JP2004207922A - Wireless lan system and handover processing method used for same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless LAN system, capable of interchanging a wireless zone channel and a wired zone channel with each other, in a data link layer with communication being maintained between the ends. <P>SOLUTION: When communication starts between wireless base station apparatuses 11, 12, a wireless terminal device 21 performs a scan process about all available frequencies, to keep connectable wireless base station apparatuses 11, 12 in an AP connection candidate list beforehand. While communicating with a communication terminal 31 on a wired network via the wireless base station apparatus 11, when the wireless terminal device 21 detects that the wireless zone communication between the wireless terminal device 21 and the wireless base station apparatus 11 is broken, the wireless terminal device extracts information on frequency and the wireless base station apparatus 12 from the AP connection candidate list, without performing rescanning processing, so that reduction in hand over process time can be realized. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a wireless LAN system and a handover processing method used for the same, and more particularly, to a handover processing method in a wireless terminal device included in a wireless LAN (Local Area Network) system.
[0002]
[Prior art]
Conventionally, a wireless LAN system has a basic service unit in which one wireless base station apparatus and a plurality of wireless terminal apparatuses perform communication between a wireless terminal apparatus and a wireless base station apparatus using a specific frequency. There is a system configured with a plurality of service units.
[0003]
In this wireless LAN system, for example, when a wireless terminal device is communicating with a communication terminal on a wired network via a wireless base station device, wireless section communication between the wireless terminal device and the wireless base station device is disconnected. When the wireless terminal device detects that the wireless base station device has been re-scanned, the wireless terminal device performs a handover process of searching for a wireless base station device. That is, in the conventional wireless LAN system, switching of the wireless base station device occurs as the wireless terminal device moves (for example, see Patent Document 1).
[0004]
[Patent Document 1]
JP-A-2002-271345 (pages 3, 4 and FIG. 4)
[0005]
[Problems to be solved by the invention]
In the above-described conventional wireless LAN system, there is a problem in that each time the wireless communication between the wireless terminal device and the wireless base station device is disconnected in the wireless terminal device, a time-consuming scan process must be performed.
[0006]
The scanning process performed by the wireless terminal device is a process that requires a response waiting time from the wireless base station device and must be performed for all frequencies, and is a very time-consuming process. Therefore, there is a problem in performing a handover process involving a scan process while maintaining a connection at the network layer or higher.
[0007]
Further, in the conventional wireless LAN system, when the wireless terminal device performs the handover process, switching of a communication path in a wired section between a communication terminal on a wired network communicating with the wireless terminal device and the wireless base station device is considered. Since there is no handover processing method described above, there is no guarantee that the destination of the packet transmitted from the communication terminal to the wireless terminal device reaches the wireless base station device after the handover process properly by the handover process in the wireless section.
[0008]
SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to solve the above-mentioned problems and to provide a wireless LAN system capable of switching a communication path between a wireless section and a wired section in a data link layer while maintaining end-to-end communication, and a handover processing method used therefor. Is to provide.
[0009]
[Means for Solving the Problems]
The wireless LAN system according to the present invention is a wireless LAN system in which one wireless base station device and a plurality of wireless terminal devices communicate with each other using a specific frequency and are configured with a plurality of basic service units. So,
An AP connection candidate list holding a scan processing result for searching for the wireless base station device connectable for all the frequencies that can be used in advance, and the wireless connection communication with any wireless base station device when the wireless section communication is cut off Means for retrieving an AP connection candidate list and determining a wireless base station apparatus to be a new connection destination.
[0010]
Another wireless LAN system according to the present invention is a wireless LAN configured by collecting a plurality of basic service units in which one wireless base station apparatus and a plurality of wireless terminal apparatuses communicate with each other using a specific frequency. The system
The wireless base station device is provided with a learning table for centrally managing information on the wireless terminal devices that have performed wireless zone communication within a predetermined period.
[0011]
The handover processing method according to the present invention provides a wireless LAN system configured by collecting a plurality of basic service units in which one wireless base station apparatus and a plurality of wireless terminal apparatuses communicate with each other using a specific frequency. In a handover processing method, the wireless terminal device performs a scan process for searching for the connectable wireless base station device for all available frequencies in advance, and stores the result in an AP connection candidate list, When the wireless zone communication with an arbitrary wireless base station device is disconnected, the AP connection candidate list is searched to determine a wireless base station device to be a new connection destination.
[0012]
Another handover processing method according to the present invention is directed to a wireless LAN configured by collecting a plurality of basic service units in which one wireless base station apparatus and a plurality of wireless terminal apparatuses communicate with each other using a specific frequency. In a handover processing method for a system, the wireless base station device centrally manages information of the wireless terminal devices that have performed wireless zone communication within a predetermined period of time in a learning table.
[0013]
That is, the wireless LAN system of the present invention is a basic service unit that one wireless base station device and a plurality of wireless terminal devices perform communication between the wireless terminal device and the wireless base station device using a specific frequency, In a wireless LAN system configured with a plurality of basic service units, the present invention relates to a wireless terminal device belonging to a plurality of basic service units, that is, a device that can be connected to a plurality of wireless base station devices.
