Method and system for controlling wireless communication channel

A portable terminal is capable of controlling a wireless communication channel control. If a particular wireless communication channel established between the portable terminal and access points (APs) is congested, the portable terminal is switched to one of the channels used by APs whose number is less than the number of APs using the particular wireless communication channel.

The present application is related to and claims the benefit under 35 U.S.C. §119(a) of a Korean patent application filed in the Korean Intellectual Property Office on Jan. 12, 2009 and assigned Serial No. 10-2009-0002397, the entire disclosure of which is hereby incorporated by reference

TECHNICAL FIELD OF THE INVENTION

The present invention relates to wireless communication systems, and more particularly, to a wireless communication channel control method and system that can switch a wireless communication channel, established between a portable terminal and an access point (AP), to a channel used by a relatively small number of access points (APs) if the wireless communication channel is congested.

BACKGROUND OF THE INVENTION

Recently, wireless local area network (WLAN) protocols whose wireless coverage range is short have been developed considering the mobility. Examples of the WLAN protocols are Wi-Fi, Bluetooth, ZigBee, and the like. WLAN protocols define a variety of technical standards to connect systems to a wired network via access points (APs). WLAN protocols include 802.11b and 802.11g protocols, which uses 2.4 GHz frequency band, and 802.11a protocol that uses 5 GHz frequency band. WLAN protocols allow for communication using a plurality of channels. For example, 802.11b and 802.11g protocols each include 14 channels that are spaced 5 MHz apart except for a 12 MHz spacing before last channel, that is, Channel 14. However, the 802.11b and 802.11g protocols each require 25 MHz of channel separation, adjacent channels overlap and will interfere with each other.

With the development of communication technology, portable terminals supporting WLAN protocols, such as Wi-Fi, and the like, are increasing. These portable terminals can wirelessly establish communication channels with APs and provide Internet services through the APs. The portable terminals supporting a Wi-Fi protocol are configured to establish a fixed wireless communication channel with APs. That is, the conventional portable terminals establish a wireless communication channel with a particular AP, using a preset channel, and do not change the channel. Therefore, if a plurality of APs use the same channel or adjacent channels, the wireless communication channel between the portable terminal and the AP may be congested due to frequency interference. That is, if a plurality of APs, located close to a portable terminal, use the same channel or adjacent channels, the portable terminal experiences the decrease of the communication speed and the disconnection of the communication channel.

SUMMARY OF THE INVENTION

To address the above-discussed deficiencies of the prior art, it is a primary object to provide a wireless communication channel control method and system that can check whether a wireless communication channel, established between a portable terminal and an access point (AP), is congested and switch the wireless communication channel to a channel where a congestion has not occurred, that is, which is used by a relatively small number of access points (APs) if the wireless communication channel is congested.

In accordance with an exemplary embodiment of the present invention, the present invention provides a method for controlling wireless communication channels including: establishing a wireless communication channel via a particular channel set to an access point (AP), where the wireless communication channel is one of a plurality of channels that may be established between a portable terminal and the AP; checking whether the particular channel is congested; identifying, if the particular channel is congested, information regarding channels used by a plurality of APs located in a range of communication of the portable terminal, and comparing the number of APs by channels; and switching the wireless communication channel to one of the mobile channels that serve as channels used by APs whose number is less than the number of APs using the particular channel.

In accordance with another exemplary embodiment of the present invention, the present invention provides a system for controlling wireless communication channels, including: a plurality of access points (APs); and a portable terminal that can establish a wireless communication channel with one selected from among the plurality of APs via a particular channel set to the selected AP and for switching, if the wireless communication channel established via the particular channel is congested, the wireless communication channel to one of the mobile channels that serve as channels used by APs whose number is less than the number of APs using the particular channel.

In accordance with another exemplary embodiment of the present invention, the present invention provides a portable terminal capable of controlling wireless communication channels, the portable terminal comprising: a wireless local area network (WLAN) communication unit configured to communicate an RF signal with the selected AP; and a controller configured to communicate with a plurality of access points (APs), to establish a wireless communication channel with a selected AP from among the plurality of APs via a particular channel set to the selected AP, to switch, if the wireless communication channel established via the particular channel is congested, the wireless communication channel to one of the mobile channels that serve as channels used by APs whose number is less than the number of APs using the particular channel.

DETAILED DESCRIPTION OF THE INVENTION

Prior to explaining the embodiments of the present invention, terminologies will be defined for the present description below. The terms or words described in the present description and the claims should not be limited by a general or lexical meaning, instead should be analyzed as a meaning and a concept through which the inventor defines and describes the present invention at his most effort, to comply with the idea of the present invention. Therefore, one skilled in the art will understand that the embodiments disclosed in the description and configurations illustrated in the drawings are only preferred embodiments, instead there may be various modifications, alterations, and equivalents thereof to replace the embodiments at the time of filing this application.

