JP5938831B2 - Wireless access point - Google Patents

Description

  The present invention relates to a wireless communication device, and more particularly to a wireless access point in wireless LAN communication.

  In an infrastructure type wireless LAN network, a wireless access point (hereinafter referred to as an access point) that operates as a parent device manages a wireless slave device (hereinafter referred to as a station).

  The access point periodically broadcasts information necessary for wireless communication called a beacon to the station. Through this beacon, the access point can notify that communication data for a predetermined station exists. When unicast data exists, a TIM (Traffic Indication Message) beacon is used. When broadcast and multicast data (hereinafter collectively referred to as broadcast data, etc.) exists, a DTIM (Delivery Traffic Indication Message) beacon is used. use.

  A DTIM beacon is included in a predetermined number of times in a normal beacon, and this frequency (interval) is referred to as a DTIM interval. For example, when the DTIM interval is 3, one DTIM beacon is transmitted at intervals of three normal beacons. When the access point receives broadcast data or the like addressed to the station, the access point does not transmit immediately but buffers the broadcast data or the like until the next DTIM beacon transmission timing. Thereafter, a DTIM beacon is transmitted, and subsequently, the broadcast data and the like are transmitted. The DTIM beacon is transmitted from the access point mainly for the purpose of managing the power saving state of the station.

  On the other hand, in order to reduce the power consumption of the station, the station periodically switches between a power saving state and a non-power saving state (operation state) as its operation mode. In the power saving state, the station cannot perform wireless communication, and can perform wireless communication only in the non-power saving state. By intermittently entering the non-power-saving state in this way, the station reduces its power consumption. The operation mode switching timing is determined by the Listen Interval and Receive DTIM parameters set in the station.

  Listen Interval means the timing of receiving a beacon from an access point. For example, when Listen Interval is 2, it sets itself to a non-power-saving state so as to receive two beacons from the access point. .

 Receive DTIM has True or False as a setting value. If True, it sets itself to a non-power-saving state so as to receive all DTIM beacons from the access point. On the other hand, in the case of False, it does not link with the DTIM beacon, and makes itself non-power-saving according to only the above-described Listen Interval.

  When the station receives a DTIM beacon from the access point when the station is in a non-power-saving state, the station also receives subsequent broadcast data and the like. In this way, data can be transmitted and received while reducing power consumption.

  Hereinafter, an operation in which the station receives communication data from the access point will be described. A station that operates by switching between a power saving state and a non-power saving state is referred to as a power saving station.

  FIG. 1 is an overall view of a wireless communication system. The stations 102 are connected to the access point 101 and can communicate with each other wirelessly. Further, the access point 101 is connected to the communication terminal 103 by wire. Therefore, in this figure, the station 102 can communicate with the communication terminal 103 via the access point 101.

  FIG. 2 shows a state of data communication from the access point 101 to the station 102. The beacon transmitted from the access point 101 to the station 102 is an arrow with numbers 1 to 11 in the figure. Among the beacons, thick arrows (beacons 3, 6, 9) are DTIM beacons. In this case, the DTIM interval is 3. Therefore, one DTIM beacon is included for every three beacons.

  On the other hand, since the Listen Interval is 2, the station 102 sets itself to a non-power saving state at intervals of two beacons. Since Receive DTIM is False, not all DTIM beacons are received, and the non-power-saving state is established only based on the Listen Interval.

  In the figure, communication data such as broadcast is generated at the timing of the beacon 4 (actually, data generation and beacon timing are independent). For example, it is communication data transmitted from the communication terminal 103 to the station 102.

  At this time, the access point 101 does not notify the station 102 of the existence of the data. The reason is that it is not the timing for transmitting the DTIM beacon.

  At the subsequent DTIM beacon transmission timing (beacon 6), an attempt is made to notify the presence of data to the station 102. At this timing, the station 102 cannot receive the DTIM beacon because it is in a power saving state. That is, it cannot recognize the existence of data for itself. Meanwhile, the access point 101 buffers data for the station 102 in itself.

  The station 102 can recognize the presence of data when the beacon 9 receives the DTIM beacon. At this time, for the first time, the station 102 can recognize the presence of data and receive data from the access point 101.

