Extended-performance echo-canceled duplex (EP ECD) communication

• US 20040213170A1
• Filed: 04/22/2003
• Published: 10/28/2004
• Est. Priority Date: 04/22/2003
• Status: Abandoned Application

• Current Assignee: Summit Technology Systems LP
• Original Assignee: Summit Technology Systems LP
• Inventors: Bremer, Gordon
• Application Number:
  US10/420,204
• Publication Number:
  US 20040213170A1
• Time in Patent Office: Days
• US Class Current: 370/282
• CPC Class Codes: H04L 5/1423 for simultaneous baseband signals
• CPC Class Codes: H04L 5/16 Half-duplex systems; Simplex/duplex switching; Transmission of break signals non-automatically inverting the direction of transmission

Abstract

The preferred embodiments of the present invention generally improve communications capabilities between at least two devices (arbitrarily called local and remote). In the preferred embodiments of the present invention, the signal levels of communication are adjusted in response to a change between and/or among a plurality of modes. The adjusted signal levels affect not only received signal levels, but also received noise levels of echo. Even after echo cancellation is attempted, imperfect echo cancellation leaves residual echo noise. Thus, adjusting signal levels also adjusts noise levels of residual echo noise. This change in signal levels and the resulting change in residual echo noise leads to a change in signal-to-noise ratios in response to the devices changing between and/or among the plurality of modes. The communication system can be changed to maximize performance over the communication channels with specific signal-to-noise ratios that are established during the plurality of modes.

Claims

1. A method, comprising the steps of:

transmitting a first information-bearing signal on a communications medium, the transmitting occurring in the presence of a received, second information-bearing signal that substantially frequency overlaps the first information-bearing signal;

changing a first plurality of times among at least two different modes;

during each mode, encoding information on the first information-bearing signal at a first non-zero information rate; and

during each mode, causing the first information-bearing signal to exhibit a first non-zero signal level.

2. The method of claim 1, wherein the first non-zero information rate changes at least based upon each change among the at least two different modes of the step of changing the first plurality of times.

3. The method of claim 1, wherein the first non-zero signal level changes at least based upon each change among the at least two different modes of the step of changing the first plurality of times.

4. The method of claim 1, wherein each change among the at least two different modes of the step of changing the first plurality of times occurs without substantial delay.

5. The method of claim 4, wherein substantial delay results from performing a task that significantly delays communicating beyond an amount of time needed to change at least one communication parameter.

6. The method of claim 5, wherein the task that significantly delays communicating is a training task performed on the communications medium.

7. The method of claim 1, wherein the communications medium comprises a subscriber loop.

8. The method of claim 1, wherein the communications medium comprises a telephone communications system.

9. The method of claim 1, wherein the communications medium carries electromagnetic waves.

10. The method of claim 9, wherein the electromagnetic waves are optical.

11. The method of claim 9, wherein the electromagnetic waves are infrared.

12. The method of claim 9, wherein the electromagnetic waves are radio.

13. The method of claim 1, wherein the communications medium comprises carries audio waves.

14. The method of claim 13, wherein the audio waves are carried in air.

15. The method of claim 13, wherein the audio waves are carried in water.

16. The method of claim 1, wherein the at least two different modes are substantially non-overlapping intervals of time and comprise a first mode and a second mode, and wherein the step of changing the first plurality of times among the at least two different modes further comprises the step of changing the first plurality of times between the first mode and the second mode.

17. The method of claim 16, wherein the first mode and the second mode are of equal durations.

18. The method of claim 16, wherein the first mode and the second mode are of unequal durations.

19. The method of claim 16, wherein the first mode and the second mode are of changing durations.

20. The method of claim 16, wherein the first mode and the second mode are of a duration of at least two bit times.

21. The method of claim 16, wherein the first mode provides for a first channel capable of carrying constant bit rate traffic and provides for a second channel capable of carrying variable bit rate traffic.

22. The method of claim 21, wherein the second mode provides for the first channel capable of carrying constant bit rate traffic and does not provide for the second channel capable of carrying variable bit rate traffic.

