GNU Radio 3.5.3.1 C++ API
digital_constellation_receiver_cb Class Reference

This block takes care of receiving generic modulated signals through phase, frequency, and symbol synchronization.This block takes care of receiving generic modulated signals through phase, frequency, and symbol synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery. More...

#include <digital_constellation_receiver_cb.h>

Inheritance diagram for digital_constellation_receiver_cb:

List of all members.

Public Member Functions

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
- Public Member Functions inherited from gr_block
virtual ~gr_block ()
unsigned history () const
void set_history (unsigned history)
bool fixed_rate () const
 Return true if this block has a fixed input to output rate.
virtual void forecast (int noutput_items, gr_vector_int &ninput_items_required)
 Estimate input requirements given output request.
virtual bool start ()
 Called to enable drivers, etc for i/o devices.
virtual bool stop ()
 Called to disable drivers, etc for i/o devices.
void set_output_multiple (int multiple)
 Constrain the noutput_items argument passed to forecast and general_work.
int output_multiple () const
bool output_multiple_set () const
void set_alignment (int multiple)
 Constrains buffers to work on a set item alignment (for SIMD)
int alignment () const
void set_unaligned (int na)
int unaligned () const
void set_is_unaligned (bool u)
bool is_unaligned () const
void consume (int which_input, int how_many_items)
 Tell the scheduler how_many_items of input stream which_input were consumed.
void consume_each (int how_many_items)
 Tell the scheduler how_many_items were consumed on each input stream.
void produce (int which_output, int how_many_items)
 Tell the scheduler how_many_items were produced on output stream which_output.
void set_relative_rate (double relative_rate)
 Set the approximate output rate / input rate.
double relative_rate () const
 return the approximate output rate / input rate
virtual 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.
virtual 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.
uint64_t nitems_read (unsigned int which_input)
 Return the number of items read on input stream which_input.
uint64_t nitems_written (unsigned int which_output)
 Return the number of items written on output stream which_output.
tag_propagation_policy_t tag_propagation_policy ()
 Asks for the policy used by the scheduler to moved tags downstream.
void set_tag_propagation_policy (tag_propagation_policy_t p)
 Set the policy by the scheduler to determine how tags are moved downstream.
gr_block_detail_sptr detail () const
void set_detail (gr_block_detail_sptr detail)
- Public Member Functions inherited from gr_basic_block
virtual ~gr_basic_block ()
long unique_id () const
std::string name () const
gr_io_signature_sptr input_signature () const
gr_io_signature_sptr output_signature () const
gr_basic_block_sptr to_basic_block ()
virtual bool check_topology (int ninputs, int noutputs)
 Confirm that ninputs and noutputs is an acceptable combination.
template<typename T >
void set_msg_handler (T msg_handler)
 Set the callback that is fired when messages are available.
- Public Member Functions inherited from gr_msg_accepter
 gr_msg_accepter ()
 ~gr_msg_accepter ()
void post (pmt::pmt_t msg)
 send msg to msg_accepter
- Public Member Functions inherited from gruel::msg_accepter
 msg_accepter ()
virtual ~msg_accepter ()
- Public Member Functions inherited from gri_control_loop
 gri_control_loop (float loop_bw, float max_freq, float min_freq)
virtual ~gri_control_loop ()
void update_gains ()
 update the system gains from the loop bandwidth and damping factor
void advance_loop (float error)
 update the system gains from the loop bandwidth and damping factor
void phase_wrap ()
 Keep the phase between -2pi and 2pi.
void frequency_limit ()
 Keep the frequency between d_min_freq and d_max_freq.
void set_loop_bandwidth (float bw)
 Set the loop bandwidth.
void set_damping_factor (float df)
 Set the loop damping factor.
void set_alpha (float alpha)
 Set the loop gain alpha.
void set_beta (float beta)
 Set the loop gain beta.
void set_frequency (float freq)
 Set the Costas loop's frequency.
void set_phase (float phase)
 Set the Costas loop's phase.
float get_loop_bandwidth () const
 Returns the loop bandwidth.
float get_damping_factor () const
 Returns the loop damping factor.
float get_alpha () const
 Returns the loop gain alpha.
float get_beta () const
 Returns the loop gain beta.
float get_frequency () const
 Get the Costas loop's frequency estimate.
float get_phase () const
 Get the Costas loop's phase estimate.

Protected Member Functions

 digital_constellation_receiver_cb (digital_constellation_sptr constellation, float loop_bw, float fmin, float fmax)
 Constructor to synchronize incoming M-PSK symbols.
void phase_error_tracking (float phase_error)
- 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 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

Friends

DIGITAL_API
digital_constellation_receiver_cb_sptr 
digital_make_constellation_receiver_cb (digital_constellation_sptr constell, float loop_bw, float fmin, float fmax)

Additional Inherited Members

- Public Types inherited from gr_block
enum  { WORK_CALLED_PRODUCE = -2, WORK_DONE = -1 }
 Magic return values from general_work. More...
enum  tag_propagation_policy_t { TPP_DONT = 0, TPP_ALL_TO_ALL = 1, TPP_ONE_TO_ONE = 2 }
- Protected Attributes inherited from gri_control_loop
float d_phase
float d_freq
float d_max_freq
float d_min_freq
float d_damping
float d_loop_bw
float d_alpha
float d_beta

Detailed Description

This block takes care of receiving generic modulated signals through phase, frequency, and symbol synchronization.

This block takes care of receiving generic modulated signals through phase, frequency, and symbol synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery.

The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming signal point compared to its nearest constellation point. The frequency and phase of the NCO are updated according to this error.

The symbol synchronization is done using a modified Mueller and Muller circuit from the paper:

G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033.

This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop) every mu samples, then it finds the sampling error based on this and the past symbols and the decision made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications to the M&M used here reduce self-noise.


Constructor & Destructor Documentation

digital_constellation_receiver_cb::digital_constellation_receiver_cb ( digital_constellation_sptr  constellation,
float  loop_bw,
float  fmin,
float  fmax 
)
protected

Constructor to synchronize incoming M-PSK symbols.

Parameters:
constellationconstellation of points for generic modulation
loop_bwLoop bandwidth of the Costas Loop (~ 2pi/100)
fminminimum normalized frequency value the loop can achieve
fmaxmaximum normalized frequency value the loop can achieve

The constructor also chooses which phase detector and decision maker to use in the work loop based on the value of M.


Member Function Documentation

int digital_constellation_receiver_cb::general_work ( int  noutput_items,
gr_vector_int ninput_items,
gr_vector_const_void_star input_items,
gr_vector_void_star output_items 
)
virtual

compute output items from input items

Parameters:
noutput_itemsnumber of output items to write on each output stream
ninput_itemsnumber of input items available on each input stream
input_itemsvector of pointers to the input items, one entry per input stream
output_itemsvector of pointers to the output items, one entry per output stream
Returns:
number of items actually written to each output stream, or -1 on EOF. It is OK to return a value less than noutput_items. -1 <= return value <= noutput_items

general_work must call consume or consume_each to indicate how many items were consumed on each input stream.

Implements gr_block.

void digital_constellation_receiver_cb::phase_error_tracking ( float  phase_error)
protected

Friends And Related Function Documentation

DIGITAL_API digital_constellation_receiver_cb_sptr digital_make_constellation_receiver_cb ( digital_constellation_sptr  constell,
float  loop_bw,
float  fmin,
float  fmax 
)
friend

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