Apparatus and method for controlling data communication in a wireless local area network

0001The present invention relates to an apparatus and method for controlling data communication in a wireless local area network (LAN).

0002<figref idref="f0001">Fig. 1</figref> is a block diagram showing the configuration of a related art portable computer. As shown in <figref idref="f0001">Fig. 1</figref>, the portable computer, such as a notebook computer has a central processing unit (CPU) 10, a display controller 11, a bridge chipset 12, a main memory 13, a read only memory (ROM) 14, a LAN controller 15, an embedded controller 16, a battery 17, etc.

0003The CPU 10 and the bridge chipset 12 are interconnected via a host bus, and the bridge chipset 12, the display controller 11 and the main memory 13 are interconnected via an accelerated graphics port (AGP) bus. The ROM 14, the LAN controller 15 and the embedded controller 16 are interconnected via a system bus.

0004The embedded controller 16 is connected with the battery 17 via a system management (SM) bus to check the remaining power of the battery 17. The LAN controller 15 is connected with a wireless LAN card 20 of the personal computer memory card international association (PCMCIA) card type to perform data communication using a wireless LAN. The LAN controller 15, for example, may be loaded in the form of a chipset on a system board in the portable computer to perform communication.

0005As shown in <figref idref="f0002">Fig. 2</figref>, each of a plurality of stations (STAs) of the wireless LAN card is connected with a portable computer that uses the battery 17, to wirelessly transmit and receive data directly in a basic service set (BSS) network as shown in <figref idref="f0002">Fig. 2</figref>. The stations of the wireless LAN card are adapted to transmit and receive data to/from one another using predefined probe request frames.

0006As shown in <figref idref="f0003">Fig. 3</figref>, on the other hand, different BSS networks BSS1 and BSS2 are connected with a distribution system (DS) network using different access points (APs) to construct an extended service set (ESS) network. Each AP and each STA are adapted to transmit and receive data to/from each other using predefined beacon frames. As a result, a STA of the wireless LAN card connected with the portable computer can wirelessly transmit and receive data directly to/from another STA included in an associated BSS network, and also to/from an STA in another BSS network existing in the ESS network via the DS network.

0007As described above, the related art apparatus and method for controlling data communication in a wireless LAN has various disadvantages. The STA of the wireless LAN card, connected with the portable computer, transmits and receives data to/from another STA or AP at a predetermined high transfer speed after completing an initial setup operation for data communication therewith. In other words, because the STA of the wireless LAN card connected with the portable computer is operated at a fixed transfer speed irrespective of external environments, a large amount of power is consumed in the battery of the portable computer, which results in significant reductions in available time of the portable computer. Further, data communication time of the battery powered portable computer can be reduced.

0008<patcit id="pcit0001" dnum="US6397061B"><text>US-B-6,397,061</text></patcit> describes a wireless communication device capable of communicating with a local wireless network within a predetermined communication range wherein, if the wireless communication device experiences interference, a low battery or movement outside of the predetermined communication range, the wireless communication device checks to see if a bandwidth, a data rate or a priority can be altered to complete the communication between the wireless communication device and the wireless network.

0009In <patcit id="pcit0002" dnum="WO02065262A"><text>WO02/065262</text></patcit>, a power management method for use in electronic devices is disclosed wherein a combination portable computer and mobile telephone device sends the portable computer portion into a sleep mode during periods of non-use and further can periodically and temporarily wake itself up so as to monitor the power consumption of a slave device, the mobile telephone, which depends on the same battery or power source.

0010<nplcit id="ncit0001" npl-type="s"><text>Kyu-Tae Jin et al. describe in "A MAC Algorithm for Energy-limited Ad-hoc Networks", Vehicular Technology Conference, 2000; IEEE VTS Fall VTC 2000 52nd; September 24-28, 2000; Volume 1; pages 219 to 222</text></nplcit>, an energy efficient MAC algorithm based on reservation and scheduling for ad-hoc wireless networks.

0011An object of the invention is to solve at least the above problems and/or disadvantages and to provide at least the advantages described hereinafter.

0012Another object of the present invention is to provide an apparatus and method for controlling data communication in a wireless LAN.

0013Another object of the present invention is to provide an apparatus and method for controlling data communication in a wireless LAN coupled to a portable computer configured to use a battery that determines data transfer speed,responsive to remaining power of the battery.

0014Another object of the present invention is to provide an apparatus and method for controlling data communication in a wireless LAN connected with a portable computer using a battery, whereby a station of a wireless LAN card determines a transfer speed corresponding to the remaining power of the battery and controls data communication with an access point or another station according to the determined transfer speed.

0015Another object of the present invention is to provide an apparatus and method for controlling data communication in a wireless LAN connected with a portable computer using a battery including a station of the wireless LAN that determines a power save period corresponding to the remaining power of the battery and controls data communication with an access point according to the determined power save period.

