WO2011030466A1 - 無線局 - Google Patents
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- WO2011030466A1 WO2011030466A1 PCT/JP2009/066037 JP2009066037W WO2011030466A1 WO 2011030466 A1 WO2011030466 A1 WO 2011030466A1 JP 2009066037 W JP2009066037 W JP 2009066037W WO 2011030466 A1 WO2011030466 A1 WO 2011030466A1
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- statistical information
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- failure
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/10—Monitoring; Testing of transmitters
- H04B17/15—Performance testing
- H04B17/17—Detection of non-compliance or faulty performance, e.g. response deviations
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04B—TRANSMISSION
- H04B17/00—Monitoring; Testing
- H04B17/20—Monitoring; Testing of receivers
- H04B17/26—Monitoring; Testing of receivers using historical data, averaging values or statistics
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/20—Arrangements for detecting or preventing errors in the information received using signal quality detector
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04L—TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION
- H04L1/00—Arrangements for detecting or preventing errors in the information received
- H04L1/24—Testing correct operation
- H04L1/245—Testing correct operation by using the properties of transmission codes
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W72/00—Local resource management
- H04W72/50—Allocation or scheduling criteria for wireless resources
- H04W72/54—Allocation or scheduling criteria for wireless resources based on quality criteria
- H04W72/542—Allocation or scheduling criteria for wireless resources based on quality criteria using measured or perceived quality
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W28/00—Network traffic management; Network resource management
- H04W28/02—Traffic management, e.g. flow control or congestion control
- H04W28/04—Error control
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04W—WIRELESS COMMUNICATION NETWORKS
- H04W84/00—Network topologies
- H04W84/02—Hierarchically pre-organised networks, e.g. paging networks, cellular networks, WLAN [Wireless Local Area Network] or WLL [Wireless Local Loop]
- H04W84/10—Small scale networks; Flat hierarchical networks
- H04W84/12—WLAN [Wireless Local Area Networks]
Definitions
- the present invention relates to a wireless station such as a wireless terminal and a wireless base station, for example.
- the communication performance is significantly degraded due to radio interference. Therefore, in order to stably maintain high reliability of the wireless system, it is necessary to promptly detect and take measures when a failure occurs.
- Non-Patent Document 1 a method of detecting radio wave interference based on a demodulation error rate of a transmission frame is used.
- This is a method using a phenomenon in which a transmission frame affected by radio wave interference fails in demodulation processing in a wireless station and a demodulation error such as PLCP error or CRC error increases.
- a demodulation error such as PLCP error or CRC error increases.
- Radio interference interference may be caused by inter-frame interference due to synchronization failure between radio stations, interference with interfering radio waves such as microwave ovens using the same frequency band or Bluetooth [TM], multipath due to reflected waves such as walls There are various types such as fading. In order to contain radio interference interference, it is necessary to take appropriate measures according to these causes, which requires, in addition to conventional interference detection techniques, techniques for accurately identifying the type of interference cause.
- the demodulation error used by the prior art is not necessarily a phenomenon that occurs only to radio wave interference.
- demodulation errors also occur when radio waves are received at low reception levels due to long distance or shielding. Therefore, the prior art may present an erroneous detection result of radio wave interference failure as the demodulation error is increased due to other causes, although no interference actually occurs.
- the present invention provides a radio station that makes it possible to accurately identify the cause of a radio communication failure.
- a wireless station is a wireless station connected to another wireless station via a wireless link to identify a cause of a failure of the wireless link, the wireless link of the wireless link according to a wireless link control scheme Based on a wireless link control unit that executes control, a statistical information acquisition unit that acquires statistical information representing the state of the wireless link during execution of the wireless link control, and statistical information acquired by the statistical information acquisition unit, And a failure cause identification unit that identifies a failure cause of the wireless link from among a plurality of failure causes that are associated with statistical information in advance.
- the present invention makes it possible to accurately identify the cause of a wireless communication failure.
- 1 shows an exemplary configuration of a communication system according to a first embodiment of the present invention.
- the structural example of the radio station which concerns on 1st Embodiment is shown.
- the flow of an example of the processing procedure of a statistical information acquisition part is shown.
- the flow of an example of the procedure of the 1st processing of failure cause specific part is shown.
- 7 shows a flow of processing for transitioning to the PS mode.
- Indicates the frame format of Null frame. 7 shows frame formats of an RTS frame and a CTS frame.
- An example of a procedure of a 2nd process of a failure cause identification part is shown.
- Indicates a congested state. Indicates a state in which interference due to radio noise is generated. It shows a state in which adjacent channel interference occurs.
- FIG. 20 shows the flow of operations of the wireless station of FIG.
- the other structural example of the radio station of 2nd Embodiment is shown.
- FIG. 23 shows the flow of operations of the wireless station of FIG. 21.
- FIG. 1 shows an example of the configuration of a communication system according to the first embodiment of the present invention.
- 1 represents a network
- A represents a wireless base station (wireless station) connected to the network
- 2 represents a wireless link
- B represents a wireless terminal (wireless station) connected to the wireless link 2.
- a wireless terminal B connected to the wireless base station A is shown in FIG. 1, a plurality of wireless terminals may be connected.
- a wireless LAN Local Area Network
- CSMA / CA Carrier Sense Multiple Access with Collision Avoidance
- FIG. 2 shows a configuration example of the radio station M according to the present embodiment.
- the wireless station M may be the wireless base station A. That is, each element 11, 12, 13, 14, 15 in FIG. 2 may be implemented in the wireless terminal B or in the wireless base station A.
- the statistical information acquisition unit 11 acquires statistical information indicating the state of the wireless link 2 formed between the wireless terminal B and the wireless base station A.
- the statistical information storage unit (statistical information DB) 12 stores statistical information acquired by the statistical information acquisition unit 11 together with time information.
- the time information is obtained from a timer (not shown) provided in the device.
- the radio link control unit 13 executes radio link control of the radio link 2 in accordance with a radio link control scheme specified in advance.
