JP6293696B2 - Radio environment estimation method, radio environment estimation apparatus, and radio environment estimation program - Google Patents

Description

  The present invention relates to a radio environment estimation method, a radio environment estimation device, and a radio environment that estimate interference radio wave information indicating the frequency of occurrence and time occupancy of an interference radio wave for each interference source that emits the interference radio wave in a radio environment in which the interference radio wave exists. It relates to an estimation program.

  In recent years, wireless communication services have been diversified, and the number of transmitting stations using various wireless communication methods has increased. If the number of transmitting stations that use radio waves in the same frequency band increases within a certain area, the probability that interference will occur when a certain transmitting station performs radio communication may increase the frequency utilization efficiency. This may be more noticeable when the interference avoidance function is not functioning normally due to a so-called hidden terminal or when the transmitting stations using radio waves in the same frequency band are operated with different protocols. It is done. The probability of interference also increases when there are non-communication equipment that emits radio waves in the same frequency band as these transmitting stations, such as ISM equipment operated in the Industry-Science-Medical (ISM) band. The frequency utilization efficiency may be degraded.

  If all the radio waves emitted by nearby transmitting stations and electronic devices (hereinafter referred to as interference sources) that use radio waves in the same frequency band are interference radio waves, in a wireless environment where such interference radio waves exist, Therefore, the effect of improving the frequency utilization efficiency can be expected by performing control in consideration of interference radio waves. However, in order to perform this control efficiently, a radio environment estimation technique for accurately estimating the interference radio wave information indicating the frequency of occurrence and time occupancy of the interference radio wave for each interference source is required.

  In the conventional wireless environment estimation technology described in Patent Document 1, each transmitting station that is an interference source is stopped for a certain period, and the radio waves received during the stop period are observed as interference radio waves, so that interference radio wave information is transmitted for each transmitting station. Is disclosed.

  In addition, when the access control method of the transmitting station is code division multiple access (CDMA), since the transmitting station performs spreading processing using a spreading code in advance, the interference radio wave separated from the received radio wave by despreading processing is used. By observing, a method of estimating interference radio wave information without providing a stop period of the transmitting station can be considered.

  Further, in Non-Patent Document 1, using a wireless LAN analyzer having a demodulation function for all signals included in received radio waves, packet information such as a transmission station and a destination MAC address and a sequence number is obtained from the demodulated signal. By interpolating signals that could not be demodulated based on the acquired packet information, a method of estimating interference radio wave information for each transmitting station that radiates interference radio waves without providing a stop period is presented.

FIG. 4 shows an example of a radio environment estimation procedure in the conventional method described in Non-Patent Document 1.
In FIG. 4, first, packet information obtained by demodulating radio waves received within an observation period is recorded in time series (step S01). Next, for each set of transmitting station and destination described in the acquired packet information, the individual time occupation rate is calculated from the occupied time of the received packet, and the sequence number and retransmission flag are set for each set of transmitting station and destination. After confirmation, a packet error rate, which is a ratio of packets that can be received by the receiving station and packets that cannot be received, is calculated (step S02). Next, the occupied time of the packet that could not be received is calculated using the calculated packet error rate, and the individual occupied time is supplemented (step S03).

JP 2013-115503 A

Tadayuki Fukuhara, "Measurement Method of Wireless Occupancy in Wireless LAN", IEICE Technical Report SR2009-46 (2009)

  In the conventional wireless environment estimation technology described in Patent Document 1, it is necessary to temporarily stop the signal of the transmitting station, observe the interference radio wave, and estimate the interference radio wave information for each transmission station. Communication quality of the wireless communication system may deteriorate.

  In the method of separating interference radio waves by despreading in the code division multiple access method, all transmitting stations require pre-coding processing, and interference coming from electronic equipment that does not perform pre-processing such as coding. For radio waves, the interference radio wave information cannot be acquired.

  The conventional wireless environment estimation technique described in Non-Patent Document 1 is based on the premise that packet information such as sequence numbers can be acquired for all signals that are not temporally superimposed. Therefore, the influence of interference radio waves that cannot acquire packet information is not considered.Therefore, if there is interference radio waves that are not supported by the receiving station and that are not used for wireless standards or communication purposes, and packet information cannot be acquired, interference for each interference source Unable to get radio wave information.

