KR100725398B1 - Apparatus and method for scanning access point and channel handover - Google Patents

Abstract

An apparatus and method for access point scan and channel handover are provided. The access point scan and channel handover device performs a handover by changing the register and channel for registering a channel when the access point exists in the scan unit for scanning the presence or absence of the access point in the communication channel between the terminal and the access point. Contains wealth.

Access point, AP, handover

Description

Apparatus and method for scanning access point and channel handover}

1 is a configuration diagram according to a communication radius between a conventional terminal and an access point.

2 is a detailed block diagram of an apparatus for handing over an access point scan and a channel according to an embodiment of the present invention.

3 is a block diagram of an apparatus for handing over an access point scan and a channel according to an embodiment of the present invention.

4 is a flowchart of channel scan and registration according to an embodiment of the present invention.

5 illustrates a channel scan according to an embodiment of the present invention.

6 is a configuration diagram of an access point and a terminal device according to an embodiment of the present invention.

7 illustrates an access point scan and a channel scan for handover according to an embodiment of the present invention.

<Explanation of symbols on main parts of the drawings>

Access point 1: 10

Channel scan module: 300

Channel control module: 301

The present invention relates to an apparatus and a method for access point scanning and handover of a channel. More particularly, the present invention relates to a method for scanning an access point existing in a channel according to a scan time interval, and when the device is out of the communication radius between the terminal and the access point. An apparatus and method for performing an access point scan and handover of a channel that proceed with over.

Recently, wireless LAN is developed and used with the development of high speed communication speed, mobile computing technology and mobile terminal. Since wireless LAN uses electromagnetic waves from access point (AP) equipment to terminal equipment, it is possible to construct a network within a relatively quick time compared to wired LAN. You can also communicate on-the-go with your laptop and PC card, instead of staying on a fixed desktop environment.

On the other hand, the access point refers to a network access control device that can control the connection to the wireless network to the station. The access point may be described in terms of an access point as defined in IEEE 802.11, which is preferably a standard for WLAN.

In addition, IEEE 802.11 WLAN is equipped with an access point that converts a frame of an 802.11 network into another frame for transmission to another network, that is, an access point that performs wireless and wired bridging functions and a WLAN device that can interface with the wireless network. And a network device capable of performing communication using a wireless medium such as a laptop, a cellular phone, a PDA, a digital TV, a set-top box, or the like. In general, the IEEE 802.11 protocol is currently standardized in the medium access control (MAC) and the physical layer, and the network device may be described as a network device defined in IEEE 802.11, which is preferably a standard for WLAN. .

1 is a configuration diagram according to a communication radius between a conventional terminal and an access point.

In an IEEE 802.11 infrastructure wireless network, the communication radius of a mobile terminal is limited to within a certain distance of the access point radius. When the mobile terminal leaves the area of the access point radius during communication, the communication of the terminal is interrupted, and the terminal proceeds with scanning of the adjacent access point.

In more detail, an access point scan, authentication, and association process is performed. The access point scanning process moves each channel and transmits a probe request packet, and waits for a predetermined time to receive a probe response packet corresponding thereto. When a probe response is received on a specific channel, it is determined that an access point exists and is connected to the access point through an obsession and association process.

However, since the access point is scanned after communication between the access point and the terminal is lost, the service using the network is stopped.

Thus, when the terminal communicating with the access point moves out of the communication radius of the access point to a new access point area, there is a need for an efficient access point scan and handover without disruption of communication.

An object of the present invention is to provide an apparatus and method for access point scan and channel handover.

The objects of the present invention are not limited to the above-mentioned objects, and other objects that are not mentioned will be clearly understood by those skilled in the art from the following description.

In order to achieve the above object, the access point scan and handover apparatus of the channel according to an embodiment of the present invention, the access point is present in the scan unit and the channel for scanning the presence of the access point in the communication channel between the terminal and the access point In this case, the terminal may include a register that registers a channel and a change unit that performs handover by changing a channel.

According to an embodiment of the present invention, an access point scan and channel handover method includes scanning a presence of an access point in a communication channel between a terminal and an access point, and registering a channel when an access point exists in the channel. It includes the step of changing the handover, the scan is characterized in that the first scan for the presence of the access point for all channels, and if there is an access point is characterized in registering the channel according to the threshold number of terminals.

