Communication system using OFDM for one direction and DSSS for another direction

• US 8,040,855 B2
• Filed: 05/31/2007
• Issued: 10/18/2011
• Est. Priority Date: 03/09/2001
• Status: Expired due to Fees

• Current Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Original Assignee: Adaptix, Inc. (Acacia Research Corporation)
• Inventors: Zhang, Wenzhong, Li, Xiaodong, Liu, Hui
• Primary Examiner(s): Wu; Daniel
• Assistant Examiner(s): OTT, FREDERICK R
• Application Number:
  US11/756,316
• Publication Number:
  US 20070223406A1
• Time in Patent Office: 1,601 Days
• Field of Search: 370/335, 370/455, 370/355, 375/140, 375/131
• US Class Current: 370/335
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04L 27/2601 Multicarrier modulation systems
• CPC Class Codes: H04L 5/023 Multiplexing of multicarrier modulation signals multicarrier modulation H04L27/2601
• CPC Class Codes: H04L 5/14 Two-way operation using the same type of signal, i.e. duplex
• CPC Class Codes: H04L 5/143 for modulated signals H04L5/1469 takes precedence
• CPC Class Codes: H04W 16/10 Dynamic resource partitioning
• CPC Class Codes: H04W 52/08 Closed loop power control
• CPC Class Codes: H04W 52/10 Open loop power control
• CPC Class Codes: H04W 72/54 based on quality criteria

Abstract

A method and apparatus for wireless communication are described. In one embodiment, a method for communicating with a subscriber comprises transmitting orthogonal frequency domain multiplexing (OFDM) signals to the subscriber, and receiving direct-sequence spread spectrum (DSSS) signals from the subscriber.

Claims

1. A method for communicating with a subscriber, the method comprising:

transmitting orthogonal frequency division multiplexing (OFDM) signals to the subscriber, wherein receipt of the OFDM signals by the subscriber is associated with a direct-sequence spread spectrum (DSSS) signal being generated by the subscriber such that use of the DSSS signal enables communication via the OFDM signals;

wherein transmitting comprises;

transmitting the OFDM signals in a first frequency range; and

where generating DSSS signals comprises;

generating DSSS signals in a second frequency range.

2. The method of claim 1, wherein the first frequency range and the second frequency range do not overlap.

3. A method for communicating with a plurality of subscribers, the method comprising:

transmitting orthogonal frequency division multiplexing (OFDM) signals to the plurality of subscribers, wherein receipt of the OFDM signals by the subscribers is associated with a direct-sequence spread spectrum (DSSS) signal being generated by the subscribers such that use of the DSSS signal enables communication via the OFDM signals.

4. The communication method of claim 3 wherein the transmitting comprises:

allocating a portion of OFDM subcarriers to at least a subset of said plurality of subscribers; and

simultaneously transmitting OFDM signals to the at least a subset of said plurality of subscribers according to the subcarrier allocation.

5. The method of claim 3, where transmitting OFDM signals comprises transmitting the OFDM signals in a first frequency range and where generating DSSS signals comprises generating the DSSS signals in a second frequency range.

6. The method of claim 5, wherein the first frequency range and the second frequency range do not overlap.

7. A communication method, the method comprising:

simultaneously receiving, at one or more subscribers, orthogonal frequency division multiplexing (OFDM) signals, where at least one subcarrier is allocated to one or more subscribers; and

transmitting, from the one or more subscribers, direct-sequence spread spectrum (DSSS) signals in association with the receiving, wherein the association between the receiving and the transmitting the DSSS signals comprises communication via the OFDM signals being enabled at a subscriber station of the one or more subscriber station using a DSSS signal of the DSSS signals transmitted by the subscriber station.

8. A communication method, the method comprising:

transmitting orthogonal frequency division multiple access (OFDMA) signals to at least one subscriber; and

receiving at a base station direct-sequence spread spectrum (DSSS) signals from the at least one subscriber;

wherein a communication link provided by the OFDMA signals transmitted by the base station and a communication link provided by the DSSS signals received from the at least one subscriber each comprise a link segment of a bi-directional communication link.

9. The method of claim 8 wherein said bi-directional communication link is asymmetrical.

10. A communication method, the method comprising:

receiving orthogonal frequency division multiple access (OFDMA) signals at a subscriber station; and

transmitting, from the subscriber station, direct-sequence spread spectrum (DSSS) signals to a base station;

wherein a communication link provided by the DSSS signals transmitted to the base station and a communication link provided by the OFDMA signals received at the subscriber station each comprise a link segment of a bi-directional communication link.

11. The method of claim 10 wherein said bi-directional communication link is asymmetrical.

12. A method comprising:

receiving orthogonal frequency division multiplexing (OFDM) signals; and

transmitting direct-sequence spread spectrum (DSSS) signals to a base station in association with the receiving OFDM signals such that use of the DSSS signals enable communication via the OFDM signals.

13. The method of claim 12 further comprising:

demultiplexing multiple sub-carriers of the received OFDM signals;

identifying fewer than all of the demultiplexed sub-carriers that are associated with a subscriber, and

outputting user data associated with the identified sub-carriers.