  The present invention provides an interference radio wave indicating the frequency of occurrence and time occupancy of each interference source without stopping the transmission signal of the transmission station or performing pre-processing at the transmission station in a wireless environment where the interference radio wave exists. It is an object of the present invention to provide a radio environment estimation method, a radio environment estimation apparatus, and a radio environment estimation program capable of estimating information.

According to a first aspect of the present invention, there is provided a wireless environment estimation method for estimating interference radio wave information indicating an occurrence frequency and a time occupancy rate of an interference radio wave for each interference source that emits the interference radio wave, measuring received power of the received interference radio wave, The frame time obtained by demodulating the interfering radio wave is acquired as successful demodulation frame information, and the time of the interfering radio wave that could not be demodulated even with the received power exceeding the predetermined threshold is acquired as non-demodulated radio wave information. A first step of recording as sequence information, a second step of calculating interference radio wave statistical information obtained by performing statistical processing on the interference radio wave time series information over a predetermined statistical period, and a part or all of interference radio waves the incoming defined based on probability arrival process, based on the state transition model representing the operation of one interference source access control scheme of the interference source, interference waves statistics By solving the equation of the distribution and the interference radio wave information, and a third step of calculating an interference wave information indicating the frequency and time occupancy of the interference wave for each interference source.

According to a second aspect of the present invention, there is provided a wireless environment estimation apparatus that estimates interference radio wave information indicating an occurrence frequency and a time occupancy rate of an interference radio wave for each interference source that emits the interference radio wave. Measure the received power of the interfering radio wave, obtain the frame time obtained by demodulating the interfering radio wave as successful demodulation frame information, and further demodulate the time of the interfering radio wave that could not be demodulated even with the received power exceeding the predetermined threshold Interfering radio wave processing unit that acquires radio wave information and records them as interference radio wave time series information, and interference radio wave statistics that calculates interference radio wave statistical information obtained by performing statistical processing on interference radio wave time series information over a predetermined statistical period tables and processing unit, the arrival of some or all of the interfering radio wave defined based on the probability arrival process, the operation of one interference source access control scheme of the interference source Based on the state transition model, an interference radio wave information calculation unit that calculates interference radio wave information indicating the frequency of occurrence and time occupancy of the interference radio wave for each interference source by solving the relational expression between the interference radio wave statistical information and the interference radio wave information With.

  A radio environment estimation program according to a third aspect of the invention calculates the interference radio wave information indicating the frequency of occurrence of interference radio waves and the time occupancy rate for each interference source by causing a computer to execute each step of the radio environment estimation method according to the first aspect of the invention. .

  According to the present invention, in an environment in which there is an interference radio wave emitted from a nearby interference source, no matter what the interference radio wave arrives without stopping the signal of the transmission station or performing preprocessing in the transmission station, the interference source Interfering radio wave information indicating the frequency of occurrence and time occupancy of each interfering radio wave can be estimated.

It is a figure which shows the Example structure of the radio | wireless environment estimation apparatus of this invention. It is a flowchart which shows the example of a process sequence of the radio | wireless environment estimation apparatus of this invention. It is a figure showing the state transition model of the transmitting station which operate | moves with the access control system of wireless LAN. It is a flowchart which shows the process sequence which estimates the time occupation rate of a nonpatent literature 1.

FIG. 1 shows a configuration of an embodiment of a wireless environment estimation apparatus of the present invention.
The radio environment estimation apparatus of the present invention is a radio frequency environment other than a radio communication application such as a frequency sharing environment using a plurality of radio communication systems, a radio environment where a plurality of transmitting stations using radio waves in the same frequency band exist at a high density, and ISM devices. It is installed in an environment where electronic devices that emit light are present, and interference radio wave information indicating the frequency of occurrence and time occupancy of interference radio waves is estimated with high accuracy for each interference source.

  In FIG. 1, the wireless environment estimation apparatus according to the present exemplary embodiment includes an interference radio wave reception unit 11, an interference radio wave processing unit 12, an interference radio wave statistical processing unit 13, and an interference radio wave information calculation unit 14. All of these functional units may be provided in a transmission station apparatus having a wireless communication function, or a part thereof may be provided in a central control station apparatus that controls the transmission station.

