JP5594189B2 - Interference determination method, communication apparatus, communication system - Google Patents

Description

  The present invention relates to a technique for determining the presence or absence of radio communication interference between communication devices.

  In recent years, development related to a wireless sensor network in which a network is configured by nodes (communication devices) in which a small electronic circuit having a wireless communication function is added to a sensor has been advanced. In a wireless sensor network, each of a plurality of nodes collects information such as external temperature, humidity, speed, and video, and transmits the information by multi-hop ad hoc communication. Wireless sensor networks are expected to be used for applications such as healthcare, entertainment, and telemedicine.

JP 2010-233142 A

  By the way, in the wireless sensor network, the possibility of inter-node communication interference increases in the frequently used frequency band due to the increase in the number of nodes, but each node cannot directly determine the presence or absence of the interference. There's a problem. In other words, when interference occurs in communication between nodes, each node can only indirectly recognize the occurrence of the interference as a decrease in S / N (Signal to Noise) or a decrease in data transmission rate. . For this reason, the conventional node sometimes adopts a method that is not necessarily appropriate as a countermeasure against interference, such as switching of reception diversity settings or retransmission of packets, where the frequency to be used should be switched. When there is interference at the receiving node, the transmitting node cannot receive an acknowledgment for the transmission data, so it will try to retransmit multiple times, resulting in wasteful power consumption and unnecessary traffic. Will occur.

  Therefore, it is an object of one aspect of the invention to provide an interference determination method, a communication apparatus, and a communication system that can appropriately determine the presence or absence of interference in wireless communication between two communication apparatuses.

In a first aspect, there is provided an interference determination method for determining whether there is interference in a received signal when the second communication device transmits a radio signal from the first communication device to the second communication device.
This interference determination method is
Estimating the distance between the first communication device and the second communication device;
Based on a predetermined relational expression indicating the degree of attenuation with respect to the distance of the radio signal, a reference value of the received power of the signal to be received from the first communication device is calculated based on the estimated distance,
The received power of the received signal is compared with the reference value, and the presence or absence of interference of the received signal of the second communication device is determined based on the comparison result.
Including that.

In a second aspect, a communication device is provided.
This communication device
A receiving unit for receiving a radio signal from another communication device;
A distance estimation unit for estimating a distance between the own device and the other communication device;
A calculating unit that calculates a reference value of received power of a signal to be received from the first communication device based on the distance estimated by the distance estimating unit, based on a predetermined relational expression indicating a degree of attenuation with respect to the distance of the radio signal;
A determination unit that compares the received power of the signal received by the reception unit with the reference value, and determines the presence or absence of interference of the reception signal of the own device based on the comparison result;
Is provided.

In a third aspect, a communication system including a first communication device and a second communication device and capable of wireless communication between the communication devices is provided.
In this communication system,
The first communication device includes a transmission unit that transmits a radio signal addressed to the second communication device.
The second communication device
A receiver for receiving a radio signal from the first communication device;
A distance estimation unit for estimating a distance between the own device and the first communication device;
A calculating unit that calculates a reference value of received power of a signal to be received from the first communication device based on the distance estimated by the distance estimating unit, based on a predetermined relational expression indicating a degree of attenuation with respect to the distance of the radio signal;
A determination unit that compares the received power of the signal received by the reception unit with the reference value, and determines the presence or absence of interference of the reception signal of the own device based on the comparison result.

  According to the disclosed interference determination method, communication apparatus, and communication system, it is possible to appropriately determine the presence or absence of interference in wireless communication between two communication apparatuses.

The figure which shows the structural example of the wireless sensor network containing the node of 1st Embodiment. The block diagram which shows the principal part of the structure of the node of 1st Embodiment. The figure explaining an example of the distance estimation method between transmission / reception nodes in 1st Embodiment. The flowchart explaining an example of the distance estimation method between transmission / reception nodes in 1st Embodiment. The flowchart explaining an example of the distance estimation method between transmission / reception nodes in 1st Embodiment. The flowchart explaining an example of the distance estimation method between transmission / reception nodes using the information of a routing table in 1st Embodiment. The flowchart of the determination process of the presence or absence of interference performed in the node of 1st Embodiment. The flowchart which concerns on the modification of the determination process of the presence or absence of interference performed by the node of 1st Embodiment. The flowchart of the determination process of the presence or absence of interference performed in the node of 2nd Embodiment. 9 is a flowchart showing details of attenuation constant update processing in the second embodiment. The figure which shows an example of CDF of the received power of a node sampled in the different time in the node of 2nd Embodiment. The figure which shows an example which plotted the CDF50% value of each received power in FIG. The figure which shows what produced | generated the least squares approximation curve with respect to the data obtained by repeating the plot of FIG. 12 in multiple times.

