JP2009225053A - Radio communication system, and base station and radio device used therein - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a radio communication system capable of suppressing a deterioration in end-to-end communication quality. <P>SOLUTION: The base stations 10 and 20 respectively measure congestion degrees C1 and C2 in themselves, incorporate the measured congestion degrees C1 and C2 into beacon frames BCF1 and BCF2 and transmit them to a radio device 30. The radio device 30 detects reception signal strengths RSSI1 and RSSI2 when receiving the beacon frames BCF1 and BCF2. Then, on the basis of the congestion degrees C1 and C2 and the reception signal strengths RSSI1 and RSSI2, the radio device 30 selects the base station whose reception signal strength is equal to or higher than a threshold RSSI_th and congestion degree is equal to or lower than a threshold C_th from among the base stations 10 and 20 as the base station of a connecting destination. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a radio communication system, a base station used for the radio communication system, and a radio apparatus.

  Conventionally, a procedure when a station connects to an access point is as follows.

  The station collects the Beacon frame transmitted by each access point (passive scan), collects the probe response frame from each access point for the probe request frame transmitted by itself (active scan), and collects all channels. Scan all base stations present above.

  Then, the station generates a scan report as a scan result. The scan report includes all base stations discovered by scanning and their parameters.

  The parameters include information such as BSSID, SSID, BSType, beacon interval, DTIM interval, timing parameter, PHY parameter, CF parameter, IBSS parameter, BSS basic rate set, and signal strength from the access point.

When the station generates a scan report, the station determines which base station to participate in based on the signal strength from the access point (Non-Patent Document 1).
Matthew Gast, "802.11 Wireless Network Management", O'Reilly Japan, ISBN4-87311-308-3.

  However, in the prior art, the signal strength from the access point is used as the access point selection criterion, but even if the signal strength from the connected access point is high, the processing load on the access point is high or the access point uses it. There is a problem in that end-to-end communication quality is deteriorated when a wireless channel is congested.

  Accordingly, the present invention has been made to solve such a problem, and an object of the present invention is to provide a wireless communication system capable of suppressing a decrease in end-to-end communication quality.

  Another object of the present invention is to provide a base station used in a radio communication system capable of suppressing a decrease in end-to-end communication quality.

  Furthermore, another object of the present invention is to provide a radio apparatus used in a radio communication system capable of suppressing a decrease in end-to-end communication quality.

  According to the present invention, a wireless communication system includes a plurality of base stations and a wireless device. Each of the plurality of base stations measures the degree of congestion at the base station, and transmits a control frame including the measured degree of congestion. The wireless device receives a plurality of control frames transmitted from a plurality of base stations, and based on a plurality of received signal strengths when a plurality of control frames are received and a plurality of congestion levels included in the plurality of control frames. Then, a base station whose received signal strength is equal to or higher than the first threshold value and whose congestion level is equal to or lower than the second threshold value is selected as a connection destination base station.

  Preferably, the wireless device has a minimum congestion level when there are a plurality of base stations whose received signal strength is equal to or higher than the first threshold value and whose congestion level is equal to or lower than the second threshold value. Select the base station as the connection destination base station.

  Preferably, each of the plurality of base stations includes a channel congestion degree of a channel used by the base station, the number of wireless devices connected to the base station, the number of sessions passing through the base station, and arithmetic processing in the base station One of the usage rate of the apparatus, the amount of input traffic input to the base station, and the amount of output traffic output from the base station is measured as the degree of congestion.

  Further, according to the present invention, the base station is a base station that transmits selection information for selecting a base station to a radio apparatus under its control, and includes a measurement unit and a transmission unit. The measuring means measures the degree of congestion at the base station. The transmission means creates a control frame including the degree of congestion measured by the measurement means, and transmits the created control frame to the subordinate radio apparatus.

  Preferably, the measurement unit is configured such that the channel congestion level of the channel used by the base station, the number of wireless devices already connected to the base station, the number of sessions passing through the base station, and the usage rate of arithmetic processing units in the base station Then, either the amount of input traffic input to the base station or the amount of output traffic output from the base station is measured as the degree of congestion.

  Preferably, the transmission unit creates a control frame and transmits the control frame to the subordinate radio apparatus in response to a request from the subordinate radio apparatus.

