KR101341990B1 - Apparatus and method for selecting of access point - Google Patents

Abstract

Receive a beacon message from multiple access points through scanning, check the information of the use frequency for each access point based on the beacon message, classify the plurality of access points based on the channel according to the identified use frequency, access point For each of the access points, an estimated value of the signal-to-interference noise ratio is calculated based on the value obtained by dividing the signal strength by the interference noise strength of the corresponding channel. Select the access point to connect.

Description

APAPATUS AND METHOD FOR SELECTING OF ACCESS POINT}

The present invention relates to an apparatus and method for selecting an access point (AP) suitable for a wireless communication environment of a user terminal.

With the development of wireless communication technology, the demand of mobile terminals such as smart phones is increasing, and from the viewpoint of these mobile terminals, which base station should be used when connecting with the network backbone of the network? Judgment is very important. In this case, it is possible to estimate a data rate of a certain level or more for each base station recognized on the network, and to select a base station that satisfies the demand of the user who uses the mobile terminal and the service request quality of the mobile terminal itself. It is a top priority.

In 4G Long Term Evolution (LTE) network, which is being actively developed, information such as RSRP (Reference Signal Received Power), RSRQ (Reference Signal Received Quality), Resource Block (Resource Block), etc. before the association procedure between the UE and the eNode B You can indirectly analyze the data rates that the network can support.

In contrast, Wi-Fi networks do not currently have a way to infer near-real network quality, such as LTE.

Instead, in a Wi-Fi network, an access point (AP) broadcasts a beacon message at every beacon interval and receives the beacon message (ie, mobile). Device) checks received signal strength indicator (RSSI) information that can be obtained through reception of a beacon message, and provides a corresponding AP quality. Most Wi-Fi user terminals output a larger icon according to the signal strength as the RSSI value increases, allowing the user to select a specific AP.

The criterion of RSSI reflects AP quality in terms of noise. For reference, noise is caused by natural phenomena, and the plurality of APs detected by the user terminal due to the wide range of natural phenomena has almost the same noise figure. On the other hand, interference refers to the overlapping density of other signals included in the received signal, and the magnitude of the interference signal varies depending on the distance between the transmitting transmitter and the receiver. Because it depends on the channel number, it is difficult for RSSI to accurately reflect the quality of the AP in terms of interference. That is, in case of selecting AP by comparing RSSI information among beacon information of each AP at the end of wireless communication, problems such as interference caused by channel sharing or network quality deterioration are not reflected in RSSI, and thus the AP having excellent transmission quality There is a problem that is difficult to determine. In order to properly reflect this, a comparison of relative transmission rates of each AP should be possible before the AP connection.

On the other hand, the value of Signal to Interference Noise Ratio (SINR) indicates how much of the signal received from the receiver (receiver) caused by noise and interference. For reference, the interference does not occur naturally but is a value generated by interference of other signals in addition to the signal transmitted from the transmitter, and the higher the variable of the interference, the smaller the SINR value. At this time, the noise in the SINR can be assumed to be almost zero, so that the SINR can be regarded as a substantially SIR (Signal to Interference Ratio). The SIR value represents the quality of the signal value received from the transmitting side. That is, if the SIR value can be accurately inferred, it can be determined whether the terminal can use the AP based on the SINR value.

However, there are various problems in implementing a technology for extracting an interference signal from the received signal itself in a user terminal. As a representative problem among them, the latest terminals such as smart phones and tablet PCs are getting smaller in size for user convenience, design, and price competition. That is, it is not preferable in terms of cost and technical aspects to equip the miniaturized user terminal with a function such as a spectrum analyzer to improve network quality. In order to successfully infer the SINR in the user terminal except for the spectrum analyzer, the quality of the network can be inferred as the SINR based on the result of the continuous packet transmission after the user terminal makes a connection with a specific AP. have. However, in this manner, it is not possible to predict the transmission quality of each AP before the network connection, that is, before the authentication (Authentication) process to select a suitable AP among a plurality of APs.

In addition, the beacon message contains supported rates of supported APs, but it does not directly reflect the current transmission quality on the network, but is based on the maximum transmit rate depending on which transmission scheme the AP supports. Information about this. Therefore, the highest rate (ie, transmission amount) in the information of the transmission rate supported by the AP cannot be used unconditionally as a condition for determining the data transmission rate of the AP.

