fake_trx: implement power measurement emulation

This change introduces a new class named FakePM, which is intended
to generate pseudo-random power levels for base stations and noise
levels inactive frequencies.

Also, there is a new command in BB CTRL, which instructs transceiver
to perform a power measurement on requested frequency. As we work in
virtual Um-interface, a FakePM instance is used to provide some fake
power levels.

Change-Id: If48c12fd0b1ba10e1cf76559b359e17a1256617d

src/target/fake_trx/ctrl_if_bb.py

@@ -29,6 +29,7 @@ class CTRLInterfaceBB(CTRLInterface):
 	trx_started = False
 	rx_freq = None
 	tx_freq = None
+	pm = None
 
 	def __init__(self, remote_addr, remote_port, bind_port):
 		print("[i] Init CTRL interface for BB")
@@ -79,6 +80,19 @@ class CTRLInterfaceBB(CTRLInterface):
 			self.tx_freq = int(request[1]) * 1000
 			return 0
 
+		# Power measurement
+		elif self.verify_cmd(request, "MEASURE", 1):
+			print("[i] Recv MEASURE cmd")
+
+			if self.pm is None:
+				return -1
+
+			# TODO: check freq range
+			meas_freq = int(request[1]) * 1000
+			meas_dbm = str(self.pm.measure(meas_freq))
+
+			return (0, [meas_dbm])
+
 		# Wrong / unknown command
 		else:
 			# We don't care about other commands,

src/target/fake_trx/ctrl_if_bts.py

@@ -29,6 +29,7 @@ class CTRLInterfaceBTS(CTRLInterface):
 	trx_started = False
 	rx_freq = None
 	tx_freq = None
+	pm = None
 
 	def __init__(self, remote_addr, remote_port, bind_port):
 		print("[i] Init CTRL interface for BTS")
@@ -55,6 +56,11 @@ class CTRLInterfaceBTS(CTRLInterface):
 
 			print("[i] Starting transceiver...")
 			self.trx_started = True
+
+			# Power emulation
+			if self.pm is not None:
+				self.pm.add_bts_list([self.tx_freq])
+
 			return 0
 
 		elif self.verify_cmd(request, "POWEROFF", 0):
@@ -62,6 +68,11 @@ class CTRLInterfaceBTS(CTRLInterface):
 
 			print("[i] Stopping transceiver...")
 			self.trx_started = False
+
+			# Power emulation
+			if self.pm is not None:
+				self.pm.del_bts_list([self.tx_freq])
+
 			return 0
 
 		# Tuning Control

src/target/fake_trx/fake_pm.py

@@ -0,0 +1,53 @@
+#!/usr/bin/env python2
+# -*- coding: utf-8 -*-
+
+# Virtual Um-interface (fake transceiver)
+# Power measurement emulation for BB
+#
+# (C) 2017 by Vadim Yanitskiy <axilirator@gmail.com>
+#
+# All Rights Reserved
+#
+# This program is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 2 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License along
+# with this program; if not, write to the Free Software Foundation, Inc.,
+# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+
+from random import randint
+
+class FakePM:
+	# Freq. list for good power level
+	bts_list = []
+
+	def __init__(self, noise_min, noise_max, bts_min, bts_max):
+		# Save power level ranges
+		self.noise_min = noise_min
+		self.noise_max = noise_max
+		self.bts_min = bts_min
+		self.bts_max = bts_max
+
+	def measure(self, bts):
+		if bts in self.bts_list:
+			return randint(self.bts_min, self.bts_max)
+		else:
+			return randint(self.noise_min, self.noise_max)
+
+	def update_bts_list(self, new_list):
+		self.bts_list = new_list
+
+	def add_bts_list(self, add_list):
+		self.bts_list += add_list
+
+	def del_bts_list(self, del_list):
+		for item in del_list:
+			if item in self.bts_list:
+				self.bts_list.remove(item)

src/target/fake_trx/fake_trx.py

@@ -30,6 +30,7 @@ import sys
 from ctrl_if_bts import CTRLInterfaceBTS
 from ctrl_if_bb import CTRLInterfaceBB
 from burst_fwd import BurstForwarder
+from fake_pm import FakePM
 
 from udp_link import UDPLink
 from clck_gen import CLCKGen
@@ -64,6 +65,15 @@ class Application:
 		self.bb_ctrl = CTRLInterfaceBB(self.bb_addr,
 			self.bb_base_port + 101, self.bb_base_port + 1)
 
+		# Power measurement emulation
+		# Noise: -120 .. -105
+		# BTS: -75 .. -50
+		self.pm = FakePM(-120, -105, -75, -50)
+
+		# Share a FakePM instance between both BTS and BB
+		self.bts_ctrl.pm = self.pm
+		self.bb_ctrl.pm = self.pm
+
 		# BTS <-> BB burst forwarding
 		self.bts_data = UDPLink(self.bts_addr,
 			self.bts_base_port + 102, self.bts_base_port + 2)