KR20140097789A - Apparatus and method for effective searching channel for tracking location in Wi-Fi device - Google Patents

Abstract

The purpose of the present invention is to provide a device and a method capable of reducing the number of searches when information is collected to track a location in a wireless network environment by predicting a neighboring AP and selectively searching for a required channel using information on a previously searched AP. In a location tracking system comprising a tag having mobility and periodically collecting information, at least three readers immobilized and collecting information on the tag, and a location detecting engine estimating a location of the tag based on the information collected by the readers, an effective channel searching device comprises: a location detecting unit detecting the current location in the tag; an AP searching unit collecting AP information of a neighboring channel; an AP matching unit comparing the AP information collected by the AP searching unit with AP information having been stored in an AP list table to confirm whether the AP information exists; a weight calculating unit changing the latest update time age of a corresponding AP based on a result of the confirmation of the AP matching unit and setting the changed update time age of the AP as a channel weight of the number of searches for a channel; an AP list processing unit updating the AP list table using results of the execution by the location detecting unit, the AP searching unit, the AP matching unit, and the weight calculating unit; and an AP list storing unit storing the AP list table.

Description

BACKGROUND OF THE INVENTION Field of the Invention [0001] The present invention relates to an apparatus and method for searching a channel for a Wi-Fi device,

Field of the Invention The present invention relates to a location tracking system, and more particularly, to an apparatus and method for reducing the number of channel searches in collecting information for location tracking in a wireless network environment using previous collection information.

 Recently, location-based services (LBS), which require location information, are increasing due to the increase of portable communication devices such as smart phones. Therefore, location recognition technology has become an essential element for providing such services, and such positioning technology is required in many applications such as prevention of lost goods and tracking of cargo.

Conventional location measurement has been studied as a location communication technology. However, a short distance communication technology based positioning system requires a lot of preconditions such as an infrastructure for measuring the position of the object and a position measurement within the infrastructure area.

On the other hand, GPS (Global Positioning System), a positioning system, has been difficult to use in portable devices because reception devices are relatively expensive and power consumption was high in the past. However, recently, Which is suitable for use in a portable device. Since GPS measures the location by receiving radio signals from satellites, it has a great advantage in terms of physical / temporal because it does not need to construct an infrastructure for location measurement and knows its location.

However, since the GPS can not transmit its own location information, a means of transmission is required. Wi-Fi technology is very popular in many portable devices because it is possible to use the network easily by utilizing a wireless network infrastructure composed of a plurality of APs (Access Points) based on IEEE 802.11 in many regions. have.

For this reason, GPS and Wi-Fi combined with location tracking system can be useful in various applications of outdoor environment where wireless network infrastructure is built. Recently, many positioning systems using GPS and WiFi have been researched in accordance with these trends.

The position tracking system is a system for grasping the position of a moving target tag. As shown in FIG. 1, the position tracking of the tag is performed by a tag 10 that periodically collects information with mobility, At least three or more readers AP1 to AP4 for collecting information, and a position measurement engine 20 for estimating the position of the tag 10 with information collected through the readers.

Particularly, in the IEEE 802.11 based location tracking system, a 'station (STA)' and an 'access point (AP)' correspond to the tag 10 and the readers AP1 to AP4. At this time, the tag 10 collects and transmits signal strength, SSID (Service Set IDentifier), MAC (Media Access Control) address, corresponding channel, and the like in the surrounding APs AP1 to AP4, Transmits a beacon that the tag 10 can receive and transmits the data received from the tag 10 to the position measurement engine 20. [

On the other hand, when the tag 10 searches for a channel to search for information, the IEEE 802.11 standard searches for all 11 to 13 channels. This causes unnecessary time and energy to be consumed because the channel searches for a channel in which the AP does not exist . In particular, considering the tags using general purpose devices and the GPS and Wi-Fi with high power consumption, the power problem in the existing position tracking system should be considered.

For example, in an existing location tracking system, a tracking object moves freely in a wireless network environment composed of IEEE 802.11-based APs, so that a handoff occurs when the distance to be communicated to the currently connected AP is exceeded. However, the handoff method provided by the IEEE 802.11 standard searches all channels every handoff. This operation consumes a large amount of power and is therefore not suitable for a system operating with limited power.

