JP5697092B2 - Reception discrimination system - Google Patents

Description

  When a plurality of wireless communication networks coexist in a communication space, the reception determination system is mounted on at least one wireless communication network and determines whether or not a wireless signal is received by another wireless communication network.

  Conventionally, standardization of a wireless communication system using TV White Space (TVWS) has been promoted (see, for example, Patent Document 1). A secondary system different from the primary system such as TVWS may exist in the same communication space. When wireless communication is actually performed in the secondary system, it is necessary to prevent communication interference with the primary signal in the primary system. First, the primary signal must be detected with high accuracy. Conventionally, a method for detecting a primary signal with high accuracy has not been studied so much until a system using such a TVWS is proposed.

  Actually, the success or failure of detection of the primary signal greatly depends on the setting of the threshold value at the time of signal detection. However, various noises may exist in a situation where many wireless communication systems coexist in recent years, and signal detection accuracy is greatly affected by noise fluctuations inside the system. Further, as interference with adjacent wireless communication systems has become widespread, there has been a limit in the conventional threshold setting method for signal detection. In particular, when it is necessary to detect a low-level primary signal with high accuracy, the conventional threshold setting method for signal detection has a limit due to noise fluctuation inside the wireless system for measurement.

  For example, when the noise level is low, the signal can be detected without omission by setting the signal detection threshold low, and Pfa {= (when it is determined that the signal is detected) / (actually If no signal is present)} can be suppressed to an ideal line. Pfa is a ratio at which it is determined that the signal to be detected is actually detected in the fact that the signal to be detected is not actually transmitted. That is, this Pfa is also called a false alarm ratio, and reflects the utilization efficiency of an empty channel where no other wireless communication network is used. When this Pfa is set low, high utilization efficiency can be realized.

  On the other hand, when the noise level is high, it is necessary to set the signal detection threshold value high in order not to detect such noise. However, if this signal detection threshold is set too high, if the noise level is low, the actual primary signal may or may not be detected, and it is determined that Pd {= (signal has been detected. Case) / (if the signal actually exists). Here, Pd is a ratio at which it is determined that the signal to be detected is actually detected on the assumption that the signal to be detected is actually transmitted.

  That is, if the threshold value is set by Pfa on the basis of the case where the noise level is low, Pfa becomes high when the noise fluctuates high. Conversely, if the threshold is set based on the case where the noise level is high, Pd becomes low when the noise fluctuates low. When there are many fluctuations in the noise level, there is a limit to the method of setting one threshold value and using it constantly as in the prior art.

Japanese Patent Application No. 2010-28383

  That is, the conventional signal detection threshold setting method has a problem that it cannot satisfy the detection accuracy required in various wireless communication systems. For this reason, it is expected that by improving the detection signal threshold setting method, it is possible to detect power with a low dBm and increase the frequency selection tolerance.

  Therefore, in order to solve the above-described problems, the present invention is a reception discrimination system capable of increasing frequency selection tolerance while improving detection accuracy in detecting a primary signal such as a TV signal. The purpose is to propose.

In order to solve the above-described problem, a reception determination system to which the present invention is applied is implemented in at least one wireless communication network when a plurality of wireless communication networks coexist in a communication space, and is wirelessly transmitted by another wireless communication network. In a reception discrimination system for discriminating whether or not a signal is received, detection means for detecting a noise level over a predetermined time while controlling not to receive a radio signal from another radio communication network, and simultaneously with the detection, The reception value calculation means for calculating the reception value based on a predetermined algorithm based on the noise level, and the noise level detected by the detection means is grouped in a plurality of stages from the minimum value to the maximum value, Based on the received value calculated by the received value calculating means and a predetermined false alarm ratio A table creating means for creating a threshold value reference table in which a threshold value is assigned to each group and a wireless signal from the other wireless communication network when actually determining whether or not a wireless signal is received by the other wireless communication network The noise level at the time of the determination is detected while controlling so as not to receive the signal, and a group corresponding to the detected noise level is selected from the threshold reference table created in advance by the table creating means and assigned to the selected group. Threshold value specifying means for specifying the threshold value, and the received value calculation means calculates the received value based on the algorithm when the radio signal from the other radio communication network is actually controlled to be receivable. By newly calculating and comparing with the threshold specified by the threshold specifying means, And discriminates whether the received line signal.

