MULTIPLE-ACCESS HYBRID OFDM-CDMA SYSTEM

• US 20110317671A1
• Filed: 09/08/2011
• Published: 12/29/2011
• Est. Priority Date: 10/18/2001
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Walton, Jay R., Ketchum, John W., Howard, Steven J., Wallace, Mark
• Granted Patent: US 8,948,705 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04B 1/692 Hybrid techniques using combinations of two or more spread spectrum techniques
• CPC Class Codes: H04L 25/0228 with direct estimation from sounding signals
• CPC Class Codes: H04L 27/0008 arrangements for allowing a transmitter or receiver to use more than one type of modulation negotiating modulation type for two-way transmission paths H04L5/1453
• CPC Class Codes: H04L 27/2607 Cyclic extensions
• CPC Class Codes: H04L 27/2613 Structure of the reference signals
• CPC Class Codes: H04L 27/2647 Arrangements specific to the receiver only equalisation H04L27/01
• CPC Class Codes: H04L 27/2655 Synchronisation arrangements
• CPC Class Codes: H04L 5/0021 in which codes are applied as a frequency-domain sequences, e.g. MC-CDMA
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04L 5/026 using code division
• CPC Class Codes: H04W 52/12 Outer and inner loops
• CPC Class Codes: H04W 52/286 during data packet transmission, e.g. high speed packet access [HSPA]

Abstract

In one aspect of a multiple-access OFDM-CDMA system, data spreading is performed in the frequency domain by spreading each data stream with a respective spreading code selected from a set of available spreading codes. To support multiple access, system resources may be allocated and de-allocated to users (e.g., spreading codes may be assigned to users as needed, and transmit power may be allocated to users). Variable rate data for each user may be supported via a combination of spreading adjustment and transmit power scaling. Interference control techniques are also provided to improve system performance via power control of the downlink and/or uplink transmissions to achieve the desired level of performance while minimizing interference. A pilot may be transmitted by each transmitter unit to assist the receiver units perform acquisition, timing synchronization, carrier recovery, handoff, channel estimation, coherent data demodulation, and so on.

Claims

1. A method for wireless communication, comprising:

spreading a modulation symbol with a spreading sequence to obtain a plurality of spread symbols;

mapping the plurality of spread symbols to a plurality of subcarriers to obtain a plurality of mapped symbols;

transforming the plurality of mapped symbols from frequency domain to time domain to obtain a plurality of time-domain samples; and

sending the plurality of time-domain samples.

2. The method of claim 1, wherein the spreading the modulation symbol comprises multiplying the modulation symbol with a plurality of symbols of the spreading sequence to obtain the plurality of spread symbols, one spread symbol for each of the plurality of symbols of the spreading sequence.

3. The method of claim 1, wherein the mapping the plurality of spread symbols comprises mapping the plurality of spread symbols to the plurality of subcarriers corresponding to a subset of all subcarriers available for transmission.

4. The method of claim 1, wherein the transforming the plurality of mapped symbols comprises transforming the plurality of mapped symbols based on an inverse fast Fourier transform (IFFT) to obtain the plurality of time-domain samples.

5. The method of claim 1, further comprising:

appending a cyclic prefix to the plurality of time-domain samples prior to transmission.

6. The method of claim 1, further comprising:

time division multiplexing the plurality of time-domain samples and pilot.

7. The method of claim 1, further comprising:

scaling the plurality of time-domain samples, or the plurality of spread symbols, or the modulation symbol based on a gain to obtain a target transmit power level.

8. The method of claim 7, further comprising:

receiving a power control command; and

adjusting the gain based on the power control command.

9. The method of claim 1, wherein the spreading sequence is assigned to a terminal.

10. The method of claim 1, wherein the spreading sequence comprises a plurality of symbols of complex values.

11. An apparatus for wireless communication, comprising:

means for spreading a modulation symbol with a spreading sequence to obtain a plurality of spread symbols;

means for mapping the plurality of spread symbols to a plurality of subcarriers to obtain a plurality of mapped symbols;

means for transforming the plurality of mapped symbols from frequency domain to time domain to obtain a plurality of time-domain samples; and

means for sending the plurality of time-domain samples.

12. The apparatus of claim 11, wherein the means for spreading the modulation symbol comprises means for multiplying the modulation symbol with a plurality of symbols of the spreading sequence to obtain the plurality of spread symbols, one spread symbol for each of the plurality of symbols of the spreading sequence.

13. The apparatus of claim 11, wherein the means for mapping the plurality of spread symbols comprises means for mapping the plurality of spread symbols to the plurality of subcarriers corresponding to a subset of all subcarriers available for transmission.

14. The apparatus of claim 11, wherein the means for transforming the plurality of mapped symbols comprises means for transforming the plurality of mapped symbols based on an inverse fast Fourier transform (IFFT) to obtain the plurality of time-domain samples.

15. The apparatus of claim 11, further comprising:

means for appending a cyclic prefix to the plurality of time-domain samples prior to transmission.

16. The apparatus of claim 11, further comprising:

means for time division multiplexing the plurality of time-domain samples and pilot.

