.

The average power calculation unit 121 extracts a total of four frames from the first frame _S1 to the fourth frame _S4 from the observation period of the received voltage. These four frames S ₁ to S ₄ may be consecutive in the observation results. In other words, the average power calculation unit 121 calculates the coefficient N+1=5 from the 0th time t ₀ to the fourth time t 4 consecutively every 10 ms, which is the period T of frame ₄ , from the observation period of the received voltage. A period of N=4 coefficients separated by time t ₀ to t ₄ is extracted as frames S ₁ to S ₄ of N=4 coefficients.

In this embodiment, the aliasing average is calculated for these coefficients N=4 frames S ₁ to S ₄ . FIG. 5B is a diagram illustrating a method for calculating a folded average value according to an embodiment. FIG. 5B includes four graphs corresponding to four frames S ₁ to S ₄ , respectively. Common to these four graphs, the horizontal axis represents time t. Further, the vertical axis indicates the received powers s ₁ (t) to s ₄ (t) of the corresponding frames S ₁ to S ₄ .

ここで、「ｔ」は時刻であり、「ｓ_ｎ（ｔ）」は折り返し平均であり、「Ｎ」は係数であり、「ｉ」は各フレームの番号を示す変数であり、「Ｔ」はフレーム４の周期であり、「ｓ（ｔ＋ｉＴ）」は時刻ｔ＋ｉＴで観測された受信電力である。 Here, the start time of each graph is the start time t ₀ to t ₃ of the corresponding frames S ₁ to S ₄ . That is, the graph of the first frame S ₁ starts from time t ₀ , the graph of the second frame S ₂ starts from time t ₁ , the graph of the third frame S 3 starts from time t 2, and the graph of the fourth frame S ₃ starts from time t ₂ . The graph of frame _S4 starts at time _t3 . Here, the start times of the four frames S ₁ to S ₄ to be averaged are aligned, and the received powers s ₁ (t) to s ₄ (t ) can be calculated by dividing the sum by a coefficient N=4 to calculate the folding average s _n (t). This calculation is expressed, for example, by the following mathematical formula "Math. 1".

Here, "t" is the time, "s _n (t)" is the folding average, "N" is the coefficient, "i" is a variable indicating the number of each frame, and "T" is This is the period of frame 4, and "s(t+iT)" is the received power observed at time t+iT.

FIG. 5C is a diagram illustrating an example of a calculation result of a folded average value according to an embodiment.

As described above, in order to realize the wireless communication signal detection device 1 according to this embodiment at a relatively low cost, a shift may occur in the local oscillator. Specifically, a case may be considered in which the number of samples in which received power is observed every cycle T of frame 4 is not constant. In other words, the reciprocal of the observation sampling frequency in the second step S02 may not be a divisor of the period T of frame 4. In such a case, even if the number of samples used to calculate the folded average is adjusted by adjusting various parameters, the waveform of the received power will shift. By detecting and correcting this deviation, it is possible to improve the accuracy of the folded average value s _n (t).

In this embodiment, any one of frames S ₁ to S ₄ in FIG. 5A is set as the reference frame. For convenience, frames other than the reference frame are referred to as other frames. The inner product of the received power of the reference frame and the received power of each of the different frames is calculated while appropriately shifting the start time of each of the different frames. For each of the different frames, the accuracy can be improved by adopting the shift of the start time that maximizes the inner product and calculating the folding average s _n (t) as described with reference to FIGS. 5A to 5C. can.

As an example, a method of calculating an inner product with another frame _S2 when the first frame _S1 is used as a reference frame will be described. However, these selections are merely examples and do not limit this embodiment.

6A to 6E are diagrams for explaining deviation correction according to one embodiment. FIG. 6A shows the waveform of the first frame _S1 of FIG. 5A. FIG. 6C shows the waveform of the second frame _S2 of FIG. 5A. FIG. 6B shows a waveform when the start time of the second frame _S2 in FIG. 5A is shifted before _t1 . Here, the waveform of the second frame _S2 shown in FIG. 6B may include a part of the first frame _S1 . FIG. 6D shows a waveform when the start time of the second frame _S2 in FIG. 5A is shifted after _t1 . Here, the waveform of the second frame _S2 shown in FIG. 6D may include a part of the third frame _S3 .

Here, for convenience, the waveforms of the second frame _S2 at three types of start times are shown, but in reality, the waveforms of the second frame _S2 corresponding to more types of start times are shown. The inner product of frame S1 and frame _S1 may be calculated.

For example, the inner product of the received power s ₁ (t) of the first frame S ₁ and the received power s ₂ (t) of the second frame S ₂ is calculated when one frame period T has elapsed from the start time of each frame. It is obtained by integrating the received power s ₁ (t) and the received power s ₂ (t) at each time t included in the range up to the end, and calculating the sum of the respective products. Each of the times t included in the range after one frame period T is selected for each sampling period that is the reciprocal of the sampling frequency at which the received power s ₁ (t) and the received power s ₂ (t) were observed, for example. Good too. In other words, the inner product may be calculated using the sampled values of the received power s ₁ (t) and the received power s ₂ (t).