- the loss rate measurement unit (measurement unit) 14 transmits a test frame to another wireless station (here, the wireless base station A), and a frame representing the percentage of the transmitted frames that were not correctly received by the wireless station M. Measure the loss rate. Note that, instead of the frame loss rate, a frame arrival rate may be calculated that indicates the proportion of frames correctly received by the wireless station.
- the failure cause identification unit 15 Based on the statistical information acquired during wireless link control by the wireless link control unit 13, the failure cause identification unit 15 identifies the failure cause of the wireless link from among a plurality of failure causes associated with statistical information in advance. . The association between the statistical information and the plurality of failure factors is prepared for each radio link control scheme. Further, the failure cause identification unit 15 holds the correspondence between the frame loss rate and the plurality of failure causes, and identifies the failure cause of the wireless link using the frame loss rate measured by the loss rate measurement unit 14.
- Each of the elements 11, 12, 13, 14, 15 may be configured as hardware or may be realized as a software module (program) executed on the wireless base station M.
- the software module may be stored in a computer readable recording medium and read and executed by a computer such as a CPU.
- FIG. 3 shows a flow of an example of the processing procedure of the statistical information acquisition unit 11.
- the statistical information acquisition unit 11 acquires the statistical information by executing predetermined statistical information acquisition processing (step S11). Below, an example of predetermined statistical information is shown.
- the number of PLCP preamble synchronization failures in (1) is a value indicating the number of times that preamble synchronization has failed in the frame reception process of the IEEE 802.11 PLCP layer.
- the number of PLCP preamble parity errors in (2) is a value indicating the number of times a parity error has occurred in the frame reception process of the IEEE 802.11 PLCP layer.
- the PLCP incorrect rate number in (3) is a value indicating the number of times the rate of the received frame is incorrect in the frame reception process of the IEEE 802.11 PLCP layer. Incorrect means, for example, that the value stored in the frame rate field is a value different from the specified value.
- the number of PLCP unauthorized services in (4) is a value indicating the number of unauthorized received frame services in the frame reception process of the IEEE 802.11 PLCP layer. Incorrect means, for example, that the value stored in the service field is a value different from the specified value.
- the number of CRC errors in (5) is a value that indicates the number of times that the FCS error check indicates that it is incorrect in the frame reception process of the IEEE 802.11 MAC layer.
- the noise level of (6) is a value indicating the amount of noise in the received signal in IEEE 802.11.
- the noise level is measured, for example, for each channel.
- the EVM of (7) is an index that represents the waveform quality of the digital modulation signal. Specifically, EVM indicates an error in the amplitude and phase of an actual digital modulation signal with respect to the amplitude and phase uniquely determined in accordance with the modulation scheme.
- the values of the statistical information (1) to (7) increase, for example, when an interference wave is received or when demodulation of a frame received at a low reception level fails.
- the statistical information to be acquired may be one or more of the statistical information (1) to (7). Also, without being limited to these statistical information, other types of statistical information may be acquired.
- the statistical information acquisition unit 11 stores the acquired statistical information in the statistical information storage unit 12 together with time information (step S12).
- the process may wait for a fixed time (step S13) and return to step S11.
- the periodic interval for example, is generally performed at 5-minute intervals in a statistical acquisition tool on the Internet. It is also possible to maintain the cycle interval constant and improve the accuracy by determining the standby time in step S13 in synchronization with the cycle timer.
- a method may be adopted in which an individual periodic interval is set and acquired for each of the statistical information.
- an average value, a maximum value, a minimum value, a standard deviation, and the like may be measured on the wireless terminal B, and these may be acquired as statistical information.
- the statistical information acquisition process (S11 to S13) of the statistical information acquisition unit 11 may be started and ended, for example, in accordance with an instruction from the failure cause identification unit 14, and the acquisition process is constantly performed during activation of the device. It is also good.
- the failure cause identification unit 15 specifies the failure cause of the wireless link using the statistical information acquisition unit 11, the statistical information DB 12, and the wireless link control unit 13 (first process). Alternatively, the failure cause identification unit 15 identifies the failure cause of the wireless link using the statistical information acquisition unit 11, the statistical information DB 12, the wireless link control unit 13, and the loss rate measurement unit 134 (second processing).
- FIG. 4 shows a flow of an example of the procedure of the first process of the failure cause identification unit 15.
- the failure cause identification unit 15 detects a process start input (step S21).
- the start input is, for example, a periodic input from a cycle timer or the like, or a specific instruction from a manager.
- a start input may be input to the failure cause identification unit 15.
- the start instruction may be input when the value of the statistical information exceeds a predetermined threshold or when the frame loss rate exceeds a predetermined value.
- the failure cause identification unit 15 acquires statistical information using the statistical information acquisition unit 11 (step S22), and stores the acquired statistical information in the statistical information DB 12 (step S23).
- the average value, the maximum value, the minimum value, the standard deviation, and the like may be stored and handled as statistical information. If the value of the statistical information acquired in steps S22 and S23 is less than or equal to the threshold value, it may be determined that no failure has occurred in the wireless link, and the processing in step S24 and subsequent steps may not be performed. That is, step S24 and subsequent steps may be performed only when the value of the statistical information is larger than the threshold value. Alternatively, steps S22 and S23 themselves may be omitted, and the process may proceed to step S24 after step S21.
- the failure cause identifying unit 15 instructs the radio link control unit 13 to execute radio link control, and the radio link control unit 13 executes radio link control according to a radio link control scheme given in advance (step S24).
- a radio link control scheme given in advance An example (scheme 1 to scheme 3) of a representative radio link control scheme is shown.
- the radio link control scheme is not limited to the following, and there are other types as described later. Details of each method will be described later.
- the failure cause identifying unit 15 acquires statistical information using the statistical information acquiring unit 11 in a state where the wireless link control in step S24 is performed (step S25), and stores the acquired statistical information in the statistical information DB 12 (Step S26).
- steps S24 to S26 are repeatedly implemented (see dotted lines with arrows in the figure). At this time, the radio link control performed immediately before is invalidated. At the time of repetition, steps S22 to S26 may be repeated.
