JP2013009130A - Wireless lan device and radio roaming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize communication quality between terminals actually communicating with each other by removing a harmful effect caused by depending only on RSSI which is communication quality measurement means in the MAC layer in the roaming of radio communication.SOLUTION: In the roaming of radio communication, it is determined whether or not roaming will be performed regarding actual communication between terminals on the basis of communication quality in the TCP/IP upper than the MAC layer and its application. In addition, excluding an access point which was once excluded from a roaming object from at least a next roaming object allows more stable roaming. Furthermore, communication quality at the past connection and the like can be a determination material of roaming.

Description

  The present invention relates to wireless communication in a computer network, and particularly to roaming technology for wireless LAN devices.

  In recent years, wireless LAN communication is generally used as a communication technique for computer networks. Specifically, the communication is based on a communication standard called IEEE802.11. In wireless LAN communication, two types of communication modes are used. One is called an ad hoc mode, and the other is called an infrastructure mode.

  The ad hoc mode is a method in which wireless LAN devices directly communicate with each other, and the infrastructure mode is a method in which wireless LAN devices and other network devices communicate with each other through a relay called an access point. In general, the ad hoc mode is often used in a small-scale wireless LAN environment, and the infrastructure mode is used when the size of the wireless LAN is large to some extent, such as when a wired network is used together.

  The infrastructure mode is, for example, a network environment as shown in FIG. In this environment, when the wireless LAN device 101 and the wired LAN device 102 communicate with each other, the wireless LAN device 101 communicates via any one of the access points 103 to 105.

  In the case of FIG. 1, there are three access points, the access point 103 to the access point 105, but in such a form, the wireless LAN device 101 passes the wired LAN device 102 through any access point. Can communicate with. Usually, in such a case, the wireless LAN device 101 selects and connects to the access point with the best radio wave condition. Specifically, the radio wave status is determined based on the RSSI (received signal strength) of the beacon signal periodically issued by the access point. Also, when performing roaming, which is an access point switching operation, a connection destination access point is determined based on this RSSI (Patent Document 1).

  The beacon that is the source of this RSSI measurement is communication located in the MAC (Media Access Control) layer in the stack structure of wireless communication, and the physical layer that is the lowest layer and a network represented by IP (Internet Protocol) It is located between the layers. That is, the RSSI described above is usually measured at the MAC layer.

  As a means for stabilizing communication quality, as disclosed in Patent Document 1, roaming based on RSSI can be expected to have a certain effect. However, since this roaming method is based on the assumption that the equal communication quality with strong received signal strength is good, the expected communication quality may not be obtained depending on the wireless LAN network environment.

  For example, this corresponds to a wireless LAN network environment in which a plurality of access points are concentrated in adjacent channels. In such an environment, radio wave interference or the like between adjacent channels occurs, so that lost radio frames, which are actual radio communications, occur frequently even though RSSI is good. That is, even when the RSSI value measured at the MAC layer is good, the actual communication quality may not be maintained.

  Furthermore, since roaming based on RSSI relies on RSSI as a criterion for roaming, even if the actual communication quality is poor, roaming is not performed at all because the RSSI value is good. As a result, communication quality tends to continue for a long time.

  Needless to say, in network communication including wireless communication, communication quality between terminals that actually communicate with each other, more specifically, communication quality at the application level that actually uses communication is most important. However, the conventional technology that performs roaming only with RSSI does not completely meet the expectation of ensuring communication quality in the higher layers.

JP 2010-34745 A

  The present invention solves such a problem. That is, the object of the present invention is to optimize the communication quality between terminals that actually communicate by eliminating the adverse effects of relying solely on RSSI, which is a communication quality measurement means in the MAC layer, in roaming wireless communication. To do.

  A first form according to the present invention is an access point search means for searching for nearby communicable access points and a means for switching the access points to be connected. Search from the connected access points by the access point search means A roaming means for switching connection to any one of the access points, and a communication between itself and a predetermined communication terminal via the connected access point. The roaming determination means for determining whether to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, and when the roaming determination means determines to roam, the access point search means searches for it. Access point Chi, a wireless LAN device characterized in that it comprises a roaming candidate determination means for determining an access point, except for the connected access point at that time as the target candidate for roaming by roaming means.

  The roaming target candidate determining means determines, when roaming execution is determined, an access point other than the currently connected access point as a roaming target candidate, and the wireless LAN device selects the roaming target candidate. The roaming target is determined from the inside.