  As described above, the station 102 having the power saving function is not always in operation (not in the non-power saving state), and thus communication may not be started immediately at a necessary timing. For this reason, a certain amount of delay is unavoidable. For example, if the station is always in a non-power-saving state (operating state), data reception can be started when the DTIM beacon 6 is received. That is, if the beacon interval is 100 milliseconds, a delay of 300 milliseconds occurs.

  As means for reducing such a delay, a technique for dynamically changing the DTIM interval is known (Non-patent Document 1). For example, when communication data such as broadcast to the station 102 exists, the DTIM interval is shortened to promptly notify the station 102 of the fact.

Nikkei BP website <http://itpro.nikkeibp.co.jp/article/COLUMN/20060929/249406/>

  Although the technology disclosed in Non-Patent Document 1 is expected to contribute to a certain degree of delay reduction, Non-Patent Document 1 does not clearly describe the trigger (trigger) for changing the DTIM interval. For example, assuming that the simplest pattern, that is, the data for the station 102 actually exists as a trigger for changing the DTIM interval, the effect is limited.

  The present invention solves this problem. That is, an access point having a power-saving station as a wireless slave device connected to itself is provided, which can perform wireless communication with low delay while reducing power consumption of the power-saving station.

  The first aspect of the present invention is a beacon transmitting means for transmitting a beacon indicating that data communication to a wireless station exists to a wireless station at a predetermined time interval, and a change for changing the predetermined time interval. Means for instructing a change of a predetermined time interval by the changing means, and the instruction means connects the wireless station to itself for a predetermined time interval when the wireless station is connected to itself. The time interval (t2) is changed to a time interval (t2) shorter than the previous time interval (t1), and then the predetermined time interval is changed to a time interval (t3) longer than the time interval (t2) before the predetermined time elapses. It is a wireless access point that instructs to change to

  The second aspect of the present invention is a beacon transmitting means for transmitting a beacon indicating that data communication to a wireless station exists to the wireless station at a predetermined time interval, and a change for changing the predetermined time interval. And an instruction means for instructing a change of a predetermined time interval by the changing means, and the instruction means sends a response (ARP response) to an ARP request transmitted from a wireless station connected to the wireless means to the wireless After responding to the station, the predetermined time interval is changed to a time interval (t5) shorter than the time interval before the response (t4), and then the predetermined time interval is changed after the predetermined time has elapsed. The wireless access point instructs to change to a time interval (t6) longer than the time interval (t5).

  More preferably, the wireless access point further includes wireless station specifying means for specifying a wireless station whose MAC address is resolved by the ARP request, and the wireless station specifying means is based on the ARP request transmitted from an arbitrary communication terminal. A wireless station that needs to resolve the MAC address is specified, and an ARP request is transmitted only to the specified wireless station.

  A third form according to the present invention is a beacon transmitting means for transmitting a beacon indicating that data communication to a wireless station exists to the wireless station at a predetermined time interval, and a change for changing the predetermined time interval. Means for instructing a change of a predetermined time interval by the changing means, and the indicating means buffers the radio frame to the radio station connected to itself at a predetermined location and then for a predetermined time. The interval is changed to a time interval (t8) shorter than the time interval before the buffer (t7), and then the predetermined time interval is set to be greater than the time interval (t8) before the predetermined time elapses after the predetermined time has elapsed. It is a wireless access point that instructs to change to a long time interval (t9).

  A fourth form according to the present invention is a beacon transmitting means for transmitting a beacon indicating that data communication to a wireless station exists to the wireless station at a predetermined time interval, and a change for changing the predetermined time interval. And an instruction means for instructing a change of a predetermined time interval by the changing means. The instruction means sets a predetermined time interval when a TCP session is established for a wireless station connected to the instruction means. When the time interval (t11) is shorter than the time interval (t10) before the TCP session is established and then the TCP session is released, the time is longer than the time interval (t11) before the TCP session is released. It is a wireless access point that instructs to change to the interval (t12).

  According to a fifth aspect of the present invention, a notification means for transmitting a notification that data communication to a communication terminal exists to a communication terminal at a predetermined time interval, and a changing means for changing the predetermined time interval. And an instruction means for instructing a change of the predetermined time interval by the changing means. The instruction means, when the predetermined condition is satisfied, the predetermined time interval before the predetermined condition is satisfied. The time interval (t14) is changed to a time interval (t14) shorter than the time interval (t13), and then the predetermined time interval is changed to a time interval (t15) longer than the time interval (t14) before the predetermined time elapses. It is a communication device that gives an instruction to change.