On the other hand, as related to the technology of the present invention, Korean Patent Laid-Open Publication No. 2010-0115991 (Handover method considering interference in a wireless LAN system), the communication terminal in the wireless LAN system to receive the received signal strength of the neighboring AP By measuring the respective signal-to-interference ratios for candidate APs whose received signal strength is greater than or equal to a predetermined reference value, the interference margin of each candidate AP is calculated, and the interference margin is subtracted from the received signal strength of the candidate APs. A method of selecting an AP for handover is disclosed.

The present invention is to solve the above-mentioned problems of the prior art, an access point having a transmission quality relatively superior to other access points in terms of interference and noise by using a beacon message broadcast by the access point in a wireless communication network environment It is intended to provide an apparatus and method for selecting a.

According to an aspect of the present invention, there is provided an apparatus for selecting an access point, including: a scanning unit configured to receive a beacon message from a plurality of access points; A channel classifying unit classifying the plurality of access points by channels by checking information of a use frequency included in the beacon message for each access point; Signal to Interference-plus-Noise Ratio based on the signal strength of one access point divided by the interference and noise strength of the corresponding channel to which the access point belongs. A selection criterion calculator which calculates an estimated value of? And an access point selector configured to select an access point to be connected among the plurality of access points based on the estimated value of the signal-to-interference noise ratio calculated for each access point. In this case, the interference noise intensity is a sum of interference strength and noise strength of the corresponding channel.

In addition, the access point selection method through the access point (Access Point) selection apparatus according to another aspect of the present invention, (a) receiving a beacon message (beacon massage) from a plurality of access points through scanning; (b) identifying information of a use frequency for each access point based on the beacon message, and classifying the plurality of access points based on a channel according to the identified use frequency; (c) The ratio of the Signal to Interference-plus-Noise Ratio based on the value obtained by dividing the signal strength of each access point by the interference and noise strength of the corresponding channel to which it belongs. Calculating an estimated value; And (d) selecting an access point to be connected among the plurality of access points based on the estimated value of the signal-to-interference noise ratio calculated for each access point. In this case, the interference noise strength is the sum of interference strength and noise strength of the corresponding channel, and the signal strength is the received signal strength detected when the beacon message is received for each access point. Indicator) is set based on the information.

According to any one of the above-described problem solving means of the present invention, by using the estimated value of the relative SINR with the other AP existing in the same channel as the criterion of AP selection, interference and interference for each channel with respect to the APs recognized by the user terminal The optimal AP can be selected considering the noise strength.

And, according to any one of the problem solving means of the present invention, the user terminal calculates the estimated value of SINR for each AP based on the beacon information obtained in the AP scanning procedure, so that the user terminal performs a direct authentication and association procedure with a specific AP The AP selection condition can be checked before performing the AP selection.

1 is a diagram illustrating a network to which the present invention is applied.
2 is a block diagram illustrating a configuration of an apparatus for selecting an access point according to an embodiment of the present invention.
3 is an example for describing a frequency band used in a Wi-Fi environment according to an embodiment of the present invention.
4 is a flowchart illustrating a method of selecting an access point according to an embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, which will be readily apparent to those skilled in the art. The present invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. In order to clearly illustrate the present invention, parts not related to the description are omitted, and similar parts are denoted by like reference characters throughout the specification.

Throughout the specification, when a part is referred to as being "connected" to another part, it includes not only "directly connected" but also "electrically connected" with another part in between . Also, when an element is referred to as "comprising ", it means that it can include other elements as well, without departing from the other elements unless specifically stated otherwise.

1 is a diagram illustrating a network to which the present invention is applied.

As illustrated in FIG. 1, a plurality of access points (APs) (referred to as 'first to nth access points' in FIG. 1) exist on a network to which the present invention is applied, and a user terminal (which is intended to access a network) ( 10) selects any one of the plurality of AP to perform a connection (connection) procedure.

