System and method for spreading/despreading in multi-carrier code division multiple access
First Claim
Patent Images
1. A spreading system in multi-carrier code division multiple access (MC-CDMA), comprising:
- a symbol repeating unit for repeating each symbol of a modulated symbol sequence, inputted for spreading in a signal-forming procedure of MC-CDMA, by the number of repetition, R, which is determined by a variable spreading factor;
a spreading unit for a direct spreading for the symbols repeated by the symbol repeating unit using a spreading code of the same chip rate as the symbol rate, to obtain a spread chip sequence;
a demultiplexer for dividing the chip sequence spread by the spreader into as many parallel chip sequences as there are subcarriers, SFF, through a serial/parallel conversion; and
an inverse Fourier transform unit for transforming the chips into a transmission symbol, which includes SFF samples for the multi-carrier transmission over SFF subcarriers.
1 Assignment
0 Petitions
Accused Products
Abstract
A system and a method for spreading/despreading in MC-CDMA are disclosed. Simple spreading and despreading procedures are provided to allow both frequency and time spreading/despreading. The system and method for spreading/despreading in MC-CDMA produce a high processing gain, frequency diversity, and multipath time diversity through two-dimensional time/frequency spreading/despreading. Moreover, the spreading/despreading system and method support a variable transmission rate by simply changing the spreading factor without changing the spreading/despreading procedure and structure.
25 Citations
25 Claims
-
1. A spreading system in multi-carrier code division multiple access (MC-CDMA), comprising:
-
a symbol repeating unit for repeating each symbol of a modulated symbol sequence, inputted for spreading in a signal-forming procedure of MC-CDMA, by the number of repetition, R, which is determined by a variable spreading factor;
a spreading unit for a direct spreading for the symbols repeated by the symbol repeating unit using a spreading code of the same chip rate as the symbol rate, to obtain a spread chip sequence;
a demultiplexer for dividing the chip sequence spread by the spreader into as many parallel chip sequences as there are subcarriers, SFF, through a serial/parallel conversion; and
an inverse Fourier transform unit for transforming the chips into a transmission symbol, which includes SFF samples for the multi-carrier transmission over SFF subcarriers. - View Dependent Claims (2, 3, 4, 5)
-
-
6. A despreading system in MC-CDMA, comprising:
-
a Fourier transform unit for extracting parallel chip sequences received over subcarriers from a received signal, using a Discrete Fourier Transform (DFT) or Fast Fourier Transform (FFT);
a multiplexer for parallel-to-serial-converting the parallel chip sequences extracted by the Fourier transform unit into a single chip sequence;
a despreader for performing a direct despreading for a single chip sequence outputted from the multiplexer using the same spreading code and chip rate as those used by the transmitting side; and
a chip combiner for sequentially combining chip samples, despread by the despreader, corresponding to the number of chips to be combined, R, which is determined by a variable spreading factor SF, to obtain a received modulated symbol sequence. - View Dependent Claims (7, 8, 9, 10, 11)
-
-
12. A spreading method in MC-CDMA, comprising:
-
(a) repeating each symbol of a modulated symbol sequence, inputted for spreading in a signal-forming procedure of MC-CDMA, by the number of repetition, R, which is determined by a variable spreading factor;
(b) producing spread chip sequences from the repeated symbols in (a) by a direct spreading using a spreading code of the same chip rate as the repeated symbol rate, and then dividing the spread chips into as many parallel chips as there are subcarriers, SFF, through a serial/parallel conversion; and
(c) transforming parallel SFF chips obtained in (b) into a transmission symbol for the multicarrier transmission over SFF subcarriers by using inverse DFT or FFT. - View Dependent Claims (13, 14, 15, 16)
-
-
17. A despreading method in MC-CDMA, comprising:
-
(a) extracting parallel chip sequences received over subcarriers from a received signal, using Discrete Fourier transform or Fast Fourier Transform;
(b) converting the parallel chip sequences extracted in (a) into a single chip sequence using a parallel-to-serial conversion, and performing a direct despreading for the single chip sequence using the same spreading code and chip rate as those used by the transmitting side; and
(c) sequentially combining chip samples, obtained in (b), corresponding to the number of chips to be combined, R, which is determined by a variable spreading factor SF, to generate a received modulated symbol. - View Dependent Claims (18, 19, 20, 21, 22)
-
-
23. A spreading/despreading method in MC-CDMA, comprising:
-
a spreading step of repeating each symbol of a modulated symbol sequence, for spreading in a signal forming procedure of MC-CDMA, by the number of symbol repetition, R, which is determined by a variable spreading factor, performing a direct spreading for the repeated symbols using a spreading code, demultiplexing the spread symbol into as many parallel chip sequences as there are subcarriers, SFF, and transforming the parallel chips into a transmission symbol over SFF subcarriers by using inverse DFT or FFT; and
a despreading step of extracting parallel chip sequences received over subcarriers from a received signal using DFT or FFT, multiplexing the parallel chip sequences into a single chip sequence, performing a direct despreading for the single chip sequence using the same spreading code and code rate as those used by the transmitting side, and sequentially combining the despread chip samples corresponding to the number of chips to be combined, R, which is determined by the variable spreading factor, SF, to output a received modulated symbol. - View Dependent Claims (24, 25)
-
Specification