[0014]
In the wireless LAN system according to the present invention, a scanning process is performed in the wireless terminal device in advance to search for a wireless base station device connectable to all available frequencies, the result is held as a connection candidate list, and an arbitrary wireless base When the wireless section communication with the station device is disconnected, a wireless base station device to restart communication in a short time is determined by searching a connection candidate list.
[0015]
Further, in the wireless LAN system of the present invention, in addition to the above reconnection processing, by configuring the wireless base station apparatus as a bridge, wireless section communication between the wireless terminal apparatus and the wireless base station apparatus is disconnected / reconnected. It is characterized in that the communication path between the wireless section and the wired section in the data link layer is switched while maintaining the end-to-end communication without notifying the upper layer above the network layer of the fact.
[0016]
More specifically, in the wireless LAN system of the present invention, the wireless base station apparatus AP # 1 and the wireless terminal apparatuses STA # 1 and STA # 2 use a specific common frequency F1 to establish a wireless terminal apparatus-wireless base station. A basic service unit BSS # 1 for performing inter-station device communication is configured, and the wireless base station device AP # 2 and the wireless terminal devices STA # 1, STA # 3, and STA # 4 wirelessly use a specific common frequency F2. When configuring the basic service unit BSS # 2 for performing communication between the terminal device and the wireless base station device, the wireless terminal device STA # 1 belongs to a plurality of basic service units BSS # 1 and BSS # 2.
[0017]
When starting communication with the wireless base station apparatus, the wireless terminal apparatus STA # 1 performs a scan process on all available frequencies, and connects the connectable wireless base station apparatuses AP # 1 and AP # 2 in advance to the AP. Keep it in the candidate list. The AP connection candidate list stores information that the radio base station device AP # 1 can be connected at the frequency F1 and the radio base station device AP # 2 can be connected at the frequency F2.
[0018]
In such a configuration, for example, when the wireless terminal STA # 1 is communicating with the communication terminal ND # 1 on the wired network via the wireless base station AP # 1, the wireless terminal STA # 1-wireless When detecting that the wireless section communication between the base station apparatuses AP # 1 has been disconnected, the wireless terminal apparatus STA # 1 does not perform the rescanning process to search for the wireless base station apparatus AP # 2, but an AP connection candidate. By extracting information on the frequency F2 and the wireless base station device AP # 2 from the list, the handover processing time can be reduced.
[0019]
In addition, the wireless base station devices AP # 1 and AP # 2 store the wireless terminal devices existing in their own basic service units BSS # 1 and BSS # 2 in the learning table in the data link layer communication, It is possible to determine whether or not to transfer a packet arriving from the wired side to the wireless terminal side, and to maintain communication between the wireless terminal apparatus STA # 1 and the communication terminal ND # 1 in an upper layer above the network layer. It is characterized in that a communication path is switched between a wireless section and a wired section in the data link layer.
[0020]
As described above, in the wireless LAN system of the present invention, since the wireless terminal device has the connection candidate list, the rescanning process during the handover process can be omitted, and the processing time can be reduced. Further, in the wireless LAN system of the present invention, the wireless base station apparatus has a learning table, and a communication path switching processing function in the data link layer on the wired side is added, so that the wireless base station apparatus can communicate between the wireless terminal apparatus and the wireless base station apparatus. It is possible to switch the communication path between the wireless section and the wired section in the data link layer while maintaining the communication between the end and the end without notifying the upper layer above the network layer that the wireless section communication has been disconnected. .
[0021]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a configuration of a wireless LAN system according to one embodiment of the present invention. In FIG. 1, a wireless LAN system according to an embodiment of the present invention includes wireless base station apparatuses (AP # 1, AP # 2) 11, 12 and wireless terminal apparatuses (STA # 1, STA # 2, STA # 3, STA). # 4) 21 to 24 and a communication terminal (ND # 1) 31.
[0022]
The wireless base station devices 11 and 12 have a bridge function for connecting the wireless terminal device 21 and devices on a wired network. The wireless terminal device 21 is a communication terminal equipped with a wireless device, and can communicate with a communication terminal 31 existing on a wired network such as Ethernet (R) via the wireless base station device 11 or the wireless base station device 12. It has become.
[0023]
In the wireless LAN system according to one embodiment of the present invention, a basic service unit in which the wireless base station device 11 and the wireless terminal devices 21 and 22 perform communication between the wireless terminal device and the wireless base station device using a specific common frequency F1. (BSS # 1) 101, a basic service unit in which the wireless base station apparatus 12 and the wireless terminal apparatuses 11, 13, and 14 perform communication between the wireless terminal apparatus and the wireless base station apparatus using the specific common frequency F2. (BSS # 2) 102. In this case, the wireless terminal device 21 belongs to a plurality of basic service units 101 and 102.
[0024]
FIG. 2 is a block diagram showing the configuration of each of the wireless base station devices 11 and 12, the wireless terminal device 21, and the communication terminal 31 in FIG. FIG. 2 shows a configuration in which the wireless terminal device 21 communicates with the communication terminal 31 via the wireless base station device 11 or the wireless base station device 12.
