TSCH: add option to not to turn off radio during active TSCH timeslots

core/net/mac/tsch/tsch-conf.h

@@ -184,4 +184,11 @@
 #define TSCH_HW_FRAME_FILTERING 1
 #endif /* TSCH_CONF_HW_FRAME_FILTERING */
 
+/* Keep radio always on within TSCH timeslot (1) or turn it off between packet and ACK? (0) */
+#ifdef TSCH_CONF_RADIO_ON_DURING_TIMESLOT
+#define TSCH_RADIO_ON_DURING_TIMESLOT TSCH_CONF_RADIO_ON_DURING_TIMESLOT
+#else
+#define TSCH_RADIO_ON_DURING_TIMESLOT 0
+#endif
+
 #endif /* __TSCH_CONF_H__ */

core/net/mac/tsch/tsch-slot-operation.c

@@ -36,6 +36,7 @@
  * \author
  *         Simon Duquennoy <simonduq@sics.se>
  *         Beshr Al Nahas <beshr@sics.se>
+ *         Atis Elsts <atis.elsts@bristol.ac.uk>
  *
  */
 
@@ -109,6 +110,18 @@
 #define RTIMER_GUARD 2u
 #endif
 
+enum tsch_radio_state_on_cmd {
+  TSCH_RADIO_CMD_ON_START_OF_TIMESLOT,
+  TSCH_RADIO_CMD_ON_WITHIN_TIMESLOT,
+  TSCH_RADIO_CMD_ON_FORCE,
+};
+
+enum tsch_radio_state_off_cmd {
+  TSCH_RADIO_CMD_OFF_END_OF_TIMESLOT,
+  TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT,
+  TSCH_RADIO_CMD_OFF_FORCE,
+};
+
 /* A ringbuf storing outgoing packets after they were dequeued.
  * Will be processed layer by tsch_tx_process_pending */
 struct ringbufindex dequeued_ringbuf;
@@ -370,6 +383,68 @@ update_neighbor_state(struct tsch_neighbor *n, struct tsch_packet *p,
   return in_queue;
 }
 /*---------------------------------------------------------------------------*/
+/**
+ * This function turns on the radio. Its semantics is dependent on
+ * the value of TSCH_RADIO_ON_DURING_TIMESLOT constant:
+ * - if enabled, the radio is turned on at the start of the slot
+ * - if disabled, the radio is turned on within the slot,
+ *   directly before the packet Rx guard time and ACK Rx guard time.
+ */
+static void
+tsch_radio_on(enum tsch_radio_state_on_cmd command)
+{
+  int do_it = 0;
+  switch(command) {
+  case TSCH_RADIO_CMD_ON_START_OF_TIMESLOT:
+    if(TSCH_RADIO_ON_DURING_TIMESLOT) {
+      do_it = 1;
+    }
+    break;
+  case TSCH_RADIO_CMD_ON_WITHIN_TIMESLOT:
+    if(!TSCH_RADIO_ON_DURING_TIMESLOT) {
+      do_it = 1;
+    }
+    break;
+  case TSCH_RADIO_CMD_ON_FORCE:
+    do_it = 1;
+    break;
+  }
+  if(do_it) {
+    NETSTACK_RADIO.on();
+  }
+}
+/*---------------------------------------------------------------------------*/
+/**
+ * This function turns off the radio. In the same way as for tsch_radio_on(),
+ * it depends on the value of TSCH_RADIO_ON_DURING_TIMESLOT constant:
+ * - if enabled, the radio is turned off at the end of the slot
+ * - if disabled, the radio is turned off within the slot,
+ *   directly after Tx'ing or Rx'ing a packet or Tx'ing an ACK.
+ */
+static void
+tsch_radio_off(enum tsch_radio_state_off_cmd command)
+{
+  int do_it = 0;
+  switch(command) {
+  case TSCH_RADIO_CMD_OFF_END_OF_TIMESLOT:
+    if(TSCH_RADIO_ON_DURING_TIMESLOT) {
+      do_it = 1;
+    }
+    break;
+  case TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT:
+    if(!TSCH_RADIO_ON_DURING_TIMESLOT) {
+      do_it = 1;
+    }
+    break;
+  case TSCH_RADIO_CMD_OFF_FORCE:
+    do_it = 1;
+    break;
+  }
+  if(do_it) {
+    NETSTACK_RADIO.off();
+  }
+}
+/*---------------------------------------------------------------------------*/
 static
 PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
 {
@@ -456,7 +531,7 @@ PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
         /* delay before CCA */
         TSCH_SCHEDULE_AND_YIELD(pt, t, current_slot_start, TS_CCA_OFFSET, "cca");
         TSCH_DEBUG_TX_EVENT();
-        NETSTACK_RADIO.on();
+        tsch_radio_on(TSCH_RADIO_CMD_ON_WITHIN_TIMESLOT);
         /* CCA */
         BUSYWAIT_UNTIL_ABS(!(cca_status |= NETSTACK_RADIO.channel_clear()),
                            current_slot_start, TS_CCA_OFFSET + TS_CCA);
@@ -480,7 +555,7 @@ PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
           /* limit tx_time to its max value */
           tx_duration = MIN(tx_duration, tsch_timing[tsch_ts_max_tx]);
           /* turn tadio off -- will turn on again to wait for ACK if needed */
-          NETSTACK_RADIO.off();
+          tsch_radio_off(TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT);
 
