JP2017169028A - Wireless lan communication apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To allow for smooth communication by selecting radar's undetected channel quickly, in a wireless LAN communication apparatus having a DFS function.SOLUTION: The control unit 3 of a wireless LAN communication apparatus 1 creates a channel status table CST indicating presence and absence of detection of a radar for each channel, and stores it in a flash memory 5. The control unit 3 creates a channel list CL so that an undetected channel of the radar is selected preferentially from the channel status table CST stored in the flash memory 5, and outputs it to a wireless driver 3d. The wireless driver 3d determines a channel according to the channel list CL, and drives a wireless LAN communication unit 2 to start communication by that channel.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a communication device that performs communication using a wireless LAN (Local Area Network), and in particular, performs communication in a 5 GHz band so that a channel that does not interfere with a radar wave can be quickly selected and communication can be performed efficiently. It relates to the configured communication device.

  In the wireless LAN, the 5 GHz band can be used in addition to the 2.4 GHz band, and data can be communicated at a higher speed. In addition, in both 2.4 GHz band and 5 GHz band, wideband communication can be performed using two channels (channel bonding). In the 5 GHz band, channels 36 ch, 40 ch, 44 ch, 48 ch (collectively referred to as W52), channels 52 ch, 56 ch, 60 ch, 62 ch (generally referred to as W53), and 5.475 using 5.15 to 5.35 GHz. There are channels 100ch, 104ch, 108ch, 112ch, 116ch, 120ch, 124ch, 128ch, 132ch, 136ch, 140ch (collectively referred to as W56) using 5.725 GHz. W52 and W53 can be used indoors only, and W56 can be used both indoors and outdoors.

By the way, in W53 and W56 of 5 GHz band, it may overlap with the frequency region of radar waves such as weather radar and ship radar. For this reason, when a radar wave is detected on the channel used by the wireless LAN communication device (hereinafter referred to as “detecting the radar”), the transmission of the radio wave is stopped, and it becomes clear that the radar wave is detected. Is equipped with a function of moving to another channel (Dynamic Frequency Selection (hereinafter abbreviated as DFS)) in IEEE (Institute of Electrical and Electronics Engineers) 802.11h.

  In this DFS, even after moving the channel, it is necessary to monitor whether radar is detected on that channel for 1 minute. Even if the destination channel can be used, the channel is moved after detecting the radar wave. However, it takes more than one minute before communication can be resumed. Such interruption of communication becomes a serious problem when real-time performance is required, for example, monitoring of a traveling vehicle.

  As a wireless LAN access system having a DFS function, the one described in Patent Document 1 is known. Patent Document 1 discloses a technique for performing communication by selecting a channel in which radar detection is not registered by registering a channel in which radar detection is performed in a radar detection channel management table.

JP 2007-214713 A

  In the wireless LAN system described in Patent Document 1 described above, when determining a channel, only the selection of a channel from which radar detection has not been performed is described, and how the channel is selected is specifically disclosed. Absent. Also, even if a channel has once detected a radar, operation of that channel is permitted if no radar is detected on that channel after 30 minutes have passed since radar detection. For this reason, there is a problem that not only the detection of the radar wave but also the elapsed time after the detection of the radar has to be managed, and the processing becomes complicated.

  An object of the present invention is to provide a wireless LAN communication device that can easily determine a channel for communication and can simplify processing for managing a channel.

In order to solve the above problems, a wireless LAN communication device of the present invention includes a wireless LAN communication unit capable of communication in a 5 GHz band, a storage unit, and a control unit in a wireless LAN communication device having a DFS function. . The control unit performs the following operations. Operate the driver of the wireless LAN communication unit, detect the presence or absence of radar waves for each channel, generate a channel status table, store the channel status table in the storage unit, and store the channel status stored in the storage unit From the table, a list of the first channels in which no radar wave is detected is created, the first channel list is output to the driver, and the channel on which the wireless LAN communication unit communicates based on the first channel list Decide and start communication.

In the wireless LAN communication device of the present invention, the wireless driver receives the first channel list from the control unit and determines the communication channel in the order of the first channel list, so that the channel search process is simplified. . In addition, since only the channels for which the radar has not been detected are described in the first channel list, it is not necessary to manage the elapsed time since the radar detection.