0016To achieve at least these objects and other advantages in a whole or in part and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided a method for controlling data communication in a wireless local area network (LAN) as defined according to claim 1 that includes checking a battery capacity using a first station and determining a transmission characteristic for a wireless LAN communication corresponding to the checked battery capacity.

0017To further achieve at least these objects and other advantages in a whole or in part and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an apparatus for controlling data communication in a wireless LAN as defined according to claim 17 that includes unit installed at a station of a wireless LAN card for checking the remaining power of a battery of a host computer connected through an interface, unit installed at the station for determining a transmission characteristic corresponding to the checked battery power and recording information corresponding to the determined transmission characteristic in a message to be transmitted to a receiving terminal and unit installed at the station for adjusting a data transmission characteristic with the receiving terminal to the determined transmission characteristic.

0018The apparatus may further include a transmitting wireless LAN terminal coupled to a host computer and configured to determine remaining battery capacity of a host computer, wherein the transmitting station is configured to determine a transmission characteristic for a wireless LAN communication responsive to the remaining battery capacity.

0019Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objects and advantages of the invention may be realized and attained as particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

0020The invention will be described in detail with reference to the following drawings in which like reference numerals refer to like elements wherein: <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig. 1</figref> is a block diagram showing the configuration of a related art portable computer;</li><li><figref idref="f0002">Fig. 2</figref> is a diagram showing a configuration of a related art BSS network including a plurality of stations;</li><li><figref idref="f0003">Fig. 3</figref> is a diagram showing a configuration of a related art ESS network including a plurality of stations and a plurality of access points;</li><li><figref idref="f0004">Fig. 4</figref> is a block diagram showing a station and access point to which an apparatus and method for controlling data communication in a wireless LAN according to the present invention is applied;</li><li><figref idref="f0005">Fig. 5</figref> is a diagram showing the structure of an exemplary beacon frame recorded with transfer speed information according to a first embodiment of the present invention;</li><li><figref idref="f0006">Fig. 6</figref> is a diagram showing the structure of an exemplary probe request frame recorded with transfer speed information according to a second embodiment of the present invention; and</li><li><figref idref="f0007">Figs. 7</figref> and <figref idref="f0008">8</figref> are diagrams showing a power save mode period variably set according to a third embodiment of the present invention and the structure of an exemplary beacon frame recorded with power save period information corresponding thereto, respectively.</li></ul>

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

0021An apparatus and method for controlling data communication in a wireless LAN according to embodiments of the present invention can be applicable to an access point (AP), a station (STA) or the like of a wireless LAN card coupled to a portable computer using a battery. As shown in <figref idref="f0004">Fig. 4</figref>, STA 20 of the wireless LAN card can include a station medium access control (STA MAC) unit 200, a forward error correction (FEC) unit 201, an orthogonal frequency division multiplexing (OFDM) unit 202, and a radio frequency (RF) front end unit 203. The STA MAC unit 200 can be coupled to a host computer, such as the portable computer.

0022The AP 30 can include an AP MAC unit 300, an FEC unit 301, an OFDM unit 302 and an RF front end unit 303. The AP MAC unit 300 can be coupled with an AP controller 304 and Ethernet driver 306 via a bridge chipset 305.

0023The STA 20 of the wireless LAN card can wirelessly transmit and receive data directly to/from another STA included in an associated BSS network using probe request frames as described above with reference to <figref idref="f0002">Fig. 2</figref>, which is in general an ad hoc mode, or wirelessly transmit and receive data to/from an AP included in an ESS network using beacon frames as described above with reference to <figref idref="f0003">Fig. 3</figref>, which is in general an infrastructure mode. According to embodiments of the present invention, the STA 20 of the wireless LAN card is adapted to check the remaining power of the battery through an interface with the portable computer and control a data transfer speed with other stations or access points appropriately according to the checked result for which exemplary embodiments of apparatus and methods will now be described.

0024As described herein, a battery of a portable computer is intended to include a single battery, a plurality of batteries or any type of battery pack or limited power source. Thus, embodiments of the present invention are intended to extend a performance time of portable computer not coupled to an AC power source or the like. However, power can be saved in alternative power modes according to embodiments of the present invention.

0025In a first embodiment of an apparatus and method for controlling data communication in a wireless LAN according to the present invention, after completing an initial setup operation for data communication with the AP, the STA 20 of the wireless LAN card can transmit and receive data at a predetermined high transfer speed. The STA 20 can check the remaining power of the battery through the interface with the portable computer during the data transmission and reception.

