Time varying delay diversity of OFDM

• US 8,233,555 B2
• Filed: 03/10/2005
• Issued: 07/31/2012
• Est. Priority Date: 05/17/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Naguib, Ayman Fawzy, Agrawal, Avneesh
• Primary Examiner(s): Fotakis, Aristocratis
• Application Number:
  US11/078,176
• Publication Number:
  US 20050254592A1
• Time in Patent Office: 2,700 Days
• Field of Search: 375/260, 375/267, 375/347, 375/348, 375/299, 455/562.1, 455/101, 455/103
• US Class Current: 375/267
• CPC Class Codes: H04B 7/0417 Feedback systems
• CPC Class Codes: H04B 7/0632 Channel quality parameters, e.g. channel quality indicator [CQI]
• CPC Class Codes: H04B 7/0671 using different delays between antennas
• CPC Class Codes: H04B 7/0673 using feedback from receiving side
• CPC Class Codes: H04L 1/0003 by switching between different modulation schemes
• CPC Class Codes: H04L 1/0009 by adapting the channel coding H04L1/1812 takes precedence
• CPC Class Codes: H04L 1/0026 Transmission of channel quality indication
• CPC Class Codes: H04L 1/0071 Use of interleaving interleaving per se H03M13/27
• CPC Class Codes: H04L 1/0618 Space-time coding
• CPC Class Codes: H04L 25/0224 using sounding signals
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2634 Inverse fast Fourier transform [IFFT] or inverse discrete Fourier transform [IDFT] modulators in combination with other circuits for modulation
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04W 52/42 in systems with time, space, frequency or polarisation diversity

Abstract

Methods and apparatuses that apply a time-varying delay to symbols to be transmitted from one or more antennas are provided. One such method may include providing a first symbol comprising a first plurality of samples to a first antenna. The first symbol is provided to a second antenna after a first delay period. A second symbol comprising a second plurality of samples is provided to the first antenna. The second symbol is provided to the second antenna after a second delay period that is different than the first delay period.

Claims

1. A wireless transmitter, comprising:

at least three antennas; and

a memory coupled with the at least three antennas, the memory storing a plurality of symbols each comprising a plurality of samples,

wherein the plurality of samples of a first symbol of the plurality of symbols are provided to one antenna of the at least three antennas after a first delay period, and the plurality of samples of a second symbol of the plurality of symbols are provided to the one antenna after a second delay period, wherein the first delay period and the second delay period are different, each of the symbols comprising a cyclic prefix of one or more samples, wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream; and

wherein the plurality of samples of the first symbol are provided to another of the at least three antennas after a third delay period and the plurality of samples of the second symbol are provided to the another antenna after a fourth delay period, wherein the first delay period, second delay period, third delay period, and fourth delay period are all different from each other, wherein the second delay period varies by n*β

samples from the first delay period and the fourth delay period varies by n*(β

+k) samples from the third delay period, where n is a location of a symbol in a symbol stream and β and

k are constants, and wherein time diversity is provided even if a channel is not of itself time selective.

2. The wireless transmitter of claim 1, wherein the memory comprises a buffer.

3. The wireless transmitter of claim 1, further comprising a cyclic prefix generator coupled with the memory that adds the cyclic prefix to each of the plurality of symbols prior to storing the plurality of symbols in memory.

4. The wireless transmitter of claim 1, wherein the delay periods vary according to the defined time varying function that is adjusted based on channel quality indicator feedback that describes channel conditions.

5. The wireless transmitter of claim 1, wherein the delay periods vary according to the defined time varying function that is not adjusted based on channel quality indicator feedback that describes channel conditions.

6. A method for providing transmission diversity in a multi-channel communication system, comprising:

providing, to a first antenna, a first symbol comprising a first plurality of samples;

providing, to a second antenna, the first symbol after a first delay period;

providing, to the first antenna, a second symbol comprising a second plurality of samples;

providing, to the second antenna, the second symbol after a second delay period that is different than the first delay period;

providing, to the first antenna, a third symbol comprising a third plurality of samples;

providing, to the second antenna, the third symbol after a third delay period that is different than the first delay period and the second delay period, each of the symbols comprising a cyclic prefix of one or more samples, wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream, wherein the defined time varying function is sin(x) where x varies from 0 to N−

1 where N is the number of symbols in a frame, burst period or symbol stream, and wherein time diversity is provided even if a channel is not of itself time selective;

modulating the first symbol, second symbol, and third symbol according to different carrier frequencies; and

providing a scalar shift to the first delay period, second delay period, and third delay period.