In the wireless LAN communication device according to the present invention, the control unit creates a second channel list, which is a list of channels detected by the radar, from the channel status table stored in the storage unit. When the second channel list is combined with the tail of the channel list and output to the driver, and radar waves are detected in all the channels included in the first channel list, the channel stored in the storage unit The status of all channels in the status table is set to no radar detection, and the driver is caused to try communication on the channels included in the second channel list.

  When the radar is detected on all channels in the first channel list, the wireless LAN communication device according to the present invention tries using the second channel list and communicates using a channel that does not detect the radar. Although the radar is detected once in the channels included in the second channel list, there is a possibility that 30 minutes have passed since the radar was detected and a channel that can be currently operated is included.

Furthermore, in the wireless LAN communication device of the present invention, the wireless LAN communication unit is capable of 2.4 GHz band communication, and the control unit includes all channels included in the first channel list and the second channel list. When a radar wave is detected in, communication can be performed on a predetermined channel in the 2.4 GHz band. That is, the wireless LAN communication device of the present invention can perform communication using a 2.4 GHz band channel that is not affected by the radar when radar is detected on all channels in the 5 GHz band.

Furthermore, in the wireless LAN communication device of the present invention, since the channel status table is stored in a nonvolatile memory, the channel status table is saved even when the power is turned off. There is no need to generate a new channel status table after power-on, and communication can be started immediately.

1 is a block diagram illustrating a configuration of a vehicle-mounted wireless LAN communication device according to an embodiment of the present invention. It is a figure explaining the outline of the system of a wireless LAN communication apparatus. It is a flowchart which shows the operation | movement which produces the channel status table of a wireless LAN communication apparatus. It is a figure explaining a channel status table. It is a figure explaining a channel status table and a channel list. It is a flowchart which shows the operation | movement which updates the channel status table of a wireless LAN communication apparatus. It is a flowchart which shows the operation | movement which updates the same channel status table. It is a figure explaining the update of the channel status table in the band 20MHz (HT20). It is a figure explaining the update of the channel status table in band 40MHz (HT40).

Embodiments of the present invention will be described below with reference to FIGS. In this embodiment, a wireless LAN communication device attached to a vehicle mainly used outdoors will be described as an example. The wireless LAN communication device 1 includes a wireless LAN communication unit 2 and a control unit 3. The wireless LAN communication unit 2 is connected to the control unit 3 via a PCI (Peripheral Component Interconnect) bus 12 and operates as an access point in an infrastructure mode in accordance with the IEEE 802.11 standard based on the control of the control unit 3. For example, a notebook personal computer PC is connected to the wireless LAN communication unit 2 as a station, but it is also possible to communicate with a smartphone or a double instead of the notebook personal computer PC. Reference numeral 2a denotes an antenna for a wireless LAN communication unit.

  The control unit 3 includes an SOC (System On Chip), and various I / Fs such as a CPU core 3a, a PCI interface (I / F) 3b, and a CAN (Control Area Network) I / F 3c are formed on one chip. Is formed. The CAN I / F 3c is connected to an ECU (Engine Control Unit) (not shown) in the vehicle via a CAN bus 11, receives data on the CAN bus 11, and transmits it to an external PC. Data can be sent to the CAN11 bus.

  The control unit 3 is connected to a DDR SDRAM (Double Data Rate Synchronous Random Access memory) 4, a flash memory 5, and an eMMC (Embedded Multi Media Card) 6 as storage devices. The DDR SDRAM 4 is used as a work area of the control unit 3 and stores the developed operation system (OS), wireless driver, application, and data being processed.

  The flash memory 5 stores data that should be retained even when the power is off, such as a channel status table CST described later. The eMMC 6 stores an OS, a wireless driver, and application programs. At startup, the control unit 3 reads these programs and develops them on the DDR SDRAM 4.

  An LED display unit 7 and a switch 8 are connected to the control unit 3. The LED display unit 7 includes a plurality of multi-color LEDs (Light Emitting Diodes) 7a, 7b, 7c, and 7d, and can notify the user of the power supply state and the wireless communication state. The switch 8 is a waterproof switch, and is used to activate wireless LAN automatic setting (Wi-Fi (registered trademark) Protected Setup (WPS)).