0026The STA 20 of the wireless LAN card can then determine the data transfer speed with the AP according to the checked battery power. For example, if the remaining battery power is 80% or more of the full level, the data transfer speed is preferably maintained at the predetermined high transfer speed, e.g., 11Mbps. Alternatively, the data transfer speed is preferably determined to be a second rate e.g., 5.5Mbps if the remaining battery power is within the range of 50 to 79% of the full level, a third rate e.g., 2Mbps if it is within the range of 30 to 49%, and a lowest rate e.g., 1Mbps if it is 29% or less.

0027Thereafter, the STA 20 of the wireless LAN card can provide the AP with the determined data transfer rate. For example, the STA 20 can convert the data transfer speed, determined in a multistage manner based on the remaining power of the battery as described above, into a corresponding unique code value recognizable by the AP, additionally record the converted code value in a beacon frame to be transmitted to the AP, and then transmit the resulting beacon frame to the AP.

0028For example, transfer speed information newly defined according to embodiments of the present invention can be assigned to prescribed bits such as two bits B5 and B6 in capability information contained in an exemplary bps beacon frame, as shown in <figref idref="f0005">Fig. 5</figref>. Accordingly, transfer speed information 'B5B6 = 00' can be additionally recorded in the capability information of the beacon frame if the data transfer speed determined according to the remaining power of the battery is 11Mbps, and 'B5B6 = 01' can be additionally recorded in the capability information if the determined data transfer speed is 5.5Mbps. Transfer speed information 'B5B6 = 10' can be additionally recorded in the capability information if the determined data transfer speed is 2Mbps, and 'B5B6 = 11' if the determined data transfer speed is 1Mbps. However, the present invention is not intended to be so limited.

0029Upon receiving the beacon frame transmitted from the STA 20, the AP can check a code value of the transfer speed information (e.g., B5 and B6) additionally recorded in the capability information of the received beacon frame. The AP can then adjust a data transfer speed with the STA 20 to a value corresponding to the checked code value. Using such an exemplary method, the STA 20 of the wireless LAN card can adjust the data transfer speed with the AP to a value determined according to the remaining battery power, so that it can carry out normal data communication with the AP and efficiently increase an available time or lifetime of the battery.

0030In a second embodiment of an apparatus and method for controlling data communication in a wireless LAN according to the present invention, after completing an initial setup operation for data communication with a selected or determined STA, the STA 20 of the wireless LAN card can transmit and receive data at a predetermined high transfer speed. Then, the STA 20 can check the remaining power of the battery through the interface with the portable computer during the data transmission and reception. The STA 20 of the wireless LAN card can then determines the data transfer speed with the selected STA according to the checked battery power. In a similar manner to the first embodiment, if the remaining battery power is 80% or more of the full level, the data transfer speed is preferably maintained at the predetermined high transfer speed, 11Mbps. Also, the data transfer speed is preferably determined to be 5.5Mbps if the remaining battery power is within the range of 50 to 79% of the full level, 2Mbps if it is within the range of 30 to 49%, and 1Mbps if it is 29% or less. However, the present invention is not intended to be so limited. For example, different ranges of battery power or data transfer speeds, and more or fewer ranges of battery power or data transfer speeds can be used.

0031Subsequently, the STA 20 of the wireless LAN card can convert the data transfer speed, determined in a multistage manner based on the remaining power of the battery as described above, into a corresponding unique code value recognizable by the selected STA, and record the converted code value in a probe request frame to be transmitted to the selected STA. Then, STA 20 can transmit the resulting probe request frame to the selected STA.

0032Transfer speed information can be, for example, 2 bits B0 and B1 newly defined according to embodiments of the present invention and can be assigned to an exemplary bps probe request frame, as shown in <figref idref="f0006">Fig. 6</figref>. Transfer speed information 'B0B1 = 00' can be recorded in the probe request frame if the data transfer speed determined according to the remaining power of the battery is 11Mbps, and 'B0B1 = 01' can be recorded in the probe request frame if the determined data transfer speed is 5.5Mbps. Also, transfer speed information 'B0B1 = 10' can be recorded in the probe request frame if the determined data transfer speed is 2Mbps, and 'B0B1 = 11' can be recorded if the determined data transfer speed is 1Mbps. However, the present invention is not intended to be so limited as different numbers of bits or codes can be used.

0033Thus, upon receiving the probe request frame transmitted from the STA 20, the selected STA can check a code value of the transfer speed information (e.g., B0 and B1) recorded in the received probe request frame, and adjust a data transfer speed with the STA 20 to a value corresponding to the checked code value. Preferably, after performing such operations, the STA 20 of the wireless LAN card can adjust the data transfer speed with the selected STA to a value determined according to the STA 20 corresponding remaining battery power, so that it can carry out normal data communication with the selected STA and increase or prolong an available time of the battery.