           if(mac_tx_status == RADIO_TX_OK) {
             if(!is_broadcast) {
@@ -502,7 +577,7 @@ PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
               TSCH_SCHEDULE_AND_YIELD(pt, t, current_slot_start,
                   tsch_timing[tsch_ts_tx_offset] + tx_duration + tsch_timing[tsch_ts_rx_ack_delay] - RADIO_DELAY_BEFORE_RX, "TxBeforeAck");
               TSCH_DEBUG_TX_EVENT();
-              NETSTACK_RADIO.on();
+              tsch_radio_on(TSCH_RADIO_CMD_ON_WITHIN_TIMESLOT);
               /* Wait for ACK to come */
               BUSYWAIT_UNTIL_ABS(NETSTACK_RADIO.receiving_packet(),
                   tx_start_time, tx_duration + tsch_timing[tsch_ts_rx_ack_delay] + tsch_timing[tsch_ts_ack_wait]);
@@ -514,7 +589,7 @@ PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
               BUSYWAIT_UNTIL_ABS(!NETSTACK_RADIO.receiving_packet(),
                                  ack_start_time, tsch_timing[tsch_ts_max_ack]);
               TSCH_DEBUG_TX_EVENT();
-              NETSTACK_RADIO.off();
+              tsch_radio_off(TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT);
 
 #if TSCH_HW_FRAME_FILTERING
               /* Leaving promiscuous mode */
@@ -588,6 +663,8 @@ PT_THREAD(tsch_tx_slot(struct pt *pt, struct rtimer *t))
       }
     }
 
+    tsch_radio_off(TSCH_RADIO_CMD_OFF_END_OF_TIMESLOT);
+
     current_packet->transmissions++;
     current_packet->ret = mac_tx_status;
 
@@ -671,27 +748,26 @@ PT_THREAD(tsch_rx_slot(struct pt *pt, struct rtimer *t))
     TSCH_DEBUG_RX_EVENT();
 
     /* Start radio for at least guard time */
-    NETSTACK_RADIO.on();
+    tsch_radio_on(TSCH_RADIO_CMD_ON_WITHIN_TIMESLOT);
-    packet_seen = NETSTACK_RADIO.receiving_packet();
+    packet_seen = NETSTACK_RADIO.receiving_packet() || NETSTACK_RADIO.pending_packet();
     if(!packet_seen) {
       /* Check if receiving within guard time */
       BUSYWAIT_UNTIL_ABS((packet_seen = NETSTACK_RADIO.receiving_packet()),
           current_slot_start, tsch_timing[tsch_ts_rx_offset] + tsch_timing[tsch_ts_rx_wait]);
     }
-    if(packet_seen) {
+    if(!packet_seen) {
+      /* no packets on air */
+      tsch_radio_off(TSCH_RADIO_CMD_OFF_FORCE);
+    } else {
       TSCH_DEBUG_RX_EVENT();
       /* Save packet timestamp */
       rx_start_time = RTIMER_NOW() - RADIO_DELAY_BEFORE_DETECT;
-    }
+
-    if(!NETSTACK_RADIO.receiving_packet() && !NETSTACK_RADIO.pending_packet()) {
-      NETSTACK_RADIO.off();
-      /* no packets on air */
-    } else {
       /* Wait until packet is received, turn radio off */
       BUSYWAIT_UNTIL_ABS(!NETSTACK_RADIO.receiving_packet(),
           current_slot_start, tsch_timing[tsch_ts_rx_offset] + tsch_timing[tsch_ts_rx_wait] + tsch_timing[tsch_ts_max_tx]);
       TSCH_DEBUG_RX_EVENT();
-      NETSTACK_RADIO.off();
+      tsch_radio_off(TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT);
 
