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#
# Copyright 2005 Free Software Foundation, Inc.
#
# This file is part of GNU Radio
#
# GNU Radio 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, or (at your option)
# any later version.
#
# GNU Radio 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 GNU Radio; see the file COPYING. If not, write to
# the Free Software Foundation, Inc., 51 Franklin Street,
# Boston, MA 02110-1301, USA.
#
_default_bitrate = 500e3
_valid_spbs = (2,3,4,5,6,7)
def _gen_tx_info(converter_rate):
results = []
for spb in _valid_spbs:
for interp in range(16, 512 + 1, 4):
bitrate = converter_rate / interp / spb
results.append((bitrate, spb, interp))
results.sort()
return results
def _gen_rx_info(converter_rate):
results = []
for spb in _valid_spbs:
for decim in range(8, 256 + 1, 2):
bitrate = converter_rate / decim / spb
results.append((bitrate, spb, decim))
results.sort()
return results
def _filter_info(info, samples_per_baud, xrate):
if samples_per_baud is not None:
info = [x for x in info if x[1] == samples_per_baud]
if xrate is not None:
info = [x for x in info if x[2] == xrate]
return info
def _pick_best(target_bitrate, bits_per_symbol, info):
"""
@returns tuple (bitrate, samples_per_baud, interp_rate_or_decim_rate)
"""
if len(info) == 0:
raise RuntimeError, "info is zero length!"
if target_bitrate is None: # return the fastest one
return info[-1]
# convert bit rate to symbol rate
target_symbolrate = target_bitrate / bits_per_symbol
# Find the closest matching symbol rate.
# In the event of a tie, the one with the lowest samples_per_baud wins.
# (We already sorted them, so the first one is the one we take)
best = info[0]
best_delta = abs(target_symbolrate - best[0])
for x in info[1:]:
delta = abs(target_symbolrate - x[0])
if delta < best_delta:
best_delta = delta
best = x
# convert symbol rate back to bit rate
return ((best[0] * bits_per_symbol),) + best[1:]
def _pick_bitrate(bitrate, bits_per_symbol, samples_per_baud,
xrate, converter_rate, gen_info):
"""
@returns tuple (bitrate, samples_per_baud, interp_rate_or_decim_rate)
"""
if not isinstance(bits_per_symbol, int) or bits_per_symbol < 1:
raise ValueError, "bits_per_symbol must be an int >= 1"
if samples_per_baud is not None and xrate is not None: # completely determined
return (float(converter_rate) / xrate / samples_per_baud,
samples_per_baud, xrate)
if bitrate is None and samples_per_baud is None and xrate is None:
bitrate = _default_bitrate
# now we have a target bitrate and possibly an xrate or
# samples_per_baud constraint, but not both of them.
return _pick_best(bitrate, bits_per_symbol,
_filter_info(gen_info(converter_rate), samples_per_baud, xrate))
# ---------------------------------------------------------------------------------------
def pick_tx_bitrate(bitrate, bits_per_symbol, samples_per_baud,
interp_rate, converter_rate=128e6):
"""
Given the 4 input parameters, return at configuration that matches
@param bitrate: desired bitrate or None
@type bitrate: number or None
@param bits_per_symbol: E.g., BPSK -> 1, QPSK -> 2, 8-PSK -> 3
@type bits_per_symbol: integer >= 1
@param samples_per_baud: samples/baud (aka samples/symbol)
@type samples_per_baud: number or None
@param interp_rate: USRP interpolation factor
@type interp_rate: integer or None
@param converter_rate: converter sample rate in Hz
@type converter_rate: number
@returns tuple (bitrate, samples_per_baud, interp_rate)
"""
return _pick_bitrate(bitrate, bits_per_symbol, samples_per_baud,
interp_rate, converter_rate, _gen_tx_info)
def pick_rx_bitrate(bitrate, bits_per_symbol, samples_per_baud,
decim_rate, converter_rate=64e6):
"""
Given the 4 input parameters, return at configuration that matches
@param bitrate: desired bitrate or None
@type bitrate: number or None
@param bits_per_symbol: E.g., BPSK -> 1, QPSK -> 2, 8-PSK -> 3
@type bits_per_symbol: integer >= 1
@param samples_per_baud: samples/baud (aka samples/symbol)
@type samples_per_baud: number or None
@param decim_rate: USRP decimation factor
@type decim_rate: integer or None
@param converter_rate: converter sample rate in Hz
@type converter_rate: number
@returns tuple (bitrate, samples_per_baud, decim_rate)
"""
return _pick_bitrate(bitrate, bits_per_symbol, samples_per_baud,
decim_rate, converter_rate, _gen_rx_info)
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