JP2012034164A - Radio wave sensor and data transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radio wave sensor and a data transmission method that enable efficient data collection for determining conditions of a radio wave (broadcast wave) to be sensed.SOLUTION: A radio wave sensor performs data transmission using a time slot assigned to itself from a plural of time slots provided by dividing a carrier frequency used for transmitting data to a data collection device. The radio wave sensor comprises: a receiving unit for receiving a radio wave in a predetermined frequency band; an operation unit for computing (measuring and analyzing) the spectrum of a radio wave received by the receiving unit during a pause period of radio transmission to which the time slot is not assigned; and a transmission unit for reporting data outputted from the operation unit as a result of the computing to the data collection device using the assigned time slot.

Description

  The present invention relates to a radio wave sensor and a data transmission method used for a wireless sensor network, for example.

  One of the wireless sensor networks is a cognitive radio system. This cognitive radio system collects and uses a plurality of radio sensors that receive radio waves of a predetermined frequency, measure and analyze the spectrum of the received radio waves, and spectrum information of radio waves measured and analyzed by each radio sensor. And a data integration device for determining a power frequency.

  When message transmission between the radio wave sensor and the data integration device is performed wirelessly, if radio signal contention or collision occurs, throughput decreases, so that radio signal contention or collision is unlikely to occur. TDMA (Time Division Multiple Access) It is conceivable to use a method.

Tsumura, Higaki “TDMA slot allocation method based on multi-hop route” Information Processing Society of Japan Research Report. EIP, [Electronic Intellectual Property / Social Infrastructure] 2007 (91), 73-78, 2007-09-20

  However, in the case of the TDMA system, each radio wave sensor is a period during which no time slot is allocated and wireless access is not performed, and during such a period, calculations such as measurement and analysis are performed during a certain period after the start of radio wave detection. However, since this calculation period is short, high quality data may not be obtained.

  The present invention has been made to solve such a problem, and an object thereof is to provide a radio wave sensor and a data transmission method capable of collecting high-quality data for determining the status of radio waves to be detected. .

In order to solve the above problems, a radio wave sensor according to an embodiment of the present invention is a radio wave sensor that performs data transmission using an assigned time slot among a plurality of time slots obtained by dividing a carrier frequency used for data transmission. A receiving unit that receives radio waves in a predetermined frequency band, a calculation unit that measures and analyzes a spectrum of the radio waves received by the receiving unit using an idle period to which the time slot is not allocated, and the calculation A transmission unit that transmits the calculation result of the unit in the assigned time slot.
In the data transmission method according to the embodiment of the present invention, the radio wave sensor transmits data using a time slot assigned to itself among a plurality of time slots obtained by dividing a carrier frequency used for transmitting data to a data integration device. In the data transmission method, the data transmission method includes: a step of receiving the radio wave of a predetermined frequency band by the radio wave sensor; and a radio activity pause period in which the time slot is not assigned, A step of calculating a spectrum, and a step of reporting data obtained as a result of calculation by the radio wave sensor to the data accumulator in an assigned time slot.

  According to the present invention, it is possible to provide a radio wave sensor and a data transmission method that can collect high-quality data for determining the status of radio waves to be detected.

It is an arrangement plan of a cognitive radio system of an embodiment. It is a schematic block diagram of a cognitive radio system. It is a functional block diagram of each sensor. It is a functional block diagram of a data integration device. It is a figure which shows the structure of the data frame of a TDMA system. It is a timing chart which shows the 1st example of operation of a plurality of sensors. It is a timing chart which shows the 2nd example of operation of a plurality of sensors. It is a general timing chart (comparative example) when a plurality of sensors perform wireless communication by the TDMA method.

  Hereinafter, a cognitive radio system according to an embodiment will be described in detail with reference to the drawings. As shown in FIGS. 1 and 2, the cognitive radio system of this embodiment includes a plurality of radio wave sensors 2 a to 2 that are distributed to receive radio waves (broadcast waves) broadcast (transmitted) from the radio tower 1 of the primary system. 2e (hereinafter referred to as sensors 2a to 2e) and the spectrum data of the radio waves detected and calculated (measured and analyzed) by each sensor 2a to 2e to collect the radio system status (quality, etc.) of the primary system The data accumulating device 3 determines whether or not the target frequency is usable and determines the frequency to be used. A cognitive radio system is one of wireless sensor networks. The plurality of sensors 2a to 2e are positioned so as to be scattered, for example, in office buildings or commercial facilities. The radio tower 1 is installed outdoors. The sensors 2a to 2e are also referred to as wireless sensors.