[0025]
The wireless base station apparatuses 11 and 12 respectively include the wireless transmission / reception units 111 and 121, the wired transmission / reception units 112 and 122, and the presence of the own apparatus as a beacon signal at regular intervals within the basic service unit (the wireless path side) of the own apparatus. Beacon transmission units 113 and 123 for reporting, learning tables 114 and 124 for registering information of wireless terminal devices existing within the basic service unit of the own device, and a registration deadline for the learning tables 114 and 124. Release timers 115 and 125 are provided.
[0026]
On the other hand, the radio terminal device 21 includes a radio transmission / reception unit 211 for performing communication with the radio base station devices 11 and 12, a beacon reception unit 212 for detecting a beacon signal from each of the radio base station devices 11 and 12, A frequency switching unit 213 for switching a frequency to be used, and an AP connection candidate list 214 for storing a used frequency of a detected beacon signal and a wireless base station device name are provided. Further, the communication terminal 31 includes a wired transmission / reception unit 311.
[0027]
Upon starting communication with the wireless terminal devices existing in the basic service units 101 and 102 of the own device, the wireless base station devices 11 and 12 always keep beacon signals of the frequency used by the own device.
[0028]
As shown in FIG. 1, adjacent base service units 101 and 102 use different frequencies so as to prevent interference. Therefore, the radio base station apparatus 11 and the radio base station apparatus 12 broadcast beacon signals of different frequencies, The use frequency of the own device is notified to the wireless terminal devices existing in the basic service units 101 and 102 of the own device.
[0029]
In addition, the wireless base station apparatuses 11 and 12 store the MAC (Medium Access Control) address (source data link layer address) of the wireless terminal apparatus included in all wireless communication packets received by the wireless transmitting and receiving units 111 and 121 in the learning table 114, After that, the wired transmission / reception units 112 and 122 compare the destination address of the communication packet received from the wired side with the destination address of the communication packet received from the wired side. Transfer to wireless side.
[0030]
Further, the wireless base station apparatuses 11 and 12 periodically monitor the learning tables 114 and 124 using the release timers 115 and 125, and delete wireless terminal apparatuses that have not communicated for a certain period of time from the learning tables 114 and 124. I do.
[0031]
FIG. 3 is a diagram illustrating an example of a packet format in the data link layer. In FIG. 3, the wireless data packet Pk1 has at least a destination address part Pk11 and a source address part Pk12 as a data link header part, and a data link payload part contains an upper layer packet.
[0032]
In the case of a wireless data packet transmitted from the wireless terminal device 21, the MAC address of the communication terminal 31 is stored in the destination address portion Pk11, and the MAC address of the wireless terminal device 21 is stored in the source address portion Pk12.
[0033]
The wired data packet Pk2 also has at least a destination address portion Pk21 and a source address portion Pk22 as a data link header portion similarly to the above-described wireless data packet Pk1, and accommodates an upper layer packet in a data link payload portion. ing.
[0034]
In the case of a packet transmitted from the communication terminal 31, the MAC address of the wireless terminal device 21 is stored in the destination address portion Pk21, and the MAC address of the communication terminal 31 is stored in the source address portion Pk22.
[0035]
The wireless control packet Pk3 used when transmitting a connection request or the like from the wireless terminal device 21 to the wireless base station devices 11 and 12 includes at least a destination address portion Pk31 and a source address portion P3k2 as a data link header portion. And a control command Pk33 as a data link payload section.
[0036]
Furthermore, the wireless ACK packet Pk4 for responding to the wireless control packet Pk3 has at least a destination address part Pk41 and a source address part Pk42 as a data link header part, and determines whether communication is possible as a data link payload part. Response information (OK / NG) Pk43 indicating whether or not this is the case.
[0037]
FIG. 4 is a diagram showing a configuration example of the learning table 114 in FIG. In FIG. 4, a learning table 114 includes a STA MAC address 1141 for holding a MAC address of a wireless terminal device with which wireless section communication has been performed within a predetermined period, a release counter 1142 indicating a registration deadline to the learning table 114, and Has the following two attributes. Although the learning table 124 is not shown, it has the same configuration as the learning table 114.
[0038]
Upon receiving a wireless packet (wireless data packet Pk1 or wireless control packet Pk3) from any of the wireless terminal devices 21 to 24, the wireless base station devices 11 and 12 transmit the wireless packet from the source address portions Pk12 and Pk32 of the received wireless packet. The MAC address of each of the terminal devices 21 to 24 is obtained, and it is checked whether or not the MAC address is registered in the learning tables 114 and 124. If the MAC address is not registered, the MAC address is registered, the corresponding release counter 1142 is reset, and the registration is already performed. If done, the MAC address is not re-registered, and only the corresponding release counter 1142 is reset.
[0039]
The learning tables 114 and 124 are periodically monitored by release timers 115 and 125, and all release counters 1142 in the learning tables 114 and 124 are incremented at regular time intervals. As a result, if the release counter 1142 exceeds a certain value (the upper limit L determined by the release counter 1142), it is determined that there has been no communication from the wireless terminal devices 21 to 24 of the corresponding MAC address for a certain period, and the wireless terminal device The registrations 21 to 24 are deleted from the learning tables 114 and 124.
