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During BTS operation, active downlink bursts drive the clock indication,
but the flow of bursts is not present in MS mode. Shift the indication
trigger to the lower non-blocking loop with FN mod 100 as the interval.
Signed-off-by: Tom Tsou <tom@tsou.cc>
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Use a 64-bit hex value as the mask specifier because the integer string
is rather unwieldly. Fix 64-bit register handling on the mask check.
Receive burst masking is only available on in MS tracking mode (post SCH
acquisition).
Modulus values greater than 64 remain unsupported.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Extend the measured SCH timing offset from the downlink to the uplink
path. In order to absorb the frame timing adjustment and remove the
potential of thread contention during the change, combine the lower
FIFO threads into single drive loop.
Force timing changes through to the UHD interface with stream flags
triggered through the updateAlignment() call.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Create 64-bit multiframe masks for each physical slot. These are set
through the SETRXMASK command with first and second arguemnts timeslot
and mask respectively.
Modulus value of 102 is currently not handled and will cause all receive
bursts on that slot to be disabled in MS tracking mode.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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The GETBSIC command returns 1 if no SCH has been decoded, and 0 with
the BSIC value if SCH decoding has been successful.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Setup two SCH detection ranges - full search and narrow search. Full
search correlates the full burst length to find for SCH detection.
Narrow uses a reduced search range, which is the same as that used for
RACH detection.
Narrow searching is enabled after the SCH is successfully decoded and
the MS is locked to the frame timing.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Enable frequency detection and correction by buffering the previous
frame to allow FCCH measurement and compensation after frame timing is
locked using the SCH. When the SCH is detected and symbol timing
matched, measure the FCCH burst from one frame prior and compensate by
baseband tuning the DDC on the device. Avoid appying frequency
corrections to the RF portion due to possible tuning delays, which is
not an issue with DDC tuning.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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When in MS acquisition mode, attempt to decode SCH and establish the BTS
frame timing. Lock the transceiver GSM clock to the BTS by adjusting the
clock value by the measured burst-SCH offset.
Add tracking state, TRX_MODE_MS_TRACKING, which continues to detect and
decode the SCH with timing tracking, but only on SCH poitions within the
51 multiframe.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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On receipt of a SYNC command on the socket interface, set the mode to
TRX_MODE_MS_ACQUIRE, which attempts to synchronize against a remote BTS
signal by detecting the SCH burst and timing offset. The transceiver
defaults to TRX_MODE_OFF, which implies no BTS or MS capability has been
enabled.
There is currently no command to enable the BTS mode. The MS mode also
disables uplink transmission since no such capability is implemented.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Use similar approach for detecting normal and RACH bursts, but apply a
sample shift after detection in order to gradually zero the measured
timing offset. SCH synchronization sequence and setup are added similar
to RACH detection with the main difference, aside being the SCH runs
full length of the burst. History is also added to accommodate full
length burst correlation.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Commit 15d743efaf8d3ec8dacd37fbac434c1e719c0b30 "Disable filler table
retransmissions by default" made OpenBTS style filler table behavior
optional. When enabled, dummy bursts were automatically loaded into the
filler table, but the table was not updated and only filler busts were
retransmitted.
Enable the restransmit state flag when the filler table option is
specified. Only preload filler table and enable retransmissions on
channel zero.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Burst selection at a particular time works in the following order
of priority.
1. Slot is disabled with channel combination set to NONE (default)
1. Burst exists in priority queue for the current time.
2. Filler table entry is used
This patch sets default behaviour to force all filler table entries
to zero and disallows filler table changes. This effectively means
that only bursts received from upper layers will be transmitted and
nothing will be automatically transmitted in the absence or delay
of incoming burts at a particular time.
New Command line option "Enable C0 filler table" allows reverting
to previous idle burst generation and retransmission behaviour on
TRX0. Retransmission cannot be enabled on non-C0 channels.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Equalization is currently disabled by default. As such, we don't need to
run channel estimates or even track the update state, which would
otherwise be allocating/decallocating the channel state vector at
regular intervals.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Mainly basic signed vs unsigned comparisons and intializer ordering.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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This includes unknown and unused variables, functions, and
non-relevant documentation.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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We support one TSC value per each transceiver object. Only channel
zero can set this value. Other channels can attempt to set the TSC
value, but will error if the TSC does not match the existing value.
In either case, non-zero channels do not manipulate the gloabl TSC
setting.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Simply vectorize the existing power state variable.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Each ARFCN channel may be independently configureted and possibly on
separate hardware, so don't share a single vector for noise estimate
calculations. Allow a non-pointer based iterator so we can get away
with using the default copy constructor.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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The transceiver has the ability to detect bursts below the noise floor,
but little hope in successful decoding, so don't even try. We still use
the detected burst to differentiate against noise vs actual data.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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In errant cases, GSM core may send bursts with invalid slot values,
which is allowed by the GSM::Time object. If we find a burst like this
coming into the transceiver, then drop it immediately.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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This patch add support for dual channel diversity on the receive
path. This allows two antennas two shared antennas to be used for
each ARFCN handling channel in the receiver. This configuration
may improvde performance in multi-path fading environments,
however, noise andpotential interference levels are increased due
to the higher bandwidth used.