The interference radio wave receiving unit 11 receives the interference radio wave and outputs it to the interference radio wave processing unit 12.
The interference radio wave processing unit 12 measures the received power of the received interference radio wave, acquires demodulation successful frame information related to the interference radio wave successfully demodulated, and non-demodulable radio wave information related to the interference radio wave that could not be demodulated in time series. The time series information is output to the interference radio wave statistical processing unit 13.

  The interference radio wave statistical processing unit 13 outputs the interference radio wave statistical information statistically processed for each statistical period to the interference radio wave information calculation unit 14 based on time-series received power information, demodulated frame information, and non-demodulable radio wave information.

  The interference radio wave information calculation unit 14 uses the interference radio wave statistical information to detect the arrival of interference radio waves from an interference source that does not operate in this access control method based on a state transition model representing the operation of a specific access control method. The simultaneous equations defined and configured in the arrival process are solved, and the interference radio wave information indicating the frequency of occurrence and the time occupation rate of the interference radio wave is calculated for each interference source.

FIG. 2 shows an example of a processing procedure in the wireless environment estimation apparatus of the present invention.
In FIG. 2, when the interference radio wave reception unit 11 receives the interference radio wave, the interference radio wave processing unit 12 measures the received power of the received interference radio wave and performs a demodulation process. Here, when the demodulation of the interference radio wave is successful, successful demodulation frame information indicating the transmission station and the frame time is acquired. On the other hand, when demodulation of the interference radio wave fails and the received power is equal to or greater than a predetermined threshold, radio wave information that cannot be demodulated indicating the time during which the radio wave that cannot be demodulated is acquired. The interference radio wave time series information including the received power information, the demodulation success frame information, and the radio wave information that cannot be demodulated is recorded for the interference radio wave thus received (step S11).

  At this time, a waiting time and a response time that are indispensable for communication may be supplemented as the time of a successful demodulation frame. In addition, when there is an idle time less than a certain time between two radio waves that cannot be demodulated, the idle time may be supplemented as a time when radio waves that cannot be demodulated exist.

The interference radio wave statistical processing unit 13 demodulates each transmission station in the statistical processing period T _m using the interference radio wave time series information (received power information, demodulation successful frame information, non-demodulated radio wave information) obtained in step S11. The individual demodulation success time T _suc totaling the successful frame times, the individual demodulation success number N _suc counting the number of successful demodulations for each transmission station, the average frame time (average demodulation success time) Tc for each transmission station, The non-demodulable radio wave reception time T _int that is the sum of the reception times of radio waves that cannot be demodulated, the non-demodulable radio wave reception count N _int that counts the number of times the radio wave is continuously received, and the received power is less than a predetermined threshold. A free time T _f obtained by summing the times is derived (step S12).

At this time, when waiting time and response time that are indispensable for communication as described above are supplemented as the time of a successful demodulation frame, the idle time between the two non-demodulable radio waves is less than a certain time, When complemented as existing time, the complemented time is excluded from the free time _Tf .

  The interference radio wave information calculation unit 14 uses the interference radio wave statistical information obtained in step S12, and the average state duration time Es that is an average value of the duration time of each state of the state transition model representing the operation of the specific access control method. Is calculated using the following equation (1) (step S13).

Here, (N _suc ) _j is an individual number of j-th transmitting stations (jεK, K = 1, 2, 3,..., M) among M transmitting stations (MεN, N: natural number). This represents the number of successful demodulations, and T _s represents the duration of the idle state specific to the access control method.

  Next, using the interference radio wave statistical information obtained in step S12 and the average state duration Es obtained in step S13, interference radio wave information is calculated by the method exemplified below (step S14).

  Here, as an example of step S14, assuming that there are M wireless LAN devices compliant with the IEEE802.11g standard in a certain area, a transmitting station or a wireless station that performs wireless communication with a different access control method in the area. A case will be described in which the frequency of occurrence of interference radio waves for each interference source and the time occupancy rate of interference radio waves are calculated as interference radio wave information in a wireless environment where there is one electronic device that emits radio waves for purposes other than communication applications.