17. An apparatus for wireless communication, comprising:

at least one processor configured to spread a modulation symbol with a spreading sequence to obtain a plurality of spread symbols, to map the plurality of spread symbols to a plurality of subcarriers to obtain a plurality of mapped symbols, to transform the plurality of mapped symbols from frequency domain to time domain to obtain a plurality of time-domain samples, and to send the plurality of time-domain samples.

18. The apparatus of claim 17, wherein the at least one processor is configured to multiply the modulation symbol with a plurality of symbols of the spreading sequence to obtain the plurality of spread symbols, one spread symbol for each of the plurality of symbols of the spreading sequence.

19. The apparatus of claim 17, wherein the at least one processor is configured to map the plurality of spread symbols to the plurality of subcarriers corresponding to a subset of all subcarriers available for transmission.

20. The apparatus of claim 17, wherein the at least one processor is configured to transform the plurality of mapped symbols based on an inverse fast Fourier transform (IFFT) to obtain the plurality of time-domain samples.

21. The apparatus of claim 17, wherein the at least one processor is configured to append a cyclic prefix to the plurality of time-domain samples prior to transmission.

22. The apparatus of claim 17, wherein the at least one processor is configured to time division multiplex the plurality of time-domain samples and pilot.

23. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code for causing at least one processor to spread a modulation symbol with a spreading sequence to obtain a plurality of spread symbols,

code for causing the at least one processor to map the plurality of spread symbols to a plurality of subcarriers to obtain a plurality of mapped symbols,

code for causing the at least one processor to transform the plurality of mapped symbols from frequency domain to time domain to obtain a plurality of time-domain samples, and

code for causing the at least one processor to send the plurality of time-domain samples.

24. A method for wireless communication, comprising:

transforming a plurality of time-domain samples from time domain to frequency domain to obtain received symbols for subcarriers available for transmission;

obtaining a plurality of received symbols for a plurality of subcarriers corresponding to a subset of all subcarriers available for transmission; and

despreading the plurality of received symbols based on a spreading sequence to obtain a despread symbol.

25. The method of claim 24, further comprising:

removing a cyclic prefix prior to transforming from time domain to frequency domain.

26. The method of claim 24, wherein the transforming the plurality of time-domain samples comprises transforming the plurality of time-domain samples based on a fast Fourier transform (FFT) to obtain the received symbols for the subcarriers available for transmission.

27. The method of claim 24, wherein the despreading the plurality of received symbols comprises correlating the plurality of received symbols with a plurality of symbols determined based on the spreading sequence to obtain the despread symbol.

28. The method of claim 24, further comprising:

time division demultiplexing the plurality of time-domain samples and pilot.

29. The method of claim 28, further comprising:

determining a channel estimate based on the pilot; and

despreading the plurality of received symbols based further on the channel estimate.

30. The method of claim 24, wherein the spreading sequence is assigned to a terminal.

31. The method of claim 24, wherein the spreading sequence comprises a plurality of symbols of complex values.

32. An apparatus for wireless communication, comprising:

means for transforming a plurality of time-domain samples from time domain to frequency domain to obtain received symbols for subcarriers available for transmission;

means for obtaining a plurality of received symbols for a plurality of subcarriers corresponding to a subset of all subcarriers available for transmission; and

means for despreading the plurality of received symbols based on a spreading sequence to obtain a despread symbol.

33. The apparatus of claim 32, further comprising:

means for removing a cyclic prefix prior to transforming from time domain to frequency domain.

34. The apparatus of claim 32, wherein the means for transforming the plurality of time-domain samples comprises means for transforming the plurality of time-domain samples based on a fast Fourier transform (FFT) to obtain the received symbols for the subcarriers available for transmission.

35. The apparatus of claim 32, wherein the means for despreading the plurality of received symbols comprises means for correlating the plurality of received symbols with a plurality of symbols determined based on the spreading sequence to obtain the despread symbol.

36. The apparatus of claim 32, further comprising:

means for time division demultiplexing the plurality of time-domain samples and pilot.

37. An apparatus for wireless communication, comprising:

at least one processor configured to transform a plurality of time-domain samples from time domain to frequency domain to obtain received symbols for subcarriers available for transmission, to obtain a plurality of received symbols from a plurality of subcarriers corresponding to a subset of all subcarriers available for transmission, and to despread the plurality of received symbols based on a spreading sequence to obtain a despread symbol.

38. The apparatus of claim 37, wherein the at least one processor is configured to remove a cyclic prefix prior to performing the transform from time domain to frequency domain.

39. The apparatus of claim 37, wherein the at least one processor is configured to transform the plurality of time-domain samples based on a fast Fourier transform (FFT) to obtain the received symbols for the subcarriers available for transmission.

40. The apparatus of claim 37, wherein the at least one processor is configured to correlate the plurality of received symbols with a plurality of symbols determined based on the spreading sequence to obtain the despread symbol.

41. The apparatus of claim 37, wherein the at least one processor is configured to time division demultiplex the plurality of time-domain samples and pilot.

42. A computer program product, comprising:

a non-transitory computer-readable medium comprising;

code for causing at least one processor to transform a plurality of time-domain samples from time domain to frequency domain to obtain received symbols for subcarriers available for transmission,

code for causing the at least one processor to obtain a plurality of received symbols for a plurality of subcarriers corresponding to a subset of all subcarriers available for transmission, and

code for causing the at least one processor to despread the plurality of received symbols based on a spreading sequence to obtain a despread symbol.