- Method 1 performs control to stop communication between the wireless terminal B and the wireless base station A when the present example (the wireless station M is the wireless terminal B and the other wireless station is the wireless base station A) It is. Specifically, the data transmission of the wireless terminal B is stopped, and the wireless base station A stops the data transmission addressed to the wireless terminal B. As a method of stopping data transmission addressed to the wireless terminal B to the wireless base station A, define a unique frame for instructing transmission stop, and stop the wireless terminal B by transmitting the frame to the wireless base station A. It is also good. Alternatively, the wireless base station A may stop data transmission to the wireless terminal B by transitioning the wireless terminal B to a PS (Power Save) mode defined by the IEEE 802.11 standard.
- PS Power Save
- FIG. 5 shows the flow of processing in which the wireless terminal B transitions to the PS mode using a Null frame.
- the wireless terminal B transmits a Null frame to the wireless base station A (H11).
- the frame format of the Null frame defined by the IEEE 802.11 standard is shown in FIG.
- the power management field (Power Management field in FIG. 6) of the Null frame is set to 1.
- the wireless base station A having received the Null frame recognizes that the wireless terminal B has transitioned to the PS mode, sends back an ACK to the wireless terminal B (H12), and thereafter stops data transmission to the wireless terminal B ( H13).
- the wireless terminal B having received the ACK stops data transmission (H14). Thereby, the wireless communication between the wireless base station A and the wireless terminal B can be stopped (H15).
- the wireless terminal B transmits a Null frame in which the power management field is set to 0 to the wireless base station A (H16).
- the wireless base station A having received the Null frame recognizes that the wireless terminal B has released the PS mode, sends back an ACK to the wireless terminal B (H17), and then resumes data transmission to the wireless terminal B (H17). H18).
- the wireless terminal B that has received the ACK can resume data transmission (H19), and cancel the wireless communication stop between the wireless base station A and the wireless terminal B.
- the wireless terminal B receives an interference wave when control to stop communication between the wireless base station A and the wireless terminal B is performed, it is a radio wave transmitted by a third party device. It is characterized by For example, in the case of a fault such as shadowing or multipath fading to be described later, the radio wave itself emitted by the wireless terminal B is the cause, and if the fault cause is shadowing or multipath fading etc., scheme 1 By performing the wireless link control of the above, the value of the statistical information (for example, the noise level of the used channel) becomes smaller. Also, in the case of congestion, radio noise, and interference with adjacent channel interference, which will be described later, the radio terminal B receiving the radio wave transmitted by the third party device causes the failure.
- the radio wave transmitted by the third party device causes the failure.
- the value of statistical information (for example, the noise level of the used channel) remains large. Therefore, it becomes possible to distinguish the cause of failure by comparing the value of the statistical information acquired in the step S25 after implementing the wireless link control of method 1 using these characteristics with a threshold value.
- Method 2 performs control to stop communication of another wireless terminal communicating on the same channel as communication between the wireless base station A and the wireless terminal B.
- a method of stopping communication of other wireless terminals for example, there is a method of using an RTS frame or a CTS frame defined by the IEEE 802.11 standard.
- the frame formats of RTS and CTS frames are shown in FIG.
- the RTS frame and CTS frame have a duration field (Duration field in FIG. 7) for setting a scheduled period to be used for wireless communication, and another wireless terminal that has received the RTS frame or CTS frame has the period set in the duration field, Disable transmission (NAV: Network Allocation Vector).
- NAV Network Allocation Vector
- the same channel as communication between the wireless base station A and the wireless terminal B can be transmitted by transmitting an RTS frame or a CTS frame in which the wireless terminal B sets a desired time period to prohibit the communication of another wireless terminal in the duration field.
- the communication of other wireless terminals communicating with can be stopped.
- the failure cause is IEEE 802.11 by determining whether or not the value of statistical information (for example, the noise level of the used channel) remains large after implementing radio link control of scheme 2 using this feature. It becomes possible to distinguish whether the signal is generated by a radio wave transmitted by a device conforming to the standard or a device not conforming to the IEEE 802.11 standard. For example, when the value (S22) of statistical information before performing this radio link control is larger than the threshold and the value (S25) of statistical information after performing becomes less than or equal to the threshold, the failure cause is congestion. It becomes possible to estimate.
- Method 3 performs control to stop the communication of another wireless terminal communicating using an adjacent channel of the channel used for communication between the wireless base station A and the wireless terminal B. is there.
- the communication of the other wireless terminal is stopped using the RTS frame or the CTS frame as in the system 2, but in this system, the RTS frame or the CTS frame is transmitted using the adjacent channel.
- the communication of the wireless terminal communicating using the adjacent channel is stopped.
- the value of statistical information (for example, noise level of used channel) before performing radio link control of scheme 3 is larger than the threshold and the value of statistical information after implementation (for example, noise level of used channel) If the failure occurs, it is possible to estimate that the failure cause is a radio wave (adjacent channel interference) transmitted by a wireless terminal communicating on the adjacent channel.
- Method 4 of transmitting a test frame to wireless base station A after stopping communication of another wireless terminal using the same channel as communication between wireless base station A and wireless terminal B other than the above It is also possible to transmit scheme 5 in which the test frame is transmitted at a lower rate than scheme 4 after stopping the communication between the base station A and the wireless terminal B and the communication of the other wireless terminal using the same channel. See Figure 16).
- the test frame may be transmitted using the test frame transmission function of the loss rate measurement unit 14 described later.
- the measurement accuracy may be enhanced by performing transmission and reception of the test packet multiple times.
- test packet transmission rate By lowering the test packet transmission rate to a low rate as in method 5, it is possible to perform measurement in a state in which the resistance to space loss of the radio wave propagation path is enhanced, thereby causing multipath fading and shadowing as described later. And separation is possible.
- the IEEE 802.11b standard defines four types of available transmission rates: 1, 2, 5.5, and 11 Mbps, and Method 5 uses a lower rate than Method 4 among these methods to improve immunity. Tests can be conducted.
