Apparatus and method for FT pre-coding of data to reduce PAPR in a multi-carrier wireless network

Abstract

A subscriber station for use in a wireless network capable of communicating according to a multi-carrier protocol, such as OFDM or OFDMA. The subscriber station comprises a size M Fourier Transform (FFT or DFT) block for receiving input symbols and generating M FT pre-coded outputs and a size N inverse Fourier Transform (IFFT or IDFT) block capable of receiving N inputs, where the N inputs include the M FT pre-coded outputs from the size M FT block. The size N IFT block generates N outputs to be transmitted to a base station of the wireless network. The input symbols comprise user data traffic to be transmitted to the base station. The size N IFT block also receives signaling and control information on at least some of N-M inputs. The FT pre-coding generates a time-domain signal that has a relatively lower peak-to-average power ratio (PAPR).

What is claimed is: 
     
       1. For use in a wireless network, a subscriber station capable of communicating with the wireless network according to a multi-carrier protocol, the subscriber station comprising:
 a size M Fourier Transform (FT) block capable of receiving input symbols and generating therefrom M FT pre-coded outputs, the input symbols comprising data signals and pilot signals; and 
 a size N inverse Fourier Transform (IFT) block capable of receiving N inputs, the N inputs including the M FT pre-coded outputs from the size M FT block, and generating therefrom N outputs to be transmitted to a base station of the wireless network, wherein the size M FT block and the size N IFT block are one of: 1) a Fast Fourier Transform (FFT) block and an inverse Fast Fourier Transform (IFFT) block; and 2) a Discrete Fourier Transform (DFT) block and an inverse Discrete Fourier Transform (IDFT) block, 
 wherein the data signals and pilot signals are mapped to alternating subcarriers and the size N IFT block receives signaling and control information on at least some of the N inputs other than the M FT pre-coded outputs. 
 
     
     
       2. The subscriber station as set forth in  claim 1 , wherein the signaling and control information comprises a pilot signal. 
     
     
       3. The subscriber station as set forth in  claim 1 , wherein the size N IFT block receives only the M FT pre-coded outputs during selected time slots and receives only the signaling and control information during other selected time slots. 
     
     
       4. The subscriber station as set forth in  claim 1 , wherein the multi-carrier protocol comprises one of orthogonal frequency division multiplexing and orthogonal frequency division multiple access. 
     
     
       5. The subscriber station as set forth in  claim 1 , wherein the input symbols further comprise a pilot signal. 
     
     
       6. The subscriber station as set forth in  claim 5 , wherein the size N IFT block receives signaling and control information on at least some of the N inputs other than the M FT pre-coded outputs further comprising a switch configured to couple the size M FT block to the size N IFT. 
     
     
       7. The subscriber station as set forth in  claim 6 , wherein the size N IFT block receives only the M FT pre-coded outputs during selected time slots and receives only the signaling and control information during other selected time slots. 
     
     
       8. The subscriber station as set forth in  claim 7 , wherein the signaling and control information comprises a pilot signal. 
     
     
       9. The subscriber station as set forth in  claim 6 , wherein the multi-carrier protocol comprises one of orthogonal frequency division multiplexing and orthogonal frequency division multiple access. 
     
     
       10. For use in a subscriber station capable of communicating with a wireless network according to a multi-carrier protocol, a method for reducing the peak-to-average power ration (PAPR) of a radio frequency signal transmitted by the subscriber station to a base station of the wireless network, the method comprisingthe steps of:
 receiving input symbols to be transmitted to the base station, the input symbols comprising data signals and pilot signals; 
 performing a size M Fourier Transform (FT) operation on the received input symbols to thereby generate M FT pre-coded outputs; and 
 performing a size N inverse Fourier Transform (IFT) operation on N inputs, the N inputs including the M FT pre-coded outputs, to thereby generate N outputs to be transmitted to the base station, wherein the size M FT operation and the size N IFT operation are one of: 1) a Fast Fourier Transform (FFT) operation and an inverse Fast Fourier Transform (IFFT) operation; and 2) a Discrete Fourier Transform (DFT) operation and an inverse Discrete Fourier Transform (IDFT) operation mapping the data signals and pilot signals to alternating subcarriers, wherein the size N IFT operation receives signaling and control information on at least some of the N inputs other than the M FT pre-coded outputs. 
 