  In the following description, when a node transmits a radio signal, the node is referred to as a “transmission node”, and when the node receives a radio signal, the node is referred to as a “reception node”. Either node can be a sending node or a receiving node. A node is an example of a communication device.

(1) First Embodiment (1-1) Wireless Sensor Network FIG. 1 shows a configuration example of a wireless sensor network including nodes of this embodiment. As shown in FIG. 1, each node in the wireless sensor network is connected to various sensors. Information obtained by the sensor of the transmission node is transmitted from the transmission node to the reception node by a radio signal. As a communication protocol between nodes, for example, short-range wireless communication such as ZigBee (registered trademark) using IEEE 802.15.4 as a PHY layer (physical layer) and a MAC (Media Access Controller) layer is known. Then, the communication protocol does not matter.

(1-2) Node Configuration Next, with reference to FIG. 2, the configuration of the node of this embodiment will be described. FIG. 2 is a block diagram showing a main part of the configuration of the node according to the present embodiment.
As shown in FIG. 2, the node of this embodiment includes an antenna 11, a radio reception unit 12, a demodulation / decoding unit 13, a received power measurement unit 14, a distance estimation unit 15, an interference determination unit 16, a packet generation unit 17, a code A modulation / modulation unit 18, a wireless transmission unit 19, and a duplexer (DPX) 20. The duplexer 20 is provided to share the antenna 11 for transmission and reception.
The wireless reception unit is an example of a reception unit. The interference determination unit 16 is an example of a calculation unit and a determination unit. The wireless transmission unit is an example of a transmission unit.

The wireless receiver 12 converts the RF signal received by the antenna 11 into a digital baseband signal. The wireless reception unit 12 includes a band limiting filter, an LNA (Low Noise Amplifier), a local frequency oscillator, an orthogonal demodulator, an AGC (Automatic Gain Control) amplifier, an A / D (Analog to Digital) converter, and the like. The reception power measurement unit 14 measures the reception power of the wireless reception unit 12 and sends information on the measured reception power to the interference determination unit 16.
The demodulation / decoding unit 13 demodulates and decodes the reception signal of the wireless reception unit 12 to obtain a data packet. The data packet can include a header including the address of the transmission source node and the address of the destination node, data including sensor data, and FCS (Frame Check Sequence).

The packet generation unit 17 generates a data packet including sensor data acquired by the own node. The encoder / modulator 18 performs error correction encoding and modulation of the data packet.
The wireless transmission unit 19 includes a D / A (Digital to Analog) converter, a local frequency transmitter, a mixer, a power amplifier, a filter, and the like. The radio transmission unit 19 radiates the baseband signal from the encoding / modulation unit 18 from the antenna 11 to the space after up-converting the baseband frequency to the radio frequency.

The distance estimation unit 15 estimates the distance between the own node and the communication target node. This distance estimation method will be described later.
The interference determination unit 16 determines the presence or absence of interference based on the distance to the communication target node estimated by the distance estimation unit 15. When it is determined that there is interference, the interference determination unit 16 controls the wireless transmission unit 19 to change the transmission frequency in order to avoid interference. An interference determination method will be described later.

  A routing (route search) protocol in the wireless sensor network may be implemented in the node of this embodiment. The type of routing protocol to be implemented is not limited, but, for example, an AODV (Ad hoc On-Demand Distance Vector) defined by RFC (Request For Comments) 3561 of the International Engineering Task Force (IETF) can be applied. AODV is a reactive type (passive type) protocol, and starts a route search only after attempting to transmit and receive data. When the route search is started, the transmission source node broadcasts an RREQ (Route Request) packet for making an inquiry to a neighboring node. The neighboring node also sends an RREQ packet to the neighboring node, and the RREQ packet finally arrives at the destination node. The node that relays the RREQ packet adopts the RREQ packet that has arrived first when it receives the RREQ packet from a plurality of paths. When the RREQ packet arrives, the destination node transmits route information to the source node by transmitting a RREP (Route Reply) packet to the source node by unicasting using the reverse route. As a result, the transmission source node selects a route having the smallest number of hops.