- method 1 + 2 (scheduling communication between the wireless terminal B and the wireless base station A and stopping communication of other wireless terminals communicating on the same channel), method 1 simultaneously executing method 1 and method 2, method 1 It is also possible to execute scheme 1 + 3 simultaneously executing scheme 3 and scheme 3 (stop communication between wireless terminal B and wireless base station A and stop communication of another wireless terminal communicating using an adjacent channel). (See FIG. 16 described later).
- the failure cause identification unit 15 associates the failure cause with the statistical information for each radio link control method based on the statistical information obtained during the radio link control.
- the failure cause is identified using the information (first correspondence information) (step S27).
- the correspondence information associates, for example, the value range of statistical information with the failure cause for each radio link control method.
- a range of values of statistical information for example, a range where the value of statistical information is equal to or greater than a threshold and a range less than the threshold may be used.
- the threshold may be different for each cause of failure.
- the failure cause identification unit 15 identifies the failure cause included in the range of the value of the statistical information acquired corresponding to the implemented radio link control method. When a plurality of wireless link control methods are performed, it is possible to narrow down the causes of failures in stages. A specific example of step S27 will be described later.
- FIG. 8 illustrates an example of the procedure of the second process of the failure cause identification unit 15.
- the loss rate measurement unit 14 it is possible to specify the cause of failure more finely than the first process described above.
- Steps S31 to S36 are the same as steps S21 to S26 in FIG. 4, and therefore redundant description will be omitted.
- step S37 the loss rate measurement unit 14 measures a frame loss rate in communication between the wireless base station A and the wireless terminal B.
- the frame loss rate is measured by transmitting a test packet from the wireless terminal B to the wireless base station A and receiving a response frame.
- the test packet for example, a Null frame defined by IEEE 802.11 can be used (see FIG. 6).
- an RTS frame is used to reserve a scheduled period for measurement, and measurement is performed after avoiding a frame collision with the hidden terminal. It is also good. If the cause of frame loss is a frame collision with a hidden terminal, performing a test using RTS frames reduces the frame loss rate. Therefore, a test using RTS frames can be used to determine whether a hidden terminal has caused a frame collision.
- the failure cause identification unit 15 completes the processing in steps S31 to S36, the range of the failure cause and the value of the statistical information for each radio link control method based on the acquired statistical information and the measured frame loss rate. And the correspondence information (the first correspondence information), and the correspondence information (the second correspondence information) in which the range of values of the frame loss rate and the failure cause are corresponded, and the failure cause is identified ( Step S38). For example, as described in step S27 in FIG. 4, one or more failure causes are identified from the first correspondence information, and among the identified causes, the value of the frame loss rate measured based on the second correspondence information. We will narrow down the failure factors that are included as the final failure factors. A specific example of step S38 will be described later.
- the wireless base station is referred to as AP, and the wireless terminal as STA.
- Congestion is defined as a state where the number of STAs belonging to a certain channel increases and collision avoidance by CSMA / CA frequently occurs in all APs and STAs belonging to the channel. In a congested state, there is a high probability that synchronization processing of frames transmitted between STAs will fail, and frame collisions occur due to simultaneous transmission.
- FIG. 9 shows a state where STA1, STA2, and STA3 are connected to the AP and a congestion state occurs.
- STA1 and STA2 simultaneously transmit, interference due to frame collision occurs, and STA3 that received the interference frame fails in frame demodulation and the value of the aforementioned statistical information increases.
- frame demodulation of STA3 is also possible when simultaneous transmission occurs between AP and STA1 or between AP and STA2. It fails and the value of statistics increases.
- Radio wave noise is defined as a state in which radio waves of the same frequency band different from the standard of IEEE 802.11 such as a microwave oven or Bluetooth (TM) reach the STA.
- FIG. 10 shows a state in which interference due to radio wave noise (microwave oven) is generated.
- the STA that has received the radio noise starts frame reception processing but fails in demodulation and the value of statistical information increases. Also, when the frame transmitted by the AP to the STA interferes with radio noise, frame demodulation fails and the value of the statistical information increases.
- “Adjacent channel interference” is defined as a state in which radio waves of a channel adjacent to the channel used by the STA reach the STA.
- the 2400 MHz to 2497 MHz band is divided into 14 channels. However, since the bands of adjacent channels overlap one another, interference will occur if used simultaneously.
- FIG. 11 shows a state in which adjacent channel interference occurs.
- the STA2 communicates using an adjacent channel of a channel used by the STA1 and the AP. At this time, STA1 that has received a frame on the adjacent channel transmitted by STA2 fails in frame demodulation, and the value of statistical information increases. Also, when the frame transmitted by the AP to the STA1 interferes with the frame transmitted by the STA2, frame demodulation fails and the value of the statistical information increases.
- “Shadowing” is defined as a state in which a direct wave is blocked by a shield between the STA and the AP, and communication is performed using a reflected wave or a diffracted wave.
- FIG. 12 shows a state in which shadowing is occurring. When shadowing occurs, the signal power of the frame received by the STA weakens, frame demodulation fails, and the value of statistical information increases. Also, when the distance between the AP and the STA is far and the signal strength is greatly reduced due to the propagation loss, frame demodulation fails and the value of statistical information increases.
- Multipath fading is defined as a state in which a reflected wave from a wall or the like is delayed and delivered to the STA in addition to the direct wave transmitted by the AP.
- FIG. 13 shows a state in which interference due to multipath fading is generated.
- multipath fading occurs, inter-symbol interference occurs between the direct wave transmitted by the AP and the reflected wave that arrives delayed, so that the STA fails in frame demodulation and the value of statistical information increases.
- the “hidden terminal” is defined as a state in which a shield or the like exists between certain STAs and carrier sense does not function with each other.
- FIG. 14 shows a state where STA1 and STA2 become hidden terminals with each other.
- STA1 and STA2 become hidden terminals with each other, a situation occurs where STA2 starts transmitting data to the AP even though STA1 is transmitting data to the AP, and as a result, Frames collide and interfere.
