JP2006279847A - Control station performing polling, and control method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a control station capable of preferably performing polling on the basis of a polling list having a priority for ranking an STA having higher priority at a higher position from among a plurality of CF-Pollable STAs associated with a non-competition period, and to provide a control method thereof. <P>SOLUTION: The control station performs polling using a polling list in executing communication with a plurality of subordinate stations. In this case, the priority of the subordinate stations is registered in the polling list controlled by the control station on the basis of a predetermined condition. Then, the control station performs polling for the subordinate stations in accordance with the priority during the non-competition period. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a control station that performs polling and a control method thereof.

  In the IEEE802.11 standard, a DCF (Distributed Coordination Function) system for transmitting data by a carrier sense multiple access / collision avoidance (CSMA / CA) system (a system for transmitting data by contention control) and an access point (AP) PCF (Point Coordination Function) that centrally manages communication traffic is standardized. In the PCF method, contention-free period (hereinafter referred to as “CFP”) and contention period (contention period, hereinafter referred to as “CP”) are alternately operated to transmit data of each station (STA). To control.

  In order to operate in the PCF method, the STA associates with the AP as a CF-Polatable STA, registers in the AP polling list, acquires the right to transmit data by polling control from the AP, and transmits data. Can do.

Non-CF-Pollable STAs that are not CF-Pollable STAs can only transmit data using the CSMA / CA method. If the PCF method is used, the CF-Pollable STA receives polling from the AP, and therefore communication can be performed with a higher priority than the NonCF-Pollable STA.
JP 2002-335266 A

  However, in the conventional example described above, the following problems have occurred.

  Since CF-Pollable STA can transmit data by AP polling, the priority of data transmission can be increased as compared with NonCF-Pollable STA, but priority between CF-Pollable STAs cannot be set. That is, CF-Pollable STAs are registered in the AP polling list, and STAs are polled fairly in the order registered in the polling list, so that the priority cannot be increased over other CF-Polable STAs. Therefore, even if a STA with high priority that frequently performs data transmission does not finish transmission during CFP, data transmission must be performed in competition with other STAs in the next CP.

  Also, the polling list registered in the AP is registered when the STA associates with the AP, and is deleted when the disassociation is performed. Therefore, the order of registration in the polling list changes at each association, and even the polling order may be later than the STA having a lower priority.

  The present invention has been made in view of such circumstances, and is based on a polling list provided with a priority order that places a higher priority STA among a plurality of CF-Pollable STAs associated in a contention-free period. It is an object of the present invention to provide a control station that can be suitably polled and a control method thereof.

In order to solve the above problems, the present invention is a control method of a control station that performs polling using a polling list for communication with a plurality of dependent stations,
A registration step of registering priorities of the plurality of dependent stations based on a predetermined condition in the polling list managed by the control station;
A polling step of polling the slave station from the control station according to the priority in a contention-free period.

In order to solve the above problem, the present invention provides a control method for a control station that performs polling using a polling list for communication with a plurality of dependent stations,
A polling step of polling a predetermined dependent station preferentially again in a remaining period within a contention-free period in which polling is performed based on the polling list is provided.

Furthermore, in order to solve the above-mentioned problem, the present invention is a control station that polls a dependent station using a polling list,
Registration means for registering priorities of the plurality of dependent stations in the polling list managed by the control station based on a predetermined condition;
Polling means for polling the dependent station from the control station according to the priority in a contention-free period.

Furthermore, in order to solve the above problem, the present invention provides a control station that polls a dependent station using a polling list,
Polling means for preferentially polling a predetermined dependent station again in a remaining period within a contention-free period in which polling is performed based on the polling list is provided.

  ADVANTAGE OF THE INVENTION According to this invention, it can poll suitably based on the polling list | wrist provided with the priority which ranks STA with high priority among several CF-Pollable STAs associated in a contention-free period.

  Hereinafter, polling in the wireless LAN system according to an embodiment of the present invention, a method for setting priority thereof, and the like will be described in detail with reference to the drawings.