(1-3) Inter-transmission / reception node distance estimation processing Next, the inter-transmission / reception node distance estimation processing mainly performed by the distance estimation unit 15 will be described. Here, the following three methods (a) to (c) are disclosed as methods for estimating the distance between the transmitting and receiving nodes, but any method may be adopted.

(A) Method Using GPS (Global Positioning System) This method will be described with reference to FIG. In this method, the transmission / reception node includes a reception circuit for receiving a GPS signal from a GPS satellite, and the distance between the transmission and reception nodes is estimated based on position positioning data obtained from the GPS signal. In this case, assuming that both the sending and receiving nodes are on the horizontal plane, the coordinates indicated by the positioning data obtained at the receiving node are (x ₁ , y ₁ ), and the coordinates indicated by the positioning data obtained at the sending node are (x ₂ , y ₂ ). At this time, the distance d between transmitting and receiving nodes is calculated by d = ((x ₂ −x ₁ ) ² + (y ₂ −y ₁ ) ² ) ^1/2 .
In this method, the transmitting node transmits a data packet including position measurement data to the receiving node, but the frequency used at this time is different from the frequency normally used in communication between the transmitting and receiving nodes from the viewpoint of avoiding interference. Is preferred.

(B) Method Using Radio Wave Propagation Time This method will be described with reference to FIG. 4 and FIG. FIG. 4 is a flowchart showing the processing of this estimation method. FIG. 5 is a diagram showing a time-series flow of packets transmitted and received between nodes in this estimation method. In this method, packets are transmitted and received between nodes, and the distance between the transmitting and receiving nodes is estimated from the round trip time of the packet according to the distance between the transmitting and receiving nodes. Hereinafter, with reference to FIG. 4 and FIG. 5, the estimation process of the distance between transmission / reception nodes using the radio wave propagation time will be described.
First, the distance measurement node that measures the distance to the other node records the reference time (T ₀ ) at which the distance measurement packet is transmitted to the other node that is the distance measurement target of the own node (step S1). ). Then, the distance measurement node transmits a distance measurement packet to another node (step S2). When the other node receives the distance measurement packet, it returns the distance measurement packet after a predetermined time ΔTp_r has elapsed. The distance measurement node receives the returned distance measurement packet (step S3). The distance measurement node records the time (T ₁ ) at which the distance measurement packet reception process was performed (step S4). Here, the time required from step S1 to step S2 and the time required from step S3 to step S4 (time required for internal signal processing) are denoted by ΔTp_t. At this time, ΔTp_r and ΔTp_t may be considered to be substantially fixed values. Therefore, in this method, the distance measurement node can calculate the distance d with another node according to d = (T ₁ −T ₀ −ΔTp_r−ΔTp_t) / 2 · C (C: speed of light). It should be noted that the frequency used for transmission / reception of the distance measurement packet between the nodes is preferably different from the frequency normally used in communication between the transmission and reception nodes from the viewpoint of avoiding interference, as in (a).

(C) Method using information in routing table For example, the distance between the transmitting and receiving nodes may be estimated under the assumption that the cost between the transmitting and receiving nodes determined by the routing protocol described above is approximately proportional to the distance between the transmitting and receiving nodes. . If data communication has already been performed between two nodes, that is, if routing has been performed before, estimate the distance using the routing table and route discovery table created at that time. Can do.
For example, referring to the example shown in FIG. 6, a case where routing from the node N1 to the node N4 (route of the node N1 → N2 → N3 → N4) has been performed before is shown. Here, for example, when the above-described routing protocol such as AODV is applied, each node has a routing table and a route discovery table in which the residual cost to the target node (in this case, node N4) is described. Is retained. Note that the cost in routing means the number of hops, the value of received power such as a reference signal between nodes, the data rate, and the delay time. In the example shown in FIG. 6, the difference in residual cost between the nodes N2 and N3 is 3, and the difference in residual cost between the nodes N4 and N4 is 6. According to this method, the difference between these residual costs is estimated as the physical distance between the nodes.