For reference, a network to which the present invention is applied may be a wireless LAN (LAN) network such as Wi-Fi, and the user terminal 10 is a wireless communication terminal, which is a desktop computer, a laptop computer, a laptop computer, and a personal portable device. It includes a terminal. In this case, the portable terminal is a wireless communication device that guarantees portability and mobility, and includes a personal communication system (PCS), a global system for mobile communications (GSM), a personal digital cellular (PDC), a personal digital assistant (PDA), and a code division (CDMA). Multiple Access (2000), W-Code Division Multiple Access (W-CDMA), Wireless Broadband Internet (WBRO) terminal, and all kinds of handheld based wireless communication devices such as smart phones.

Meanwhile, the apparatus 100 for selecting an access point according to an embodiment of the present invention to be described below with reference to FIG. 2 may be included in the user terminal 10 or the user terminal 10 in one configuration.

In such a network environment, the APs transmit beacon messages to the user terminal 10 in a broadcasting manner. The beacon message includes a plurality of beacon information, and the user terminal 10 may manage a beacon frame composed of beacon information obtained from the beacon message for each AP.

For example, as shown in FIG. 1, a beacon frame obtained using a beacon message received from each AP may include a timestamp, a beacon interval, capability information, and a service set. Service Set Identifier (SSID), basic service set identifier (BSSID), Signal Level (RSSI in dBm), Supported Rates, Various Parameter Set (FH Parameter Set, And beacon information such as a DS Parameter Set, a CF Parameter Set, an IBSS Parameter Set, and a Traffic Indication Map (TIM).

Specifically, the header of the beacon frame may include a 'BSSID', 'BSSID' is a MAC address that proves the membership of the AP or the existence of the AP itself.

The body of the beacon frame includes' Timestamp ',' Beacon Interval ',' Capability Information ',' SSID ',' Supported Rates', 'FH Parameter Set', 'DS Parameter Set', 'CF Parameter Set', ' IBSS Parameter Set ', and' TIM 'may be included. In this case, 'Timestamp' is information for synchronizing a local clock with a neighboring terminal by synchronizing a local clock of a terminal receiving beacon information, and 'Beacon Interval' is information of a period in which the AP provides beacon information. In other words, 'Capability Information' is various kinds of security information required for the authentication process required by the network to be accessed. For reference, 'Capability Information' may include information on authentication schemes such as WEP, WPA / WPA2. The 'SSID' is naming information representing the AP in terms of 'user friendly' instead of 'BSSID' in order for the user of the user terminal to easily distinguish the AP. In addition, 'Supported Rates' is information on a transmission quality that an AP can provide, and means the maximum data transmission rate possible between the AP and a user terminal after the connection procedure. Also, 'Parameter Sets' (' FH Parameter Set ',' DS Parameter Set ',' CF Parameter Set ',' IBSS Parameter Set ')' is a set of various variables for the data transmission technique of the AP. For reference, in the Wi-Fi environment, 'Parameter Sets' for 2.4 GHz band is a set of variables for Direct Sequence Spread Spectrum (DSSS), and 'Parameter Sets' for 5 GHz band are orthogonal frequency division. It is a set of variables for (OFDM, Orthogonal Frequency Division Multiplexing). In addition, 'Parameter Sets' includes frequency information on the frequency band (Hz) used by the AP. In this case, the frequency information may be center frequency information, and the center frequency information may be used to determine which frequency band channel the AP is currently using.

The physical layer of the beacon frame may include a signal level (RSSI in dBm), and the signal level (RSSI in dBm) may be measured by a user terminal when receiving a beacon message from an AP. As the signal magnitude, an embodiment of the present invention may use information of the received signal strength indicator (RSSI) as the signal magnitude. For reference, RSSI may be expressed in dBm.

Hereinafter, the configuration and operation of the apparatus 100 for selecting an access point according to an embodiment of the present invention will be described in detail with reference to FIGS. 2 and 3.

2 is a block diagram illustrating a configuration of an apparatus for selecting an access point according to an embodiment of the present invention.

3 is an example for describing a frequency band used in a Wi-Fi environment according to an embodiment of the present invention.

First, as shown in FIG. 2, the apparatus 100 for selecting an access point according to an embodiment of the present invention includes a scanning unit 110, a channel classifying unit 120, a selection criterion calculating unit 130, and an access point. It is configured to include a selection unit 140.