<First Embodiment>
FIG. 1 is a block diagram showing a configuration of a wireless LAN system according to the first embodiment of the present invention. In FIG. 1, reference numeral 101 denotes a BSS (Basic Service Set) range indicating a wireless area of the access point (AP) 102. Reference numeral 102 denotes an AP that performs wireless communication with each wireless station (STA) and transmits and receives data. The AP 102 can perform PCF control by the PCF method.

  In FIG. 1, PC_1 (103), PC_2 (104), PC_A (105), and PC_B (106) are STAs that are going to join this BSS101.

  Here, PC_1 (103) indicates a state in which it is not associated with the AP. When PC_1 (103) enters the wireless area of the AP 102, it associates with the AP 102 and joins the BSS 101. This state is indicated by PC_1 (113). In this association, the CF-Pollable bit and the CF-PollRequest bit are turned ON so that the PCF operation is possible, the polling list stored in the memory in the AP 102 is CF-PollableSTA, and the polling target Register as a STA. In the polling list, STA-specific identifiers such as MAC (Media Access Control) addresses are registered.

  By associating with the CF-Pollable bit set to ON, it is possible to receive data transmission from the AP 102 during the CFP period. In addition, the CF-Poll Request bit is turned on and association is registered in the polling list of the AP 102, and the polling CF-Poll is received from the AP 102 during the CFP period, and data is transmitted from the PC_1 (113) to the AP 102. Make it possible. Similarly, other STAs can operate as CF-Polatable STAs by associating with the AP 102. This state is indicated by PC_2 (114), PC_A (115), and PC_B (116).

  Here, it is assumed that the PC_1 (113) is associated with the AP 102 for a long time, and once associated, maintains the association state for almost one day. That is, it is assumed that PC_1 (113) is a STA that performs wireless communication only with the AP. In this case, PC_1 (123) indicates a state in which the company is disassociated during the midnight and the power source of PC_1 is not started up at the midnight when the role of data transmission in the BSS 101 is completed. That is, the usage environment of PC_1 is almost in the area of the BSS 101 of the AP 102.

  Next, the PC_2 (114) associates with the AP 101 for a long time as with the PC_1 (113), but associates with the AP 102 only about half the time of the PC_1 (113), not about the PC_1 (113). Shall. However, in the case of association, the CF-Pollable bit and the CF-PollRequest bit are set to ON so that the PCF operation is possible. For example, this is a STA that associates almost every day in the morning, but disassociates with the AP 102 in the afternoon and enters the state of PC_2 (124).

  Next, PC_A (105) is an STA that associates with AP 102 for such a short time that it cannot be compared with PC_1 or PC_2. To enable PCF operation. For example, this is a case where PC_A is operated for about 1-2 days a week. After the operation, disassociation is performed and the state of PC_A (125) is obtained.

  Next, PC_B (106) is an STA with a shorter association time than PC_A (115). When the PC_B (106) associates similarly to the PC_A (115), the two bits of the CF-Pollable bit and the CF-PollRequest bit are turned ON to enable the PCF operation. For example, this is the case of an STA that happens to join the BSS 101, and after operation, it is disassociated and enters the PC_B (126) state.

  As described above, in the example illustrated in FIG. 1, the PC_ <b> 1, PC_ <b> 2, PC_A, and PC_B are in descending order of the time that the AP 102 has joined the BSS 101. FIG. 13 is a block diagram showing a detailed configuration of the AP and the STA configuring the wireless LAN system according to the embodiment of the present invention.

  In FIG. 13, 131 is an access point (for example, AP 102) that functions as a control station, and 132 is a station apparatus (STA) (for example, PC_1 (103)) that functions as a wireless station. As shown in the figure, the STA 132 includes an information processing unit 132a such as a personal computer and a station unit 132b connected thereto. The information processing unit 132a generates data to be transmitted by the station unit 132b and performs processing such as calculation using the data received by the station unit 132b.

  The station unit 132b includes a communication interface (communication I / F) unit 1321, a communication unit 1322, a control unit 1323, a memory unit 1324, and a bus 1325 for connecting them.