- no frame demodulation failure occurs in STA1 and STA2, but since the AP fails to receive the frame transmitted by STA1 and does not send back an ACK, the frame loss rate of the STA increases.
- the “radio wave noise in the vicinity of the connection destination radio station” is defined as a state in which radio waves of the same frequency band different from the standard of IEEE 802.11 such as a microwave oven or Bluetooth [TM] reach the connection destination radio station of the radio station M.
- FIG. 15 shows a state in which interference due to radio wave noise (microwave oven) is generated in the vicinity of the connection destination radio station. If radio wave noise occurs in the vicinity of a connection destination radio station (AP) to which the wireless station M (STA) is connected, a frame transmitted by the STA to the AP interferes with the radio wave noise. Although radio frame noise in the vicinity of the AP does not cause a frame demodulation failure in the STA, the AP fails in receiving a frame transmitted by the STA and does not send back an ACK, so the frame loss rate of the STA increases.
- AP connection destination radio station
- STA wireless station M
- correspondence information (first correspondence information) indicating the relationship between the radio link control method, failure cause and statistical information, correspondence information indicating the relation between frame loss rate measurement method, failure factor and frame loss rate (second correspondence information) Will be explained.
- FIG. 16 illustrates an example of correspondence information (first correspondence information) indicating the relationship between the radio link control method, the failure cause, and the statistical information.
- “Exist” and “absent” in the figure indicate the magnitude relationship between the value of the statistical information and the threshold. “Yes” indicates that the value of statistical information is larger than a preset threshold, and “None” indicates that the value of statistical information is equal to or less than the threshold.
- the cause of failure can be identified based on the comparison between the value of the acquired statistical information and the threshold value and the correspondence information of FIG. The following is an example of identifying the cause of failure.
- the failure cause is “radio noise ⁇ adjacent Channel interference / congestion can be specified and any of “shadowing, multipath fading, radio noise in the vicinity of a connection destination radio station, hidden terminal, no failure” can be specified when it is determined that “no”.
- method 1 + 2 stop communication between itself and the radio base station and stop communication of other wireless terminals communicating on the same channel
- method 1 If “Yes” and method 1 + 2 are determined to be “Yes”, the failure cause is identified as either “radio wave noise / adjacent channel interference”, method 1 is “Yes” and method 1 + 2 is “none” If it is determined that the "congested” can be identified.
- the statistical information used in the scheme 1 + 2 may include, for example, the noise level of the used channel.
- system 1 + 2 and system 1 + 3 stop communication between itself and the radio base station and stop communication of other radio terminals communicating on adjacent channels
- system 1 + 2 If both are determined to be “present”, the cause of the failure is identified as “radio wave noise”, if it is determined to be “present” in method 1 + 2 and “absent” in method 1 + 3, "adjacent channel” Can be identified as “interference”. Further, if it is determined that the method 1 + 2 is "absent” and the method 1 + 3 is "presence”, it can be specified as “congested”.
- the statistical information used in the scheme 1 + 2 may include, for example, the noise level of the used channel.
- Method 1 and Method 4 stop communication of other wireless terminals on the same channel and transmit a Null frame
- Method 1 and Method 4 stop communication of other wireless terminals on the same channel and transmit a Null frame
- scheme 1 and scheme 5 stop communication of other wireless terminals on the same channel, and then transmit a Null frame at a lower transmission rate than scheme 4), respectively. If it is judged as “No” in 5, the cause of failure is identified as "shadowing, hidden terminal, radio noise near the connected radio station, no failure", and “No” in method 1 and “Yes” in method 5. If it is determined, "multipath fading" can be specified.
- the statistical information used in method 5 may include, for example, the number of CRC errors and the number of PLCP preamble synchronization failures.
- FIG. 17 shows an example of correspondence information (second correspondence information) indicating the relationship between the frame loss rate measurement method, the failure factor, and the frame loss rate.
- the failure cause is identified as “hidden terminal, radio wave noise near the connected radio station, no failure” by the method described in FIG. 16, the frame loss rate measured by Null frame transmission (first measurement) is “ If it is determined that it is present, the cause of the failure can be specified as either "hidden terminal / radio wave noise in the vicinity of the connection destination radio station", and if it is determined as “absent”, it can be specified as "no failure”.
- a loss rate measurement (second measurement) of transmitting a Null frame after preventing a frame collision with a hidden terminal using the RTS frame is performed. If the frame loss rate is determined to be “present”, the failure cause can be identified as "radio wave noise in the vicinity of the connection destination radio station", and if it is determined to be “absent”, it can be identified as "hidden terminal”.
- FIG. 18 shows an example of the process flow of the procedure for identifying the cause of failure according to the present embodiment.
- the radio link control unit 13 performs radio link control of method 1 (stops communication with the radio base station A), and during radio link control, the statistical information acquisition unit 11 acquires statistical information (step S41). .
- the radio link control unit executes radio link control according to scheme 1 + 2 (stops communication with the radio base station A and transmits an RTS frame or CTS frame for the same channel) During the radio link control, the statistical information acquisition unit 11 acquires statistical information (step S43).
- step S44 the value of the statistical information acquired in step S43 is compared with the threshold (step S44).
- the radio link control unit 13 executes radio link control according to method 3 (stops communication with the radio base station A and transmits an RTS frame or CTS frame for an adjacent channel), During radio link control, statistical information is acquired by the statistical information unit 11 (step S45).
- step S46 the value of the statistical information acquired in step S45 is compared with the threshold (step S46).
- the cause of failure is identified as "adjacent channel interference”.
- the cause of the failure is identified as "radio noise”.
- the wireless link control unit 13 performs wireless link control according to method 4 (transmission of NULL frame protected by RTS frame), and the statistical information is controlled during wireless link control. get.
- the loss rate measurement unit may be used to transmit the NULL frame (step S51) (in this case, the frame loss rate is also calculated, and the second measurement in FIG. 17 can also be performed simultaneously).
