LOCAL AND WIDE-AREA TRANSMISSIONS IN A WIRELESS BROADCAST NETWORK

• US 20100098032A1
• Filed: 12/23/2009
• Published: 04/22/2010
• Est. Priority Date: 10/24/2003
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Subramaniam, Anand, Viswanathan, Krishnamurthy, Vijayan, Rajiv, Walker, Gordon Kent, Ling, Fuyun, Mantravadi, Ashok, Murali, Ramaswamy
• Granted Patent: US 8,355,354 B2
• Time in Patent Office: Days
• US Class Current: 370/336
• CPC Class Codes: H04L 12/189 in combination with wireless systems selective distribution or broadcast in wireless communication networks H04W4/06
• CPC Class Codes: H04L 5/0007 the frequencies being orthogonal, e.g. OFDM(A), DMT
• CPC Class Codes: H04L 5/0041 Frequency-non-contiguous
• CPC Class Codes: H04L 5/0044 allocation of payload
• CPC Class Codes: H04L 5/0048 Allocation of pilot signals, i.e. of signals known to the receiver
• CPC Class Codes: H04W 72/30 Resource management for broadcast services

Abstract

To broadcast different types of transmission having different tiers of coverage in a wireless broadcast network, each base station processes data for a wide-area transmission in accordance with a first mode (or coding and modulation scheme) to generate data symbols for the wide-area transmission and processes data for a local transmission in accordance with a second mode to generate data symbols for the local transmission. The first and second modes are selected based on the desired coverage for wide-area and local transmissions, respectively. The base station also generates pilots and overhead information for local and wide-area transmissions. The data, pilots, and overhead information for local and wide-area transmissions are multiplexed onto their transmission spans, which may be different sets of frequency subbands, different time segments, or different groups of subbands in different time segments. More than two different types of transmission may also be multiplexed and broadcast.

Claims

1. A method of broadcasting data in a wireless broadcast network, comprising:

multiplexing data for a wide-area transmission onto a first transmission span, the wide-area transmission being sent from a plurality of transmitters in the network;

multiplexing data for a local transmission onto a second transmission span, the local transmission being sent from a subset of the plurality of transmitters; and

broadcasting the local and wide-area transmissions via a wireless link.

2. The method of claim 1, wherein different local transmissions are sent from different subsets of the plurality of transmitters.

3. The method of claim 1, wherein different wide-area transmissions are sent from different pluralities of transmitters.

4. The method of claim 1, further comprising:

multiplexing data for venue transmission onto a third transmission span, the venue transmission being sent from a smaller subset of the subset of the plurality of transmitters.

5. The method of claim 1, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second time segments, respectively, of a frame of a predetermined time duration.

6. The method of claim 1, wherein the data for the wide-area transmission is frequency division multiplexed (FDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second sets of frequency subbands, respectively, obtained with multi-carrier modulation.

7. The method of claim 1, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM).

8. The method of claim 7, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

9. The method of claim 8, wherein the data for the local transmission is multiplexed onto fewer than all usable frequency subbands to reduce interference.

10. The method of claim 9, wherein the data for the local transmission from the subset of the plurality of transmitters is multiplexed onto frequency subbands that are orthogonal to frequency subbands used by at least one other subset of the plurality of transmitters.

11. The method of claim 9, wherein the data for the local transmission is multiplexed onto frequency subbands pseudo-randomly selected from among all usable frequency subbands.

12. The method of claim 1, further comprising:

processing the data for the wide-area transmission in accordance with a first coding and modulation scheme, wherein the processed data for the wide-area transmission is multiplexed onto the first transmission span; and

processing the data for the local transmission in accordance with a second coding and modulation scheme, wherein the processed data for the local transmission is multiplexed onto the second transmission span.

13. The method of claim 12, wherein the first and second coding and modulation schemes are selected based on desired coverage for the wide-area and local transmissions, respectively.

14. The method of claim 12, wherein the second coding and modulation scheme has a lower spectral efficiency than the first coding and modulation scheme to extend coverage for the local transmission.

15. The method of claim 12, wherein the first coding and modulation scheme has a lower spectral efficiency than the second coding and modulation scheme.

16. The method of claim 1, further comprising:

processing the data for the wide-area and local transmissions based on the transmission in which the data is sent and data type.