[0040]
On the other hand, when starting communication with the wireless base station apparatus 11 or the wireless base station apparatus 12, the wireless terminal apparatus 21 changes the designated frequency of the frequency switching unit 213 for all available frequencies in advance, and The beacon signal is scanned by the beacon receiving unit 212 and the result is stored in the AP connection candidate list 214.
[0041]
Thereafter, the wireless terminal device 21 fixes the designated frequency of the frequency switching unit 213 to the frequency of any of the wireless base station devices 11 and 12 in the AP connection candidate list 214, and transmits a beacon signal from the corresponding wireless base station device 11 or 12 to a beacon. While the receiving section 212 continues receiving, it recognizes that the wireless section with the corresponding wireless base station apparatus 11 or 12 is communicable.
[0042]
FIG. 5 is a diagram showing a configuration example of the AP connection candidate list 214 in the wireless terminal device 21 of FIG. In FIG. 5, the AP connection candidate list 214 is a scan performed for all frequencies {f1, f2,..., Fn} that can be used to search for the wireless base station apparatuses 11 and 12 to which the wireless terminal apparatus 21 can connect. This is for holding the processing result, and has at least two attributes of the usable frequency AL1 and the radio base station device name AL2, and includes the same number of rows as the number (n) of usable frequencies.
[0043]
As a result of the scanning process, the wireless terminal device 21 extracts information for identifying the wireless base station devices 11 and 12 from the beacon signal for the frequency at which the beacon signal was received, and stores the information in the wireless base station device name AL2. For example, in the wireless terminal device 21, information indicating that the wireless base station device 11 can be connected at the frequency F1 and the wireless base station device 12 can be connected at the frequency F2 is obtained from the scan processing result, so that F1 = f1, F2 = When fn is set, information indicating the wireless base station device names AP # 1 and AP # 2 is stored in the wireless base station device names AL2 in the f1 and fn rows of the AP connection candidate list.
[0044]
FIG. 6 is a diagram showing a protocol hierarchy between the end and end of the wireless terminal device 21 of FIG. 1 and the communication terminal 31 that is the communication partner thereof. In FIG. 6, a protocol layer between an end and a wireless terminal (STA # 1) 21 and a communication terminal (ND # 1) 31 is a data link layer that establishes a communication environment using a wireless / wired communication medium. Sd1 and Nd1; network layers Sd2 and Nd2 for establishing communication at an IP (Internet Protocol) network level; and communication control at end-to-end levels such as TCP (Transmission Control Protocol) and UDP (User Datagram Protocol). And the transport layers Sd3 and Nd3.
[0045]
The wireless base station devices (AP # 1, AP # 2) 11, 12 are communication devices having a bridge function and performing route selection in the data link layer Ad1.
[0046]
In the handover process according to the present embodiment, when the wireless terminal device (STA # 1) 21 detects that the wireless communication channel c1 with the wireless base station device (AP # 1) 11 has been disconnected from the reception state of the beacon signal. The communication with the wireless base station device (AP # 2) 12 is started using the above-described processing method for searching the AP connection candidate list 124, and the wireless communication channel c1 is restored in a short time.
[0047]
In this case, since the wireless base station device as the relay device changes from AP # 1 to AP # 2, the route of the wired section communication path c2 also changes. In the wireless base station device (AP # 2) 12, the wireless transmission / reception unit 121 newly receives a wireless packet (wireless data packet Pk1 or wireless control packet Pk3) from the wireless terminal device (STA # 1) 21 to make the learning table. The MAC address of the wireless terminal device (STA # 1) 21 is registered in 124, and a wired section communication path c2 with the communication terminal (ND # 1) 31 is established.
[0048]
Conversely, since the wireless base station device (AP # 1) 11 does not receive a wireless packet (wireless data packet Pk1 or wireless control packet Pk3) from the wireless terminal device (STA # 1) 21 for a certain period of time, the learning table 114 The registration of the MAC address of the wireless terminal device (STA # 1) 21 is deleted, and the wired section communication path c2 with the communication terminal (ND # 1) 31 is closed.
[0049]
As described above, in the present embodiment, even when the communication path in the data link layer is changed, the communication layer above the network layer is not notified of the disconnection of the communication. That is, in the present embodiment, a connection c3 in the network layer where communication is established between the wireless terminal device (STA # 1) 21 and the communication terminal (ND # 1) 31, and an end-to-end session in the transport layer. It is possible to switch only the wireless section communication path c1 and the wired section communication path c2 in the data link layer while holding c4.
[0050]
In normal LAN communication, since the IP layer is connectionless, TCP is used for the transport layer when performing connection-type communication. However, in the case of a short-time route change in the handover process according to the present embodiment, Since the switching within the session holding time in the TCP protocol becomes possible, lower-layer communication disconnection is performed for a user using the wireless terminal device (STA # 1) 21 and the communication terminal (ND # 1) 31. Communication can be continued in the same session without being noticed.