Specific details of other embodiments are included in the detailed description and the drawings.

Advantages and features of the present invention, and methods of accomplishing the same will be apparent with reference to the embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below, but can be implemented in various different forms, only the embodiments are to make the disclosure of the present invention complete, and common knowledge in the art to which the present invention belongs It is provided to fully inform the person having the scope of the invention, which is defined only by the scope of the claims. Like reference numerals refer to like elements throughout.

Prior to describing the embodiments of the present invention, key terms will be described.

<Key term>

Service Set Identifier (SSID): A 32-byte unique identifier for each header of a packet transmitted over a wireless LAN. It is used as a password when wireless devices access the Basic Service Set (BSS). do. Since the service set identifier distinguishes one WLAN from another WLAN, an access point or a wireless device to access a specific WLAN must use the same service set identifier. No device that does not know the unique service set identifier of a particular basic service set can connect to that basic service set.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 is a detailed configuration diagram of an access point search and channel handover apparatus according to an embodiment of the present invention.

A terminal using an 802.11 infrastructure network includes a network application 200, an OS kernel network stack 210, a first scan module 220, a network interface card driver 230, and a network interface card 240.

The network application 200 is an application using a network.

The OS kernel network stack 210 is a network protocol stack of an operating system.

Priority scan module 220 includes a priority set (P-Set) 222, a priority set manager 224, a channel scanner 226, and an access point. Handover engine 228.

First, the scan module 220 may operate through a mutual interface with the network interface card driver 230. That is, it scans nearby access points through the interface with the network interface card driver 230 and is responsible for handover of the access points.

The preferential set 222 is a set of channels within a maximum scanning set size (MSS) in order of high signal to noise ratio (SNR) according to a predetermined channel in which an access point exists. The preferential set 222 is sorted and continuously updated according to the signal-to-noise ratio, and if it is out of the threshold number of ranks, a channel having a weak signal-to-noise ratio may be preferentially deleted. The threshold number may be set to a value greater than or equal to 1 or less than the number of available channel sets (CSs) of the IEEE 802.11b infrastructure, and may preferably be set to 3 as a default value. In addition, the present invention can be applied to a network using an infrastructure mode in the same manner as IEEE 802.11 in addition to the IEEE 802.11b.

The preferred set 222 includes a channel field, a service set identifier field, a signal status field and a last update time field as shown in Table 1.

channel Service set identifier Signal status Last update time

The channel field has a channel number value.

The Service Set Identifier (SSID) field is preferably a service set identifier used in an 802.11 network.

The signal status field is a numerical value of the signal to noise ratio.

The last update time is the update time of the last signal to noise ratio of the channel where the access point is present.

On the other hand, the signal-to-noise ratio is a signal-to-noise ratio at the time of packet reception and can be calculated by measuring the received signal strength indication (RSSI) of the packet measured when the packet is received. The farther the terminal is from the access point, the weaker the signal-to-noise ratio.

The channel is preferably a signal band used by the access point in an infrastructure mode of a wireless network such as 802.11, and the terminal may be set to the same channel as the channel used by the access point in order to communicate through a specific access point.

The preferred set manager 224 can manage the registration, deletion and update of the preferred set 222 according to the signal-to-noise ratio.

The channel scanner 226 may periodically scan nearby access points according to the scan time interval 500. If it is determined through the channel scanner 226 that the access point is present, the channel is sorted according to the signal-to-noise ratio, and the channel is registered in the preferential set 222.

The access point handover engine 228 may determine whether a handover is necessary because the signal-to-noise ratio of the entry of the set 222 is preferred over the signal-to-noise ratio of the access point of the channel currently being used.

The network interface card driver 230 is a device driver of the network interface card 240.

The network interface card (NIC) 240 preferably means a network adapter card or a wireless LAN card, and serves as a medium for connecting a cable to a computer when communicating between computers on a network. can do.

3 is a block diagram of an apparatus for handovering an access point search and a channel according to an embodiment of the present invention.

The access point scan and channel handover apparatus includes a channel scan module 300 and a channel control module 301.

The channel scan module 300 may scan, register, update, and delete a channel.

The channel scan module 300 includes a scan unit 310, a register 320, and a manager 330.