     
     
       11. The method as set forth in  claim 10 , wherein the signaling and control information comprises a pilot signal. 
     
     
       12. The method as set forth in  claim 10 , wherein the size N IFT operation is performed only on the M FT pre-coded outputs during selected time slots and is performed only on the signaling and control information during other selected time slots. 
     
     
       13. The method as set forth in  claim 10 , wherein the multi-carrier protocol comprises one of orthogonal frequency division multiplexing and orthogonal frequency division multiple access. 
     
     
       14. The method as set forth in  claim 10 , wherein the input symbols further comprise a pilot signal. 
     
     
       15. The method as set forth in  claim 14 , wherein the size N IFT operation receives signaling and control information on at least some of the N inputs other than the M FT pre-coded outputs. 
     
     
       16. The method as set forth in  claim 15 , wherein the size N IFT operation is performed only on the M FT pre-coded outputs during selected time slots and is performed only on the signaling and control information during other selected time slots. 
     
     
       17. The method as set forth in  claim 16 , wherein the signaling and control information comprises a pilot signal. 
     
     
       18. The method as set forth in  claim 15 , wherein the multi-carrier protocol comprises one of orthogonal frequency division multiplexing and orthogonal frequency division multiple access. 
     
     
       19. A base station for use in a wireless network capable of communicating with subscriber stations according to a multi-carrier protocol, the base station comprising:
 down-conversion circuitry capable of receiving incoming radio frequency signals from the subscriber stations and generating therefrom a baseband signal; 
 a size N Fourier Transform (FT) block capable of receiving the baseband signal on N inputs and performing an FT operation to generate N outputs; 
 a size M Inverse Fourier Transform (IFT) block capable of receiving M of the N outputs of the size N FT block and performing a size M IFT operation on the M outputs to generate a plurality of data symbols transmitted by a first one of the subscriber stations, wherein the size N FT block and the size M IFT block are one of 1) a Fast Fourier Transform (FFT) block and an inverse Fast Fourier Transform (IFFT) block; and 2) a Discrete Fourier Transform (DFT) block and an inverse Discrete Fourier Transform (IDFT) block; and 
 a frequency-domain equalizer capable of receiving a pilot signal transmitted by the first subscriber station and using the pilot signal to perform frequency-domain equalization on the M outputs of the size N FT block prior to the size M IFT operation of the size M IFT block wherein the size N FT block generates on at least some of the N outputs signaling and control information transmitted by the first subscriber station. 
 
     
     
       20. The base station as set forth in  claim 19 , wherein the signaling and control information transmitted by the first subscriber station comprises the pilot signal. 
     
     
       21. The base station as set forth in  claim 20 , wherein the data symbols transmitted by the first subscriber station are pre-coded. 
     
     
       22. A method for use in base station of a wireless network capable of communicating with subscriber stations according to a multi-carrier protocol, the method comprisingthe steps of:
 receiving incoming radio frequency (RF) signals from the subscriber stations; 
 down-converting the incoming RF signals to generate a baseband signal; 
 performing a size N Fourier Transform (FT) operation on the baseband signal to generate N outputs; 
 performing a size M Inverse Fourier Transform (IFT) operation on M of the N outputs of the size N FT operation to generate a plurality of data symbols transmitted by a first one of the subscriber stations, wherein the size N FT operation and the size M IFT operation are one of: 1) a Fast Fourier Transform (FFT) operation and an inverse Fast Fourier Transform (LEFT) operation; and 2) a Discrete Fourier Transform (DFT) operation and an inverse Discrete Fourier Transform (IDFT) operation; and 
 using a pilot signal transmitted by the first subscriber station to perform frequency-domain equalization on the M outputs of the size N FT operation prior to the size M IFT operation, wherein the size N FT operation generates on at least some of the N outputs signaling and control information transmitted by the first subscriber station. 
 
     
     
       23. The method as set forth in  claim 22 , wherein the signaling and control information transmitted by the first subscriber station comprises the pilot signal. 
     