23. The method of claim 21, wherein the first channel is lower latency and the second channel is higher latency.

24. The method of claim 16, further comprising the step of:

receiving the second information-bearing signal from the communications medium during at least one of the first mode and the second mode, the second information-bearing signal being affected by echo from the transmitting of the first information-bearing signal, wherein the second information-bearing signal encodes information at a second non-zero information rate during at least one of the first mode and the second mode.

25. The method of claim 24, wherein the second non-zero information rate changes at least based upon each change among the at least two different modes of the step of changing the first plurality of times.

26. The method of claim 24, wherein the second non-zero signal level changes at least based upon each change among the at least two different modes of the step of changing the first plurality of times.

27. The method of claim 24, further comprising the step of:

performing echo cancellation during at least one of the first mode and the second mode to improve performance of the receiving of the second information-bearing signal during at least one of the first mode and the second mode.

28. The method of claim 24, wherein the transmitting of the first information-bearing signal is performed by a local device, and wherein the second information-bearing signal was transmitted from a first remote device.

29. The method of claim 28, wherein the local device behaves in the first mode as the first remote device behaves in the second mode.

30. The method of claim 28, wherein the local device behaves in the second mode as the first remote device behaves in the first mode.

31. The method of claim 28, wherein the first information-bearing signal is transmitted from the local device during the first mode at a first local-to-first-remote symbol rate, wherein the second information-bearing signal is transmitted from the first remote device during the first mode at a first first-remote-to-local symbol rate.

32. The method of claim 31, wherein the first local-to-first-remote symbol rate is equal to the first first-remote-to-local symbol rate.

33. The method of claim 31, wherein the first local-to-first-remote symbol rate is not equal to the first first-remote-to-local symbol rate.

34. The method of claim 28, wherein the first information-bearing signal is transmitted from the local device during the second mode at a second local-to-first-remote symbol rate, wherein the second information-bearing signal is transmitted from the first remote device during the second mode at a second first-remote-to-local symbol rate.

35. The method of claim 34, wherein the second local-to-first-remote symbol rate is equal to the second first-remote-to-local symbol rate.

36. The method of claim 34, wherein the second local-to-first-remote symbol rate is not equal to the second first-remote-to-local symbol rate.

37. The method of claim 16, wherein the transmitting of the first information-bearing signal is performed by a local device, and wherein the second information-bearing signal was transmitted from a first remote device.

38. The method of claim 37, wherein L2R S₁ is a signal level of the first information-bearing signal from the local device during the first mode, wherein L2R S₂ is a signal level of the first information-bearing signal from the local device during the second mode, wherein R2L S₁ is a signal level of the second information-bearing signal from the first remote device during the first mode, wherein R2L S₂ is a signal level of the second information-bearing signal from the first remote device during the second mode, and wherein the signal levels of the first and second modes of the local and the first remote devices are related by the inequality of:

L2R S₁×

R2L S₂>

L2R S₂×

R2L S₁.

39. The method of claim 38, wherein the inequality of:

L2R S₁×

R2L S₂>

L2R S₂×

R2L S₁ is met by at least one change in at least one signal space of at least one of the local and the first remote devices in changing between the first mode and the second mode.

40. The method of claim 39, wherein each signal space is associated with a number of signal points, and wherein the at least one change in the at least one signal space involves at least one change in the number of signal points in each of the at least one signal space.

41. The method of claim 39, wherein each signal space is associated with a set of at least one pair of adjacent signal points, wherein each pair of adjacent signal points further is associated with a distance, and wherein the at least one change in the at least one signal space involves at least one change in the distance between at least one pair of adjacent signal points.

42. The method of claim 41, wherein the at least one change in the distance between at least one pair of adjacent signal points is at least partially offset by at least one change in error control coding in changing between the first mode and the second mode.

43. The method of claim 37, wherein each signal space is associated with a plurality of signal points and associated with a mapping of information to the plurality of signal points, wherein the inequality of:

L2R S₁×

R2L S₁>

L2R S₂×

R2L S₁ is met by at least one change in a first mapping of information to first signal points without a change in an associated first signal space in changing between the first mode and the second mode.

44. The method of claim 37, wherein the step of changing the first plurality of times among the at least two different modes is performed dynamically based at least upon at least one of a local device data transmission demand and a first remote device data transmission demand.

