Enabling phase tracking for a communication device

1. A communication device for enabling phase tracking, comprising:

a processor;

memory in electronic communication with the processor;

instructions stored in the memory, the instructions being executable to:

generate a plurality of pilot symbols, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank and enables comparing a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate; and

transmit the plurality of pilot symbols during a training period.

2. The communication device of claim 1 , wherein the instructions are further executable to transmit data or training symbols.

3. The communication device of claim 2 , wherein the data or training symbols are Orthogonal Frequency-Division Multiplexing (OFDM) data or training symbols.

4. The communication device of claim 1 , wherein the pilot symbols are Orthogonal Frequency-Division Multiplexing (OFDM) pilot symbols.

5. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix comprises at least one pair of identical pilot symbols.

6. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix is a rank-deficient pilot mapping matrix R, wherein each row corresponds to pilot symbols transmitted on a different spatial stream and each column corresponds to pilot symbols transmitted on different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

7. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix for four spatial streams and four Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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8. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix for six spatial streams and six Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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9. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix for eight spatial streams and eight Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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10. The communication device of claim 1 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11 ac specifications.

11. The communication device of claim 1 , wherein the pilot symbols are transmitted on tones reserved for pilot tones in Very High Throughput-Long Training Fields (VHT-LTFs).

12. The communication device of claim 1 , wherein the communication device is a wireless communication device.

13. The communication device of claim 1 , wherein the rank-deficient pilot mapping matrix has a number of linearly independent rows or columns less than a smallest dimension of the pilot mapping matrix.

14. A communication device for tracking phase, comprising:

a processor;

memory in electronic communication with the processor;

instructions stored in the memory, the instructions being executable to:

receive a plurality of pilot symbols from a sending communication device during a training period, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank;

compare a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate;

estimate a channel based on the phase estimate and the pilot symbols; and

receive data from the sending communication device using the channel estimate.

15. The communication device of claim 14 , wherein the pilot symbols are Orthogonal Frequency-Division Multiplexing (OFDM) pilot symbols.

16. The communication device of claim 14 , wherein the rank-deficient pilot mapping matrix comprises at least one pair of identical pilot symbols.

17. The communication device of claim 14 , wherein the rank-deficient pilot mapping matrix is a rank-deficient pilot mapping matrix R, wherein each row corresponds to pilot symbols transmitted on a different spatial stream and each column corresponds to pilot symbols transmitted on different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

18. The communication device of claim 14 , wherein the phase estimate is determined based on identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

19. The communication device of claim 16 , wherein the instructions are further executable to determine the phase estimate based on the at least one pair of identical pilot symbols.

20. The communication device of claim 16 , wherein the phase estimate is determined by computing a cross-correlation of the identical pilot symbols.

21. The communication device of claim 16 , wherein the phase estimate is determined by computing a phase delta of the identical pilot symbols.

22. The communication device of claim 14 , wherein the phase estimate is determined by computing a cross-correlation of identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

23. The communication device of claim 14 , wherein the phase estimate is determined by computing a phase delta of identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

24. The communication device of claim 14 , wherein the plurality of pilot symbols is received during a training period.

25. The communication device of claim 24 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

26. The communication device of claim 14 , wherein the phase estimate is determined during a training period.

27. The communication device of claim 26 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

28. The communication device of claim 14 , wherein the channel is estimated during a training period.

29. The communication device of claim 28 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

30. The communication device of claim 14 , wherein the communication device is a base station.

31. A method for enabling phase tracking, comprising:

generating, on a communication device, a plurality of pilot symbols, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank and enables comparing a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate; and

transmitting the plurality of pilot symbols during a training period.

32. The method of claim 31 , further comprising transmitting data or training symbols.

33. The method of claim 32 , wherein the data or training symbols are Orthogonal Frequency-Division Multiplexing (OFDM) data or training symbols.

34. The method of claim 31 , wherein the pilot symbols are Orthogonal Frequency-Division Multiplexing (OFDM) pilot symbols.

35. The method of claim 31 , wherein the rank-deficient pilot mapping matrix comprises at least one pair of identical pilot symbols.