  A second form according to the present invention is an access point search means for searching for nearby communicable access points and a means for switching the access points to be connected. The access point search means searches from the connected access points. A roaming means for switching connection to any one of the access points, and a communication between itself and a predetermined communication terminal via the connected access point. The roaming determination means for determining whether to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, and when the roaming determination means determines to roam, the access point search means searches for it. Is currently connected A roaming target candidate determining means for determining, as a roaming target candidate by a roaming means, an access point that has been connected in the past and has been disconnected for a predetermined time. This is a featured wireless LAN device.

  The roaming target candidate determination means restores an access point that has been connected in the past as a roaming target candidate, and the wireless LAN device determines a roaming target from all candidates including the restored access point. It becomes.

  A third form according to the present invention is an access point search means for searching for nearby communicable access points and a means for switching the access points to be connected. Search from the connected access points by the access point search means A roaming means for switching connection to any one of the access points, and a communication between itself and a predetermined communication terminal via the connected access point. The roaming determination means for determining whether to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, and when the roaming determination means determines to roam, the access point search means searches for it. Is currently connected A roaming target candidate determining unit that determines a roaming target candidate that has been connected in the past and that satisfies a predetermined duration as a roaming target candidate. This is a wireless LAN device characterized by the above.

  The roaming target candidate determination means restores an access point that has been connected in the past as a roaming target candidate, and the wireless LAN device determines a roaming target from all candidates including the restored access point. It becomes.

  According to a fourth aspect of the present invention, there is provided a wireless LAN device, an access point search means for searching surrounding access points capable of communication and a means for switching an access point to be connected. A wireless LAN device comprising roaming means for switching connection to any one of the access points searched by the point search means, and the wireless LAN device via the connected access point and a predetermined communication terminal And a roaming determination means for determining whether or not to perform roaming by the roaming means based on at least the quality of the communication higher than the MAC layer, and when the roaming determination means determines to roam, Searched by point search means Of access point, and roaming candidate determination means for determining an access point, except for the connected access point at that time as the target candidate for roaming by roaming unit, a program to function with.

  The roaming target candidate determining means determines, when roaming execution is determined, an access point other than the currently connected access point as a roaming target candidate, and the wireless LAN device selects the roaming target candidate. The roaming target is determined from the inside.

  According to a fifth aspect of the present invention, there is provided a wireless LAN device, an access point search means for searching surrounding access points capable of communication and a means for switching an access point to be connected. A wireless LAN device comprising roaming means for switching connection to any one of the access points searched by the point search means, and the wireless LAN device via the connected access point and a predetermined communication terminal And a roaming determination means for determining whether or not to perform roaming by the roaming means based on at least the quality of the communication higher than the MAC layer, and when the roaming determination means determines to roam, Searched by point search means, A roaming target candidate determining means for determining, as a roaming target candidate by the roaming means, an access point that has been connected in the past among the access points that are not currently connected, and for which a predetermined time has elapsed since disconnection; , And a program to make it function.

  The roaming target candidate determination means restores an access point that has been connected in the past as a roaming target candidate, and the wireless LAN device determines a roaming target from all candidates including the restored access point. It becomes.

  According to a sixth embodiment of the present invention, there is provided a wireless LAN device, an access point search means for searching for nearby communicable access points, and a means for switching access points to be connected. A wireless LAN device comprising roaming means for switching connection to any one of the access points searched by the point search means, and the wireless LAN device via the connected access point and a predetermined communication terminal And a roaming determination means for determining whether or not to perform roaming by the roaming means based on at least the quality of the communication higher than the MAC layer, and when the roaming determination means determines to roam, Searched by point search means, Roaming target candidate determination for determining a roaming target candidate that has been connected in the past among the access points that are not currently connected and satisfy a predetermined value at the time of connection. It is a program that functions as a means.

  The roaming target candidate determination means restores an access point that has been connected in the past as a roaming target candidate, and the wireless LAN device determines a roaming target from all candidates including the restored access point. It becomes.

  Since the present invention performs roaming based on communication quality higher than the MAC layer, for example, TCP or its application, in wireless communication roaming, compared to roaming using only RSSI, the communication is more stable in reality. Quality can be ensured.