A reception determination system to which the present invention is applied is implemented in at least one wireless communication network when a plurality of wireless communication networks coexist in a communication space, and receives whether a wireless signal is received by another wireless communication network. In the discrimination system, control is performed so as not to receive a radio signal from another radio communication network, and detection means for detecting a noise level, and reception based on an algorithm predetermined based on the noise level simultaneously with the detection. A reception value calculation means for calculating a value, and a threshold value specifying means using the reception value calculated by the reception value calculation means as a threshold, the reception value calculation means receives a radio signal from the other wireless communication network. When the reception value is actually controlled and the reception value is newly calculated based on the above algorithm To, by comparing the specified threshold by the threshold specifying unit, characterized by determining the presence or absence of reception of the wireless signal.

  According to the present invention having the above-described configuration, an optimum threshold value can be set in relation to actual noise. Therefore, when a communication space is shared with another wireless communication system, the other wireless communication system Can be detected with high accuracy, and at the same time, the fact that the other wireless communication system is not transmitting can also be determined with high accuracy.

1 shows a configuration example of a reception determination system to which the present invention is applied. It is a figure for demonstrating the operation example of the reception discrimination | determination system to which this invention is applied. It is the figure which expanded and displayed the range of R1-R2 of the received value corresponding to the group of N1-N2 shown in FIG. It is a flowchart until a threshold value reference table is created. 10 is a flowchart for actually determining whether or not a wireless signal is received by another wireless communication network. It is a figure which shows the example which selects an appropriate threshold value reference table based on the adaptability with the conditions defined beforehand. It is a flowchart which sets the threshold value in performing reception discrimination | determination in real time. It is another flowchart which sets the threshold value in performing reception discrimination | determination in real time. It is a flowchart which creates the threshold value reference table which also considered environmental noise.

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

  FIG. 1 shows a configuration example of a reception discrimination system 1 to which the present invention is applied. The reception determination system 1 is mounted on at least one of the wireless communication networks 10a and 10b. In the following example, a case where the wireless communication network 10a is implemented will be described as an example. The wireless communication network 10a includes a plurality of terminal devices 2a. The reception determination system 1 is mounted on the terminal device 2a.

  In the above-described reception determination system 1 shown in FIG. 1, the case where the wireless communication networks 10a and 10b are configured is illustrated as an example. However, the present invention is not limited to this, and three or more wireless communication networks 10 are included. Of course, it may consist of.

  The terminal device 2 includes, for example, a notebook personal computer (notebook PC), various portable information terminals such as a mobile phone, and the like. The terminal device 2 performs wireless packet communication with another terminal device 2 at least in the WPAN. Any one of the terminal devices 2 may be responsible for controlling the entire network.

  In the reception determination system 1 installed in the wireless communication network 10a, the presence / absence of reception of a wireless signal in the other wireless communication network 10b is determined. If a wireless signal can be received in another wireless communication network 10b, it is possible to shift to processing for preventing interference with the wireless signal.

Next, the operation of the reception determination system 1 to which the present invention is applied will be described. First, in the present invention, a noise level is detected over a predetermined time while controlling not to receive a radio signal from another radio communication network 10b. As shown in the lower part of FIG. 2, an example in which the noise level is detected in a predetermined time from t ₁ to t ₂ is shown. The reception determination system 1 calculates a reception value based on an algorithm determined in advance for the noise level. The upper part of FIG. 2 shows the calculation result of the received value. Since the received value is calculated by performing a certain algorithm on the noise level, the time-series tendency corresponds to the noise level. Any algorithm may be used. For example, the received power may be used as it is as the received value.