  An image processing unit 9 is connected to the control unit 3. The image processing unit 9 combines the images taken by the four video cameras 10-1, 10-2, 10-3, and 10-4 attached at appropriate positions on the vehicle into a single screen and controls the control unit. 3 is output. The synthesized image is compressed by the control unit 3 and transmitted from the wireless LAN communication unit 2 to the PC, and an image captured by each video camera can be displayed on the display unit of the PC.

The wireless LAN communication device 1 is housed in a waterproof case 1a, and only the antenna 2a terminal, LED display unit 7, switch 8 button, CAN bus 11 terminal, camera connection terminal, and power supply terminal are external. Exposed to. The power is supplied from a battery (not shown) of the vehicle, and the power is supplied only while the ignition key of the vehicle is on. In other words, when the ignition key is off, the wireless LAN communication device 1 is completely stopped.

Next, the operation of the wireless LAN communication device 1 will be described. First, an outline of the system configuration of the wireless LAN communication device 1 will be described with reference to FIG. The control unit 3 executes the wireless driver 3d and the communication application 3e. The wireless driver 3d is a program that bridges the wireless LAN communication unit 2 and the communication application 3e. An event such as a radar detected by the wireless LAN communication unit 2 is transmitted to the communication application 3e via the wireless driver 3d. The communication application 3e is given a channel list and the like to be described later to the wireless driver 3d.
The wireless driver 3d notifies the wireless LAN communication unit 2 that communication is attempted on a channel in the channel list. In the following description, the operation of the communication application 3e of the control unit 3 will be described as the operation of the control unit 3.

Next, creation of a channel status table will be described with reference to FIGS. In the following description, a W56 channel that can be used outdoors will be described. Since the same applies to W53, the description of W53 is omitted.

FIG. 4A shows a channel status table CST. In the “channel” column of the channel status table CST, channels are assigned in order from the channel 100 ch having the lowest frequency. In the “status” column, the presence or absence of radar detection is entered. This channel status table CST is stored in the flash memory 5.

  In step S1 of FIG. 3, the control unit 3 sets a start channel. As shown in FIG. 4A, since the top channel of the channel status table CST is 100 ch, the control unit 3 sets 100 ch as the start channel. The wireless LAN communication unit 2 receives radio waves at 100 ch (Listen) and informs the control unit 3 via the wireless driver 3d whether or not the radar is detected.

  The control unit 3 determines whether or not the radar is detected in 100ch (step S2). If the radar is detected (in the case of Yes), the process branches to the process in step S3, and the channel status table CST is set to 100ch. Enter "1" in the row. If the radar is not detected (No), the process branches to step S4, and “0” is entered in the 100 ch row of the channel status table CST. In FIG. 4B, since the radar is detected at 100 ch, “1” indicating detection is entered in the status.

  Next, the control unit 3 determines whether or not radar detection is checked for all target channels (step S5). Since the determination is naturally No at the stage where 100-ch detection is checked, the control unit 3 shifts to the next channel 104ch (step S6), returns to step S2, and determines whether or not the radar is detected. If the radar is not detected in 104ch, the determination in step S2 is “No” and the process branches to step S4. Then, “0” indicating that the radar is not detected is written in the 104ch status of the channel status table CST. FIG. 4B shows that “0” is entered for 104ch in the channel status table CST.

  When the control unit 3 finishes checking all the target channels, the control unit 3 branches to the determination in step S7. FIG. 5 (a) shows a channel status table CST in a state where all the channels have been checked. In FIG. 5A, the status is “1” at 100 ch and 128 ch, and it can be seen that the radar is detected at 100 ch and 128 ch. In other channels, the radar is not detected, so the status is “0”.

  Next, the control unit 3 determines whether all the statuses of the channel status table CST are “1” (step S7). If the determination in step S7 is “Yes”, the process branches to step S8, and all the statuses in the channel status table CST are changed to “0”. Then, the control unit 8 proceeds to the process of step S9 and creates a channel list. If the determination in step 7 is “No”, the control unit 8 branches to the process in step 9 to create a channel list.