(1-4) Interference Presence Determination Processing Next, interference presence determination processing mainly performed by the interference determination unit 16 will be described with reference to FIG. FIG. 7 is a flowchart of the process for determining the presence or absence of interference.
First, the interference determining unit 16 of the receiving node sets the distance d to the transmitting node to a value d0 estimated by the distance estimating unit 15 (d = d0), and at this time, the received power Pr measured by the received power measuring unit 14 at the same time. Is recorded as Pr0 (step S10). The interference determination unit 16 uses this d0 and Pr0 as reference values for equation (1) described later. Note that d0 and Pr0 may be theoretical values in free space or predetermined values obtained by measurement in advance.
Next, the interference determination unit 16 acquires the value dn newly estimated by the distance estimation unit 15 as the distance d to the transmission node, and at the same time, records the reception power Prn measured by the reception power measurement unit 14 ( Step S20). Then, the interference determination unit 16 calculates (estimates) the received power value Pr_t at the distance dn based on the following equation (1), assuming that the propagation environment between the transmitting and receiving nodes conforms to the theoretical value assumed in step S10 (step 1). S30). The attenuation constant γ in step S30 can be a fixed value of γ = 2 as shown in equation (1). Expression (1) is an example of a predetermined relational expression.

  Further, the interference determination unit 16 adds the average value ΔPn of the received power fluctuation due to the estimation error of the received power Pr_t calculated by Expression (1) and fading and the allowable interference value ΔIn to Pr_t to determine the interference. The power Pth, which is a threshold value for, is calculated (step S40). That is, the threshold value power Pth is as shown in the following equation (2).

  Here, when the reception power value Pr_t estimated by Expression (1) is larger than the threshold power Pth (YES in Step S50), the interference determination unit 16 interferes with other nodes other than the reception power from the transmission node. It is determined that power is received (that is, there is interference) (step S60). At this time, the receiving node notifies the transmitting node that the used frequency is to be changed, and controls the wireless transmitting unit 19 of the own node to change the receiving frequency. On the other hand, when the received power value Pr_t estimated by the equation (1) is equal to or less than the threshold power Pth (NO in step S50), it is determined that there is no interference, and the process returns to step S20 to continue monitoring for the presence or absence of interference.

  As described above, according to the node of the present embodiment, the distance between the transmitting and receiving nodes is estimated, and the presence or absence of interference is appropriately determined in order to compare the received power estimated from the distance between the transmitting and receiving nodes with the actual received power. Can be determined. Therefore, the node can take appropriate measures according to the determination of the presence or absence of interference. That is, since the node can determine the presence or absence of interference itself, it is not necessary to take measures that may become inappropriate for interference, such as switching the setting of reception diversity and retransmission of packets. Instead, the node can immediately take effective measures against the interference, such as setting the sleep mode until the interference is reduced, or changing the use frequency. Also, if it is known that the receiving node is receiving interference, the receiving node can broadcast a notification that the receiving node is receiving interference. Traffic can be suppressed. Furthermore, power consumed for packet retransmission and the like in the wireless sensor network is suppressed.

  Note that the accuracy of estimation of the received power Pr_t can be improved by changing the flowchart of the process shown in FIG. 7 to the flowchart shown in FIG. That is, in the flowchart of FIG. 8, steps S22 and S24 are added to the flowchart of FIG. In this added step, d0 which is the reference value of the distance between the transmission nodes and Pr0 which is the reference value of the received power at that time are updated when a sample having a smaller value is obtained. That is, when the estimated distance dn obtained in step S20 is smaller than the previous reference value d0 (YES in step S22), the estimated value dn is set as a new reference value d0, and in step S20. The obtained received power Prn is set as a new received power reference value Pr0 (step S24). The smaller the distance d between the transmitting and receiving nodes, the more accurate the space between the transmitting and receiving nodes can be estimated, so that the actual relationship between the distance and the received power approaches the theoretical relationship. Therefore, in the above update process, the smaller the obtained distance between the transmitting and receiving nodes, the reference value is the distance and the value of the received power at that time, thereby improving the estimation accuracy of the received power Pr_t obtained in step S30. be able to.

(2) Second Embodiment Hereinafter, a node according to a second embodiment will be described.
In the node of the first embodiment, the attenuation constant γ is a fixed value. However, the node of the present embodiment dynamically sets the attenuation constant γ according to the radio propagation environment. Thereby, in the node of this embodiment, the determination precision of the presence or absence of interference improves compared with the node of 1st Embodiment.
Note that the configuration of the node of this embodiment may be the same as that of FIG. 2, but the processing in the interference determination unit 16 is different from the node of the first embodiment. In the present embodiment, the interference determination unit 16 is provided with a lookup table (LUT) for sequentially updating the attenuation constant γ.

