Shifted training sequences in a communications system

• US 7,339,981 B2
• Filed: 07/09/2002
• Issued: 03/04/2008
• Est. Priority Date: 07/09/2002
• Status: Active Grant

• Current Assignee: Tahoe Research Limited (f/k/a Learndale Limited) (Vector Capital Corporation)
• Original Assignee: ArrayComm LLC (Ygomi LLC)
• Inventors: Dogan, Mithat C.
• Primary Examiner(s): Fan, Chieh M.
• Assistant Examiner(s): Joseph, Jaison
• Application Number:
  US10/191,642
• Publication Number:
  US 20040008760A1
• Time in Patent Office: 2,065 Days
• Field of Search: 375/219, 375/220, 375/343, 370/337, 342/457
• US Class Current: 375/219
• CPC Class Codes: H04L 25/0226 sounding signals per se

Abstract

Embodiments of the present invention can be used to select a training sequence used by a base station and a user terminal for communications. In one embodiment, selecting the training sequence to use includes first selecting a training sequence from a set of training sequences. Then, a shift indicator is received, the shift indicator indicating a number of symbols the training sequence is to be shifted. A shifted training sequence is generated by shifting the selected training sequence by the number indicated by the received shift indicator, and the shifted training sequence is used for communication with a first transceiver on a communications channel. In another embodiment, a shift indicator indicating a number of symbols a training sequence is to be shifted is first selected, and then used to generate a shifted training sequence by shifting the training sequence by the number of symbols indicated by the selected shift indicator. The shifted training sequence is then used for communicating with a transceiver on a communications channel.

Claims

1. A method performed by a communications device comprising:

receiving an identification of a first transceiver over a wireless communications channel;

selecting a core training sequence based on the received identification;

receiving a spatial channel assignment from the first transceiver;

selecting a shift indicator using the spatial channel assignment, the shift indicator indicating a number of symbols that the core training sequence stored in a memory of the communications device is to be shifted;

generating a shifted training sequence by shifting the core training sequence by the number of symbols indicated by the selected shift indicator, and

communicating from a second transceiver of the communications device on the assigned communications channel using the shifted training sequence.

2. The method of claim 1, wherein communicating comprises sending a signal to the first transceiver, the signal containing the shifted training sequence.

3. The method of claim 1, wherein communicating comprises receiving a signal from the second transceiver, the signal containing a received training sequence corresponding to the shifted training sequence.

4. The method of claim 3, wherein communicating further comprises training by comparing the received training sequence with the shifted training sequence.

5. The method of claim 4, wherein training comprises one or more of measuring a channel parameter of the assigned communications channel, measuring a signal to noise ratio (SNR), measuring a signal to interference and noise ratio (SINR), estimating a spatial parameter, estimating a timing offset of the communications channel, estimating a frequency offset of the communications channel, synchronizing symbols, synchronizing frames, calibrating a transceiver, calibrating an equalizer, and calculating spatial and temporal filter weights.

6. The method of claim 1, wherein receiving an identification comprises receiving an identifier of the first transceiver to the second transceiver in a broadcast channel.

7. The method of claim 6, wherein the first transceiver comprises a base station, the identifier of the first transceiver comprises a Base Station Color Code (BSCC), and the training sequence comprises a core training sequence corresponding to the BSCC.

8. The method of claim 1, further comprising:

selecting a second shift indicator indicating a different number of symbols than the shift indicator;

generating a second shifted training sequence by cyclically shifting the training sequence by the number indicated by the second shift indicator;

communicating with a third transceiver on the communications channel using the second shifted training sequence.

9. The method of claim 8, wherein communicating with the third transceiver comprises sending a signal containing the shifted training sequence to the second transceiver and sending a signal containing the second shifted training sequence to the third transceiver simultaneously on the same communications channel.

10. The method of claim 8, wherein communicating with the third transceiver comprises receiving a signal containing the shifted training sequence from the second transceiver and receiving a signal containing the second shifted training sequence from the third transceiver simultaneously on the same communications channel.

11. The method of claim 1, wherein the training sequence has a maximum out-of-phase auto-correlation below a threshold.

12. The method of claim 8, wherein the correlation between the shifted training sequence and the second shifted training sequence is below a threshold.

13. A communications device comprising:

a processor to;

receive an identification of a first transceiver over a wireless communications channel;

select a core training sequence based on the received identification;

receive a spatial channel assignment from the first transceiver;

select a shift indicator using the spatial channel assignment, the shift indicator indicating a number of symbols that the core training sequence is to be shifted; and

generate a shifted training sequence by shifting the core training sequence by the number of symbols indicated by the selected shift indicator; and

a second transceiver to communicate with the first transceiver on the assigned communications channel using the shifted training sequence.