  More preferably, the predetermined condition is that data communication is predicted to occur before data communication to the communication terminal occurs.

  The change of the predetermined time interval indicated by the above-mentioned instruction means not only means the change of the absolute time interval such as 100 milliseconds, but also the DTIM beacon frequency (see paragraph 0004) has been explained. In this way, the change of the number of units, including a predetermined absolute time interval as one unit, is also included.

  The access point according to the present invention changes the DTIM interval not only when communication data for the station is actually generated but also when generation of communication data can be predicted. Furthermore, for an ARP request from a station, this request is transferred only to the corresponding station. Thus, communication can be started quickly while reducing the power consumption of the station. As a result, both power consumption and communication performance can be achieved.

Embodiments according to the present invention will be described below with reference to the drawings. Although the mechanism for changing the interval of the DTIM beacon is described below, the same applies to the TIM beacon.
[Example 1]
[System overview]

An overall system diagram according to the present embodiment is the same as that of FIG. In this figure, the device according to the present invention is an access point 101.
[DTIM interval]

  The access point 101 according to the present embodiment dynamically changes the DTIM interval when a predetermined condition is satisfied. For example, the change is made as shown in FIG. Normally, the access point 101 operates with a DTIM interval of 3. However, when a predetermined condition is satisfied, the DTIM interval is changed to 1 and this state is continued for a predetermined time. Return to.

By shortening the DTIM interval in this way, it is possible to promptly notify the station 102 in the power saving state of the existence of broadcast data or the like, and as a result, it contributes to the rapid start of unicast communication. The present invention is based on conditions that trigger the change of the DTIM interval.
[DTIM pattern]

  FIG. 4 shows a DTIM beacon pattern according to the present embodiment. In this embodiment, the normal DTIM interval is 2.

  The point of this embodiment is that the DTIM interval is changed from 2 to 1 after the connection 401 from the station 102 to the access point 101 just before the DTIM beacon 1 is performed. This connection 401 means a connection in the physical layer and the data link layer, not a connection such as TCP, and specifically, is an association process between the access point 101 and the station 102.

  The reason why the DTIM interval is shortened immediately after the association (DTIM beacons 1 to 6) is that the station 102 is presumed to be connected because there is a specific reason for communication. These DTIM beacons 1 to 6 are forged and notified that data is generated even though there is no actual broadcast data or the like.

  Therefore, by shortening the DTIM interval for a predetermined time immediately after the association, the station 102 can be quickly brought into a non-power-saving state. Actually, the station 102 is kept in a non-power-saving state continuously for a predetermined time by shortening the DTIM interval and at the same time notifying the occurrence of the above-mentioned simulated data.

  As means for faking data generation, there is a means for setting a MoreData (more data) bit that is included in the frame control field and indicates whether or not there is subsequent transmission waiting data to True (with data).

  After the predetermined time has elapsed, the station 102 returns to the operation of repeating the power saving state and the non-power saving state at the Listen Interval interval by returning to the normal DTIM interval (cancelling the notification that simulated data generation).

As described above, in this embodiment, the DTIM beacon interval is shortened by determining the presence of the association between the station 102 and the access point 101 as a prelude to the start of communication.
[Example 2]

  FIG. 5 shows a DTIM beacon pattern according to the present embodiment. In the present embodiment, the normal DTIM interval is set to 3.

  Beacons 1, 4-13 are DTIM beacons. The ARP request (broadcast communication) is transmitted from the communication terminal 103 to the station 102. The communication terminal 103 tries to resolve the IP address of the station 102 by the ARP request 501, but the ARP request 501 does not reach the station 102 at this timing because the station 102 is in a non-power saving state. For this reason, the access point 102 once buffers the ARP request 501 in itself.

  The access point 102 changes the DTIM beacon interval and transmits it by using the ARP request 501 buffered as a trigger (after DTIM beacon 4). The station 102 that has received this shifts from the power saving state to the non-power saving state.

