Transmission of signaling in an OFDM-based system

• US 20060045001A1
• Filed: 09/16/2004
• Published: 03/02/2006
• Est. Priority Date: 08/25/2004
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Jalali, Ahmad
• Granted Patent: US 7,852,746 B2
• Time in Patent Office: Days
• US Class Current: 370/208
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0053 Allocation of signaling, i.e. of overhead other than pilot signals
• CPC Class Codes: H04W 72/0453 Resources in frequency domain, e.g. a carrier in FDMA

Abstract

Techniques for efficiently transmitting various types of signaling on the forward and reverse links in an OFDM-based system are described. Instead of specifically allocating subbands to individual signaling channels, signaling data for a signaling channel on a given link is sent as “underlay” to other transmissions that may be sent on the same link. Each wireless terminal is assigned a different PN code. The signaling data for each terminal is spectrally spread over all or a portion of the system bandwidth using the assigned PN code. For the reverse link, a wireless terminal may transmit signaling on all N usable subbands and may transmit traffic data on L subbands assigned for data transmission, which may be a subset of the N usable subbands. For the forward link, a base station may transmit signaling and traffic data for all terminals on the N usable subbands.

Claims

1. An apparatus in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

a signaling modulator operable to spread signaling data over M frequency subbands used for signaling transmission, the M frequency subbands being selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N;

a data modulator operable to map data symbols onto L frequency subbands used for data transmission, where L is one or greater and is less than or equal to N; and

a combiner operable to combine outputs of the signaling modulator and the data modulator.

2. The apparatus of claim 1, wherein the signaling modulator is operable to generate signaling chips for the spread signaling data, wherein the data modulator is operable to perform modulation on the mapped data symbols and generate data chips, and wherein the combiner is operable to combine the signaling chips with the data chips and generate output chips.

3. The apparatus of claim 1, further comprising:

an OFDM modulator operable to perform modulation on an output of the combiner and generate output chips.

4. The apparatus of claim 1, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

5. The apparatus of claim 1, wherein M is less than N and the signaling data is spread over a subset of the N usable frequency subbands.

6. The apparatus of claim 1, wherein the M frequency subbands used for signaling transmission include the L frequency subbands used for data transmission.

7. The apparatus of claim 1, wherein M is equal to L and the M frequency subbands are used for both signaling transmission and data transmission.

8. The apparatus of claim 1, wherein the M frequency subbands are for a shared signaling channel used to send signaling to a plurality of wireless terminals, and wherein the M frequency subbands used for signaling transmission are different from the L frequency subbands used for data transmission.

9. The apparatus of claim 1, wherein the signaling modulator is operable to spread the signaling data with a pseudo-random number (PN) sequence assigned to a wireless terminal.

10. The apparatus of claim 1, wherein the signaling modulator is operable to multiply the signaling data with a pseudo-random number (PN) sequence to generate signaling chips.

11. The apparatus of claim 1, wherein the signaling modulator is operable to multiply the signaling data with a pseudo-random number (PN) sequence to generate spread signaling data and to map the spread signaling data onto the M frequency subbands.

12. The apparatus of claim 11, wherein the signaling modulator is further operable to perform modulation on the mapped spread signaling data to generate signaling chips.

13. The apparatus of claim 2, wherein the combiner is operable to scale the signaling chips with a first gain, scale the data chips with a second gain, and sum the scaled signaling chips with the scaled data chips to generate the output chips.

14. The apparatus of claim 13, wherein the first gain is selected to achieve a target received signal quality for the signaling data at a receiving entity.

15. The apparatus of claim 1, wherein the signaling data is an acknowledgment (ACK) or a negative acknowledgment (NAK) for a data packet received by the apparatus.

16. The apparatus of claim 1, wherein the signaling data is a data rate control (DRC) value indicative of received signal quality at the apparatus.

17. The apparatus of claim 1, wherein the signaling data is a request for an estimate of received signal quality at an entity designated to receive the signaling data.

