System and Method for WLAN OFDMA Design of Uplink and Downlink Transmissions

Abstract

Embodiments are provided for WLAN OFDMA operations in uplink and downlink transmissions. For OFDMA downlink transmission, an access point (AP) sends a signaling requesting protection of a transmission channel from access by stations (STAs) associated with the AP. The AP then sends an OFDMA physical layer Protocol Data Unit (PPDU) and a Block Acknowledgement Request (BAR) to the STAs, and receives a Block Acknowledgement (BA) from each one of the STAs. For OFDMA uplink transmissions, an STA sends a signaling requesting protection of a transmission channel from access by the AP. The STA then sends, to the AP, a frame indicating start of OFDMA transmission by the STA, and receives, from the AP, an OFDMA Begin Receive (OBR) frame, which is sent by the AP to participating STAs. The STA then sends an OFDMA PPDU and a BAR to the AP, and receives a BA in return.

What is claimed is: 
     
         1 . A method by an access point (AP) for Orthogonal Frequency Division Multiple Access (OFDMA) downlink transmission in a Wireless Local Area Network (WLAN), the method comprising:
 sending a signaling requesting protection of a transmission channel for downlink transmissions from access by stations (STAs) associated with the AP;   sending an OFDMA physical layer Protocol Data Unit (PPDU) to the STAs;   sending a Block Acknowledgement Request (BAR) to the STAs; and   receiving a Block Acknowledgement (BA) from each one of the STAs.   
     
     
         2 . The method of  claim 1 , further comprising gaining access to the transmission channel before sending the signaling. 
     
     
         3 . The method of  claim 1 , wherein sending the signaling requesting protection of the transmission channel from access by the STAs includes sending by the AP a clear-to-send (CTS) frame, wherein the CTS frame is sent using a non-High Throughput (non-HT) format and comprises timing information allowing the STAs to defer their transmissions by an amount of time. 
     
     
         4 . The method of  claim 3 , wherein the timing information is sent in one of a Legacy Signal Field (L-SIG) of the CTS frame for legacy STAs and a Duration/ID field of the CTS frame for non-OFDMA STAs. 
     
     
         5 . The method of  claim 1 , wherein sending the signaling requesting protection of the transmission channel from access by stations (STAs) includes:
 sending a request-to-send (RTS) message to the STAs, wherein the RTS message comprises timing information allowing the STAs to defer their transmissions by an amount of time; and   receiving a clear-to-send (CTS) message from the STAs.   
     
     
         6 . The method of  claim 5 , wherein the RTS message and the CTS message are sent using non-High Throughput (non-HT) format. 
     
     
         7 . The method of  claim 1 , wherein the OFDMA PPDU comprises a Signaling (SIG) field including a group ID that identifies recipient STAs for the OFDMA PPDU, wherein OFDMA resource allocation in the SIG field is determined by a previous packet transmission from the AP. 
     
     
         8 . The method of  claim 1 , wherein the STAs support OFDMA uplink transmission, wherein the BAR comprises a BAR information field of variable length, the BAR information field including timing information for synchronizing OFDMA uplink transmissions from the STAs, and wherein the BA is sent by the STAs simultaneously using OFDMA. 
     
     
         9 . The method of  claim 1 , wherein the STAs do not support OFDMA uplink transmission, wherein the BAR is sent using non-High Throughput (non-HT) format and comprises a BAR control field of variable number of bits according to a maximum number of the STAs, the BAR control field indicating a sequence of transmissions to the STAs, and wherein the BA is sent by the STAs according to the sequence of transmissions. 
     
     
         10 . A method by a station (STA) for Orthogonal Frequency Division Multiple Access (OFDMA) downlink transmission in a Wireless Local Area Network (WLAN), the method comprising:
 detecting a signaling from an access point (AP), the signaling indicating the AP requesting protection of a transmission channel from access by a plurality of STAs associated with the AP including the STA;   receiving, from the AP an OFDMA physical layer Protocol Data Unit (PPDU);   receiving, from the AP, a Block Acknowledgement Request (BAR), wherein the BAR is sent to the STAs; and   sending, to the AP, a Block Acknowledgement (BA).   
     
     
         11 . The method of  claim 10 , wherein detecting the signaling from the AP comprises detecting a clear-to-send (CTS) frame by the AP, wherein the CTS frame is sent using a non-High Throughput (non-HT) format and comprises timing information allowing the STAs to defer transmission by an amount of time. 
     
     
         12 . The method of  claim 10 , wherein detecting the signaling from the AP comprises receiving from the AP, a request-to-send (RTS) message that is sent to the STAs, wherein the RTS message comprises timing information allowing the STAs to defer transmission by an amount of time, and wherein the method further comprises sending, to the AP, a clear-to-send (CTS) message in response to the RTS message. 
     
     
         13 . A method by a station (STA) for Orthogonal Frequency Division Multiple Access (OFDMA) uplink transmissions in a Wireless Local Area Network (WLAN), the method comprising:
 sending a signaling requesting protection of a transmission channel for uplink transmissions from access by an access point (AP) of the STA;   sending, to the AP, a frame indicating start of OFDMA transmission by the STA;   receiving, from the AP, an OFDMA Begin Receive (OBR) frame, wherein the OBR frame is sent by the AP to a plurality of STAs associated with the AP including the STA;   sending, to the AP, an Orthogonal Frequency Division Multiple Access (OFDMA) physical layer Protocol Data Unit (PPDU);   sending a Block Acknowledgement Request (BAR) to the AP; and   receiving a Block Acknowledgement (BA) from the AP.   
     