  Next, the access point 101 transmits the buffered ARP request to the station 102 (ARP request 502). At this timing, since the station 102 is in a non-power saving state, the ARP request 502 can be received.

  On the other hand, the station 102 transmits an ARP response 503 to the communication terminal 103 as a response to the received ARP request 502. This enables communication higher than the IP layer between the communication terminal 103 and the station 102.

  Although higher-layer communication has become possible, it is not possible at this point to specify when data transmission / reception actually starts. However, in order to reduce the delay with respect to actual data transmission / reception, it is necessary to continuously set the station 102 in a non-power saving state. For this reason, also in this embodiment, the station 102 is continuously put into a non-power-saving state using the DTIM beacon and the like as in the first embodiment. Specifically, DTIM beacons 7 to 13 are beacons in which data generation is simulated.

  As shown in the figure, in this embodiment, there are two predetermined times, and the access point 101 shortens the DTIM interval during these times.

  One is a stage where the ARP request 501 from the communication terminal 103 is buffered. The presence of an ARP request indicates that there is a very high possibility that communication at the IP layer or higher will be performed thereafter, so that the station 102 is always in a non-power-saving state.

  The other is a predetermined time after the ARP response 503 from the station 102 is returned to the communication terminal 103 that is the ARP request source. This is because, as in the former case, it is estimated that there is an extremely high possibility that communication after the IP layer will be started after this. As described above, also in this case, since it is not known when the actual data communication in the upper layer is performed, it is necessary to keep the station 102 continuously in a non-power-saving state using a DTIM beacon or the like.

  As described above, in the present embodiment, the DTIM beacon interval is shortened by determining the presence of the ARP request and the ARP response as a prelude to the start of communication.

  The ARP request 502 from the access point 101 is normally made by broadcast communication. Therefore, if this is transmitted as wireless communication as it is, there arises a problem that stations other than the station 102 that is the target of the ARP request 502 are put into a non-power-saving state.

  As one means for avoiding such a problem, the access point 101 acquires the IP address of the station in advance by means such as RARP (Reverse Address Resolution Protocol), and the IP address and MAC address of all the stations are obtained. Know the correspondence beforehand. As a result, the station 102 that is the target of the ARP request 502 can be specified, and the request can be transmitted only to this station. Therefore, the ARP request 501 can be transmitted without obstructing the power saving state of other stations. Response is possible. As a result, it is possible to contribute to power saving as a whole wireless system.

The means for acquiring the IP address of the station and specifying the station that is the target of the ARP request 502 (wireless station specifying means) is not limited to the above-described RARP as long as the same can be performed. Is available. That is, it is only necessary that the access point 101 can uniquely identify a station without transferring the ARP request 502 by broadcast.
[Example 3]

  FIG. 6 shows a DTIM beacon pattern according to the present embodiment. In the present embodiment, the normal DTIM interval is set to 3.

  Beacons 1, 4-8, and 11 are DTIM beacons. As can be seen from the figure, the feature of this embodiment is that the interval between DTIM beacons is shortened in the TCP session duration. This is because, while the TCP session continues, there is a possibility that TCP data is always transmitted and received, and it is desirable to keep the station 102 in a non-power-saving state during that period.

Of course, as in the above-described embodiment, although there is a case where a TCP session exists, actual data communication may not be accompanied. Therefore, it is necessary to keep the station 102 in a non-power-saving state using a DTIM beacon or the like. is there. Specifically, it is DTIM beacons 4-8.
[Other Examples]

  In the embodiments so far, the DTIM interval is always set to 1. However, it is not necessarily 1, and any interval is effective as long as it is shorter than the normal DTIM interval. It is also possible to change the DTIM interval according to the type of trigger that triggers the change of the DTIM interval. For example, in the case where the association between the station 102 and the access point 101 as shown in the first embodiment is estimated that the occurrence probability of data communication is lower than the duration of the TCP session, the DTIM interval is set to 1. It is also possible to use 2 instead.

  Further, when returning the shortened DTIM interval, it is not always necessary to return to the normal DTIM interval, and it is sufficient that the interval is longer than the shortened DTIM interval. For example, the normal DTIM interval is 3, which is changed to 1 and then returned to 2 instead of the original 3. Of course, it is possible to return to a longer one (for example, 4) than the normal DTIM interval.