[0051]
FIG. 7 is a sequence chart showing operations up to the creation of the AP connection candidate list 214 in FIG. 2, and FIG. 8 is a sequence chart showing operations up to the start of wireless zone communication according to an embodiment of the present invention. 9 is a sequence chart showing a handover process according to one embodiment of the present invention, and FIG. 10 is a flowchart showing a handover process including a rescan process according to one embodiment of the present invention. An example of the operation of the handover process in one embodiment of the present invention will be described with reference to FIGS.
[0052]
In FIG. 7, the wireless terminal device (STA # 1) 21 sets a wireless base station device (AP # 1) 11 using the frequency f1 and a wireless base station device (AP # 2) 12 using the frequency fn as an AP connection candidate. The operation of registering in the list 214 is shown.
[0053]
In this case, first, in order to search for all connectable wireless base station apparatuses, the wireless terminal apparatus (STA # 1) 21 starts up the STA (a1 in FIG. 7) immediately after starting up the STA (a1 in FIG. 7). The scanning process is started (a2 in FIG. 7).
[0054]
Subsequently, the wireless terminal device (STA # 1) 21 receives the beacon signal from the wireless base station device (AP # 1) 11 as a result of the scan processing of the frequency f1 (a3 in FIG. 7), and stores the beacon signal in the AP connection candidate list 214. The information of the wireless base station device (AP # 1) 11 is stored (a4 in FIG. 7).
[0055]
In addition, the wireless terminal device (STA # 1) 21 cannot receive anything as a result of the scanning process up to the frequencies f2 to fn-1, and the wireless base station device (AP # 2) 12 performs the scanning process at the frequency fn. (A5 in FIG. 7), and stores information of the wireless base station device (AP # 2) 12 in the AP connection candidate list 214 (a6 in FIG. 7).
[0056]
As described above, the scanning process in the wireless terminal device (STA # 1) 21 is completed, and at this time, information on the frequencies usable by the wireless terminal device (STA # 1) 21 and the connectable wireless base station devices is stored. The AP connection candidate list 214 (see FIG. 5) is created (a7 in FIG. 7).
[0057]
FIG. 8 shows a sequence until the wireless terminal device (STA # 1) 21 starts wireless zone communication with an arbitrary wireless base station device registered in the AP connection candidate list 214. Here, a method of determining a wireless base station device that performs communication first from a plurality of wireless base station devices registered in the AP connection candidate list 214 may be any method and is not directly related to the present invention. The description is omitted.
[0058]
In this case, the wireless terminal device (STA # 1) 21 sets the wireless base station device (AP # 1) 11 as an arbitrary wireless base station device from the AP connection candidate list 214 (see FIG. 5) created by the above-described processing. Assume that you have selected.
[0059]
In order to start communication with the wireless base station device (AP # 1) 11, the wireless terminal device (STA # 1) 21 first sets a frequency designated by the frequency switching unit 213 to the beacon receiving unit 214. (AP # 1) 11 is fixed to the frequency F1 (= f1) used (b1 in FIG. 8).
[0060]
Subsequently, the wireless terminal device (STA # 1) 21 issues a connection request packet (wireless control packet Pk3) to the wireless base station device (AP # 1) 11 (b2 in FIG. 8). The wireless base station device (AP # 1) 11 returns a wireless ACK packet Pk4 including response information indicating that communication is possible to the wireless terminal device (STA # 1) that has received the connection request packet (b3 in FIG. 8). The MAC address of the wireless terminal device (STA # 1) 21 is extracted from the source address portion Pk32 of the received connection request packet, stored in the STA MAC address 1141 of the learning table 114 of the own device, and corresponds to the STA MAC address 1141. The release counter 1142 is reset (b4 in FIG. 8).
[0061]
Since the wireless terminal device (STA # 1) 21 is stored in the learning table 114 of the wireless base station device (AP # 1) 11, the wireless base station device (AP # 1) 11 and the communication terminal (ND # 1) ) Recognize establishment of a wired section communication path with 31.
[0062]
Further, the wireless terminal device (STA # 1) 21 receives the wireless ACK packet Pk4 from the wireless base station device (AP # 1) 11, and thereby establishes a wireless communication path with the wireless base station device (AP # 1) 11. The communication between the wireless terminal device (STA # 1) 21 and the communication terminal (ND # 1) 31 at the network layer and above is started at the same time as the recognition of the establishment of (b5 in FIG. 8) (b6, b7 in FIG. 8). ).
[0063]
Further, the wireless terminal device (STA # 1) 21 always checks whether or not a beacon signal from the wireless base station device (AP # 1) 11 can be received, and the wireless terminal device (STA # 1) 11 communicates with the wireless base station device (AP # 1) 11. Monitor that is maintained.
[0064]
In FIG. 9, the wireless terminal device (STA # 1) 21 detects that the wireless communication with the wireless base station device (AP # 1) 11 has been disconnected, and the handover to the wireless base station device (AP # 2) 12 is performed. The operation for performing the processing is shown.