SUMMARY OF THE INVENTION Accordingly, the present invention has been made in order to solve the above-mentioned problems, and it is an object of the present invention to provide an apparatus and a method for designing an optimized tag that can be used in a GPS and a position tracking system using Wi- -Fi) apparatus, and an apparatus and method for efficiently searching for a channel.

Another object of the present invention is to estimate a neighboring AP by using information of a previously searched AP and to search for a sufficient number of APs And an apparatus and method for reducing the number of channel searches in collecting information for location tracking in a wireless network environment.

According to an aspect of the present invention, there is provided an apparatus for searching for a location of a Wi-Fi (Wi-Fi) device, comprising: a tag that periodically collects information with mobility; And a position measurement engine for estimating a position of a tag with information collected through at least three or more readers and readers, the position tracking system comprising: a position detector for detecting a current position of the tag in the tag; An AP matching unit for comparing the AP information collected by the AP search unit and the AP information stored in advance in the AP list table to confirm presence or absence of AP information; (Age) of the corresponding AP and sets the latest update time value of the changed AP to the channel weight of the channel search number An AP list processing unit for updating the AP list table using the result information of the position detection unit, the AP search unit, the AP matching unit, and the weight calculation unit; and an AP list storage unit for storing the AP list table .

Preferably, the AP search unit searches for a channel with a probability of a channel weight given based on a channel weight stored in an AP list table that is updated and stored.

Preferably, the AP information includes an SSID indicating AP information, a MAC address indicating a location of the AP, channel information indicating a channel to be used, an RSSI value indicating a strength of a signal, and an Age value indicating a time value .

Preferably, the Age value is a value decreasing by a predetermined time unit, and when the channel connection is established, the Age value is updated to a preset initial value through initialization.

According to an aspect of the present invention, there is provided an effective channel search method for tracking a location of a Wi-Fi device, the method comprising: And a position measurement engine for estimating a position of the tag with information collected through at least two or more readers and readers, the tag being configured to (A) periodically check whether the AP list table is stored in the AP list storage And (B) if the AP list table is not stored as a result of the checking (A), AP information is collected through an adaptive channel search technique for searching all channels, (C) if the AP list table is stored as a result of the checking (A), the probability that an AP among the channels stored in the AP list table is present is high (D) searching for an AP through an adaptive channel search scheme in a weighted state; (E) searching for an AP in the corresponding channel; If the AP is not searched, decreasing the Age value of the corresponding AP from the AP information stored in the AP list table and searching for the AP through the adaptive channel search technique; and (F) Collecting the AP information through an adaptive channel search technique that minimizes the number of searches when the AP is searched in the channel and initializing the Age value of the corresponding AP from the AP information stored in the AP list; And updating the priority based on the Age value and the signal strength of the AP existing in each of the stored channels.

Preferably, the AP list table is a list table in which a list of APs having a high priority in a channel having a high probability of existence of an AP using the previous collection information is stored in advance.

Preferably, the AP list includes an AP signal strength, an SSID, a MAC address required for location measurement, channel information necessary for channel selection, an Age value indicating a time value, and a connection priority.

Preferably, the step (D) collects the AP information as many times as necessary according to the application, performs position estimation, and stops searching for a desired number of APs to reduce unnecessary channel search times.

Preferably, the step (E) further comprises the step of deleting the corresponding AP information from the AP list table when the reduced Age value becomes zero.

Preferably, the Age value of the AP is reduced even if the Age value is not retrieved for a predetermined time.

Preferably, in the step (F), the Age value is initialized to a predetermined initial value and the Age value is changed.

Preferably, the step (G) includes the steps of calculating a sum of Age values of APs existing in respective channels stored in the AP list table, setting a sum of the calculated Age values as channel weights, And updating the priority by applying a signal strength to the channel weight.

Preferably, after step (G), if there is information to be transmitted to the AP found in the tag, attempting channel connection with the AP having the highest priority in the updated AP list table; and Reducing the priority of the corresponding AP in the list and attempting channel connection with the AP in descending order of priority in the AP list; and transmitting the information to the AP connected to the channel when the attempted channel connection is successful, And releasing the connection with the AP when the connection is completed.

As described above, an effective channel searching apparatus and method for tracking a position of a Wi-Fi device according to the present invention has the following effects.