18. The apparatus of claim 1, wherein the signaling data is a request for air-link resources.

19. The apparatus of claim 1, wherein the signaling data is a power control (PC) command.

20. The apparatus of claim 2, wherein the data modulator is operable to multiplex pilot symbols with the data symbols, to map the multiplexed pilot and data symbols onto the L frequency subbands, and to perform modulation on the mapped pilot and data symbols to generate the data chips.

21. The apparatus of claim 20, wherein the data modulator is operable to time division multiplex the pilot symbols with the data symbols, and wherein the pilot symbols and the data symbols are transmitted in different symbol periods.

22. The apparatus of claim 20, wherein the data modulator is operable to frequency division multiplex the pilot symbols with the data symbols, and wherein the pilot symbols and the data symbols are transmitted on first and second non-overlapping subsets, respectively, of the L frequency subbands.

23. The apparatus of claim 1, further comprising:

a pilot modulator operable to spread pilot symbols over P frequency subbands used for pilot transmission, the P frequency subbands being selected from among the N frequency subbands, where P is greater than one, and wherein the combiner is operable to combine outputs of the data modulator, the pilot modulator, and the signaling modulator.

24. The apparatus of claim 23, wherein the pilot modulator is operable to multiply the pilot symbols with a pseudo-random number (PN) sequence to generate spread pilot symbols and to map the spread pilot symbols onto the P frequency subbands.

25. The apparatus of claim 23, wherein P is equal to L and the L frequency subbands are used for both pilot transmission and data transmission.

26. The apparatus of claim 1, wherein the wireless communication system is an orthogonal frequency division multiple access (OFDMA) system.

27. The apparatus of claim 1, wherein the wireless communication system utilizes frequency hopping, and wherein a different group of L frequency subbands is used for data transmission in each hop period.

28. A wireless terminal comprising the apparatus of claim 1.

29. A base station comprising the apparatus of claim 1.

30. A method of transmitting data and signaling in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

spreading signaling data over M frequency subbands used for signaling transmission, the M frequency subbands being selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N;

mapping data symbols onto L frequency subbands used for data transmission, where L is one or greater and is less than or equal to N; and

processing the spread signaling data on the M frequency subbands and the mapped data symbols on the L frequency subbands to generate output chips.

31. The method of claim 30, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

32. The method of claim 30, wherein the spreading the signaling data comprises multiplying the signaling data with a pseudo-random number (PN) sequence to generate signaling chips.

33. The method of claim 30, wherein the spreading the signaling data comprises

multiplying the signaling data with a pseudo-random number (PN) sequence to generate spread signaling data,

mapping the spread signaling data onto the M frequency subbands, and

performing modulation on the mapped and spread signaling data to generate signaling chips.

34. An apparatus in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

means for spreading signaling data over M frequency subbands used for signaling transmission, the M frequency subbands being selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N;

means for mapping data symbols onto L frequency subbands used for data transmission, where L is one or greater and is less than or equal to N; and

means for processing the spread signaling data on the M frequency subbands and the mapped data symbols on the L frequency subbands to generate output chips.

35. The apparatus of claim 34, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

36. The apparatus of claim 34, wherein the means for spreading the signaling data comprises means for multiplying the signaling data with a pseudo-random number (PN) sequence to generate signaling chips.

37. The method of claim 34, wherein the means for spreading the signaling data comprises

means for multiplying the signaling data with a pseudo-random number (PN) sequence to generate spread signaling data,

means for mapping the spread signaling data onto the M frequency subbands, and

means for performing modulation on the mapped and spread signaling data to generate signaling chips.

38. An apparatus in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

an OFDM demodulator operable to perform demodulation on received samples and provide received symbols; and

a signaling demodulator operable to perform despreading on the received samples or received symbols for M frequency subbands used for signaling transmission and provide detected signaling data, wherein signaling data is spread across the M frequency subbands prior to transmission, and wherein the M frequency subbands are selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N.