[0065]
In this case, it is assumed that the wireless terminal device (STA # 1) 21 is communicating with the communication terminal (ND # 1) 31 via the wireless base station device (AP # 1) 11 (c1, c2 in FIG. 9). Since the beacon signal from the wireless base station device (AP # 1) 11 has been interrupted (c3 in FIG. 9), the wireless terminal device (STA # 1) 21 has a wireless section with the wireless base station device (AP # 1) 21. It is detected that the communication has been disconnected (c4 in FIG. 9).
[0066]
As a result, the wireless terminal device (STA # 1) 21 searches the AP connection candidate list 214 and selects a wireless base station device (AP # 2) 12 that can be newly connected. The frequency switching unit 213 changes the frequency specified for the beacon receiving unit 212 to the frequency F2 (= fn) used by the wireless base station device (AP # 2) 12 (c5 in FIG. 9), and the wireless terminal device (STA). # 1) 21 transmits a connection request packet (wireless control packet Pk3) to the wireless base station device (AP # 2) 12 (c6 in FIG. 9).
[0067]
Upon receiving the connection request packet, the wireless base station device (AP # 2) 12 returns a wireless ACK packet Pk4 including response information indicating that communication is possible to the wireless terminal device (STA # 1) 21 (FIG. 9). C7), the MAC address of the wireless terminal device (STA # 1) 21 is stored in the STA MAC address 1141 of the learning table 124 of the own device, and the release counter 1142 corresponding to the STA MAC address 1141 is reset (c8 in FIG. 9). ).
[0068]
Since the wireless terminal device (STA # 1) 21 is stored in the learning table 124 of the wireless base station device (AP # 2) 12, the wireless base station device (AP # 2) 12 and the communication terminal (ND # 1) ) Recognize establishment of a wired section communication path with 31. Further, the wireless terminal device (STA # 1) 21 receives the wireless ACK packet Pk4 in response to the connection request, thereby recognizing the establishment of a wireless communication channel with the wireless base station device (AP # 2) 12 (FIG. 9). c9-c11).
[0069]
In the above process, no communication disconnection / switching is notified to the network layer and above, and the communication between the wireless terminal device (STA # 1) 21 and the communication terminal (ND # 1) 31 between the end and the end. Is maintained, the handover process ends.
[0070]
The handover process according to one embodiment of the present invention is performed as described above. However, in an actual wireless LAN environment, the wireless terminal device may be affected by various factors such as movement of the wireless terminal device and the operation status of the wireless base station device. From the AP connection candidate list created at the time of performing the scan processing for the first time, it is assumed that a wireless base station apparatus as a new connection destination cannot be found. In that case, the scan processing is performed again, and a new AP is performed. The connection candidate list needs to be recreated. Therefore, a handover process according to an embodiment of the present invention including a process of re-creating the AP connection candidate list 214 will be described with reference to FIG.
[0071]
The wireless terminal device (STA # 1) 21 starts handover processing by detecting that the beacon signal from the currently connected wireless base station device (AP # 1) 11 has been interrupted. The wireless terminal device (STA # 1) 21 searches the AP connection candidate list 124 for a new connection destination wireless base station device. It is checked whether a device exists (step S1 in FIG. 10).
[0072]
When there is a wireless base station device that has never been referred to, the wireless terminal device (STA # 1) 21 fixes the frequency specified by the frequency switching unit 213 to the frequency used by the wireless base station device, and It waits for a time and checks whether or not a beacon signal can be received (step S2 in FIG. 10).
[0073]
When the wireless terminal device (STA # 1) 21 can receive a beacon signal from the wireless base station device within a predetermined time, the wireless terminal device (STA # 1) 21 newly uses the frequency and the wireless base station device referred to in the AP connection candidate list 214. Is determined (step S3 in FIG. 10), the process proceeds to a connection request process (step S4 in FIG. 10), and the handover process ends.
[0074]
On the other hand, if the beacon signal has not been received even after waiting for a certain period of time, the wireless terminal device (STA # 1) 21 returns to the process of step S1 to refer to the AP connection candidate list 214 again.
[0075]
If the wireless terminal device (STA # 1) 21 cannot find a new wireless base station device to connect to even if it refers to all wireless base station devices registered in the AP connection candidate list 214, The scanning process for all the frequencies is performed again (step S5 in FIG. 10), a new AP connection candidate list 214 is created from the result (step S6 in FIG. 10), and the wireless base station device of the connection destination is determined from the AP connection candidate list 214. The process returns to step S1 to search.
[0076]
As described above, in the present embodiment, in the wireless terminal device (STA # 1) 21, scan processing for searching for a connectable wireless base station device for all available frequencies is performed in advance, and the result is referred to as an AP connection candidate. The list 214 is stored as a list, and when the wireless zone communication with an arbitrary wireless base station device is disconnected, the AP connection candidate list 214 is searched without performing the re-scanning process, so that the wireless connection to be a new connection destination is performed. The base station device can be determined.
[0077]
Further, in the present embodiment, the wireless terminal apparatus (STA # 1) 21 determines the wireless base station apparatus by searching the AP connection candidate list 214 without performing the rescanning process. Thus, the re-establishment of the wireless communication path in the data link layer can be realized.
