Shifted training sequences in a communications system

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.