14. The method of claim 12, wherein the transmitting of the DSSS signals comprises transmitting code division multiple access (CDMA) signals.

15. The method of claim 14, wherein the transmitting of CDMA signals comprises transmitting W-CDMA signals.

16. The method of claim 12, wherein the transmitting of the DSSS signals comprises transmitting a signal including a signal quality metric of the received OFDM signals.

17. The method of claim 12, comprising determining a quality metric for the received OFDM signals.

18. The method of claim 17, wherein the determining of the quality metric comprises determining a signal to noise ratio of the received OFDM signals.

19. The method of claim 12, wherein the receiving of the OFDM signals comprises receiving one or more pilot signals.

20. The method of claim 12, wherein the receiving of the OFDM signals comprises receiving OFDM signals in a first frequency range and wherein the transmitting of the DSSS signal comprises transmitting DSSS signals in a second frequency range.

21. The method of claim 20, wherein the first frequency range and the second frequency range do not overlap.

22. A subscriber unit comprising:

a direct-sequence spread spectrum (DSSS) transmitter; and

an orthogonal frequency division multiplexing (OFDM) receiver, wherein the subscriber unit is configured to transmit a DSSS signal from the DSSS transmitter in association with an OFDM signal received by the OFDM receiver such that use of the DSSS signal enables communication via the OFDM signal.

23. The subscriber unit of claim 22, wherein the DSSS transmitter comprises a code division multiple access transmitter.

24. The subscriber unit of claim 22, wherein the DSSS transmitter comprises a DSSS transceiver.

25. The subscriber unit of claim 22, comprising a switch coupled to the DSSS transmitter and the OFDM receiver.

26. The subscriber unit of claim 25, comprising an antenna coupled to the switch.

27. The subscriber unit of claim 22, wherein the OFDM receiver is configured to determine a quality metric for the OFDM signal.

28. The subscriber unit of claim 22, wherein the subscriber unit comprises a mobile unit.

29. The subscriber unit of claim 22, wherein the OFDM receiver comprises:

a Fast Fourier Transform (FFT) unit to perform an FFT on the OFDM signal; and

a plurality of processing paths coupled to individual outputs of the FFT unit, each of the plurality of processing paths having a demodulator coupled to the one of the individual outputs of the FFT unit.

30. The subscriber unit of claim 29, wherein the OFDM receiver comprises:

a deinterleaver coupled to an output of one or more of the demodulators; and

a forward error correction decoder coupled to an output of the deinterleaver.

31. The subscriber unit of claim 22, wherein the OFDM receiver and the DSSS receiver are configured to operate on non-overlapping frequency bands.

32. The subscriber unit of claim 22, wherein the subscriber unit is configured to demultiplex the OFDM signal based on time.

33. A method for communicating with a subscriber, the method comprising transmitting orthogonal frequency division multiplexing (OFDM) signals to the subscriber, wherein communication by receipt of the OFDM signals by the subscriber is enabled by a DSSS signal being generated by the subscriber.

34. The method of claim 33 wherein said transmitting comprises:

allocating a first portion of OFDM subcarriers to a first subscriber; and

transmitting OFDM signals to the first subscriber according to the allocation.

35. The method of claim 34 wherein the transmitting further comprises:

allocating a second portion of OFDM subcarriers to a second subscriber; and

transmitting OFDM signals to the second subscriber according to the allocation.

36. The method of claim 34 wherein the allocation is responsive to a quality metric received from the first subscriber.

37. The method of claim 36 wherein the quality metric comprises a SNR.

38. The method of claim 34 wherein the allocation is adaptive.

39. The method of claim 34 wherein the allocation comprises allocating only sub-carriers determined to have at least a minimum quality metric.

40. The method of claim 33, comprising receiving a signal indicative of a quality metric associated with the OFDM signals.

41. The method of claim 40, wherein the receiving of the signal comprises receiving a signal indicative of a signal to noise ration of the OFDM signals.

42. The method of claim 40, comprising selecting a code rate based at least partially on the quality metric.

43. The method of claim 40, comprising selecting a modulation scheme based at least partially on the quality metric.

44. The method of claim 33, wherein the transmitting of the OFDM signals comprises:

transmitting content for a first subscriber using a first time division of the OFDM signals; and

transmitting content for a second subscriber using a second time division of the OFDM signals.

45. A method comprising:

receiving direct-sequence spread spectrum (DSSS) signals from a subscriber unit, wherein the DSSS signals were generated by the subscriber unit in association with received orthogonal frequency division multiplexing (OFDM) signals to enable communication via the OFDM signals.

46. The method of claim 45, wherein the receiving of the DSSS signals comprises receiving a quality metric associated with the OFDM signals.

47. The method of claim 46, comprising transmitting the quality metric to an OFDM transmitter.

48. The method of claim 47, wherein the transmitting of the quality metric comprises transmitting the quality metric to an OFDM transmitter located in a base station, wherein the base station is configured to the DSSS signals from the subscriber unit.