This patch applies oversampling, when selected with 4 sps,
to the downlink only, while running the receiver with
minimal sampling at 1 sps. These split sample rates allow
us to run a highly accurate downlink signal with minimal
distortion, while keeping receive path channel filtering
on the FPGA.
Without this patch, we oversample the receive path and
require a steep receive filter to get similar adjacent
channel suppression as the FPGA halfband / CIC filter
combination, which comes with a high computational cost.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
This requires an additional memcpy() on the signal vector
constructor, but allows the interpolation filter to use
SSE optimzationed convolution.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
This patch primarily addresses observed repeated overrun
conditions in embedded environments - namely ARM.
The heartbeat of the transceiver is derived from the receive
sample stream, which drives the main GSM clock. Detach the
transmit thread from the receive loop to avoid interfering with
the receive I/O, which is sensitive to overrun conditions if
pull process is interrupted.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Start the correlation search window at 4 symbols before
the expected correlation peak. End the search at 10
symbols and 4 + maximum expected delay for RACH and TSC
bursts respectively.
This change lowers receive side cpu utilization while
maintaining reasonable timing jitter and accuracy tolerance.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
This patch only applies to resampling use at 4 samples-per-symbol.
By extention that means only USRP2 / N2xx devices are affected.
At 4 samples-per-symbol we restrict output bandwidth to roughly
roughly 700 MHz, which combined with the 2 pulse Laurent
approximation yields < 0.5 degrees of RMS phase error at the
resampler output.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Set master clock rate to 52 MHz for B200. Also, we want to avoid
floating point comparison errors on clock rate settings, but we
expect to be able really set the rates we specify. Set the
offset limit to 1 Hz. If we can't set our rates with that level
of precision, then something is wrong.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Provides substantially improved transmit phase error
performance when enabled. Requires use of 4 samples
per symbol, and is enabled by default when set.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
If there is an error in the sample rate determination, noted
by a negative return sample rate value, error directly and
don't try to set the device rate.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Both RACH and normal bursts are detected with the same approach of
midamble correlation combined with peak-to-average ratio. The
difference is the midamble placements and lengths. Thus, there is
no reason to have independent implementations.
This patch creates a common call burstDetect(), while leaving the
correlation window indexing in the original calls.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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>
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>
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>
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>
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>
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>
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>
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>
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>
The configuration table is instantiated as a global variable with
no means to check constructor status. This means various types
of database failure conditions (e.g. file existence, permissions,
etc.) are not reported. This patch performs a small number of
checks to make sure that the configuration is sane.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
UHD will throw if something goes awry in these sensitive sections,
so we should catch and shutdown gracefully. There is no recovery
if we can't set rates.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Remove the built time resampling selection and link both options.
Move the normal push/pullBuffer() calls back to the base class and
overload them in the inherited resampling class.
USRP2/N2xx devices are the only devices that require resampling so
return that resampling is necessary on the device open(), which is
the point at which the device type will be known.
The GSM transceiver only operates at a whole number multiple of
the GSM rate and doesn't care about the actual device rate and
if resampling is used. Therefore GSM specific portion of the
transceiver should only need to submit the samples-per-symbol
value to the device interface.
Then, the device should be able to determine the appropriate
sample rate (400 ksps or 270.833 ksps) and if resampling is
appropriate.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
The transceiver only uses a single integer oversampling value,
which is more simply referred to as samples-per-symbol.
mRadioOversampling --> mSPS
mTransceiverOversampling (removed)
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Periodic timing alignment should never be required for UHD devices,
though the mechanism was used as a fallback mechanism should UHD
not properly recover after an underrun - as may occur in old
003.003.000 based revisions. This issue is not a concern in more
recent UHD releases and deprecates this code for legacy USRP1
use only.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
Previously, two timing correction values were used for UHD devices
depending on the sample rate of 270.833e3 or 400e3 for native GSM or
resampled device rate respectively. The correction values compensate
for residual timing effects due to analog component delays, filters
lag times, and general fudge factors. These values are device
specific and over-generalized by the two value configuration.
This patch adds the following struct to store these correction
values by device type and sample rate - through samples-per-symbol.
struct uhd_dev_offset {
enum uhd_dev_type type;
int sps;
double offset;
};
Signed-off-by: Thomas Tsou <tom@tsou.cc>
UHD device type was previously detected, but only categorized in
terms of bus type, USB or Ethernet, and sample rate capability.
With the number of supported device increasing, we can no longer
easily group devices since we need to handle more and more
device-specific peculiarities. Some of these factors are managed
internally by the UHD driver, but other factors (e.g. timing
offsets) are specific to a single device.
Start by maintaining an enumerated list of relevant device types
that we can use for applying device specific operations. Also
rename the USB/Ethernet grouping to transmit window type because
that's what it is.
enum uhd_dev_type {
USRP1,
USRP2,
B100,
NUM_USRP_TYPES,
};
Signed-off-by: Thomas Tsou <tom@tsou.cc>
This patch is long overdue and can now be merged after better understanding
of timestamp stability issues. UHD tick / timespec conversions were
generally used with the streamer interface, though these calls are actually
independent change sets. The combination would lead to internal rounding
errors and a timing drift most notably on B100 running at GSM symbol
rate multiples. There are no known issues, however, with the streamer code
itself.
The aforementioned issue was discovered in test code only, which was never
merged to mainline.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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
Although currently unsupported in GSM core, enable TCH/H
support in Transceiver52M for testing and future availability.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@5169 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Without this patch, if SAMPSPERSYM is set bigger than 1, then
erratic behaviour will occur.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@4633 19bc5d8c-e614-43d4-8b26-e1612bc8e597
CommonLibs: Avoid direct syslog calls in ConfigurationTable
We instead introduce a 'log early' facility in Logger.h to accomplish
the same
Signed-off-by: Sylvain Munaut <tnt@246tNt.com>
I added similar code to the reporting functions, which did not exist when sylvain made this patch
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@4629 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Added support for performance-reporting counters.
and
Patch 4588 in private:
For some reason, ReportingTest won't build on all systems. Since it is not part of the actuall application, I am commenting it out from the Makefile.am for now.
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@4627 19bc5d8c-e614-43d4-8b26-e1612bc8e597
The adaptive energy detection threshold does not scale relative
to signal level. In other words, the adjustment factor will be
the same whether the at 40% of signal level or 4%. If the receive
gain is reduced by a large amount, suppose 20 dB, the receiver
may take minutes to adjust to the new level.
When the receive gain is changed, reset the threshold back to
the initial level. This reduces issues of runtime gain adjustment
and prevents blocking bursts while the threhold level slowly
adjusts.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@4595 19bc5d8c-e614-43d4-8b26-e1612bc8e597
1)I did an experiment and compiled OpenBTS with clang yesterday, which
immediately highlighted two potential bugs in the Transceiver52 code.
I'm not sure they are indeed bugs and not the intended behavior, but
they look very much like that. The first one is below and the second
one is in the following mail.
GSM::Time() arguments are defined like #define USB_LATENCY_INTRVL
(10,0), which means that they are expanded into GSM::Time((10,0)).
This expression is a GSM::Time() with a single parameter where (10,0)
return value of the last argument, 0 in this case. I.e.
GSM::Time((10,0)) is equivalent to GSM::Time(0). I think this was not
the intention.
2) Printing \n after every complex number breaks output when you want to
print it in a single line, e.g. in many debug output.
I do not claim any copyright over this change, as it's very basic.
Looking forward to see it merged into mainline.
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@4515 19bc5d8c-e614-43d4-8b26-e1612bc8e597
Thomas Tsou