17. The method of claim 1, further comprising:

multiplexing a first pilot onto a third transmission span, the first pilot being suitable for deriving a first channel estimate for the wide-area transmission; and

multiplexing a second pilot onto a fourth transmission span, the second pilot being suitable for deriving a second channel estimate for the local transmission.

18. The method of claim 17, wherein the first and second pilots are each multiplexed onto different sets of frequency subbands in different symbol periods,

19. The method of claim 8, further comprising:

multiplexing a first pilot onto different sets of frequency subbands used for pilot transmission in different symbol periods of the first time segment, the first pilot being suitable for deriving a first channel estimate for the wide-area transmission; and

multiplexing a second pilot onto different sets of frequency subbands used for pilot transmission in different symbol periods of the second time segment, the second pilot being suitable for deriving a second channel estimate for the local transmission.

20. The method of claim 17, further comprising:

generating the second pilot with an orthogonal sequence assigned to the subset of the plurality of transmitters, wherein the second pilot for the subset of the plurality of transmitters is orthogonal to at least one other second pilot for at least one other subset of the plurality of transmitters.

21. The method of claim 17, further comprising:

generating the second pilot with a pseudo-random sequence assigned to the subset of the plurality of transmitters, wherein the second pilot for the subset of the plurality of transmitters is pseudo-random with respect to at least one other second pilot for at least one other subset of the plurality of transmitters.

22. The method of claim 17, further comprising:

multiplying modulation symbols for different frequency subbands with a pseudo-random sequence assigned to the subset of the plurality of transmitters to obtain scaled symbols, wherein the pseudo-random sequence is used for each symbol period; and

multiplying the scaled symbols for different symbol periods with an orthogonal sequence assigned to the subset of the plurality of transmitters to generate the second pilot, wherein the second pilot for the subset of the plurality of transmitters is pseudo-random in frequency and orthogonal in time with respect to at least one other second pilot for at least one other subset of the plurality of transmitters.

23. The method of claim 1, further comprising:

multiplexing overhead information for the wide-area transmission onto a third transmission span; and

multiplexing overhead information for the local transmission onto a fourth transmission span.

24. The method of claim 23, wherein the overhead information for the wide-area transmission indicates frequency and time location of each data channel for the wide-area transmission, and wherein the overhead information for the local transmission indicates frequency and time location of each data channel for the local transmission.

25. The method of claim 1, further comprising:

selecting the first and second transmission spans based on an amount of data to broadcast for the wide-area transmission and an amount of data to broadcast for the local transmission.

26. The method of claim 1, further comprising:

adjusting the first and second transmission spans based on time of day.

27. The method of claim 1, further comprising:

adjusting the first and second transmission spans based on a predetermined schedule.

28. An apparatus in a wireless broadcast network, comprising:

a multiplexer operable to receive and multiplex data for a wide-area transmission onto a first transmission span and to receive and multiplex data for a local transmission onto a second transmission span, the wide-area transmission being sent from a plurality of transmitters in the network, and the local transmission being sent from a subset of the plurality of transmitters; and

a transmitter unit operable to broadcast the local and wide-area transmissions via a wireless link.

29. The apparatus of claim 28, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM), wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

30. The apparatus of claim 28, further comprising:

a first data processor operable to process the data for the wide-area transmission in accordance with a first coding and modulation scheme; and

a second data processor operable to process the data for the local transmission in accordance with a second coding and modulation scheme, and

wherein the multiplexer is operable to multiplex the processed data for the wide-area transmission onto the first transmission span and to multiplex the processed data for the local transmission onto the second transmission span.

31. The apparatus of claim 30, wherein the first data processor is further operable to generate a first pilot suitable for deriving a first channel estimate for the wide-area transmission, wherein the second data processor is further operable to generate a second pilot suitable for deriving a second channel estimate for the local transmission, and wherein the multiplexer is further operable to multiplex the first pilot onto a third transmission span and to multiplex the second pilot onto a fourth transmission span.

32. The apparatus of claim 28, wherein the multiplexer is further operable to multiplex overhead information for the wide-area transmission onto a third transmission span and to multiplex overhead information for the local transmission onto a fourth transmission span.