- the radio link control unit 13 performs radio link control according to method 5 (sends a NULL frame protected by RTS frame at a low rate), and performs statistical information during radio link control. Is acquired (step S53).
- the loss rate measurement unit may be used to transmit the NULL frame.
- step S54 the value of the statistical information acquired in step S53 is compared with the threshold (step S54).
- the cause of failure is identified as "shadowing". Also, when the value of the statistical information is larger than the threshold value, the cause of failure is identified as "multipath fading".
- the loss rate measurement unit 14 executes the above-described first measurement (measurement of a frame loss rate due to transmission of a NULL frame) (step S61).
- the frame loss rate and the threshold are compared (step S62), and when the frame loss rate is less than or equal to the threshold, the failure cause is identified as "no failure".
- the loss rate measurement unit 14 executes the second measurement described above (frame loss rate measurement in which protection by RTS frame is performed and a NULL frame is transmitted) (step S63).
- step S63 the frame loss rate obtained in step S63 is compared with the threshold (step S64).
- the failure cause is identified as "hidden terminal”.
- the cause of failure is identified as "radio wave noise in the vicinity of the connection destination radio station".
- the cause of the failure is either “congestion”, “radio wave noise”, “adjacent channel interference”, “shadowing”, “multipath fading”, “hidden terminal”, “radio wave noise in the vicinity of connection destination radio station” or “no failure” It can be identified as one. Therefore, according to the present embodiment, it is possible to accurately identify the cause of failure in wireless communication.
- the threshold value of the statistical information and the threshold value of the frame loss rate can be set to different values individually for each failure cause, and changes in the surrounding environment of the wireless LAN system or the wireless terminal use May be updated dynamically as the application changes.
- the method of estimating the cause of radio interference shown in the present embodiment has an advantage that it can be realized, for example, even in a situation where the connection quality can not be established because the propagation quality is extremely low.
- FIG. 19 is a block diagram showing an example of configuration of a wireless station according to the present embodiment.
- the wireless station 200 (for example, the wireless terminal B in FIG. 1) transmits the frame wirelessly to the communication partner (for example, the wireless base station A in FIG. 1), and receives the frame wirelessly from the communication partner Receiver 201, a retransmission rate measurement unit 204 that measures the retransmission rate from the ratio of the number of transmitted frames to the number of transmitted frames, and the channel usage rate from the ratio of periods in which the channel is in use among predetermined periods.
- the receiving unit 201 receives a radio signal from the antenna, and when the signal strength of the used channel is equal to or higher than a predetermined carrier sense level, the carrier information “busy” is input to the channel usage rate measuring unit 203 and is less than the carrier sense level.
- the carrier information “idle” is input to the channel utilization measurement unit 203 in step S.
- the receiving unit 201 further performs physical layer processing and MAC layer processing on the received signal, and if the received signal contains user data, the user data is input to the upper layer.
- the retransmission control unit 206 is notified that an ACK frame has been received.
- the channel usage rate measuring unit 203 measures the ratio (channel usage rate) of a period in which the carrier information input from the receiving unit 201 is “busy” in a predetermined period (for example, 60 seconds), and has a predetermined timing (for example, 1). Update every millisecond, or when carrier information changes. Further, the channel usage rate measurement unit 203 inputs the measured channel usage rate to the transmission rate control unit 205.
- the retransmission control unit 206 If the retransmission control unit 206 transmits a radio signal and then receives notification that an ACK frame has been received within a predetermined time, the retransmission control unit 206 notifies the transmission unit 202 to transmit the next data, and within a predetermined time period. When it is not notified that the ACK frame has been received, the transmission unit 202 is notified to retransmit the transmitted data. Furthermore, the retransmission control unit 206 notifies the transmission rate control unit 205 of the number of retransmissions of the same frame.
- the retransmission control unit 206 transmits the next data to the transmission unit 202 even when the ACK frame is not received when a predetermined condition (for example, the number of retransmissions or the retransmission time exceeds a predetermined value) is satisfied. You may be asked to
- the retransmission rate measurement unit 204 measures a ratio (retransmission rate) of retransmission frames among a predetermined number (for example, 1000) of frames transmitted by the transmission unit 202, and performs predetermined timing (for example, every one millisecond or frame transmission) Update every time, etc. Furthermore, the retransmission rate measurement unit 204 inputs the measured retransmission rate to the transmission rate control unit 205.
- the transmission rate control unit 205 sequentially changes the transmission rate to a lower value according to a predetermined rule (for example, according to the number of retransmissions notified from the retransmission control unit 206, and when an ACK frame is received in the first transmission, the next The transmission rate of the transmission frame is controlled based on the first transmission rate of data to a value higher than the previous time, and so on.
- a predetermined rule for example, according to the number of retransmissions notified from the retransmission control unit 206, and when an ACK frame is received in the first transmission, the next The transmission rate of the transmission frame is controlled based on the first transmission rate of data to a value higher than the previous time, and so on.
- congestion occurs if the retransmission rate input from the retransmission rate measurement unit 204 exceeds the predetermined threshold A and the channel usage rate input from the channel usage rate measurement unit 203 exceeds the predetermined threshold B, congestion occurs. Judging that it is occurring, it maintains without reducing the transmission rate.
- FIG. 20 is a flowchart showing the flow of the operation of the wireless station 200.
- the threshold A of the wireless station 200 is set to 10% and the threshold B to 60%, the retransmission rate is 5%, the channel usage rate is 70%, and the previous transmission rate is 48 Mbps.
- the retransmission control unit 206 if an ACK frame for the previously transmitted data is not received from the transmitting unit 202 within a predetermined time, the retransmission control unit 206 notifies the transmitting unit 202 to retransmit the transmitted data, and the transmission rate control unit 205 The number of retransmissions (for example, 1) is notified (S211).
- the transmission rate control unit 205 changes the transmission rate of the frame to be retransmitted next to 36 Mbps, which is one step lower, and instructs the transmission unit 202 to retransmit the frame. It notifies (S215).