  The communication interface unit 1321 connects the information processing unit 132a and the station unit 132b. The communication unit 1322 transmits the input data by performing framing, error correction coding, modulation, etc. according to a predetermined wireless LAN protocol, or demodulates and decodes the received signal according to a predetermined wireless LAN protocol. Data is acquired by performing deframing or the like. For example, the communication unit 1322 uses the same frequency and modulation method as the AP 131 that is the communication partner. The control unit 1323 controls each component constituting the station unit 132b according to a program stored in the memory unit 1324 and operates in cooperation with each other. The memory unit 1324 includes a ROM that stores a program, a RAM that is used for temporary storage of data during program execution, and the like.

  On the other hand, the AP 131 controls a communication unit 1311 for wireless communication with the STA 132, a memory unit 1312 for storing communication data, a management unit 1313 that maintains a polling list and manages registration and the like. A control unit 1314 and a bus 1315 for performing communication between the units are provided.

  Conventionally, as a registration to the polling list, registration is performed in the higher order in the order of the association with the AP 102 regardless of the association time. The STAs at the top of this polling list are equal to the order of polling by the CFP under the PCF function. FIG. 2 is a diagram for explaining an example of a general polling list. As shown in FIG. 2, according to a general polling list, polling is performed in the order of STAs in higher rank, and after one round, polling is performed again from the higher rank. The polling operation in the CFP will be described with reference to FIG. In the following description, it is assumed that the association order is performed in the order of PC_A, PC_2, PC_1, and PC_B.

  FIG. 3 is a diagram for explaining the operation of a general CFP. First, the CFP 501 is a CFP under PCF operation, and continues to the CP 502 and further to the CFP 503. Since the association order is equal to the priority order of the polling list, the polling order in this case is PC_A, PC_2, PC_1, and PC_B. Therefore, when CFP is started, CF-Poll 504, which is polling for PC_A, is issued from the AP 102, and the PC_A (115) acquires the data transmission right in preference to other STAs, and transmits the data to the AP 102. Can do. In FIG. 3, data transmission to the AP 102 is not shown.

  Since the order of the next polling list is PC_2, CF-Poll 505 is issued and data transmission is performed in the same manner. The AP 102 issues a CF-Poll 506 to PC_1, which is the last polling of this CFP, in view of the preset CFP period. Next, PC_1 performs data transmission in the same manner, and the CFP ends. Here, since PC_1 (113) is a STA that always associates with the AP 102, the frequency of transmitting data to the AP 102 is often high. Therefore, data that could not be transmitted during the CFP period is transmitted to the AP 102 in competition with other STAs during the next CP 502, as indicated by DATA 507.

  Then, CFP 503 is started after CP 502. Here, since polling has been completed up to PC_1 (113) in the previous CFP 501, the next STA to be polled is PC_B (116). Since polling of the polling list has been completed, CF-Poll 509 is issued again to PC_A in the upper polling list.

  In the above process, CF-Poll in CFP is issued by repeating this operation, so that all CF-Pollable STAs are issued CF-Poll fairly. For this reason, superiority or inferiority between CF-Pollable STAs cannot be obtained.

  Then, next, the operation | movement which determines a priority in the case of registration to a polling list is demonstrated. The high priority STA determined here is not deleted from the polling list of the AP 102 even if it is disassociated, and an identifier is left for the next association. When a STA having a low priority is disassociated, the STA is deleted from the polling list. As a result, even when a low-priority STA associates earlier than a high-priority STA, a high-priority STA remains in the polling list, so a low-priority STA is higher than a high-priority STA. It will not be registered at the top.

  Next, an embodiment will be described in which when a STA having a high priority is CF-Polled, a large CFP period is set to allow sufficient time for data transmission. FIG. 4 is a flowchart for explaining an example of identifier remaining / deletion processing in the polling list according to the first embodiment of the present invention.