  Further, according to the present invention, the wireless device is a wireless device that selects a connection destination base station from a plurality of base stations, and includes a reception unit, a detection unit, and a selection unit. The receiving means receives a control frame including the degree of congestion in the base station from a plurality of base stations. The detecting means detects a plurality of received signal strengths when the receiving means receives a plurality of control frames from a plurality of base stations. The selection means has a received signal strength that is greater than or equal to a first threshold and a congestion level that is a second threshold based on a plurality of received signal strengths and a plurality of congestion levels included in a plurality of control frames. A base station that is less than or equal to the value is selected as a connection destination base station.

  Preferably, the wireless device further includes a creation unit. The creation means includes a selection table comprising a plurality of identifiers for identifying a plurality of base stations, a plurality of received signal strengths associated with the plurality of identifiers, and a plurality of congestion levels associated with the plurality of identifiers. Create The detecting means detects the received signal strength when the receiving means receives a control frame from one base station. The selecting means extracts the identifier and congestion level of one base station from the control frame received by the receiving means from one base station, and the reception detected by the identifier and congestion degree of the extracted base station and the detecting means. Corresponding signal strength is stored in the selection table.

  Preferably, the selection means has a minimum congestion level when there are a plurality of base stations whose received signal strength is equal to or higher than the first threshold value and whose congestion level is equal to or lower than the second threshold value. Select the base station as the connection destination base station.

  Preferably, the receiving unit receives the control frame as a response corresponding to the request from the wireless device.

  In the present invention, a base station whose received signal strength is equal to or higher than the first threshold and whose congestion level is equal to or lower than the second threshold is selected as a connection destination base station. As a result, the wireless device can stably perform wireless communication with the connected base station.

  Therefore, according to the present invention, it is possible to suppress a decrease in end-to-end communication quality.

  Embodiments of the present invention will be described in detail with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals and description thereof will not be repeated.

  FIG. 1 is a schematic diagram showing a configuration of a wireless communication system according to an embodiment of the present invention. A wireless communication system 100 according to an embodiment of the present invention includes base stations 10 and 20 and a wireless device 30.

  Each of the base stations 10 and 20 includes an access point. Each of the base stations 10 and 20 measures the degree of congestion in itself by a method described later, and transmits the measured degree of congestion in the Beacon frame to the radio apparatus 30.

  The radio device 30 receives the Beacon frame transmitted from the base stations 10 and 20, and based on the received signal strength when the Beacon frame is received and the degree of congestion included in the Beacon frame, by a method described later Then, the base station to be connected is selected from the base stations 10 and 20. Then, the wireless device 30 connects to the selected base station.

  FIG. 2 is a schematic diagram showing the configuration of the base station 10 shown in FIG. The base station 10 includes a wireless module 1, a monitor module 2, a queue 3, and a communication module 4.

  The wireless module 1 has a built-in timer. The wireless module 1 extracts the packet from the queue 3, transmits the extracted packet to the wireless device 30, receives the packet from the wireless device 30, and outputs the received packet to the communication module 4.

  The wireless module 1 measures the time when the packet transmission is completed and outputs the measured time to the monitor module 2.

  The monitor module 2 receives a time T1 when the communication module 2 stores the packet in the queue 3 from the communication module 4, and receives a time T2 when the wireless module 1 completes transmission of the packet from the wireless module 1. Then, the monitor module 2 calculates the transmission time Ttx in the base station 10 by subtracting the time T1 from the time T2, and outputs the calculated transmission time Ttx to the communication module 4 as the congestion degree in the base station 10.

  The queue 3 holds the packet received from the communication module 4 for a certain time. The communication module 4 has a built-in timer. The communication module 4 stores the packet received from the upper layer in the queue 3 and measures the time T1 when the packet is stored in the queue 3 and outputs it to the monitor module 2.

  The communication module 4 receives a packet from the wireless module 1. Further, when the communication module 4 receives the congestion level (= transmission time Ttx) from the monitor module 2, the communication module 4 stores the received congestion level (= transmission time Ttx) in the Beacon frame, via the queue 3 and the wireless module 1. Transmit to the wireless device 30.

  The base station 20 shown in FIG. 1 has the same configuration as the base station 10 shown in FIG.

