digital_ofdm_cyclic_prefixer Class Reference

Adds a cyclic prefix and performs pulse shaping on OFDM symbols.Input: OFDM symbols (in the time domain, i.e. after the IFFT). Optionally, entire frames can be processed. In this case, len_tag_key must be specified which holds the key of the tag that denotes how many OFDM symbols are in a frame. Output: A stream of (scalar) complex symbols, which include the cyclic prefix and the pulse shaping. Note: If complete frames are processed, and rolloff_len is greater than zero, the final OFDM symbol is followed by the delay line of the pulse shaping. More...

#include <digital_ofdm_cyclic_prefixer.h>

Inheritance diagram for digital_ofdm_cyclic_prefixer:

List of all members.

Public Member Functions
int	work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
	Just like gr_block::general_work, but makes sure the input is valid.
Protected Member Functions
	digital_ofdm_cyclic_prefixer (size_t input_size, size_t output_size, int rolloff_len, const std::string &len_tag_key)
int	calculate_output_stream_length (const gr_vector_int &ninput_items)
	Return the number of complex samples from the number of OFDM symbols (includes rolloff)
Friends
DIGITAL_API digital_ofdm_cyclic_prefixer_sptr	digital_make_ofdm_cyclic_prefixer (size_t input_size, size_t output_size, int rolloff_len, const std::string &len_tag_key)

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Detailed Description

Adds a cyclic prefix and performs pulse shaping on OFDM symbols.

Input: OFDM symbols (in the time domain, i.e. after the IFFT). Optionally, entire frames can be processed. In this case, len_tag_key must be specified which holds the key of the tag that denotes how many OFDM symbols are in a frame. Output: A stream of (scalar) complex symbols, which include the cyclic prefix and the pulse shaping. Note: If complete frames are processed, and rolloff_len is greater than zero, the final OFDM symbol is followed by the delay line of the pulse shaping.

The pulse shape is a raised cosine in the time domain.

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Constructor & Destructor Documentation

digital_ofdm_cyclic_prefixer::digital_ofdm_cyclic_prefixer	(	size_t	input_size,
		size_t	output_size,
		int	rolloff_len,
		const std::string &	len_tag_key
	)		[protected]

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Member Function Documentation

int digital_ofdm_cyclic_prefixer::calculate_output_stream_length

(

const gr_vector_int &

ninput_items

)

[protected, virtual]

Return the number of complex samples from the number of OFDM symbols (includes rolloff)

Reimplemented from gr_tagged_stream_block.

int digital_ofdm_cyclic_prefixer::work	(	int	noutput_items,
		gr_vector_int &	ninput_items,
		gr_vector_const_void_star &	input_items,
		gr_vector_void_star &	output_items
	)		[virtual]

Just like gr_block::general_work, but makes sure the input is valid.

The user must override work to define the signal processing code. Check the documentation for general_work() to see what happens here.

Like gr_sync_block, this calls consume() for you (it consumes ninput_items[i] items from the i-th port).

A note on tag propagation: The PDU length tags are handled by other functions, but all other tags are handled just as in any other gr_block. So, most likely, you either set the tag propagation policy to TPP_DONT and handle the tag propagation manually, or you propagate tags through the scheduler and don't do anything here.

Parameters:

noutput_items	The size of the writable output buffer
ninput_items	The exact size of the items on every input for this particular PDU. These will be consumed if a length tag key is provided!
input_items	See gr_block
output_items	See gr_block

Implements gr_tagged_stream_block.

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Friends And Related Function Documentation

DIGITAL_API digital_ofdm_cyclic_prefixer_sptr digital_make_ofdm_cyclic_prefixer	(	size_t	input_size,
		size_t	output_size,
		int	rolloff_len,
		const std::string &	len_tag_key
	)		[friend]

Parameters:

input_size	FFT length (i.e. length of the OFDM symbols)
output_size	FFT length + cyclic prefix length (in samples)
rolloff_len	Length of the rolloff flank in samples
len_tag_key	For framed processing the key of the length tag

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

• digital_ofdm_cyclic_prefixer.h