JP3915021B2 - Channel selection method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a channel selection method for a wireless communication system, and more particularly to a channel selection method for selecting a channel to be used during wireless communication from a plurality of selection target channels including channels that can be used redundantly in a plurality of wireless communication systems. Is.
[0002]
[Prior art]
In recent years, there is a wireless LAN system as a wireless communication system that has been studied as a system for realizing high-speed data transmission by wireless.
In this type of wireless LAN system, a plurality of wireless stations form one wireless link, and each wireless station constituting the wireless link has one wireless channel by CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance). (Hereinafter referred to as a channel).
[0003]
Here, according to CSMA / CA, each radio station determines that another radio station is using a channel when the interference wave power level of a signal from the other radio station exceeds a certain level. Therefore, no transmission is performed.
Therefore, in order to perform efficient communication in a wireless communication system such as a wireless LAN system, a channel is selected so as to receive as little interference waves as possible from wireless stations other than the wireless stations constituting the wireless link. Is important.
[0004]
In this case, as a radio station that transmits a signal that becomes an interference wave, a radio station that configures another radio link in the own radio communication system that uses the same channel and another radio station that uses the same frequency band. There are two types of wireless stations in the wireless communication system. Conventionally, in such a wireless LAN system, a technique for avoiding interference from wireless forming different wireless links has been proposed (for example, Ishii et al. “Proposal of Wireless LAN Packet DCA” 1996, Electronic Information Communication (See the Society Society Conference Proceedings, B-652, etc.).
[0005]
This is because when an arbitrary radio station newly transmits and receives a control packet when a radio link is formed and a control packet returned from another radio station is received in accordance with this, the channel is transmitted to the own radio communication system. To avoid interference with other radio stations of the own radio communication system by selecting a channel that is judged to be used by another radio station and has not received a control packet from the other radio station. It is a thing.
[0006]
On the other hand, as a radio device capable of avoiding interference from radio stations of different radio communication systems sharing a frequency band, a channel is detected by another radio communication system by detecting the reception level, signal length, and periodicity of the received signal. It has been proposed that the use of channels used by other wireless communication systems is avoided (see, for example, Japanese Patent Laid-Open No. 4-189700).
[0007]
[Problems to be solved by the invention]
However, in such a conventional channel selection method of a radio communication system, both the former and the latter are means for detecting the presence or absence of interference from a radio station of the own radio communication system, or an interference wave from a radio station of another radio communication system. Therefore, it is not possible to select a channel that minimizes the influence of interference waves from different radio stations belonging to the own radio communication system and the other radio communication system. In the communication system and other wireless communication systems, there has been a problem that frequency bands cannot be used efficiently.
[0008]
In particular, in the former channel selection method, the use state of the channel is determined by the control packet, but the same control packet is not always used in other wireless communication systems, and the same control packet is used. Even if the communication method is different, it is not always possible to correctly receive and analyze control packets of other wireless communication systems.
Therefore, the former channel selection method cannot be applied to both the own radio communication system and other radio communication systems.
[0009]
Further, in the latter channel selection method, the channel usage status is determined by detecting the reception level, signal length, and periodicity of the received signal, so whether the interference is from another radio communication system or the own radio It cannot be determined by distinguishing from other radio stations in the communication system.
Therefore, the latter channel selection method cannot be applied to both the own radio communication system and other radio communication systems.
The present invention is intended to solve such problems, and an object of the present invention is to provide a channel selection method for a radio communication system that can effectively share a frequency band between the own radio communication system and another radio communication system. .
[0010]
[Means for Solving the Problems]
In order to achieve such an object, the present invention relates to a channel used by another radio communication system in a state where the own radio communication system and other radio communication systems each consisting of a plurality of radio stations coexist. In a wireless communication system that selects a channel to be used at the time of wireless communication in the own wireless communication system from a plurality of selection target channels including, the channel usage status of each selection target channel by the own wireless communication system and each selection target by another wireless communication system The channel usage status of the channel is investigated, and the channel used at the time of wireless communication in the own wireless communication system is selected from the selection target channels based on the investigation results.
Therefore, the channel is selected based on the investigation results of both the usage status of each selection target channel by the own radio communication system and the usage status of each selection target channel by the other radio communication system.
[0011]
Also, as an investigation of the channel usage status of the selection target channel by the other radio communication system, the own radio communication system that detects the interference wave power of each selection target channel and extracts based on the channel usage status of the selection target channel by the own radio communication system The channel with the lowest interference wave power is selected from the unused channels to be selected.
In addition, a predetermined reference level is set in advance, and a channel used at the time of wireless communication in the own wireless communication system is selected from channels whose interference wave power of each channel is smaller than the predetermined reference level. is there.