  Next, in the reception discrimination system 1, the detected noise level in FIG. 2 is grouped into a plurality of stages from the minimum value to the maximum value. In the example of FIG. 2, Nmin to N1, N1 to N2, N2 to N3,..., Ni to Nmax are grouped.

  Next, a threshold value is assigned to each of the groups Nmin to N1, N1 to N2, N2 to N3,..., Ni to Nmax. This threshold is determined based on the received value and Pfa. Here, Pfa {= (when it is determined that a signal is detected) / (when there is no actual signal)} can be suppressed to an ideal line. Pfa is a ratio at which it is determined that a signal to be detected is actually detected in a situation where a signal to be detected is not actually transmitted, and is also referred to as a false alarm ratio. If Pfa = 0.1, as a result of setting the threshold value high, it is indicated that 10% of cases are determined to have been detected even though no signal actually exists. This Pfa is preset in the reception discrimination system 1.

  The threshold is determined based on this Pfa and the actual received value. FIG. 3 is an enlarged view of the range of received values R1 to R2 corresponding to the groups N1 to N2 shown in FIG. 2, but if Pfa is 0.1, the threshold value is in the range of R1 to R2. The line is 10% from the top. In this way, threshold values are similarly determined based on Pfa for the range of received values corresponding to all noise level groups. As a result, a threshold reference table THtab as shown in Table 1 below is finally created.

  That is, in the present invention, the noise level is detected and recorded for a predetermined time in a state where control is performed so as not to receive the radio signal of the other radio communication system 10b, and the received value is calculated by using a predetermined algorithm. To do. At this time, even if the noise level is various, the minimum value Nmin and the maximum value Nmax are set so as to be able to cope with the noise level, and the noise enters within the range (Nmin ≦ noise ≦ Nmax). Then, this noise range is divided into small ranges (M). Furthermore, in each noise group, threshold values TH1, TH2,..., THM are set using Pfa.

  FIG. 4 shows a flow until the threshold reference table THtab is created. In step S11, the system is operated with the switch turned off. The switch-off state here refers to a case where the configuration of an isolator or the like that receives radio waves from the outside is switched off. As a result, no wireless signal from the other wireless communication network 10b can be received, and only noise in its own system can be detected. That is, while configuring the wireless communication network 10a and switching off the means for receiving radio waves from the outside of the terminal device 2a in which the reception determination system 1 is mounted, wireless signals from other wireless communication networks 10b are not received. Is doing so to control.

Next, in step S12, noise is measured and this is set as Ni. The received value (Rni) is calculated using a preset algorithm. Such calculation may be performed simultaneously with detection of the noise level. When the process proceeds to step S13, the measured Ni and the received value Rni obtained by using the algorithm are recorded in the buffer. Next, in step S14, it is compared whether or not t is less than T. If t is less than T, the process proceeds to step S15. If t is not less than T, that is, if t is equal to or greater than T, the process proceeds to step S16. In step S15, a _{value obtained} by adding t0 to t is newly defined as t, and the process returns to step S12 described above. This t ₀ is an arbitrary positive number. In step S16, the threshold reference table THtab shown in Table 1 is created.

  Thus, in the present invention, noise measurement is performed, and the noise level Ni and the algorithm Ri used are recorded in the buffer every time in step S13. Incidentally, the noise detection period is optimized in advance based on both the requirement of the communication standard adopted by the reception determination system 1 and the tolerance of the reception determination system 1 core. As shown in Table 1, the noise to be newly acquired in the future can be caught in any range from the minimum value Nmin to the maximum value Nmax. That is, there are various new acquisitions in the future, but it is possible to cover them without leaking, and it is possible to set a threshold value corresponding to them.

  When the creation of the threshold reference table THtab is completed in this way, the presence / absence of reception of a wireless signal by another wireless communication network is actually determined.