7. The method of claim 6, wherein the symbols that are delayed according to the defined time varying function and the undelayed symbols are received from a single modulator.

8. The method of claim 7, wherein the ith symbol is transmitted from antenna m according to

9. The method of claim 6, wherein the delay periods vary according to the defined time varying function that is adjusted based on channel quality indicator feedback that describes channel conditions.

10. The method of claim 6, wherein the delay periods vary according to the defined time varying function that is not adjusted based on channel quality indicator feedback that describes channel conditions.

11. The method of claim 6, wherein the first symbol, second symbol, and third symbol are consecutive symbols of a same symbol stream.

12. The method of claim 6, wherein the third symbol is transmitted immediately after the second symbol that is transmitted immediately after the first symbol.

13. The method of claim 6, wherein the first symbol, second symbol, and third symbol are non-consecutive symbols of a same symbol stream.

14. The method of claim 13, wherein the first symbol and second symbol are separated by a number of symbols and the second symbol and the third symbol are separated by the number of symbols.

15. The method of claim 6, wherein the first symbol, second symbol, and third symbol are each transmitted in different frames.

16. A method for use in a wireless transmitter, the method comprising:

with a memory, storing a plurality of symbols each comprising a plurality of samples;

providing the plurality of samples of a first symbol of the plurality of symbols to one antenna of at least three antennas after a first delay period;

providing the plurality of samples of a second symbol of the plurality of symbols to the one antenna after a second delay period, wherein the first delay period and the second delay period are different, each of the symbols comprising a cyclic prefix of one or more samples, and wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream;

providing the plurality of samples of the first symbol to another of the at least three antennas after a third delay period; and

providing the plurality of samples of the second symbol to the another antenna after a fourth delay period,

wherein the first delay period, second delay period, third delay period, and fourth delay period are all different from each other, wherein the second delay period varies by n*β

samples from the first delay period and the fourth delay period varies by n*(β

+k) samples from the third delay period, where n is a location of a symbol in a symbol stream and β and

k are constants, and wherein time diversity is provided even if a channel is not of itself time selective.

17. An apparatus for use in a wireless transmitter, the apparatus comprising:

means for storing a plurality of symbols each comprising a plurality of samples;

means for providing the plurality of samples of a first symbol of the plurality of symbols to one antenna of at least three antennas after a first delay period;

means for providing the plurality of samples of a second symbol of the plurality of symbols to the one antenna after a second delay period, wherein the first delay period and the second delay period are different, each of the symbols comprising a cyclic prefix of one or more samples, and wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream;

means for providing the plurality of samples of the first symbol to another of the at least three antennas after a third delay period; and

means for providing the plurality of samples of the second symbol to the another antenna after a fourth delay period,

wherein the first delay period, second delay period, third delay period, and fourth delay period are all different from each other, wherein the second delay period varies by n*β

samples from the first delay period and the fourth delay period varies by n*(β

+k) samples from the third delay period, where n is a location of a symbol in a symbol stream and β and

k are constants, and wherein time diversity is provided even if a channel is not of itself time selective.

18. An article comprising:

a processor-readable memory having instructions thereon which are executable by a processor in a wireless transmitter to;

access a plurality of symbols each comprising a plurality of samples;

initiate providing the plurality of samples of a first symbol of the plurality of symbols to one antenna of at least three antennas after a first delay period;

initiate providing the plurality of samples of a second symbol of the plurality of symbols to the one antenna after a second delay period, wherein the first delay period and the second delay period are different, each of the symbols comprising a cyclic prefix of one or more samples, and wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream;

initiate providing the plurality of samples of the first symbol to another of the at least three antennas after a third delay period; and

initiate providing the plurality of samples of the second symbol to the another antenna after a fourth delay period,

wherein the first delay period, second delay period, third delay period, and fourth delay period are all different from each other, wherein the second delay period varies by n*β

samples from the first delay period and the fourth delay period varies by n*(β

+k) samples from the third delay period, where n is a location of a symbol in a symbol stream and β and

k are constants, and wherein time diversity is provided even if a channel is not of itself time selective.