     
       24. The method as set forth in  claim 23 , wherein the data symbols transmitted by the first subscriber station are pre-coded. 
     
     
       25. A wireless network comprising a plurality of base stations capable of communicating with subscriber stations according to a multi-carrier protocol, each of the base stations comprising:
 down-conversion circuitry capable of receiving incoming radio frequency signals from the subscriber stations and generating therefrom a baseband signal; 
 a size N Fourier Transform (FT) block capable of receiving the baseband signal on N inputs and performing an IFT operation to generate N outputs; 
 a size M Inverse Fourier Transform (IFT) block capable of receiving M of the N outputs of the size N FT block and performing a size M IFT operation on the M outputs to generate a plurality of data symbols transmitted by a first one of the subscriber stations, wherein the size N FT block and the size M IFT block are one of: 1) a Fast Fourier Transform (FFT) block and an inverse Fast Fourier Transform (IFFT) block; and 2) a Discrete Fourier Transform (DFT) block and an inverse Discrete Fourier Transform (IDFT) block; and 
 a frequency-domain equalizer capable of receiving a pilot signal transmitted by the first subscriber station and using the pilot signal to perform frequency-domain equalization on the M outputs of the size N FT block prior to the size M IFT operation of the size M IFT block wherein the size N FT block generates on at least some of the N outputs signaling and control information transmitted by the first subscriber station. 
 
     
     
       26. The wireless network as set forth in  claim 25 , wherein the signaling and control information transmitted by the first subscriber station comprises the pilot signal. 
     
     
       27. The wireless network as set forth in  claim 26 , wherein the data symbols transmitted by the first subscriber station are pre-coded. 
     
     
       28. A data transmission method in a communication system, the method comprising:
 modulating data information to generate non-FT pre-coded modulation data symbols;   modulating control information to generate non-FT pre-coded modulation control symbols;   Fourier Transform (FT) pre-coding the non-FT pre-coded modulation data symbols to generate FT pre-coded symbols;   mapping the FT pre-coded symbols to a first set of subcarriers;   mapping the non-FT pre-coded modulation control symbols to a second set of subcarriers;   performing an inverse Fourier Transform (IFT) operation on at least one of (i) the FT pre-coded symbols based on the first set of subcarriers and (ii) the non-FT pre-coded modulation control symbols based on the second set of subcarriers to generate an output signal; and   transmitting the output signal.   
     
     
       29. The method of claim 28, wherein FT pre-coding comprises performing an M point FT operation, performing the IFT operation comprising performing an N point IFT operation, and N is not less than M. 
     
     
       30. The method of claim 28, wherein performing the IFT operation comprises performing the IFT operation on both the FT pre-coded symbols based on the first set of subcarriers and the non-FT pre-coded modulation control symbols based on the second set of subcarriers. 
     
     
       31. The method of claim 28, wherein performing the IFT operation comprising, based on time multiplexing, performing the IFT operation on one of (i) the FT pre-coded symbols based on the first set of subcarriers and (ii) the non-FT pre-coded modulation control symbols based on the second set of subcarriers. 
     
     
       32. The method of claim 30, wherein the control information comprises at least one of a pilot signal, a resource request, a random access, Channel Quality Indicator (CQI) and a feedback for hybrid automatic repeat request (HARQ). 
     
     
       33. A method for receiving data in a communication system, the method comprising:
 receiving a transmitted signal;   performing a Fourier Transform (FT) operation on the received signal to generate N outputs, wherein a first subset of the N outputs comprises FT pre-coded modulated data symbols and a second subset of the N outputs comprises non-FT pre-coded modulated control symbols;   demapping the first subset of outputs;   performing Inverse Fourier Transform (IFT) operation on the demapped outputs to recover modulated data symbols; and   demodulating the modulated data symbols.   
     
     
       34. The method of claim 33, wherein the first subset further comprises FT pre-coded modulated control symbols, wherein performing the IFT operation further comprises performing the IFT operation to recover modulated control symbols, and the method further comprising demodulating the modulated control symbols. 
     