- the transmitting unit 202 transmits the transmitted data at 36 Mbps based on the retransmission instruction received from the retransmission control unit 206 and the transmission rate received from the transmission rate control unit 205 (S216).
- the transmission rate control unit 205 Since the threshold A is exceeded (Yes in S212) and the channel usage rate exceeds the threshold B (Yes in S213), it is determined that congestion is occurring, and the transmission rate of the next frame to be retransmitted is maintained at 48 Mbps ( S214).
- the transmitting unit 202 transmits a frame addressed to the other party of communication according to the notification of the retransmission control unit 206 and the transmission rate of the transmission rate control unit 205 (S216).
- FIG. 21 is a block diagram showing another configuration example of the radio station according to the present embodiment.
- the wireless station 220 (for example, the wireless terminal B in FIG. 1) transmits the frame wirelessly to the communication partner (for example, the wireless base station A in FIG. 1), and receives the frame wirelessly from the communication partner Reception unit 221, a transmission rate control unit 225 that controls the transmission rate of a frame (in particular, a retransmission frame), a retransmission control unit 226 that controls whether to perform retransmission, and a failure cause estimation unit 223 that estimates the failure cause.
- the failure cause estimation unit 223 includes the statistical information acquisition unit, the statistical information DB, the wireless link control unit, the loss rate measurement unit, and the failure cause identification unit shown in FIG. 2, and the failure cause estimation unit 223 is a wireless link according to the operation of the first embodiment. Estimate the cause of the disorder.
- the transmission rate control unit 205 controls the transmission rate of the transmission frame based on the above-described predetermined rule. However, when the failure cause estimation unit 223 estimates that the failure cause is congestion, the transmission rate is maintained without being reduced.
- FIG. 22 is a flowchart showing the flow of the operation of the wireless station 220.
- the previous transmission rate is 48 Mbps. If the ACK frame for the previously transmitted data is not received from the transmitting unit 222 within the predetermined time, the retransmission control unit 226 notifies the transmitting unit 222 to retransmit the transmitted data, and the number of retransmissions to the transmission rate control unit 225 ( For example, 1) is notified (S231).
- the transmission rate control unit 225 changes the transmission rate of the frame to be retransmitted next to 48 Mbps, which is one step lower, and transmits the frame to the transmission unit 222 Is notified of the resend instruction of the (S235).
- the transmitting unit 222 transmits the already transmitted data at 48 Mbps based on the retransmission instruction received from the retransmission control unit 226 and the transmission rate received from the transmission rate control unit 225 (S236).
- the transmission rate control unit 225 maintains the transmission rate of the next frame to be retransmitted as 48 Mbps (S234).
- the transmitting unit 222 transmits a frame addressed to the other party of communication according to the notification of the retransmission control unit 226 and the transmission rate of the transmission rate control unit 225 (S236).
- the cause of the failure is congestion
- the transmission rate of the retransmission frame is maintained
- the present invention is not limited to the above embodiment as it is, and at the implementation stage, the constituent elements can be modified and embodied without departing from the scope of the invention.
- various inventions can be formed by appropriate combinations of a plurality of constituent elements disclosed in the above embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, components in different embodiments may be combined as appropriate.
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Abstract
Description
図1において、1はネットワーク、Aはネットワーク1に接続した無線基地局(無線局)、2は無線リンク、Bは無線リンク2に接続した無線端末(無線局)を表す。なお、図1には、無線基地局Aに接続する無線端末Bを1台だけ示しているが、複数台の無線端末が接続しても構わない。また、本実施形態では無線通信方式として無線LAN(Local Area Network)を例に説明するが、CSMA/CA(Carrier Sense Multiple Access with Collision Avoidance)に基づく無線通信方式を採用している装置であればどのようなものであっても本発明は適用可能である。
