Changes between Version 2 and Version 3 of 802.11/app_notes/FDD-NoMAC

Timestamp:

Feb 13, 2017, 3:04:39 PM (7 years ago)

Author:

murphpo

Comment:

--

802.11/app_notes/FDD-NoMAC

@@ -63 +63 @@
 }}}
 
+''' Different Channels on RF A/B ''': the reference code tunes all RF interfaces to the same center frequency any time the MAC application requests a new channel. The RF interfaces are tuned in the {{{wlan_mac_low_set_radio_channel(u32 channel)}}} function in {{{wlan_mac_low.c}}}. The {{{channel}}} argument is an 802.11 channel index. This function also enables/disables the Rx PHY DSSS receiver when tuned to a 5 GHz channel, as DSSS transmissions only occur in 2.4 GHz channels.
+
+A fully-general FDD implementation would modify this function to support a channel argument per RF interface. However this app note adopts the simpler scheme of:
+ * Always disable DSSS Rx
+ * Tune RF A to the channel requested by the MAC
+ * Tune RF B to channel 36 (5180 MHz)
+
+The modified {{{wlan_mac_low_set_radio_channel()}}} function is:
+
+{{{#!c
+void wlan_mac_low_set_radio_channel(u32 channel) {
+
+    // Always disable DSSS Rx
+    wlan_phy_DSSS_rx_disable();
+
+        if (wlan_verify_channel(mac_param_chan) == XST_SUCCESS) {
+
+        // Update the framework's global variables for channel/band
+        mac_param_chan = channel;
+
+                if(mac_param_chan <= 14) mac_param_band = RC_24GHZ;
+                else                     mac_param_band = RC_5GHZ;
+
+        // Adjust Tx baseband gain when switching to 5GHz channels; this adjustment makes
+        //  the actual Tx power set via the Tx VGA more accurate
+            if(channel >= 36) radio_controller_setRadioParam(RC_BASEADDR, RC_RF_A, RC_PARAMID_TXGAIN_BB, 3);
+            else              radio_controller_setRadioParam(RC_BASEADDR, RC_RF_A, RC_PARAMID_TXGAIN_BB, 1);
+
+        // Tune the RF A interface to the requested channel
+                radio_controller_setCenterFrequency(RC_BASEADDR, RC_RF_A, mac_param_band, wlan_mac_low_wlan_chan_to_rc_chan(mac_param_chan));
+
+        // Tune the RF B interface to channel 36
+        radio_controller_setRadioParam(RC_BASEADDR, RC_RF_B, RC_PARAMID_TXGAIN_BB, 3);
+        radio_controller_setCenterFrequency(RC_BASEADDR, RC_RF_B, mac_param_band, wlan_mac_low_wlan_chan_to_rc_chan(36));
+        } else {
+                xil_printf("Invalid channel selection %d\n", mac_param_chan);
+        }
+}
+}}}
+
+
+
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