Transceiver52M: Add NEON complex-complex multiply

Complex-complex block multiples are used for phase rotation of
bursts. Optimization targeted from perf profiling.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Dynamically allocate convolution input vectors

This prevents the use of a copy constructor in the downlink
modulator and prevents a secondary memory allocation during
the convolution. Avoid both cases by dynamically allocating
with preloaded head room. The latter provides enough memory
before the first sample in the burst to cover the length
of the filter taps.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Remove extra copy in receive drive path

Currently the code allocations a signalVector and then copies
into a radioVector. This is unnecessary because the latter is
a derived class making the first allocation unnecessary.
Modify the radioVector constructor to allow direct use in the
case above.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Separate signalVector into it's own file

Break out the signalVector object and clean up the interface in the
process.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Precompute fractional delay filters

Preallocate and compute a bank of fractional sample delay filters.
The number of filters to allocate is specified by the DELAYFILTS
preprocessor definition with a default value of 64. The filters
themselves are sinc pulse generated with 20 taps and Blackman-harris
windowed .

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Default to 1 sample-per-symbol for non-FMA ARM

This includes ARM Cortex-A8 powered device such as Beagle Board and
Gumstix driven E100 USRP. Set the reduced SPS value automatically
for the user.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Set priority on downlink socket thread

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>
Transceiver52M: UHD: Continue on receive and send timeouts

With testing on current UHD releases, currently 003.005.xxx series,
timeout errors on both receive and transmit are recoverable on network
and USB based devices. Remove the fatal error conditions.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Preallocate head room for burst correlation

Set a transceiver high level length value that specifies the largest
number of complex or real filter taps that we will encounter. This
allows preallocation of head room and prevents an extra allocation and
copy on every incoming receive burst.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Setup sinc() call directly with table lookup

On Beagle Board the call into the sinc() function is generating a lot of
load on the peak interpolation. Simplify the sinc() function with a
dedicated table lookup. Eventually, this table may be removed in favour
of using a precomputed filterbank for fractional delay determination.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Allow separate in/out vectors for delay and decimation

Allow non-in-place use of the delay setting. Internally, the delay call
creates a new vector and copies the contents back into the original.
Instead, provide the option to return the computed output vector
directly and remove an an extra copy in the process.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Dynamically allocate correlation vectors

Stack allocating the correlation output generates a call to the copy
constructor of an zero valued vector. We can avoid this extra copy
constructor with a pointer reference and dynamic allocation.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Rearrange socket port assignemnts

Style change for clarity only.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Add vectorized radio burst capability

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>
Transceiver52M: UHD: Add string descriptors to device-offset pairs

As we add more channel combintions including but not limited to
new devices, signal processing schemes, and diversity, we'll
need to handle more special cases. Add string descriptions for
just a bit more sanity.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: sigproc: Wrap internal phase on frequency shift

The call into table lookup will loop on values outside of the
table range. With continuously increasing phase, this leads
to an eventual permanent hard spin. Wrap the phase value to
prevent that from happening.

Signed-off-by: Thomas Tsou <tom@tsou.cc>
Transceiver52M: Refactor receive path outer burst handling

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>
Transceiver52M: Add dual channel diversity receiver option

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>
Transceiver52M: Check time slot validity of incoming bursts

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>
Transceiver52M: Ignore detected bursts at the noise floor

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>