  First, each of the STAs PC_1 (103), PC_2 (104), PC_A (105), and PC_B (106) associates with the AP 102 in order to operate in the BSS 101 (step S801). At this time, the CF-Pollable bit and the CF-PollRequest bit are turned ON. As a result, the AP 102 can operate as a CF-Polatable STA even under the PCF function.

  The AP 102 keeps in the memory in the AP 102 which STA has associated with it in the past. Then, the AP 102 determines whether or not to leave the polling list depending on how many times the STA has associated. For example, when a STA that has associated 20 or more times in the past disassociates, it is set so as not to be deleted from the polling list. Therefore, the past number of each STA to be associated this time is integrated, and it is determined whether or not there is a specified number of times (here, for example, 20 times) or more (step S802).

  Here, if it is determined that the number of times is equal to or greater than the prescribed number (Yes), the association state is maintained until the STA requests disassociation (step S807), and if disassociation is requested (Yes), disassociation is performed. (Step S808), and the identifier of the disassociated STA remains in the polling list of the AP 102 (Step S809). As a result, when the association is performed next time, the association order remains in the polling list even later, so it is possible to receive the CF-Poll without changing the polling list.

  Here, when it remains in the polling list in step S809, it is assumed that it can be identified whether it is a polling target or not. For example, when registering in the polling list, a flag for identifying whether or not the STA to be registered is a polling target is set, or a list different from the polling list is prepared and the polling target is prepared. STA to be identified can be identified.

  On the other hand, if it is determined in step S802 that the number is less than the specified number (No), it is further determined whether or not the associated STA is a STA having a special priority (step S803). This requires such a criterion when the user of the STA is high. The reason is that even if the past number of associations is not large, the user is expected to handle important data and needs to raise the priority. This may be a method of storing the MAC address of the STA having the special priority in the AP 102 or a method of performing association with a special ID when the STA associates with the AP.

  As a result, if it is determined in step S803 that there is a priority connection right (Yes), the identifier remains in the polling list even if the STA disassociates as in the case where the above-described association is more than the specified number of times (step S807, S808, S809). On the other hand, if it is determined that there is no priority connection right (No), it is determined based on whether or not the association has been performed for a time longer than the specified time in the current association (step S804).

  As a result, if there is no association over the specified time (No), it is further determined whether or not the total number of times of data transmission / reception has been performed more than the specified number of times (or the length of data transmission time, etc.) for a short time (Step S806). Alternatively, the determination may be made based on whether the target STA has a special address or code. If it is determined that the specified number of times of data transmission / reception has not been performed (No), the association state is maintained until the STA requests disassociation (step S810), and the disassociation is requested (Yes). Then, a disassociation process is performed (step S811), and the identifier of the disassociated STA is deleted from the polling list (step S812).

  On the other hand, if the association has been made for the current specified time or more in step S804 (Yes), it is next determined how many times data has been transmitted / received in the current association (step S805). As a result, when data transmission / reception is performed more than the specified number of times (Yes), the process proceeds to step S807 described above.

  On the other hand, if the data transmission has not been performed more than the current specified number of times in step S805 (No), the process proceeds to step S810 described above. . In the present embodiment, STAs with high priorities are left in the polling list by such a method. Thus, in this embodiment, when determining the priority order of the polling list, the order of the polling list is determined according to the conditions described so far, regardless of the order of association.

  The conditions described here are merely examples, and it may be possible to leave the polling list at the top of various other conditions. However, the effect of the present invention is not changed. When all the STAs are disassociated after the end of these operations, PC_A and PC_B having a low priority are deleted from the polling list, and PC_1 and PC_2 having a high priority remain. FIG. 5 is a diagram showing a polling list after disassociation in the wireless LAN system according to the present embodiment.

  Next, an operation for determining the priority of the polling list and the length of the CFP period when performing CF-Poll according to the priority of the polling list determined in the above process will be described. Each STA associates with the AP 102 as a CF-Pollable STA by the above process. The priority order here is PC_1, PC_2, PC_A, and PC_B. This is determined from the association time and the like. FIG. 6 is a diagram showing a polling list before the start of an operation for determining the priority of the polling list and the length of the CFP period.