  FIG. 9 is an example of a flowchart of processing in the interference determination unit 16 of the node according to the present exemplary embodiment. As shown in FIG. 9, in the present embodiment, an update process (step S26) of the attenuation constant γ can be added to the flowchart shown in FIG. 8 before calculating Pr_t. Needless to say, step S26 may be added to the flowchart of FIG.

FIG. 10 is a flowchart showing details of the attenuation constant γ update process (step S26 in FIG. 9). Hereinafter, details of the updating process of the attenuation constant γ will be described with reference to FIGS.
FIG. 11 is an example of a CDF (Cumulative Distribution Function) of the received power Prn of the node sampled at different times. FIG. 12 is an example in which the CDF 50% value of each received power in FIG. 11 is plotted. FIG. 13 shows a least square approximation curve generated for data obtained by repeating the plot of FIG. 12 a plurality of times. 11 to 13 are all data obtained when the interference determination unit 16 of the node according to the present exemplary embodiment executes the process of FIG.
In each figure and the following description, K is a factor of the Nakagami-Rice distribution or the Nakagami m distribution. For example, “Radio wave propagation basics for digital mobile communications, Corona, especially pages 24 to 27” is known. See literature.

  To estimate the attenuation constant γ, plot the relationship between the received power of the node and the distance between the transmitting and receiving nodes (Prn−dn), and the square error between the obtained plot and the curve due to the theoretical attenuation constant γ is the most. A method of selecting a value of γ that decreases is conceivable. However, in the wireless sensor network, it is assumed that the user holds the transmission node. In that case, the distance between the transmitting and receiving nodes for obtaining the plot cannot be changed on the receiving node side. Therefore, in the present embodiment, the method shown in FIG. 10 is used.

  Referring to FIG. 10, first, the interference determination unit 16 proceeds to step S110 if the update look-up table for the attenuation constant γ has not been created (NO in step S100). Steps S110, S170, and S180 are provided to repeat the processing of steps S120 to S160 a predetermined number of times (N times) so that a plot of the amount necessary to calculate the attenuation constant γ is obtained in step S190. Yes.

Steps S120 and S130 are processes for appropriately setting the sample interval as the sampling condition. If a plurality of received power measurements (that is, sampling) are performed within a time shorter than the coherence time, an error may occur when the CDF is plotted because the propagation path at each time cannot be regarded as independent. As a result, there is a possibility that the sample value of the received power is not included in the appropriate K range to be obtained in the actual propagation environment. Therefore, it is preferable that the received power sampling interval is longer than the coherence time. When the moving body in the propagation environment is only a pedestrian, the coherence time may be considered constant, but when it is not only the pedestrian, it is preferable to measure the coherence time in real time and adaptively change the sample interval. In the measurement of the coherence time, the interference determining unit 16 a first reception signal waveform is converted into a frequency region by Fourier transform, to measure the maximum Doppler frequency f _D (step S120). The interference determination unit 16 calculates a coherence time Tc from the maximum Doppler frequency _{f D} (step S130). Coherence time Tc is approximated by the inverse of the maximum Doppler frequency f _D.

Next, the interference determination unit 16 sets a sample interval longer than the coherence time Tc calculated in step S130, measures the received power Prn at the sample interval, and plots the CDF as illustrated in FIG. S140). Further, the interference determination unit 16 classifies the received power CDF plot value for each K range.
In step S140, for example, at several different times, the received power Prn at the distance dn between the transmitting and receiving nodes is acquired by several hundred to 1000 samples, respectively. The CDF plots obtained with these samples are compared with the theoretical curve for each K of Nakagami-Rice distribution or Nakagami m distribution. Here, as shown in FIG. 11, as a result of the comparison, the CDF of the received power value at each time is in the range of ●: 0 <K <1, ▲: in the range of 3 <K <4, ×: 10 <K The case where it is contained in each range of <20 ranges is assumed.

  Next, the interference determination unit 16 sets the CDF 50% value of each received power to the range of K of received power at each time (0 <K <1, 3 <K <4, 10 <K <20). Is plotted on the graph of Prn-dn. The processing result of this plot is shown in FIG. At this point, only one point is plotted on the Prn-dn graph from each K range. Then, by repeating the processing of steps S120 to S160 several times (N times in FIG. 10), several points can be obtained for each K range as shown in FIG.