45. The method of claim 44, wherein the local device data transmission demand increases responsive to increases in an amount of local data queued in the local device to be transmitted into the communications medium, and wherein the local device data transmission demand decreases responsive to decreases in the amount of local data queued in the local device to be transmitted into the communications medium.

46. The method of claim 44, wherein the first remote device data transmission demand increases responsive to increases in an amount of first remote data queued in the first remote device to be transmitted into the communications medium, and wherein the first remote device data transmission demand decreases responsive to decreases in the amount of first remote data queued in the first remote device to be transmitted into the communications medium.

47. The method of claim 1, wherein ATM data is carried on the first information-bearing signal during at least one of the at least two different modes.

48. The method of claim 1, wherein IP data is carried on the first information-bearing signal during at least one of the at least two different modes.

49. The method of claim 1, wherein the step of transmitting the first information-bearing signal, the step of changing the first plurality of times, the step of encoding information on the first information-bearing signal, and the step of causing the first information-bearing signal to exhibit are performed by a local device during a first manner of operation in communicating with a first remote device.

50. The method of claim 49, further comprising the steps performed by the local device of:

changing between the first manner of operation and a second manner of operation, the second manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

communicating with the first remote device using time division duplexing (TDD) during the second manner of operation.

51. The method of claim 50, wherein the time division duplexing (TDD) is adaptive time division duplexing (ATDD).

52. The method of claim 49, further comprising the steps performed by the local device of:

changing between the first manner of operation and a third manner of operation, the third manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

communicating with the first remote device using echo cancelled duplexing (ECD) during the third manner of operation.

53. The method of claim 49, wherein the at least two different modes are at least two different first-manner-of-operation modes and wherein each mode of the at least two different first-manner-of-operation modes is a first-manner-of-operation mode.

54. The method of claim 53, further comprising the steps performed by the local device of:

changing between the first manner of operation and a fourth manner of operation, the fourth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

communicating with a second remote device during the fourth manner of operation by performing the steps further comprising;

transmitting a third information-bearing signal on the communications medium, the transmitting occurring in the presence of a received, fourth information-bearing signal that substantially frequency overlaps the third information-bearing signal;

changing a second plurality of times among at least two different fourth-manner-of-operation modes;

during each fourth-manner-of-operation mode, encoding information on the third information-bearing signal at a third non-zero information rate; and

during each fourth-manner-of-operation mode, causing the third information-bearing signal to exhibit a third non-zero signal level.

55. The method of claim 54, wherein the third non-zero information rate changes at least based upon each change among the at least two different fourth-manner-of-operation modes of the step of changing the second plurality of times.

56. The method of claim 54, wherein the third non-zero signal level changes at least based upon each change among the at least two different fourth-manner-of-operation modes of the step of changing the second plurality of times.

57. The method of claim 54, wherein the first information-bearing signal, the second information-bearing signal, the third information-bearing signal, and the fourth information-bearing signal all substantially overlap each other in frequency.

58. The method of claim 49, further comprising the steps performed by the local device of:

changing between the first manner of operation and a fifth manner of operation, the fifth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

communicating with a second remote device using time division duplexing (TDD) during the fifth manner of operation.

59. The method of claim 58, wherein the time division duplexing (TDD) is adaptive time division duplexing (ATDD).

60. The method of claim 49, further comprising the steps performed by the local device of:

changing between the first manner of operation and a sixth manner of operation, the sixth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

communicating with a second remote device using echo cancelled duplexing (ECD) during the sixth manner of operation.

61. The method of claim 49, further comprising the step of testing the communications medium to determine an efficient duplexing configuration from among:

the first manner of operation, a second manner of operation involving time-division duplexing (TDD), and a third manner of operation involving echo cancelled duplexing (ECD).

62. The method of claim 1, wherein the first information-bearing signal encodes information using at least one modulation type selected from the group consisting of:

carrierless amplitude phase (CAP) modulation, quadrature amplitude modulation (QAM), pulse amplitude modulation (PAM), discrete multi-tone (DMT) modulation, frequency-shift keying (FSK) modulation, and optical modulation.

63. The method of claim 1, further comprising the step of:

during at least one first mode of the at least two different modes, communicating first information regarding a first information rate at which the step of transmitting the first information-bearing signal is occurring.