FIG. 3 shows a state transition model of a transmitting station i (iεK, K = 1, 2, 3,..., M) operated in the wireless LAN access control method compliant with the IEEE802.11g standard. Is as follows. In the case of indicating the state transition parameter of the transmitting station i, a description will be given by adding a subscript i to each symbol.
p: Probability that another transmitting station transmits a signal (state transition parameter)
q: Probability of a new frame to be transmitted during one state (state transition parameter)
r: Probability of holding the next frame to be transmitted when the frame transmission is successful and when the number of retransmissions reaches the maximum value and the frame is discarded (state transition parameter)
R: Maximum value of the number of retransmissions W _s : Maximum value of the contention window when the number of retransmissions is s

Here, using the radio wave transmission probability τ _j of the transmitting station j in each state, the state transition parameter p _i of a certain transmitting station i can be expressed as in equation (2).

When there are interfering radio waves generated by M transmitting stations operated in the access control system of the wireless LAN, based on the state transition model of FIG. 3, a predetermined statistical time T _m and an individual demodulation success time of the transmitting station i (T _{suc) i} and an average frame time Tc _i of the transmission station i, a radio wave transmission probability tau _j, and free time T _f, the duration of idle T _s of the transmitting station j in each state (j∈K) And the relational expression of the average state duration Es is expressed as Expressions (3) and (4).

Here, in addition to the M transmitting stations operated in the access control scheme of the wireless LAN, when there is an interference radio wave generated by the interference source l (l is not included in K), the interference source l in the state x Using the radio wave transmission probability τ _lx , the relational expressions of equations (3) and (4) can be rewritten as equations (5) and (6).

Here, the arrival of interfering radio waves emitted from the interference source l is defined by the Poisson arrival process. That is, assuming that the duration of a certain state x is T _x , the relational expression between the radio wave transmission probability τ _lx of the interference source l in the state x and the variable λ _l related to the frequency of occurrence of the interference radio wave per unit time is expressed by the following equation (7) It is expressed as

From equations (5), (6), and (7), when the arrival of interfering radio waves generated by the interference source l is defined by the Poisson arrival process, the predetermined demodulation time T _m and the individual demodulation success time ( T _suc) and _i, the average frame period Tc _i of the transmission station i, and idle time T _f, the duration T _s of the free state, the average state duration Es, radio transmission probability τ of the transmission station j in each state The relational expression between _j and the variable λ _l concerning the frequency of occurrence of the interference radio wave per unit time is expressed as Expressions (8) and (9).

At this time, the occurrence frequency N _i and the time occupation rate T _i of the interference radio wave emitted from the transmission station i are obtained using the radio wave transmission probability τ _i of the transmission station i, the predetermined statistical time T _m, and the average state duration Es. Are expressed as equations (10) and (11).

The frequency N _{l of} interference radio waves generated by the interference source l and the time occupation rate T _l are the radio wave reception time T _int that cannot be demodulated, the number N _{int of} radio waves that cannot be demodulated, the average state duration Es, by using the radio wave transmission probability tau _j of the transmitting station j, the variable lambda _l about the occurrence frequency per unit of the interference radio wave time is expressed by the equation (12) to (15).

Equations (8) and (9) can be applied to τ _j and λ _l using numerical analysis methods such as sequential substitution, scissors, Newton's method, multi-objective optimization methods such as genetic algorithms, or combinations thereof. Can be solved.

Further, using the values of τ _j and λ _l obtained, the interference radio wave information indicating the frequency of occurrence and time occupancy of the interference radio wave emitted from the transmission station i and the interference source l is calculated from the equations (10) to (15). can do.

Specific numerical examples are shown below.
A transmitter station 1-5 that operates in accordance with a wireless LAN access control method compatible with the IEEE802.11g standard and generates interference radio waves in the vicinity of a transmitter station compatible with the IEEE802.11g standard equipped with a wireless environment estimation device; It is assumed that there is an interference source 6 that emits interference radio waves that cannot be demodulated by a transmission station equipped with the apparatus. Here, when all the interference radio waves are received by the transmission station equipped with the radio environment estimation device, the interference radio wave processing unit 12 of the radio environment estimation device performs the interference radio wave time obtained based on the received power of the interference radio waves and the demodulation result. The series information is output to the interference radio wave statistical processing unit 13. An example of interference radio wave time series information is shown in Table 1.

Next, the interference radio wave statistical processing unit 13 performs statistical processing on the interference radio wave time series information in Table 1, and outputs the interference radio wave statistical information in Table 2 to the interference radio wave information estimation unit 14, for example.