     
         14 . The method of  claim 13 , further comprising gaining access to the transmission channel before sending the signaling. 
     
     
         15 . The method of  claim 13 , wherein sending the signaling requesting protection of the transmission channel from the AP includes:
 sending, to the AP, a request-to-send (RTS) message, wherein the RTS message comprises time information allowing the AP to defer transmission by an amount of time; and   receiving, from the AP, a clear-to-send (CTS) message, wherein the CTS message is sent by the AP to the STAs.   
     
     
         16 . The method of  claim 15 , wherein the OBR frame includes identities of STAs selected for OFDMA uplink transmissions and optionally at least one of timing information for the STAs for synchronizing OFDMA transmissions from the STAs, allocation of a plurality of subcarrier groups to the STAs for OFDMA transmissions, and a maximum PPDU length for the STAs. 
     
     
         17 . The method of  claim 16 , wherein the OBR comprises a group ID designating the STAs, and a plurality of subcarrier group indices indicating the subcarrier groups. 
     
     
         18 . The method of  claim 16 , wherein the OFDMA PPDU is sent to the AP on one or more subcarriers from the subcarrier groups allocated to the STA. 
     
     
         19 . The method of  claim 13 , before sending the OFDMA PPDU, waiting an amount of time providing an Inter Frame Spacing between receiving the OBR frame and sending the OFDMA PPDU, wherein the Inter Frame Spacing allows the STA to switch from receiving mode to transmitting mode. 
     
     
         20 . A method by an access point (AP) for Orthogonal Frequency Division Multiple Access (OFDMA) uplink transmission in a Wireless Local Area Network (WLAN), the method comprising:
 detecting a signaling from a station (STA), the signaling indicating the STA requesting protection of a transmission channel from access by the AP;   receiving, from the STA, a frame indicating start of OFDMA transmission by the STA;   sending, to a plurality of STAs associated with the AP including the STA, an OFDMA Begin Receive (OBR) frame;   receiving, from the STA, an OFDMA physical layer Protocol Data Unit (PPDU);   receiving, from the STA, a Block Acknowledgement Request (BAR); and   sending, to the STA, a Block Acknowledgement (BA).   
     
     
         21 . The method of  claim 20 , wherein detecting the signaling from the STA includes:
 receiving, from the STA, a request-to-send (RTS) message, wherein the RTS message comprises time information allowing the AP to defer transmission by an amount of time; and   sending, to the STAs, a clear-to-send (CTS) message.   
     
     
         22 . The method of  claim 20 , wherein the OBR frame includes allocation of a plurality of subcarrier groups to the STAs for OFDMA transmissions, and wherein the method further comprises receiving from the STAs simultaneously a plurality of OFDMA PPDUs on respective subcarriers of the STAs according to the allocation of the subcarrier groups to the STAs. 
     
     
         23 . The method of  claim 20  further comprising, upon receiving the OBR frame from the STA, selecting other STAs to participate with the STA in the OFDMA uplink transmission. 
     
     
         24 . An access point (AP) supporting Orthogonal Frequency Division Multiple Access (OFDMA) transmission in a Wireless Local Area Network (WLAN), the AP comprising:
 a processor; and   a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
 send a signaling requesting protection of a transmission channel from access by stations (STAs) associated with the AP; 
 send an Orthogonal Frequency Division Multiple Access (OFDMA) physical layer Protocol Data Unit (PPDU) to the STAs; 
 send a Block Acknowledgement Request (BAR) to the STAs; and 
 receive a Block Acknowledgement (BA) from each one of the STAs. 
   
     
     
         25 . The AP of  claim 24 , wherein the programming includes further instructions to:
 detect a signaling from a STA, the signaling indicating the STA requesting protection of a transmission channel for uplink transmissions from access by the AP;   receive, from the STA, a frame indicating start of OFDMA transmission by the STA;   send, to the STAs including the STA, an OFDMA Begin Receive (OBR) frame;   receive, from the STAs, OFDMA physical layer Protocol Data Units (PPDUs);   receive, from the STAs, Block Acknowledgement Requests (BARs); and   send, to the STAs, Block Acknowledgements (BAs).   
     
     
         26 . A user station supporting Orthogonal Frequency Division Multiple Access (OFDMA) transmission in a Wireless Local Area Network (WLAN), the user station comprising:
 a processor; and   a computer readable storage medium storing programming for execution by the processor, the programming including instructions to:
 send a signaling requesting protection of a transmission channel from access by an access point (AP) of the user station; 
 send, to the AP, a frame indicating start of OFDMA transmission by the STA; 
 receive, from the AP, an OFDMA Begin Receive (OBR) frame, wherein the OBR frame is sent by the AP to a plurality of STAs associated with the AP including the user station; 
 send, to the AP, an OFDMA physical layer Protocol Data Unit (PPDU); 
 send a Block Acknowledgement Request (BAR) to the AP; and 
 receive a Block Acknowledgement (BA) from the AP. 
   
     
     
         27 . The user station of  claim 26 , wherein the programming includes further instructions to:
 detect a signaling from the AP, the signaling indicating the AP requesting protection of a transmission channel for downlink transmissions from access by the STAs including the user station;   receive, from the AP an OFDMA PPDU;   receive, from the AP, a BAR, wherein the BAR is sent to the STAs; and   send, to the AP, a BA.