[0012]
In addition, a shared channel with another wireless communication system is registered in advance, and a channel other than the shared channel is preferentially selected.
Further, a predetermined shared reference level is set in advance, and a channel to be used at the time of wireless communication in the own wireless communication system is selected from channels whose interference wave power of each shared channel is smaller than the predetermined shared reference level. It is a thing.
[0013]
Further, when a predetermined restriction reference level is set in advance and the interference wave power of each channel is larger than the predetermined reference level, a channel whose interference wave power is smaller than the predetermined restriction reference level is selected and the channel Is set to a lower limit transmission power than usual.
Further, the common reference level, the restriction reference level, or the restriction transmission power is individually set for each selection target channel.
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Next, the present invention will be described with reference to the drawings.
FIG. 1 is a schematic diagram showing a radio communication system according to a first embodiment of the present invention, in which base stations 1 to 3 connected to a wired network 8 and a plurality of base stations and mobile stations 4 to 7 A wireless communication system 10A including a plurality of mobile stations and another wireless communication system 10B including a plurality of wireless stations 11, 12 and the like are mixed.
Note that a wireless station includes all devices that perform wireless communication, such as base stations and mobile stations.
[0015]
Mobile station 4,5 A plurality of other mobile stations connect to the base station 1 for communication. Base station 1 is a mobile station 4,5 In addition to communicating with a plurality of mobile stations connected to the local station using a single channel (CH1), the mobile station 4,5 In addition, even when a plurality of mobile stations connected to the base station 1 communicate with each other, communication is performed using CH1, which is a channel used by the base station 1.
[0016]
Similarly, the mobile stations 6 and 7 and a plurality of mobile stations communicate by connecting to the base station 3.
The base station 3 communicates with the mobile stations 6 and 7 and other mobile stations connected to its own station using a single channel (CH2), and also connects the mobile stations 6 and 7 and other base stations 3 Even when the mobile stations communicate with each other, communication is performed using CH2, which is a channel used by the base station 3.
[0017]
Note that CH1 and CH2 may be the same channel.
Here, the channel refers to a frequency band used for wireless communication.
On the other hand, the radio stations 11 and 12 constitute another radio communication system 10B different from the base stations 1 to 3 and the mobile stations 4 to 7, and perform communication using a single channel (CH10) or a plurality of channels.
[0018]
Note that CH10 and the plurality of other channels used in other radio communication system 10B may be the same channels as those used in own radio communication system 10A such as CH1 and CH2.
Further, these channels are channels that overlap with the channels used in the own radio communication system 10A, such as CH1 and CH2, or a part of the frequency band that overlaps the frequency bands of the plurality of channels used in the own radio communication system 10A. There may be.
[0019]
FIG. 2 is a block diagram illustrating a channel selection processing unit included in the base stations 1 to 3 in FIG.
The channel selection processing unit includes a control packet transmission / reception unit 21, a reception power measurement unit 22, a channel selection control unit 23, and a channel selection information registration unit 24.
The control packet transmitting / receiving unit 21 transmits a control packet for channel selection control in response to a control packet transmission instruction signal from the channel selection control unit 23, and when receiving a control packet from another wireless station, the contents of the packet Is notified to the channel selection control unit 23 using a control packet reception notification signal.
[0020]
The reception power measuring unit 22 monitors each wireless channel that can be selected during wireless communication, that is, each selection target channel, and receives the received power for each packet and the interference wave power for each channel in the channel selection control unit 23. Notify as level signal or interference wave level signal.
Here, the level of the interference wave power is given by averaging the received power of each channel over time.
[0021]
The channel selection control unit 23 checks the usage status of each selection target channel based on the reception state and received power of the control packet, and selects and sets a channel to be used in the own station from among the selection target channels.
The channel selection information registration unit 24 records and stores the status of each channel notified by the registration cancellation signal from the channel selection control unit 23, and stores control information set for each channel by the user or manufacturer. In response to the registration confirmation signal from the selection control unit 23, the channel status is notified using a registration confirmation response signal.
[0022]
Next, with reference to FIGS. 1 to 3, a basic processing procedure for channel selection in the base station will be described as an operation of the present invention.
Here, a case where a channel is selected in the base station 2 of FIG. 1 will be described as an example. First, the channel selection control unit 23 of the base station 2 selects one arbitrary uninvestigated channel from among a plurality of selection target channels (step 301), and the channel usage status by other radio stations of the own radio communication system 10A In order to investigate, the control packet is transmitted / received to / from other radio stations of the own radio communication system 10A (step 302).
