Implemented adaptive CSMA scheme

Config.h

@@ -290,7 +290,10 @@
 	// MCU independent configuration parameters
 	const long serial_baudrate  = 115200;
 	const int lora_rx_turnaround_ms = 50;
-	const int csma_slot_ms = lora_rx_turnaround_ms;
+	uint8_t csma_p = 0;
+	float csma_p_min = 0.1;
+	float csma_p_max = 0.8;
+	int csma_slot_ms = lora_rx_turnaround_ms;
 
 	// SX1276 RSSI offset to get dBm value from
 	// packet RSSI register
@@ -373,8 +376,9 @@
 	bool dcd                  = false;
 	bool dcd_led              = false;
 	bool dcd_waiting          = false;
+	long dcd_wait_until       = 0;
 	uint16_t dcd_count        = 0;
-	uint16_t dcd_threshold    = 15;
+	uint16_t dcd_threshold    = 6;
 
 	uint32_t status_interval_ms = STATUS_INTERVAL_MS;
 	uint32_t last_status_update = 0;

Makefile

@@ -99,11 +99,11 @@ upload-mega2560:
 	arduino-cli upload -p /dev/ttyACM0 --fqbn arduino:avr:mega
 
 upload-tbeam:
-	arduino-cli upload -p /dev/ttyUSB1 --fqbn esp32:esp32:t-beam
+	arduino-cli upload -p /dev/ttyACM0 --fqbn esp32:esp32:t-beam
 	@sleep 1
-	rnodeconf /dev/ttyUSB1 --firmware-hash $$(./partition_hashes ./build/esp32.esp32.t-beam/RNode_Firmware.ino.bin)
+	rnodeconf /dev/ttyACM0 --firmware-hash $$(./partition_hashes ./build/esp32.esp32.t-beam/RNode_Firmware.ino.bin)
 	@sleep 3
-	python ./Release/esptool/esptool.py --chip esp32 --port /dev/ttyUSB1 --baud 921600 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 80m --flash_size 4MB 0x210000 ./Release/console_image.bin
+	python ./Release/esptool/esptool.py --chip esp32 --port /dev/ttyACM0 --baud 921600 --before default_reset --after hard_reset write_flash -z --flash_mode dio --flash_freq 80m --flash_size 4MB 0x210000 ./Release/console_image.bin
 
 upload-lora32_v10:
 	arduino-cli upload -p /dev/ttyUSB0 --fqbn esp32:esp32:ttgo-lora32

RNode_Firmware.ino

@@ -373,6 +373,7 @@ void flushQueue(void) {
   if (!queue_flushing) {
     queue_flushing = true;
 
+    led_tx_on();
     uint16_t processed = 0;
 
     #if MCU_VARIANT == MCU_ESP32
@@ -394,6 +395,9 @@ void flushQueue(void) {
         processed++;
       }
     }
+
+    lora_receive();
+    led_tx_off();
   }
 
   queue_height = 0;
@@ -439,6 +443,7 @@ void update_airtime() {
     }
     longterm_channel_util = (float)longterm_channel_util_sum/(float)AIRTIME_BINS;
 
+    update_csma_p();
     kiss_indicate_channel_stats();
   #endif
 }
@@ -446,7 +451,6 @@ void update_airtime() {
 void transmit(uint16_t size) {
   if (radio_online) {
     if (!promisc) {
-      led_tx_on();
       uint16_t  written = 0;
       uint8_t header  = random(256) & 0xF0;
 
@@ -471,9 +475,6 @@ void transmit(uint16_t size) {
       }
 
       LoRa.endPacket(); add_airtime(written);
-      led_tx_off();
-
-      lora_receive();
     } else {
       // In promiscuous mode, we only send out
       // plain raw LoRa packets with a maximum
@@ -500,9 +501,6 @@ void transmit(uint16_t size) {
         written++;
       }
       LoRa.endPacket(); add_airtime(written);
-      led_tx_off();
-
-      lora_receive();
     }
   } else {
     kiss_indicate_error(ERROR_TXFAILED);
@@ -934,7 +932,7 @@ void updateModemStatus() {
     }
   } else {
     if (dcd_count > 0) {
-      dcd_count--;
+      dcd_count = 0;
     } else {
       dcd_led = false;
     }
@@ -1099,6 +1097,13 @@ void validate_status() {
   }
 }
 
+#define _e 2.71828183
+#define _S 10.0
+float csma_slope(float u) { return (pow(_e,_S*u-_S/2.0))/(pow(_e,_S*u-_S/2.0)+1.0); }
+void update_csma_p() {
+  csma_p = (uint8_t)((1.0-(csma_p_min+(csma_p_max-csma_p_min)*csma_slope(airtime)))*255.0);
+}
+
 void loop() {
   if (radio_online) {
     checkModemStatus();
@@ -1121,6 +1126,25 @@ void loop() {
 
     if (!airtime_lock) {
       if (queue_height > 0) {
+        #if MCU_VARIANT == MCU_ESP32
+
+          if (dcd_waiting && (millis() >= dcd_wait_until)) { dcd_waiting = false; }
+          if (!dcd_waiting) {
+            updateModemStatus();
+            long check_time = millis();
+
+            if (!dcd) {
+              uint8_t csma_r = (uint8_t)random(256);
+              if (csma_p >= csma_r) {
+                flushQueue();
+              } else {
+                dcd_waiting = true;
+                dcd_wait_until = check_time+csma_slot_ms;
+              }
+            }
+          }
+          
+        #else
           if (!dcd_waiting) updateModemStatus();
 
           if (!dcd && !dcd_led) {
@@ -1136,6 +1160,7 @@ void loop() {
           } else {
             dcd_waiting = true;
           }
+        #endif
       }
     }
   

Utilities.h

@@ -912,6 +912,7 @@ void updateBitrate() {
 			lora_symbol_time_ms = (1.0/lora_symbol_rate)*1000.0;
 			lora_bitrate = (uint32_t)(lora_sf * ( (4.0/(float)lora_cr) / ((float)(pow(2, lora_sf))/((float)lora_bw/1000.0)) ) * 1000.0);
 			lora_us_per_byte = 1000000.0/((float)lora_bitrate/8.0);
+			csma_slot_ms = lora_symbol_time_ms*10;
 		} else {
 			lora_bitrate = 0;
 		}