14. The communications device of claim 13, wherein the second transceiver communicates with the first transceiver by sending a signal to the first transceiver, the signal containing the shifted training sequence.

15. The communications device of claim 13, wherein the second transceiver communicates with the first transceiver by receiving a signal from the first transceiver, the signal containing a received training sequence corresponding to the shifted training sequence.

16. The communications device of claim 15, wherein the processor uses the shifted training sequence for training by comparing the received training sequence with the shifted training sequence.

17. The communications device of claim 16, wherein training comprises one or more of measuring a channel parameter of the assigned communications channel, measuring a signal to noise ratio (SNR), measuring a signal to interference and noise ratio (SINR), estimating a spatial parameter, estimating a timing offset of the communications channel, estimating a frequency offset of the communications Channel, synchronizing symbols, synchronizing frames, calibrating a transceiver, calibrating an equalizer, and calculating spatial and temporal filter weights.

18. The communications device of claim 13, wherein the first transceiver sends an identifier of the communications device to the second transceiver.

19. The communications device of claim 18, wherein the first transceiver comprises a base station, the identifier of the first transceiver comprises a Base Station Color Code (BSCC), and the training sequence comprises a core training sequence corresponding to the BSCC.

20. The communications device of claim 13, wherein the processor:

selects a second shift indicator indicating a different number of symbols than the shift indicator;

generates a second shifted training sequence by cyclically shifting the training sequence by the number indicated by the second shift indicator; and

wherein the first transceiver communicates with a second remote transceiver on the communications channel using the second shifted training sequence.

21. The communications device of claim 20, wherein the first transceiver sends a signal containing the shifted training sequence to the second transceiver, and sends a signal containing the second shifted training sequence to the second remote transceiver simultaneously on the same communications channel.

22. The communications device of claim 20, wherein the first transceiver receives a signal containing the shifted training sequence from the second transceiver, and receives a signal containing the second shifted training sequence from the second remote transceiver simultaneously on the same communications channel.

23. The communications device of claim 13, wherein the training sequence has a maximum out-of-phase auto-correlation below a threshold.

24. The communications device of claim 20, wherein the correlation between the shifted training sequence and the second shifted training sequence is below a threshold.

25. The communications device of claim 20, wherein the second transceiver and the second remote transceiver comprise user terminals, and the first transceiver comprises a base station.

26. A machine-readable medium having stored thereon data representing instructions that, when executed by a processor, cause the processor to perform operations comprising:

receiving an identification of a first transceiver over a wireless communications channel;

selecting a core training sequence based on the received identification;

receiving a spatial channel assignment from the first transceiver;

selecting a shift indicator using the spatial channel assignment, the shift indicator indicating a number of symbols that the core training sequence stored in a memory of the communications device is to be shifted;

generating a shifted training sequence by shifting the core training sequence by the number of symbols indicated by the selected shift indicator; and

communicating from a second transceiver of the communications device on the assigned communications channel using the shifted training sequence.

27. The machine-readable medium of claim 26, wherein communicating comprises sending a signal from the second transceiver to the first transceiver, the signal containing the shifted training sequence.

28. The machine-readable medium of claim 26, wherein communicating comprises receiving a signal at the first transceiver from the second transceiver, the signal containing a received training sequence corresponding to the shifted training sequence.

29. The machine-readable medium of claim 26, wherein the instructions further cause the processor to perform operations comprising:

selecting a second shift indicator indicating a different number of symbols than the shift indicator;

generating a second shifted training sequence by cyclically shifting the training sequence by the number indicated by the second shift indicator;

communicating with a third transceiver on the communications channel using the second shifted training sequence.

30. The machine-readable medium of claim 29, wherein communicating with the third transceiver comprises sending a signal containing the shifted training sequence from the first transceiver to the second transceiver and sending a signal containing the second shifted training sequence from the first transceiver to the third transceiver simultaneously on the same communications channel.

31. The machine-readable medium of claim 29, wherein communicating with the third transceiver comprises receiving a signal containing the shifted training sequence from the second transceiver at a first transceiver and receiving a signal containing the second shifted training sequence from the third transceiver at the first transceiver simultaneously on the same communications channel.

32. The machine-readable medium of claim 26, wherein the training sequence has a maximum out-of-phase auto-correlation below a threshold.

33. The machine-readable medium of claim 29, wherein the correlation between the shifted training sequence and the second shifted training sequence is below a threshold.