[0023]
Subsequently, the channel usage status in the other radio communication system 10B (further, the status of other radio stations in the own radio communication system 10A in which the control packet has not been correctly transmitted / received due to a communication environment problem such as a long distance) is investigated. Therefore, the interference wave power of the channel is detected and recorded in the channel selection information registration unit 24 (step 303).
Note that the processing order of step 302 and step 303 can be switched.
[0024]
In this manner, the selected arbitrary channel is investigated, and it is determined whether or not all the channels to be selected have been investigated (step 304). If the investigation has not been completed (step 304: NO), step Returning to 301, one other uninvestigated channel is selected from the channels to be selected (step 301), and the investigation is performed in steps 302 and 303 described above.
[0025]
When all channels to be selected have been investigated (step 304: YES), the investigation result of each channel, that is, whether there is a response from the radio station of the own radio communication system 10A, and the level of interference wave power Based on this, a channel to be used is selected (step 305).
An example of the channel selection procedure here will be described later with reference to FIGS.
[0026]
As described above, both the channel usage status of the own radio communication system 10A and the channel usage status of the other radio communication system 10B are examined, and the channel is selected based on these results. Even in this case, a channel can be selected while avoiding interference with the own radio communication system 10A and the other radio communication system 10B, and the frequency bands can be effectively shared with each other in both radio communication systems.
[0027]
Next, with reference to FIG. 4, an example of a processing procedure (FIG. 3: step 302) for investigating the channel usage status by the own wireless communication system will be described in detail.
The base station 2 that performs channel selection first broadcasts a control packet (hereinafter referred to as a response request packet) requesting a response to another radio station of the own radio communication system 10A using the investigation target channel (step 401). ).
Here, it is assumed that other base stations and mobile stations of the own radio communication system 10A that have received the response request packet return a predetermined response packet.
[0028]
After transmitting the response packet, the base station 2 starts a timer that times a predetermined period (step 402).
The measurement time of this timer is set in the control information registration unit 24.
Thereafter, until the timer times out (step 404: YES), the latest information notified by each received response packet is recorded in the control information registration unit 24 (step 403).
[0029]
In the response packet, information such as a MAC address for distinguishing the transmission source radio station and information indicating the received power of the received response packet notified from the received power measuring unit 22 are recorded.
Thereafter, the series of processes, that is, the process of step 302 is terminated according to the timeout of the timer (step 404: YES).
[0030]
As another embodiment of step 302, each wireless station may periodically broadcast a response packet.
Thereby, each wireless station receives information notified from the reception power measuring unit 22 and information such as a MAC address for distinguishing the transmission source wireless station in response to reception of a response packet broadcast from another wireless station. The latest information indicating the received power of the response packet is sequentially recorded in the control information registration unit 24, so that transmission of the response request packet in step 401 can be omitted and the processing time can be shortened.
[0031]
Next, with reference to FIG. 5, an example of the channel selection procedure (FIG. 3: step 305) based on the investigation result will be described in detail.
The base station 2 that performs channel selection first determines whether there is a channel that has not received a response packet (step 501). If there is a channel that has not received a response packet (step 501: YES), It is determined that the channel is a channel that is not used by other radio stations in the own radio communication system, that is, an unused channel, and all channels that have not received response packets are extracted (step 502).
[0032]
Then, the extracted interference wave power of each channel is compared with a reference level registered in advance in the channel selection information registration unit 24 (step 503). If there is a channel with interference wave power lower than the reference level ( Step 504: YES), a channel having the smallest interference wave power and the lowest possibility of being used in the other radio communication system 10B is selected (Step 505), and the series of processing, that is, Step 305 is completed.
[0033]
On the other hand, if there is no channel below the reference level, no channel is selected (step 506), and the series of processing is terminated.
In addition, you may transfer to step 505 after step 502.
If response packets are received from all channels in step 501 (step 501: NO), the channel with the smallest reception power of the response packet is selected from all channels (step 505), and a series of processing is performed. finish.
[0034]
As described above, since the channel with the lowest interference wave power is selected from the selection target channels unused in the own radio communication system 10A (steps 501, 502, and 505), the channel not used in the own radio communication system 10A is selected. A channel that is in use and has the lowest possibility of being used in the other radio communication system 10B can be selected accurately.
[0035]
In addition, since the channel to be selected that is not used in the own radio communication system 10A and the interference wave power is lower than the reference level, the channel used at the time of radio communication is selected (steps 501 to 504). ), A channel that is not used in the own radio communication system 10A, has an interference wave power smaller than the reference level, and can effectively communicate with each other while suppressing the mutual influence between the own radio communication system 10A and another radio communication system 10B Can be selected.