 #if TSCH_RESYNC_WITH_SFD_TIMESTAMPS
       /* At the end of the reception, get an more accurate estimate of SFD arrival time */
@@ -784,7 +860,7 @@ PT_THREAD(tsch_rx_slot(struct pt *pt, struct rtimer *t))
                   packet_duration + tsch_timing[tsch_ts_tx_ack_delay] - RADIO_DELAY_BEFORE_TX, "RxBeforeAck");
               TSCH_DEBUG_RX_EVENT();
               NETSTACK_RADIO.transmit(ack_len);
-              NETSTACK_RADIO.off();
+              tsch_radio_off(TSCH_RADIO_CMD_OFF_WITHIN_TIMESLOT);
             }
 
             /* If the sender is a time source, proceed to clock drift compensation */
@@ -820,6 +896,8 @@ PT_THREAD(tsch_rx_slot(struct pt *pt, struct rtimer *t))
           process_poll(&tsch_pending_events_process);
         }
       }
+
+      tsch_radio_off(TSCH_RADIO_CMD_OFF_END_OF_TIMESLOT);
     }
 
     if(input_queue_drop != 0) {
@@ -860,8 +938,12 @@ PT_THREAD(tsch_slot_operation(struct rtimer *t, void *ptr))
 
     } else {
       uint8_t current_channel;
+      int is_active_slot;
       TSCH_DEBUG_SLOT_START();
       tsch_in_slot_operation = 1;
+      /* Reset drift correction */
+      drift_correction = 0;
+      is_drift_correction_used = 0;
       /* Get a packet ready to be sent */
       current_packet = get_packet_and_neighbor_for_link(current_link, &current_neighbor);
       /* There is no packet to send, and this link does not have Rx flag. Instead of doing
@@ -870,12 +952,13 @@ PT_THREAD(tsch_slot_operation(struct rtimer *t, void *ptr))
         current_link = backup_link;
         current_packet = get_packet_and_neighbor_for_link(current_link, &current_neighbor);
       }
+      is_active_slot = current_packet != NULL || (current_link->link_options & LINK_OPTION_RX);
+      if(is_active_slot) {
         /* Hop channel */
         current_channel = tsch_calculate_channel(&current_asn, current_link->channel_offset);
         NETSTACK_RADIO.set_value(RADIO_PARAM_CHANNEL, current_channel);
-      /* Reset drift correction */
+        /* Turn the radio on already here if configured so; necessary for radios with slow startup */
-      drift_correction = 0;
+        tsch_radio_on(TSCH_RADIO_CMD_ON_START_OF_TIMESLOT);
-      is_drift_correction_used = 0;
         /* Decide whether it is a TX/RX/IDLE or OFF slot */
         /* Actual slot operation */
         if(current_packet != NULL) {
@@ -886,11 +969,12 @@ PT_THREAD(tsch_slot_operation(struct rtimer *t, void *ptr))
            **/
           static struct pt slot_tx_pt;
           PT_SPAWN(&slot_operation_pt, &slot_tx_pt, tsch_tx_slot(&slot_tx_pt, t));
-      } else if((current_link->link_options & LINK_OPTION_RX)) {
+        } else {
           /* Listen */
           static struct pt slot_rx_pt;
           PT_SPAWN(&slot_operation_pt, &slot_rx_pt, tsch_rx_slot(&slot_rx_pt, t));
         }
+      }
       TSCH_DEBUG_SLOT_END();
     }