JP2009038754A - Wireless communication apparatus and interference detection method - Google Patents

Abstract

Radio waves of a wireless device other than a wireless communication device in a wireless LAN are detected, and it is determined whether interference due to the radio waves is a cause of a packet transmission error.
When a radio communication device detects radio waves in the same frequency band used by itself and other radio devices (S203: "YES"), the radio waves do not include preamble information of the wireless LAN ( In S204: “NO”), it is determined that the radio wave is a radio wave of a wireless device other than the wireless communication device. Further, the radio wave is equal to or greater than a predetermined threshold (S205: “YES”), and packet transmission is performed. If an error has occurred (S208: “YES”), it is determined that the cause of the packet transmission error is due to interference of the radio wave (S210).
[Selection] Figure 2

Description

  The present invention relates to a wireless communication device and an interference detection method used in a wireless local area network (wireless LAN).

  In recent years, cases of introducing a wireless LAN in homes and offices are increasing. As a typical technique of wireless LAN, IEEE 802.11 standardized by IEEE (Institute of Electrical and Electronics Engineers) is known.

  However, the 2.4 GHz ISM (Industry Science Medical) band used in IEEE802.11b and IEEE802.11g is also used in microwave ovens, amateur radio, Bluetooth, etc., and these wireless devices and wireless LANs There is a problem that interference occurs between the two.

In the technique described in Patent Document 1, a wireless LAN is distinguished from a microwave oven, an amateur wireless device, or the like by determining a radio wave pattern. For example, the pattern of radio waves output from a microwave oven is a continuous pulse signal with a period of about 7 to 22 ms. By identifying this pattern, radio waves in the microwave oven can be detected as interference radio waves in a wireless LAN. it can.
JP 2004-179888 A

  However, such a conventional interference detection method has the following problems. That is, in the interference detection method described in Patent Document 1, since interference is detected using a radio wave pattern, if there is periodic traffic in the wireless LAN, the periodic traffic is distinguished from the microwave oven radio waves. It is not possible to obtain an erroneous interference detection result. For example, in VoIP (Voice Over Internet Protocol), transmission and reception are performed with periodic traffic such as 20 ms. Therefore, when there is periodic wireless LAN traffic such as VoIP, there is a possibility that radio waves in the microwave oven cannot be detected correctly.

  In addition, even when a microwave transmission is detected when a packet transmission error occurs, for example, when communication quality deteriorates, it is not possible to determine whether the cause of the packet transmission error is due to interference of the microwave. could not. Communication quality degradation occurs even when the communication devices are separated from each other. Therefore, if a microwave oven is detected when a wireless communication device in a wireless LAN is separated from an access point and is in a weak electric field state and communication quality is deteriorated, there is a possibility that the communication quality is deteriorated due to the microwave oven.

  The present invention has been made in view of this point, and detects the radio wave of a wireless device other than the radio communication device in the wireless LAN, and further detects the cause of the packet transmission error of the radio communication device in the wireless LAN. An object of the present invention is to provide a wireless communication apparatus and an interference detection method that can determine whether or not the interference is caused by interference.

  In order to solve the above problems, a wireless communication device of the present invention is a wireless communication device that performs wireless communication in a wireless local area network, and is different from the wireless communication in the same frequency band as the wireless communication at the time of packet transmission. Detecting means for detecting radio waves of a wireless device using a method, and when an error occurs in the packet transmission, the radio wave does not include preamble information of the wireless local area network, and the energy level is set in advance If it is more than the above, it will comprise the determination means which determines with the cause of the said error being the interference of the said electromagnetic wave.

  The interference detection method of the present invention is an interference detection method used for wireless communication in a wireless local area network, and uses the same frequency band as the wireless communication and a method different from the wireless communication when transmitting a packet. A step of detecting radio waves of a wireless device, and when an error occurs in packet transmission, if the radio wave does not include preamble information of the wireless local area network and the energy level is equal to or higher than a preset threshold, the error Determining that the cause is due to the interference of the radio waves.

  According to the present invention, a wireless communication device in a wireless LAN detects radio waves in the same frequency band used by the own device and other wireless devices, and determines whether or not the detected radio waves include preamble information of the wireless LAN. Thus, it can be determined whether or not the detected radio wave is that of another wireless device. Further, by determining whether or not the detected radio wave energy is equal to or greater than a predetermined threshold, it is possible to determine whether or not the cause of the packet transmission error is due to radio wave interference of another wireless device. .