FIG. 6E shows the inner product of the received power s ₁ (t) of the first frame S ₁ and the received power s ₂ (t) of the second frame S ₂ extracted from the received power s(t) of FIG. 5A. , is a graph showing an example of a change in the start time of the second frame _S2 due to the deviation ε. In the graph of FIG. 6E, the horizontal axis indicates the start time shift ε, and the vertical axis indicates the inner product.

In the graph of FIG. 6E, point ε ₁ , point ε ₂ and point ε ₃ are the inner product when the start time deviation ε of the second frame S ₂ is point ε ₁ , point ε ₂ and point ε ₃ respectively. It shows. In the example of the graph in FIG. 6E, the inner product becomes maximum when the shift in the start time of the second frame _S2 is ε ₂ , so the start time after correcting _the start time _t1 of the second frame S2 Correct to t ₁ +ε ₃ . Similarly, for each of the third frame _S3 and the fourth frame _S4 , a shift in the start time at which the inner product becomes the maximum is calculated, and the start time is corrected.

In this way, by using the corrected start time, it is possible to calculate the return average with high accuracy. FIG. 7 is a diagram illustrating an example of a calculation result of a highly accurate aliasing average of received power for one frame, according to an embodiment. Here, referring to the flowchart of FIG. 3, after the third step S03, a fourth step S04 is executed.

In the fourth step S04, the characteristic period detection unit 122 detects a characteristic period that occurs multiple times in the first period and has a predetermined characteristic, from among the first wireless communication signals, based on the average frame.

As an example, in this embodiment, the characteristic period is detected as follows. First, the characteristic period detection unit 122 removes noise from the waveform of the calculation result of a highly accurate folded average of one frame's worth of received power. Here, in order to make it easier to understand the effect of noise removal, a waveform based on a computer simulation will be used instead of the waveform shown in FIG. 7 based on an actual measured value of received power. FIG. 8A is a diagram illustrating an example of a waveform before noise removal according to one embodiment. More specifically, the diagram in FIG. 8A is a graph showing an example of the waveform of an average frame, which is the calculation result of the aliasing average, obtained by computer simulation. FIG. 8B is a diagram illustrating an example of a waveform after noise removal according to one embodiment.

The noise may be removed, for example, by interval averaging processing. In other words, by replacing the numerical values at each time included in the waveform of the average frame, which is the calculation result of the folded average, with the average value of the numerical values included until a predetermined period elapses from each time, the interval average frame is calculated. is obtained. Here, the predetermined period may be, for example, 5% to 10% of the period T of frame 4. Note that this process may not be performed if noise removal is not necessary. Hereinafter, a case where the interval averaging process is performed will be explained.

Next, the characteristic period detecting unit 122 performs moving averaging processing on the interval average frame after noise removal using the interval length of GP 43. That is, a moving average frame is obtained by replacing the numerical values at each time included in the waveform of the interval average frame with the average value of the numerical values included until the interval length of GP 43 has elapsed from each time.

FIG. 8C is a diagram illustrating an example of a waveform after performing a moving average according to an embodiment. The horizontal axis in FIG. 8C represents time t, and its unit is s. The vertical axis in FIG. 8C is the moving average of received power, and its unit is dBm. Point P ₂₁ included in the waveform of FIG. 8C corresponds to period T ₂₁ shown in FIG. 8B. Similarly, points P ₂₂ and P ₂₃ in FIG. 8C correspond to periods T ₂₂ and T ₂₃ in FIG. 8B, respectively. Here, point P ₂₁ , which is the minimum value point of the waveform in FIG. 8C, corresponds to period T 21, which is GP ₄₃ shown in FIG. 8B. This is because in the interval average frame shown in FIG. 8B, the received power in GP 43, which is the non-communication period, is the lowest. This indicates that the start position of GP 43 in the interval average frame can be detected by detecting the minimum value point P ₂₁ of the waveform of the moving average frame as shown in FIG. 8C. This also indicates that the starting position of GP 43 in the waveform that is the observation result of the received power can be detected.

Next, the characteristic period detection unit 122 detects the end position of the GP 43 based on the start position of the GP 43 and the known section length of the GP 43. Here, in consideration of the error, the start position and the end position may be set to positions that are approximately 80% or 90% of the theoretical values when viewed from the center of the GP 43.

After the fourth step S04, a fifth step S05 is executed.

