Wireless local area network (WLAN) and method of transmitting frame in the WLAN

Abstract

In a Wireless Local Area Network (WLAN) and a method of transmitting a frame in the WLAN, mode information and an available data transfer rate of each wireless terminal located within a coverage of an Access Point (AP) are collected. A determination is made as to whether or not the AP transmits a Clear To Send (CTS) frame depending upon an existence of wireless terminals corresponding to the collected mode information before the AP transmits a data frame to at least one wireless terminal. A data transfer rate of the CTS frame is adjusted based on the collected available data transfer rate of each of the wireless terminals to transmit the CTS frame at the adjusted data transfer rate. Therefore, both the stability and the bandwidth effectiveness may be enhanced.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the present invention and many of the attendant advantages thereof, will be readily apparent as the present invention becomes better understood by reference to the following detailed description when considered in conjunction with the accompanying drawings in which like reference symbols indicate the same or similar components, wherein:

FIG. 1 is a diagram of cell coverage of each node in a Wireless Local Area Network (WLAN);

FIG. 2 is a diagram of a WLAN that transmits Request To Send (RTS)/Clear To Send (CTS) frames;

FIG. 3 is a diagram of a virtual carrier sensing method of an IEEE 802.11 WLAN;

FIG. 4 is a diagram of a configuration of a WLAN according to an exemplary embodiment of the present invention;

FIG. 5 is a diagram of a method of controlling a transmission of frames based on a CTS frame according to an exemplary embodiment of the present invention;

FIG. 6 is a block diagram of an Access Point (AP) according to an exemplary embodiment of the present invention; and

FIG. 7 is a flow diagram of the operation of an AP according to an exemplary embodiment of the present invention.

Claims

1. A method of transmitting a frame in a Wireless Local Area Network (WLAN), the method comprising: collecting mode information and an available data transfer rate of each wireless terminal located within a coverage of the Access Point (AP);determining whether or not the AP transmits a Clear To Send (CTS) frame depending upon an existence of wireless terminals corresponding to the collected mode information before the AP transmits a data frame to at least one wireless terminal among all of the wireless terminals located within a coverage of the AP; andadjusting a data transfer rate of the CTS frame based on the collected available data transfer rate of each of the wireless terminals to transmit the CTS frame at the adjusted data transfer rate.

2. The method of claim 1, wherein the mode information includes information representing one of IEEE 802.11b and IEEE 802.11g.

3. The method of claim 1, wherein determining whether or not the AP transmits a CTS frame includes transmitting the CTS frame when at least one first wireless terminal conforming to IEEE 802.11b and at least one second wireless terminal conforming to IEEE 802.11g are located within a coverage of the AP.

4. The method of claim 3, wherein the adjusted data transfer rate of the CTS frame corresponds to a minimum data transfer rate of available data transfer rates of the at least one first wireless terminal conforming to IEEE 802.11b.

5. The method of claim 1, wherein determining whether or not the AP transmits a CTS frame includes determining that the CTS frame is not transmitted when only first wireless terminals conforming to IEEE 802.11b are located within a coverage of the AP, or when only second wireless terminals conforming to IEEE 802.11g are located within a coverage of the AP.

6. The method of claim 1, wherein the CTS frame is modulated using Complementary Code Keying (CCK) when the adjusted data transfer rate of the CTS frame corresponds to 5.5 Mbps or 11 Mbps, and wherein the CTS frame is modulated using Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) when the adjusted data transfer rate of the CTS frame corresponds to 1 Mbps or 2 Mbps.

7. The method of claim 1, further comprising transmitting a data frame modulated using Complementary Code Keying (CCK) or Orthogonal Frequency Division Multiplexing (OFDM) depending upon the mode information of each of the wireless terminals.

8. The method of claim 7, further comprising receiving the data frame to transmit an ACK frame to the AP by at least one first wireless terminal corresponding to a destination of the data frame.

9. The method of claim 1, further comprising receiving the CTS frame from the AP to cease a data transmission of at least one second wireless terminal during an interval corresponding to a transmission cease time included in a duration field of the CTS frame, the at least one second wireless terminal not corresponding to a destination of the data frame.

10. A method of transmitting a frame in an Access Point (AP) of a Wireless Local Area Network (WLAN), the method comprising: collecting mode information representing one of IEEE 802.11b and IEEE 802.11g and an available data transfer rate of each wireless terminal located within a coverage of the AP;transmitting a Clear To Send (CTS) frame at a minimum data transfer rate of available data transfer rates of at least one first wireless terminal conforming to IEEE 802.11b before sending a data frame when both the at least one first wireless terminal conforming to IEEE 802.11b and at least one second wireless terminal conforming to IEEE 802.11g are located within the coverage of the AP.

11. The method of claim 10, wherein the CTS frame is not transmitted when only first wireless terminals conforming to IEEE 802.11b are located within the coverage of the AP, and wherein whether or not the CTS frame is transmitted is determined based on a number of second wireless terminals conforming to IEEE 802.11g and distances between each of the second wireless terminals and the AP when only the second wireless terminals conforming to IEEE 802.11g are located within the coverage of the AP.

12. A Wireless Local Area Network (WLAN), comprising: an Access Point (AP) adapted to collect mode information and an available data transfer rate of each wireless terminal located within a coverage of the AP, to determine whether or not the AP transmits a Clear To Send (CTS) frame depending upon an existence of wireless terminals corresponding to the collected mode information before the AP transmits a data frame, and to adjust a data transfer rate of the CTS frame based on the collected available data transfer rate of each of the wireless terminals to transmit the CTS frame at the adjusted data transfer rate; andat least one wireless terminal adapted to receive the CTS frame from the AP to cease a data transmission of the at least one wireless terminal during an interval corresponding to a transmission cease time included in a duration field of the CTS frame.

13. The WLAN of claim 12, wherein the mode information includes information representing one of IEEE 802.11b and IEEE 802.11g.

14. The WLAN of claim 12, wherein the AP is adapted to transmit the CTS frame at a minimum data transfer rate of available data transfer rates of at least one first wireless terminal conforming to IEEE 802.11b when both the at least one first wireless terminal conforming to IEEE 802.11b and at least one second wireless terminal conforming to IEEE 802.11g are located within the coverage of the AP.

15. The WLAN of claim 12, wherein the CTS frame is not transmitted when only first wireless terminals conforming to IEEE 802.11b are located within the coverage of the AP, or when only second wireless terminals conforming to IEEE 802.11g are located within the coverage of the AP.

16. The WLAN of claim 12, wherein the CTS frame is modulated using Complementary Code Keying (CCK) when the adjusted data transfer rate of the CTS frame corresponds to 5.5 Mbps or 11 Mbps, and wherein the CTS frame is modulated using Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) when the adjusted data transfer rate of the CTS frame corresponds to 1 Mbps or 2 Mbps.

17. An Access Point (AP) conforming to both IEEE 802.11b and IEEE 802.11b, the AP comprising: a storage unit adapted to store information about all wireless terminals located within a coverage of the AP;a controller adapted to collect mode information of each of the wireless terminals, and to determine a data transfer rate of a Clear To Send (CTS) frame, the determined data transfer rate of the CTS frame corresponding to a minimum data transfer rate of available data transfer rates of at least one first wireless terminal conforming to IEEE 802.11b when both the at least one first wireless terminal conforming to IEEE 802.11b and at least one second wireless terminal conforming to IEEE 802.11g are located within the coverage of the AP; anda frame generator adapted to generate the CTS frame based on the determined data transfer rate of the CTS frame.

18. The AP of claim 17, wherein the frame generator is adapted to modulate the CTS frame using Complementary Code Keying (CCK) when the determined data transfer rate of the CTS frame corresponds to 5.5 Mbps or 11 Mbps, and to modulate the CTS frame using Binary Phase Shift Keying (BPSK) or Quadrature Phase Shift Keying (QPSK) when the determined data transfer rate of the CTS frame corresponds to 1 Mbps or 2 Mbps.

19. The AP of claim 17, wherein the information about each of the wireless terminals includes at least one of a Media Access Control (MAC) address, a mode and available data transfer rate of each of the wireless terminals.

20. The AP of claim 17, further comprising a frame transmitter adapted to transmit the CTS frame generated by the frame generator or a data frame to at least one wireless terminal.