Changes between Version 6 and Version 7 of 802.11/MAC/Lower/DCF

Timestamp:

Aug 7, 2015, 1:44:47 PM (9 years ago)

Author:

chunter

Comment:

--

802.11/MAC/Lower/DCF

@@ -120 +120 @@
 Pseudocode:
 {{{
+if( RA address is to me )
+        switch( packet type )
+                case ACK:
+                        wait for FCS
+                        if (FCS good )
+                                raise corresponding return flag
+                case CTS:
+                        wait for FCS status
+                        if( FCS good )
+                                configure MAC support core to send MPDU after SIFS interval
+                                raise corresponding return flag
 
 }}}
+
+Upon exiting the {{{frame_transmit()}}} context, execution returns to the MAC Low Framework, where an IPC message is sent to CPU_HIGH indicating that the MPDU transmission is done.
 
 
@@ -127 +140 @@
 
 [[Image(wiki:802.11/files:mpdu_rx.png, width=800)]]
+
+MPDU reception is considerably simpler than transmission. The DCF software is responsible for polling the PHY Rx by calling the {{{wlan_mac_low_poll_frame_rx()}}} function in the MAC Low Framework.
+
+'''P1:'''
+
+The {{{wlan_mac_low_poll_frame_rx()}}} function reads the status registers from the PHY and converts that information into a {{{phy_rx_details}}} structure that contains the following:
+* the PHY mode that was used (i.e. OFDM or DSSS)
+* the PHY rate that was used
+* the frame length decoded from the SIGNAL field
+
+If the reception is valid and supported, the framework calls the {{{frame_rx_callback}}} function.
+
+Pseudocode:
+{{{
+read the MAC status register
+
+if( the Rx PHY is currently active OR the PHY is blocked after a reception )
+        if( the PHY is using the DSSS subsystem )
+                update the phy_rx_details struct to reflect the DSSS mode and rate
+                call frame_rx_callback()
+        else
+                wait for valid OFDM Rx params from the PHY
+                if( params indicate a supported mode )
+                        update the phy_rx_details with Rx params
+                        call frame_rx_callback()
+
+return status_variable the return of the call to frame_rx_callback()
+        
+}}}
+
+----
+
+In the DCF, the {{{frame_rx_callback()}}} is attached to the {{{frame_receive()}}} function. In the above MPDU transmission state, we have already seen some executions of this function to deal with the receptions of ACK and CTS frames. Independently of these actions, the {{{frame_receive()}}} function needs to pass receptions up to CPU_HIGH