  FIG. 3 is a schematic diagram showing the configuration of the wireless device 30 shown in FIG. The wireless device 30 includes a transmission / reception module 31, a detection unit 32, a creation unit 33, a selection table 34, a selection unit 35, and a communication module 36.

  The transmission / reception module 31 receives the Beacon frame transmitted from the base stations 10 and 20 and outputs the received Beacon frame to the creation unit 33. In addition, the transmission / reception module 31 receives packets transmitted from the base stations 10 and 20 and outputs the received packets to the communication module 36.

  Further, the transmission / reception module 31 transmits the packet received from the communication module 36 to the base stations 10 and 20.

  The detecting unit 32 detects the received signal strength RSSI when the transmission / reception module 31 receives the Beacon frame, and outputs the detected received signal strength RSSI to the creating unit 33.

  The creation unit 33 receives the Beacon frame from the transmission / reception module 31 and the reception signal strength RSSI from the detection unit 32. Then, the creation unit 33 creates the selection table 34 by a method described later based on the Beacon frame and the received signal strength.

  The selection table 34 includes a table in which the identifiers of the base stations 10 and 20, the received signal strength when receiving packets from the base stations 10 and 20, and the congestion level in the base stations 10 and 20 are associated with each other.

  The selection means 35 refers to the selection table 34 and selects a connection destination base station to which the radio apparatus 30 is connected from the base stations 10 and 20 by a method described later. Then, the selection unit 35 notifies the communication module 36 of the selected base station.

  The communication module 36 receives a packet from the transmission / reception module 31. In addition, when the communication module 36 receives the base station to which the wireless device 30 is connected from the selection unit 35, the communication module 36 accesses the connection destination base station to establish a wireless link. Then, the communication module 36 performs wireless communication with the connection destination base station.

  FIG. 4 is a configuration diagram of a Beacon frame as a MAC management frame. The Beacon frame includes a MAC header, a frame body, and a frame checksum sequence (FCS).

  The MAC header is constant regardless of the frame subtype. The MAC header includes BSSID. The frame body is composed of an information element (IE) and a fixed field.

  The information element is used for exchanging information between nodes and has a variable length.

  FIG. 5 is a configuration diagram of the information element shown in FIG. The information element includes an element ID, a length, and measurement information. In the present invention, for example, “224” is stored as an element ID that is not generally used in the present invention. The length indicates the length of the information element. The measurement information stores the degree of congestion and the SSID.

  When the communication module 4 of the base stations 10 and 20 receives the congestion level from the monitor module 2, the communication module 4 stores the received congestion level in the measurement information of the information element of the Beacon frame, and the Beacon frame storing the congestion level is stored in the wireless device. 30.

  FIG. 6 is a configuration diagram of the selection table 34 shown in FIG. The selection table 34 includes BSSID, SSID, received signal strength, and congestion level. The SSID, SSID, received signal strength, and congestion level are associated with each other.

  The BSSID is an identifier of the base stations 10 and 20 and includes the MAC addresses of the base stations 10 and 20. The SSID is an ID of a base station (access focus) that performs the same operation, and is set by the user.

  The received signal strength consists of the received signal strength when a Beacon frame is received. The degree of congestion consists of the degree of congestion in the base stations 10 and 20.

  When receiving the Beacon frame from the transmission / reception module 31, the creating unit 33 of the wireless device 30 extracts the BSSID, the SSID, and the degree of congestion from the received Beacon frame. The creation unit 33 receives the received signal strength from the detection unit 32 when the Beacon frame is received. Then, the creation unit 33 stores the BSSID, SSID, received signal strength, and congestion level in the selection table 34 in association with each other.

  FIG. 7 is a diagram showing a specific example of the selection table 34. The creation means 33 creates the selection table 34A based on the Beacon frame received from the base stations 10 and 20. In the selection table 34A, the same SSID is assigned to the base stations 10 and 20.

  The selection means 35 refers to the selection table 34 </ b> A and selects the base station to which the wireless device 30 is connected from the base stations 10 and 20. More specifically, the selection means 35 extracts the received signal strengths RSSI1, RRSI2 and the congestion levels C1, C2 from the selection table 34A, compares the extracted received signal strengths RSSI1, RRSI2 with the threshold value RSSI_th, and the congestion level. C1 and C2 are compared with a threshold value C_th.