The term ‘packet error rate (PER)’ refers to the ratio of the number of retransmitted packets to the total number of received packets for a certain time period.

The term ‘retransmission rate (RR)’ refers to the ratio of the number of retransmitted packets to the total number of transmitted packets for a certain time period.

The term ‘congestion’ refers to a state where at least one of the PER and the RR is equal to or greater than a preset threshold. In an embodiment of the present invention, it is assumed that congestion occurs in a wireless communication channel used by a relatively large number of APs.

The term ‘mobile channels’ refer to channels used by APs whose number is less than the number of APs that use a particular channel having established a communication channel, where the channels are portion of a plurality of channels may be established between a portable terminal and an AP.

FIG. 1illustrates a configuration of a system for controlling a wireless communication channel, according to an embodiment of the present invention.

A wireless communication network system may include a plurality of wireless communication devices100,200, and300, and a plurality of access points (APs)10,20, and30. The wireless communication network system uses WLAN protocols, for example, a Wi-Fi protocol. In an embodiment of the present invention, the wireless communication channel control system will be explained, referring to the portable terminal100and the first AP10. AlthoughFIG. 1shows three APs and three wireless communication devices, respectively, it should be understood that the present invention is not limited to the embodiment. For example, the wireless communication network system according to the present invention may be implemented with at least one or more wireless communication devices and APs.

The portable terminal100refers to a terminal that can perform Wi-Fi communication and can establish a wireless communication channel with one of the plurality of APs10,20and30. In the following description, embodiments of the present invention will be explained under the assumption that the portable terminal100establishes a wireless communication channel with the first AP10. In order to establish a wireless communication channel, the portable terminal100may transmit a probe request message with respect to a plurality of channels. That is, the portable terminal100scans frequencies to seek a connectable AP. The APs10,20, and30receives the probe request message and transmit a probe response message to the portable terminal100. The probe response message contains a service set identifier (SSID) of an AP and information regarding a channel set and stored in an AP which is hereinafter called a particular channel. The portable terminal100receives the probe response messages and displays the SSID of each of the APs. Thereafter, if one of the SSIDs, for example, an SSID corresponding to the first AP10, is selected, the portable terminal100establishes a wireless communication channel with the first AP10, using a channel set in the first AP10, that is, a particular channel. Alternatively, if the portable terminal100has already stored information regarding the first AP10with which the portable terminal100intends to establish a wireless communication channel, the portable terminal100can directly transmit an associate request message to the first AP10. In particular, if the particular channel is congested, the portable terminal100may perform a switching operation with respect to the wireless communication channel. For example, if frequency interference and traffic increase due to the increase of the number of APs using the particular channel, that is, the second and third APs20and30establish wireless communication channels with other portable terminals using the particular channel set in the first AP10, the particular channel may be congested. The portable terminal100may identify information regarding channels used by a plurality of APs existing within a certain range of communication in order to switch a wireless communication channel. Thereafter, the portable terminal100estimates the number of APs for each channel, which means the number of APs using each channel, and then switches the wireless communication channel to one of the mobile channels, where the mobile channels are channels used by APs whose number is less than the number of APs that use the particular channel. The channel switching operation will be explained later.

The first AP10refers to a device that establishes a wireless communication channel with the portable terminal100and allows the portable terminal100to access a wired network, for example, the Internet. The first AP10may store a particular channel, such as, channel 6, to establish a wireless communication channel with the portable terminal100. The particular channel stored in the first AP10may be changed according to a user's operation. In particular, if the first AP10receives a channel switch message from the portable terminal100, the first AP10can switch the particular channel to one of the mobile channels according to the received message. More specifically, if the portable terminal100ascertains that the particular channel is congested, the portable terminal100may transmit a channel switch message, requesting to switch the particular channel to one selected from among the mobile channels, to the first AP10. The channel switch message contains an Internet protocol (IP) address of the first AP10and information regarding one selected from among the mobile channels. The first AP10receives the channel switch message and then switches the wireless communication channel to the selected channel. If the portable terminal100needs to reestablish a communication channel released by the channel switching operation of the first AP10, the portable terminal100may transmit an associate request message to the first AP10via the selected channel. The first AP10transmits a response message, replying to the associate request message, to the portable terminal100, thereby completing the channel switching operation. It is preferable that the channel switch operation be performed within a few milliseconds so that users cannot recognize disconnection of a communication channel.