[0078]
Further, in the present embodiment, in the wireless base station devices (AP # 1, AP # 2) 11, 12, the information of the wireless terminal device (STA # 1) 21 with which the wireless section communication has been performed within a certain period is stored in a learning table. Since the centralized management is performed as 114 and 124, the packets received by the wireless base station apparatuses (AP # 1 and AP # 2) 11 and 12 at the wired transmission / reception units 112 and 122 are sent to the correct wireless terminal apparatus (STA # 1) 21. Can be sent. That is, in the present embodiment, it is possible to prevent packet transfer to the wireless terminal device (STA # 1) 21 that is out of the basic service unit managed by the own device, and to prevent transmission of an illegal packet.
[0079]
Furthermore, in the present embodiment, an AP connection candidate list 214 in the wireless terminal device (STA # 1) 21 and learning tables 114 and 124 in the wireless base station devices (AP # 1 and AP # 2) 11 and 12 are provided. Accordingly, even when a route change in the data link layer is necessary, the communication path can be restored in a short time in both the wireless section and the wired section, and the wireless terminal device (STA # 1) 21 or the communication terminal (ND # 1) It is possible for the user using 31 to continue the communication in the same session without noticing the disconnection of the lower layer communication.
[0080]
In this embodiment, the wireless terminal device (STA # 1) 21 cannot receive beacon signals from the wireless base station devices (AP # 1 and AP # 2) 11 and 12 communicating the start point of the handover process. Although it is assumed that it is detected that the handover process is actually performed, it may be implemented in consideration of a case where a handover process is required in addition to this factor. For example, in a case where retransmission is repeatedly performed in an upper layer even when a beacon signal can be received, it may be determined that it is better to communicate with another wireless base station apparatus, and a handover process may be started.
[0081]
In the present embodiment, the AP connection candidate list 214 is updated only when the scan processing is performed. However, the AP connection candidate list 214 is updated until the next time the AP connection candidate list 214 needs to be referred to. By adding a process of deleting the registration of the wireless base station devices (AP # 1, AP # 2) 11 and 12 registered in the candidate list 214, the AP connection candidate list 214 reflecting the actual communication environment is added. Functions may be added. For example, in the present embodiment, the AP connection candidate list 214 is created based on whether or not a beacon has been received. However, even when a beacon signal is received, communication is not permitted due to higher layer authentication or the like. Alternatively, the registration may be deleted from the AP connection candidate list 214 when the authentication fails.
[0082]
Furthermore, in the present embodiment, the AP connection candidate list 214 is a list having at least two attributes of the usable frequency and the wireless base station device name. The device name need not be particularly specified. In addition, since the beacon signal (or probe frame) has information indicating communication quality such as a reception level, such detailed information may be added as a new attribute when the AP connection candidate list 214 is created.
[0083]
Furthermore, in the present embodiment, the learning tables 114 and 124 in the wireless base station devices (AP # 1 and AP # 2) 11 and 12 have two attributes of the STA MAC address and the release counter, and the wireless terminal device Upon receiving the wireless section communication packet from (STA # 1) 21, the wireless base station devices (AP # 1, AP # 2) 11, 12 change the MAC address of the wireless terminal device (STA # 1) 21 to the STA MAC address 1141. The release counter 1142 is stored and reset, and the release counter 1142 of the learning tables 114 and 124 is incremented each time the release timers 115 and 125 in the radio base station apparatuses (AP # 1 and AP # 2) 11 and 12 perform regular monitoring. By doing so, the wireless terminal devices (ST # 1) manages the 21 registration deadline.
[0084]
However, such a counter method is not necessary. For example, instead of the release counter 1142, a wireless terminal device (STA #) that has a time stamp for holding the last packet arrival time as an attribute and records the time before a certain time during the regular monitoring of the release timers 115 and 125. 1) 21 may be deleted from the learning tables 114 and 124.
[0085]
In the present embodiment, the handover processing when the mobile terminal (STA # 1) 21 shown in FIG. 1 is located at a position that can belong to two basic service units has been described. The basic service unit that can be processed, that is, the maximum number of wireless base station devices matches the number of frequencies that can be used by the wireless terminal device (STA # 1) 21 that performs the handover process. Therefore, the handover process in this embodiment can be performed even when the number of wireless base station devices is three or more, that is, in a unit of a basic service.
[0086]
Further, in this embodiment, the probe frame can be used for the scanning process for the wireless terminal device (STA # 1) 21 to search for the wireless base station devices (AP # 1, AP # 2) 11, 12. is there. In the wireless LAN system defined by IEEE802.11, the wireless terminal device (STA # 1) 21 searches for the wireless base station devices (AP # 1 and AP # 2) 11 and 12 according to a method in which the wireless terminal device has a certain frequency. A passive scan method of detecting a connectable wireless base station device by receiving a beacon signal from the wireless base station device while waiting for a certain time, and a probe request frame to the wireless base station device at a certain frequency in the wireless terminal device. When transmitted, the frequencies match, and the wireless base station apparatus that has received the probe request frame returns a probe response frame, and there are two methods, an active scan method that detects a connectable wireless base station apparatus.
