Method and system for multirate multiuser modulation

• US 20020118765A1
• Filed: 09/24/2001
• Published: 08/29/2002
• Est. Priority Date: 12/29/2000
• Status: Active Grant

• Current Assignee: Google Technology Holdings LLC (Alphabet Inc.)
• Original Assignee: Motorola, Inc. (Motorola Solutions, Inc.)
• Inventors: Nangia, Vijay, Ramasubramanian, Karthik, Baum, Kevin Lynn
• Granted Patent: US 7,139,237 B2
• Time in Patent Office: Days
• US Class Current: 375/260
• CPC Class Codes: H04B 2201/70703 using multiple or variable rates
• CPC Class Codes: H04J 13/004 Orthogonal
• CPC Class Codes: H04J 13/18 Allocation of orthogonal codes
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601

Abstract

A multi-rate interleaved frequency division multiple access (IFDMA) modulation scheme permits users to transmit at different data rates or to vary their data rates while providing frequency diversity and preserving low peak-to-average power ratios and orthogonality between users at different data rates. The modulation scheme allows user-specific data block and repetition sizes, as well as user-specific modulation codes. Code assignment rules are provided for maintaining orthogonality between users having different data rates. Block and phase ramp modulation codes can be used. Asynchronous transmissions by users are supported by ensuring that the length of the cyclic extension is sufficiently long to tolerate worst case relative signal arrival delays between users and the channel pulse response duration over the communication medium. The modulation scheme can be employed in wireless communication systems, such as cellular or paging systems.

Claims

1. A method of modulating a signal, comprising:

providing an interleaved frequency division multiple access (IFDMA) modulation scheme for transferring information using a communication system;

providing assignment rules for defining a plurality of data rates; and

modulating the signal using the IFDMA modulation scheme and at least one of the data rates.

2. The method of claim 1, further comprising, varying the data rate of the modulated signal based on the channel conditions of a channel used by the communication system.

3. The method of claim 1, further comprising, selecting a modulation code for the signal.

4. The method of claim 3, wherein the modulation code is one of a block modulation code and a phase ramp modulation code.

5. The method of claim 4, wherein the block modulation code is based on an L-dimensional discrete Fourier transform (DFT) matrix defining a channelization code.

6. The method of claim 3, wherein the modulation code is selected based on a code tree.

7. The method of claim 1, wherein the data rates are selected using a code tree.

8. An apparatus, comprising, a transmitter modulating a signal at a selected one of a plurality of data rates using an interleaved frequency division multiple access (IFDMA) modulation scheme.

9. The apparatus of claim 8, wherein the transmitter includes, means for applying a user-specific symbol block repetition value in the IFDMA modulation scheme.

10. The apparatus of claim 8, wherein the transmitter includes, means for applying a user-specific modulation code in the IFDMA modulation scheme.

11. The apparatus of claim 8, wherein the transmitter includes a pulse-shaping filter.

12. The apparatus of claim 8, wherein the transmitter includes means for adding a cyclic extension to the signal.

13. The apparatus of claim 12, wherein the cyclic extension has a length greater than the sum of a relative signal arrival delay between a plurality of users and the channel pulse response duration.

14. The apparatus of claim 8, wherein the transmitter includes, a serial-to-parallel converter for converting the signal to a multi-symbol vector representation.

15. The apparatus of claim 8, wherein the transmitter includes, a parallel-to-serial converter for converting the modulated signal to a serial representation prior to transmission.

17. The communication system of claim 16, wherein the channel is a radio frequency (RF) communication channel.

18. The communication system of claim 16, wherein the multi-rate IFDMA modulation scheme provides predetermined assignment rules for selecting a plurality of data rates.

19. The communication system of claim 16, wherein the multi-rate IFDMA modulation scheme provides predetermined assignment rules for specifying a modulation code.

20. The communication system of claim 19, wherein the modulation code is selected from a block modulation code and a phase ramp modulation code.

21. The communication system of claim 19, wherein the modulation code is selected to maintain orthogonality between information modulated at different data rates.