The scan unit 310 may scan the presence or absence of an access point in a predetermined channel.

The registration unit 320 may register the channel in the preferential set 222 when the access point exists in the predetermined channel.

The manager 330 may delete the predetermined channel according to the update of the signal-to-noise ratio of the registered channel and the signal-to-noise ratio.

The channel control module 301 may control channel switching and handover.

The channel control module 301 includes a switching unit 340 and a changing unit 350.

The switching unit 340 may switch the channel of the terminal to a channel corresponding to the set threshold number of entries.

If it is determined that the communication state deteriorates and the handover is necessary at some time out of the communication radius with the access point with which the terminal is communicating, the changer 350 selects a channel having the best signal-to-noise ratio among the entries of the preferential set 222. First of all, the handover may be performed by selecting.

4 is a flowchart of channel scan and registration according to an embodiment of the present invention.

The sequential set 221 sequentially scans the entire presence or absence of access points of all channels through the scan unit 310 (S401). The preferential set 222 registers the channel through the register 320 as an entry within a threshold number range in the order of the high value of the signal-to-noise ratio of the channel in which the access point exists through the sequential set scan 221a process. . The scan may preferably be an active scan. After the initial full scan 700 through the sequential set scan 221a, the processes of the sequential set scan 221a and the preferential set scan 222a are alternately performed 800. Desirably, the first full scan 700 may be only once.

After the initial full scan 700, the subsequent process of FIG. 4 will be described in conjunction with FIG. 5.

5 illustrates a channel scan according to an embodiment of the present invention.

As shown in FIG. 5A, for example, when the threshold number of entries is set to 3, after the full scan of the initial step 700, the channel of the terminal is changed to the first entry of the entry of the sequential set 221 ( That is, switching to the channel corresponding to ss0 through the switching unit 340 (S411).

5B shows a scan of the channel corresponding to the first entry ss0.

The terminal transmits a probe request to the access point (S421).

After transmitting the probe request, the terminal waits for a predetermined time and waits for reception of a probe response of the access point (S431).

If the access point exists in the corresponding channel, the probe response of the access point is received, and it is determined whether the corresponding channel exists in the entry of the preferential set 222 (S441).

If it already exists in the preferential set 222, the signal-to-noise ratio of the channel of the preferential set 222 is updated through the management unit 330 (S451).

If it does not exist, the corresponding channel is registered in the entry of the priority set 222 through the register 320 (S461). At the time of registration, if there is already a predetermined number of channels (i.e., set of three channels) in the priority set 222, the signal-to-noise ratio measured in that channel is compared to the signal-to-signal of the entry in the priority set 222. Compare with the noise ratio. If the signal-to-noise ratio of the corresponding channel is larger than the entry of the preferential set 222, the channel having the smallest signal-to-noise ratio among the entries of the preferential set 222 is deleted through the management unit 330, and the corresponding channel is deleted from the preferential set 222. The new entry is registered through the register 320.

In a next step, the channel of the terminal is switched to the channel corresponding to the second entry (that is, ss1) of the sequential set 221 through the switching unit 340 (S411). Subsequent steps are the same as the scanning and registering process of the channel (process of FIG. 4).

When the sequential set scan 221a is terminated until the third entry (ie, ss2), data communication is performed with the access point 10 in use, and when the time is determined according to the time interval 500 of the scan, the preferred set 222 Is changed to the channel corresponding to the first entry (ie, ps0) through the switching unit 340, and the scanning unit 310 performs a priority set scan 222a process by the set threshold number of entries ps0, ps1, and ps2. Proceeds through (S411). Subsequent steps are the same as the scanning and registering process of the channel corresponding to each entry of the sequential set 221 (process of FIG. 4).

The scan time interval 500 is the data communication time before the sequential set scan 221a ends and the preferential set scan 222a starts. In addition, the time interval 500 of the scan may be set according to a network environment (for example, the number of terminal nodes and the moving speed of the terminal), and may be preferably set to 1000 milliseconds as a default value.

The time required to perform the scan operation is limited to within the retransmission limit time of the packet of the wireless terminal, thereby minimizing the influence on packet transmission and reception through the access point 10 that is already in use. In addition, in the link layer (LLC) of a wireless LAN, a response packet for packet transmission is received when a packet is transmitted between links. If the packet is not received within a certain time, the packet is determined to have not been delivered normally, and then retransmitted. . There is a limit on the number of retransmissions. The limit of the number of retransmissions may be defined as a retransmission limit time.