  Here, FIG. 7 is a diagram for explaining the CFP operation according to the first embodiment of the present invention. FIG. 11 is a flowchart for determining the length of the CFP according to the first embodiment of the present invention. The AP 102 starts the CFP 1301 under the PCF function (Step S111). In this case, since CF-Poll (1306) is polling from PC_1 (113) having the highest priority, CFP 1301 sets the CFP having the maximum length that can be taken in accordance with the standard (step S112). This is because the PC_2 (114) having the second highest priority after the PC_1 (113) is polled after the data transmission of the PC_1 (113) is completed. This is because it is determined that PC_2 (114) having a high priority needs to give sufficient time for data transmission.

  Then, after the CF-Poll (1307), which is polling to the PC_2 (114), and after the data transmission of the PC_2 (114) is completed, the CFP period ends. Therefore, the PC_A (115) of the next priority in the polling list The polling of will be sent to the next CFP. Since CFP and CP are operated alternately, CP 1302 operates after CFP 1301 (step S113).

  Next, the CFP 1303 is started (step S114). The PC_A (115) that could not be CF-Polled by the previous CFP 1301 is polled (1308). However, as shown in FIG. 6, since the priority of PC_A (115) is low, the period of CFP 1303 is set to the shortest (step S115). This is a factor that sets the shortest STA to be polled next is PC_B having the lowest priority.

  After polling of PC_A (115), polling of PC_B (116) is performed (1309). However, since the period of the CFP 1303 is set to the shortest, it is assumed that the data transmission of the PC_B (116) does not end within the period of the CFP 1303. Therefore, when the CP 1304 after the CFP 1303 operates (step S116), it competes with other STAs to secure the access right and perform data transmission (1310).

  Since the CP 1304 is in a contention period, there is a possibility that the access right cannot be secured. Therefore, it is desirable that PC_1 (113) and PC_2 (114) having higher priorities avoid contention in the CP as much as possible and terminate data transmission with priority in the CFP. Then, the next CFP 1305 is started (step S117), and the CFP 1305 again polls the PC_1 (113) and the PC_2 (114), so that the CFP 305 sets the maximum period that can be taken according to the standard (step S118). ). Accordingly, PC_1 (113) and PC_2 (114) can have a sufficient margin for data transmission.

  As described above, the polling order is not always divided into a high priority group and a low priority group. Therefore, a case where STAs with high priority and STAs with low priority are mixed during the CFP period will be described next.

  FIG. 8 is a diagram for explaining the operation of the CFP when STAs with high priority and STAs with low priority are mixed during the CFP period. First, polling is performed for PC_1 (113), which is the highest in the polling list (1406). For this reason, the CFP 1401 sets a maximum period. After the data transmission of the PC_1 (113) is completed, the PC_2 (114) is polled (1407).

  Here, since the period still remains in the CFP 401 after the data transmission of the PC_2, the PC_A (115) is polled (1408). In the next CFP 1403, polling is performed from PC_B (116) having a low priority (409). Therefore, the period of CFP 1403 is minimized. Although PC_1 (113) having the next highest priority is reserved, it is minimized to avoid taking much time for data transmission of PC_B (116) having the lower priority. Since the next polling of the CFP 1405 continues with PC_1 (113) and PC_2 (114), the CFP 1405 can secure a maximum period and give a sufficient margin for data transmission time.

  By this operation, a large CFP period is secured for STAs with high priority, and the CFP is reduced when STAs with low priority are polled. As a result, a STA with a high priority is given a CFP for a sufficiently long period, and a priority can be set between CF-Pollable STAs.

  As described above, the wireless LAN system according to this embodiment has the following effects. First, instead of registering the priorities to be registered in the polling list in order from the earliest associated person, various conditions can be prepared and priorities suitable for the conditions can be assigned. Also, during the CFP period, the length of the CFP period is set in consideration of the priority order of each STA registered in the polling list. As a result, by changing the time available for data transmission during the CFP period between the CF-Pollable STAs, it becomes possible to give priority to the CF-Pollable STAs. That is, it is possible to give enough time for data transmission to STAs with high priority and not much time to STAs with low priority.