64. The method of claim 63, further comprising the step of:

during the at least one first mode of the at least two different modes, communicating second information regarding a second information rate at which the second information-bearing signal is capable of being received during at least one second mode of the at least two different modes.

65. The method of claim 64, further comprising the step of:

changing at least one of the first information rate and the second information rate seamlessly and without error by using at least one of the first information and the second information.

66. A communication apparatus comprising:

means for transmitting a first information-bearing signal on a communications medium, the transmitting occurring in the presence of a received, second information-bearing signal that substantially frequency overlaps the first information-bearing signal; and

means for changing a first plurality of times among at least two different modes, wherein during each mode, information is encoded on the first information-bearing signal at a first non-zero information rate, and wherein during each mode, the first information-bearing signal exhibits a first non-zero signal level.

67. The communication apparatus of claim 66, wherein the first non-zero information rate changes at least based upon each change among the at least two different modes of the means for changing the first plurality of times.

68. The communication apparatus of claim 66, wherein the first non-zero signal level changes at least based upon each change among the at least two different modes of the means for changing the first plurality of times.

69. The communication apparatus of claim 66, wherein each change among the at least two different modes of the means for changing the first plurality of times occurs without substantial delay.

70. The communication apparatus of claim 69, wherein substantial delay results from performing a task that significantly delays communicating beyond an amount of time needed to change at least one communication parameter.

71. The communication apparatus of claim 70, wherein the task that significantly delays communicating is a training task performed on the communications medium.

72. The communication apparatus of claim 66, wherein the communications medium comprises a subscriber loop.

73. The communication apparatus of claim 66, wherein the communications medium comprises a telephone communications system.

74. The communication apparatus of claim 66, wherein the communications medium carries electromagnetic waves.

75. The communication apparatus of claim 74, wherein the electromagnetic waves are optical.

76. The communication apparatus of claim 74, wherein the electromagnetic waves are infrared.

77. The communication apparatus of claim 74, wherein the electromagnetic waves are radio.

78. The communication apparatus of claim 66, wherein the communications medium comprises carries audio waves.

79. The communication apparatus of claim 78, wherein the audio waves are carried in air.

80. The communication apparatus of claim 78, wherein the audio waves are carried in water.

81. The communication apparatus of claim 66, wherein the at least two different modes are substantially non-overlapping intervals of time and comprise a first mode and a second mode, and wherein the means for changing the first plurality of times among the at least two different modes further comprises a means for changing the first plurality of times between the first mode and the second mode.

82. The communication apparatus of claim 81, wherein the first mode and the second mode are of equal durations.

83. The communication apparatus of claim 81, wherein the first mode and the second mode are of unequal durations.

84. The communication apparatus of claim 81, wherein the first mode and the second mode are of changing durations.

85. The communication apparatus of claim 81, wherein the first mode and the second mode are of a duration of at least two bit times.

86. The communication apparatus of claim 81, wherein the first mode provides for a first channel capable of carrying constant bit rate traffic and provides for a second channel capable of carrying variable bit rate traffic.

87. The communication apparatus of claim 86, wherein the second mode provides for the first channel capable of carrying constant bit rate traffic and does not provide for the second channel capable of carrying variable bit rate traffic.

88. The communication apparatus of claim 86, wherein the first channel is lower latency and the second channel is higher latency.

89. The communication apparatus of claim 81, further comprising:

means for receiving the second information-bearing signal from the communications medium during at least one of the first mode and the second mode, the second information-bearing signal being affected by echo from the transmitting of the first information-bearing signal, wherein the second information-bearing signal encodes information at a second non-zero information rate during at least one of the first mode and the second mode.

90. The communication apparatus of claim 89, wherein the second non-zero information rate changes at least based upon each change among the at least two different modes of means for changing the first plurality of times.

91. The communication apparatus of claim 89, wherein the second non-zero signal level changes at least based upon each change among the at least two different modes of the means for changing the first plurality of times.

92. The communication apparatus of claim 89, further comprising:

means for performing echo cancellation during at least one of the first mode and the second mode to improve performance of the means for receiving of the second information-bearing signal during at least one of the first mode and the second mode.

93. The communication apparatus of claim 89, wherein the means for transmitting of the first information-bearing signal is at least part of a local device, and wherein the second information-bearing signal was transmitted from a first remote device.