The scanning unit 110 receives the beacon message (beacon massage) being broadcast from each AP to scan the neighboring AP (scanning). For reference, the scanning unit 110 may obtain beacon information from beacon messages of a plurality of APs, configure a beacon frame, and store and manage each AP.

In this case, the scanning unit 110 performs a scanning procedure prior to an authentication and association procedure with a specific AP when the connection procedure is performed. In addition, the scanning unit 110 scans when the access point selection device 100 first accesses the current network, or when the connection with the previously connected AP is terminated, or in any one of a preset period (or time point). Can be performed.

The channel classifier 120 obtains frequency information included in the beacon frame for each AP from the scanning unit 110, and classifies a plurality of APs by channel based on the obtained frequency information. For reference, as described with reference to FIG. 1, the beacon frame includes center frequency information used by the AP.

Specifically, the channel classifier 120 checks information of each center frequency used by the plurality of APs scanned by the scanning unit 110 and checks the number of the channel including the center frequency. The channel classifier 110 classifies APs by channels by classifying APs included in the same channel. For reference, the number of the channel is previously matched for each frequency band (or center frequency). For example, FIG. 3 shows that 14 channels exist in the 2.4 GHz band of Wi-Fi.

2 again, the selection criterion calculator 130 calculates an estimated value of a Signal to Interference-plus-Noise Ratio (SINR) for each AP. In this case, the selection criterion calculator 130 is a value obtained by dividing a signal strength of one AP by an interference and noise strength of a channel to which the AP belongs (hereinafter, referred to as a corresponding channel). Based on this, an estimated value of SINR is calculated. For reference, the interference noise strength is a sum of interference strength and naturally occurring noise strength according to APs present in a corresponding channel.

However, as in the exemplary embodiment of the present invention, it is difficult to calculate an accurate SINR value in a state where only a scanning procedure is performed before performing an authentication and association procedure with a specific AP. That is, the correct SINR value can be calculated only after the user terminal (ie, the access point selecting device) actually transmits and receives data while connected to a specific AP through authentication and association procedures. Therefore, the selection criterion calculator 130 according to an embodiment of the present invention calculates an estimated value of SINR by applying the received signal strength (RSSI) value detected through the beacon message for each AP as the signal strength.

At this time, the selection criterion calculator 130 obtains information of the received signal strength (RSSI) detected when receiving the beacon message for each AP through the scanning unit 110, and applies the RSSI for each AP as the signal strength of the AP. In addition, the selection criterion calculator 130 sets the interference noise strength by applying the sum of the signal strengths of other APs existing in the same channel as the interference strength and applying a preset noise strength.

In detail, when a plurality of APs are included in one channel, the selection criterion calculator 130 sets the noise strength to zero by assuming that the strength of noise applied to the APs included in the same channel is the same. The estimated value of SINR can be calculated.

That is, the selection criterion calculator 130 calculates an estimated value of the SINR using Equation 1 below.

&Quot; (1) "

)로 나눈 값이다. 참고로, 수학식 1에서 간섭세기는 동일 채널 내 나머지 AP의 RSSI의 합이다.Estimate of the SINR (SINR _estimate) interference strength is the received signal strength (RSSI _APcurrent) of the AP in the equation (1) (

Divided by). For reference, in Equation 1, the interference strength is the sum of RSSIs of the remaining APs in the same channel.

In this case, the selection criterion calculator 130 may check the information on the transmission scheme from the beacon message for each AP in the same channel, and set the noise strength to zero when the checked transmission scheme is a preset transmission scheme. . For example, in DSDS of Wi-Fi, since noise hardly occurs due to transmission characteristics, the noise strength may be assumed to be close to zero in Equation 1.

In addition, when one AP is included in one channel, the selection criterion calculator 130 calculates an estimated value of SINR by applying a predetermined minimum noise intensity as a noise intensity and applying an interference intensity as zero (0). can do. In this case, the minimum noise strength may be set to the minimum signal strength that can be measured by the user terminal (ie, the access point selection device).

