When 4 samples-per-symbol operation is selected, replace the
existing pulse approximation, which becomes inaccurate with
non-unit oversampling, with the primary pulse, C0, from the
Laurent linear pulse approximation.
Pierre Laurent, "Exact and Approximate Construction of Digital Phase
Modulations by Superposition of Amplitude Modulated Pulses", IEEE
Transactions of Communications, Vol. 34, No. 2, Feb 1986.
Octave pulse generation code for the first three pulses of the
linear approximation are included.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6736 19bc5d8c-e614-43d4-8b26-e1612bc8e597
The adaptive energy threshold gating suffers a near-far problem
at certain gain levels. This is due to exponential threshold
raising, but linear decreases. A large signal level followed by
a period low signal level causes (comparatively) weak signals to
go undetected. Additionally, the algorithm performs differently
at multiple RF gain levels.
This patch switches solely to correlation based gating for burst
detection. The main computational load with this approach is
sub-sample width peak interpolation, which we disable for intial
detection and run after threshold passing.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6735 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Replace the polyphase filter and resampler with a separate
implementation using SSE enabled convolution. The USRP2 (including
derived devices N200, N210) are the only supported devices that
require sample rate conversion, so set the default resampling
parameters for the 100 MHz FPGA clock. This changes the previous
resampling ratios.
270.833 kHz -> 400 kHz (65 / 96)
270.833 kHz -> 390.625 kHz (52 / 75)
The new resampling factor uses a USRP resampling factor of 256
instead of 250. On the device, this allows two halfband filters to
be used rather than one. The end result is reduced distortial and
aliasing effecits from CIC filter rolloff.
B100 and USRP1 will no be supported at 400 ksps with these changes.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6733 19bc5d8c-e614-43d4-8b26-e1612bc8e597
This large patch replaced the convolve() call with an SSE vector
enabled version. The lower C and SSE intrinsic based code operates
on fixed and aligned vectors for the filter taps. The storage format
of interleaved I/Q for both complex and real vectors is maintained.
SSE filter tap values must:
1. Start 16-byte aligned
2. Number with a multiple of 4 between 4 and 20 for real taps
3. Number with a multiple of 4 for complex taps
Non-compliant values will fall back to non-SSE usage. Fixed length
iterators mean that head and tail cases may require reallocation of
the input vector, which is automatically handled by the upper C++
interface.
Other calls are affected by these changes and adjusted or rewritten
accordingly. The underlying algorithms, however, are unchanged.
generateGSMPulse()
analyzeTrafficBurst()
detectRACHBurst()
Intel SSE configuration is automatically detected and configured at
build time with Autoconf macros.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6732 19bc5d8c-e614-43d4-8b26-e1612bc8e597
There is no temporal dependency on when the RACH sequence is generated,
so there is no need for transceiver to create it in response to a
command from GSM core. If we power on the transceiver, we will need
the RACH sequence, so just allocate it during initialization.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6731 19bc5d8c-e614-43d4-8b26-e1612bc8e597
The only logging outputs in the the signal processing library
are debug lines that generate copious amounts of output while
providing little useful information to the user. The relevant
information (time-of-arrival, channel gains, etc.) can and
should be logged from transceiver instance itself.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6730 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Add destructor calls so we can avoid the nested vector deallocations.
Also remove the unnecessary pointer NULL checks prior to destruction.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6729 19bc5d8c-e614-43d4-8b26-e1612bc8e597
There is no reason expose the pulse shaping filter outside of the
signal processing calls. The main transceiver object makes no use
of the filter and there's no reason to pass it around.
Initialize the pulse shape with the signal processing library, and
maintain an internal static member like many of the other library
variables. Similarly destroy the object when the library is closed.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6728 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Because repeatedly typing mSamplesPerSymbol is giving me
carpal tunnel syndrome. Replace with the much shorter,
easier to type, and just as clear name of 'sps'.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@6727 19bc5d8c-e614-43d4-8b26-e1612bc8e597
The correlation starting point for normal burst training sequence
calculation should be a scaled value of the same symbol regardless
of the samples-per-symbol used. Use of 2 samples-per-symbols double
the index values, but yields the following outputs, which results
in a late time-of-arrival value at the output of the correlation.
This patch modifies the parameter calculation accordingly.
1 sps parameters
maxTOA = 3
spanTOA = 5;
startIx = 61;
endIx = 87;
windowLen = 26;
corrLen = 7;
2 sps parameters (errant case)
maxTOA = 6;
spanTOA = 10;
startIx = 112;
endIx = 184;
windowLen = 72;
corrLen =13;
2 sps parameters (corrected)
maxTOA = 6;
spanTOA = 10;
startIx = 122;
endIx = 174;
windowLen = 52;
corrLen =13;
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@5183 19bc5d8c-e614-43d4-8b26-e1612bc8e597
With transceiver integration, the resampling filter files were
dropped. This created a working resampling implementation for
the USRP2 / N200, but with spectrum irregulaties that likely
caused issues at longer range operation. Simply reinsert the
filter files and modify the filter initialization to use them.
Signed-off-by: Thomas Tsou <ttsou@vt.edu>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@2689 19bc5d8c-e614-43d4-8b26-e1612bc8e597
