Apparatus and Method for Inserting a Cyclic Postfix for a Time-Rotated Symbol in a Communication System

• US 20100303166A1
• Filed: 05/29/2009
• Published: 12/02/2010
• Est. Priority Date: 05/29/2009
• Status: Active Grant

• Current Assignee: WSOU Investments, LLC (WSOU Holdings, LLC)
• Original Assignee: Nokia Corporation
• Inventors: Piedras, Alberto Escolar
• Granted Patent: US 8,331,468 B2
• Time in Patent Office: Days
• US Class Current: 375/267
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2636 with FFT or DFT modulators, e.g. standard single-carrier frequency-division multiple access [SC-FDMA] transmitter or DFT spread orthogonal frequency division multiplexing [DFT-SOFDM]

Abstract

An apparatus and method for inserting a cyclic postfix for a time-rotated symbol in a communication system. In one embodiment, the apparatus includes a time pre-rotation module configured to time shift bits of at least one of ending samples of a symbol to a beginning of the symbol to form a time-rotated symbol. The apparatus also includes an interpolator configured to construct an up-sampled symbol from the time-rotated symbol and a cyclic postfix module configured to insert a cyclic postfix at an end of the up-sampled symbol to form an expanded up-sampled symbol.

Claims

1. An apparatus, comprising:

time pre-rotation module configured to time shift bits of at least one of ending samples of a symbol to a beginning of said symbol to form a time-rotated symbol;

an interpolator configured to construct an up-sampled symbol from said time-rotated symbol; and

a cyclic postfix module configured to insert a cyclic postfix at an end of said up-sampled symbol to form an expanded up-sampled symbol.

2. The apparatus as recited in claim 1 wherein said bits of said at least one of said ending samples comprises all of said bits thereof.

3. The apparatus as recited in claim 1 wherein said cyclic postfix comprises at least one of initial samples of said up-sampled symbol.

4. The apparatus as recited in claim 1 further comprising a modulator configured to map data into complex-valued constellation samples and aggregate said samples into said symbol.

5. The apparatus as recited in claim 1 wherein said time pre-rotation module is configured to apply a phase correction to samples of said symbol in accordance with forming said time-rotated symbol.

6. The apparatus as recited in claim 1 wherein said interpolator, comprises:

a discrete Fourier transform module configured to map said time-rotated symbol into complex-valued samples in a frequency plane, and

an inverse discrete Fourier transform module configured to construct said up-sampled symbol in a time domain from said complex-valued samples.

7. The apparatus as recited in claim 6 wherein a length of said cyclic postfix is a function of a ratio of a number of coefficients of an inverse discrete Fourier transform employed by said inverse discrete Fourier transform module to a number of coefficients of a discrete Fourier transform employed by said discrete Fourier transform module and corrected for fractional numbers.

8. The apparatus as recited in claim 6 wherein said interpolator is configured to apply a phase correction to at least one of samples of said time-rotated symbol, said complex-valued samples and samples of said up-sampled symbol.

9. The apparatus as recited in claim 1 wherein said time pre-rotation module, said interpolator and said cyclic postfix module are embodied in at least one of a processor and a transceiver.

10. The apparatus as recited in claim 1 wherein said apparatus is operable in a single carrier-frequency division multiple access communication system.

11. An apparatus, comprising:

means for time shifting bits of at least one of ending samples of a symbol to a beginning of said symbol to form a time-rotated symbol;

means for constructing an up-sampled symbol from said time-rotated symbol; and

means for inserting a cyclic postfix at an end of said up-sampled symbol to form an expanded up-sampled symbol.

12. The apparatus as recited in claim 11 wherein said means for constructing, comprises:

means for mapping said time-rotated symbol into complex-valued samples in a frequency plane, and

means for constructing said up-sampled symbol in a time domain from said complex-valued samples.

13. A computer program product comprising a program code stored in a computer readable medium configured to shift bits of at least one of ending samples of a symbol to a beginning of said symbol to form a time-rotated symbol, construct an up-sampled symbol from said time-rotated symbol, and insert a cyclic postfix at an end of said up-sampled symbol to form an expanded up-sampled symbol.

14. The computer program product as recited in claim 13 wherein said program code stored in said computer readable medium is configured to construct said up-sampled symbol by mapping said time-rotated symbol into complex-valued samples in a frequency plane, and constructing said up-sampled symbol in a time domain from said complex-valued samples.

15. A method, comprising:

time shifting bits of at least one of ending samples of a symbol to a beginning of said symbol to form a time-rotated symbol;

constructing an up-sampled symbol from said time-rotated symbol; and

inserting a cyclic postfix at an end of said up-sampled symbol to form an expanded up-sampled symbol.

16. The method as recited in claim 15 wherein said bits of said at least one of said ending samples comprises all of said bits thereof.

17. The method as recited in claim 15 wherein said cyclic postfix comprises at least one of initial samples of said up-sampled symbol.

18. The method as recited in claim 15 further comprising mapping data into complex-valued constellation samples and aggregating said samples into said symbol.

19. The method as recited in claim 15 wherein said constructing said up-sampled symbol, comprises:

mapping said time-rotated symbol into complex-valued samples in a frequency plane, and

constructing said up-sampled symbol in a time domain from said complex-valued samples.

20. The method as recited in claim 19 further comprising applying a phase correction to at least one of samples of said time-rotated symbol, said complex-valued samples and samples of said up-sampled symbol.