OFDM communication system with multiple OFDM symbol sizes

• US 20040081131A1
• Filed: 02/25/2003
• Published: 04/29/2004
• Est. Priority Date: 10/25/2002
• Status: Abandoned Application

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Howard, Steven J., Ketchum, John W., Walton, Jay Rod, Wallace, Mark
• Application Number:
  US10/375,162
• Publication Number:
  US 20040081131A1
• Time in Patent Office: Days
• US Class Current: 370/344
• CPC Class Codes: H04B 7/0421 utilizing implicit feedback, e.g. steered pilot signals
• CPC Class Codes: H04B 7/043 using best eigenmode, e.g. beam forming or beam steering
• CPC Class Codes: H04B 7/0669 using different channel coding between antennas space-time coding H04L1/0618
• CPC Class Codes: H04B 7/0697 using spatial multiplexing
• CPC Class Codes: H04B 7/0854 using error minimizing algorithms, e.g. minimum mean squared error [MMSE], "cross-correlation" or matrix inversion
• CPC Class Codes: H04L 1/0017 where the mode-switching is based on Quality of Service requirement
• CPC Class Codes: H04L 25/0232 by interpolation between sounding signals
• CPC Class Codes: H04L 25/0248 Eigen-space methods
• CPC Class Codes: H04L 27/2602 Signal structure
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0023 Time-frequency-space
• CPC Class Codes: H04L 5/0028 Variable division signaling therefor H04L5/0092
• CPC Class Codes: H04L 5/0037 Inter-user or inter-terminal allocation
• CPC Class Codes: H04W 28/20 Negotiating bandwidth
• CPC Class Codes: H04W 52/50 at the moment of starting communication in a multiple access environment
• CPC Class Codes: H04W 72/04 Wireless resource allocation

Abstract

Techniques to use OFDM symbols of different sizes to achieve greater efficiency for OFDM systems. The system traffic may be arranged into different categories (e.g., control data, user data, and pilot data). For each category, one or more OFDM symbols of the proper sizes may be selected for use based on the expected payload size for the traffic in that category. For example, control data may be transmitted using OFDM symbols of a first size, user data may be transmitted using OFDM symbols of the first size and a second size, and pilot data may be transmitted using OFDM symbols of a third size or the first size. In one exemplary design, a small OFDM symbol is utilized for pilot and for transport channels used to send control data, and a large OFDM symbol and the small OFDM symbol are utilized for transport channels used to send user data.

Claims

1. A method of transmitting data in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

transmitting a first block of data in a first OFDM symbol of a first size; and

transmitting a second block of data in a second OFDM symbol of a second size that is different from the first size.

2. The method of claim 1, wherein the first block of data comprises control data and the second block of data comprises user data.

3. The method of claim 2, wherein the first size is selected based on an expected payload size for the control data and the second size is selected based on an expected payload size for the user data.

4. The method of claim 1, wherein the first and second blocks of data are for a data packet.

5. The method of claim 1, wherein the first block of data is intended for multiple receivers and the second block of data is intended for a single receiver.

6. The method of claim 1, further comprising:

transmitting a pilot in a third OFDM symbol.

7. The method of claim 6, wherein the pilot is a steered reference.

8. The method of claim 1, wherein each pair of modulation symbols for the second OFDM symbol is concurrently transmitted on a pair of subbands from two antennas.

9. The method of claim 1, wherein cyclic prefixes for the first and second OFDM symbols have the same length.

10. The method of claim 1, wherein cyclic prefixes for the first and second OFDM symbols have different lengths.

11. The method of claim 1, wherein the second block of data is coded to obtain an error detection value that is transmitted in the second OFDM symbol.

12. The method of claim 1, wherein the first and second blocks of data are interleaved with the same interleaving scheme.

13. The method of claim 1, wherein the first and second sizes are related by a power of two.

14. An apparatus in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

means for transmitting a first block of data in a first OFDM symbol of a first size; and

means for transmitting a second block of data in a second OFDM symbol of a second size that is different from the first size.

15. The apparatus of claim 14, further comprising:

means for transmitting a pilot in a third OFDM symbol of the first size.

16. A transmitter unit in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

a transmit (TX) data processor operative to process a first block of data to obtain a first set of modulation symbols and to process a second block of data to obtain a second set of modulation symbols; and

a modulator operative to process the first set of modulation symbols to obtain a first OFDM symbol of a first size and to process the second set of modulation symbols to obtain a second OFDM symbol of a second size that is different from the first size.

17. The transmitter unit of claim 16, wherein the modulator is further operative to process a third set of modulation symbols for a pilot to obtain a third OFDM symbol for the pilot.

18. A method of transmitting data in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

transmitting control data in a first time segment with a first OFDM symbol of a first size; and

transmitting user data in a second time segment with a second OFDM symbol of a second size that is different from the first size.

19. The method of claim 18, further comprising:

transmitting user data in the second time segment with a third OFDM symbol of a third size that is different from the second size.

20. The method of claim 18, further comprising:

transmitting a pilot in a third time segment with a third OFDM symbol.

21. The method of claim 18, wherein the first and second sizes are fixed.

22. The method of claim 18, wherein the first and second sizes are configurable.

23. A method of receiving data in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

receiving a first OFDM symbol of a first size for a first block of data; and

receiving a second OFDM symbol of a second size for a second block of data, the second size being different from the first size.

24. The method of claim 23, wherein the first block of data comprises control data and the second block of data comprises user data.

