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Automatic Gain Control (agc)

Normalizing the level of an incoming signal is a critical step in many wireless communications systems and is necessary before further processing can happen in the receiver. This is particularly necessary in digital modulation schemes which encode information in the signal amplitude (e.g. see LIQUID_MODEM_QAM16 in section-modem-digital ).

http://liquidsdr.org/doc/agc/

Genetic Algorithm Search Optimization (gasearch)

The gasearch object implements an evolutionary (genetic) algorithm search in liquid. The search uses a binary string of traits called a chromosome (see section-optim-gasearch-chromosome , below) to represent a potential solution. A population of chromosomes is generated and their appropriate fitnesses are calculated.

http://liquidsdr.org/doc/gasearch/

Gauss Minimum-Shift Keying Modulator/Demodulator (gmskmodem)

The two objects gmksmod and gmskdem implement the Gauss minimum-shift keying (GMSK) modem in liquid. Notice that unlike the linear modem objects, the GMSK modulator and demodulator are split into separate objects.

http://liquidsdr.org/doc/gmskmodem/

Mathematical Operations

The math module implements several useful functions for digital signal processing including transcendental function not necessarily in the standard C library, windowing functions, and polynomial manipulation methods.

http://liquidsdr.org/doc/math/

Random Number Generators

The random module in liquid includes a comprehensive set of random number generators useful for simulation of wireless communications channels, particularly for generating noise as well as fading channels. This includes the uniform, normal, circular (complex) Gaussian, Rice- , and Weibull distributions.

http://liquidsdr.org/doc/random/

channel

The channel family of objects add signal impairments due to various channel conditions commonly found in wireless communications systems, including additive white Gauss noise (AWGN) channel gain carrier phase and frequency offsets multi-path fading slowly time-varying shadowing Shown below is an example of the channel object Here is a basic ...

http://liquidsdr.org/doc/channel/

Continuous-Phase Frequency-Shift Keying Modem

Shown in the figure below is a compaarison of the transmitted spectrum for various combinations of parameters. Here is a basic example of the cpfksmod and cpfskdem objects.

http://liquidsdr.org/doc/cpfskmodem/

Frequency-Shift Keying Modem

Frequency-shift keying (fsk) modem... Listed below is the full interface to... Here is a basic example of...

http://liquidsdr.org/doc/fskmodem/

Flexible Framing Structure (flexframe)

liquid comes packaged with two basic framing structures: frame64 and flexframe which can be used with little modification to transmit data over a wireless link.

http://liquidsdr.org/doc/flexframe/

Linear Modem Bit Error Rates, Part II: Derivation

This is the second of a two-part tutorial to derive bit error rate expressions for certain linear modulation schemes.

http://liquidsdr.org/blog/modem-ber-calc/

Contact

The best way to get ahold of me is through email, although I admit that sometimes I'm really not very good about replying. Honestly, though, I'll do my best.

http://liquidsdr.org/contact/

Matrix Operations

Matrices are used for solving linear systems of equations and are used extensively in polynomial fitting, adaptive equalization, and filter design. In liquid , matrices are represented as just arrays of a single dimension, and do not rely on special objects for their manipulation.

http://liquidsdr.org/doc/matrix/

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