  In step S9, a channel list CL is created. The creation of the channel list will be described with reference to FIG. In FIG. 5B, the channels are rearranged so that the channel whose status is “0” comes up. A portion in which channels with a status of “0” are arranged is defined as a white channel list WCL. A channel having a status of “1” is referred to as a black channel list BCL. The white channel list corresponds to the “first channel list”, and the black channel list corresponds to the “second channel list”. In FIG. 5B, the arrangement of the table is changed for convenience of explanation, but it is not necessary to rearrange the channel status table CST stored in the flash memory 5.

  As shown in FIG. 5C, a channel list CL obtained by combining the white channel list WCL and the black channel list BCL is passed to the wireless driver 3d. Only the white channel list WCL may be passed to the wireless driver 3d. The wireless driver 3d tries communication from the channel on the channel list CL. In the example of FIG. 5C, communication is first attempted on the channel 104ch. If radar is not detected on channel 104ch, communication is performed using 104ch.

  5C shows a channel list used when the band is 20 MHz (HT20), and FIGS. 5D and 5E show the channel list when the band is 40 MHz (HT40). Yes. In the channel list CL1 in FIG. 5D, for example, 108ch indicates that communication is performed in a wide band using 108ch and 112ch. In the channel status table CST of FIG. 5A, since the statuses of both 108ch and 112ch are “0”, it is possible to perform communication by combining these two channels. 116 ch and 132 ch can be similarly communicated by the HT 40. That is, 108 ch, 116 ch, and 132 ch constitute the white channel list WCL1.

The second 100 ch from the bottom of the channel list CL1 has a status of “1” in the channel status table CST in FIG. 5A. Cannot communicate with HT40. The 124 ch at the bottom of the channel list CL1 is not detected because the status of the channel status table CST of FIG. 5A is “0” in FIG. 5A, but is not detected by the 128 ch. And 128ch cannot be connected to perform HT40 communication. That is, 100ch and 124ch constitute the black channel list BCL1.

The channel 104ch at the top of the channel list CL2 in FIG. 5 (e) has a status of “0” according to the channel status table CST in FIG. 5 (a), and the radar is not detected. Similarly, since no radar is detected in 108ch, it is possible to perform communication of HT40 by combining 104ch and 108ch. Similarly, HT40 communication is possible on 112ch, 120ch, and 136ch. That is, 104 ch, 112 ch, 120 cg, and 136 ch constitute the white channel list WCL2.

Since the status of the channel status table CST in FIG. 5A is “1”, the lowest 128 channels in the channel list CL2 in FIG. 5E are 128ch and 132ch even if 132ch is not detecting the radar. HT40 communication cannot be performed by combining the two. This 132ch constitutes the black channel list BCL2.

  Next, channel status table CST update processing will be described with reference to FIGS. This update process is always executed. The control unit 3 acquires an event from the wireless driver 3d (FIG. 6, step S11). Next, the control unit 3 determines the type of event (step S12). If the event is “detect radar with one channel”, the control unit 3 branches to the process of step S13. The control unit 3 acquires the channel X from which the radar is detected from the wireless driver 3d (step S13).

  The control unit 3 determines whether the current band is HT20 or HT40 (step S14). When the bandwidth is HT20, the control unit 3 branches to the process of S18 and updates the Xch status of the channel status table CST from “0” to “1”. FIG. 8A shows a case where radar is detected at 104 ch. In this case, as shown in FIG. 8B, the control unit 3 updates the status of 104ch in the channel status table CST to “1”. Then, the control part 3 returns to the process of step S11.

  If the control unit 3 determines in step S14 that the band is HT40, it determines whether the Xch is a lower channel or an upper channel (step S15). If it is the lower channel, the process branches to S16, and the statuses of Xch and (X + 4) ch in the channel status table are updated to “1”. If the channel is the upper channel, the process branches to step S17, and the statuses of Xch and (X-4) ch in the channel status table CLT are changed to "1". When the process of step S16 or step S17 ends, the control unit 3 returns to the process of step S11.

  The case of HT40 will be further described with reference to FIG. 9A, the channel list CL1 shown in FIG. 5D is shown on the left side in the figure, and the channel status table CST is shown on the right side in the figure. Note that a part of the channel status table CST is omitted. Here, “108 ch” indicates that communication of the HT 40 is performed using 108 ch and 112 ch. In this case, it is a requirement that the radar is not detected in both 108ch and 112ch.