19. An apparatus for use in a multi-channel communication system, the apparatus comprising:

a plurality of antennas, comprising at least a first antenna and a second antenna;

a modulator; and

a delay circuit coupled between the modulator and the plurality of antennas, the delay circuit to;

provide, to the first antenna, a first symbol comprising a first plurality of samples;

provide, to the second antenna, the first symbol after a first delay period;

provide, to the first antenna, a second symbol comprising a second plurality of samples;

provide, to the second antenna, the second symbol after a second delay period that is different than the first delay period;

provide, to the first antenna, a third symbol comprising a third plurality of samples; and

provide, to the second antenna, the third symbol after a third delay period that is different than the first delay period and the second delay period, each of the symbols comprising a cyclic prefix of one or more samples,

wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream, wherein the defined time varying function is sin(x) where x varies from 0 to N−

1 where N is the number of symbols in a frame, burst period or symbol stream, and wherein time diversity is provided even if a channel is not of itself time selective, and wherein the first symbol, second symbol, and third symbol are modulated according to different carrier frequencies, and a scalar shift is provided to the first delay period, second delay period, and third delay period.

20. The apparatus of claim 19, wherein the first symbol, second symbol, and third symbol are consecutive symbols of a same symbol stream.

21. The apparatus of claim 19, wherein the third symbol is transmitted immediately after the second symbol that is transmitted immediately after the first symbol.

22. The apparatus of claim 19, wherein the first symbol, second symbol, and third symbol are non-consecutive symbols of a same symbol stream.

23. The apparatus of claim 19, wherein the first symbol and second symbol are separated by a number of symbols and the second symbol and the third symbol are separated by the number of symbols.

24. The apparatus of claim 19, wherein the first symbol, second symbol, and third symbol are each transmitted in different frames.

25. An apparatus for use in a multi-channel communication system,

the apparatus comprising:

means for providing, to a first antenna, a first symbol comprising a first plurality of samples;

means for providing, to a second antenna, the first symbol after a first delay period;

means for providing, to the first antenna, a second symbol comprising a second plurality of samples;

means for providing, to the second antenna, the second symbol after a second delay period that is different than the first delay period;

means for providing, to the first antenna, a third symbol comprising a third plurality of samples; and

means for providing, to the second antenna, the third symbol after a third delay period that is different than the first delay period and the second delay period, each of the symbols comprising a cyclic prefix of one or more samples,

wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream, wherein the defined time varying function is sin(x) where x varies from 0 to N−

1 where N is the number of symbols in a frame, burst period or symbol stream, and wherein time diversity is provided even if a channel is not of itself time selective, and wherein the first symbol, second symbol, and third symbol are modulated according to different carrier frequencies, and a scalar shift is provided to the first delay period, second delay period, and third delay period.

26. An article comprising:

a processor-readable memory having instructions thereon which are executable by a processor in device for use in a multi-channel communication system to;

initiate providing, to a first antenna, a first symbol comprising a first plurality of samples;

initiate providing, to a second antenna, the first symbol after a first delay period;

initiate providing, to the first antenna, a second symbol comprising a second plurality of samples;

initiate providing, to the second antenna, the second symbol after a second delay period that is different than the first delay period;

initiate providing, to the first antenna, a third symbol comprising a third plurality of samples; and

initiate providing, to the second antenna, the third symbol after a third delay period that is different than the first delay period and the second delay period, each of the symbols comprising a cyclic prefix of one or more samples,

wherein the delay periods that vary according to a defined time varying function are limited based on a number of symbols in a frame, burst period or symbol stream, wherein the defined time varying function is sin(x) where x varies from 0 to N−

1 where N is the number of symbols in a frame, burst period or symbol stream, and wherein time diversity is provided even if a channel is not of itself time selective, and wherein the first symbol, second symbol, and third symbol are modulated according to different carrier frequencies, and a scalar shift is provided to the first delay period, second delay period, and third delay period.