Schmidl & Cox synchronisation for OFDM. More...

#include <gnuradio/digital/ofdm_sync_sc_cfb.h>

Public Types
typedef std::shared_ptr< ofdm_sync_sc_cfb >	sptr

Public Types inherited from gr::hier_block2
typedef basic_block_sptr	opaque_self
	typedef for object returned from self(). More...

Public Member Functions
virtual void	set_threshold (float threshold)=0

virtual float	threshold () const =0

Public Member Functions inherited from gr::hier_block2
	~hier_block2 () override

opaque_self	self ()
	Return an object, representing the current block, which can be passed to connect. More...

void	connect (basic_block_sptr block)
	Add a stand-alone (possibly hierarchical) block to internal graph. More...

void	connect (basic_block_sptr src, int src_port, basic_block_sptr dst, int dst_port)
	Add gr-blocks or hierarchical blocks to internal graph and wire together. More...

void	msg_connect (basic_block_sptr src, pmt::pmt_t srcport, basic_block_sptr dst, pmt::pmt_t dstport)
	Add gr-blocks or hierarchical blocks to internal graph and wire together. More...

void	msg_connect (basic_block_sptr src, std::string srcport, basic_block_sptr dst, std::string dstport)

void	msg_disconnect (basic_block_sptr src, pmt::pmt_t srcport, basic_block_sptr dst, pmt::pmt_t dstport)

void	msg_disconnect (basic_block_sptr src, std::string srcport, basic_block_sptr dst, std::string dstport)

void	disconnect (basic_block_sptr block)
	Remove a gr-block or hierarchical block from the internal flowgraph. More...

void	disconnect (basic_block_sptr src, int src_port, basic_block_sptr dst, int dst_port)
	Disconnect a pair of gr-blocks or hierarchical blocks in internal flowgraph. More...

void	disconnect_all ()
	Disconnect all connections in the internal flowgraph. More...

virtual void	lock ()

virtual void	unlock ()

int	max_output_buffer (size_t port=0)
	Returns max buffer size (itemcount) on output port `i`. More...

void	set_max_output_buffer (int max_output_buffer)
	Sets max buffer size (itemcount) on all output ports. More...

void	set_max_output_buffer (size_t port, int max_output_buffer)
	Sets max buffer size (itemcount) on output port `port`. More...

int	min_output_buffer (size_t port=0)
	Returns min buffer size (itemcount) on output port `i`. More...

void	set_min_output_buffer (int min_output_buffer)
	Sets min buffer size (itemcount) on all output ports. More...

void	set_min_output_buffer (size_t port, int min_output_buffer)
	Sets min buffer size (itemcount) on output port `port`. More...

flat_flowgraph_sptr	flatten () const

hier_block2_sptr	to_hier_block2 ()

bool	has_msg_port (pmt::pmt_t which_port) override

bool	message_port_is_hier (pmt::pmt_t port_id) override

bool	message_port_is_hier_in (pmt::pmt_t port_id) override

bool	message_port_is_hier_out (pmt::pmt_t port_id) override

void	message_port_register_hier_in (pmt::pmt_t port_id)

void	message_port_register_hier_out (pmt::pmt_t port_id)

void	set_processor_affinity (const std::vector< int > &mask) override
	Set the affinity of all blocks in hier_block2 to processor core `n`. More...

void	unset_processor_affinity () override
	Remove processor affinity for all blocks in hier_block2. More...

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

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

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

bool	all_min_output_buffer_p (void)
	Get if all block min buffers should be set. More...

bool	all_max_output_buffer_p (void)
	Get if all block max buffers should be set. More...

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

	~basic_block () override

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...

virtual void	set_processor_affinity (const std::vector< int > &mask)=0

virtual void	unset_processor_affinity ()=0

virtual std::vector< int >	processor_affinity ()=0

virtual void	set_log_level (const std::string &level)=0

virtual std::string	log_level ()=0

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

	~msg_accepter () override

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

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

virtual	~msg_accepter ()

virtual void	post (pmt::pmt_t which_port, pmt::pmt_t msg)=0
	send `msg` to `msg_accepter` on port `which_port` More...

Static Public Member Functions
static sptr	make (int fft_len, int cp_len, bool use_even_carriers=false, float threshold=0.9)

Additional Inherited Members
Public Attributes inherited from gr::hier_block2
pmt::pmt_t	hier_message_ports_in

pmt::pmt_t	hier_message_ports_out

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

Protected Member Functions inherited from gr::hier_block2
	hier_block2 ()

	hier_block2 (const std::string &name, gr::io_signature::sptr input_signature, gr::io_signature::sptr output_signature)

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)

template<typename Derived >
std::shared_ptr< Derived >	shared_from_base ()
	This is meant to be called by derived classes (e.g. block) to get a shared pointer internally. This is needed because std::enable_shared_from_this doesn't seem to work with derived classes in an inheritance hierarchy. More...

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

gr::logger_ptr	d_logger

gr::logger_ptr	d_debug_logger
	Default logger. More...

msg_queue_map_t	msg_queue
	Verbose logger. More...

std::vector< rpcbasic_sptr >	d_rpc_vars

pmt::pmt_t	d_message_subscribers

Detailed Description

Schmidl & Cox synchronisation for OFDM.

Input: complex samples. Output 0: Fine frequency offset, scaled by the OFDM symbol duration. This is \(\hat{\varphi}\) in [1]. The normalized frequency offset is then 2.0*output0/fft_len. Output 1: Beginning of the first OFDM symbol after the first (doubled) OFDM symbol. The beginning is marked with a 1 (it's 0 everywhere else).

The evaluation of the coarse frequency offset is not done in this block. Also, the initial equalizer taps are not calculated here.

Note that we use a different normalization factor in the timing metric than the authors do in their original work[1]. If the timing metric (8) is

\[ M(d) = \frac{|P(d)|^2}{(R(d))^2}, \]

we calculate the normalization as

\[ R(d) = \frac{1}{2} \sum_{k=0}^{N-1} |r_{k+d}|^2, \]

i.e., we estimate the energy from both half-symbols. This avoids spurious detects at the end of a burst, when the energy level suddenly drops.

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

Member Typedef Documentation

◆ sptr

typedef std::shared_ptr<ofdm_sync_sc_cfb> gr::digital::ofdm_sync_sc_cfb::sptr

Member Function Documentation

◆ make()

static sptr gr::digital::ofdm_sync_sc_cfb::make	(	int	fft_len,
		int	cp_len,
		bool	use_even_carriers = `false`,
		float	threshold = `0.9`
	)

static

Parameters

fft_len	FFT length
cp_len	Length of the guard interval (cyclic prefix) in samples
use_even_carriers	If true, the carriers in the sync preamble are occupied such that the even carriers are used (0, 2, 4, ...). If you use all carriers, that would include the DC carrier, so be careful.
threshold	detection threshold. Default is 0.9.

◆ set_threshold()

virtual void gr::digital::ofdm_sync_sc_cfb::set_threshold ( float threshold )

pure virtual

◆ threshold()

virtual float gr::digital::ofdm_sync_sc_cfb::threshold ( ) const

pure virtual

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

ofdm_sync_sc_cfb.h

Public Types

Public Member Functions

Static Public Member Functions