1 files changed, 143 insertions, 0 deletions
diff --git a/gnuradio-examples/python/ofdm/pick_bitrate.py b/gnuradio-examples/python/ofdm/pick_bitrate.py
new file mode 100644
index 000000000..42aefa94e
--- /dev/null
+++ b/gnuradio-examples/python/ofdm/pick_bitrate.py
@@ -0,0 +1,143 @@
+#
+# Copyright 2005,2006 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_samples_per_symbol = (2,3,4,5,6,7)
+
+def _gen_tx_info(converter_rate):
+    results = []
+    for samples_per_symbol in _valid_samples_per_symbol:
+        for interp in range(16, 512 + 1, 4):
+            bitrate = converter_rate / interp / samples_per_symbol
+            results.append((bitrate, samples_per_symbol, interp))
+    results.sort()
+    return results
+
+def _gen_rx_info(converter_rate):
+    results = []
+    for samples_per_symbol in _valid_samples_per_symbol:
+        for decim in range(8, 256 + 1, 2):
+            bitrate = converter_rate / decim / samples_per_symbol
+            results.append((bitrate, samples_per_symbol, decim))
+    results.sort()
+    return results
+    
+def _filter_info(info, samples_per_symbol, xrate):
+    if samples_per_symbol is not None:
+        info = [x for x in info if x[1] == samples_per_symbol]
+    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_symbol, 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_symbol 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_symbol,
+                  xrate, converter_rate, gen_info):
+    """
+    @returns tuple (bitrate, samples_per_symbol, 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_symbol is not None and xrate is not None:  # completely determined
+        return (float(converter_rate) / xrate / samples_per_symbol,
+                samples_per_symbol, xrate)
+
+    if bitrate is None and samples_per_symbol is None and xrate is None:
+        bitrate = _default_bitrate
+
+    # now we have a target bitrate and possibly an xrate or
+    # samples_per_symbol constraint, but not both of them.
+
+    return _pick_best(bitrate, bits_per_symbol,
+                      _filter_info(gen_info(converter_rate), samples_per_symbol, xrate))
+    
+# ---------------------------------------------------------------------------------------
+
+def pick_tx_bitrate(bitrate, bits_per_symbol, samples_per_symbol,
+                    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_symbol: samples/baud (aka samples/symbol)
+    @type samples_per_symbol: 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_symbol, interp_rate)
+    """
+    return _pick_bitrate(bitrate, bits_per_symbol, samples_per_symbol,
+                         interp_rate, converter_rate, _gen_tx_info)
+
+
+def pick_rx_bitrate(bitrate, bits_per_symbol, samples_per_symbol,
+                    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_symbol: samples/baud (aka samples/symbol)
+    @type samples_per_symbol: 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_symbol, decim_rate)
+    """
+    return _pick_bitrate(bitrate, bits_per_symbol, samples_per_symbol,
+                         decim_rate, converter_rate, _gen_rx_info)