  As illustrated in FIG. 3, each of the sensors 2 a to 2 e includes a reception unit 22, a calculation unit 23, and a transmission unit 26. The calculation unit 23 includes a measurement unit 24 and an analysis unit 25.

  The receiving unit 22 receives a radio wave (for example, a radio wave such as a television broadcast) in a predetermined frequency band, for example, a UHF frequency band (300 MHz to 3000 MHz (3 GHz)) through the antenna 21. This frequency band is called a sensing channel (first channel). That is, the sensing channel is a channel that scans the frequency band to be recognized.

  The calculation unit 23 calculates (measures and analyzes) the spectrum of the radio wave received by the reception unit 22 during the radio activity suspension period to which no time slot is allocated. More specifically, the calculation unit 23 calculates (measures and analyzes) the spectrum of the radio wave received by the reception unit 22 during a period excluding the reporting period due to the time slot in the radio activity suspension period.

  For example, the calculation (measurement and analysis) is performed in a period until the time of the time slot assigned to itself is reached after the detection of the radio wave is started. In addition, calculation of data to be loaded in the next frame is performed during a period of radio activity suspension after data is reported in the time slot. The wireless activity suspension period is called the idle period.

  The measuring unit 24 measures the intensity of the radio signal received by the receiving unit 22. The radio wave spectrum is an intensity distribution arranged in the order of the wavelength of the signal that repeats the amplitude of a certain period. The analysis unit 25 obtains a radio wave spectrum by analyzing an intensity distribution in which the radio signal intensity measured by the measurement unit 24 is arranged in order of wavelength.

  The transmission unit 26 transmits the data of the calculation result calculated by the calculation unit 23 (radio wave spectrum data, the identifier of the sensor itself, etc.) from the data accumulation device 3 in the time slot assigned to itself through the antenna 27. This is reported to the data accumulation device 3. The transmission unit 26 performs wireless transmission using a communication band of a wireless system such as PHS.

  Wireless access between the sensors 2a to 2e and the data integration device 3 is performed by the TDMA method. A channel used for this wireless access is called a sensor channel (second channel). In the TDMA system, each of the sensors 2a to 2e divides the carrier frequency used for transmitting data to the data accumulating device 3 into a plurality of time slots, and among the divided time slots, the data accumulating device 3 Data transmission is performed using the assigned time slot.

  As illustrated in FIG. 4, the data accumulation device 3 includes a reception unit 32, an accumulation unit 33, a memory 34, a determination unit 35, and the like.

  The receiving unit 32 receives data wirelessly transmitted from each of the sensors 2a to 2e by the TDMA method. The accumulating unit 33 collects data from each of the sensors 2 a to 2 e received by the receiving unit 32, combines the collected data, and stores the synthesized data in the memory 34.

  The memory 34 stores data such as the radio wave status (quality, etc.) of the primary system synthesized by the accumulation unit 33. The memory 34 stores in advance threshold data 7 for determining the radio wave status (quality and the like) of the primary system, position data associated with the identifiers of the sensors 2a to 2e, and the like. The memory 34 functions as a work area for data processing by the accumulating unit 33 and the determining unit 35.

  The determination unit 35 compares the data of the primary system radio wave status (quality, etc.) stored in the memory 34 by the accumulation unit 33 with threshold data to determine whether or not the frequency of the radio wave to be detected exists. The frequency to be used is determined according to the determination result.

  For example, if the value of data such as radio wave status (quality, etc.) is higher than the threshold data, it is determined that the frequency of the radio wave to be detected (the frequency of the primary system radio wave) is being used, and the frequency band is excluded Determine the frequency to use the selected frequency band.

  Also, if the value of data such as radio wave status (quality, etc.) is lower than the threshold data, it is determined that the frequency of the radio wave to be detected (the frequency of the primary system radio wave) is not being used, and that frequency band is used. Determine the frequency to be used.

  Here, a data frame transmitted and received between the data accumulation device 3 and each of the sensors 2a to 2e will be described with reference to FIG.

  As shown in FIG. 5, data wirelessly transmitted by the TDMA method is provided with an initial integration period 52 and a plurality of time slots 53 for reporting in a time interval of a plurality of beacon frames 51. Each beacon frame 51 includes a command for instructing a specific action, information on an accumulation period for each sensor, and other information necessary for synchronization.

  Hereinafter, the operation of the cognitive radio system will be described with reference to FIGS. In order to make the explanation easier to understand, the operation of the three sensors 2a to 2c among the sensors 2a to 2e will be described. First, a first operation example will be described.