The receive path is oversampled by a factor of four for a rate
of 1.083333 Msps. If the receive paths are tuned within a
maximum channel spacing (currently set at 600 kHz), then both
ARFCN frequencies are processed by each channel of the receiver.
Otherwise, the frequency shifted diversity path is disabled and
standard non-diversity operation takes place.
Diversity processing is handled by selecting the path with the
higheset energy level and discarding the burst on the second
path. Selection occurs on a burst-by-burst basis.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Separate the large pullRadioVector() call, which forms the central
portion of the receive path burst processing. Break out RACH, normal
burst, and demodulation into separate methods. This makes the burst
handling from the FIFO read to soft bit output somewhat more
manageable.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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This patch allows multiple signalVectors to be stored within
a single radioVector object. The motivation is to provide
a facility for diversity and/or MIMO burst handling. When
no channel value is specified, single channel bevhaviour
is maintained.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Style change for clarity only.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Clock indications passed up to GSM core originate on the transciever
downlink side. Set priority to keep the flow of clock updates
consistent.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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The transceiver and underlying device drivers are threaded. use
the following priority levels.
0.50 - UHD driver internal threads
0.45 - Receive device drive thread
0.44 - Transmit device drive thread
0.43 - UHD asynchronous update thread (error reporting)
0.42 - Receive burst processing thread(s)
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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This patch primarily addresses devices with multiple RF front end
support. Currently device support is limited to UmTRX.
Vectorize transceiver variables to allow multiple asynchronous
threads on the upper layer with single downlink and uplink threads
driving the UHD I/O interface synchronously.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Collect the slot information into an indpendent state object. This
will allow us to easily create multiple instances of internal state
variables without having to replicate the transceiver object itself.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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For multiple transceiver connections, it is inappropriate to
allocate all sockets in the transceiver constructor due to not
knowing how many connections are avaialble in advance and for
error checking purposes. Instead, store the base socket address
port combination and setup the sockets in the initialization
call.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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The current status and operability of this compile option is
unknown. Remove due to lack of use, demand, and maintenance.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Use the same measurement method for RSSI as the noise level. Previous
method was to use the peak correlation amplitude relative to the
expected value. This created two very different amplitude approaches
between the noise measurement and RSSI measurement, which would
throw off the upper layer MS power control loop.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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Previous removal of the energy detector requirement broke
the noise level calculation loop. The previous adaptive
approach was finicky - noticably at high gain levels. Since
we no longer use the energy threshold for primary burst gating,
we can return to a simpler world.
In the new approach, we compute a running average of energy
levels and track them with a noise vector. A timeslot that
passes the correlator threshold is a valid burst. These are
not used in the noise calculation. Everything else is
considered noise and used to compute the noise level with
respect to full scale input level, which for almost all
supported devices is 2^15.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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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>
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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>
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Unsupported at 4 sps, and performance benefits remain
to be proven at 1 sps. Disable until further testing.
Signed-off-by: Thomas Tsou <tom@tsou.cc>
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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>
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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>
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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>
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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>
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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>
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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>
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Submitted by: Ivan Kluchnikov <kluchnikovi@gmail.com>
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@5690 19bc5d8c-e614-43d4-8b26-e1612bc8e597
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Submitted-by: Andreas Eversberg <jolly@eversberg.eu>
Signed-off-by: Thomas Tsou <tom@tsou.cc>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@5677 19bc5d8c-e614-43d4-8b26-e1612bc8e597
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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
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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
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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
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Put a floor on the transmit latency of the B100 in order to suppress
underruns in typical conditions. Empirical data from a handful of
relatively recent machines shows that the B100 will underrun when
the transmit threshold is reduced to a time of 6 and a half frames,
so we set a minimum 7 frame threshold.
The overall benefit should be marginal and may increase the
possibility of bursts arriving stale (after the trasmit deadline),
but will reduce the number of alarming UHD related messages that
appear in the log file.
This patch is UHD and B100 specific - USRP1 is unaffected.
Signed-off-by: Thomas Tsou <ttsou@vt.edu>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@3980 19bc5d8c-e614-43d4-8b26-e1612bc8e597
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With the introduction of the B100, there is USB support
using UHD devices. The characteristics of the trasmit
side burst submissions are more reflective of the bus
type than the device or driver.
Use a fixed latency interval for network devices and the
adaptive underrun approach for USB devices - regardless
of driver or device type.
The GPMC based transport on the E100 appears unaffected
by either latency scheme, which defaults to network.
Signed-off-by: Thomas Tsou <ttsou@vt.edu>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@2677 19bc5d8c-e614-43d4-8b26-e1612bc8e597
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Small name change to match setTime for a get/set pair.
Signed-off-by: Thomas Tsou <ttsou@vt.edu>
git-svn-id: http://wush.net/svn/range/software/public/openbts/trunk@2673 19bc5d8c-e614-43d4-8b26-e1612bc8e597
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