In the fifth step S05, the threshold determining unit 123 determines a threshold of wireless communication signal power. This threshold value is used to determine whether or not the second wireless communication signal arrives superimposed with the first wireless communication signal. In this embodiment, in the sixth step S06, which will be described later, if received power exceeding this threshold is observed during the period of GP 43, which is a characteristic period of the first wireless communication system and is also a non-communication period, It is determined that the wireless communication signal No. 2 has been detected.

Therefore, the threshold value in this embodiment may be determined, for example, as a value obtained by adding a predetermined margin to the average value of the received power of the first wireless communication signal in the GP 43. Alternatively, the second step S02 may be executed multiple times to calculate the average value of the received power at the GP 43 multiple times, and the threshold value may be determined based on these multiple average values.

Further, a plurality of average values calculated in the past are stored in the storage device 13, a threshold value is determined multiple times based on these plurality of average values and stored in the storage device 13, and the correctness or wrongness of the judgment based on the plurality of threshold values is determined. The information shown may be received from the outside via the input/output interface 11 and stored in the storage device 13. In this case, a safer threshold may be determined based on the probability of an erroneous determination as a result.

Another possibility is that if the relatively inexpensive sensor device 15 has unstable clock accuracy, the detection range of the GP 43 may partially include the DwPTS or UpPTS. FIG. 9 is a diagram for explaining an error in detection accuracy of a no-communication period according to an embodiment. FIG. 9 includes a total of four graphs from the first graph G91 to the fourth graph G94. Common to these four graphs G91 to G94, the horizontal axis indicates time t, and the vertical axis indicates received power. Common to these four graphs G91 to G94, a frame 90 indicates a range that is the result of detecting GP 43. In the first graph G91, GP 43 is detected with high accuracy, but in the second graph G92, third graph G93, and fourth graph G94, DwPTS or UpPTS is partially included in the frame 90. There is. In such a case, the threshold value may be determined using only the observation results of the first graph G91, or the frame 90 in the observation results of the second graph G92, the third graph G93, and the fourth graph G94 may be used to determine the threshold value. , the threshold value may be determined after adding processing for shifting in the direction of the arrow in FIG.

After the fifth step S05, a sixth step S06 is executed.

In the sixth step S06, the determining unit 124 determines whether the wireless communication signal power exceeds a threshold value. The received power of the wireless communication signal compared here may be different from the received power used to determine the threshold value. That is, the determination may be made by comparing the currently observed received power with a threshold based on the previously observed received power.

If the determination result is "No", that is, if the received power of the wireless communication signal is below the threshold, it is considered that the received power of the wireless communication signal originating from the second wireless communication system has not been detected. It will be done. In this case, after the sixth step S06, the second step S02 may be executed again.

If the result of the determination is "Yes", that is, if the received power of the wireless communication signal exceeds the threshold, it is considered that the received power of the wireless communication signal originating from the second wireless communication system has been detected. In this case, after the sixth step S06, the seventh step S07 is executed.

In the seventh step S07, the input/output interface 11 notifies the outside of the determination result. As an example, the input/output interface 11 may notify the first base station 21 belonging to the first wireless communication system that the second wireless communication system is performing wireless communication. In response to this notification, the first base station 21 belonging to the first wireless communication system may stop using the frequency band that competes with the second wireless communication system.

As a modification of this embodiment, the wireless communication signal detection device 1 may notify the outside of the determination result after the determination result in the sixth step S06 becomes "Yes" multiple times. By doing this, the probability of false alarms can be reduced.

As a modification of the present embodiment, the wireless communication signal detection device 1 reports the determination result to the outside as "Yes" in the sixth step S06, and then the determination result becomes "No". In this case, the result of the determination may be notified to the outside. In this case, since the second wireless communication system is considered to have ended wireless communication, the first wireless communication system may resume use of the frequency band that competes with the second wireless communication system.

As a modification of this embodiment, the wireless communication signal detection device 1 may not need to perform the observation in the second step S02 and the processes from the third step S03 to the sixth step S06, for example. . In other words, according to the present embodiment, for example, the observation in the second step S02 and the processing from the third step S03 to the sixth step S06 may be performed alternately. From this point of view, it is possible to employ a cheaper arithmetic device 12 compared to the case where all processing is performed in parallel.

(Second embodiment)
In the first embodiment, a threshold value was determined based on the received power of the GP 43 during the non-communication period, and this threshold value was used to determine the detection of a wireless signal originating from the second wireless communication system. In this embodiment, the threshold value is determined based on the net power in a period other than the no-communication period, and a similar determination is made.

FIG. 10 is a diagram showing an example of the position of the DwPTS immediately before the no-communication period, which is included in the special subframe of the TD-LTE signal. As described with reference to FIG. 4E, in the TD-LTE system, the DwPTS 42 is placed immediately before the GP 43. Using this configuration, if the GP 43 can be detected, the DwPTS 42 immediately preceding it can also be detected. As a result, it is possible to determine the threshold value that serves as the criterion for the determination in the sixth step S06, based on the relatively high received power in the characteristic periods 51, 52, and 53 shown in FIG. 4F.