<Second Embodiment>
FIG. 9 is a diagram showing a configuration of a wireless LAN system according to the second embodiment of the present invention. FIG. 10 is a sequence diagram for explaining the operation in the wireless LAN system according to the second embodiment of the present invention.

  In FIG. 9, reference numeral 1101 is connected to the Internet network 1107 by wire, and an access point (AP) that communicates with each STA by wireless is configured by an STA that is wirelessly connected to the AP 1101 within a range of radio waves of the AP 101. A basic service set (BSS) and 1103 are printers that can communicate with the AP 1101 in the BSS 1102 and are associated with the AP 1101 as a CF-Polatable STA in the second embodiment. However, since it is not registered in the polling list of the AP 1101, the AP 1101 does not transmit polling by CF-Poll.

  In FIG. 9, reference numeral 1104 denotes PC_A, which is a CF-Pollable STA associated with the AP 1101 as a CF-Pollable STA in the BSS. Further, reference numeral 1105 denotes PC_B which is a NonCF-Pollable STA associated with the AP 1101 in the BSS as a NonCF-Pollable STA. Note that PC_B (1105) is a personal computer having an IEEE 802.11 function in this embodiment.

  Normally, the system configuration as described above is used. During CP, PC_A (1104) and PC_B (1105) compete for wireless access and connect to the Internet network 1107 via the AP 1101 to transmit and receive data. Do. Also, when printing data from PC_A (1104) and PC_B (1105), the data is transmitted to the printer 1103 via the AP 1101 and printed. Data transmission to the printer 1103 can be performed in both CP (contention period) and CFP (no contention period) because the printer 1103 is a CF-Pollable STA. However, when printing data with high priority, CFP It is possible to print more efficiently if the data is transmitted with the.

  FIG. 9 further shows a case where a camera 1106 that is a mobile STA and has a wireless LAN function joins the BSS 1102. The camera before joining is indicated by a broken line. In this example, the camera 1106 associates with the AP 1101 as a CF-Polatable STA. The camera 1106 does not always subscribe to the BSS 1102, but associates with the AP 1101 only when the photographed photo data is printed on the printer 1103, joins the BSS 1102, and when printing of the photo data is completed, the AP 1101 And disassociate and leave BSS1102.

  Next, an operation in which the camera 1106 as the CF-Pollable STA transmits data in preference to other STAs (here, PC_A (1104) and PC_B (1105)) and prints photo data on the printer 1103 will be described with reference to FIG. It explains using.

  Before the camera 1106 joins the BSS 1102, the STAs of the PC_A (1104), the printer (1103), and the PC_B (1105) have completed association with the AP (1101).

  Since the PC_A (1104) is associated with the AP 1101 as a CF-Pollable STA, it is registered in the polling list of the AP 1101 and further becomes a CF-Pollable STA (1401, 1402). Here, it is assumed that PC_A (1104) is registered at the top of the polling list of the AP 1101.

  The printer 1103 associates only as a CF-PollableSTA, but does not register in the polling list of the AP 1101 (1403, 1404). This is because the possibility of transmitting data from the printer 1103 is very low, so even if polling is performed from the AP 1101, there is little opportunity to transmit data, and time is wasted, and other STAs miss the chance of data transmission. is there. However, since it is a CF-Pollable STA, it is possible to receive data from the AP 1101 when receiving data during the CFP period.

  Since PC_B (1105) is associated as NonCF-PolatableSTA, it cannot receive data from AP 1101 by receiving polling during CFP. Therefore, data cannot be transmitted / received unless the medium access right is ensured by competing with other STAs during the CP period. Here, the priority of the STA of PC_B (1105) is the lowest (1405, 1406).