In FIG. 9A, it is assumed that the radar is detected at 108 ch. In other words, this corresponds to the case where it is determined in step S15 that the channel is the lower channel. In this case, not only the status of channel 108 in channel status table CST is updated to “1”, but also the status of channel 112 not detected by the radar is updated to “1” (step S16).

In FIG. 9B, it is assumed that the radar is detected at 112ch. That is, it corresponds to the case where it is determined in step S15 that the channel is the upper channel. In this case, not only the status of channel 112 in the channel status table CST is updated to “1”, but the status of channel 108 not detected by the radar is also updated to “1” (step S17). Here, the channel list CL1 has been described, but the same applies to the channel list CL2 shown in FIG.

  Returning to FIG. 6 again, when it is determined that the signal is usable in step S12, that is, when radar is detected in all channels in the white channel list WCL, the control unit 3 proceeds to step S19 in FIG. The status of all channels in the status table CST is changed to “0”. This is because the channels included in the black channel list BCL may be in a state where the radar is not detected thereafter, so that all channels can be reset to search for channels that can be communicated.

  If radar is detected for all channels of WCL and BCL in step S12, the process proceeds to step S20 in FIG. 7, and in this case, all the statuses in the channel status list CST are set to “0”. Then, the 5 GHz band is changed to the 2.4 GHz band, and communication is attempted using 1ch (step S21). In addition, although it has shifted to 1ch of the 2.4 GHz band here, any channel of 2ch to 13ch may be used.

  The wireless LAN communication device 1 maintains the channel status table CST as it is in the flash memory 5 even when the power is turned off. Next, when the power is turned on, the control unit 3 creates a channel list CL from the stored channel status table CST and outputs it to the wireless driver 3d. When the radar is in a fixed position, such as a weather radar, the radar is always detected on the same channel. Communication can be started on possible channels.

  In the above embodiment, the wireless LAN device mounted on the vehicle has been described. However, the present invention is widely applicable to devices that construct a wireless LAN using 5 GHz bands W53 and W56, such as a wireless LAN access point used in an office or factory. Applicable.

  The present invention is applicable to wireless LAN communication devices used in 5 GHz bands W53 and W56 having a DFS function.

1: Wireless LAN communication device 2: Wireless LAN communication unit 2a: Antenna 3: Control unit 3a: CPU core 3b: PCI I / F
3c: CAN I / F
3d: Wireless driver 3e: Communication application 4: DDR SDRAM
5: Flash memory 6: eMMC
7: LED display parts 7a, 7b, 7c, 7d: LED
8: Switch 9: Image processing circuits 10-1, 10-2, 10-3, 10-4: Video camera 11: CAN bus 12: PCI bus CST: Channel status tables CL, CL1, CL2: Channel lists WCL, WCL1 , WCL2: White channel list BCL, BCL1, BCL2: Black channel list

Claims (4)

In a wireless LAN communication device having a DFS function,
A wireless LAN communication unit capable of communication in the 5 GHz band;
A storage unit;
With a control unit,
The controller is configured to perform the following operations:
Operate the driver of the wireless LAN communication unit,
Let the wireless LAN communication unit detect the presence or absence of radar waves for each channel, generate a channel status table,
Storing the channel status table in the storage unit;
From the channel status table stored in the storage unit, create a list of first channels in which radar waves are not detected,
A wireless LAN communication characterized by outputting a list of first channels to the driver, causing the driver to determine a channel for communication based on the first channel list, and starting communication by the wireless LAN communication unit machine. The wireless LAN communication device according to claim 1,
The control unit creates a second channel list, which is a list of channels detected by the radar, from the channel status table stored in the storage unit, and a second channel list at the end of the first channel list. And
When radar waves are detected in all the channels included in the first channel list, the status of all channels in the channel status table stored in the storage unit is set to no radar detection, and the driver receives the second channel list. A wireless LAN communication device which causes communication to be tried on a channel included in the network. The wireless LAN communication device according to claim 2,
The wireless LAN communication unit is capable of 2.4 GHz band communication,
The control unit performs communication on a predetermined channel in a 2.4 GHz band when radar waves are detected in all channels included in the first channel list and the second channel list. LAN communication equipment. The wireless LAN communication device according to any one of claims 1 to 3,
The wireless LAN communication device, wherein the storage unit is a nonvolatile memory.

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