Estimate channel and coarse frequency offset for OFDM from preamblesInput: OFDM symbols (in frequency domain). The first one (or two) symbols are expected to be synchronisation symbols, which are used to estimate the coarse freq offset and the initial equalizer taps (these symbols are removed from the stream). The following n_data_symbols are passed through unmodified (the actual equalisation must be done elsewhere). Output: The data symbols, without the synchronisation symbols. The first data symbol passed through has two tags: 'ofdm_sync_carr_offset' (integer), the coarse frequency offset as number of carriers, and 'ofdm_sync_eq_taps' (complex vector). Any tags attached to the synchronisation symbols are attached to the first data symbol. All other tags are propagated as expected. More...

#include <gnuradio/digital/ofdm_chanest_vcvc.h>

Public Types
typedef boost::shared_ptr< ofdm_chanest_vcvc >	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...

Static Public Member Functions
static sptr	make (const std::vector< gr_complex > &sync_symbol1, const std::vector< gr_complex > &sync_symbol2, int n_data_symbols, int eq_noise_red_len=0, int max_carr_offset=-1, bool force_one_sync_symbol=false)

Additional Inherited Members
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...

void	set_inverse_relative_rate (double inverse_relative_rate)
	Set the approximate output rate / input rate using its reciprocal. More...

void	set_relative_rate (uint64_t interpolation, uint64_t decimation)
	Set the approximate output rate / input rate as an integer ratio. More...

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

uint64_t	relative_rate_i () const
	return the numerator, or interpolation rate, of the approximate output rate / input rate More...

uint64_t	relative_rate_d () const
	return the denominator, or decimation rate, of the approximate output rate / input rate More...

mpq_class &	mp_relative_rate ()
	return a reference to the multiple precision rational represntation of 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` output buffer. More...

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

float	pc_output_buffers_full_var (int which)
	Gets variance of fullness of `which` output 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...

void	set_log_level (std::string level)
	Set the logger's output level. More...

std::string	log_level ()
	Get the logger's output level. 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...

std::string	identifier () const

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

std::string	identifier () const

gr::io_signature::sptr	input_signature () const

gr::io_signature::sptr	output_signature () const

basic_block_sptr	to_basic_block ()

bool	alias_set () const

std::string	alias () const

pmt::pmt_t	alias_pmt () const

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)

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 ()

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< rpcbasic_sptr >	d_rpc_vars

pmt::pmt_t	d_message_subscribers

Detailed Description

Estimate channel and coarse frequency offset for OFDM from preambles

Input: OFDM symbols (in frequency domain). The first one (or two) symbols are expected to be synchronisation symbols, which are used to estimate the coarse freq offset and the initial equalizer taps (these symbols are removed from the stream). The following n_data_symbols are passed through unmodified (the actual equalisation must be done elsewhere). Output: The data symbols, without the synchronisation symbols. The first data symbol passed through has two tags: 'ofdm_sync_carr_offset' (integer), the coarse frequency offset as number of carriers, and 'ofdm_sync_eq_taps' (complex vector). Any tags attached to the synchronisation symbols are attached to the first data symbol. All other tags are propagated as expected.

Note: The vector on ofdm_sync_eq_taps is already frequency-corrected, whereas the rest is not.

This block assumes the frequency offset is even (i.e. an integer multiple of 2).

[1] Schmidl, T.M. and Cox, D.C., "Robust frequency and timing synchronization for OFDM", Communications, IEEE Transactions on, 1997. [2] K.D. Kammeyer, "Nachrichtenuebertragung," Chapter. 16.3.2.

Member Typedef Documentation

◆ sptr

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

Member Function Documentation

◆ make()

static sptr gr::digital::ofdm_chanest_vcvc::make	(	const std::vector< gr_complex > &	sync_symbol1,
		const std::vector< gr_complex > &	sync_symbol2,
		int	n_data_symbols,
		int	eq_noise_red_len = `0`,
		int	max_carr_offset = `-1`,
		bool	force_one_sync_symbol = `false`
	)

static

Parameters

sync_symbol1	First synchronisation symbol in the frequency domain. Its length must be the FFT length. For Schmidl & Cox synchronisation, every second sub-carrier has to be zero.
sync_symbol2	Second synchronisation symbol in the frequency domain. Must be equal to the FFT length, or zero length if only one synchronisation symbol is used. Using this symbol is how synchronisation is described in [1]. Leaving this empty forces us to interpolate the equalizer taps. If you are using an unusual sub-carrier configuration (e.g. because of OFDMA), this sync symbol is used to identify the active sub-carriers. If you only have one synchronisation symbol, set the active sub-carriers to a non-zero value in here, and also set `force_one_sync_symbol` parameter to true.
n_data_symbols	The number of data symbols following each set of synchronisation symbols. Must be at least 1.
eq_noise_red_len	If non-zero, noise reduction for the equalizer taps is done according to [2]. In this case, it is the channel influence time in number of samples. A good value is usually the length of the cyclic prefix.
max_carr_offset	Limit the number of sub-carriers the frequency offset can maximally be. Leave this zero to try all possibilities.
force_one_sync_symbol	See `sync_symbol2`.

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

ofdm_chanest_vcvc.h

Public Types

Static Public Member Functions

Additional Inherited Members

Detailed Description

Member Typedef Documentation

◆ sptr

Member Function Documentation

◆ make()