On the other hand, it has been described above that the selection criterion calculator 130 calculates an estimated value of SINR by applying a relative interference strength with respect to at least one AP included in one channel with another AP. However, the selection criterion calculator 130 according to another embodiment of the present invention divides the signal strength of one AP by the interference noise strength of the corresponding channel to which the AP belongs and the interference channel interference strength of the adjacent channel. The value may be calculated as an estimated value of SINR. In this case, the selection criterion calculator 130 may give a higher weight to the interference noise intensity of the channel than the interference noise intensity of the adjacent channel. For reference, the selection criterion calculator 130 may apply the sum of the received signal strengths of all APs included in the adjacent channel as the interference strength when calculating the interference noise strength of the adjacent channel. In addition, the adjacent channel may include at least one channel of the upper and lower frequency band of the channel.

The access point selector 140 selects an AP to connect among the plurality of APs based on the estimated value of the SINR calculated for each AP through the selection criterion calculator 130.

Specifically, the access point selector 140 determines the priority of the AP for each channel based on the magnitude of the estimated value of the SINR of each AP, and compares the magnitudes of the estimated values of the SINR of the APs having the highest rank for each channel. The priority of the liver AP is determined. In addition, the access point selector 140 may select the AP having the highest priority among the determined priority of the inter-channel AP as the AP to be connected. At this time, the priority of the inter-channel access point is determined based on the estimated value of the signal-to-interference noise ratio of the highest access point for each channel.

For reference, the access point selector 140 may set a higher priority as the estimated value of the SINR increases.

Hereinafter, an access point selection method according to an embodiment of the present invention will be described in detail with reference to FIG. 4.

4 is a flowchart illustrating a method of selecting an access point according to an embodiment of the present invention.

First, an AP scanning is performed by receiving a beacon message from a plurality of APs (S410).

In this case, the scanning may be performed at any one of a time point when the user terminal (ie, an access point selecting device) first accesses the corresponding network or when a connection with a specific AP previously connected is terminated and a predetermined period (or time point). Can be performed.

Next, a plurality of APs are classified for each channel based on the beacon information obtained by using the received beacon message (S420).

At this time, among the beacon information included in the beacon message, the information of the frequency band used by the AP (for example, center frequency information) is checked, and the channel number set in advance for the identified frequency band is checked for each AP. Can distinguish channels to

Next, the estimated value of the signal-to-interference noise ratio (SINR) is calculated based on the relative interference strength and the noise strength with other APs included in the same channel for each AP (S430).

In this case, a value obtained by dividing the signal strength of one AP by the sum of signal strengths (ie, interference strengths) and preset noise strengths of other APs of a channel to which the AP belongs is calculated as an estimated value of SINR. For reference, the received signal strength (RSSI) detected when the beacon message is received may be applied as the signal strength of the AP.

In addition, the SINR may be calculated by further considering the interference strength and the noise strength of the corresponding channel, as well as the interference strength and the noise strength of the adjacent channel, for one AP. As described above, the method of calculating the estimated value of the SINR in consideration of the interference strength and the noise strength of one channel and the adjacent channel is the same as the process of calculating the estimated value of the SINR by the selection criterion calculator 130 described with reference to FIG. Similar descriptions will be omitted.

Finally, an AP to be connected is selected based on an estimated value of SINR calculated for each AP (S440).

Specifically, after determining the priority of the AP for each channel and the priority of the AP between channels based on the magnitude of the estimated value of the SINR of each AP, the AP having the highest rank between channels may be selected as the AP to be connected.

For reference, after an AP to be connected is selected, a connection is performed between the user terminal and the selected AP through an authentication and association procedure with the selected AP.

The foregoing description of the present invention is intended for illustration, and it will be understood by those skilled in the art that the present invention may be easily modified in other specific forms without changing the technical spirit or essential features of the present invention. will be. It is therefore to be understood that the above-described embodiments are illustrative in all aspects and not restrictive. For example, each component described as a single entity may be distributed and implemented, and components described as being distributed may also be implemented in a combined form.

The scope of the present invention is shown by the following claims rather than the above description, and all changes or modifications derived from the meaning and scope of the claims and their equivalents should be construed as being included in the scope of the present invention. do.

