Method and Apparatus for Generating and Receiving Ofdm Symbol

• US 20090003478A1
• Filed: 01/12/2007
• Published: 01/01/2009
• Est. Priority Date: 01/13/2006
• Status: Active Grant

• Current Assignee: KT Corporation, SK Telecom Co., Ltd.
• Original Assignee: Electronics and Telecommunications Research Institute
• Inventors: Jwa, Hye-Kyung, Bang, Seung-Chan, Kim, Nam-Il, Kim, Young-Hoon, Kim, Il-Gyu
• Granted Patent: US 8,102,927 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04L 27/2614 Peak power aspects
• CPC Class Codes: H04L 27/2615 Reduction thereof using coding

Abstract

The present invention provides an OFDM symbol generating apparatus. The OFDM symbol generating apparatus generates a plurality of weight-applied symbol groups by applying a plurality of weights to a digital modulation symbol group, and generates a plurality of IFFT symbol groups by performing an IFFT operation on the plurality of weight-applied symbol groups. Subsequently, an IFFT symbol group having the minimum PAPR is selected from among the plurality of IFFT symbol groups such that a characteristic of a PAPR can be improved without reducing data transmission speed.

Claims

1. An apparatus for generating an orthogonal frequency division multiplexing (OFDM) symbol, the apparatus comprising:

a plurality of weight applying units respectively corresponding to a plurality of weights, and generating a weight-applied symbol group by applying a corresponding weight to each symbol of a digital modulation symbol group;

a plurality of inverse fast Fourier transform (IFFT) operators respectively corresponding to the plurality of weight applying units, and generating an IFFT symbol group by performing an IFFT operation on the weight-applied symbol group generated by a corresponding weight applying unit; and

a signal selector for selecting an IFFT symbol group having the minimum PAPR among a plurality of IFFT symbol groups generated by the plurality of IFFT operators.

2. The apparatus of claim 1, wherein the plurality of weights respectively correspond to a plurality of phase weights.

3. The apparatus of claim 2, wherein a portion or all of the plurality of weight applying units divide the digital modulation symbol group into a first sub-group and a second sub-group, and apply the phase weight to one of the first sub-group and the second sub-group.

4. The apparatus of claim 3, further comprising a digital modulator for generating the digital modulation symbol group by performing quadrature phase shift modulation (QAM) on a plurality of data symbols,

wherein the plurality of weight applying units comprise:

a first weight applying unit for applying a phase weight of 0 to the digital modulation symbol group; and

a second weight applying unit for applying a phase weight of π

/4 to the first sub-group and applying the phase weight of 0 to the second sub-group.

5. The apparatus of claim 4, wherein the plurality of weight applying units further comprise a third weight applying unit for applying a phase weight of 0 to the first sub-group and applying a phase weight of π

/4 to the second sub-group.

6. The apparatus of claim 3, further comprising a digital modulator for generating the digital modulation symbol group by performing binary phase shift keying (BPSK) modulation on a plurality of data symbols,

wherein the plurality of weight applying units comprise:

a first weight applying unit for applying a phase weight of 0 to the digital modulation symbol group; and

a second weight applying unit for applying a phase weight of π

/2 to the first sub-group and applying a phase weight of 0 to the second sub-group.

7. The apparatus of claim 6, wherein the plurality of weight applying units further comprise a third weight applying unit for applying a phase weight of 0 to the first sub-group and applying a phase weight of π

/2 to the second sub-group.

8. The apparatus of claim 4, wherein the first sub-group includes odd symbols of the digital modulation symbol group, and the second sub-group includes even symbols of the digital modulation symbol group.

9. The apparatus of claim 1, wherein the apparatus comprises:

a plurality of fast Fourier transform (FFT) operators respectively corresponding to the plurality of weight applying units, and performing an FFT operation on a weight-applied symbol group generated by a corresponding weight applying unit so as to generate an FFT symbol group;

a plurality of subcarrier allocators respectively corresponding to the plurality of FFT operators, and allocating a plurality of subcarriers to the FFT symbol group generated by a corresponding FFT operator so as to generate a subcarrier allocation symbol group; and

a plurality of inverse fast Fourier transform (IFFT) operators respectively corresponding to the plurality of subcarrier allocators, performing IFFT on a subcarrier allocation symbol group generated by a corresponding subcarrier allocator so as to generate an IFFT symbol group.

10. The apparatus of claim 9, further comprising:

a guard interval adder for adding a guard interval to an IFFT symbol group output from the signal selector so as to generate a guard interval-added symbol group;

a windowing controller for eliminating a radio frequency component from the guard interval-added symbol group so as to generate a windowing symbol group; and

a transmission unit for converting the windowing symbol group into an analog signal so as to generate an orthogonal division multiplexing (OFDM) symbol, amplifying the OFDM symbol, and transmitting the amplified OFDM symbol to a channel.

