Reduce the burst detection threshold to pass more bursts to upper
layers, but force stricter requirements on the computation itself.
For the latter, we now require at least 5 samples (rather than 2)
to compute a peak-to-average value.
End result is increased burst detection at low SNR conditions with
a small increase in false positive bursts when no signal is present.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
OsmoTRX does not support the use of multiple TSC settings per
internal TRX instance. There should not be an error to modifiy
the TSC value after POWERON. Setting TSC value on TRX channels
other then 0 is a NOP operation that should only error if the
requested TSC differs from that of TRX channel 0.
Reported-by: Max <msuraev@sysmocom.de>
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Current UDP receive reads up to MAX_UDP_LENGTH bytes into the
passed in buffer, which may lead to buffer overflow if the
write buffer is of insufficient size.
Add mandatory length argument to UDP socket receive calls.
Reported-by: Simone Margaritelli <simone@zimperium.com>
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Previously MAXDLY value was applied to Normal Bursts, which was nice
when working with sloppy test equipment like CMD57, but useless for
real world usage. At the same time documentation and de facto usage
of MAXDLY in OsmoBTS and OpenBTS assumed that it actually applies to
Access Bursts (RACH). So this patch changes osmo-rx behavior to apply
MAXDLY to RACH bursts and introduces a new command MAXDLYNB for the
old behavior.
When EDGE is enabled with the '-e' option, the random burst generator
switches from GMSK normal bursts to 8-PSK EDGE bursts.
$ ./osmo-trx -e -r 7
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Setup generators for empty, random, and dummy bursts. This moves error
prone burst length handling out of the Transceiver and into the signal
processing core.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Create EDGE slot type in the Transceiver. When EDGE mode is enabled
for a particular slot, blind detection will be performed by
correlating against EDGE followed by normal bursts if no EDGE burst
is found.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Allow setting the device to non single SPS sample rates - mainly
running at 4 SPS as the signal processing library does not support
other rates. Wider bandwith support is required on the receive path
to avoid 8-PSK bandlimiting distortion for EDGE.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
DFE equalizer is unused and has been experiencing code rot for
multiple years. The effect is a significant amount of baggage being
carried in the Transceiver and interfaces.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Samples per symbol used by the transceiver is not configurable through
the socket interface once running, so stop pretending like it could be.
Initialize all tables and midambles at start.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
As a side change - get rid of passing toa and amp arguments as pointers and use
references instead.
The commit doesn't change behaviour, but makes the code cleaner.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
We can't rely on an assumption that if we can't decode a burst - it's noise.
There are many rasons why we can't decode a burst even if it's well above the
noise level. Just one example is a RACH burst which can be overlapped with
another RACH burst up to a level both are completely unrecognizable. Another
example is when a burst is destroyed by bad multi-path.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
It does more harm than good. the current noise calculation is too error
prone, so we can't trust it. And we end up loosing perfectly good bursts
because of that.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
There are two primary changes in this commit:
1) Return values of detect functions changed form bool to int to actually pass
the return value from the inner function and notify higher levels about clipping.
Previously the information was lost due to conversion to bool.
2) Clipping level is not the final verdict now. We still try to demod a burst
and mark it as clipped only if the level is above the clipping level AND we can't
demod it. The reasoning for this is that in real life we want to do as much as
possible to demod the burst, because we want to get as much from our dynamic
range as possible. So a little bit of clipping is fine and is expected. We just
don't want too much of it to break our demod.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Receive thread receives data from the device, which is a more stable source of
clocking than the transmit side. If transmit side has a hiccup, osmo-trx doesn't
send the clock indication, and transmit side is getting completely lost in time.
With this patch we ensure that clock indication keeps coming.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Alert user of overdriven burst input indicated by a positive
threshold detector result. This indication serves as notification
that the receive RF gain level is too high for the configured
transceiver setup.
Signed-off-by: Tom Tsou <tom.tsou@ettus.com>
Add stop and restart capability through the POWEROFF and POWERON
commands. Calling stop causes receive streaming to cease, and I/O
threads to shutdown leaving only the control handling thread running.
Upon receiving a POWERON command, I/O threads and device streaming are
restarted.
Proper shutdown of the transceiver is now initiated by the destructor,
which calls the stop command internally to wind down and deallocate
threads.
Signed-off-by: Tom Tsou <tom@tsou.cc>
Commit 15d743efaf "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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
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>
Tom Tsou