39. The apparatus of claim 38, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

40. The apparatus of claim 38, wherein the M frequency subbands used for signaling transmission include the L frequency subbands used for data transmission.

41. The apparatus of claim 38, wherein the signaling demodulator is operable to multiply the received samples with a pseudo-random number (PN) sequence and to accumulate result of the multiply to obtain the detected signaling data.

42. The apparatus of claim 38, wherein the signaling demodulator is operable to multiply the received symbols for the M frequency subbands with a pseudo-random number (PN) sequence and to accumulate result of the multiply to obtain the detected signaling data.

43. The apparatus of claim 38, further comprising:

a data demodulator operable to perform data detection on received symbols for L frequency subbands used for data transmission and provide detected data symbols, where L is one or greater and is less than or equal to N.

44. The apparatus of claim 43, wherein the data demodulator is operable to derive a channel estimate for the L frequency subbands and to perform data detection on the received symbols for the L frequency subbands with the channel estimate.

45. The apparatus of claim 43, wherein the data demodulator is operable to despread received symbols for P frequency subbands used for pilot transmission, to derive a channel estimate for the L frequency subbands based on despread symbols for the P frequency subbands, and to perform data detection on the received symbols for the L frequency subbands with the channel estimate.

46. The apparatus of claim 43, wherein the data demodulator is further operable to derive an interference estimate for the detected signaling data, to subtract the interference estimate from the received symbols for the L frequency subbands to obtain interference-canceled symbols, and to perform data detection on the interference-canceled symbols to obtain the detected data symbols.

47. The apparatus of claim 43, wherein the data demodulator is further operable to derive an interference estimate for pilot received by the apparatus, to subtract the interference estimate from the received symbols for the L frequency subbands to obtain pilot-canceled symbols, and to perform data detection on the pilot-canceled symbols to obtain the detected data symbols.

48. A method of receiving data and signaling in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

performing demodulation on received samples to obtain received symbols; and

despreading the received samples or received symbols for M frequency subbands used for signaling transmission to obtain detected signaling data, wherein signaling data is spread across the M frequency subbands prior to transmission, and wherein the M frequency subbands are selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N.

49. The method of claim 48, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

50. The method of claim 48, wherein the despreading comprises

multiplying the received samples with a pseudo-random number (PN) sequence, and

accumulating result of the multiply to obtain the detected signaling data.

51. The method of claim 48, wherein the despreading comprises

multiplying the received symbols for the M frequency subbands with a pseudo-random number (PN) sequence, and

accumulating result of the multiply to obtain the detected signaling data.

52. The method of claim 48, further comprising:

performing data detection on received symbols for L frequency subbands used for data transmission to obtain detected data symbols, where L is one or greater and is less than or equal to N.

53. An apparatus in a wireless communication system utilizing orthogonal frequency division multiplexing (OFDM), comprising:

means for performing demodulation on received samples to obtain received symbols; and

means for despreading the received samples or received symbols for M frequency subbands used for signaling transmission to obtain detected signaling data, wherein signaling data is spread across the M frequency subbands prior to transmission, and wherein the M frequency subbands are selected from among N frequency subbands usable for transmission, where M and N are each greater than one and M is less than or equal to N.

54. The apparatus of claim 53, wherein M is equal to N and the signaling data is spread over all N usable frequency subbands.

55. The apparatus of claim 53, wherein the means for despreading comprises

means for multiplying the received samples with a pseudo-random number (PN) sequence, and

means for accumulating result of the multiply to obtain the detected signaling data.

56. The apparatus of claim 53, wherein the means for despreading comprises

means for multiplying the received symbols for the M frequency subbands with a pseudo-random number (PN) sequence, and

means for accumulating result of the multiply to obtain the detected signaling data.

57. The apparatus of claim 53, further comprising:

means for performing data detection on received symbols for L frequency subbands used for data transmission to obtain detected data symbols, where L is one or greater and is less than or equal to N.