Next, as shown in FIG. 13, the interference determination unit 16 calculates a square error between the received power point for each K range and the following equation (3), and the square error is the smallest. The value of γ is calculated (minimum square error approximation). As shown in FIG. 13, a lookup table for updating the attenuation constant γ for each factor K is created when the distance dn between the transmitting and receiving nodes and the received power Prn are known. Note that the processing corresponding to steps S140 to S160 described above has been described with reference to the drawings for ease of explanation, but is actually executed by digital calculation processing by the interference determination unit 16.
When the propagation environment is close to the Rayleigh distribution, the value of the attenuation constant γ calculated as described above becomes a value of about 3 to 4 depending on the degree, and when the propagation environment is close to the Nakagami-Rice distribution (that is, in line-of-sight communication). When a certain degree is strong), it becomes a value of about 2-3 depending on the degree.

When the lookup table as shown in FIG. 13 is created, the interference determination unit 16 of the node according to the present embodiment periodically acquires samples. Then, the range of K to which the CDF obtained by the sample belongs (for example, any of 0 <K <1, 3 <K <4, 10 <K <20 described above) is specified, and based on the specified K range The attenuation constant γ is uniquely obtained by referring to the lookup table.
As described above, the attenuation constant γ is sequentially updated based on the periodic samples. Based on the updated attenuation constant γ, the node interference determination unit 16 calculates the following expression (3) in step S26 of FIG. 9 to calculate received power Pr_t.

  In the above-described example, the range of the factor K is three, but this is only an example, and an arbitrary K range of 3 or more can be set. However, if the step size in the K range is too small, the number of samples acquired in each K range may be insufficient, and the accuracy of estimating the attenuation constant γ may be reduced. Therefore, it is preferable to take a sufficient number of samples according to the number of each range of K.

  Although the embodiments of the present invention have been described in detail above, the interference determination method, communication apparatus, and communication system of the present invention are not limited to the above-described embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. Of course, you may do.

  Regarding the above embodiments, the following additional notes are disclosed.

(Appendix 1)
An interference determination method for determining whether or not there is interference in a received signal when transmitting a radio signal from a first communication device to a second communication device,
Estimating the distance between the first communication device and the second communication device;
Based on a predetermined relational expression indicating the degree of attenuation with respect to the distance of the radio signal, a reference value of the received power of the signal to be received from the first communication device is calculated based on the estimated distance,
The received power of the received signal is compared with the reference value, and the presence or absence of interference of the received signal of the second communication device is determined based on the comparison result.
An interference determination method.

(Appendix 2)
The relational expression indicates that the reference distance, the estimated first communication device, and the second communication when the received power in the second communication device separated by a predetermined reference distance from the first communication device is defined as the reference received power. A value obtained by multiplying the value of the ratio of the device to the γ power (γ: positive value) by the reference received power is calculated as the reference value;
Updating the value of γ in response to a change in propagation environment between the first communication device and the second communication device;
The interference determination method according to attachment 1.

(Appendix 3)
When the communication between the first communication device and the second communication device is line-of-sight communication, the value of γ is set to a small value as compared to the case where line-of-sight communication is not performed.
The interference determination method described in Appendix 2.

(Appendix 4)
When the received power of the signal received from the first communication device is smaller than the reference received power, the received power of the received signal is changed to a new reference received power, and the signal is received from the first communication device. Further including setting the distance between the first communication device and the second communication device estimated to be a new reference distance,
The interference determination method described in Appendix 2 or 3.

(Appendix 5)
A receiving unit for receiving a radio signal from another communication device;
A distance estimation unit for estimating a distance between the own device and the other communication device;
A calculating unit that calculates a reference value of received power of a signal to be received from the first communication device based on the distance estimated by the distance estimating unit, based on a predetermined relational expression indicating a degree of attenuation with respect to the distance of the radio signal;
A determination unit that compares the received power of the signal received by the reception unit with the reference value, and determines the presence or absence of interference of the reception signal of the own device based on the comparison result;
A communication device comprising:

(Appendix 6)
The relational expression indicates that the reference distance, the estimated first communication device, and the second communication when the received power in the second communication device separated by a predetermined reference distance from the first communication device is defined as the reference received power. A value obtained by multiplying the value of the ratio of the device to the γ power (γ: positive value) by the reference received power is calculated as the reference value;
The calculation unit includes:
Updating the value of γ in response to a change in the propagation environment of the other communication device and the own device,
The communication apparatus described in appendix 5.