First, when a tag having a limited power resource does not search all 13 channels in a channel search, it searches for only a small number of channels expected to have an AP, thereby reducing power consumption, thereby improving the operation time of the tag.

Second, the tag can operate longer, so the location tracking system can track the location of the object for a longer period of time.

1 is a block diagram showing the configuration of a general position tracking system
2 is a block diagram illustrating a configuration of an effective channel search apparatus for tracking a position of a Wi-Fi device according to an embodiment of the present invention.
3 is a flowchart illustrating an effective channel search method for location tracking of a Wi-Fi device according to an embodiment of the present invention.

Other objects, features and advantages of the present invention will become apparent from the detailed description of the embodiments with reference to the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of an apparatus and method for effective channel search for tracking a position of a Wi-Fi device according to the present invention will be described with reference to the accompanying drawings. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. It is provided to let you know. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely the most preferred embodiments of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents It should be understood that water and variations may be present.

2 is a block diagram illustrating a configuration of an effective channel search apparatus for tracking a location of a Wi-Fi device according to an embodiment of the present invention.

As shown in FIG. 2, the apparatus for reducing the number of channel searches includes a tag 10 for collecting information periodically with mobility as shown in FIG. 1, at least three readers (for example, And a position measurement engine 20 for estimating the position of the tag 10 with the information collected through the readers. The position detection system 20 includes a position detector (not shown) An AP search unit 120 for collecting AP information of peripheral channels, AP information collected in the AP search unit 120 and AP information stored in advance in the AP list table, An AP matching unit 130 for checking the latest update time value of the corresponding AP based on the result of the checking performed by the AP matching unit 130, The weight calculation unit 1 An AP list processing unit 150 for updating the AP list table using the result information of the position detecting unit 110, the AP searching unit 120, the AP matching unit 130, and the weight calculating unit 140; And an AP list storage unit 160 for storing the AP list table. At this time, the AP search unit 120 searches a channel with a probability of a weight given based on the channel weight stored in the updated AP list table. Then, the AP search unit 120 sets a high probability that a channel having a high channel weight is selected.

At this time, the AP information includes an SSID indicating AP information, a MAC address indicating the location of the AP, channel information indicating a channel to be used, an RSSI value indicating the strength of the signal, and an Age value indicating a time value. The Age value is a value decreasing by a predetermined time unit. When the channel connection is established, the Age value is updated to a predetermined initial value (set to '10' in this specification) through initialization. Thus, it is possible to determine the AP status in each channel during the recent time.

The AP list table is data obtained by collecting AP information and converting it into a database and storing it in the AP list storage unit 160 as shown in Table 1 below.

An operation of an effective channel search device for tracking a location of a Wi-Fi device according to the present invention will now be described in detail with reference to the accompanying drawings. Like reference numerals in FIG. 1 or FIG. 2 denote the same members performing the same function.

3 is a flowchart illustrating an effective channel search method for tracking a location of a Wi-Fi device according to an embodiment of the present invention.

Referring to FIG. 3, the tag 10 periodically checks whether the AP list table is stored in the AP list storage unit 160 (S101). If the AP list table is not stored in the AP list storage unit 160, So that AP information is collected through an adaptive channel search technique for searching all channels (S102). In this case, AP information having device information such as AP position, transmission power, and antenna is required not simply for all AP information in the vicinity, but also for location measurement. Also, most APs tend to be distributed over several channels because they do not change the default values set by the manufacturer to prevent channel characteristics and channel interference. Therefore, the method of searching all the channels as described above is also inefficient in terms of time and energy because it searches the channels in which the AP does not exist. Currently, 11 ~ 13 channels are used in Korea. When all the channels are searched in the channel search, about 13 times current is consumed compared to the case where only one channel is searched.

In the present invention, in order to minimize a search frequency by searching a channel having a high possibility that an AP exists in a channel search, a channel having a high probability of existence of an AP is previously stored . At this time, since the AP list table is created using the previous collection information, the AP list table is not created at the time of searching the minimum channel of the tag, so the AP information is collected through the entire channel search first.