0034Further, the STA 20 of the wireless LAN card can be adapted to determine whether there is valid data received from an AP. For example, the STA 20 can determine if there is valid data in a delivery traffic indication message (DTIM) signal transmitted from the AP as shown in <figref idref="f0007">Fig. 7</figref>. In the case where the STA 20 of the wireless LAN card is set to a power save mode, it preferably wakes up at an interval of a natural number multiple of a beacon interval to check the DTIM signal transmitted from the AP. According to preferred embodiments of the present invention, the STA 20 can set a wakeup period in consideration of the remaining battery power to increase the available time of the battery.

0035For example, in the power save mode, the AP transmits the DTIM signal at an interval of 100msec, and the STA 20 wakes up at a period corresponding to about 300msec to check the transmitted DTIM signal. According to a third embodiment of the present invention, the STA 20 of the wireless LAN card check the remaining power of the battery through the interface with the portable computer and adjust the power save mode period according to the checked battery power.

0036For example, if the remaining battery power is 80% or more of the full level, the power save mode period can be maintained at the initial value, 300msec. Also, the power save mode period can be determined to be 400msec if the remaining battery power is within the range of 50 to 79% of the full level, 500msec if it is within the range of 30 to 49%, and 650msec if it is 29% or less. However, the present invention is not intended to be so limited as more, less or different battery ranges and power save mode periods can be used.

0037Thereafter, the STA 20 of the wireless LAN card can convert the power save mode period, determined in a multistage manner based on the remaining power of the battery as described above, into a corresponding unique code value recognizable by the AP. The STA 20 can additionally record the converted code value in a beacon frame to be transmitted to the AP, and then transmit the resulting beacon frame to the AP.

0038For example, as shown in <figref idref="f0008">Fig. 8</figref>, power save period information newly defined according to the third embodiment can be assigned to two bits (e.g., B5 and B6) in beacon interval information contained in a beacon frame. Exemplary power save period information 'B5B6 = 00' is additionally recorded in the beacon interval information of the beacon frame if the power save mode period determined according to the remaining power of the battery is 300msec. 'B5B6 = 01' is additionally recorded in the beacon interval information if the determined power save mode period is 400msec. Also, power save period information 'B5B6 = 10' is recorded in the beacon interval information if the determined power save mode period is 500msec, and 'B5B6 = 11' is recorded in the beacon interval information if the determined power save mode period is 650msec.

0039Upon receiving the beacon frame transmitted from the STA 20, the AP checks a code value of the power save period information (e.g., B5 and B6) additionally recorded in the beacon interval information of the received beacon frame, and can adjust a transmission period of the DTIM signal to be transmitted to the STA 20 to a value corresponding to the checked code value. Also according to embodiments of the present invention, the AP can recognize the respective remaining battery powers of a plurality of stations including the STA 20 from power save period information received from the stations and assign a highest priority for data transmission and reception to any one of the stations having a lowest one of the remaining battery powers.

0040Preferably, after performing such operations, the STA 20 of the wireless LAN card can adjust the power save mode period to a value determined according to the remaining battery power, so that it can carry out normal data communication with the AP. Thus, the STA 20 can increase the available time of the battery.

0041As described above, preferred embodiments used beacon frame and probe request frame messages. However, embodiments of the present invention are not intended to be so limited. For example, other messages or newly defined messages can be used so long as the corresponding information having a desired granularity can be included.

0042Any reference in this specification to "one embodiment," "an embodiment," "example embodiment," "first embodiment," etc., means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of such phrases in various places in the specification are not necessarily all referring to the same embodiment. Further, when a particular feature, structure, or characteristic is described in connection with any embodiment, it is submitted that it is within the purview of one skilled in the art to effect such feature, structure, or characteristic in connection with other ones of the embodiments. Furthermore, for ease of understanding, certain method procedures may have been delineated as separate procedures; however, these separately delineated procedures should not be construed as necessarily order dependent in their performance. That is, some procedures may be able to be performed in an alternative ordering, simultaneously, etc.

0043As described above, embodiments of an apparatus and method for controlling data communication in a wireless LAN have various advantages. Embodiments of the present invention can provide an apparatus and method for controlling data communication in a wireless LAN including a station of a wireless LAN card coupled to a portable computer using a battery that can reduce or prevent power of the battery from being abruptly reduced because of the wireless LAN and normally perform data communication with an access point or another station during such reduced power control. Further, embodiments can be applied to an ad hoc mode or an infrastructure mode of an wireless LAN.

0044The foregoing embodiments and advantages are merely exemplary and are not to be construed as limiting the present invention. The present teaching can be readily applied to other types of apparatuses. The description of the present invention is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. In the claims, means-plus-function clauses are intended to cover the structures described herein as performing the recited function and not only structural equivalents but also equivalent structures.