GNU Radio 3.6.4.1 C++ API
digital_lms_dd_equalizer_cc Class Reference

Least-Mean-Square Decision Directed Equalizer (complex in/out)This block implements an LMS-based decision-directed equalizer. It uses a set of weights, w, to correlate against the inputs, u, and a decisions is then made from this output. The error in the decision is used to update teh weight vector. More...

#include <digital_lms_dd_equalizer_cc.h>

Inheritance diagram for digital_lms_dd_equalizer_cc:
gr_adaptive_fir_ccc gr_sync_decimator gr_sync_block gr_block gr_basic_block gr_msg_accepter gruel::msg_accepter

List of all members.

Public Member Functions

float get_gain ()
void set_gain (float mu)
- Public Member Functions inherited from gr_adaptive_fir_ccc
void set_taps (const std::vector< gr_complex > &taps)
int work (int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
 just like gr_block::general_work, only this arranges to call consume_each for you
- Public Member Functions inherited from gr_sync_decimator
unsigned decimation () const
void set_decimation (unsigned decimation)
void forecast (int noutput_items, gr_vector_int &ninput_items_required)
 Estimate input requirements given output request.
int general_work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
 compute output items from input items
int fixed_rate_ninput_to_noutput (int ninput)
 Given ninput samples, return number of output samples that will be produced. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this.
int fixed_rate_noutput_to_ninput (int noutput)
 Given noutput samples, return number of input samples required to produce noutput. N.B. this is only defined if fixed_rate returns true. Generally speaking, you don't need to override this.

Protected Member Functions

virtual gr_complex error (const gr_complex &out)
virtual void update_tap (gr_complex &tap, const gr_complex &in)
- Protected Member Functions inherited from gr_adaptive_fir_ccc
gr_complex filter (gr_complex *x)
 gr_adaptive_fir_ccc (const char *name, int decimation, const std::vector< gr_complex > &taps)
- Protected Member Functions inherited from gr_sync_decimator
 gr_sync_decimator (void)
 gr_sync_decimator (const std::string &name, gr_io_signature_sptr input_signature, gr_io_signature_sptr output_signature, unsigned decimation)
- Protected Member Functions inherited from gr_sync_block
 gr_sync_block (void)
 gr_sync_block (const std::string &name, gr_io_signature_sptr input_signature, gr_io_signature_sptr output_signature)
- Protected Member Functions inherited from gr_block
 gr_block (void)
 gr_block (const std::string &name, gr_io_signature_sptr input_signature, gr_io_signature_sptr output_signature)
void set_fixed_rate (bool fixed_rate)
void add_item_tag (unsigned int which_output, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 Adds a new tag onto the given output buffer.
void add_item_tag (unsigned int which_output, const gr_tag_t &tag)
 Adds a new tag onto the given output buffer.
void remove_item_tag (unsigned int which_input, uint64_t abs_offset, const pmt::pmt_t &key, const pmt::pmt_t &value, const pmt::pmt_t &srcid=pmt::PMT_F)
 Removes a tag from the given input buffer.
void remove_item_tag (unsigned int which_input, const gr_tag_t &tag)
 Removes a tag from the given input buffer.
void get_tags_in_range (std::vector< gr_tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end)
 Given a [start,end), returns a vector of all tags in the range.
void get_tags_in_range (std::vector< gr_tag_t > &v, unsigned int which_input, uint64_t abs_start, uint64_t abs_end, const pmt::pmt_t &key)
 Given a [start,end), returns a vector of all tags in the range with a given key.
- Protected Member Functions inherited from gr_basic_block
 gr_basic_block (void)
 gr_basic_block (const std::string &name, gr_io_signature_sptr input_signature, gr_io_signature_sptr output_signature)
 Protected constructor prevents instantiation by non-derived classes.
void set_input_signature (gr_io_signature_sptr iosig)
 may only be called during constructor
void set_output_signature (gr_io_signature_sptr iosig)
 may only be called during constructor
void set_color (vcolor color)
 Allow the flowgraph to set for sorting and partitioning.
vcolor color () const
bool has_msg_handler (pmt::pmt_t which_port)
 Tests if there is a handler attached to port which_port.
virtual void dispatch_msg (pmt::pmt_t which_port, pmt::pmt_t msg)

Friends

DIGITAL_API
digital_lms_dd_equalizer_cc_sptr 
digital_make_lms_dd_equalizer_cc (int num_taps, float mu, int sps, digital_constellation_sptr cnst)

Additional Inherited Members

- Protected Attributes inherited from gr_adaptive_fir_ccc
gr_complex d_error

Detailed Description

Least-Mean-Square Decision Directed Equalizer (complex in/out)

This block implements an LMS-based decision-directed equalizer. It uses a set of weights, w, to correlate against the inputs, u, and a decisions is then made from this output. The error in the decision is used to update teh weight vector.

y[n] = conj(w[n]) u[n] d[n] = decision(y[n]) e[n] = d[n] - y[n] w[n+1] = w[n] + mu u[n] conj(e[n])

Where mu is a gain value (between 0 and 1 and usualy small, around 0.001 - 0.01.

This block uses the digital_constellation object for making the decision from y[n]. Create the constellation object for whatever constellation is to be used and pass in the object. In Python, you can use something like: self.constellation = digital.constellation_qpsk() To create a QPSK constellation (see the digital_constellation block for more details as to what constellations are available or how to create your own). You then pass the object to this block as an sptr, or using "self.constellation.base()".

The theory for this algorithm can be found in Chapter 9 of: S. Haykin, Adaptive Filter Theory, Upper Saddle River, NJ: Prentice Hall, 1996.


Member Function Documentation

virtual gr_complex digital_lms_dd_equalizer_cc::error ( const gr_complex out)
inlineprotectedvirtual
float digital_lms_dd_equalizer_cc::get_gain ( )
inline
void digital_lms_dd_equalizer_cc::set_gain ( float  mu)
inline
virtual void digital_lms_dd_equalizer_cc::update_tap ( gr_complex tap,
const gr_complex in 
)
inlineprotectedvirtual

Friends And Related Function Documentation

DIGITAL_API digital_lms_dd_equalizer_cc_sptr digital_make_lms_dd_equalizer_cc ( int  num_taps,
float  mu,
int  sps,
digital_constellation_sptr  cnst 
)
friend

The documentation for this class was generated from the following file: