Methods and systems for providing efficient operation of multiple modes in a wlan system

Abstract

A method and apparatus that applies medium access control (MAC) transmission opportunity (TXOP) protection for multiple mode operation in a WLAN system. In particular, MAC mechanisms are defined to support multiple mode CTS frames, and multiple mode CF-End frames sent by the AP, each in a format appropriate for the corresponding mode which may also apply to a single mode. MAC mechanisms permit truncation of TXOP duration for releasing the unused portion of the TXOP when no further data for transmission is available. Release of unused protected TXOP is possible for both protected AP transmissions and STA transmissions.

What is claimed is: 
     
         1 . A method for use in an access point (AP), the method comprising:
 receiving a request-to-send (RTS) frame from a station (STA), wherein the RTS frame indicates a request for a transmit opportunity (TXOP);   transmitting, in response to the RTS frame, an indication of a TXOP, wherein the indication of a TXOP is a space-time block code (STBC) clear-to-send (CTS) frame and a non-STBC CTS frame;   receiving packet data from the STA during the TXOP;   receiving, on a condition that the STA does not have further packet data to transmit, an indication of truncation of the TXOP including a first STBC contention free (CF)-End frame or a first non-STBC CF-End frame; and   transmitting a second STBC CF-End frame and a second non-STBC CF-End frame.   
     
     
         2 . The method of  claim 1 , wherein the receiving the indication of truncation of the TXOP occurs on a condition that sufficient TXOP duration is remaining. 
     
     
         3 . The method of  claim 2 , wherein the remaining TXOP duration is sufficient on a condition that the remaining TXOP duration is greater than a sum of a CF-End frame duration, an STBC CF-End frame duration, a non-STBC CF-End frame duration, and two short interframe spacing (SIFS) durations. 
     
     
         4 . The method of  claim 1 , wherein the indication of truncation of the TXOP indicates a network allocation vector (NAV) reset to the AP. 
     
     
         5 . The method of  claim 1 , wherein each of the second STBC CF-End frame and the second non-STBC CF-End frame indicate an end of a contention free interval. 
     
     
         6 . The method of  claim 1 , wherein a short interframe spacing (SIFS) duration separates the second STBC CF-End frame and the second non-STBC CF-End frame. 
     
     
         7 . The method of  claim 1 , wherein the receiving an indication of truncation of the TXOP includes receiving a CF-End frame using a same modulation type as the received packet data. 
     
     
         8 . The method of  claim 1 , wherein on a condition that the RTS frame is an STBC RTS frame, transmitting the STBC CTS frame followed by the non-STBC CTS frame, and on a condition that the RTS frame is a non-STBC RTS frame, transmitting the non-STBC CTS frame followed by the STBC CTS frame. 
     
     
         9 . The method of  claim 1 , wherein on a condition that the indication of truncation of the TXOP is an STBC CF-End frame, transmitting the second STBC CF-End frame followed by the second non-STBC CF-End frame. 
     
     
         10 . The method of  claim 1 , wherein on a condition that the indication of truncation of the TXOP is a non-STBC CF-End frame, transmitting the second non-STBC CF-End frame followed by the second STBC CF-End frame. 
     
     
         11 . An access point (AP) comprising:
 a receiver configured to receive a request-to-send (RTS) frame from a station (STA), wherein the RTS frame indicates a request for a transmit opportunity (TXOP); and   a transmitter configured to transmit, in response to the RTS frame, an indication of a TXOP, wherein the indication of a TXOP is a space-time block code (STBC) clear-to-send (CTS) frame and a non-STBC CTS frame;   wherein the receiver is further configured to receive packet data from the STA during the TXOP, and receive, on a condition that the STA does not have further packet data to transmit, an indication of truncation of the TXOP including a first STBC contention free (CF)-End frame or a first non-STBC CF-End frame; and   wherein the transmitter is further configured to transmit a second STBC CF-End frame and a second non-STBC CF-End frame.   
     
     
         12 . The AP of  claim 11 , wherein the receiver is further configured to receive the indication of truncation of the TXOP on a condition that sufficient TXOP duration is remaining. 
     
     
         13 . The AP of  claim 12 , wherein sufficient TXOP duration is remaining on a condition that a remaining TXOP duration is greater than a CF-End frame duration, an STBC CF-End frame duration, a non-STBC CF-End frame duration, and two short interframe spacing (SIFS) durations. 
     
     
         14 . The AP of  claim 11 , wherein the receiver is further configured to receive an indication of truncation of the TXOP using a CF-End frame using a same modulation type as the received packet data. 
     
     
         15 . The AP of  claim 11 , wherein the indication of truncation of the TXOP indicates a network allocation vector (NAV) reset to the AP. 
     
     
         16 . The AP of  claim 11 , wherein each of the second STBC CF-End frame and the second non-STBC CF-End frame indicate an end of a contention free interval. 
     
     
         17 . The AP of  claim 11 , wherein the transmitter is configured to transmit the second STBC CF-End frame and the second non-STBC CF-End frame separated by a short interframe spacing (SIFS) duration. 
     
     
         18 . The AP of  claim 11 , wherein on a condition that the RTS frame is an STBC RTS frame, the transmitter is further configured to transmit the STBC CTS frame followed by the non-STBC CTS frame, and on a condition that the RTS frame is a non-STBC RTS frame, the transmitter is further configured to transmit the non-STBC CTS frame followed by the STBC CTS frame. 
     
     
         19 . The AP of  claim 11 , wherein on a condition that the indication of truncation of the TXOP is an STBC CF-End frame, the transmitter is further configured to transmit the second STBC CF-End frame followed by the second non-STBC CF-End frame. 
     
     
         20 . The AP of  claim 11 , wherein on a condition that the indication of truncation of the TXOP is a non-STBC CF-End frame, the transmitter is further configured to transmit the second non-STBC CF-End frame followed by the second STBC CF-End frame.