Table 2 shows that when the predetermined statistical time T _m is 1 second, the individual demodulation success times (T _suc ) ₁ to (T _suc ) ₅ of the transmitting stations ₁ to ₅ are 0.11 seconds, 0.10 seconds, 0.10 seconds, 0.10 seconds, 0.07 seconds, radio wave reception time T _int that cannot be demodulated is 0.43 seconds, idle time T _f is 0.09 seconds, and the individual demodulation success counts (N _suc ) ₁ to (N _suc ) _{5 of} the transmitting stations ₁ to ₅ are respectively 74 times, 100 times, 100 times, 100 times, 100 times, non-demodulable radio wave reception number N _int is 414 times, and average frame times Tc _{1 to} Tc 5 of transmitting stations 1 to ₅ are 1.5 × 10 ⁻³ seconds, respectively. , 1.0 × 10 ⁻³ seconds, 1.0 × 10 ⁻³ seconds, 1.0 × 10 ⁻³ seconds, and 0.7 × 10 ⁻³ seconds. The radio waves that cannot be demodulated are not limited to those from an interference source that emits an interfering radio wave that cannot be demodulated, but also include when the interference radio waves from the transmitting stations 1 to 5 collide.

Using the interference radio wave statistics information in Table 2 and the idle time duration T _s , the average state duration Es is obtained as 9.4 × 10 ⁻⁵ seconds from Equation (1). Here, T _s is 9.0 × 10 ⁻⁶ seconds which is a slot time defined in the IEEE802.11g standard.

Next, the radio wave transmission probability τ _j of the transmitting station j is obtained from the equations (8) and (9) using the interference radio wave statistics information of Table 2, the idle time duration T _s, and the average state duration time Es. (j = 1,2,3,4,5) and by solving for the variable λ ₆ related to the frequency of occurrence of the interference radio wave of the interference source 6 per unit time, τ ₁ = 1.16 × 10 ⁻² , τ ₂ = 1.33 × 10 ⁻² , τ ₃ = 1.33 × 10 ⁻² , τ ₄ = 1.33 × 10 ⁻² , τ ₅ = 1.22 × 10 ^−2, and λ ₆ = 3.04 × 10 ⁻⁴ .

Finally, using the interference wave statistical information in Table 2, the average state duration Es, and the values of τ _j and λ ₆ , the frequency and time of occurrence of interference waves for each interference source from Equations (10) to (15) The interference radio wave information that is the occupation rate is estimated. Interference radio wave generation frequencies N _{1 to} N ₅ and time occupancy rates T _{1 to} T _{5 at the} estimated transmitting stations 1 to ₅ , interference radio wave generation frequency N ₆ and time from the interference source 6 that emits the interference radio waves at random The occupation rate T ₆ is shown in Table 3.

  The communication environment estimation apparatus of the present invention can be realized by a wireless reception unit, a computer, and a computer program that performs the above processing. This computer program can be stored in a computer-readable storage medium or provided via a network.

11 Interference radio wave reception unit 12 Interference radio wave processing unit 13 Interference radio wave statistical processing unit 14 Interference radio wave information calculation unit

Claims (7)

In the radio environment estimation method for estimating interference radio wave information indicating the frequency of occurrence of interference radio waves and the time occupation rate for each interference source that emits interference radio waves,
Measure the received power of the received interfering radio wave, acquire the frame time obtained by demodulating the interfering radio wave as successful demodulation frame information, and demodulate the time of the interfering radio wave that could not be demodulated even with the received power exceeding the predetermined threshold A first step of acquiring as radio wave information and recording these as interference radio wave time series information;
A second step of calculating interference radio wave statistical information obtained by performing statistical processing on the interference radio wave time series information over a predetermined statistical period;
Part or the arrival of all of the interfering radio waves is defined based on the probability arrival process, based on the state transition model representing the operation of one interference source access control scheme of the interference source, and the interference wave statistics A third step of calculating interference radio wave information indicating an occurrence frequency and a time occupancy rate of the interference radio wave for each of the interference sources by solving a relational expression with the interference radio wave information. Method. The radio environment estimation method according to claim 1,
In the second step, as the interference radio wave statistical information calculated from the interference radio wave time series information, the individual demodulation success is obtained by summing up the frame times successfully demodulated for each interference source in a predetermined statistical processing period T _m. Time T _suc , individual demodulation success number N _suc that counts the number of successful demodulations for each interference source, average frame time Tc for each interference source, and reception time of non-demodulated radio wave reception time T performed and _int, and a demodulation Call wave reception number N _int obtained by counting the number of times of receiving the demodulated allowed radio waves continuously, the process of receiving power derives the idle time T _f which is the sum of time which was less than the predetermined threshold value,
The third step uses the idle time duration T _S unique to the access control method in the state transition model and the interference radio wave statistics information T _m , T _f , N _suc , N _int , An average state duration Es, which is an average value of the duration of each state of the state transition model, is calculated, and an arrival of an interference radio wave from an interference source that does not operate in the access control method among the interference radio waves is stochastic arrival process And based on the interference radio wave statistics information, T _m , T _f , T c, N _suc , T _int , N _int , T _S , Es and the relational expression among the interference radio wave information are solved. A wireless environment estimation method comprising: performing processing for calculating interference radio wave information indicating an occurrence frequency and a time occupation rate of interference radio waves for each interference source. In the radio | wireless environment estimation method of Claim 1 or Claim 2,
A wireless environment estimation method, wherein a Poisson arrival process is used as a probability arrival process that defines the arrival of the interference radio wave. For each interference source that emits interference radio waves, in a radio environment estimation device that estimates interference radio wave information indicating the frequency of occurrence and time occupancy of interference radio waves,
An interference radio wave receiving unit for receiving the interference radio wave;
Measure the received power of the received interfering radio wave, acquire the frame time obtained by demodulating the interfering radio wave as successful demodulation frame information, and demodulate the time of the interfering radio wave that could not be demodulated even with the received power exceeding the predetermined threshold An interference radio wave processing unit that obtains non-radio wave information and records them as interference radio wave time-series information;
An interference radio wave statistical processing unit that calculates interference radio wave statistical information obtained by performing statistical processing on the interference radio wave time series information over a predetermined statistical period;
Part or the arrival of all of the interfering radio waves is defined based on the probability arrival process, based on the state transition model representing the operation of one interference source access control scheme of the interference source, and the interference wave statistics An interference radio wave information calculating unit that calculates interference radio wave information indicating an occurrence frequency and a time occupancy rate of the interference radio wave for each of the interference sources by solving a relational expression with the interference radio wave information. Environment estimation device. In the radio | wireless environment estimation apparatus of Claim 4,
The interference radio wave statistical processing unit, as the interference radio wave statistical information calculated from the interference radio wave time-series information, individual demodulation that totals the frame time successfully demodulated for each interference source within a predetermined statistical processing period T _m Successful time T _suc , individual demodulation success frequency N _suc counting the number of successful demodulations for each interference source, average frame time Tc for each interference source, and reception time of non-demodulable radio wave reception time A process of deriving a free time T _f obtained by summing T _int , a non-demodulable radio wave reception count N _int that counts the number of times radio waves that can be continuously demodulated, and a time when the received power is less than a predetermined threshold is performed. Configuration,
The interference radio wave information calculation unit uses an idle state duration T _S unique to the access control method in the state transition model and T _m , T _f , N _suc , and N _int that are the interference radio wave statistical information. , Calculating an average state duration Es that is an average value of the duration of each state of the state transition model, and probabilistic arrival of an interference radio wave from an interference source that does not operate in the access control method among the interference radio waves Solving the relational expression between T _m , T _f , T c, N _suc , T _int , N _int , T _S , Es and the interference radio wave information defined based on the process Thus, the wireless environment estimation device is configured to perform processing for calculating interference radio wave information indicating an occurrence frequency and a time occupation rate of interference radio waves for each interference source. In the radio | wireless environment estimation apparatus of Claim 4 or Claim 5,
A radio environment estimation apparatus characterized in that a Poisson arrival process is used as a probability arrival process that defines the arrival of the interference radio wave.   A radio environment estimation program that causes a computer to execute the steps of the radio environment estimation method according to claim 1 to calculate interference radio wave information indicating an occurrence frequency and a time occupation rate of an interference radio wave for each interference source. .

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