10: User terminal
100: access point selection device
110: scanning unit
120: channel classification unit
130: selection criterion calculator
140: access point selector

Claims (11)

In the apparatus for selecting an access point,
A scanning unit receiving a beacon message from a plurality of access points;
A channel classifying unit classifying the plurality of access points by channels by checking information of a use frequency included in the beacon message for each access point;
Signal to Interference-plus-Noise Ratio based on the signal strength of one access point divided by the interference and noise strength of the corresponding channel to which the access point belongs. A selection criterion calculator which calculates an estimated value of? And
An access point selector for selecting an access point to be connected among the plurality of access points based on the estimated value of the signal-to-interference noise ratio calculated for each access point,
The interference noise intensity is,
It is the sum of interference strength and noise strength of the corresponding channel,
The selection criterion calculator,
And calculating the estimated value of the signal-to-interference noise ratio by applying the sum of the signal strengths of the other access points in the corresponding channel as the interference intensity and applying a predetermined noise intensity. delete The method of claim 1,
The selection criterion calculator,
When one access point in the corresponding channel is included,
And calculating an estimated value of the signal-to-interference noise ratio by applying a predetermined minimum noise intensity as the noise intensity. The method of claim 1,
The selection criterion calculator,
When a plurality of access points in the corresponding channel is included,
Confirm the transmission scheme information from the beacon message for each access point in the corresponding channel, and calculate the estimated value of the signal-to-interference noise ratio by applying the noise strength to zero when the identified transmission scheme is a preset transmission scheme. Access point selection device. The method of claim 1,
The selection criterion calculator,
The signal strength of the one access point divided by the interference noise strength of the corresponding channel and the interference noise strength of the adjacent channel of the corresponding channel is calculated as an estimated value of the signal-to-interference noise ratio,
And assigning a higher weight to the interference noise strength of the corresponding channel than the interference noise strength of the adjacent channel. 6. The method according to claim 1 or 5,
The access point selector,
Determining the priority of each access point and the priority of the inter-channel access point based on the magnitude of the estimated value of the signal-to-interference noise ratio, and accessing the access point having the highest priority among the priority of the inter-channel access point. Select points,
Priority of the access point between the channels,
And determined based on the estimated value of the signal-to-interference noise ratio of the highest ranking access point for each channel. The method of claim 1,
The selection criterion calculator,
And setting the signal strength based on information of a received signal strength indicator detected at the reception of the beacon message for each access point. In the access point selection method through an access point selection device,
(a) receiving a beacon message from multiple access points via scanning;
(b) identifying information of a use frequency for each access point based on the beacon message, and classifying the plurality of access points based on a channel according to the identified use frequency;
(c) The ratio of the Signal to Interference-plus-Noise Ratio based on the value obtained by dividing the signal strength of each access point by the interference and noise strength of the corresponding channel to which it belongs. Calculating an estimated value; And
(d) selecting an access point to be connected among the plurality of access points based on the estimated value of the signal-to-interference noise ratio calculated for each access point,
The interference noise strength is a sum of interference strength and noise strength of the corresponding channel,
The signal strength is set based on the information of the received signal strength (Received Signal Strength Indicator) detected when receiving the beacon message for each access point,
The step (c)
And applying a sum of the signal strengths of the other access points in the corresponding channel as the interference strength and applying a preset noise strength. The method of claim 8,
The step (c)
When one access point is included in the corresponding channel, a preset minimum noise strength is applied as the noise strength,
When a plurality of access points in the corresponding channel are included, the transmission scheme information is checked from the beacon message for each access point in the corresponding channel, and when the identified transmission scheme is a preset transmission scheme, the noise intensity is zero (0). The access point selection method to apply in). The method of claim 8,
The step (c)
The signal strength of the access point divided by the interference noise strength of the corresponding channel and the interference noise strength of the adjacent channel of the corresponding channel is calculated as an estimated value of the signal-to-interference noise ratio,
And weighting the interference noise strength of the corresponding channel higher than the interference noise strength of the adjacent channel. 11. The method according to claim 8 or 10,
The step (d)
Determining the priority of each access point and the priority of the inter-channel access point based on the magnitude of the estimated value of the signal-to-interference noise ratio, and accessing the access point having the highest priority among the priority of the inter-channel access point. Select points,
Priority of the access point between the channels,
And determined based on the estimated value of the signal-to-interference noise ratio of the highest ranking access point for each channel.

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