  Then, the selection unit 35 selects a base station whose received signal strength RSSI is equal to or higher than the threshold RSSI_th and whose congestion degree C is equal to or lower than the threshold C_th as a base station to which the radio apparatus 30 is connected.

  Note that when there are a plurality of base stations whose received signal strength RSSI is equal to or greater than the threshold RSSI_th and the congestion degree C is equal to or less than the threshold C_th, the selection unit 35 selects the base having the minimum congestion degree C. The station is selected as a base station to which the wireless device 30 is connected.

  Thus, in the present invention, a base station whose received signal strength RSSI is equal to or greater than the threshold RSSI_th and whose congestion degree C is equal to or less than the threshold C_th is selected as a base station to which the radio apparatus 30 is connected. Therefore, the wireless device 30 can perform wireless communication while suppressing a decrease in end-to-end communication quality.

  FIG. 8 is a flowchart for explaining an operation of selecting a base station. When a series of operations is started, the base station 10 measures the congestion degree C1 by the above-described method, and the base station 20 measures the congestion degree C2 by the above-described method (step S1).

  Then, the base station 10 creates a Beacon frame BCF1 including the congestion degree C1, transmits the created Beacon frame BCF1 to the wireless device 30, and the base station 20 creates a Beacon frame BCF2 including the congestion degree C2. The created Beacon frame BCF2 is transmitted to the wireless device 30 (step S2).

  The transmission / reception module 31 of the radio apparatus 30 receives the Beacon frames BCF1 and BCF2 from the base stations 10 and 20 respectively (step S3), and outputs the received Beacon frames BCF1 and BCF2 to the creation unit 33.

  The detection unit 32 of the wireless device 30 detects the received signal strength RSSI1 when the transmission / reception module 31 receives the Beacon frame BCF1, and detects the reception signal strength RSSI2 when the transmission / reception module 31 receives the Beacon frame BCF2. (Step S4).

  Thereafter, the detection means 32 of the wireless device 30 outputs the detected received signal strengths RSSI1 and RSSI2 to the creation means 33.

  The creation means 33 of the wireless device 30 receives the Beacon frames BCF1 and BCF2 from the transmission / reception module 31, and receives the received signal strengths RSSI1 and RSS2 from the detection means 32. Then, the creation unit 33 of the wireless device 30 extracts the BSSID (= MACadd10), SSID (= SSID_A), and the congestion degree C1 from the Beacon frame BCF1, and extracts the BSSID (= MACadd10), SSID (= SSID_A) and the congestion degree. C1 and received signal strength RSSI1 are stored in the selection table 34 in association with each other.

  Also, the creation unit 33 of the wireless device 30 extracts the BSSID (= MACadd20), SSID (= SSID_A), and congestion degree C2 from the Beacon frame BCF2, and extracts the extracted BSSID (= MACadd20), SSID (= SSID_A) and congestion degree. C2 and received signal strength RSSI2 are stored in the selection table 34 in association with each other. Thereby, the selection table 34A is created (step S5).

  Then, the selection unit 35 of the wireless device 30 extracts the congestion levels C1 and C2 and the received signal strengths RSSI1 and TSSI2 from the selection table 34A, and receives them based on the extracted congestion levels C1 and C2 and the received signal strengths RSSI1 and TSSI2. Base stations whose signal strength RSSI is equal to or greater than the threshold RSSI_th and whose congestion degree C is equal to or less than the threshold C_th are extracted (step S6).

  And the selection means 35 of the radio | wireless apparatus 30 determines whether the extracted base station is plurality (step S7).

  When it is determined in step S7 that there are a plurality of extracted base stations, the selection unit 35 of the wireless device 30 selects the base station with the smallest congestion level as the connection destination base station (step S8).

  On the other hand, when it is determined in step S7 that there are not a plurality of extracted base stations, the selection unit 35 of the wireless device 30 selects the base station extracted in step S6 as a connection destination base station (step S9).

  And a series of operation | movement is complete | finished after step S8 or step S9.

  When the connection destination base station is selected, the wireless device 30 accesses the selected base station, establishes a wireless link, and performs wireless communication.