33. The apparatus of claim 28, further comprising:

a controller operable to select the first and second transmission spans based on an amount of data to broadcast for the wide-area transmission and an amount of data to broadcast for the local transmission.

34. An apparatus in a wireless broadcast network, comprising:

means for multiplexing data for a wide-area transmission onto a first transmission span, the wide-area transmission being sent from a plurality of transmitters in the network;

means for multiplexing data for a local transmission onto a second transmission span, the local transmission being sent from a subset of the plurality of transmitters; and

means for broadcasting the multiplexed data for the local and wide-area transmissions via a link.

35. The apparatus of claim 34, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM), wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

36. The apparatus of claim 34, further comprising:

means for processing the data for the wide-area transmission in accordance with a first coding and modulation scheme, wherein the processed data for the wide-area transmission is multiplexed onto the first transmission span; and

means for processing the data for the local transmission in accordance with a second coding and modulation scheme, wherein the processed data for the local transmission is multiplexed onto the second transmission span.

37. The apparatus of claim 34, further comprising:

means for multiplexing a first pilot onto a third transmission span, the first pilot being suitable for deriving a first channel estimate for the wide-area transmission; and

means for multiplexing a second pilot onto a fourth transmission span, the second pilot being suitable for deriving a second channel estimate for the local transmission.

38. The apparatus of claim 34, further comprising:

means for multiplexing overhead information for the wide-area transmission onto a third transmission span; and

means for multiplexing overhead information for the local transmission onto a fourth transmission span.

39. The apparatus of claim 34, further comprising:

means for selecting the first and second transmission spans based on an amount of data to broadcast for the wide-area transmission and an amount of data to broadcast for the local transmission.

40. A method of receiving data in a wireless broadcast network, comprising:

receiving via a wireless link a broadcast transmission comprised of a wide-area transmission and a local transmission, the wide-area transmission being sent from a plurality of transmitters in the network, and the local transmission being sent from a subset of the plurality of transmitters;

if the wide-area transmission is being received, demultiplexing the data for the wide-area transmission from a first transmission span; and

if the local transmission is being received, demultiplexing the data for the local transmission from a second transmission span.

41. The method of claim 40, wherein the data for the wide-area transmission is frequency division multiplexed (FDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second sets of frequency subbands, respectively, obtained with multi-carrier modulation.

42. The method of claim 40, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second time segments, respectively, of a frame.

43. The method of claim 42, wherein the first time segment for the wide-area transmission is prior to the second time segment for the local transmission.

44. The method of claim 40, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM).

45. The method of claim 44, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

46. The method of claim 40, further comprising:

if the wide-area transmission is being received, processing the data for the wide-area transmission in accordance with a first demodulation and decoding scheme; and

if the local transmission is being received, processing the data for the local transmission in accordance with a second demodulation and decoding scheme.

47. The method of claim 40, further comprising:

if the wide-area transmission is being received, demultiplexing overhead information for the wide-area transmission from a third transmission span; and

if the local transmission is being received, demultiplexing overhead information for the local transmission from a fourth transmission span.

48. The method of claim 47, wherein the overhead information for the wide-area transmission indicates frequency and time location of each data channel for the wide-area transmission, and wherein the overhead information for the local transmission indicates frequency and time location of each data channel for the local transmission.

49. The method of claim 40, further comprising:

if the wide-area transmission is being received,

demultiplexing a first pilot from a third transmission span,

deriving a first channel estimate for the wide-area transmission based on the first pilot, and

processing the data for the wide-area transmission with the first channel estimate.

50. The method of claim 49, further comprising:

if the local transmission is being received,

demultiplexing a second pilot from a fourth transmission span,

deriving a second channel estimate for the local transmission based on the second pilot, and

processing the data for the local transmission with the second channel estimate.

51. The method of claim 50, wherein the first and second channel estimates are respectively associated with first and second impulse response estimates having different lengths.

52. The method of claim 51, further comprising:

performing thresholding to zero out channel taps of the first impulse response estimate that are below a first predetermined threshold; and

performing thresholding to zero out channel taps of the second impulse response estimate that are below a second predetermined threshold.

53. The method of claim 52, wherein the first predetermined threshold is equal to the second predetermined threshold.

54. The method of claim 50, further comprising:

if the wide-area transmission is being received, processing the first pilot with a first set of at least one time-domain filter to derive the first channel estimate; and

if the local transmission is being received, processing the second pilot with a second set of at least one time-domain filter to derive the second channel estimate.

