Pilot signal in an FDMA communication system
AssigneeFreescale Semiconductor, Inc.
InventorJames McCoy
Life of this patent
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Abstract
Methods (500, 800) and corresponding systems (100, 200, 300, 400, 900) for generating a pilot symbol (330) include providing an M-point parallel transform sequence that is a discrete Fourier transform of a CAZAC sequence (312, 504-508). The M-point parallel transform sequence (312) is distributed (316, 510) to a set of M subcarriers among N subcarriers to form an N-point frequency-domain sequence (318) wherein the M subcarriers are evenly spaced apart. An N-point inverse fast Fourier transform (320, 512) is performed to convert the N-point frequency-domain sequence to an N-point time-domain sequence (322). The N-point time-domain sequence is converted (324, 514) to a serial sequence (326), and a cyclic prefix is added (328, 516) to the serial sequence to form a pilot symbol (330).
Claims21
A method for generating a pilot symbol in a single carrier frequency division multiple access (SC-FDMA) transmitter comprising:
- providing an M-point parallel transform sequence that is a discrete Fourier transform of a constant-amplitude zero-autocorrelation (CAZAC) sequence;
- distributing the M-point parallel transform sequence to a set of M subcarriers among N subcarriers to form an N-point frequency-domain sequence, wherein N is greater than M, and wherein the M subcarriers are evenly spaced apart;
- performing an N-point inverse fast Fourier transform to convert the N-point frequency-domain sequence to an N-point time-domain sequence;
- converting the N-point time-domain sequence to a serial sequence;
- and
- adding a cyclic prefix to the serial sequence to form a pilot symbol.
A pilot symbol generator comprising:
- an M-point parallel transform sequence generator for generating an M-point parallel transform sequence derived from a constant-amplitude zero-autocorrelation (CAZAC) sequence;
- a distributed subcarrier mapper coupled to the M-point discrete Fourier transformer for mapping the M-point parallel transform sequence onto a set of M selected subcarriers of N subcarriers to produce an N-point distributed transformed sequence, wherein N is greater than M, and wherein the set of M selected subcarriers are evenly spaced apart;
- an N-point inverse fast Fourier transformer coupled to the distributed subcarrier mapper for transforming the N-point distributed transformed sequence to produce an N-point distributed time-domain sequence;
- a parallel to serial converter coupled to the N-point distributed time-domain sequence for producing a serial N-point distributed time-domain sequence;
- and
- a cyclic prefix adder coupled to the serial N-point distributed time-domain sequence for producing a pilot symbol.
A method for receiving a pilot symbol in an single carrier frequency division multiple access (SC-FDMA) receiver comprising:
- removing a cyclic prefix from a received pilot waveform to produce a modified pilot waveform;
- converting the modified pilot waveform into an N-point parallel modified pilot symbol;
- performing an N-point fast Fourier transform on the N-point parallel modified pilot symbol to produce a received transformed pilot symbol;
- demapping M distributed subcarriers in the received transformed pilot symbol to produce an M-point received pilot signal;
- multiplying the M-point received pilot signal by an M-point channel estimate multiplier to produce an M-point intermediate channel estimate, wherein the M-point channel estimate multiplier is derived from a constant-amplitude zero-autocorrelation (CAZAC) sequence;
- and
- performing a two dimensional interpolation on the M-point intermediate channel estimate to produce a final channel estimate.
A pilot symbol receiver comprising:
- a cyclic prefix remover for removing a cyclic prefix from a received waveform to produce a modified pilot waveform;
- a serial to parallel converter coupled to the modified pilot waveform for producing an N-point parallel modified pilot symbol;
- an N-point fast Fourier transformer coupled to the serial to parallel converter for performing an N-point fast Fourier transform on the N-point parallel modified pilot symbol to produce a received transformed pilot symbol;
- a distributed subcarrier demapper coupled to the N-point fast Fourier transformer for demapping M distributed subcarriers in the received transformed pilot symbol to produce an M-point received pilot signal;
- and
- a multiplier coupled to the distributed subcarrier demapper for multiplying the M-point received pilot signal by an M-point channel estimate multiplier to produce an M-point intermediate channel estimate, wherein the M-point channel estimate multiplier is derived from a constant-amplitude zero-autocorrelation (CAZAC) sequence;
- and
- a two dimensional interpolator coupled to the multiplier for performing a two dimensional interpolation on the M-point intermediate channel estimate to produce a final channel estimate.
Dependencies are inferred from the claim text.