  In the above description, the base stations 10 and 20 have described that the measured congestion levels C1 and C2 are stored in the Beacon frames BCF1 and BCF2, respectively, and transmitted to the radio apparatus 30, but the present invention is not limited thereto. Instead, the base stations 10 and 20 may store the congestion levels C <b> 1 and C <b> 2 in the Probe Response frame transmitted in response to the Probe Request frame received from the wireless device 30 and transmit the congestion degree C <b> 1 and C <b> 2 to the wireless device 30.

  The Probe Response frame has the same configuration as the Beacon frame shown in FIGS. Therefore, the communication module 4 of the base stations 10 and 20 stores the congestion degrees C1 and C2 in the measurement information of the information element of the Probe Response frame and transmits it to the radio apparatus 30.

  As described above, in the present invention, the radio apparatus 30 transmits a Probe Request frame to the base stations 10 and 20, and transmits a Probe Response frame including the congestion degrees C1 and C2 in the base stations 10 and 20 from the base stations 10 and 20, respectively. Information for selecting a connection destination base station may be collected by reception. That is, the wireless device 30 transmits a request (= Probe Request frame) to the base stations 10 and 20, and receives a Probe Response frame that is a response corresponding to the request to select a connection destination base station. Information may be collected.

  In the above description, the degree of congestion has been described as being the time from when the packet is stored in the queue 3 until the packet transmission is completed in the base stations 10 and 20, but the present invention is not limited to this. The congestion level may consist of the following information.

  That is, the congestion level is the channel congestion level of the channels at the base stations 10 and 20, the number of wireless devices connected to the base stations 10 and 20, the number of sessions passing through the base stations 10 and 20, and the computation at the base stations 10 and 20. It may consist of any one of a usage rate of a processing device (CPU: Central Processing Unit), an input traffic amount input to the base stations 10 and 20, and an output traffic amount output from the base stations 10 and 20.

  When the congestion level is composed of the channel congestion level, the congestion level is measured by the monitor module 2 as the time from when the packet is stored in the queue 3 to when the packet is taken out from the queue 3.

  When the congestion level is composed of the number of connected wireless devices, the congestion level is measured by the communication module 4 as the number of wireless devices with which the communication module 4 is performing wireless communication.

  Further, when the congestion degree is composed of the number of sessions passing through the base stations 10 and 20, the congestion degree is measured by the application as the number of sessions established by the application existing in the upper layer. Then, the communication module 4 receives the number of sessions from the application.

  Furthermore, when the degree of congestion is composed of the usage rate of the arithmetic processing unit (CPU), the degree of congestion is measured by the arithmetic processing unit (CPU) as the processing amount of the arithmetic processing unit (CPU) within a certain time. The communication module 4 receives the usage rate from the arithmetic processing unit (CPU).

  Further, when the congestion degree is composed of the input traffic amount, the congestion degree is measured by the communication module 4 as the bit amount input to the communication module 4 within a predetermined time.

  Furthermore, when the congestion level is composed of the output traffic volume, the congestion level is measured by the communication module 4 as the bit volume output from the communication module 4 within a certain time.

  Further, in the above description, the radio communication system 100 includes the two base stations 10 and 20, but in the present invention, the radio communication system 100 is not limited to this, and the radio communication system 100 includes three or more base stations. In general, a plurality of base stations may be provided. The same applies to the wireless device.

  In the present invention, the threshold value RSSI_th constitutes a “first threshold value”, and the threshold value C_th constitutes a “second threshold value”.

  In the present invention, the Beacon frame and the Probe Response frame constitute a “control frame”.

  Further, in the present invention, the monitor module 2 constitutes “measuring means”, and the communication module 4 constitutes “transmission means”.

  Furthermore, in the present invention, the transmission / reception module 31 constitutes “reception means”.

  The embodiment disclosed this time should be considered as illustrative in all points and not restrictive. The scope of the present invention is shown not by the above description of the embodiments but by the scope of claims for patent, and is intended to include meanings equivalent to the scope of claims for patent and all modifications within the scope.

  The present invention is applied to a wireless communication system capable of suppressing a decrease in end-to-end communication quality. The present invention is also applied to a base station used in a wireless communication system capable of suppressing a decrease in end-to-end communication quality. Furthermore, the present invention is applied to a radio apparatus used in a radio communication system capable of suppressing a decrease in end-to-end communication quality.