  In step S21 shown in FIG. 5, the switch is first turned off. As a result, no wireless signal from the other wireless communication network 10b can be received, and only noise in its own system can be detected. Next, in step S22, the noise level is detected. The detection of the noise level is performed only to confirm how much noise is generated in the own system at the actual determination time. Let n be the noise level detected during this discrimination.

  Next, the process proceeds to step S25, where a threshold THcorr used for determination of the reception level is searched. This threshold value search is performed by referring to the threshold value reference table THtab. That is, the group corresponding to the noise level (n) is selected from the threshold value reference table THtab, and the threshold value THcorr assigned to the selected group is specified. For example, in the example of Table 1, if the noise level (n) is N1 <n ≦ N2, the threshold THcorr is TH2, and if the noise level (n) is N2 <n ≦ N3, the threshold THcorr Is TH3.

  Moreover, it transfers to step S23 from step S22 and a switch is set to ON. As a result, the wireless communication network 10a is controlled to be able to receive wireless signals from the other wireless communication network 10b. Next, the process proceeds to step S24, and a received value is calculated by using an algorithm. This algorithm is basically the same as the algorithm described above. Such calculation may be performed simultaneously with detection of the noise level. The threshold value is based on the received value Rni calculated through the algorithm. In order to match it, it is necessary to convert this newly received signal to the received value Rx using the same algorithm. Because. Next, the process proceeds to step S26, and the newly acquired received value Rx is compared with the threshold value THcorr specified in step S25. If the received value is equal to or greater than the threshold value THcorr, it is determined that a wireless signal from another wireless communication system 10b has been received. If the received value is less than the threshold value THcorr, it is determined that a radio signal from another radio communication system 10b has not been received. As described above, the series of reception determination operations is completed by completing step S26.

  The present invention is not limited to the embodiment described above. For example, as shown in Table 2, a plurality of threshold value reference tables THtab1 and THtab2 may be created in advance. In the threshold reference tables THtab1 and THtab2, the same groups Nmin to N1, N1 to N2, N2 to N3,..., Ni to Nmax are set. Different from THtab2. Such a plurality of types of threshold reference tables THtab1 and THtab2 are created in advance, and reception determination is performed based on the flow shown in FIG.

  In step S31, the switch is first turned off. As a result, no wireless signal from the other wireless communication network 10b can be received, and only noise in its own system can be detected. Next, in step S32, the noise level (n) is detected as in step S22 described above. The process proceeds to step S33 and the switch is set to ON. As a result, the wireless communication network 10a is controlled to be able to receive wireless signals from the other wireless communication network 10b. In step S34, actual reception is started, and reception information is acquired from the received content. Then, the compatibility between the received information and a predefined condition is calculated or determined. An example of the reception information is reception power, and an example of the predefined condition is an allowable range of the reception power. That is, it is determined whether or not the received power is actually matched within a predefined allowable range of received power.

  Next, the process proceeds to step S35, and one of the threshold reference tables THtab1 and THtab2 shown in Table 2 is selected according to the actually determined suitability. For example, the threshold value reference table THtab1 may be selected when the received power is within a predefined allowable range of received power, and the threshold value reference table THtab2 may be selected when the received power is outside the allowable range.

  Next, the process proceeds to step S36, and the received value Rx is calculated by using an algorithm. Such calculation may be performed simultaneously with detection of the noise level.

  In step S37, similarly to step S25 described above, the threshold THcorr used for determination of the reception level is searched. This threshold value search is performed by referring to the threshold value reference table THtab selected in step S35. That is, the group corresponding to the noise level (n) is selected from the threshold value reference table THtab, and the threshold value THcorr assigned to the selected group is specified. This specific method is the same as in step S25.

  Next, the process proceeds to step S38, and the received value newly acquired in step S36 is compared with the threshold value THcorr specified in step S37. If the received value is equal to or greater than the threshold value THcorr, it is determined that a wireless signal from another wireless communication system 10b has been received. If the received value is less than the threshold value THcorr, it is determined that a radio signal from another radio communication system 10b has not been received. As described above, a series of reception determination operations is completed by completing step S38.

