trx_toolkit/fake_trx: introduce basic path loss simulation

This change introduces a couple of new CTRL commands for path loss
simulation, in particular a possibility to drop some amount of
bursts according to some TDMA frame period, separately for both
Uplink and Downlink directions.

Examples:

  FAKE_DROP 4 - drop 4 consistent (period=1) bursts,
  FAKE_DROP 16 2 - drop 16 even bursts (period=2).

Change-Id: Ib210138a03e2377c79875a4ff2f2bb58a43cfa46
Related: OS#3428

src/target/trx_toolkit/burst_fwd.py

@@ -66,6 +66,15 @@ class BurstForwarder:
 	rssi_dl_threshold = 10
 	rssi_ul_threshold = 5
 
+	# Path loss simulation: DL/UL burst dropping
+	# Indicates how many bursts should be dropped
+	# and which dropping period is used. By default,
+	# period is 1, i.e. every burst (fn % 1 is always 0)
+	burst_dl_drop_amount = 0
+	burst_ul_drop_amount = 0
+	burst_dl_drop_period = 1
+	burst_ul_drop_period = 1
+
 	def __init__(self, bts_link, bb_link):
 		self.bts_link = bts_link
 		self.bb_link = bb_link
@@ -131,6 +140,30 @@ class BurstForwarder:
 		# Generate a random RSSI value
 		return random.randint(rssi_min, rssi_max)
 
+	# DL path loss simulation
+	def path_loss_sim_dl(self, msg):
+		# Burst dropping
+		if self.burst_dl_drop_amount > 0:
+			if msg.fn % self.burst_dl_drop_period == 0:
+				print("[~] Simulation: dropping DL burst (fn=%u %% %u == 0)"
+					% (msg.fn, self.burst_dl_drop_period))
+				self.burst_dl_drop_amount -= 1
+				return None
+
+		return msg
+
+	# UL path loss simulation
+	def path_loss_sim_ul(self, msg):
+		# Burst dropping
+		if self.burst_ul_drop_amount > 0:
+			if msg.fn % self.burst_ul_drop_period == 0:
+				print("[~] Simulation: dropping UL burst (fn=%u %% %u == 0)"
+					% (msg.fn, self.burst_ul_drop_period))
+				self.burst_ul_drop_amount -= 1
+				return None
+
+		return msg
+
 	# DL burst preprocessing
 	def preprocess_dl_burst(self, msg):
 		# Calculate both RSSI and ToA values
@@ -180,6 +213,11 @@ class BurstForwarder:
 		if msg.tn != self.ts_pass:
 			return None
 
+		# Path loss simulation
+		msg = self.path_loss_sim_dl(msg)
+		if msg is None:
+			return None
+
 		# Burst preprocessing
 		self.preprocess_dl_burst(msg)
 
@@ -211,6 +249,11 @@ class BurstForwarder:
 		if msg is None:
 			return None
 
+		# Path loss simulation
+		msg = self.path_loss_sim_ul(msg)
+		if msg is None:
+			return None
+
 		# Burst preprocessing
 		self.preprocess_ul_burst(msg)
 

src/target/trx_toolkit/ctrl_if_bb.py

@@ -150,6 +150,46 @@ class CTRLInterfaceBB(CTRLInterface):
 
 			return 0
 
+		# Path loss simulation for UL: burst dropping
+		# Syntax: CMD FAKE_DROP <AMOUNT>
+		# Dropping pattern: fn % 1 == 0
+		elif self.verify_cmd(request, "FAKE_DROP", 1):
+			print("[i] Recv FAKE_DROP cmd")
+
+			# Parse / validate amount of bursts
+			num = int(request[1])
+			if num < 0:
+				print("[!] FAKE_DROP amount shall not be negative")
+				return -1
+
+			self.burst_fwd.burst_ul_drop_amount = num
+			self.burst_fwd.burst_ul_drop_period = 1
+
+			return 0
+
+		# Path loss simulation for UL: burst dropping
+		# Syntax: CMD FAKE_DROP <AMOUNT> <FN_PERIOD>
+		# Dropping pattern: fn % period == 0
+		elif self.verify_cmd(request, "FAKE_DROP", 2):
+			print("[i] Recv FAKE_DROP cmd")
+
+			# Parse / validate amount of bursts
+			num = int(request[1])
+			if num < 0:
+				print("[!] FAKE_DROP amount shall not be negative")
+				return -1
+
+			# Parse / validate period
+			period = int(request[2])
+			if period <= 0:
+				print("[!] FAKE_DROP period shall be greater than zero")
+				return -1
+
+			self.burst_fwd.burst_ul_drop_amount = num
+			self.burst_fwd.burst_ul_drop_period = period
+
+			return 0
+
 		# Wrong / unknown command
 		else:
 			# We don't care about other commands,

src/target/trx_toolkit/ctrl_if_bts.py

@@ -118,6 +118,46 @@ class CTRLInterfaceBTS(CTRLInterface):
 
 			return 0
 
+		# Path loss simulation for DL: burst dropping
+		# Syntax: CMD FAKE_DROP <AMOUNT>
+		# Dropping pattern: fn % 1 == 0
+		elif self.verify_cmd(request, "FAKE_DROP", 1):
+			print("[i] Recv FAKE_DROP cmd")
+
+			# Parse / validate amount of bursts
+			num = int(request[1])
+			if num < 0:
+				print("[!] FAKE_DROP amount shall not be negative")
+				return -1
+
+			self.burst_fwd.burst_dl_drop_amount = num
+			self.burst_fwd.burst_dl_drop_period = 1
+
+			return 0
+
+		# Path loss simulation for DL: burst dropping
+		# Syntax: CMD FAKE_DROP <AMOUNT> <FN_PERIOD>
+		# Dropping pattern: fn % period == 0
+		elif self.verify_cmd(request, "FAKE_DROP", 2):
+			print("[i] Recv FAKE_DROP cmd")
+
+			# Parse / validate amount of bursts
+			num = int(request[1])
+			if num < 0:
+				print("[!] FAKE_DROP amount shall not be negative")
+				return -1
+
+			# Parse / validate period
+			period = int(request[2])
+			if period <= 0:
+				print("[!] FAKE_DROP period shall be greater than zero")
+				return -1
+
+			self.burst_fwd.burst_dl_drop_amount = num
+			self.burst_fwd.burst_dl_drop_period = period
+
+			return 0
+
 		# Wrong / unknown command
 		else:
 			# We don't care about other commands,