In the foregoing description, the wireless communication channel control system has been explained. A detailed description is provided regarding the configuration of a portable terminal according to an embodiment of the present invention with reference toFIG. 2.

FIG. 2illustrates a portable terminal100according to an embodiment of the present invention.

Referring toFIGS. 1 and 2, the portable terminal100includes a controller110, a storage unit120, and a wireless local area network (WLAN) communication unit140.

The WLAN communication unit140performs wireless communication with the first AP10located in a WLAN service area. The WLAN communication unit140may include an RF transmitter and an RF receiver. The RF transmitter up-coverts the frequency of signals that will be transmitted and amplifies the signals. The RF receiver low-noise amplifies received RF signals and down-coverts the frequency of the received RF signals. If a particular channel is congested, the WLAN communication unit140transmits a channel switch message to the first AP10under the control of the controller110. The WLAN communication unit140transmits a probe request message to a plurality of APs located within a range of communication in order to calculate the number of APs for each channel, and receives probe response messages therefrom, under the control of the controller110. The WLAN communication unit140transmits an associate request message to the first AP10to establish a wireless communication channel, and receives a response message thereto from first AP10, under the control of the controller110.

The storage unit120stores a program for controlling the entire operation of the portable terminal100as well as an operating system (OS) for booting the portable terminal100. The storage unit120may also store application programs required to play-back multimedia contents. The storage unit120can store data generated when the portable terminal100is operated. In an embodiment of the present invention, the storage unit120stores a program for identifying whether a particular channel is congested and switching the particular channel to the other channel. The storage unit120stores a reference value for identifying channels environments of the first AP10and the portable terminal100, and first and second thresholds for determining whether the particular channel is congested. It is preferable that the second threshold is greater than the first threshold.

The storage unit120may also store the following table 1 to identify the mobile channels and to calculate the number of APs for each channel.

TABLE 1ChannelsNo. of APs132432405265758790108113125136140

Table 1 shows the number of APs for each channel, based on a Wi-Fi communication channel in 2.4 GHz band.

Referring to Table 1, if a wireless communication channel between the first AP10and the portable terminal100is established via Channel 6, the mobile channels may be Channels 1 to 5, 9, 11, and 14. Thereafter, the controller110may switch the wireless communication channel to one of the mobile channels. A method for selecting one from among the mobile channels will be described later. In an embodiment of the present invention, although the mobile channels have been explained in such a way that they are used by APs whose number is less than the number of APs using the particular channel, it should be understood that the present invention is not limited to the embodiment. For example, the mobile channels may be set as a channel used by APs whose number is at least two less than the number of APs using the particular channel. if the mobile channel is set a channel, such as Channel 2, used by APs whose number is one less than the number of APs using the particular channel, the channel switching effect is not large because the channel switching operation is performed and then the number of APs of Channel 2 is the same as the number of APs of a previous particular channel.

The controller110controls the entire operation of the portable terminal100and signal flows among elements in the portable terminal100. The controller110can also control the data process function. In an embodiment of the present invention, the controller110establishes a wireless communication channel with the first AP10using the particular channel and checks whether the particular channel is congested. As such, the controller110may further include a WLAN module11.

The WLAN module11controls the WLAN communication unit140to perform wireless communication. In an embodiment of the present invention, the WLAN module11continues monitoring the PER and RR and outputs them to the controller110.

The controller110receives the PER and RR, and checks whether the particular channel is congested referring to first and second thresholds stored in the storage unit120. In an embodiment of the present invention, the congestion determining conditions may be differently set according to the channel environment between the first AP10and the portable terminal100. For example, the controller110measures the received signal strength indication (RSSI) to check the channel environment. In a case where the RSSI is equal to and greater than a preset reference value, that is, a transmission and reception state is proper, if at least one of the PER and RR is equal to or greater than the first threshold, the controller110concludes that the particular channel is congested. Conversely, in a case where the RSSI is less than a preset reference value, that is, a transmission and reception state is insufficient, if at least one of the PER and RR is equal to or greater than the second threshold that is greater than the first threshold, the controller110concludes that the current channel is congested. Alternatively, the controller110calculates the frequency that at least one of the PER and RR is equal to or greater than the first threshold for a preset period and concludes that the particular channel is congested if the calculated frequency is equal to or greater than a preset value. If the controller110ascertains that the particular channel is congested, the controller110transmits a probe request message to a plurality of APs located within a range of communication of the WLAN communication unit140and then receives probe response messages there from. Transmission of the probe request message may be performed with respect to each of the plurality channels that may be established between the portable terminal100and the first AP10.