Meanwhile, as shown in Table 1, the AP list table includes signal strength, SSID, MAC address, channel information necessary for channel selection, Age value indicating a time value, and connection priority . At this time, the signal intensity is an element for performing position measurement, and more precise positioning can be performed as the signal intensity is more information. The channel information indicates a channel in which APs exist, and this information is basic information for selecting a channel. And we show the probability that APs exist in each channel by using aging technique.

If the AP list table is stored in the AP list storage unit 160, the channel having a high probability of the AP among the channels stored in the AP list table is weighted (S103). At this time, a method of assigning a weight to a channel is given by calculating a channel weight value of the corresponding AP through Equation (1), and a detailed description will be given below.

In step S104, the AP is searched through the adaptive channel search technique in the weighted state. At this time, in order to obtain a large amount of AP information, the number of channel searches increases and power consumption increases accordingly. Conversely, collecting less than a certain number of information results in a trade-off in which precision is lowered. Therefore, AP information is gathered by the required number of APs according to the application, and when the AP is found by the desired number, the channel search is stopped to reduce unnecessary channel search times. In addition, by weighting the APs, searching for APs improves the likelihood that a channel with a higher weight is selected.

At this time, if the AP is not searched in the corresponding channel, the Age value of the corresponding AP is decreased in the AP information stored in the AP list table, and when the decreased Age value becomes zero, the corresponding AP information is deleted from the AP list table (S105). Then, the AP is searched again through the adaptive channel search technique (S104). Note that the Age value of the AP decreases the Age value of the corresponding AP even if it can not be retrieved for a certain period of time.

On the other hand, if the AP is found in the corresponding channel (S104), AP information is collected through an adaptive channel search technique that minimizes the number of searches, and the Age value of the corresponding AP is initialized from the AP information stored in the AP list table ). At this time, the Age value is initialized as a preset initial value, and the Age value is changed. As the Age value is closer to the initial value, it can be confirmed that the corresponding channel has been recently searched. It can be judged.

If AP information collected using the collected information does not exist in the AP list table, then the AP information collected in the AP list table is added. As shown in Equation (1), the sum of Age values of APs existing in each channel stored in the AP list table is obtained, and the values are assigned as channel weights to update priorities (S107). In this case, the updated priority is defined by applying the signal strength to the weight based on the Age value, and the defined priority is necessary for the AP connection for the collected information transmission.

As described above, the channel weights are weighted for each channel using an aging technique after the AP list table is created. That is, the channel weight is calculated by increasing the weight in proportion to the Age value being updated in the AP list table.

On the other hand, when the AP search is not performed in the channel searching step, or when the AP is not searched for a predetermined time, a channel having a channel weight of zero is generated due to the deleted AP. In addition, if the channel is congested due to equipment such as a wireless LAN controller (WLC) that manages a wireless network in a network environment of a medium or small size, the channel can be changed to a channel with less interference. At this time, if the AP does not have the weight of the changed channel, the corresponding channel will not be selected for a predetermined time, and the AP search will not be performed. Therefore, all channels are basically given a certain weight. The channel weight is updated for each channel search operation and the tag 10 then applies the weight of the corresponding channel to the random function to select the channel. Then, the channel selection is repeated until the collected number of APs is sufficient. If all the channels are searched, but the number of acquired APs is not sufficient, the search is stopped.

If there is information to be transmitted to the AP found in the tag 10 (S107), a channel connection with the AP having the highest priority is attempted in the updated AP list table (S109).

At this time, if the attempted channel connection fails (S110), the priority of the corresponding AP is decreased in the AP list (S111), and the channel connection with the AP is attempted in descending order of priority in the AP list (S109).

If the attempted channel connection is successful (S110), information is transmitted to the channel-connected AP (S112). If the channel connection is successful, the connection with the AP is released (S113).

By using the AP list table as described above, it is possible to reduce the number of channel searches performed periodically in information search, thereby effectively reducing power consumption.