  In this system, the data accumulation device 3 operates as a control node for controlling wireless access by a plurality of distributed sensors 2a to 2c.

  The data accumulation device 3 transmits a beacon frame 51 including information for assigning slots to the sensors 2a to 2c before the sensors 2a to 2c start detecting the radio wave spectrum.

  When each sensor 2a-2c receives a beacon frame 51 including time slot allocation information, each sensor 2a to 2c reads out its own time slot allocation information from the beacon frame 51, and reports the result of the calculation in the allocated time slot. Set the time and start detecting radio waves.

  That is, each of the sensors 2a to 2c starts radio wave sensing, and reports after using each time slot (t1, t2, t3 in FIG. 6) assigned to itself.

  Normally, as in the comparative example of FIG. 8, the integration period t from when each of the sensors 2a to 2c starts detection of radio waves to perform calculation and obtains the calculation result is the same time (constant). Since there is a limit to the time from the start of detection until the calculation result is obtained, there are cases where a certain level of quality cannot be obtained as the detection result (calculation result) of each sensor.

  Therefore, in the first operation example, as shown in FIG. 6, for example, the sensor 2a immediately starts the detection of the radio wave and immediately performs the calculation during the first integration period t1, and the time slot s1 assigned to itself is executed. The calculation result data is reported and reported, and the idle period I1 is entered. The operation of the sensor 2a is the same as that of the comparative example of FIG.

  On the other hand, the sensor 2b starts detection of radio waves simultaneously with the sensor 2a, and the calculation is executed in the second integration period t2, which is a period until the sensor 2a finishes reporting, in the time slot s2 assigned to itself. The calculation result data is reported and reported, and the idle period I2 is entered. The second integration period t2 is a period obtained by adding the first integration period t1 and the reporting period of the time slot s1.

  The sensor 2c starts detecting the radio wave simultaneously with the sensors 2a and 2b, and executes the calculation during the third integration period t3, which is a period until the sensor 2b finishes reporting, in the time slot s3 assigned to itself. Report the calculation result data.

  In the comparative example of FIG. 8, there are two idle periods I1 and idle periods I2 and I3. In the operation example of FIG. 6, the sensor 2b is connected to the integration period t and the idle period I3 of FIG. Since the calculation is executed as the second integration period t2, a higher quality calculation result can be obtained. Further, since the sensor 2c performs the calculation in the third integration period t3 obtained by adding the continuous period t4 and the idle period I4 in FIG. 8, a higher quality calculation result can be obtained.

Therefore, when the data accumulation device 3 combines the data of the operation results collected from the sensors 2a to 2c, high-quality data can be obtained, and the presence / absence or intensity of the broadcasted radio waves can be determined. A more reliable determination can be made.
Next, a second operation example will be described with reference to FIG.
In the case of this second operation example, as shown in FIG. 7, the sensor 2a immediately executes the calculation during the first integration period t1 after starting the detection of the radio wave, and calculates the result in the time slot s1 assigned to itself. Report with the data. Thereafter, in the first operation example, the integration period t4 during which the operation for obtaining the data to be transmitted in the next frame is executed during the period of the idle period I1 (FIG. 6).

  Further, the sensor 2b starts to detect radio waves simultaneously with the sensor 2a, and the calculation is not only performed in the second integration period t2, but the period of the idle period I2 after the report is set as the integration period t5, and the next Performs operations on data sent in frames.

  The sensor 2c starts detection of radio waves simultaneously with the sensors 2a and 2b, and the calculation is a period until the sensor 2b finishes reporting (a period obtained by adding the integration period t1 and the idle period I4 in FIG. 8). It is executed in the 3 accumulation period t3, and the calculation result data is reported in the time slot s3 allocated to itself.

  In the comparative example of FIG. 8, there are two idle periods I1 and idle periods I2 and I3, whereas in the operation example of FIG. 7, the sensor 2a also has a further frame in the first integration period t1. Therefore, a higher quality calculation result can be obtained. Further, for the sensor 2b, since the integration period t and the idle period I3 in FIG. 8 are set as the second integration period t2, and the idle period I2 is set as the integration period t5 for the next frame, the calculation is executed. The calculation time can be made longer than that in one operation example, and a higher quality calculation result can be obtained. Further, since the sensor 2c performs the calculation in the third integration period t3 obtained by adding the continuous period of the integration period t and the idle period I1 in FIG. 8, a higher quality calculation result can be obtained. In this second operation example, the idle periods I1 to I4 are eliminated in addition to the qualitative improvement of the calculation result data, so that the operation efficiency of the sensors 2a to 2e can be improved.