(1)PLCPプリアンブル同期失敗数
(2)PLCPパリティエラー数
(3)PLCP不正レート数
(4)PLCP不正サービス数
(5)CRCエラー数
(6)ノイズレベル
(7)EVM(Error Vector Magnitude)
(方式1)無線局Mと無線局Mが接続する他の無線局との間の通信の停止
(方式2)無線局Mと無線局Mが接続する他の無線局との間の通信と同一チャネルを使用する、他の異なる無線局による当該同一チャネルでの通信の停止
(方式3)無線局Mと無線局Mが接続する他の無線局との間の通信で使用するチャネルの隣接チャネルを使用する他の異なる無線局による当該隣接チャネルでの通信の停止
Claims (11)
- 他の無線局と無線リンクを介して接続され、前記無線リンクの障害原因を特定する無線局であって、
無線リンク制御方式に従って前記無線リンクの無線リンク制御を実行する無線リンク制御部と、
前記無線リンク制御の実行の間、前記無線リンクの状態を表す統計情報を取得する統計情報取得部と、
前記統計情報取得部により取得した統計情報に基づき、あらかじめ統計情報と関連づけられた複数の障害原因の中から、前記無線リンクの障害原因を特定する障害原因特定部と、
を備えた無線局。 - 前記無線リンク制御方式は、
前記他の無線局との通信を停止する方式1、
前記他の無線局と同一チャネルを使用する、前記他の無線局と異なる無線局の通信を停止する方式2、
前記他の無線局の使用チャネルの隣接チャネルを使用する、前記他の無線局と異なる無線局の通信を停止する方式3、
前記他の無線局と同一チャネルを使用する、前記他の無線局と異なる無線局の通信を停止して、前記他の無線局に試験フレームを送信する方式4
前記他の無線局と同一チャネルを使用する、前記他の無線局と異なる無線局の通信を停止して、前記他の無線局に試験フレームを前記方式4よりも低レートで送信する方式5
の少なくともいずれかを含み、
各前記方式のそれぞれに対応して前記統計情報と前記複数の障害原因が関連づけられており、
前記障害原因特定部は、各前記方式のうち実行した方式に応じて前記障害要因を特定する
ことを特徴とする請求項1に記載の無線局。 - 前記無線リンク制御部は、前記方式1を実行し、前記方式1と前記方式2とを同時実行し、
前記障害原因特定部は、前記方式1の実行に対応して得られた統計情報と、前記方式1と方式2との同時実行に対応して得られた統計情報とに基づき、前記無線リンクの障害原因を特定する
ことを特徴とする請求項2に記載の無線局。 - 前記無線リンク制御部は、前記方式1と前記方式3を同時実行し、
前記障害原因特定部は、前記方式1と方式3との同時実行に対応して得られた統計情報に基づき前記無線リンクの障害原因を特定する
ことを特徴とする請求項3に記載の無線局。 - 前記無線リンク制御部は、前記方式4を実行し、
前記障害原因特定部は、前記方式4の実行に対応して得られた統計情報を用いて、前記無線リンクの障害原因を特定する
ことを特徴とする請求項4に記載の無線局。 - 前記無線リンク制御部は、前記方式5を実行し、
前記障害原因特定部は、前記方式5の実行に対応して得られた統計情報を用いて前記無線リンクの障害原因を特定する
ことを特徴とする請求項5に記載の無線局。 - 前記他の無線局に試験フレームを送信し、送信した試験フレームの総数と前記他の無線局からの応答フレームの総数とに基づきフレーム損失率を測定する測定部をさらに備え、
前記障害原因特定部は、さらに、前記フレーム損失率と複数の障害原因との対応を保持しており、前記測定されたフレーム損失率をさらに用いて前記対応に基づき前記無線リンクの障害原因を特定する、
ことを特徴とする請求項6に記載の無線局。 - 前記測定部は、前記他の無線局と異なる無線局による、前記他の無線局と同一チャネルでの通信停止を指示するフレームを送信した上、前記試験フレームを前記他の無線局に送信する
ことを特徴とする請求項7に記載の無線局。 - 前記他の無線局とフレームの送受信を行う通信部と、
前記フレームの再送制御を行う再送制御部と、
前記他の無線局へ再送されたフレームの総数または前記フレームの再送率の増加に応じて前記伝送レートを低下させる伝送レート制御部と、を備え、
前記伝送レート制御部は、前記障害原因が混雑と判定されたときは、前記再送されたフレームの総数または前記フレームの再送率の増加にかかわらず、前記伝送レートを維持する
ことを特徴とする請求項8に記載の無線局。 - 前記障害原因特定部は、前記方式1に対応して得られた統計情報の値が第1閾値より大きく、前記方式4に対応して得られた統計情報の値が第2閾値以下の場合に、前記障害の原因を混雑に特定する
ことを特徴とする請求項9に記載の無線局。 - 前記他の無線局とフレームの送受信を行う通信部と、
前記フレームの再送制御を行う再送制御部と、
前記他の無線局に送信したフレーム数に対する再送フレーム数の割合である再送率を計測する再送率計測部と、
所定の期間のうちチャネルが使用中である期間の割合からチャネル使用率を計測するチャネル使用率計測部と、
前記再送率と前記チャネル使用率に基づいてフレームの伝送レートを制御する伝送レート制御部と、をさらに備え、
前記伝送レート制御部は、前記再送率が閾値Aより大きく前記チャネル使用率が閾値Bより大きいときは前記伝送レートを維持し、前記再送率が閾値A以下または前記チャネル使用率が前記閾値B以下のときは前記伝送レートを低下させる
ことを特徴とする請求項1に記載の無線局。
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Cited By (12)
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JP2014099773A (ja) * | 2012-11-14 | 2014-05-29 | Fujitsu Ltd | 無線監視装置 |
JP2014158204A (ja) * | 2013-02-18 | 2014-08-28 | Buffalo Inc | 無線通信装置、及び、無線通信を行なう方法 |
JPWO2015121902A1 (ja) * | 2014-02-14 | 2017-03-30 | 日本電気通信システム株式会社 | 無線通信端末 |
US10244558B2 (en) | 2014-02-14 | 2019-03-26 | Nec Communication Systems, Ltd. | Transmission control of a wireless communication terminal with transmission loss and collision detection |
JP2017118198A (ja) * | 2015-12-21 | 2017-06-29 | 富士通株式会社 | 無線通信装置、停波判断方法および停波判断プログラム |
JP2017195600A (ja) * | 2016-04-21 | 2017-10-26 | 富士通株式会社 | 故障診断方法、装置及びシステム |
WO2020144987A1 (ja) * | 2019-01-10 | 2020-07-16 | 日本電気株式会社 | 無線通信障害分析装置、無線通信障害分析方法、及び、無線通信障害分析プログラムが格納された記録媒体 |
JPWO2020144987A1 (ja) * | 2019-01-10 | 2021-11-11 | 日本電気株式会社 | 無線通信障害分析装置、無線通信障害分析方法、及び、無線通信障害分析プログラム |
JP7092213B2 (ja) | 2019-01-10 | 2022-06-28 | 日本電気株式会社 | 無線通信障害分析装置、無線通信障害分析方法、及び、無線通信障害分析プログラム |
US11991538B2 (en) | 2019-01-10 | 2024-05-21 | Nec Corporation | Wireless communication failure analysis device, wireless communication failure analysis method, and recording medium having wireless communication failure analysis program stored therein |
JP2023517107A (ja) * | 2020-03-11 | 2023-04-21 | セキュイ コーポレイション | 無線侵入防止システム、これを含む無線ネットワークシステム、及び無線ネットワークシステムの作動方法 |
JP7455220B2 (ja) | 2020-03-11 | 2024-03-25 | セキュイ コーポレイション | 無線侵入防止システム、これを含む無線ネットワークシステム、及び無線ネットワークシステムの作動方法 |
Also Published As
Publication number | Publication date |
---|---|
JP5148756B2 (ja) | 2013-02-20 |
US8824972B2 (en) | 2014-09-02 |
CN102498736A (zh) | 2012-06-13 |
US20120157007A1 (en) | 2012-06-21 |
JPWO2011030466A1 (ja) | 2013-02-04 |
CN102498736B (zh) | 2014-11-12 |
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