
## Latest improvements ##

## Improvements for v1.3.1 ##

  * improved selection of SSE/MMX extension flags for gcc
  * agc
    - adding squelch functionality back into gain control object
  * filter
    - adding callback function for Parks-McClellan algorithm to allow generic 
      filter prototyping
    - fixed double-free bug in iirfilt
  * fft
    - adding new spwaterfall family of objects for generating waterfall plot
      and automatically down-size as input sample size grows
  * sequence
    - fixed issue with order of operations causing inconsitent behavior across
      different platforms

## Major improvements for v1.3.0 ##

  * New MIT/X11 license (https://opensource.org/licenses/MIT)
  * agc (automatic gain control)
    - major code scrub, improved reliability, simplified interface
    - block-level operation
  * buffer
    - new cbuffer objects for dynamic-sized circular buffering
  * channel
    - new module to define certain channel emulation objects
    - new functionality includes carrier frequency/phase offsets,
      (time-varying) multi-path, shadowing, and additive noise
  * dotprod
    - adding method to compute x^T * x of a vector (sum of squares)
  * equalization
    - improved interface for LMS and RLS equalizers
    - simplified methods to support blind operation
  * fec (forward error correctino)
    - interleaver and packetizer moved from the framing to the fec module
    - packetizer now includes data whitening
  * fft (fast Fourier transform)
    - general speed improvements for one-dimensional FFTs
    - completely reimplemented spgram (spectral periodogram) objects to
      include both complex and real-values amples with simpler interface
    - reimplemented asgram (ASCII spectral periodogram) objects
  * filter
    - additional prototype create methods, block execution
    - added new fftfilt family of objects to realize linear filter
      with fast Fourier transforms
    - interp family renamed to firinterp, new iirinterp family
    - decim family renamed to firdecim, new iirdecim family
    - add linear interpolation for arbitrary resamp output
    - new multi-stage half-band resampler family
    - symsync: improved stability, added rate adjustment to help pull in
      sample rate offsets
    - added autotests for validating performance of both the
      resamp and msresamp objects
  * framing
    - added `framedatastats` object for counting statistics across different
      framing objects (e.g. number of total bytes received)
    - adding generic callback function definition for all framing
      structures
    - qpacketmodem: new object to easily combine modulating and encoding;
      buffer of data in, modulated and encoded samples out
    - qpilotgen/qpilotsync: new objects to add and synchronize pilot symbols
      to modulated symbols to recover carrier frequency/phase, and gain
    - framing objects: frame64, flexframe now use qpacketmodem, qpilotgen, and
      qpilotsync objects for unified interface and vastly improved performance
    - flexframe: vastly simplified interface
    - qdetector: new family for pre-demodulator synchronizion and detection
    - moved interleaver and packetizer objects to `fec` module
    - symstream: new family for generating random stream of modulated samples
    - msource: new family for generating multiple signals for a single source,
      including tones, noise, modulated symbols
    - symtrack: new family for tracking a stream of symbols and recovering
      signal level, timing, carrier frequency/phase without pilots
  * math
    - new windowing methods (e.g. 7-term Blackman-harris window)
  * matrix
    - adding smatrix family of objects (sparse matrices)
    - improving linear solver methods (roughly doubled speed)
  * modem
    - re-organizing internal linear modem code (no interface change)
    - freqmod/freqdem: new interface, block-level execution for analog FM
    - cpfskmod/cpfskdem: new family for generic non-linear continuous-phase
      frequency-shift modulation (e.g. minimum-shift keying)
    - fskmod/fskdem: new family for non-coherent frequency-shift keying
      modulation, often with many samples per symbol (e.g. 256-FSK)
  * multicarrier
    - adding OFDM framing option for window tapering
    - simplfying OFDM framing for generating preamble symbols (all
      generated OFDM symbols are the same length)
    - adding run-time option for debugging ofdmframesync
    - adding method for initializing subcarriers with frequency range
  * nco (numerically-controlled oscillator)
    - general performance improvements, adding block-level execution
  * optim
    - gradsearch (gradient search) uses internal linesearch for
      significant speed increase and better reliability
    - gradsearch interface greatly simplified
  * utility
    - build no longer auto-generates tables at compile time (helps with cross
      compilation)
  * vector
    - new module to simplify basic vector operations
  * miscellany
    - documentation moved from core repository to website
    - global header file (`liquid.h`) include more structured source
    - consistent naming of reset() methods for most objects

## Major improvements for v1.2.0 ##

  * dotprod
    - leveraging SIMD extensions for vector operations (SSE2, SSE3)
  * fft
    - completely re-structured internal transform strategy including
      Cooley-Tukey mixed-radix algorithm, Rader algorithm for FFTs of
      prime length, and specific codelets for small-size transforms.
  * math
    - new modular arithmetic methods (prime factor, totient, etc.)
  * modem
    - new API creates linear modem objects with one argument, e.g.
      LIQUID_MODEM_QAM16
    - new type definitions for analog modems

## Major improvements for v1.1.0 ##

  * build
    - simplifying build environment by explicitly defining object
      dependencies (no longer auto-generated; much faster now)
  * documentation
    - new tutorials (ofdmflexframe)
    - sections on new objects/methods (msresamp, gmsk filter design,
      soft-decision demodulation)
    - adding useful figures (polyfit-lagrange, symsync)
    - adding BER performance plots for new FEC schemes
    - adding BER performance plots for sqam32 and sqam128
  * agc
    - fixing scaling issues
    - improving computation speed
    - simplifying interface with a single, unified design model
  * equalization
    - adding support for decision-directed equalizers
  * fec
    - adding soft decoding (when available) for forward error-correction
      schemes; generally improves performance by about 2 dB Eb/N0
    - adding half-rate Golay(24,12) code
    - adding SEC-DED codes: (22,16), (39,32), (72,64)
  * filter
    - firdes: adding Nyquist prototyping design method
    - firdes: adding new GMSK receive filter design method
    - interp: porting to efficient polyphase filterbank implementation,
      adding prototype create() method
    - adding multi-stage resampler for efficient decimation and
      interpolation
  * framing
    - adding ofdmflexframe family of objects capable of defining which
      subcarriers are nulls/pilots/data, and easily loading data into
      frames. Very similar to 'flexframe' in usage.
    - supporting soft packet decoding (interleaving, etc.)
    - adding gmskframe generator and synchronizer object; simple,
      reliable
  * matrix
    - adding Cholesky factorization A = R^T * R (for positive definite
      matrices)
    - adding conjugate gradient solver (for positive definite matrices)
  * modem
    - adding simple on/off keying (OOK) type
    - adding 256-APSK type (6,18,32,36,46,54,64)
    - adding 'square' (cross) 32-, 128-QAM types
    - adding 'optimal' 64-, 128-, and 256-QAM constellations
    - improved speed of most schemes' modulate/demodulate
      implementations
    - adding soft-decision (log-likelihood ratio) demodulation
    - adding GMSK modulation/demodulation with improved filter design
  * multicarrier
    - ofdmframe: improving synchronization and reliability in
      interference environments, enabling squelch, improving
      equalization
  * optim
    - simplified interface to gradient search