  When the camera 1106 associates, the AP 1101 needs to recognize that the camera 1106 has a high priority. In this recognition method, a unique number such as a MAC address of the camera 1106 can be input and stored in the AP 1101 in advance. Furthermore, it can be realized by various methods such as setting a special bit when the camera 1106 associates with the AP 1101 or switching on the AP 1101 (1407, 1408). At this time, the camera 1106 is registered in the polling list of the AP 1101 with the next priority of PC_A (1104).

  Here, FIG. 12 is a flowchart for determining the length of the CFP according to the second embodiment of the present invention. A CFP start beacon (Beacon) is transmitted from the AP 1101 (1409). Thereby, CFP starts (step S121). This beacon includes duration information indicating the CFP period, and each STA can know how long the CFP is set. In this embodiment, since priority is further specified between CF-Pollable STAs and data transmission is to be performed, CFP is secured as long as possible. Therefore, when the camera 1106 having a higher priority is associated, it is necessary to set the maximum period during which the CFP can be taken according to the standard.

  Immediately after the beacon transmission, the AP 1101 polls the PC_A 1104 that is the highest STA registered in the polling list of the AP 1101 (1410). PC_A (1104) piggybacks the CF-Poll acknowledgment (ACK) as data to be transmitted to AP 1101, and transmits it as DATA + ACK (1411). When there is no data to be transmitted, it is not necessary to send back only ACK and transmit data.

  Next, the camera 1106 registered in the polling list of the AP 1101 is polled (1412). The camera 1106 piggybacks the photo data and an acknowledgment (ACK) to the AP 1101 and transmits it as DATA + ACK (1413). Here, in this example, the CFP is secured for the maximum period (step S122). Therefore, polling is further performed for the STA having a high priority in the remaining CFP (contention-free period), and CF-Poll is issued to pass the data transmission right (1414). Therefore, this system has a configuration in which such a period can be determined by the AP 1101. Here, the ACK of the data previously received by the AP 1101 is also transmitted at the same time. The AP 1101 issues CF-Poll until the photo data is completely transmitted. The camera 1106 continues to transmit photo data (1415-1417).

  The AP 1101 transmits the photo data received from the camera 1106 to the printer 1103 that is a CF-Pollable STA this time (1418). The printer 1103 and the AP 1101 repeatedly perform DATA and ACK (acknowledgment) until the transmission of the photo data is completed (1419). When this data transfer ends, the AP 1101 issues a CF-End and ends the CFP (step S123).

  Next, the AP 1101 starts CP (step S124). Here, since the camera 1106 has achieved the purpose of printing photo data, it disassociates and leaves the BSS 1102. Since PC_B (1105) could not transmit data at all by CFP, it competes with CP and completes data transmission with data (1422) and acknowledgment (1423) after RTS (1420) CTS (1421).

  As described above, the data of the camera 1106 is transmitted to the AP 1101 in preference to PC_A (1104) which is the same CF-Pollable STA and is higher in the polling list, and the data is further transmitted to the printer 1103. Become. As a result, the photo data of the camera 1106 is quickly printed by the printer 1103.

  As described above, according to the wireless LAN system according to the second embodiment, after polling each STA registered in the polling list once during the CFP period, the remaining CFP period is a high priority CF. -Priority polling for Polar STAs allows the priority order to be set between CF-Pollable STAs registered in the polling list, and the STA data is transmitted with priority over other STAs. Enable.

1 is a block diagram illustrating a configuration of a wireless LAN system according to a first embodiment of the present invention. It is a figure for demonstrating an example of a general polling list. It is a figure for demonstrating the operation | movement of general CFP. It is a flowchart for demonstrating an example of the residual / deletion process in the polling list which concerns on the 1st Embodiment of this invention. It is a figure which shows the polling list | wrist after the disassociation in the wireless LAN system which concerns on this embodiment. It is a figure which shows the polling list before the operation | movement start which determines the priority of a polling list, and the length of the period of CFP. It is a figure for demonstrating the CFP operation | movement which concerns on the 1st Embodiment of this invention. It is a figure for demonstrating the operation | movement of CFP when STA with high priority and STA with low priority coexist in a CFP period. It is a figure which shows the structure of the wireless LAN system which concerns on the 2nd Embodiment of this invention. It is a sequence diagram for demonstrating operation | movement in the wireless LAN system which concerns on the 2nd Embodiment of this invention. It is a flowchart for determining the length of CFP which concerns on the 1st Embodiment of this invention. It is a flowchart for determining the length of CFP which concerns on the 2nd Embodiment of this invention. It is a block diagram which shows the detailed structure of AP and STA which comprise the wireless LAN system which concerns on one Embodiment of this invention.