36. The method of claim 31 , wherein the rank-deficient pilot mapping matrix is a rank-deficient pilot mapping matrix R, wherein each row corresponds to pilot symbols transmitted on a different spatial stream and each column corresponds to pilot symbols transmitted on different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

37. The method of claim 31 , wherein the rank-deficient pilot mapping matrix for four spatial streams and four Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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38. The method of claim 31 , wherein the rank-deficient pilot mapping matrix for six spatial streams and six Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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39. The method of claim 31 , wherein the rank-deficient pilot mapping matrix for eight spatial streams and eight Orthogonal Frequency-Division Multiplexing (OFDM) symbols is

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40. The method of claim 31 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

41. The method of claim 31 , wherein the pilot symbols are transmitted on tones reserved for pilot tones in Very High Throughput-Long Training Fields (VHT-LTFs).

42. The method of claim 31 , wherein the communication device is a wireless communication device.

43. A method for tracking phase, comprising:

receiving, by a communication device, a plurality of pilot symbols from a sending communication device during a training period, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank;

comparing, by the communication device, a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate;

estimating a channel based on the phase estimate and the pilot symbols; and

receiving data from the sending communication device using the channel estimate.

44. The method of claim 43 , wherein the pilot symbols are Orthogonal Frequency-Division Multiplexing (OFDM) pilot symbols.

45. The method of claim 43 , wherein the rank-deficient pilot mapping matrix comprises at least one pair of identical pilot symbols.

46. The method of claim 43 , wherein the rank-deficient pilot mapping matrix is a rank-deficient pilot mapping matrix R, wherein each row corresponds to pilot symbols transmitted on a different spatial stream and each column corresponds to pilot symbols transmitted on different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

47. The method of claim 43 , wherein the phase estimate is determined based on identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

48. The method of claim 45 , further comprising determining the phase estimate based on the at least one pair of identical pilot symbols.

49. The method of claim 45 , wherein the phase estimate is determined by computing a cross-correlation of the identical pilot symbols.

50. The method of claim 45 , wherein the phase estimate is determined by computing a phase delta of the identical pilot symbols.

51. The method of claim 43 , wherein the phase estimate is determined by computing a cross-correlation of identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

52. The method of claim 43 , wherein the phase estimate is determined by computing a phase delta of identical pilot symbols transmitted on all spatial streams but across different Orthogonal Frequency-Division Multiplexing (OFDM) symbols.

53. The method of claim 43 , wherein the plurality of pilot symbols is received during a training period.

54. The method of claim 53 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

55. The method of claim 43 , wherein the phase estimate is determined during a training period.

56. The method of claim 55 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

57. The method of claim 43 , wherein the channel is estimated during a training period.

58. The method of claim 57 , wherein the training period comprises Very High Throughput-Long Training Field (VHT-LTF) symbols transmitted according to Institute of Electrical and Electronics Engineers (IEEE) 802.11ac specifications.

59. The method of claim 43 , wherein the communication device is a base station.

60. A computer-program product for enabling phase tracking comprising a non-transitory tangible computer-readable medium having instructions thereon, the instructions comprising:

code for causing a communication device to generate a plurality of pilot symbols, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank and enables comparing a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate; and

code for causing the communication device to transmit the plurality of pilot symbols during a training period.

61. A computer-program product for tracking phase comprising a non-transitory tangible computer-readable medium having instructions thereon, the instructions comprising:

code for causing a communication device to receive a plurality of pilot symbols from a sending communication device during a training period, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank;

code for causing the communication device to compare a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate;

code for causing the communication device to estimate a channel based on the phase estimate and the pilot symbols; and

code for causing the communication device to receive data from the sending communication device using the channel estimate.

62. The computer-program product of claim 61 , wherein the phase estimate is determined during a training period.

63. An apparatus for enabling phase tracking, comprising:

means for generating a plurality of pilot symbols, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank and enables comparing a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate; and

means for transmitting the plurality of pilot symbols during a training period.

64. An apparatus for tracking phase, comprising:

means for receiving a plurality of pilot symbols from a sending communication device during a training period, wherein the pilot symbols conform to a rank-deficient pilot mapping matrix that has less than full rank;

means for comparing a phase of a repeated pilot symbol set to a phase of an original pilot symbol set to determine a phase estimate;

means for estimating a channel based on the phase estimate and the pilot symbols; and

means for receiving data from the sending communication device using the channel estimate.

65. The apparatus of claim 64 , wherein the phase estimate is determined during a training period.