Symbol Synchronizer block with float input, float output. More...

#include <gnuradio/digital/symbol_sync_ff.h>

Public Types
typedef boost::shared_ptr< symbol_sync_ff >	sptr

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, TPP_CUSTOM = 3 }
	enum to represent different tag propagation policies. More...

Public Member Functions
virtual float	loop_bandwidth () const =0
	Returns the normalized approximate loop bandwidth. More...

virtual float	damping_factor () const =0
	Returns the loop damping factor. More...

virtual float	ted_gain () const =0
	Returns the user provided expected gain of the Timing Error Detector. More...

virtual float	alpha () const =0
	Returns the PI filter proportional gain, alpha. More...

virtual float	beta () const =0
	Returns the PI filter integral gain, beta. More...

virtual void	set_loop_bandwidth (float omega_n_norm)=0
	Set the normalized approximate loop bandwidth. More...

virtual void	set_damping_factor (float zeta)=0
	Set the loop damping factor. More...

virtual void	set_ted_gain (float ted_gain)=0
	Set the expected gain of the Timing Error Detector. More...

virtual void	set_alpha (float alpha)=0
	Set the PI filter proportional gain, alpha. More...

virtual void	set_beta (float beta)=0
	Set the PI filter integral gain, beta. More...

Public Member Functions inherited from gr::block
virtual	~block ()

unsigned	history () const

void	set_history (unsigned history)

void	declare_sample_delay (int which, unsigned delay)

void	declare_sample_delay (unsigned delay)

unsigned	sample_delay (int which) const

bool	fixed_rate () const
	Return true if this block has a fixed input to output rate. More...

virtual void	forecast (int noutput_items, gr_vector_int &ninput_items_required)
	Estimate input requirements given output request. More...

virtual 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 More...

virtual bool	start ()
	Called to enable drivers, etc for i/o devices. More...

virtual bool	stop ()
	Called to disable drivers, etc for i/o devices. More...

void	set_output_multiple (int multiple)
	Constrain the noutput_items argument passed to forecast and general_work. More...

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) More...

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. More...

void	consume_each (int how_many_items)
	Tell the scheduler `how_many_items` were consumed on each input stream. More...

void	produce (int which_output, int how_many_items)
	Tell the scheduler `how_many_items` were produced on output stream `which_output`. More...

void	set_relative_rate (double relative_rate)
	Set the approximate output rate / input rate. More...

double	relative_rate () const
	return the approximate output rate / input rate More...

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. More...

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. More...

uint64_t	nitems_read (unsigned int which_input)
	Return the number of items read on input stream which_input. More...

uint64_t	nitems_written (unsigned int which_output)
	Return the number of items written on output stream which_output. More...

tag_propagation_policy_t	tag_propagation_policy ()
	Asks for the policy used by the scheduler to moved tags downstream. More...

void	set_tag_propagation_policy (tag_propagation_policy_t p)
	Set the policy by the scheduler to determine how tags are moved downstream. More...

int	min_noutput_items () const
	Return the minimum number of output items this block can produce during a call to work. More...

void	set_min_noutput_items (int m)
	Set the minimum number of output items this block can produce during a call to work. More...

int	max_noutput_items ()
	Return the maximum number of output items this block will handle during a call to work. More...

void	set_max_noutput_items (int m)
	Set the maximum number of output items this block will handle during a call to work. More...

void	unset_max_noutput_items ()
	Clear the switch for using the max_noutput_items value of this block. More...

bool	is_set_max_noutput_items ()
	Ask the block if the flag is or is not set to use the internal value of max_noutput_items during a call to work. More...

void	expand_minmax_buffer (int port)

long	max_output_buffer (size_t i)
	Returns max buffer size on output port `i`. More...

void	set_max_output_buffer (long max_output_buffer)
	Request limit on max buffer size on all output ports. More...

void	set_max_output_buffer (int port, long max_output_buffer)
	Request limit on max buffer size on output port `port`. More...

long	min_output_buffer (size_t i)
	Returns min buffer size on output port `i`. More...

void	set_min_output_buffer (long min_output_buffer)
	Request limit on the minimum buffer size on all output ports. More...

void	set_min_output_buffer (int port, long min_output_buffer)
	Request limit on min buffer size on output port `port`. More...

float	pc_noutput_items ()
	Gets instantaneous noutput_items performance counter. More...

float	pc_noutput_items_avg ()
	Gets average noutput_items performance counter. More...