(Appendix 7)
When the communication between the other communication device and the own device is line-of-sight communication, the value of γ is set to a small value compared to the case where line-of-sight communication is not performed.
The communication apparatus described in appendix 6.

(Appendix 8)
The calculation unit includes:
When the received power of the signal received from the other communication device is smaller than the reference received power, the received power of the received signal is changed to a new reference received power and the signal is received from the other communication device. Further including, as a new reference distance, a distance between the other communication apparatus and the self apparatus estimated when
The communication apparatus according to appendix 6 or 7.

(Appendix 9)
In a communication system comprising a first communication device and a second communication device and capable of wireless communication between the communication devices,
The first communication device is
A transmission unit for transmitting a radio signal to the second communication device;
The second communication device
A receiver for receiving a radio signal from the first communication device;
A distance estimation unit for estimating a distance between the own device and the first communication device;
A calculating unit that calculates a reference value of received power of a signal to be received from the first communication device based on the distance estimated by the distance estimating unit, based on a predetermined relational expression indicating a degree of attenuation with respect to the distance of the radio signal;
A determination unit that compares the received power of the signal received by the reception unit with the reference value and determines the presence or absence of interference of the reception signal of the own device based on the comparison result;
Communications system.

DESCRIPTION OF SYMBOLS 11 ... Antenna 12 ... Radio | wireless receiving part 13 ... Demodulation / decoding part 14 ... Received power measurement part 15 ... Distance estimation part 16 ... Interference determination part 17 ... Packet generation part 18 ... Encoding / modulation part 19 ... Radio transmission part 20 ... Duplexer

Claims (4)

An interference determination method for determining whether or not there is interference in a received signal when transmitting a radio signal from a first communication device to a second communication device,
Estimating the distance between the first communication device and the second communication device;
When the received power in the second communication device separated by a predetermined reference distance from the first communication device is defined as the reference received power, the reference distance and the estimated distance between the first communication device and the second communication device Based on the relational expression for calculating a value obtained by multiplying the value of the ratio to the γ power (γ: positive value) by the reference received power as the reference value, the ratio is received from the first communication device by the estimated distance. Calculate the reference value of the received power of the power signal,
Comparing the received power of the received signal with the reference value, and determining the presence or absence of interference of the received signal of the second communication device based on the comparison result ;
An interference determination method further comprising updating the value of γ according to a change in propagation environment between the first communication device and the second communication device . When the received power of the signal received from the first communication device is smaller than the reference received power, the received power of the received signal is changed to a new reference received power, and the signal is received from the first communication device. Further including setting the distance between the first communication device and the second communication device estimated to be a new reference distance,
The interference determination method according to claim 1 . A receiving unit for receiving a radio signal from another communication device;
A distance estimation unit for estimating a distance between the own device and the other communication device;
When the received power in the second communication device separated by a predetermined reference distance from the first communication device is defined as the reference received power, the reference distance and the estimated distance between the first communication device and the second communication device Based on the relational expression for calculating a value obtained by multiplying the value of the ratio to the γ power (γ: positive value) by the reference received power as the reference value, the first distance is estimated by the distance estimation unit. A calculation unit for calculating a reference value of received power of a signal to be received from the communication device;
A determination unit that compares the received power of the signal received by the reception unit with the reference value, and determines the presence or absence of interference of the reception signal of the own device based on the comparison result;
Means for updating the value of γ in response to a change in propagation environment between the first communication device and the second communication device;
A communication device comprising: In a communication system comprising a first communication device and a second communication device and capable of wireless communication between the communication devices,
The first communication device is
A transmission unit for transmitting a radio signal to the second communication device;
The second communication device
A receiver for receiving a radio signal from the first communication device;
A distance estimation unit for estimating a distance between the own device and the first communication device;
When the received power in the second communication device separated by a predetermined reference distance from the first communication device is defined as the reference received power, the reference distance and the estimated distance between the first communication device and the second communication device Based on the relational expression that calculates, as the reference value, a value obtained by multiplying the value of the ratio to the γ power (γ: positive value) by the reference received power, the first communication is performed based on the distance estimated by the distance estimation unit. A calculation unit for calculating a reference value of received power of a signal to be received from the device;
A determination unit that compares the received power of the signal received by the reception unit with the reference value, and determines the presence or absence of interference of the reception signal of the own device based on the comparison result;
Means for updating the value of γ in response to a change in propagation environment between the first communication device and the second communication device ,
Communications system.

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