[wake-up] enable CCA for wake up frames (#11024)

This commit enables transmitting wake up frames with CCA enabled. A
build time configuration is added in case the coprocessor doesn't
support the newly added feature skipping CSMA/CA backoff only.

src/core/config/wakeup.h

@@ -117,6 +117,15 @@
 #define OPENTHREAD_CONFIG_WED_RECEIVE_TIME_AFTER 500
 #endif
 
+/**
+ * @def OPENTHREAD_CONFIG_WAKEUP_FRAME_TX_CCA_ENABLE
+ *
+ * Define to 1 to perform CCA before transmitting wake-up frame.
+ */
+#ifndef OPENTHREAD_CONFIG_WAKEUP_FRAME_TX_CCA_ENABLE
+#define OPENTHREAD_CONFIG_WAKEUP_FRAME_TX_CCA_ENABLE 1
+#endif
+
 /**
  * @}
  */

src/core/mac/wakeup_tx_scheduler.cpp

@@ -101,7 +101,7 @@ Mac::TxFrame *WakeupTxScheduler::PrepareWakeupFrame(Mac::TxFrames &aTxFrames)
     VerifyOrExit(frame->GenerateWakeupFrame(Get<Mac::Mac>().GetPanId(), target, source) == kErrorNone, frame = nullptr);
     frame->SetTxDelayBaseTime(static_cast<uint32_t>(Get<Radio>().GetNow()));
     frame->SetTxDelay(radioTxDelay);
-    frame->SetCsmaCaEnabled(false);
+    frame->SetCsmaCaEnabled(kWakeupFrameTxCca);
     frame->SetMaxCsmaBackoffs(0);
     frame->SetMaxFrameRetries(0);
 

src/core/mac/wakeup_tx_scheduler.hpp

@@ -103,6 +103,7 @@ private:
     constexpr static uint8_t  kConnectionRetryInterval = OPENTHREAD_CONFIG_WAKEUP_COORDINATOR_CONNECTION_RETRY_INTERVAL;
     constexpr static uint8_t  kConnectionRetryCount    = OPENTHREAD_CONFIG_WAKEUP_COORDINATOR_CONNECTION_RETRY_COUNT;
     constexpr static uint32_t kWakeupFrameLength       = 54; // Includes SHR
+    constexpr static bool     kWakeupFrameTxCca        = OPENTHREAD_CONFIG_WAKEUP_FRAME_TX_CCA_ENABLE;
     constexpr static uint32_t kParentRequestLength     = 78; // Includes SHR
 
     // Called by the MAC layer when a wake-up frame transmission is about to be started.