  According to this embodiment, normally, each sensor 2a-2c calculates (measures and analyzes) the spectrum of the detected radio wave during idle periods I1-I4 (FIG. 8) in which the data accumulator 3 is not wirelessly accessed. (FIGS. 6 and 7), the quality of the data of the calculation result is improved, and the data accumulating device 3 can collect data of necessary quality from each of the sensors 2a to 2e. That is, it is possible to provide a radio wave sensor and a data transmission method that can collect high-quality data for determining the status of radio waves to be detected, such as presence / absence of broadcast waves to be detected.

Here, calculation in the idle periods I1 to I4 will be described.
As in this embodiment, each sensor 2a-2c has a longer calculation time (sensing time), thereby obtaining a higher sensitivity result and maximizing the overall global detection probability Pg. Can do.

を変形し、拡張されたセンシング時間を組み入れると、

を得ることができる。
ここで、Ｐｇはグローバルな検出確率、Ｐｄｉはｉ次の検出確率、Ｐｄはローカルな検出確率、Ｔ’_ｓｅｎは拡張されたセンシング時間を表す。
Ｔ’_ｓｅｎは、

により与えられる。
上記式を変形して、拡張されたセンシング時間Ｔ’_ｓｅｎからセンシング時間Ｔ_ｓｅｎを求め、下記式

を計算することにより、ローカルな検出確率Ｐｄが求められる。但しγは閾値、
Ｑは標準正規分布の末端確率、Ｔ_ｓamはハードウェアを要素とする時間、ζは放送波のＳ／Ｎ比を示す。 For example, the following formula, which is the basic formula for calculation

And incorporating the extended sensing time,

Can be obtained.
Here, Pg represents a global detection probability, Pdi represents an i-th detection probability, Pd represents a local detection probability, and _T′sen represents an extended sensing time.
_T'sen is

Given by.
By modifying the above equation, calculated the sensing time T _sen from the expanded sensing time T _'sen, the following formula

Is calculated, the local detection probability Pd is obtained. Where γ is a threshold value,
Q is the end probability of the standard normal distribution, T _sam is the time with hardware elements, and ζ is the S / N ratio of the broadcast wave.

  Note that the present invention is not limited to the above-described embodiment and its operation example, and can be embodied by modifying the components without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

  DESCRIPTION OF SYMBOLS 1 ... Radio tower, 2a-2e ... Sensor, 3 ... Data integration apparatus, 31 ... Antenna, 32 ... Reception part, 33 ... Integration part, 34 ... Memory, 35 ... Determination part, 21 ... Antenna, 22 ... Reception part, 23 Calculating unit, 24 Measuring unit, 25 Analyzing unit, 26 Transmitting unit, 27 Antenna.

Claims (6)

In a radio wave sensor that performs data transmission using a time slot allocated to itself among a plurality of time slots obtained by dividing a carrier frequency used for transmitting data to a data integration device,
A receiver for receiving radio waves in a predetermined frequency band;
A computing unit that computes a spectrum of radio waves received by the receiving unit during a radio activity suspension period in which the time slot is not assigned;
A radio wave sensor comprising: a transmission unit that reports data obtained as a result of calculation by the calculation unit to an assigned time slot to the data accumulation device. The computing unit is
2. The radio wave sensor according to claim 1, wherein the spectrum is calculated during a period of radio activity suspension until the time of the time slot assigned to the radio wave is reached after the start of radio wave detection. The computing unit is
2. The radio wave sensor according to claim 1, wherein calculation of data to be loaded in the next frame is performed during a period of radio activity suspension after data is reported in the time slot. In a data transmission method in which a radio wave sensor performs data transmission using a time slot assigned to itself among a plurality of time slots obtained by dividing a carrier frequency used for transmitting data to a data integration device.
Receiving the radio wave in a predetermined frequency band by the radio wave sensor;
The radio wave sensor calculates a spectrum of the radio wave during a radio activity idle period in which the time slot is not assigned;
A data transmission method comprising the step of reporting data obtained as a result of calculation by the radio wave sensor to the data accumulating device in an assigned time slot. The radio wave sensor is
5. The data transmission method according to claim 4, wherein after the detection of the radio wave is started, the spectrum is calculated in a radio activity suspension period until a time of a time slot assigned to itself is reached. The radio wave sensor is
5. The data transmission method according to claim 4, wherein calculation of data to be loaded in a next frame is performed during a radio activity suspension period after data is reported in the time slot.

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