itpp::Spread_1d Class Reference
Communications Module » Digital Modulation

Spreading of float symbols to float output. More...

`#include <itpp/comm/spread.h>`

## Public Member Functions

| Spread_1d ()
| Constructor.
| Spread_1d (const vec &incode)
| Constructor.
void | spread (const vec &symbols, vec &out)
| Spreading of signal return i out.
vec | spread (const vec &symbols)
| Spreading of signal.
void | despread (const vec &rec_signal, vec &out, int timing)
| Despreading of signal. timing is the start position of the first symbol, given in number of samples.
vec | despread (const vec &rec_signal, int timing)
| Despreading of signal. timing is the start position of the first symbol, given in number of samples.
void | set_code (const vec &incode)
| Set the spreading code used for spreading.
vec | get_code ()
| Returns the spreading code used.
int | get_period ()
| Get the period of the code (length of code vector).

## Protected Attributes

vec | code
| The spreading code.
int | N
| The spreading factor.

## Detailed Description

Spreading of float symbols to float output.

Spreading block for generation of 1-dimensional DS-CDMA signals Useful in the simulation of DS-CDMA systems on chip level or upsampled chip level.

Obeserve that the spreading is normalized so that the energy per bit is preserved before and after spreading (that is each symbol is multiplied with `1/sqrt`(N)). Hence, for the multicode case the energy is normalized for one symbol (code) but the transmitted signal consist of a sum of several signals.

Four different classes exist:

- Spread_1d for 1-dimensional symbols (e.g. BPSK).
- Spread_2d for 2-dimensional symbols (e.g. QPSK).

For multicode transmission, that is each user uses several codes in parallel to transmit data, there exist

- Multicode_Spread_1d for 1-dimensional symbols.
- Multicode_Spread_2d for 2-dimensional symbols.

Example:

#include "itpp/itcomm.h"
int main() {
//Generate the spreading code you want to use.
vec spreading_code = "-1 1 -1 1";
//Initiate th Spreading class
Spread_1d spread_1d(spreading_code);
//Generate the symbols to transmitt
bvec transmitted_bits = randb(10);
BPSK bpsk;
vec transmitted_symbols = bpsk.modulate_bits(transmitted_bits);
//Spread the symbols
vec transmitted_signal = spread_1d.spread(transmitted_symbols);
//Generate the received signal
vec received_signal = transmitted_signal;
//Despread the received signal
vec received_symbols = spread_1d.despread(received_signal,0);
//demodulate the bits
bvec received_bits = bpsk.demodulate_bits(received_symbols);
}
itpp::Array
General array class.
Definition array.h:105
itpp::BPSK
BPSK modulator with real symbols.
Definition modulator.h:877
itpp::BPSK::modulate_bits
void modulate_bits(const bvec &bits, vec &output) const
Modulate bits into BPSK symbols in complex domain.
Definition modulator.cpp:310
itpp::BPSK::demodulate_bits
void demodulate_bits(const vec &signal, bvec &output) const
Demodulate noisy BPSK symbols in complex domain into bits.
Definition modulator.cpp:326
itpp::Spread_1d
Spreading of float symbols to float output.
Definition spread.h:100
itpp::randb
bin randb(void)
Generates a random bit (equally likely 0s and 1s)
Definition random.h:793
itcomm.h
Include file for the IT++ communications module.

Definition at line 99 of file spread.h.

## Constructor & Destructor Documentation

## Spread_1d() [1/2]

itpp::Spread_1d::Spread_1d | ( |  | ) |

inline

Constructor.

Definition at line 103 of file spread.h.

## Spread_1d() [2/2]

itpp::Spread_1d::Spread_1d | ( | const vec & | incode | ) |

Constructor.

Definition at line 39 of file spread.cpp.

References set_code().

## Member Function Documentation

## spread() [1/2]

void itpp::Spread_1d::spread | ( | const vec & | symbols,
|  | vec & | out
| ) |  |

Spreading of signal return i out.

Definition at line 56 of file spread.cpp.

References code, itpp::Array< T >::length(), N, and itpp::Array< T >::set_size().

Referenced by itpp::Spread_2d::spread().

## spread() [2/2]

vec itpp::Spread_1d::spread | ( | const vec & | symbols | ) |

inline

Spreading of signal.

Definition at line 109 of file spread.h.

References spread().

Referenced by spread().

## despread() [1/2]

void itpp::Spread_1d::despread | ( | const vec & | rec_signal,
|  | vec & | out,
|  | int | timing
| ) |  |

Despreading of signal. timing is the start position of the first symbol, given in number of samples.

Definition at line 64 of file spread.cpp.

References code, itpp::Array< T >::length(), itpp::Array< T >::mid(), N, and itpp::Array< T >::set_size().

Referenced by itpp::Spread_2d::despread().

## despread() [2/2]

vec itpp::Spread_1d::despread | ( | const vec & | rec_signal,
|  | int | timing
| ) |  |

inline

Despreading of signal. timing is the start position of the first symbol, given in number of samples.

Definition at line 117 of file spread.h.

## set_code()

void itpp::Spread_1d::set_code | ( | const vec & | incode | ) |

Set the spreading code used for spreading.

Definition at line 44 of file spread.cpp.

References code, N, itpp::norm(), and itpp::Array< T >::size().

Referenced by itpp::Spread_2d::set_code(), and Spread_1d().

## get_code()

vec itpp::Spread_1d::get_code | ( |  | ) |

Returns the spreading code used.

Definition at line 51 of file spread.cpp.

References code.

Referenced by itpp::Spread_2d::get_codeI(), and itpp::Spread_2d::get_codeQ().

## get_period()

int itpp::Spread_1d::get_period | ( |  | ) |

inline

Get the period of the code (length of code vector).

Definition at line 124 of file spread.h.

## Member Data Documentation

## code

vec itpp::Spread_1d::code

protected

The spreading code.

Definition at line 127 of file spread.h.

Referenced by despread(), get_code(), set_code(), and spread().

## N

int itpp::Spread_1d::N

protected

The spreading factor.

Definition at line 129 of file spread.h.

Referenced by despread(), set_code(), and spread().

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

- itpp/comm/spread.h
- itpp/comm/spread.cpp

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