float	pc_noutput_items_var ()
	Gets variance of noutput_items performance counter. More...

float	pc_nproduced ()
	Gets instantaneous num items produced performance counter. More...

float	pc_nproduced_avg ()
	Gets average num items produced performance counter. More...

float	pc_nproduced_var ()
	Gets variance of num items produced performance counter. More...

float	pc_input_buffers_full (int which)
	Gets instantaneous fullness of `which` input buffer. More...

float	pc_input_buffers_full_avg (int which)
	Gets average fullness of `which` input buffer. More...

float	pc_input_buffers_full_var (int which)
	Gets variance of fullness of `which` input buffer. More...

std::vector< float >	pc_input_buffers_full ()
	Gets instantaneous fullness of all input buffers. More...

std::vector< float >	pc_input_buffers_full_avg ()
	Gets average fullness of all input buffers. More...

std::vector< float >	pc_input_buffers_full_var ()
	Gets variance of fullness of all input buffers. More...

float	pc_output_buffers_full (int which)
	Gets instantaneous fullness of `which` input buffer. More...

float	pc_output_buffers_full_avg (int which)
	Gets average fullness of `which` input buffer. More...

float	pc_output_buffers_full_var (int which)
	Gets variance of fullness of `which` input buffer. More...

std::vector< float >	pc_output_buffers_full ()
	Gets instantaneous fullness of all output buffers. More...

std::vector< float >	pc_output_buffers_full_avg ()
	Gets average fullness of all output buffers. More...

std::vector< float >	pc_output_buffers_full_var ()
	Gets variance of fullness of all output buffers. More...

float	pc_work_time ()
	Gets instantaneous clock cycles spent in work. More...

float	pc_work_time_avg ()
	Gets average clock cycles spent in work. More...

float	pc_work_time_var ()
	Gets average clock cycles spent in work. More...

float	pc_work_time_total ()
	Gets total clock cycles spent in work. More...

float	pc_throughput_avg ()
	Gets average throughput. More...

void	reset_perf_counters ()
	Resets the performance counters. More...

void	setup_pc_rpc ()
	Sets up export of perf. counters to ControlPort. Only called by the scheduler. More...

bool	is_pc_rpc_set ()
	Checks if this block is already exporting perf. counters to ControlPort. More...

void	no_pc_rpc ()
	If the block calls this in its constructor, it's perf. counters will not be exported. More...

void	set_processor_affinity (const std::vector< int > &mask)
	Set the thread's affinity to processor core `n`. More...

void	unset_processor_affinity ()
	Remove processor affinity to a specific core. More...

std::vector< int >	processor_affinity ()
	Get the current processor affinity. More...

int	active_thread_priority ()
	Get the current thread priority in use. More...

int	thread_priority ()
	Get the current thread priority stored. More...

int	set_thread_priority (int priority)
	Set the current thread priority. More...

bool	update_rate () const

void	system_handler (pmt::pmt_t msg)
	the system message handler More...

bool	finished ()
	returns true when execution has completed due to a message connection More...

block_detail_sptr	detail () const

void	set_detail (block_detail_sptr detail)

void	notify_msg_neighbors ()
	Tell msg neighbors we are finished. More...

void	clear_finished ()
	Make sure we don't think we are finished. More...

Public Member Functions inherited from gr::basic_block
pmt::pmt_t	message_subscribers (pmt::pmt_t port)

virtual	~basic_block ()

long	unique_id () const

long	symbolic_id () const

std::string	name () const

std::string	symbol_name () const

gr::io_signature::sptr	input_signature () const

gr::io_signature::sptr	output_signature () const

basic_block_sptr	to_basic_block ()

bool	alias_set ()

std::string	alias ()

pmt::pmt_t	alias_pmt ()

void	set_block_alias (std::string name)

void	message_port_register_in (pmt::pmt_t port_id)

void	message_port_register_out (pmt::pmt_t port_id)

void	message_port_pub (pmt::pmt_t port_id, pmt::pmt_t msg)

void	message_port_sub (pmt::pmt_t port_id, pmt::pmt_t target)

void	message_port_unsub (pmt::pmt_t port_id, pmt::pmt_t target)

virtual bool	message_port_is_hier (pmt::pmt_t port_id)

virtual bool	message_port_is_hier_in (pmt::pmt_t port_id)

virtual bool	message_port_is_hier_out (pmt::pmt_t port_id)

pmt::pmt_t	message_ports_in ()
	Get input message port names. More...