  Also, instead of shortening the DTIM interval, the beacon notification interval itself can be shortened. That is, the same effect as halving the DTIM interval can be obtained by setting the beacon interval that is normally broadcast at 100 millisecond intervals to 50 milliseconds.

  Furthermore, it is also possible to change the DTIM interval by stepping into the application communication performed on the TCP session. For example, as shown in FIG. 7, in a predetermined storage area, information in which session information (application and port number) of each application, the importance of response, and the DTIM interval are associated with each other is stored as a set. If communication by session is occurring, the interval is changed to the corresponding DTIM interval. Of course, when the response importance is high, the DTIM interval is set short, and conversely when the importance is low, the DTIM interval is set long. As a result, the DTIM interval can be changed according to the response importance of communication actually performed by the application.

  FIG. 8 shows a functional block diagram of the access point 101 common to the embodiments described above. The DTIM beacon sending means 801 is means for sending a DTIM beacon.

  The DTIM interval changing means 802 is means for dynamically changing the interval (cycle) at which the DTIM beacon is transmitted, and its value is designated by the DTIM interval changing instruction means 803 described later.

  The DTIM interval change instructing unit 803 instructs the DTIM interval changing unit 802 to change the DTIM interval to a value corresponding to the situation described in the previous embodiments.

The fake data notification instruction means 804 indicates to the DTIM beacon transmission means 801 that the MoreData (more data) bit, which is included in the frame control field and indicates whether or not there is subsequent transmission waiting data, is set to True (with data). It is a means of indicating.
[Summary]

  The access point according to the present invention changes the DTIM interval not only when communication data for the station is actually generated but also when generation of communication data can be predicted. Furthermore, for an ARP request from a station, this request is transferred only to the corresponding station. Thus, communication can be started quickly while reducing the power consumption of the station. As a result, both power consumption and communication performance can be achieved.

Overall system diagram Data communication from access point to wireless station Dynamic change of DTIM interval DTIM pattern in Example 1 DTIM pattern in Example 2 DTIM pattern in Example 3 DTIM interval according to the session Functional block diagram of access point

801 DTIM beacon transmission means 802 DTIM interval change means 803 DTIM interval change instruction means

Claims (5)

Beacon transmitting means for transmitting a beacon indicating that data communication to the wireless station exists to the wireless station at a predetermined time interval;
Changing means for changing the predetermined time interval;
An instruction means for instructing a change of a predetermined time interval by the changing means,
The instruction means includes
After responding to the wireless station with an ARP request transmitted from the wireless station connected to the wireless station (ARP response) , regardless of the presence or absence of data communication, the occurrence of data is simulated and notified, and the predetermined Is changed to a time interval (t5) shorter than the time interval before the response (t4),
Thereafter, after a predetermined time has elapsed, the predetermined time interval is changed to a time interval (t6) longer than the time interval (t5) before the predetermined time elapses.
Wireless access point that gives instructions. The wireless access point further includes wireless station specifying means for specifying a wireless station whose MAC address is resolved by an ARP request.
The wireless station specifying means specifies a wireless station that needs to resolve a MAC address based on the ARP request transmitted from an arbitrary communication terminal, and transmits the ARP request only to the specified wireless station. Item 2. The wireless access point according to Item 1. Beacon transmitting means for transmitting a beacon indicating that data communication to the wireless station exists to the wireless station at a predetermined time interval;
Changing means for changing the predetermined time interval;
An instruction means for instructing a change of a predetermined time interval by the changing means,
The instruction means includes
When a TCP session is established for a wireless station connected to itself, regardless of the presence or absence of data communication, data generation is falsified and reported , and the predetermined time interval is set before the TCP session is established. Change to a time interval (t11) shorter than the time interval (t10),
Thereafter, when the TCP session is released, the time interval is changed to a time interval (t12) longer than the time interval (t11) before the TCP session is released.
Wireless access point that gives instructions. The wireless access according to claim 3, wherein the time interval (t11) shorter than the time interval (t10) before the TCP session is established can be changed according to a response importance level of communication performed by an application on the TCP session. point.   5. The wireless access point according to claim 1, further comprising means for transmitting a frame with MoreData bit set to True.