  FIG. 7 shows an example in which a threshold for performing reception determination is set in real time. In step S41, the switch is first turned off. As a result, no wireless signal from the other wireless communication network 10b can be received, and only noise in its own system can be detected. Next, in step S42, the noise level (n) is detected. However, the detection of the noise level in step S42 does not have to be performed for a long time, and may be a short period before performing the reception determination. At the same time, an actual reception value Rn is obtained based on the noise level by using an algorithm. The received value is set as a threshold value.

  Next, the process proceeds to step S43, where the switch is turned on. Next, the process proceeds to step S44, where reception is performed, and a reception value Rx is calculated by using an algorithm. Of course, this algorithm corresponds to the algorithm described above. Then, the reception value Rx calculated in step S44 is compared with the threshold value Rn obtained in step S42, and reception determination as described above is performed.

  As a result, the threshold value is acquired in real time, and the received value can be immediately determined by comparing the received value with the received value.

  At this time, if Rn> TH0, the threshold value = TH0 may be set, and otherwise, the threshold value = Rn may be set. Here, TH0 is a predetermined value determined in advance. Setting Rni = threshold results in Pfa = 0. At this time, if the value of Pfa is to be set upward, for example, if it is desired to set Pfa = 0.1, if Rn> THx (here, x = 0.1), the threshold is set to THx instead of Rn. Here, THx (here, x = 0.1) is calculated based on Pfa = 0.1 determined in advance.

  The flowchart shown in FIG. 8 is also an example in which a threshold for performing reception determination is set in real time. In FIG. 8, steps S41 to S45 are the same as those in FIG. 7 described above, and hence the description below is omitted by citing the description.

  After completion of step S45, variable j is compared with constant J in step S46. As a result, if j <J, the process proceeds to step S47. If j <J is not satisfied, the process proceeds to step S41 and the above-described processing is repeated. When the process proceeds to step S47, j + 1 is newly defined as j, and the process proceeds to step S44 again.

  That is, in the example shown in FIG. 8, after setting the threshold value once, the reception value is calculated several times in succession, the reception value is calculated up to a certain number of times, the calculated reception value, and the threshold value The threshold value is set again after repeating the discrimination process by comparison with.

  That is, in this method based on the real time threshold, the received signal from the other radio communication system 10b is blocked for a while in the phase A). Then, a threshold value is calculated in the detection algorithm. Also, in phase B), when reception from another wireless communication system 10b is performed, a detection algorithm is executed to determine whether or not it is greater than or equal to a threshold value.

  When considering system characteristics (noise diversity) and / or environmental conditions (interference diversity), the above two phases A) and B) are executed alternately as A) → B) → A) → B) Or after A) is executed once, B) is repeated several times, and after A) is executed once again, B) is repeatedly performed several times. May be.

  That is, when the determination is made based on the threshold value updated in advance, the threshold value is always fixed to one type, but with this real-time method, the threshold value can be periodically updated.

  Note that the present invention assumes that control is performed so as not to receive a radio signal from another radio communication network 10b, and that only the noise in its own system is detected by turning the switch off. However, the present invention is not limited to this. For example, the control so as not to receive a radio signal from another radio communication network 10b may be performed so that environmental noise can be detected by executing a flow described below.

  First, in step S61, the wireless communication network 10a accesses a database (not shown). In this database, for example, the wireless communication state of various wireless communication networks 10, such as channel usage status, is recorded as needed. Therefore, by accessing this database, it can be confirmed whether or not the other wireless communication system 10b is currently performing wireless communication using the channel. Next, the process proceeds to step S62, where it is determined whether another wireless communication system 10b is currently performing wireless communication using a channel. If the other wireless communication system 10b is not currently performing wireless communication using a channel, the process proceeds to step S12, and if the other wireless communication system 10b is currently performing wireless communication using a channel. Control goes to step S63.