pmt::pmt_t	message_ports_out ()
	Get output message port names. More...

void	_post (pmt::pmt_t which_port, pmt::pmt_t msg)

bool	empty_p (pmt::pmt_t which_port)
	is the queue empty? More...

bool	empty_p ()

bool	empty_handled_p (pmt::pmt_t which_port)
	are all msg ports with handlers empty? More...

bool	empty_handled_p ()

size_t	nmsgs (pmt::pmt_t which_port)
	How many messages in the queue? More...

void	insert_tail (pmt::pmt_t which_port, pmt::pmt_t msg)

pmt::pmt_t	delete_head_nowait (pmt::pmt_t which_port)

pmt::pmt_t	delete_head_blocking (pmt::pmt_t which_port, unsigned int millisec=0)

msg_queue_t::iterator	get_iterator (pmt::pmt_t which_port)

void	erase_msg (pmt::pmt_t which_port, msg_queue_t::iterator it)

virtual bool	has_msg_port (pmt::pmt_t which_port)

const msg_queue_map_t &	get_msg_map (void) const

virtual void	setup_rpc ()
	Set up the RPC registered variables. More...

bool	is_rpc_set ()
	Ask if this block has been registered to the RPC. More...

void	rpc_set ()
	When the block is registered with the RPC, set this. More...

virtual bool	check_topology (int ninputs, int noutputs)
	Confirm that ninputs and noutputs is an acceptable combination. More...

template<typename T >
void	set_msg_handler (pmt::pmt_t which_port, T msg_handler)
	Set the callback that is fired when messages are available. More...

Public Member Functions inherited from gr::msg_accepter
	msg_accepter ()

	~msg_accepter ()

void	post (pmt::pmt_t which_port, pmt::pmt_t msg)
	send `msg` to `msg_accepter` on port `which_port` More...

Public Member Functions inherited from gr::messages::msg_accepter
	msg_accepter ()

Static Public Member Functions
static sptr	make (enum ted_type detector_type, float sps, float loop_bw, float damping_factor=1.0f, float ted_gain=1.0f, float max_deviation=1.5f, int osps=1, constellation_sptr slicer=constellation_sptr(), ir_type interp_type=IR_MMSE_8TAP, int n_filters=128, const std::vector< float > &taps=std::vector< float >())

Additional Inherited Members
Protected Types inherited from gr::basic_block
enum	vcolor { WHITE, GREY, BLACK }

Protected Member Functions inherited from gr::block
	block (void)

	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. More...

void	add_item_tag (unsigned int which_output, const tag_t &tag)
	Adds a new tag onto the given output buffer. More...

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)
	DEPRECATED. Will be removed in 3.8. More...

void	remove_item_tag (unsigned int which_input, const tag_t &tag)
	DEPRECATED. Will be removed in 3.8. More...

void	get_tags_in_range (std::vector< 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. More...

void	get_tags_in_range (std::vector< 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. More...

void	get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end)
	Gets all tags within the relative window of the current call to work. More...

void	get_tags_in_window (std::vector< tag_t > &v, unsigned int which_input, uint64_t rel_start, uint64_t rel_end, const pmt::pmt_t &key)
	Operates like gr::block::get_tags_in_window with the ability to only return tags with the specified `key`. More...

void	enable_update_rate (bool en)

Protected Member Functions inherited from gr::basic_block
	basic_block (void)

	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. More...

void	set_input_signature (gr::io_signature::sptr iosig)
	may only be called during constructor More...

void	set_output_signature (gr::io_signature::sptr iosig)
	may only be called during constructor More...

void	set_color (vcolor color)
	Allow the flowgraph to set for sorting and partitioning. More...

vcolor	color () const

virtual bool	has_msg_handler (pmt::pmt_t which_port)
	Tests if there is a handler attached to port `which_port`. More...

virtual void	dispatch_msg (pmt::pmt_t which_port, pmt::pmt_t msg)

Protected Attributes inherited from gr::block
std::vector< long >	d_max_output_buffer

std::vector< long >	d_min_output_buffer

gr::thread::mutex	d_setlock

gr::logger_ptr	d_logger

gr::logger_ptr	d_debug_logger

const pmt::pmt_t	d_pmt_done

const pmt::pmt_t	d_system_port

Protected Attributes inherited from gr::basic_block
std::string	d_name

gr::io_signature::sptr	d_input_signature

gr::io_signature::sptr	d_output_signature

long	d_unique_id

long	d_symbolic_id

std::string	d_symbol_name

std::string	d_symbol_alias

vcolor	d_color

bool	d_rpc_set

msg_queue_map_t	msg_queue

std::vector< boost::any >	d_rpc_vars

pmt::pmt_t	d_message_subscribers

Detailed Description

Symbol Synchronizer block with float input, float output.