Thereafter, the controller110identifies the probe response messages and calculates the number of APs by channels. The controller110compares the number of APs by channels and then switches a wireless communication channel to one of the mobile channels, where the mobile channels refer to channels used by APs whose number is less than the number of APs using the particular channel. The controller110may switch the wireless communication channel to one of the mobile channels, used by the least number of APs. If the least number of APs uses a number of channels, the controller110switches the wireless communication channel to a channel that is spaced apart from the particular channel with the largest frequency difference. For example, as described in table 1, if Channels 4, 9, and 14 are used by the least number of APs and the particular channel is Channel 6, the controller110may switch the wireless communication channel to Channel 14 that is spaced apart there from with the largest frequency difference.

The controller110may calculate the summation of the number of APs of channels adjacent to the mobile channels, and switch the wireless communication channel to the mobile channel having the smallest summation. This channel switching operation is performed because of the following reason. That is, if a number of APs use a channel adjacent to the mobile channels used by the least number of APs, the frequency of the adjacent channel causes the congestion in the wireless communication channel established between the portable terminal100and the first AP10. For example, as described in table 1, regarding a case where a wireless communication channel is switched to Channel 9, Channel 9 is used by no AP but Channels 8 and 10 adjacent to Channel 9 are used by a plurality of APs, so that Channel 9 may be congested by the frequency interference due to Channels 8 and 10. Therefore, it is not preferable that a wireless communication channel be switched to Channel 9.

The controller110may generate a channel switch message and transmit it to the first AP10. The first AP10receives the channel switch message and performs a channel switching operation. The controller110transmits an associate request message to the first AP10, and receives a response message thereto to reestablish a wireless communication channel that was released by the channel switching operation of the first AP10. It is preferable that the channel switching operation be performed within a few milliseconds so that a user cannot recognize the disconnection of a communication channel.

Although it is not shown inFIGS. 1 and 2, the portable terminal100may further includes a camera module for capturing images or moving images, a broadcast receiver module for receiving broadcasts, an audio signal outputting device such as a speaker, an audio signal inputting device such as a microphone, a digital audio source reproducing module such as an MP3 player module, and the like. With the convergence of digital devices, there may be many digital devices and modifications thereof, not listed in the application, and, it will be appreciated that they can also be included in the portable terminal.

FIG. 3illustrates a flow chart that describes a method for controlling a wireless communication channel according to an embodiment of the present invention.

The wireless communication channel control method according to the present invention will be explained, based on a wireless communication channel established via a particular channel that is set to the first AP10and one of a plurality of channels that may be established between the portable terminal100and the first AP10.

Referring toFIGS. 1 to 3, the controller110identifies and determines whether the particular channel established with the first AP10is congested in blocks301and303. A determination regarding the channel congestion is made whether the PER or RR is equal to or greater than a preset reference value, which will be described herein below with respect toFIG. 4.

When the controller110ascertains that the particular channel is not congested at block303, the controller110retains a wireless communication channel via the particular channel in block305. Alternatively, if the controller110ascertains that the particular channel is congested at block303, the controller110identifies information regarding channels used by a plurality of APs10,20, and30existing within a range of communication of the portable terminal100and compares the number of APs by channels in block307, which will be described later referring toFIG. 5.

Thereafter, the controller110determines whether there are mobile channels that serve as channels used by APs whose number is less than the number of APs using the particular channel in block309. If the controller110ascertains that there are not mobile channels at block309, the controller110returns to and proceeds with block305and retains a wireless communication channel. Alternatively, if the controller110ascertains that there are mobile channels at block309, the controller110switches the wireless communication channel to one of the mobile channels in block313. The controller110generates a channel switch message for switching a wireless communication channel and transmits it to the first AP10. The channel switch message is a format of hyper text transfer protocol (HTTP) and contains an IP address of the first AP10and information regarding one selected from among the mobile channels. The first AP10receives the channel switch message and switches the wireless communication channel to the selected mobile channel. Thereafter, the controller110transmits an associate request message to the first AP10via the selected channel, and receives a response message thereto from the first AP10, thereby completing the channel switching operation with respect to the wireless communication channel. It is preferable that the channel switch operation be performed within a few milliseconds so that users cannot recognize disconnection of a communication channel.

Therefore, the wireless communication channel control method according to the present invention performs wireless communication via a channel used by the least number of APs, thereby preventing the traffic increase, the data loss, and the reduction of communication speed, due to frequency interference.

In the foregoing description, the wireless communication channel control method has been explained. A detailed description is explained regarding a method for identifying whether a particular channel is congested referring toFIG. 4.