When the process proceeds to step S12, the noise is measured and set as Ni. The noise level measured here includes not only the noise in the system but also the noise of the environment received from the outside. Based on these noise levels, a received value is calculated using a preset algorithm. When the process proceeds to step S13, the measured Ni and the received value obtained by using the algorithm are recorded in a buffer. Next, in step S64, a _{value obtained} by adding t0 to t is redefined as t, and whether or not t is less than T is compared in step S65. If t is less than T, the process proceeds to step S61 and the above-described processing is repeated. If t is not less than T, that is, if t is equal to or greater than T, the process proceeds to step S66. When the process proceeds to step S63, the process waits for the period t0, and then proceeds to step S61 again to repeat the above-described processing. When the process proceeds to step S66, a threshold reference table THtab as shown in Table 1 is created.

  According to such a method, it is possible to create a threshold reference table THtab that takes into account not only noise in the system but also environmental noise. Even when processing for actually specifying the threshold THcorr is performed, instead of turning off the above-described switch, the database is accessed and the other wireless communication system 10b is not currently using the channel. By performing the reception after confirming the above, it is possible to detect not only the noise in the own system but also the environmental noise.

DESCRIPTION OF SYMBOLS 1 Reception discrimination | determination system 2 Terminal device 10 Wireless communication network

Claims (5)

When a plurality of wireless communication networks coexist in a communication space, the reception determination system is mounted on at least one wireless communication network and determines whether or not a wireless signal is received by another wireless communication network.
Detecting means for detecting a noise level over a predetermined time while controlling not to receive a wireless signal from another wireless communication network;
A received value calculating means for calculating a received value based on an algorithm determined in advance based on the noise level simultaneously with the detection;
The noise level detected by the detection means is grouped into a plurality of stages from the minimum value to the maximum value, and based on the reception value calculated by the reception value calculation means and a predetermined false alarm ratio. A table creation means for creating a threshold reference table in which a threshold is assigned to each group;
When actually determining whether or not a wireless signal is received by another wireless communication network, the noise level at the time of the determination is detected while controlling not to receive a wireless signal from the other wireless communication network. A threshold value specifying unit for selecting a group corresponding to the noise level from a threshold value reference table created in advance by the table creating unit, and specifying a threshold value assigned to the selected group;
The received value calculating means newly calculates a received value based on the algorithm when the wireless signal from the other wireless communication network is actually controlled to be receivable, and is specified by the threshold specifying means. A reception determination system, wherein the presence / absence of reception of the wireless signal is determined by comparison with a received threshold value. 2. The reception according to claim 1, wherein the detection means and the threshold value specifying means control so as not to receive a radio signal from another radio communication network by switching off an external radio wave receiving means. Discriminating system. The detection means detects a noise level for a predetermined time in a time zone in which a wireless communication state recorded by another wireless communication network is recorded and wireless communication by another wireless communication network is not performed. The reception determination system according to claim 1 , wherein the threshold value specifying means detects a noise level at the time of determination. The table creating means creates a plurality of types of threshold value reference tables having different threshold values assigned to the same group,
The reception determination according to any one of claims 1 to 3, wherein the threshold value specifying unit selects any one of the threshold value reference tables according to suitability between the reception information and a predetermined condition. system. When a plurality of wireless communication networks coexist in a communication space, the reception determination system is mounted on at least one wireless communication network and determines whether or not a wireless signal is received by another wireless communication network.
Detecting means for detecting a noise level while controlling not to receive a wireless signal from another wireless communication network;
A received value calculating means for calculating a received value based on an algorithm determined in advance based on the noise level simultaneously with the detection;
Threshold value specifying means using the received value calculated by the received value calculating means as a threshold value,
The received value calculating means newly calculates a received value based on the algorithm when the wireless signal from the other wireless communication network is actually controlled to be receivable, and is specified by the threshold specifying means. A reception determination system, wherein the presence / absence of reception of the wireless signal is determined by comparison with a received threshold value.

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