[0087]
The probe response frame is a frame defined by IEEE802.11 similarly to the above-described beacon signal, and thus does not need to be newly defined for this embodiment. Since the probe response frame stores information for identifying the wireless base station device equivalent to the beacon signal, the difference between the information in the beacon signal and the information in the probe response frame is used as information for registration in the AP connection candidate list 214. Does not occur.
[0088]
Furthermore, in the present embodiment, the operation related to the wireless terminal device (STA # 1) 21 has been described, but the other wireless terminal devices (STA # 2 to # 4) 22 to 24 also have the above-described wireless terminal device (STA # 1). ) 21 is the same as the configuration and operation.
[0089]
【The invention's effect】
As described above, the present invention provides a wireless LAN system in which one wireless base station apparatus and a plurality of wireless terminal apparatuses collectively include a plurality of basic service units for performing communication between them using a specific frequency. In, the wireless terminal device performs a scan process for searching for a connectable wireless base station device for all available frequencies in advance and holds the result in an AP connection candidate list, and By searching the AP connection candidate list when the wireless section communication is disconnected and determining the wireless base station apparatus to be the new connection destination, the wireless section and the wired section in the data link layer can be maintained while maintaining the end-to-end communication. The effect that the communication path of the section can be switched can be obtained.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a wireless LAN system according to one embodiment of the present invention.
FIG. 2 is a block diagram illustrating a configuration of each of a wireless base station device, a wireless terminal device, and a communication terminal in FIG. 1;
FIG. 3 is a diagram illustrating an example of a packet format in a data link layer.
FIG. 4 is a diagram illustrating a configuration example of a learning table in FIG. 2;
FIG. 5 is a diagram illustrating a configuration example of an AP connection candidate list in the wireless terminal device of FIG. 2;
FIG. 6 is a diagram showing a protocol hierarchy between end and end of the wireless terminal device of FIG. 1 and a communication terminal that is a communication partner of the wireless terminal device.
FIG. 7 is a sequence chart showing an operation up to creation of an AP connection candidate list in FIG. 2;
FIG. 8 is a sequence chart showing an operation up to the start of wireless zone communication according to an embodiment of the present invention.
FIG. 9 is a sequence chart showing a handover process according to one embodiment of the present invention.
FIG. 10 is a flowchart showing a handover process including a rescan process according to one embodiment of the present invention.
[Explanation of symbols]
11,12 wireless base station device
21-24 Wireless terminal device
31 Communication terminal
101,102 Basic service unit
111, 121 wireless transceiver
112,122 Wired transmitting / receiving unit
113,123 Beacon transmission unit
114,124 learning table
115, 125 release timer
211 Wireless transceiver
212 Beacon receiver
213 Frequency switching unit
214 AP connection candidate list
311 Wired transceiver

Claims (8)

A wireless LAN system including a plurality of basic service units in which one wireless base station device and a plurality of wireless terminal devices communicate with each other using a specific frequency,
An AP connection candidate list holding a scan processing result for searching for the wireless base station apparatus connectable for all available frequencies in advance, and the wireless section communication with any wireless base station apparatus when the wireless section communication is disconnected Means for retrieving an AP connection candidate list and determining a wireless base station device to be a new connection destination in the wireless terminal device. 2. The wireless LAN system according to claim 1, wherein the wireless base station device includes a learning table for centrally managing information on the wireless terminal devices that have performed the wireless section communication within a predetermined period. The wireless base station apparatus does not notify the upper layer above the network layer that the wireless section communication has been disconnected / reconnected, and the wireless section and the wired section in the data link layer while maintaining the end-to-end communication. 3. The wireless LAN system according to claim 2, wherein the switching of the communication path of the section is performed based on the learning table. A wireless LAN system including a plurality of basic service units in which one wireless base station device and a plurality of wireless terminal devices communicate with each other using a specific frequency,
A wireless LAN system comprising a learning table in the wireless base station device for centrally managing information on the wireless terminal devices that have performed wireless zone communication within a predetermined period of time. A handover processing method for a wireless LAN system including a plurality of basic service units in which one wireless base station device and a plurality of wireless terminal devices communicate with each other using a specific frequency, The wireless terminal device performs a scan process for searching for the wireless base station device connectable for all available frequencies in advance, holds the result in an AP connection candidate list, and performs a scan with an arbitrary wireless base station device. A handover processing method comprising: searching for the AP connection candidate list when a wireless zone communication is disconnected to determine a wireless base station apparatus to be a new connection destination. 6. The handover processing method according to claim 5, wherein the wireless base station apparatus centrally manages information of the wireless terminal apparatuses with which the wireless section communication has been performed within a predetermined period by using a learning table. The wireless base station apparatus does not notify the upper layer above the network layer that the wireless section communication has been disconnected / reconnected, and the wireless section and the wired section in the data link layer while maintaining the end-to-end communication. 7. The handover processing method according to claim 6, wherein the switching of the communication path of the section is performed based on the learning table. A handover processing method for a wireless LAN system including a plurality of basic service units in which one wireless base station device and a plurality of wireless terminal devices communicate with each other using a specific frequency, A handover processing method, wherein a wireless base station apparatus centrally manages information of the wireless terminal apparatuses with which wireless section communication has been performed within a predetermined period by using a learning table.

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