This implements a discrete-time error-tracking synchronizer.

For this block to work properly, the input stream must meet the following requirements:

if not using the PFB Matched Filter interpolator, and using a non-CPM timing error detector, the input pulses must have peaks (not flat), which usually can be implemented by using a matched filter before this block.
for decision directed timing error detectors, the input pulses should nominally match the normalized slicer constellation, which is normalized to an average symbol magnitude of 1.0 over the entire constellation.

Member Typedef Documentation

typedef boost::shared_ptr<symbol_sync_ff> gr::digital::symbol_sync_ff::sptr

Member Function Documentation

virtual float gr::digital::symbol_sync_ff::alpha ( ) const

pure virtual

Returns the PI filter proportional gain, alpha.

See the documentation for set_alpha() for more details.

virtual float gr::digital::symbol_sync_ff::beta ( ) const

pure virtual

Returns the PI filter integral gain, beta.

See the documentation for set_beta() for more details.

virtual float gr::digital::symbol_sync_ff::damping_factor ( ) const

pure virtual

Returns the loop damping factor.

See the documentation for set_damping_factor() for more details.

Note that if set_alpha() or set_beta() were called to directly set gains, the value returned by this method will be inaccurate/stale.

virtual float gr::digital::symbol_sync_ff::loop_bandwidth ( ) const

pure virtual

Returns the normalized approximate loop bandwidth.

See the documentation for set_loop_bandwidth() for more details.

Note that if set_alpha() or set_beta() were called to directly set gains, the value returned by this method will be inaccurate/stale.

static sptr gr::digital::symbol_sync_ff::make	(	enum ted_type	detector_type,
		float	sps,
		float	loop_bw,
		float	damping_factor = `1.0f`,
		float	ted_gain = `1.0f`,
		float	max_deviation = `1.5f`,
		int	osps = `1`,
		constellation_sptr	slicer = `constellation_sptr()`,
		ir_type	interp_type = `IR_MMSE_8TAP`,
		int	n_filters = `128`,
		const std::vector< float > &	taps = `std::vector< float >()`
	)

static

Make a Symbol Synchronizer block.

This implements a discrete-time error-tracking synchronizer.

For this block to work properly, the input stream must meet the following requirements:

if not using the PFB Matched Filter interpolator, and using a non-CPM timing error detector, the input pulses must have peaks (not flat), which usually can be implemented by using a matched filter before this block.
for decision directed timing error detectors, the input pulses should nominally match the normalized slicer constellation, which is normalized to an average symbol magnitude of 1.0 over the entire constellation.

Parameters

detector_type	The enumerated type of timing error detector to use. See enum ted_type for a list of possible types.
sps	User specified nominal clock period in samples per symbol.
loop_bw	Approximate normailzed loop bandwidth of the symbol clock tracking loop. It should nominally be close to 0, but greater than 0. If unsure, start with a number around 2pi0.040, and experiment to find the value that works best for your situation.
damping_factor	Damping factor of the symbol clock tracking loop. Damping < 1.0f is an under-damped loop. Damping = 1.0f/sqrt(2.0f) is a maximally flat loop response. Damping = 1.0f is a critically-damped loop. Damping > 1.0f is an over-damped loop.
ted_gain	Expected gain of the timing error detector, given the TED in use and the anticipated input amplitude, pulse shape, and Es/No. This value is the slope of the TED's S-curve at timing offset tau = 0. This value is normally computed by the user analytically or by simulation in a tool outside of GNURadio. This value must be correct for the loop filter gains to be computed properly from the desired input loop bandwidth and damping factor.
max_deviation	Maximum absolute deviation of the average clock period estimate from the user specified nominal clock period in samples per symbol.
osps	The number of output samples per symbol (default=1).
slicer	A constellation obj shared pointer that will be used by decision directed timing error detectors to make decisions. I.e. the timing error detector will use this constellation as a slicer, if the particular algorithm needs sliced symbols.
interp_type	The enumerated type of interpolating resampler to use. See the interpolating resampler type enum for a list of possible types.
n_filters	The number of arms in the polyphase filterbank of the interpolating resampler, if using an interpolating resampler that uses a PFB.
taps	The prototype filter for the polyphase filterbank of the interpolating resampler, if using an interpolating resampler that uses a PFB.

virtual void gr::digital::symbol_sync_ff::set_alpha ( float alpha )

pure virtual

Set the PI filter proportional gain, alpha.