94. The communication apparatus of claim 93, wherein the local device behaves in the first mode as the first remote device behaves in the second mode.

95. The communication apparatus of claim 93, wherein the local device behaves in the second mode as the first remote device behaves in the first mode.

96. The communication apparatus of claim 93, wherein the first information-bearing signal is transmitted from the local device during the first mode at a first local-to-first-remote symbol rate, wherein the second information-bearing signal is transmitted from the first remote device during the first mode at a first first-remote-to-local symbol rate.

97. The communication apparatus of claim 96, wherein the first local-to-first-remote symbol rate is equal to the first first-remote-to-local symbol rate.

98. The communication apparatus of claim 96, wherein the first local-to-first-remote symbol rate is not equal to the first first-remote-to-local symbol rate.

99. The communication apparatus of claim 93, wherein the first information-bearing signal is transmitted from the local device during the second mode at a second local-to-first-remote symbol rate, wherein the second information-bearing signal is transmitted from the first remote device during the second mode at a second first-remote-to-local symbol rate.

100. The communication apparatus of claim 99, wherein the second local-to-first-remote symbol rate is equal to the second first-remote-to-local symbol rate.

101. The communication apparatus of claim 99, wherein the second local-to-first-remote symbol rate is not equal to the second first-remote-to-local symbol rate.

102. The communication apparatus of claim 81, wherein the means for transmitting of the first information-bearing signal is at least part of a local device, and wherein the second information-bearing signal was transmitted from a first remote device.

103. The communication apparatus of claim 102, wherein L2R S₁ is a signal level of the first information-bearing signal from the local device during the first mode, wherein L2R S₂ is a signal level of the first information-bearing signal from the local device during the second mode, wherein R2L SI is a signal level of the second information-bearing signal from the first remote device during the first mode, wherein R2L S₂ is a signal level of the second information-bearing signal from the first remote device during the second mode, and wherein the signal levels of the first and second modes of the local and the first remote devices are related by the inequality of:

L2R S₁×

R2L S₂>

L2R S₂×

R2L S₁.

104. The communication apparatus of claim 103, wherein the inequality of:

L2R S₁×

R2L S₂>

L2R S₂×

R2L S₁ is met by at least one change in at least one signal space of at least one of the local and the first remote devices responsive to the means for changing the first plurality of times changing at least once between the first mode and the second mode.

105. The communication apparatus of claim 104, wherein each signal space is associated with a number of signal points, and wherein the at least one change in the at least one signal space involves at least one change in the number of signal points in each of the at least one signal space.

106. The communication apparatus of claim 104, wherein each signal space is associated with a set of at least one pair of adjacent signal points, wherein each pair of adjacent signal points further is associated with a distance, and wherein the at least one change in the at least one signal space involves at least one change in the distance between at least one pair of adjacent signal points.

107. The communication apparatus of claim 106, wherein the at least one change in the distance between at least one pair of adjacent signal points is at least partially offset by at least one change in error control coding responsive to the means for changing the first plurality of times changing at least once between the first mode and the second mode.

108. The communication apparatus of claim 102, wherein each signal space is associated with a plurality of signal points and associated with a mapping of information to the plurality of signal points, wherein the inequality of:

L2R S₁×

R2L S₂>

L2R S₂×

R2L S₁ is met by at least one change in a first mapping of information to first signal points without a change in an associated first signal space responsive to the means for changing the first plurality of times changing at least once between the first mode and the second mode.

109. The communication apparatus of claim 102, wherein the means for changing the first plurality of times among the at least two different modes performs dynamically based at least upon at least one of a local device data transmission demand and a first remote device data transmission demand.

110. The communication apparatus of claim 109, wherein the local device data transmission demand increases responsive to increases in an amount of local data queued in the local device to be transmitted into the communications medium, and wherein the local device data transmission demand decreases responsive to decreases in the amount of local data queued in the local device to be transmitted into the communications medium.

111. The communication apparatus of claim 109, wherein the first remote device data transmission demand increases responsive to increases in an amount of first remote data queued in the first remote device to be transmitted into the communications medium, and wherein the first remote device data transmission demand decreases responsive to decreases in the amount of first remote data queued in the first remote device to be transmitted into the communications medium.