     
       35. The method of claim 33, further comprising:
 recovering the non-FT pre-coded modulated control symbols from the second subset of the N outputs; and   demodulating the non-FT pre-coded modulated control symbols.   
     
     
       36. The method of claim 35, wherein the first subset of the N outputs further comprises a pilot signal, wherein the second subset of the N outputs comprises control information other than the pilot signal, wherein performing the IFT operation further comprises performing the IFT operation to recover modulated pilot symbols, and the method further comprising demodulating the modulated pilot symbols. 
     
     
       37. The method of claim 33, wherein the non-FT pre-coded modulated control symbols comprise control information, and wherein the control information comprises at least one of a pilot signal, a resource request, a random access, Channel Quality Indicator (CQI) and a feedback for HARQ. 
     
     
       38. An apparatus for data transmission in a communication system, the apparatus comprising:
 a modulation block configured to modulate data information to generate non-FT pre-coded modulation data symbols and control information to generate non-FT pre-coded modulation control symbols;   a Fourier Transform (FT) block configured to FT pre-code the non-FT pre-coded modulation data symbols to generate FT pre-coded symbols;   a subcarrier mapping block configured to map the FT pre-coded symbols to a first set of subcarriers and the non-FT pre-coded modulation control symbols to a second set of subcarriers; and   an inverse FT (IFT) block configured to perform an IFT operation on at least one of (i) the FT pre-coded symbols based on the first set of subcarriers and (ii) the non-FT pre-coded modulation control symbols based on the second set of subcarriers to generate an output signal,   wherein the apparatus is configured to transmit the output signal.   
     
     
       39. The apparatus of claim 38, wherein the FT block performs an M point FT operation, the IFT block performs an N point IFT operation, and N is not less than M. 
     
     
       40. The apparatus of claim 38, wherein the IFT block is configured to perform the IFT operation on both the FT pre-coded symbols based on the first set of subcarriers and the non-FT pre-coded modulation control symbols based on the second set of subcarriers. 
     
     
       41. The apparatus of claim 38, wherein based on time multiplexing, the IFT block is configured to perform the IFT operation on one of (i) the FT pre-coded symbols based on the first set of subcarriers and (ii) the non-FT pre-coded modulation control symbols based on the second set of subcarriers. 
     
     
       42. The apparatus of claim 40, wherein the control information comprises at least one of a pilot signal, a resource request, a random access, Channel Quality Indicator (CQI) and a feedback for hybrid automatic repeat request (HARQ). 
     
     
       43. An apparatus for receiving data in a communication system, the apparatus comprising:
 a Fourier Transform (FT) block configured to perform an FT operation on a received signal to generate N outputs, wherein a first subset of the N outputs comprises FT pre-coded modulated data symbols and a second subset of the N outputs comprises non-FT pre-coded modulated control symbols;   an inverse FT (IFT) block configured to perform IFT operations on M inputs, wherein M is less than N;   a subcarrier demapping block configured to receive the first subset of the N outputs from the FT block and to demap the first subset of outputs to the inputs of the IFT block, wherein the IFT block is further configured to perform an IFT operation on the inputs to recover modulated data symbols; and   a demodulation block configured to demodulate the modulated data symbols.   
     
     
       44. The apparatus of claim 43, wherein the first subset further comprises FT pre-coded modulated control symbols, wherein the IFT block is further configured to perform an IFT operation on the inputs to recover modulated control symbols, and wherein the demodulation block is further configured to demodulate the modulated control symbols. 
     
     
       45. The apparatus of claim 43, wherein the demodulation block is further configured to demodulate the non-FT pre-coded modulated control symbols. 
     
     
       46. The apparatus of claim 45, wherein the first subset of the N outputs further comprises a pilot signal, wherein the second subset of the N outputs comprises control information other than the pilot signal, wherein the IFT block is further configured to perform the IFT operation to recover modulated pilot symbols, and wherein the demodulator is further configured to demodulate the modulated pilot symbols. 
     
     
       47. The apparatus of claim 43, wherein the non-FT pre-coded modulated control symbols comprise control information, and wherein the control information comprises at least one of a pilot signal, a resource request, a random access, Channel Quality Indicator (CQI) and a feedback for HARQ.