Sets the PI filter proportional gain, alpha. This gain directly mutliplies the clock phase/timing error term in the PI filter when advancing the loop. It most directly affects the instantaneous clock period estimate, T_inst, and instantaneous clock phase estimate, tau.

This value would normally be adjusted by setting the loop bandwidth and damping factor. However, it can be set here directly if desired.

Setting this parameter directly is probably only feasible if the user is directly observing the estimates of average clock period and instantaneous clock period over time in response to an impulsive change in the input stream (i.e. watching the loop transient behavior at the start of a data burst).

Parameters

alpha PI filter proportional gain

virtual void gr::digital::symbol_sync_ff::set_beta ( float beta )

pure virtual

Set the PI filter integral gain, beta.

Sets the PI filter integral gain, beta. This gain is used when integrating the clock phase/timing error term in the PI filter when advancing the loop. It most directly affects the average clock period estimate, T_avg.

This value would normally be adjusted by setting the loop bandwidth and damping factor. However, it can be set here directly if desired.

Setting this parameter directly is probably only feasible if the user is directly observing the estimates of average clock period and instantaneous clock period over time in response to an impulsive change in the input stream (i.e. watching the loop transient behavior at the start of a data burst).

Parameters

beta	PI filter integral gain

virtual void gr::digital::symbol_sync_ff::set_damping_factor ( float zeta )

pure virtual

Set the loop damping factor.

Set the damping factor of the loop. Damping in the range (0.0, 1.0) yields an under-damped loop. Damping in the range (1.0, Inf) yields an over-damped loop. Damping equal to 1.0 yields a crtically-damped loop. Damping equal to 1.0/sqrt(2.0) yields a maximally flat loop filter response.

Damping factor of the 2nd order loop transfer function. When a new damping factor is set, the gains, alpha and beta, of the loop are automatcally recalculated.

Parameters

zeta	loop damping factor

virtual void gr::digital::symbol_sync_ff::set_loop_bandwidth ( float omega_n_norm )

pure virtual

Set the normalized approximate loop bandwidth.

Set the normalized approximate loop bandwidth. Useful values are usually close to 0.0, e.g. 2*pi*0.045.

It should be a small positive number, corresponding to the normalized natural radian frequency of the loop as digital low-pass filter that is filtering the clock phase/timing error.

Technically this parameter corresponds to the natural radian frequency of the 2nd order loop transfer function (scaled by Fs), which is the radius of the pole locations in the s-plane of an underdamped analog 2nd order system.

The input parameter corresponds to omega_n_norm in the following relation:

omega_n_norm = omega_n*T = 2*pi*f_n*T = 2*pi*f_n_norm

where T is the period of the clock being estimated by this clock tracking loop, and omega_n is the natural radian frequency of the 2nd order loop transfer function.

When a new loop bandwidth is set, the gains, alpha and beta, of the loop are automatically recalculated.

Parameters

omega_n_norm normalized approximate loop bandwidth

virtual void gr::digital::symbol_sync_ff::set_ted_gain ( float ted_gain )

pure virtual

Set the expected gain of the Timing Error Detector.

Sets the expected gain of the timing error detector, given the TED in use and the anticipated input amplitude, pulse shape, and Es/No. This value is the slope of the TED's S-curve at timing offset tau = 0. This value is normally computed by the user analytically or by simulation in a tool outside of GNURadio. This value must be correct for the loop filter gains to be computed properly from the desired input loop bandwidth and damping factor.

When a new ted_gain is set, the gains, alpha and beta, of the loop are automatcally recalculated.

Parameters

ted_gain expected gain of the timing error detector

virtual float gr::digital::symbol_sync_ff::ted_gain ( ) const

pure virtual

Returns the user provided expected gain of the Timing Error Detector.

See the documentation for set_ted_gain() for more details.

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

symbol_sync_ff.h

Public Types

Public Member Functions

Static Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

Member Function Documentation