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

  FIG. 1 is a block diagram showing a main configuration of a wireless communication apparatus 100 in a wireless LAN according to an embodiment of the present invention.

  In FIG. 1, the wireless communication device 100 includes an antenna 101, a wireless LAN transmission / reception circuit 102, and a control circuit 106. The wireless LAN transmission / reception circuit 102 includes a baseband circuit 103, an RF (Radio Frequency) circuit 104, and an interference detection circuit 105. The baseband circuit 103 and the RF circuit 104 transmit and receive the transmission / reception data of the wireless communication apparatus 100 via the antenna 101 using the control information input from the control circuit 106. The interference detection circuit 105 detects radio waves (interference radio waves) of a radio device other than the radio communication device 100 in the wireless LAN, for example, a microwave oven, via the antenna 101. Further, the interference detection circuit 105 determines whether or not the cause of the packet transmission error in the wireless communication apparatus 100 is due to the detected radio wave interference based on the control of the control circuit 106.

  FIG. 2 is a flowchart showing a procedure for detecting the interference radio wave in the interference detection circuit 105 and determining the cause of the packet transmission error.

  First, in step S201, the wireless communication device 100 starts packet transmission.

  Next, in step S202, the wireless LAN transmission / reception circuit 102 performs carrier wave detection by a CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method.

  Next, in step S203, the interference detection circuit 105 determines whether or not radio waves in the same frequency band used by the wireless communication device 100 and other wireless devices have been detected during carrier wave detection.

  If the determination result in step S203 is “NO”, the procedure proceeds to step S212.

  On the other hand, if the determination result in step S203 is “YES”, in step S204, the interference detection circuit 105 determines whether or not radio LAN preamble information is included in radio waves in the same frequency band. When a radio LAN preamble is included in radio waves in the same frequency band, the current communication is in a busy state based on the CSMA / CA mode defined by IEEE 802.11 and the energy level of the radio waves in the same frequency band. Or packet transmission is determined.

  If the determination result in step S204 is “YES”, the procedure proceeds to step S207.

  On the other hand, when the determination result in step S204 is “NO”, the procedure proceeds to step S205.

  In step S205, the interference detection circuit 105 determines whether the energy level of radio waves in the same frequency band is equal to or higher than a predetermined threshold, that is, the interference threshold.

  If the determination result in step S205 is “NO”, the procedure proceeds to step S207.

  If the determination result in step S205 is “YES”, the procedure proceeds to step S206.

  In step S206, the interference detection circuit 105 determines that the radio wave in the same frequency band is an interference radio wave, and sets the interference wave detection flag (Flag) to “1” to indicate that this packet transmission is performed in an interference state. Set to.

  Next, regardless of whether or not an interference radio wave is detected, in step S207, the wireless communication device 100 performs packet transmission.

  Next, in step S208, the interference detection circuit 105 determines whether a packet transmission error has occurred.

  If the determination result of step S208 is “NO”, the procedure proceeds to step S212.

  On the other hand, when the determination result of step S208 is “YES”, the procedure proceeds to step S209.

  In step S209, the interference detection circuit 105 determines whether or not the interference wave detection flag is “1”.

  If the determination result in step S209 is “YES”, the interference detection circuit 105 determines that the packet transmission error is due to an interference radio wave, and in step S210, the control circuit 106 increases the error count due to interference. . Here, the error count due to interference may be an error count due to a single interference, or may be an error count based on an interference error rate calculated using a certain number of packets. In IEEE802.11, if the data transmission is unicast, the total number of transmissions can be read from the management information.

  On the other hand, when the determination result in step S209 is “NO”, that is, when the interference wave detection flag is “0”, the interference detection circuit 105 determines that the cause of the packet transmission error is not due to the interference radio wave. In step S211, the control circuit 106 increases the normal error count. In IEEE 802.11, packet transmission errors are managed by a counter.

  Next, after the count is increased or when packet transmission is successful, the interference detection circuit 105 sets the interference wave detection flag to “0” in step S212.

  The interference threshold value in step S205 of the interference detection procedure shown in FIG. 2 may be automatically adjusted based on the received energy level using the received packet.

  FIG. 3 is a flowchart for explaining a method of automatically adjusting an interference threshold used for interference detection. FIG. 3 shows a procedure for automatically adjusting the interference threshold using a Beacon received packet.

  The wireless communication apparatus 100 always receives a beacon as in step S301 while belonging to an access point.

  If Beacon is received, then in step S302, wireless communication apparatus 100 calculates a value S [dBm] of Beacon's RSSI (Received Signal Strength Indicator).

  Next, in step S303, the wireless communication device 100 subtracts a certain value α from the RSSI value S [dBm].

  Next, in step S304, the wireless communication device 100 sets the subtraction result in step S303 to the interference threshold value N [dBm].

  Since the beacon is normally transmitted every 100 ms, the wireless communication apparatus 100 can automatically adjust the interference threshold every time the beacon is received, that is, at an interval of 100 ms.

  Note that α used in step S303 is a predetermined value and corresponds to an SN ratio (Signal to Noise Ratio). In the case of IEEE 802.11, the S / N ratio that can be communicated is determined based on the transmission rate to be used, and therefore α is determined based on the transmission rate to be used. Α may also be automatically varied based on the received transmission rate. In that case, if the transmission rate is high, the communicable SN ratio increases, so the value of α is also increased. Conversely, if the transmission rate is low, communication is possible even if the SN ratio is small, so α is also small. To do.

  Although the case of Beacon reception by the wireless communication apparatus 100 has been described here, communication reception data may be used in the case of packet reception.

  Further, the interference threshold value in step S205 of FIG. 2 may be automatically adjusted based on the received energy level using the received packet.

  As described above, according to the present embodiment, a wireless communication device in a wireless LAN detects radio waves in the same frequency band used by the device and other wireless devices, and the detected radio waves are preamble information of the wireless LAN. Therefore, it is possible to correctly detect radio waves from wireless devices other than the wireless communication device.

  Further, according to the present embodiment, the wireless communication device in the wireless LAN compares the detected radio wave energy of the other radio device with the predetermined threshold value, thereby causing the packet transmission error to be caused by the radio wave of the other radio device. It can be determined whether or not this is due to interference.

  The above description is an illustration of a preferred embodiment of the present invention, and the scope of the present invention is not limited to this. For example, any interference source may be used, and any interference source that does not belong to a wireless LAN system can be applied to an interference device.

  Further, the type, number, connection method, and the like of each circuit unit constituting the wireless communication device are not limited to the above-described embodiments.

  The radio communication apparatus and the interference detection method according to the present invention can be applied to the use of a radio communication apparatus used in a radio local area network.

1 is a block diagram showing a main configuration of a wireless communication device in a wireless LAN according to an embodiment of the present invention. The flowchart which shows the procedure which detects the interference electromagnetic wave in the interference detection circuit which concerns on one embodiment of this invention, and determines the cause of a packet transmission error The flowchart for demonstrating the method of adjusting automatically the interference threshold value used for the interference detection which concerns on one embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Wireless communication apparatus 101 Antenna 102 Wireless LAN transmission / reception circuit 103 Baseband circuit 104 RF circuit 105 Interference detection circuit 106 Control circuit

Claims (5)

A wireless communication device that performs wireless communication in a wireless local area network,
Detecting means for detecting radio waves of a wireless device using the same frequency band as the wireless communication and a method different from the wireless communication at the time of packet transmission;
When an error occurs in the packet transmission, if the radio wave does not include the preamble information of the wireless local area network and the energy level of the radio wave is equal to or higher than a preset threshold, the cause of the error Determining means for determining that is due to the interference of the radio wave,
A wireless communication apparatus comprising: The detection means includes
Detecting the radio wave by CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) method,
The wireless communication apparatus according to claim 1. The determination means includes
A predetermined value is subtracted from the RSSI (Received Signal Strength Indicator) value of Beacon received by the wireless communication device, and a subtraction result is set as the threshold value.
The wireless communication apparatus according to claim 2. The determination means includes
Each time the wireless communication device receives the Beacon, the subtraction result is set as the threshold value.
The wireless communication apparatus according to claim 3. An interference detection method used for wireless communication in a wireless local area network,
Detecting a radio wave of a wireless device using the same frequency band as the wireless communication and a method different from the wireless communication at the time of packet transmission;
When an error occurs in packet transmission, if the radio wave does not include preamble information of the wireless local area network and the energy level of the radio wave is equal to or higher than a preset threshold, the cause of the error is Determining that it is due to interference of the radio waves;
An interference detection method.

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