11. An apparatus for receiving an orthogonal frequency division multiplexing (OFDM) symbol and outputting a data symbol, the apparatus comprising:

a digital converter for outputting a digital symbol group by converting the OFDM symbol into a digital signal;

a fast Fourier transform (FFT) operator for outputting an FFT symbol group by performing an FFT operation on the digital symbol group;

a signal recovery unit for estimating a weight applied to the FFT symbol group, compensating the estimated weight, and outputting a weight compensation symbol group; and

a digital demodulator for demodulating the weight compensation symbol group and outputting the demodulated data symbol.

12. The apparatus of claim 11, wherein the weight corresponds to a phase weight, and the signal recovery unit estimates the phase weight applied to the FFT symbol group and compensates the estimated phase weight.

13. The apparatus of claim 12, wherein the signal recovery unit estimates the phase weight based on a first sub-group and a second sub-group included in the FFT symbol group and compensates the estimated phase weight.

14. The apparatus of claim 13, wherein the signal recovery unit estimates the phase weight based on a phase distribution pattern difference between the first sub-group and the second sub-group and compensates the estimated phase weight.

15. The apparatus of claim 11, wherein the apparatus comprises:

a subcarrier deallocator for outputting a subcarrier deallocation symbol group by deallocating the FFT symbol group for each subcarrier;

a channel estimator for outputting a channel estimation symbol group by compensating distortion of the subcarrier deallocation symbol group;

an inverse fast Fourier transform (IFFT) operator for outputting an IFFT symbol group by performing an IFFT operation on the channel estimation symbol group; and

a signal recovery unit for estimating a weight applied to the IFFT symbol group, compensating the weight, and outputting a weight compensation symbol group.

16. The apparatus of claim 15, further comprising:

a guard interval eliminator outputting a guard interval -eliminated symbol group by eliminating a guard interval from the digital symbol group; and

an FFT operator for outputting an FFT symbol group by performing an FFT operation on the guard interval-eliminated symbol group.

17. A method for generating an orthogonal frequency division multiplexing (OFDM) symbol, the method comprising:

generating a plurality of weight-applied symbol groups respectively corresponding to a plurality of weights by applying the plurality of weights to a plurality of digital modulation symbol groups;

generating a plurality of IFFT symbol groups, respectively corresponding to the plurality of weight-applied groups by performing inverse fast Fourier transform (IFFT) on the plurality of weight-applied symbol groups; and

selecting an IFFT symbol group having the minimum PAPR among the plurality of IFFT symbol groups and outputting the selected IFFT symbol group.

18. The method of claim 17, wherein the plurality of weights correspond to a plurality of phase weights, and

the generating of the plurality of weight-applied symbol groups comprises:

dividing the digital modulation symbol groups into a first sub-group and a second sub-group; and

generating a portion or all of the plurality of weight-applied symbol groups by applying a phase weight to one of the first sub-group and the second sub-group.

19. The method of claim 17, wherein the method comprises:

generating a plurality of FFT symbol groups by performing FFT on the plurality of weight-applied symbol groups;

generating a plurality of subcarrier allocation symbol groups by allocating a plurality of subcarriers to the plurality of FFT symbol groups; and

generating a plurality of IFFT symbol group by performing IFFT on the plurality of subcarrier allocation symbol groups.

20. The method of claim 19, further comprising:

generating a guard interval-added symbol group by adding a guard interval to the IFFT symbol group having the minimum PAPR;

generating a windowing symbol group by eliminating a radio frequency component from the guard interval-added symbol group; and

converting the windowing symbol group into an analog signal, amplifying the windowing symbol group that has been converted into the analog signal, and transmitting the amplified the windowing symbol group to a channel.

21. A method for receiving an orthogonal frequency division multiplexing (OFDM) symbol and outputting a data symbol, the method comprising:

converting the OFDM symbol into a digital signal and outputting a digital symbol group;

transforming the digital symbol group by performing a fast Fourier transform (FFT) operation and outputting an FFT symbol group;

estimating a weight applied to the FFT symbol group, compensating the weight, and outputting a weight compensation symbol group; and

digitally demodulating the weight compensation symbol group and outputting the data symbol.

22. The method of claim 21, wherein the weight corresponds to a phase weight, and the outputting of the weight compensation symbol group comprises estimating the phase weight applied to the FFT symbol group and compensating the estimated phase weight.

23. The method of claim 22, wherein the outputting of the weight compensation symbol group comprises:

estimating the phase weight based on a phase distribution pattern of a first sub-group and a phase distribution pattern of a second sub-group, the first sub-group and the second sub-group included in the FFT symbol group; and

compensating the estimated phase weight.

24. The method of claim 21, wherein the method comprises:

deallocating the FFT symbol group for each subcarrier and outputting a subcarrier deallocation symbol group;

compensating distortion of the subcarrier deallocation symbol group and outputting a channel estimation symbol group;

performing an inverse FFT (IFFT) operation on the channel-estimated symbol group and outputting an IFFT symbol group; and

estimating a weight applied to the IFFT symbol group, compensating the weight, and outputting a weight compensation symbol group.

25. The method of claim 24, further comprising:

eliminating a guard interval from the digital symbol group and outputting a guard interval-eliminated symbol group; and

performing an FFT operation on the guard interval-eliminated symbol group and outputting an FFT symbol group.