tinymodem::OFDMConfig Struct Reference

Configuration of the OFDM modem (OFDMEncoder, OFDMDecoder): the data is transmitted in parallel on carriers subcarriers with differential QPSK (2 bits per carrier and symbol). Each symbol has a cyclic prefix (guard interval) against echoes. More...

#include <OFDM.h>

Inheritance diagram for tinymodem::OFDMConfig:

Collaboration diagram for tinymodem::OFDMConfig:

Public Member Functions
	OFDMConfig ()
bool	setMode (const char *mode)
	Selects "ofdm16", "ofdm32" or "ofdm64": returns false if invalid.
int	fftSize () const
	length of the useful part of a symbol (DFT size) in samples
int	prefixSize () const
	length of the cyclic prefix in samples
int	firstBin () const
	DFT bin of the first carrier: even, for the sync symbol.
float	carrierFrequency (int idx) const
	frequency of the carrier with the indicated index
float	symbolRate () const
	OFDM symbols per second.
float	bitRate () const
	data bits per second
bool	isValid () const
	Checks the configuration: returns false (and logs the reason) if invalid.

Static Public Member Functions
static bool	isMode (const char *mode)
	true if the mode is an OFDM mode
static int	headerSymbols (int carriers)
	Number of symbols of the header (32 bits, one bit per carrier).
static int	knownPhase (int symbol, int carrier)

Public Attributes
int	carriers = 32
	number of carriers (4 - 128)
float	carrier_spacing = 62.5f
	distance of the carriers in Hz
float	first_freq = 1000.0f
	frequency of the first carrier in Hz
float	guard = 0.25f
	length of the cyclic prefix relative to the symbol (0.0 - 0.5)
float	volume = 1.0f
	transmit amplitude (0.0 - 1.0)
int	max_frame = 512
	transmitter: max number of bytes per frame
float	sync_threshold = 0.5f
	receiver: minimum normalized correlation of the sync symbol
bool	rx_one = false
	receiver: stop after the first frame
uint8_t	channel = 0
	receiver: input channel which is used for the decoding
float	rx_noise = 0.0f
	receiver: (testing only) amplitude of added uniform noise

Static Protected Member Functions
static int	modeCarriers (const char *mode)

Detailed Description

Configuration of the OFDM modem (OFDMEncoder, OFDMDecoder): the data is transmitted in parallel on carriers subcarriers with differential QPSK (2 bits per carrier and symbol). Each symbol has a cyclic prefix (guard interval) against echoes.

setMode() selects "ofdm16", "ofdm32" or "ofdm64": all use the band from 1000 Hz to about 3000 Hz and transmit 3200 bit/s. More carriers result in longer symbols with a longer guard interval.

Copyright

GPLv3

Constructor & Destructor Documentation

OFDMConfig()

tinymodem::OFDMConfig::OFDMConfig ( )

inline

Member Function Documentation

bitRate()

float tinymodem::OFDMConfig::bitRate ( ) const

inline

data bits per second

carrierFrequency()

float tinymodem::OFDMConfig::carrierFrequency ( int idx ) const

inline

frequency of the carrier with the indicated index

fftSize()

int tinymodem::OFDMConfig::fftSize ( ) const

inline

length of the useful part of a symbol (DFT size) in samples

firstBin()

int tinymodem::OFDMConfig::firstBin ( ) const

inline

DFT bin of the first carrier: even, for the sync symbol.

headerSymbols()

int tinymodem::OFDMConfig::headerSymbols ( int carriers )

inlinestatic

Number of symbols of the header (32 bits, one bit per carrier).

isMode()

bool tinymodem::OFDMConfig::isMode ( const char * mode )

inlinestatic

true if the mode is an OFDM mode

isValid()

bool tinymodem::OFDMConfig::isValid ( ) const

inline

Checks the configuration: returns false (and logs the reason) if invalid.

knownPhase()

int tinymodem::OFDMConfig::knownPhase ( int symbol, int carrier )

inlinestatic

Known phase (0 - 3, in steps of 90 degrees) of a carrier in the sync (symbol = 0) and reference (symbol = 1) symbols

modeCarriers()

int tinymodem::OFDMConfig::modeCarriers ( const char * mode )

inlinestaticprotected

prefixSize()

int tinymodem::OFDMConfig::prefixSize ( ) const

inline

length of the cyclic prefix in samples

setMode()

bool tinymodem::OFDMConfig::setMode ( const char * mode )

inline

Selects "ofdm16", "ofdm32" or "ofdm64": returns false if invalid.

symbolRate()

float tinymodem::OFDMConfig::symbolRate ( ) const

inline

OFDM symbols per second.

Member Data Documentation

carrier_spacing

float tinymodem::OFDMConfig::carrier_spacing = 62.5f

distance of the carriers in Hz

carriers

int tinymodem::OFDMConfig::carriers = 32

number of carriers (4 - 128)

channel

uint8_t tinymodem::OFDMConfig::channel = 0

receiver: input channel which is used for the decoding

first_freq

float tinymodem::OFDMConfig::first_freq = 1000.0f

frequency of the first carrier in Hz

guard

float tinymodem::OFDMConfig::guard = 0.25f

length of the cyclic prefix relative to the symbol (0.0 - 0.5)

max_frame

int tinymodem::OFDMConfig::max_frame = 512

transmitter: max number of bytes per frame

rx_noise

float tinymodem::OFDMConfig::rx_noise = 0.0f

receiver: (testing only) amplitude of added uniform noise

rx_one

bool tinymodem::OFDMConfig::rx_one = false

receiver: stop after the first frame

sync_threshold

float tinymodem::OFDMConfig::sync_threshold = 0.5f

receiver: minimum normalized correlation of the sync symbol

volume

float tinymodem::OFDMConfig::volume = 1.0f

transmit amplitude (0.0 - 1.0)

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

• src/modem/OFDM.h