6 is a configuration diagram of an access point and a terminal device according to an embodiment of the present invention.

When the mobile node communicating with the access point 1 (10) using the channel 1 moves in the direction of the access point 6 (10b) using the channel 6 and the access point 11 (10c) using the channel 11, the terminal is shown in FIG. Scan the access points in the same order.

7 illustrates a channel scan for access point search and handover according to an embodiment of the present invention.

After the initial full scan 700 through the sequential set scan 221a, the processes of the sequential set scan 221a and the preferential set scan 222a are alternately performed 800. Desirably, the first full scan 700 may be only once.

When the terminal starts communication at time T, the sequential set scan 221a is preferably performed through the scan unit 310 for the first one time all channels. In T through T + 3d, the access point 6 10b and the access point 11 10c adjacent to the first set 222 are registered through the register 320 through the full channel scan process. Accordingly, channels {1, 6, 11} are registered in the preferential set 222 including the channel of the access point 1 (10) currently in use. Since the threshold number is set to 3, for example, it is limited to the above three entries.

In the next step, the sequential set scan 221a and the preferential set scan 222a are repeatedly performed through the scan unit 310.

In T + 4d 222b and T + 6d 222c, the preferential set scan 222a proceeds as it is because there are no changes in the registered channels {1, 6, 11} of the preferential set 222, and the sequential set scan ( 221a proceeds sequentially for channels excluding entries in the preferential set 222. A channel scan corresponding to each entry is performed on the {2, 3, 4} channel in the T + 5d 221b and the {5, 7, 8} channel in the T + 7d 221c. On the other hand, the scanning and registration process of each channel corresponding to the entries (ss0, ss1, ss2) of the sequential set 221 and the entries (ps0, ps1, ps2) of the preferential set 222 follow the steps of FIG. .

d denotes a time interval 500 of scanning, and during the remaining periods except for each scanning process, the terminal performs data communication using the access point 1 (10) that is being used.

If the terminal continues to move toward the access point 6 (10b) and the communication state of the access point 1 (10) deteriorates at some point and it is determined that handover is necessary through the access point handover engine 228, the preferred set 222 First, the channel having the best signal-to-noise ratio among the entries of the) may be preferentially selected and handover may be performed through the changer 350. Therefore, in the IEEE 802.11 infrastructure network, a seamless communication service is possible when a mobile terminal moves between access points beyond a communication radius of one access point.

Although the embodiments of the present invention have been described above with reference to the accompanying drawings, those skilled in the art to which the present invention pertains may implement the present invention in other specific forms without changing the technical spirit or essential features thereof. I can understand that. Therefore, it should be understood that the embodiments described above are exemplary in all respects and not restrictive.

According to the apparatus and method for access point scan and channel handover of the present invention as described above, when the terminal communicating with the access point moves out of the communication radius of the access point to a new access point area, There is an advantage in that the access point can be scanned and handover can be performed.

Claims (5)

A scanning unit scanning the presence or absence of the access point in a communication channel between a terminal and an access point; A register that registers the channel when the access point exists in the channel; A management unit for updating the signal-to-noise ratio of the registered channel or deleting the registered channel according to the signal-to-noise ratio; A switching unit for switching a channel of the terminal to the channel corresponding to a threshold number of entries of the terminal; And And a changer for changing and handing over the channel. The method of claim 1, And the scan unit scans a channel corresponding to a threshold number of entries of the terminal according to a scan time interval. The method of claim 2, And the scan unit scans the presence or absence of the access point for all the first channels, and registers the channel according to the threshold number when the access point exists. Scanning the presence or absence of the access point in a communication channel between a terminal and an access point; Registering the channel if the access point exists in the channel; Updating the signal-to-noise ratio of the registered channel or deleting the registered channel according to the signal-to-noise ratio; Switching a channel of the terminal to the channel corresponding to a threshold number of entries of the terminal; And And changing the channel to handover the access point scan and channel handover method. The method of claim 4, wherein The scanning may include scanning a channel corresponding to a threshold number of entries of the terminal according to a scan time interval.

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