It is the schematic which shows the structure of the radio | wireless communications system by embodiment of this invention. It is the schematic which shows the structure of the base station shown in FIG. It is the schematic which shows the structure of the radio | wireless apparatus shown in FIG. It is a block diagram of the Beacon frame as a MAC management frame. It is a block diagram of the information element shown in FIG. It is a block diagram of the selection table shown in FIG. It is a figure which shows the specific example of a selection table. It is a flowchart for demonstrating the operation | movement which selects a base station.

Explanation of symbols

  1 wireless module, 2 monitor module, 3 queue, 4,36 communication module, 10, 20 base station, 30 wireless device, 31 transmission / reception module, 32 detection means, 33 creation means, 34, 34A selection table, 35 selection means, 100 Wireless communication system.

Claims (10)

A plurality of base stations each measuring the degree of congestion in the base station and transmitting a control frame including the measured degree of congestion;
Receiving a plurality of control frames transmitted from the plurality of base stations, based on a plurality of received signal strengths when the plurality of control frames are received and a plurality of congestion levels included in the plurality of control frames, A radio communication system comprising: a radio apparatus that selects, as the connection destination base station, a base station whose received signal strength is equal to or higher than a first threshold and whose congestion level is equal to or lower than a second threshold .   In the wireless device, when there are a plurality of base stations in which the received signal strength is equal to or higher than the first threshold value and the congestion level is equal to or lower than the second threshold value, the congestion level is The wireless communication system according to claim 1, wherein a base station that is the smallest is selected as the connection-destination base station.   Each of the plurality of base stations includes a channel congestion degree of a channel used by the base station, the number of wireless devices connected to the base station, the number of sessions passing through the base station, and the number of processing units in the base station. The wireless communication system according to claim 1, wherein any one of a usage rate, an input traffic amount input to the base station, and an output traffic amount output from the base station is measured as the congestion level. A base station that transmits selection information for selecting a base station to a subordinate radio apparatus,
Measuring means for measuring the degree of congestion in the base station;
A base station comprising: a control frame that includes a control frame that includes the degree of congestion measured by the measurement module; and a transmission module that transmits the generated control frame to the subordinate radio apparatus.   The measurement means includes a channel congestion degree of a channel used by the base station, the number of radio devices already connected to the base station, the number of sessions passing through the base station, a usage rate of arithmetic processing units in the base station, The base station according to claim 4, wherein either the input traffic amount input to the base station or the output traffic amount output from the base station is measured as the congestion level.   The base station according to claim 4 or 5, wherein the transmission unit creates the control frame and transmits the control frame to the subordinate radio apparatus in response to a request from the subordinate radio apparatus. A wireless device for selecting a connection destination base station from a plurality of base stations,
Receiving means for receiving a control frame including a congestion degree in the base station from the plurality of base stations;
Detecting means for detecting a plurality of received signal strengths when the receiving means receives a plurality of control frames from the plurality of base stations;
Based on the plurality of received signal strengths and the plurality of congestion levels included in the plurality of control frames, the received signal strength is equal to or higher than a first threshold value, and the congestion level is a second threshold value. A radio apparatus comprising: a selecting unit that selects a base station that is equal to or less than a value as the connection destination base station. A selection table comprising a plurality of identifiers for identifying the plurality of base stations, a plurality of received signal strengths associated with the plurality of identifiers, and a plurality of congestion levels associated with the plurality of identifiers. It further comprises a creation means for creating,
The detecting means detects a received signal strength when the receiving means receives a control frame from one base station,
The selecting means extracts the identifier and congestion degree of the one base station from the control frame received by the receiving means from the one base station, and extracts the identifier and congestion degree of the one base station and the The radio apparatus according to claim 7, wherein the received signal strength detected by the detection unit is stored in the selection table in association with the received signal strength.   In the case where there are a plurality of base stations in which the received signal strength is equal to or higher than the first threshold value and the congestion level is equal to or lower than the second threshold value, the selection unit determines that the congestion level is The radio apparatus according to claim 8, wherein a base station that is the smallest is selected as the connection-destination base station.   The wireless device according to claim 7, wherein the reception unit receives the control frame as a response corresponding to a request from the wireless device.

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