FIG. 4illustrates a flow chart that describes a method for identifying whether a particular channel is congested, according to an embodiment of the present invention.

Referring toFIGS. 1 to 4, the controller110measures the received signal strength indication (RSSI) in block401. Thereafter, the controller110checks whether the RSSI is equal to or greater than a preset reference value in block403. This is to identify a transmission/reception state between the portable terminal100and the first AP10and to determine whether the particular channel is congested.

If the controller110ascertains that the RSSI is equal to or greater than a preset reference value, that is, a transmission/reception state is proper, at block403, it determines whether at least one of the PER and RR, from the WLAN module11, is equal to or greater than a first threshold in block411. If the controller110ascertains that at least one of the PER and RR is equal to or greater than a first threshold at block411, the controller110concludes that the particular channel is congested in block407. Alternatively, if the controller110ascertains that at least one of the PER and RR is less than a first threshold at block411, it concludes that the particular channel is not congested in block409. In that case, the controller110retains a wireless communication channel via the particular channel.

Meanwhile, if the controller110ascertains that the RSSI is less than a preset reference value, that is, a transmission/reception state is insufficient, at block403, the controller110determines whether at least one of the PER or RR is equal to or greater than a second threshold that is greater than the first threshold in block405. If the controller110ascertains that at least one of the PER or RR is equal to or greater than a second threshold at block405, it concludes that the particular channel is congested at block407. Alternatively, if the controller110ascertains that at least one of the PER or RR is less than the second threshold at block405, the controller110concludes that the particular channel is not congested at409. In that case, the controller110retains a wireless communication channel via the particular channel.

In an embodiment of the present invention, if the RSSI is less than the reference value, although a determination whether the particular channel is congested is made by identifying whether the PER or RR is equal to or greater than the second threshold, it should be understood that the present invention is not limited to the embodiment. That is, the embodiment may be modified in such a way to calculate the frequency that at least one of the PER and RR is equal to or greater than the first threshold for a preset period, and conclude that the particular channel is congested if the calculated frequency is equal to or greater than a preset value.

In an embodiment of the present invention, although the congestion determination condition is differently set according to the channel environment between the portable terminal100and the first AP10, that is, the transmission/reception state, it should be understood that the present invention is not limited to the embodiment. That is, the embodiment may be modified in such a way to apply the same congestion determination condition to the system without discerning the channel environments.

In the foregoing description, the method for identifying whether the particular channel is congested has been explained. A detailed description is explained regarding a method for comparing the numbers of APs by channels with reference toFIG. 5.

FIG. 5illustrates a flow chart that describes a method for comparing the numbers of access points by channels, according to an embodiment of the present invention.

Referring toFIGS. 1 to 5, the controller110of the portable terminal100transmits a probe request message to a plurality of APs located in a range of communication of the portable terminal100, via each of a plurality of channels that may be established between the portable terminal100and a first AP10one of the plurality of APs in block501. The controller110receives probe response messages from the plurality of APs in block503. The probe response message contains information regarding a service set identifier (SSID) and an IP address of an AP, and so forth.

The controller110receives the probe response messages and calculates the number of APs by channels in block505. That is, the controller110transmits a probe request message to the plurality of APs via each of the plurality of channels and receives probe response messages there from for a certain period of time. Through this process, the controller110can calculate the number of APs by channels. Thereafter, the controller110determines whether there are mobile channels that serve as channels used by APs whose number is less than the number of APs using the particular channel in block507. If the controller110ascertains that there are not mobile channels at507, the controller110retains a wireless communication channel in block509. Alternatively, if the controller110ascertains that there are mobile channels at507, the controller110selects one from among the mobile channels, used by the lease number of APs in block511.

After that, the controller110switches the wireless communication channel to the selected channel in block513. Although it is not shown inFIG. 5, the controller110may switch the wireless communication channel to a channel that is spaced apart from the particular channel with the largest frequency difference if the least number of APs uses two or more channels.

Although it is not shown inFIG. 5, the controller110may calculate the summation of the number of APs of channels adjacent to the mobile channels, and switch the wireless communication channel to the mobile channel having the smallest summation. This channel switching operation is performed because of the following reason. That is, if a number of APs use a channel adjacent to the mobile channels used by the least number of APs, the frequency of the adjacent channel causes the congestion in the wireless communication channel established between the portable terminal100and the first AP10.

As described above, the wireless communication channel control method and system, according to the present invention, can continue checking whether wireless communication channels established between the portable terminal and APs is congested and can automatically switch the wireless communication channel to a channel used by a relatively small number of APs, thereby preventing the reduction of communication speed and the disconnection of communication and thus enhancing user convenience.