25. The method of claim 23, wherein the first and second blocks of data are for a data packet.

26. The method of claim 23, further comprising:

receiving a third OFDM symbol for a pilot.

27. The method of claim 26, further comprising:

processing the third OFDM symbol to obtain a channel estimate for each of a plurality of subbands.

28. The method of claim 27, further comprising:

interpolating channel estimates for the plurality of subbands to obtain a channel estimate for an additional subband not among the plurality of subbands.

29. An apparatus in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

means for receiving a first OFDM symbol of a first size for a first block of data; and

means for receiving a second OFDM symbol of a second size for a second block of data, the second size being different from the first size.

30. The apparatus of claim 29, further comprising:

means for receiving a third OFDM symbol for a pilot; and

means for processing the third OFDM symbol to obtain a channel estimate for each of a plurality of subbands.

31. The apparatus of claim 30, comprising:

means for interpolating channel estimates for the plurality of subbands to obtain a channel estimate for an additional subband not among the plurality of subbands.

32. A receiver unit in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

a demodulator operative to process a first OFDM symbol of a first size to obtain a first set of received modulation symbols and to process a second OFDM symbol of a second size to obtain a second set of received modulation symbols, wherein the second size is different from the first size; and

a receive (RX) data processor operative to process the first set of received modulation symbols to obtain a first block of data and to process the second set of received modulation symbols to obtain a second block of data.

33. The receiver unit of claim 32, wherein the demodulator is further operative to process a third OFDM symbol for a pilot to provide a channel estimate for each of a plurality of subbands.

34. The receiver unit of claim 33, further comprising:

a controller operative to interpolate channel estimates for the plurality of subbands to obtain a channel estimate for an additional subband not among the plurality of subbands.

35. A method of processing a pilot in a multiple-input multiple-output (MIO) orthogonal frequency division multiplexing (OFDM) communication system, comprising:

receiving a first set of OFDM symbols from a set of antennas for the pilot;

processing the first set of OFDM symbols to obtain a channel response matrix for each of a plurality of subbands; and

decomposing the channel response matrix for each of the plurality of subbands to obtain a unitary matrix of eigenvectors for the channel response matrix, wherein the decomposition is performed in a manner to avoid arbitrary phase rotations from subband to subband.

36. The method of claim 35, wherein the arbitrary phase rotations from subband to subband are avoided by constraining first element in each column of the unitary matrix to be a non-negative value.

37. The method of claim 36, further comprising:

generating a steered reference based on a particular column of the unitary matrix for each of the plurality of subbands; and

transmitting a second set of OFDM symbols from the set of antennas for the steered reference.

38. A method of processing a steered reference in a multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) communication system, comprising:

receiving a set of OFDM symbols from a set of antennas for the steered reference;

processing the set of OFDM symbols to obtain a steering vector for each of a plurality of subbands; and

interpolating steering vectors for the plurality of subbands to obtain a steering vector for an additional subband not among the plurality of subbands.

39. A method of transmitting a data unit having a data unit size in an orthogonal frequency division multiplexing (OFDM) communication system, the method comprising:

selecting a first OFDM symbol size from a set of OFDM symbol sizes, wherein the set of OFDM symbol sizes comprises a large OFDM symbol size and a small OFDM symbol size that is smaller than the large OFDM symbol size; and

transmitting a first portion of the data unit in an OFDM symbol having the first OFDM symbol size.

40. The method of claim 39 wherein the selecting a first OFDM symbol size is based on the data unit size.

41. The method of claim 39 wherein the data unit has a data unit type, and wherein the selecting a first OFDM symbol size is based on the data unit type.

42. The method of claim 39 further comprising:

selecting a second OFDM symbol size from the set of OFDM symbol sizes; and

transmitting a second portion of the data unit in a second OFDM symbol having the second OFDM symbol size.

43. The method of claim 42, wherein the first OFDM symbol size is equal to the second OFDM symbol size.

44. The method of claim 42, wherein the first OFDM symbol size is larger than the second OFDM symbol size.

45. An apparatus in an orthogonal frequency division multiplexing (OFDM) communication system, comprising

means for selecting a first OFDM symbol size from a set of OFDM symbol sizes, wherein the set of OFDM symbol sizes comprises a large OFDM symbol size and a small OFDM symbol size that is smaller than the large OFDM symbol size;

and

means for transmitting a first portion of a data unit in an OFDM symbol having the first OFDM symbol size.

46. The apparatus of claim 45, further comprising:

means for selecting a second OFDM symbol size from the set of OFDM symbol sizes; and

means for transmitting a second portion of the data unit in a second OFDM symbol having the second OFDM symbol size.

47. The apparatus of claim 45, wherein the first OFDM symbol size is selected based on a data unit size of the data unit.

48. The apparatus of claim 45, wherein the first OFDM symbol size is selected based on a data unit type of the data unit.

49. A transmitter unit in an orthogonal frequency division multiplexing (OFDM) communication system, comprising:

a controller operative to select a first OFDM symbol size from a set of OFDM symbol sizes, wherein the set of OFDM symbol sizes comprises a large OFDM symbol size and a small OFDM symbol size that is smaller than the large OFDM symbol size; and

a modulator operative to process a first portion of a data unit to obtain an OFDM symbol having the first OFDM symbol size.

50. The transmitter of claim 49, wherein the controller is further operative to select a second OFDM symbol size from the set of OFDM symbol sizes, and wherein the modulator is further operative to process a second portion of the data unit to obtain a second OFDM symbol having the second OFDM symbol size.