Embodiments according to the present invention will be described below with reference to the drawings.
[Example 1]
[System overview]
An overall system diagram according to the present invention is the same as that of FIG. In the following description, it is assumed that the wireless LAN device 101 and the wired LAN device 102 communicate with each other, and the wireless LAN device 101 is connected via any one of the access points 103 to 105. Shall.

FIG. 2 shows a state in which the wireless LAN device 101 is communicating with the wireless LAN device 102 via the access point 104. Note that immediately after the wireless LAN device 101 is activated, the RSSI of a beacon emitted from each access point is measured, and the access point having the highest strength is connected. In the case of FIG. 2, the RSSI of the beacon from the access point 104 is the strongest.
[Function block diagram]

  FIG. 3 is a functional block diagram of the wireless LAN device 101. As shown in the figure, functional blocks are roughly divided into two layers, an application layer and a MAC layer, depending on the hierarchy in which they operate. The MAC layer is usually a layer on which software called a wireless driver operates. On the other hand, as will be described later, the application layer is a layer on which TCP / IP and higher-level applications (for example, FTP, TELNET, HTTP, etc.) operate.

  The wireless interface 301 and the roaming means 304, the access point search means 302, and the access point connection means 303, which are other functional blocks, are all supposed to be included in the wireless interface 301, but in the present invention, for convenience of explanation. They are listed separately.

  The access point search means 302 is a means for detecting an access point that can communicate with the wireless LAN device 101 (self). Specifically, if a beacon from an access point can be detected, it is determined that communication is possible.

  The access point connection unit 303 is a unit for actually connecting to an access point, and performs a connection at the MAC layer by performing a predetermined process defined by the IEEE802.11 standard.

  The roaming means 304 is means for switching the connection from the connected access point to another access point. Specifically, the roaming means 304 disconnects the connection with the connected access point and connects to the connection target access point. Do. The connection process performed by the roaming means 304 is the same as that of the access point connection means 303 described above.

  TCP / IP 305 operates in the application layer, and is a means for processing communication from the lower layer MAC layer by TCP / IP. The upper application 306 is a TCP / IP application in the figure, but may be UDP / IP. In that case, TCP / IP 305 becomes UDP / IP.

  The roaming determination unit 307 is a unit that is a point of the present invention, and is a unit that determines whether or not to perform roaming. The criterion is based on the actual communication quality of the TCP / IP 305 and the upper application 306. For example, for TCP / IP 305, communication quality based on parameters such as communication throughput, the number of session disconnections within a certain time exceeds a predetermined number, the window size is below a predetermined value, and there is no KeepAlive response. Judging. In either case, in TCP / IP communication, the tendency of parameters is seen when the communication quality is low. The same applies to the criteria for the upper application 306. This depends on the application protocol actually used. For example, in the case of FTP, the communication throughput is appropriate as a criterion for determination. When the determination of roaming is made, it instructs the roaming target determining means 308 described later to determine the roaming target, and changes the information indicating whether the access point is a roaming target to the roaming target changing means 309 described later. Instruct.

  The roaming target determining unit 308 determines which access point to roam based on an instruction from the roaming determining unit 307. Specifically, the access point with the strongest RSSI is selected from the other access points excluding the currently connected access point. The reason why the currently connected access points are excluded (excluded from roaming candidates) is that the currently connected access points cannot maintain the communication quality in the upper layer even though the RSSI is strong. Without this condition, the current access point is always selected, so it is an indispensable condition. When the access point to be roamed is determined, the roaming means 304 is instructed to roam.

  As will be described later with reference to FIG. 6, the roaming target changing unit 309 changes information indicating whether or not an access point can be a roaming target. If the roaming target is possible, change it to impossible.

  FIG. 4 shows information managed by the wireless LAN device 101. Specifically, this is status information indicating the RSSI of each access point detected by the access point search means 302 and whether or not it is connected. In the case of this embodiment, the access point 104 is the currently connected access point, and the access point 103 and the access point 105 are not connected. Further, it can be seen that the RSSI of the access point 104 is 90, which is the strongest RSSI among the three access points.

  FIG. 5 is a diagram showing how the wireless LAN device 101 determines a roaming target based on the information in FIG. The determination of whether or not to roam is as described above for the roaming determination means 307.