[0036]
In addition to this, since the channel with the smallest interference wave power is selected (steps 501 to 505), the channel is unused in the own radio communication system 10A, and the interference wave power is smaller than the reference level. A channel that has the lowest mutual influence between 10A and the other wireless communication system 10B and can be satisfactorily communicated can be accurately selected.
[0037]
Furthermore, when all the selection target channels are in use in the own radio communication system 10A, the channel with the lowest interference wave power is selected from each selection target channel (steps 501 and 507). Even if all the channels to be selected in the system 10A are in use, it is possible to accurately select the channel that is least likely to be used in the other radio communication system 10B.
[0038]
Next, with reference to FIG. 6, another example of the channel selection procedure (FIG. 3: step 305) based on the investigation result will be described in detail.
Here, a channel that may be used also from other radio communication system 10B (see FIG. 1), that is, a shared channel is assumed to be registered in advance as shared channel information in the channel selection information registration unit 24. These channels are not used in the other radio communication system 10B.
[0039]
Note that FIG. 6 is obtained by replacing only steps 503 to 505 in FIG. 5 described above, and other steps are the same as those in FIG.
First, when there is a channel that does not receive a response packet (step 501: YES), the base station 2 that performs channel selection extracts all channels that have not received a response packet, that is, unused channels (step 502). Then, it is determined whether there is any channel that is not a shared channel (step 601).
[0040]
If there is a channel that is not a shared channel (step 601: YES), the channel with the smallest interference wave power is selected from these channels (step 602), and the series of processing, that is, step 305 is completed. .
On the other hand, in the case of all shared channels (step 601: NO), the interference wave power of all unused shared channels is compared with the shared reference level recorded in the channel selection information registration unit 24 (step 603). ).
[0041]
As a result, when there is a channel whose interference wave power is lower than the common reference level (step 604: YES), a channel having the minimum interference wave power is selected (step 605), and the series of processing ends. .
If there is no channel whose interference wave power falls below the common reference level in step 604 (step 604: NO), no channel is selected (step 606), and the series of processes is terminated.
[0042]
In addition, you may make it transfer to step 605 after step 601: YES.
As described above, when the channel shared by the other radio communication system 10B is known in advance, the interference wave power is the lowest among the channels not used in the own radio communication system 10A and other than the shared channel. Since the channel is selected (steps 501, 502, 601, 602), it is possible to accurately select a channel that is not used in the own radio communication system 10A and the other radio communication system 10B.
[0043]
In addition, the channel used at the time of wireless communication is selected from among the shared channels unused in the own wireless communication system 10A and the interference wave power is smaller than the shared reference level (steps 501, 502, 601). ˜604), a shared channel that is not used in the own radio communication system 10A, has a lower interference wave power than the common reference level, and is good while suppressing the mutual influence between the own radio communication system 10A and the other radio communication system 10B. Channels that can be communicated to each other can be selected accurately.
[0044]
In addition to this, since the channel with the smallest interference wave power is selected (steps 501, 502, 601 to 605), the own radio communication system 10A and the other radio communication systems have an interference wave power smaller than the common reference level. A channel that has the lowest mutual influence between 10B and can be satisfactorily communicated can be accurately selected.
[0045]
The common reference level may be set to an individual value for each channel.
As a result, even if the degree of influence is different due to the difference in the degree of overlap with the frequency band of the other radio communication system 10B, the difference in communication method, and the presence of multiple other radio communication systems 10B, it is optimal for each channel. Various selection conditions can be set.
[0046]
Next, another example of the channel selection procedure (FIG. 3: step 305) based on the investigation result will be described in detail with reference to FIG.
Here, a channel that may be used from other wireless communication system 10B (see FIG. 1), that is, a shared channel is assumed to be registered in the channel selection information registration unit 24 as shared channel information. It is assumed that the channel is not used in the other radio communication system 10B.
[0047]
Note that FIG. 7 shows only a part that is replaced by the above-described step 506 in FIG. 6, and other steps are the same as those in FIG. 6.
The base station 2 that performs channel selection, in step 604, when all the channels that are not used in the own radio communication system 10A are shared channels and the interference wave power of these shared channels exceeds the shared reference level ( Step 604: NO), the interference wave power of these shared channels is compared with the restriction reference level recorded in the channel selection information registration unit 24 (step 701).
[0048]
Here, if there is a channel that is below the limit reference level (step 702: YES), a channel with the smallest interference wave power is selected from the channels (step 703), and transmission power when this channel is used. Is set to a predetermined limited transmission power lower than normal (step 704), and a series of processing, that is, step 305 is ended.