16. A communication system, comprising:

a transmitter modulating a signal using a multi-rate interleaved frequency division multiple access (IFDMA) modulation scheme; and

a receiver, operatively coupled to the transmitter over a channel, for demodulating the signal using a multi-rate IFDMA demodulation scheme.

22. A method of demodulating a signal, comprising:

equalizing the signal;

correlating the equalized signal with a predetermined modulation code;

combining block repetitions of the correlated signal; and

detecting one or more symbols based on the combined block repetitions.

23. The method of claim 22, further comprising, filtering the signal.

24. The method of claim 22, further comprising, performing an A/D conversion on the signal.

25. The method of claim 22, further comprising, removing a cyclic extension.

26. The method of claim 22, wherein the step of equalizing includes a step selected from the group consisting of:

performing a frequency domain equalization, performing a time-domain equalization, performing a decision feedback equalization, performing an iterative equalization, performing an ISI cancellation, performing a turbo equalization, and performing a maximum likelihood sequence estimation.

27. The method of claim 22, wherein the modulation code is selected from a group consisting of a block modulation code and a phase ramp modulation code.

29. The method of claim 28, further comprising, filtering the signal.

30. The method of claim 28, further comprising, performing an A/D conversion on the signal.

31. The method of claim 28, further comprising, removing a cyclic extension.

32. The method of claim 28, wherein the modulation code is selected from the group consisting of a block modulation code and a phase ramp modulation code.

33. The method of claim 28, further comprising, equalizing the combined block repetitions.

34. The method of claim 33, wherein the step of equalizing includes a step selected from the group consisting of:

performing a frequency domain equalization, performing a time-domain equalization, performing a decision feedback equalization, performing an iterative equalization, performing an ISI cancellation, performing a turbo equalization, and performing a maximum likelihood sequence estimation.

36. The receiver of claim 35, further comprising, an intermediate frequency (IF) filter, operatively coupled to the equalizer, for filtering the signal prior to it being equalized.

37. The receiver of claim 35, further comprising, an A/D converter for performing an A/D conversion on the signal.

38. The receiver of claim 35, further comprising, means for removing a cyclic extension.

39. The receiver of claim 35, wherein the equalizer performs an equalization selected from the group consisting of:

a frequency domain equalization, time-domain equalization, decision feedback equalization, iterative equalization, ISI cancellation, turbo equalization, and maximum likelihood sequence estimation.

40. The receiver of claim 35, wherein the modulation code is selected from the group consisting of a block modulation code and a phase ramp modulation code.

41. The receiver of claim 35, further comprising, a detector, responsive to the output of the block combiner, for detecting one or more symbols based on the combined block repetitions.

28. A method of demodulating a signal, comprising:

correlating the signal with a predetermined modulation code;

combining block repetitions of the correlated signal; and

detecting one or more symbols based on the combined block repetitions.

35. A receiver, comprising:

an equalizer for equalizing an input signal;

a correlator, operatively couple to the equalizer, for correlating the equalized signal using a predetermined modulation code; and

a block combiner, operatively coupled to the correlator, for combining block repetitions of the correlated signal.

42. A receiver, comprising:

a correlator for correlating a signal using a predetermined modulation code;

a block combiner, operatively coupled to the correlator, for combining block repetitions of the correlated signal; and

an equalizer, operatively coupled to the block combiner, for equalizing the output of the block combiner.

43. The receiver of claim 42, further comprising, an intermediate frequency (IF) filter for filtering the signal prior to it being correlated.

44. The receiver of claim 42, further comprising, an A/D converter for performing an A/D conversion on the signal.

45. The receiver of claim 42, further comprising, means for removing a cyclic extension.

46. The receiver of claim 42, wherein the equalizer performs an equalization selected from the group consisting of:

a frequency domain equalization, time-domain equalization, decision feedback equalization, iterative equalization, ISI cancellation, turbo equalization, and maximum likelihood sequence estimation.

47. The receiver of claim 42, wherein the modulation code is selected from a block modulation code and a phase ramp modulation code.

48. The receiver of claim 42, further comprising, a detector, responsive to the equalized signal, for detecting one or more symbols based on the equalized combined block repetitions.