In the description of the functional block, the access point determined by the roaming target determination unit 308 is described as “selecting the access point having the strongest RSSI among other access points excluding the currently connected access point”. This is actually realized by the wireless LAN device 101 managing information as shown in FIG. That is, each access point is provided with a flag indicating whether roaming is possible or not so that the currently connected access point to be disconnected is not selected as a roaming target.
[Operation flow of wireless LAN device]

  FIG. 7 is an operation flow in the wireless LAN device 101 from when it is activated until roaming is performed. Note that the operation subject in each step is each functional block described with reference to FIG. 3, and the corresponding relationship is as shown in FIG.

  In step 701, the surrounding access points are searched and detected.

  In step 702, the access point having the strongest RSSI among the detected access points is connected. Immediately after activation, since no connection is made to any access point, the first connection is made based only on RSSI.

  In step 703, it is determined whether or not to roam. This determination criterion is as described in the roaming determination means 307 described above. A specific determination flow will be described later. As a result of the determination, if it is determined to roam, the process proceeds to step 704. Otherwise, the roaming determination process is repeated.

  In step 704, the roaming target of the connected access point is changed from enabled to disabled.

  In step 705, a connection destination access point that is a roaming target is determined. Which access point is connected is as described in the roaming target determination means 308 described above.

  In step 706, roaming is performed.

  FIG. 8 shows details of the roaming determination made in step 703. In step 801, it is determined whether the throughput of TCP communication is less than a predetermined value. As a result of the determination, if it is less than the predetermined value, the process proceeds to step 802, and if not, the process is completed.

  In step 802, it is determined whether the throughput of the upper application 306 is less than a predetermined value. As a result of the determination, if it is less than the predetermined value, the process proceeds to step 803 to execute roaming, and if not, the process is completed.

Thus, by using both the TCP communication throughput and the throughput of the upper application as the determination criteria, it is possible to more appropriately determine whether or not roaming execution is necessary. Of course, the determination can be made based on the throughput of either the TCP communication or the upper application.
[Example 2]

  In the first embodiment, access points whose communication quality has deteriorated are excluded from roaming targets. That is, in the first embodiment, the access point 104 has never been selected as a roaming target.

  However, when the wireless LAN communication is operated for a long time or the environment of the wireless LAN network changes frequently, it is necessary to restore the access point excluded from the roaming target as the roaming target on some basis. Otherwise, even if the communication quality with the last access point deteriorates, there is no next access point to be roamed, and it is necessary to continue using an access point with poor communication quality.

  Therefore, in this embodiment, for the access point excluded from the roaming target, the duration of the state in which roaming is disabled is managed, and when the duration exceeds a predetermined value, the access point can be roamed again. Revive. That is, the access point excluded from the roaming target is set as the roaming target candidate again.

  The reason for this is that the wireless LAN network environment is constantly changing, and it is considered that the communication quality obtained in the past will not become normal.

  FIG. 9 shows information managed by the wireless LAN device 101 in this embodiment. Compared to the first embodiment, the item of impossible duration is increased. This is the duration from the point when roaming is disabled. For example, the upper table shows that the access point 104 is 200 sec and the access point 103 is 60 sec. Here, when the threshold for enabling the roaming target is set to 200 sec, the roaming target is disabled from enabled as shown in the figure. Along with this, the impossible continuation time of the access point 104 is reset.

  FIG. 10 is an operation flow of the wireless LAN device according to the second embodiment. The operations according to the present embodiment are steps 1001 to 1004 in the figure, and the other steps are the same as those of the first embodiment, and thus the description thereof is omitted.

  In step 1001, counting is started to measure the duration of the original access point from when the roaming target is disabled.

  Steps 1002 to 1004 in the figure operate as tasks different from the steps described so far, and are therefore different flows.

  In step 1002, for each access point, the continuation time during which roaming is not possible is checked to determine whether a predetermined condition for reviving the roaming target is satisfied. As a result of the determination, if the condition is satisfied, the process proceeds to step 1003. Otherwise, the determination is repeated.

In step 1003, the roaming target of the access point that satisfies the resurrection condition is changed from impossible to possible, and in step 1004, the roaming disabled duration is reset. Specifically, to reset is to set the impossible duration to zero, and remains zero until the count in step 1001 is started.
[Example 3]

 In this embodiment, an access point that cannot be roamed under conditions different from those in the second embodiment is restored to allow roaming.

  FIG. 11 shows a state where the roaming target according to the present embodiment is revived. In this embodiment, the duration (communication duration) from when each access point is connected until it is disconnected by roaming is measured, and when all access points are disabled from roaming, the last roaming target The roaming target of the access point other than the access point for which the communication is disabled is revived (candidate for roaming), and the revived one is connected to the one with the highest communication duration.