Here, the interval average for the entire DwPTS 42 placed immediately before the GP 43 may be calculated, or the section average of the entire DwPTS 42 placed immediately before the GP 43 may be calculated as shown in FIG. The interval average may be calculated by extracting only the characteristic periods 51, 52, and 53. As a method for extracting the portions corresponding to the characteristic periods 51, 52, and 53, for example, a threshold different from the threshold used for the determination in the sixth step S06 is determined in advance, and the received power exceeds this different threshold. Extraction may be performed on the condition that

Although the invention made by the inventor has been specifically explained based on the embodiments above, the present invention is not limited to the embodiments described above, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say. Furthermore, the features described in the above embodiments can be freely combined within a technically consistent range.

1 Wireless communication signal detection device 10 Bus 11 Input/output interface 12 Arithmetic device 121 Average power calculation section 122 Characteristic period detection section 123 Threshold value determination section 124 Judgment section 13 Storage device 14 External storage device 141 Recording medium 15 Sensor device 21 First base station 22, 22A, 22B First terminal 31 Second base station 32 Second terminal 4 Frame 400 to 409 Subframe 41 Special subframe 42 DwPTS (downlink pilot time slot)
43 GP (guard period)
44 UpPTS (Uplink Pilot Time Slot)
51, 52, 53, 54 Characteristic period 90 frames G91 to G94 graph P ₂₁ to P ₂₃ points S ₁ to S ₄ frames s ₁ to s ₄ received power T period T ₂₁ to T ₂₃ period t ₀ to t ₄ time t ₀₀ ~t ₁₀ time t ₀₃₁ , t ₀₃₂ time t _E time

Claims (8)

a sensor device that observes received power of a wireless communication signal included in a predetermined frequency band;
Based on the observation result of the received power, the length of the first period of the received power derived from the first wireless communication signal included in the wireless communication signal and having periodicity according to a predetermined first period. an average power calculation unit that calculates an average frame having an average value among a plurality of frames;
Characteristic period detection that detects a characteristic period that occurs multiple times in the first wireless communication signal, occurs at least once in each first period , and has a predetermined characteristic, based on the average frame. Department and
Detection or non-detection of a second wireless communication signal that is included in the wireless communication signal and that is different from the first wireless communication signal is based on the observation result and the received power in the characteristic period of the average frame. A wireless communication signal detection device comprising: a determination unit that makes a determination. The wireless communication signal detection device according to claim 1,
N is an integer of 2 or more,
The sensor device observes the received power over an observation period longer than N times the first period,
The average power calculation unit includes:
extracting N frames separated by N+1 consecutive times at intervals of the first period from the observation period;
selecting one frame from the N frames as a reference frame;
For each of the N frames other than the reference frame, calculate the inner product of the received power in each of the different frames and the received power in the reference frame,
The wireless communication signal detection device calculates the average frame by averaging received power between the reference frame and each of the other frames whose break times are shifted so that the respective inner products are maximized. The wireless communication signal detection device according to claim 1 or 2,
The first wireless communication signal includes a period of no communication that occurs periodically in the first period,
The length of the no-communication period is known;
The characteristic period detection unit is
Detecting the position of the no-communication period in the average frame based on the minimum value of a moving average according to the length of the no-communication period of the average frame,
A wireless communication signal detection device that detects the characteristic period based on the position of the no-communication period. The wireless communication signal detection device according to claim 3,
The characteristic period is the no-communication period. The wireless communication signal detection device. The wireless communication signal detection device according to claim 3,
The characteristic period is a communication period immediately before the no-communication period. The wireless communication signal detection device. The wireless communication signal detection device according to any one of claims 1 to 5,
further comprising a threshold determining unit that determines a threshold based on the average value of the received power in the characteristic period of the average frame,
The determination unit determines whether to detect the second wireless communication signal if the received power during the characteristic period of the observation result exceeds the threshold. The wireless communication signal detection device according to any one of claims 1 to 6,
The wireless communication signal detection device further includes an interface that notifies the result of the determination to the outside. Observing the received power of a wireless communication signal included in a predetermined frequency band;
Based on the observation result of the received power, the length of the first period of the received power derived from the first wireless communication signal included in the wireless communication signal and having periodicity according to a predetermined first period. calculating an average frame having an average value between the plurality of frames;
Detecting, based on the average frame, a characteristic period that occurs multiple times in the first wireless communication signal, occurs at least once in each first period , and has a predetermined characteristic;
Detection or non-detection of a second wireless communication signal that is included in the wireless communication signal and that is different from the first wireless communication signal is based on the observation result and the received power in the characteristic period of the average frame. and determining a wireless communication signal detection method.

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