While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. It will be apparent to those skilled in the art that various modifications may be made without departing from the scope of the present invention. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

Claims (15)

A position tracking system comprising a tag for periodically collecting information with mobility, at least two readers for collecting information of a tag fixedly, and a position measuring engine for estimating the position of the tag with information collected by the readers, Within the tag
A position detection unit for detecting the current position of the user,
An AP search unit for collecting AP information of a neighboring channel,
An AP matching unit for comparing the AP information collected by the AP search unit and the AP information stored in advance in the AP list table to confirm presence / absence of AP information,
A weight calculation unit for changing the latest update time value (Age) of the corresponding AP based on the result of the checking by the AP matching unit and setting the latest update time value of the changed AP as the channel weight of the channel search number;
An AP list processing unit for updating the AP list table using the execution result information of the position detection unit, the AP search unit, the AP matching unit, and the weight calculation unit;
And an AP list storage unit for storing the AP list table. The apparatus of claim 1, The method according to claim 1,
Wherein the AP search unit searches a channel with a probability of a channel weight given based on a channel weight stored in an AP list table that is updated and stored. . 3. The method of claim 2,
Wherein the AP search unit is configured to have a high probability that a channel having a high weight is selected. 2. The method of claim 1,
An SSI indicating AP information, a MAC address indicating a location of an AP, channel information indicating a channel to be used, an RSSI value indicating a strength of a signal, and an Age value indicating a time value. -Fi) An effective channel search device for tracking the location of a device. 5. The method of claim 4,
Wherein the Age value is a value that is decreased by a predetermined time unit and is updated to a preset initial value through initialization when a channel connection is established. 5. The method of claim 4,
Wherein the AP list table collects AP information and stores the AP information in a database. A position tracking system comprising a tag for periodically collecting information with mobility, at least two readers for collecting information of a tag fixedly, and a position measuring engine for estimating the position of the tag with information collected by the readers, The tag
(A) checking whether the AP list table is periodically stored in the AP list storing section,
(B) if the AP list table is not stored as a result of the checking (A), collecting the AP information through an adaptive channel search technique for searching all channels as a whole, and adding AP information collected in the AP list table Wow,
(C) weighting a channel having a high probability that an AP among the channels stored in the AP list table is stored if the AP list table is stored as a result of the checking (A); and
(D) searching for an AP through the adaptive channel search scheme in the weighted state,
(E) If the AP does not search in the corresponding channel as a result of the searching in the step (D), the AG value of the corresponding AP is decreased in the AP information stored in the AP list table, , ≪ / RTI &
(F) collecting AP information through an adaptive channel search technique that minimizes a search frequency when an AP is searched for in a corresponding channel as a result of the searching in the step (D), extracting, from the AP information stored in the AP list table, Initializing the value,
And updating the priority based on the Age value and the signal strength of an AP existing in each channel stored in the (G) AP list table. The Wi- Effective channel search method. 8. The method of claim 7,
Wherein the AP list table is a list table in which a list of APs having a high priority is previously stored in a channel having a high probability of existence of an AP using previous collection information. Way. 9. The method of claim 8,
The AP list table includes a signal strength, an SSID, a MAC address required for location measurement, channel information necessary for channel selection, an Age value indicating a time value, and a connection priority. An effective channel search method for location tracking of a device. 8. The method of claim 7,
Wherein the step (D) collects the AP information as many times as necessary according to the application, estimates the position, stops the channel search if the AP is found by a desired number, and reduces the number of unnecessary channel searches. An effective channel search method for location tracking. 8. The method of claim 7,
Wherein the step (E) further comprises the step of deleting the corresponding AP information from the AP list table when the reduced Age value becomes zero. Way. 12. The method of claim 11,
Wherein the Age value of the AP decreases the Age value of the AP even if the Age value of the AP is not retrieved for a predetermined period of time. 8. The method of claim 7,
Wherein the Age value is changed to a preset initial value in the initialization of the Age value in the step (F). 8. The method of claim 7, wherein step (G)
Calculating a sum of Age values of APs existing in each channel stored in the AP list table;
Setting a sum of the calculated Age values as a channel weight;
And updating the priority by applying a signal strength to the set channel weight. The method of claim 1, 8. The method of claim 7, wherein after step (G)
Attempting to establish a channel connection with an AP having the highest priority in the updated AP list table when there is information to be transmitted to the AP found in the tag,
If the attempted channel connection fails, decreasing the priority of the corresponding AP in the AP list and attempting channel connection with the AP in descending order of priority in the AP list;
And transmitting the information to the AP connected to the channel when the attempted channel connection is successful, and releasing the connection with the AP when the transmission is completed. How to search for channels.

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