  The reason for doing this is that an access point having a long communication time in the past that is expected to return to a good state again even if the quality deteriorates once. For example, even if the communication quality deteriorates due to an unexpected reason, if the state does not continue for a long time, it can be restored as a roaming target again.

  FIG. 12 is an operation flow of the wireless LAN device according to the third embodiment. Similar to the second embodiment, only steps 1201 to 1207 which are parts according to the present embodiment will be described.

  In step 1201, counting of the communication continuation time of the connected access point is started. Actually, after the wireless LAN device 101 is activated, it is a communication time with the access point connected first.

  In step 1202, it is determined whether there is a next roaming destination. Specifically, the determination is made based on whether there is an access point that can be roamed. As a result of the determination, if there is a next roaming destination, the process proceeds to step 704. If not, that is, if all the roaming targets of the access points other than the currently connected access point are not possible, the process proceeds to step 1205.

  In step 1203, the count of communication continuation time is stopped. At the time of this step, since it has already been decided to roam, counting of the communication continuation time with the currently connected access point is ended.

  In step 1204, the count of the communication continuation time is started. The start here is different from step 1201 described above, and is a count of the communication continuation time with the newly connected access point that is the roaming destination.

  In step 1205, all roaming targets of access points that cannot be roamed are set to be allowed to be restored as roamable access points.

  In step 1206, the roaming target of the connected access point is set to be disabled.

In step 1207, the access point having the longest communication continuation time is determined as the roaming target among the access points that can be roamed in step 1205.
[Summary]

  Since the present invention performs roaming based on the communication quality higher than the MAC layer, for example, TCP or its application, in wireless communication roaming, it ensures stable communication quality compared to roaming using only RSSI. be able to.

  Furthermore, once the access point excluded from the roaming target is restored to a roamable state by satisfying a predetermined condition, it becomes possible to deal with changes in the wireless LAN network environment more flexibly.

Furthermore, it is possible to respond flexibly to changes in the wireless LAN network environment by preferentially reviving and connecting the access points that have been connected for a long time.

Overall system diagram Communication link status Functional block diagram of wireless LAN equipment Information managed by wireless LAN devices Roaming (1) Roaming (2) Operation flow of wireless LAN equipment Roaming decision details Resurrection of roaming target (1) Operation flow of wireless LAN device of embodiment 2 Resurrection of roaming target (2) Operation Flow of Wireless LAN Device of Example 3

302 Access point search means 304 Roaming means 307 Roaming judgment means

Claims (6)

An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming is performed, access points other than the currently connected access point among the access points searched by the access point search means are candidates for roaming by the roaming means. A wireless LAN device comprising: a roaming target candidate determination means for determining. An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming has occurred, the access point searched by the access point search means and not connected at the present time may have been connected in the past, and a predetermined time has passed since disconnection. A wireless LAN device, comprising: a roaming target candidate determining unit that determines a target as a roaming target candidate by the roaming unit. An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming has been performed, the access point searched by the access point search means that has been connected in the past among the access points that are not currently connected, and the duration of the connection is a predetermined value. A wireless LAN device comprising: a roaming target candidate determining unit that determines a target satisfying the above as a target candidate for roaming by the roaming unit. Wireless LAN device
An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming is performed, access points other than the currently connected access point among the access points searched by the access point search means are candidates for roaming by the roaming means. A program that functions as a roaming target candidate determination means for determining. Wireless LAN device
An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming has occurred, the access point searched by the access point search means and not connected at the present time may have been connected in the past, and a predetermined time has passed since disconnection. That functions as a roaming target candidate determination unit that determines a candidate for roaming by the roaming unit. Wireless LAN device
An access point search means for searching for access points around which communication is possible;
A wireless LAN comprising means for switching an access point to be connected, and roaming means for switching a connection to any one of the access points searched by the access point search means from the connected access points Equipment,
Determines whether or not to perform roaming by the roaming means based on the quality of the communication at least above the MAC layer, which is communication between itself and a predetermined communication terminal via the connected access point Roaming judgment means,
If it is determined by the roaming determination means that roaming has been performed, the access point searched by the access point search means that has been connected in the past among the access points that are not currently connected, and the duration of the connection is a predetermined value. A program that functions as a roaming target candidate determination unit that determines a candidate satisfying the above as a roaming target candidate by the roaming unit.