[0049]
Thereby, also when selecting the channel currently used in the other radio | wireless communications system 10B, the influence which it has on the other radio | wireless communications system 10B by suppressing transmission power can be suppressed.
In FIG. 7, the case of applying to step 506 of FIG. 6 described above is described as an example. However, it may be applied to step 506 of FIG. 5, and the same effect as described above can be obtained.
[0050]
On the other hand, when there is no channel below the restriction reference level (step 702: NO), no channel is selected (step 506), and the series of processes is terminated.
Here, the restriction reference level may be set to an individual value for each channel.
[0051]
In addition, the limited transmission power in the channel used at that time can be individually set for each channel.
As a result, even if the degree of influence is different due to the difference in the degree of overlap with the frequency band of the other radio communication system 10B, the difference in communication method, and the presence of multiple other radio communication systems 10B, it is optimal for each channel. Various selection conditions can be set.
[0052]
【The invention's effect】
As described above, the present invention investigates both the channel usage status of each selection target channel by the own radio communication system and the channel usage status of each selection target channel by another radio communication system, and based on these survey results. Thus, the channel used at the time of wireless communication in the own wireless communication system is selected.
Therefore, even when a plurality of radio communication systems coexist, interference with other radio stations of the own radio communication system and other radio stations of the other radio communication system is avoided as much as possible, and The channel used at the time of wireless communication can be selected, and the frequency band can be effectively shared by both wireless communication systems.
[Brief description of the drawings]
FIG. 1 is a schematic diagram showing a wireless communication system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing a channel selection processing unit of a base station.
FIG. 3 is a flowchart showing a basic processing procedure for channel selection;
FIG. 4 is a flowchart showing a procedure for investigating the channel usage status of the own wireless communication system.
FIG. 5 is a flowchart showing another channel selection processing procedure.
FIG. 6 is a flowchart showing another channel selection processing procedure.
FIG. 7 is a flowchart showing another channel selection processing procedure.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10A ... Own wireless communication system, 1-3 ... Base station, 4-7 ... Mobile station, 8 ... Wired network, 10B ... Other wireless communication systems, 11 ... Base station, 12 ... Mobile station, 21 ... Control packet transmission / reception part, 22 ... Received power measurement unit, 23 ... Channel selection control unit, 24 ... Channel selection information registration unit.

Claims (7)

Each Ri Do from a plurality of radio stations, in a state where the local radio communication system and other wireless communication systems using different communication schemes from each other are mixed, the plurality of selection target channel including a channel which is also used by other radio communication systems From the wireless communication system for selecting a channel to be used at the time of wireless communication in the own wireless communication system, the usage status of each selection target channel by the own wireless communication system is investigated by sending and receiving control packets, A channel selection method characterized by investigating the usage status of a selection target channel by interference wave power, and selecting a channel to be used at the time of wireless communication in the own radio communication system from the selection target channel based on these investigation results, A shared channel shared by both wireless communication systems is registered in advance as shared channel information. In addition, a channel that is a selection target channel that is not used in the local radio communication system that is confirmed based on the channel usage status of the selection target channel by the local radio communication system and that is not registered as a shared channel is extracted and extracted. A channel selection method characterized by selecting a channel having the smallest interference wave power from the selected channels. The channel selection method according to claim 1, wherein
If all of the channels to be selected that are not used in the own radio communication system are shared channels, these channels are not used in the own radio communication system and the interference wave power is lower than the preset common reference level. A channel selection method, comprising: extracting a channel and selecting a channel to be used during wireless communication in the own wireless communication system from the extracted channels. The channel selection method according to claim 2, wherein
Set a predetermined limit reference level higher than the shared reference level in advance,
When there is no channel whose interference wave power is lower than the common reference level among the selection target channels that are not used in the own radio communication system,
Extraction of channels that are unused in the local wireless communication system and whose interference wave power is lower than the limit reference level,
A channel selection method characterized by selecting a channel to be used at the time of wireless communication in the own wireless communication system from among the extracted channels, and setting a limited transmission power lower than normal as a transmission power in the channel. The channel selection method according to claim 2 or 3,
A channel selection method comprising: selecting a channel having the smallest interference wave power from among the extracted channels as a channel to be used during wireless communication in the own wireless communication system. The channel selection method according to claim 2 or 3,
A channel selection method using a value set individually for each channel to be selected as a common reference level. The channel selection method according to claim 3,
A channel selection method using a value set individually for each selection target channel as a restriction reference level. The channel selection method according to claim 3,
A channel selection method using a value set individually for each selection target channel as the limited transmission power.

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