112. The communication apparatus of claim 66, wherein ATM data is carried on the first information-bearing signal during at least one of the at least two different modes.

113. The communication apparatus of claim 66, wherein IP data is carried on the first information-bearing signal during at least one of the at least two different modes.

114. The communication apparatus of claim 66, wherein the means for transmitting the first information-bearing signal and the means for changing the first plurality of times are at least part of a local device and operate during a first manner of operation in communicating with a first remote device.

115. The communication apparatus of claim 114, further comprising:

means for changing between the first manner of operation and a second manner of operation, the second manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

means for communicating with the first remote device using time division duplexing (TDD) during the second manner of operation.

116. The communication apparatus of claim 115, wherein the time division duplexing (TDD) is adaptive time division duplexing (ATDD).

117. The communication apparatus of claim 114, further comprising:

means for changing between the first manner of operation and a third manner of operation, the third manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

means for communicating with the first remote device using echo cancelled duplexing (ECD) during the third manner of operation.

118. The communication apparatus of claim 114, wherein the at least two different modes are at least two different first-manner-of-operation modes and wherein each mode of the at least two different first-manner-of-operation modes is a first-manner-of-operation mode.

119. The communication apparatus of claim 118, further comprising:

means for changing between the first manner of operation and a fourth manner of operation, the fourth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

means for communicating with a second remote device during the fourth manner of operation, the means for communicating further comprising;

means for transmitting a third information-bearing signal on the communications medium, the means for transmitting the third information-bearing signal operating in the presence of a received, fourth information-bearing signal that substantially frequency overlaps the third information-bearing signal; and

means for changing a second plurality of times among at least two different fourth-manner-of-operation modes, wherein during each fourth-manner-of-operation mode, information is encoded on the third information-bearing signal at a third non-zero information rate, and wherein during each fourth-manner-of-operation mode, the third information-bearing signal exhibits a third non-zero signal level.

120. The communication apparatus of claim 119, wherein the third non-zero information rate changes at least based upon each change among the at least two different fourth-manner-of-operation modes of the means for changing the second plurality of times.

121. The communication apparatus of claim 119, wherein the third non-zero signal level changes at least based upon each change among the at least two different fourth-manner-of-operation modes of the means for changing the second plurality of times.

122. The communication apparatus of claim 119, wherein the first information-bearing signal, the second information-bearing signal, the third information-bearing signal, and the fourth information-bearing signal all substantially overlap each other in frequency.

123. The communication apparatus of claim 114, further comprising:

means for changing between the first manner of operation and a fifth manner of operation, the fifth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

means for communicating with a second remote device using time division duplexing (TDD) during the fifth manner of operation.

124. The communication apparatus of claim 123, wherein the time division duplexing (TDD) is adaptive time division duplexing (ATDD).

125. The communication apparatus of claim 114, further comprising:

means for changing between the first manner of operation and a sixth manner of operation, the sixth manner of operation being a substantially non-overlapping interval of time with the first manner of operation; and

means for communicating with a second remote device using echo cancelled duplexing (ECD) during the sixth manner of operation.

126. The communication apparatus of claim 114, further comprising means for testing the communications medium to determine an efficient duplexing configuration from among:

the first manner of operation, a second manner of operation involving time-division duplexing (TDD), and a third manner of operation involving echo cancelled duplexing (ECD).

127. The communication apparatus of claim 66, wherein the first information-bearing signal encodes information using at least one modulation type selected from the group consisting of:

carrierless amplitude phase (CAP) modulation, quadrature amplitude modulation (QAM), pulse amplitude modulation (PAM), discrete multi-tone (DMT) modulation, frequency-shift keying (FSK) modulation, and optical modulation.

128. The communication apparatus of claim 66, further comprising means for communicating first information regarding a first information rate at which the means for transmitting the first information-bearing signal is operating, the means for communicating the first information operating during at least one first mode of the at least two different modes.

129. The communication apparatus of claim 128, further comprising means for communicating second information regarding a second information rate at which the second information-bearing signal is capable of being received during at least one second mode of the at least two different modes.

130. The communication apparatus of claim 129, further comprising means for:

changing at least one of the first information rate and the second information rate seamlessly and without error by using at least one of the first information and the second information.