Explanation of symbols

101, 1102 Basic Service Set (BSS)
102, 1101 access point (AP)
103, 113, 123 PC_1
104, 114, 124 PC_2
105, 115, 125, 1104 PC_A
106, 116, 126, 1105 PC_B
1103 Printer 1106 Camera

Claims (19)

A control method for a control station that performs polling using a polling list for communication with a plurality of subordinate stations,
A registration step of registering priorities of the plurality of dependent stations based on a predetermined condition in the polling list managed by the control station;
And a polling step of polling the dependent station from the control station according to the priority in a contention-free period.   2. The control method according to claim 1, further comprising a deletion step of deleting, from the polling list, a dependent station that is out of the control of the control station according to the priority order of the dependent station.   3. The control method according to claim 2, wherein the deletion step does not delete a dependent station having a higher priority even if the dependent station is out of the control of the control station.   4. The polling process according to claim 1, wherein polling is performed by changing a length of a contention-free period in accordance with a priority order of a dependent station registered in the polling list. 5. Control method.   5. The contention-free period in which polling is started from a station having a higher priority of a dependent station registered in the polling list is set as a maximum period that can be taken by the contention-free period. Control method.   5. The contention-free period in which polling starts from a station having a lower priority of the dependent station registered in the polling list is set as a minimum period that can be taken by the contention-free period. Control method.   7. The registration process according to claim 1, wherein the registration step registers the plurality of dependent stations in the polling list in a priority order based on a time when each of the dependent stations is connected to the control station. The control method according to claim 1.   7. The registration process according to claim 1, wherein each of the dependent stations registers the plurality of dependent stations in the polling list in a priority order based on a data transmission time with the control station. 2. The control method according to item 1.   7. The registration process according to claim 1, wherein the registration step registers the plurality of dependent stations in the polling list in a priority order based on a predetermined code possessed by each of the dependent stations. The control method described in 1. A control method for a control station that performs polling using a polling list for communication with a plurality of subordinate stations,
A control method comprising a polling step of preferentially polling a predetermined dependent station again in a remaining period within a contention-free period in which polling is performed based on the polling list.   The control method according to claim 10, further comprising a determination step of determining the contention-free period.   The control method according to claim 10, further comprising a registration step of registering a subordinate station having a higher priority registered in the polling list in a higher rank in the polling list.   The control method according to claim 10, further comprising a registration step of registering a subordinate station having a lower priority registered in the polling list in an upper position in the polling list.   The control method according to claim 10, further comprising a registration step of registering a dependent station that is registered in the polling list at an upper level of the polling list.   The control method according to claim 10, further comprising a registration step of registering a subordinate station registered late in the polling list at a higher rank in the polling list.   11. The control according to claim 10, further comprising a registration step of registering a dependent station having a predetermined address among a plurality of dependent stations registered in the polling list in a higher rank of the polling list. Method.   The control according to claim 10, further comprising a registration step of registering a dependent station having a predetermined code among a plurality of dependent stations registered in the polling list at a higher rank of the polling list. Method. A control station that polls a dependent station using a polling list,
Registration means for registering priorities of the plurality of dependent stations in the polling list managed by the control station based on a predetermined condition;
Polling means for polling the dependent station from the control station according to the priority in a contention-free period. A control station that polls a dependent station using a polling list,
A control station comprising polling means for preferentially polling a predetermined dependent station again during a remaining period within a contention-free period in which polling is performed based on the polling list.

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