55. The method of claim 54, wherein the first and second sets of at least one time-domain filter have different lengths, different coefficients, or both different lengths and different coefficients.

56. A wireless apparatus in a wireless broadcast network, comprising:

a receiver unit operable to receive via a wireless link a broadcast transmission comprised of a wide-area transmission and a local transmission, the wide-area transmission being sent from a plurality of transmitters in the network, and the local transmission being sent from a subset of the plurality of transmitters; and

a demultiplexer operable to demultiplex data for the wide-area transmission from a first transmission span if the wide-area transmission is being received and to demultiplex data for the local transmission from a second transmission span if the local transmission is being received.

57. The apparatus of claim 56, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM), wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

58. The apparatus of claim 56, further comprising:

a data processor operable to process the data for the wide-area transmission in accordance with a first demodulation and decoding scheme if the wide-area transmission is being received and to process the data for the local transmission in accordance with a second demodulation and decoding scheme if the local transmission is being received.

59. The apparatus of claim 56, wherein the demultiplexer is further operable to demultiplex overhead information for the wide-area transmission from a third transmission span if the wide-area transmission is being received and to demultiplex overhead information for the local transmission from a fourth transmission span if the local transmission is being received.

60. The apparatus of claim 56, further comprising:

a channel estimator operable to derive a first channel estimate for the wide-area transmission based on a first pilot demultiplexed from a third transmission span if the wide-area transmission is being received and to derive a second channel estimate for the local transmission based on a second pilot demultiplexed from a fourth transmission span if the local transmission is being received; and

a demodulator operable to process the data for the wide-area transmission with the first channel estimate if the wide-area transmission is being received and to process the data for the local transmission with the second channel estimate if the local transmission is being received.

61. The apparatus of claim 56, wherein the receiver unit is operable to receive both the wide-area transmission and the local transmission concurrently by tuning to a single radio frequency.

62. A wireless apparatus in a wireless broadcast network, comprising:

means for receiving via a wireless link a broadcast transmission comprised of a wide-area transmission and a local transmission, the wide-area transmission being sent from a plurality of transmitters in the network, and the local transmission being sent from a subset of the plurality of transmitters;

means for demultiplexing the data for the wide-area transmission from a first transmission span if the wide-area transmission is being received; and

means for demultiplexing the data for the local transmission from a second transmission span if the local transmission is being received.

63. The apparatus of claim 62, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM), wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

64. The apparatus of claim 62, further comprising:

means for processing the data for the wide-area transmission in accordance with a first demodulation and decoding scheme if the wide-area transmission is being received; and

means for processing the data for the local transmission in accordance with a second demodulation and decoding scheme if the local transmission is being received.

65. The apparatus of claim 62, further comprising:

means for demultiplexing overhead information for the wide-area transmission from a third transmission span if the wide-area transmission is being received; and

means for demultiplexing overhead information for the local transmission from a fourth transmission span if the local transmission is being received.

66. The apparatus of claim 62, further comprising:

means for demultiplexing a first pilot from a third transmission span if the wide-area transmission is being received;

means for demultiplexing a second pilot from a fourth transmission span if the local transmission is being received;

means for deriving a first channel estimate for the wide-area transmission based on the first pilot if the wide-area transmission is being received;

means for deriving a second channel estimate for the local transmission based on the second pilot if the local transmission is being received;

means for processing the data for the wide-area transmission with the first channel estimate if the wide-area transmission is being received; and

means for processing the data for the local transmission with the second channel estimate if the local transmission is being received.

67. A computer readable storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:

multiplexing data for a wide-area transmission onto a first transmission span, the wide-area transmission being sent from a plurality of transmitters in the network;

multiplexing data for a local transmission onto a second transmission span, the local transmission being sent from a subset of the plurality of transmitters; and

broadcasting the local and wide-area transmissions via a wireless link.

68. The computer readable storage medium encoded with a computer program of claim 67, wherein different local transmissions are sent from different subsets of the plurality of transmitters.

69. The computer readable storage medium encoded with a computer program of claim 67, wherein different wide-area transmissions are sent from different pluralities of transmitters.

70. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

multiplexing data for venue transmission onto a third transmission span, the venue transmission being sent from a smaller subset of the subset of the plurality of transmitters.

71. The computer readable storage medium encoded with a computer program of claim 67, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second time segments, respectively, of a frame of a predetermined time duration.

72. The computer readable storage medium encoded with a computer program of claim 67, wherein the data for the wide-area transmission is frequency division multiplexed (FDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second sets of frequency subbands, respectively, obtained with multi-carrier modulation.

73. The computer readable storage medium encoded with a computer program of claim 67, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM).

74. The computer readable storage medium encoded with a computer program of claim 73, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

75. The computer readable storage medium encoded with a computer program of claim 74, wherein the data for the local transmission is multiplexed onto fewer than all usable frequency subbands to reduce interference.

76. The computer readable storage medium encoded with a computer program of claim 75, wherein the data for the local transmission from the subset of the plurality of transmitters is multiplexed onto frequency subbands that are orthogonal to frequency subbands used by at least one other subset of the plurality of transmitters.

77. The computer readable storage medium encoded with a computer program of claim 75, wherein the data for the local transmission is multiplexed onto frequency subbands pseudo-randomly selected from among all usable frequency subbands.

78. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

processing the data for the wide-area transmission in accordance with a first coding and modulation scheme, wherein the processed data for the wide-area transmission is multiplexed onto the first transmission span; and

processing the data for the local transmission in accordance with a second coding and modulation scheme, wherein the processed data for the local transmission is multiplexed onto the second transmission span.

79. The computer readable storage medium encoded with a computer program of claim 78, wherein the first and second coding and modulation schemes are selected based on desired coverage for the wide-area and local transmissions, respectively.

80. The computer readable storage medium encoded with a computer program of claim 78, wherein the second coding and modulation scheme has a lower spectral efficiency than the first coding and modulation scheme to extend coverage for the local transmission.

81. The computer readable storage medium encoded with a computer program of claim 78, wherein the first coding and modulation scheme has a lower spectral efficiency than the second coding and modulation scheme.

82. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

processing the data for the wide-area and local transmissions based on the transmission in which the data is sent and data type.

83. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

multiplexing a first pilot onto a third transmission span, the first pilot being suitable for deriving a first channel estimate for the wide-area transmission; and

multiplexing a second pilot onto a fourth transmission span, the second pilot being suitable for deriving a second channel estimate for the local transmission.

84. The computer readable storage medium encoded with a computer program of claim 83, wherein the first and second pilots are each multiplexed onto different sets of frequency subbands in different symbol periods.

85. The computer readable storage medium encoded with a computer program of claim 74, further comprising:

multiplexing a first pilot onto different sets of frequency subbands used for pilot transmission in different symbol periods of the first time segment, the first pilot being suitable for deriving a first channel estimate for the wide-area transmission; and

multiplexing a second pilot onto different sets of frequency subbands used for pilot transmission in different symbol periods of the second time segment, the second pilot being suitable for deriving a second channel estimate for the local transmission.

86. The computer readable storage medium encoded with a computer program of claim 83, further comprising:

generating the second pilot with an orthogonal sequence assigned to the subset of the plurality of transmitters, wherein the second pilot for the subset of the plurality of transmitters is orthogonal to at least one other second pilot for at least one other subset of the plurality of transmitters.

87. The computer readable storage medium encoded with a computer program of claim 83, further comprising:

generating the second pilot with a pseudo-random sequence assigned to the subset of the plurality of transmitters, wherein the second pilot for the subset of the plurality of transmitters is pseudo-random with respect to at least one other second pilot for at least one other subset of the plurality of transmitters.

88. The computer readable storage medium encoded with a computer program of claim 83, further comprising:

multiplying modulation symbols for different frequency subbands with a pseudo-random sequence assigned to the subset of the plurality of transmitters to obtain scaled symbols, wherein the pseudo-random sequence is used for each symbol period; and

multiplying the scaled symbols for different symbol periods with an orthogonal sequence assigned to the subset of the plurality of transmitters to generate the second pilot, wherein the second pilot for the subset of the plurality of transmitters is pseudo-random in frequency and orthogonal in time with respect to at least one other second pilot for at least one other subset of the plurality of transmitters.

89. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

multiplexing overhead information for the wide-area transmission onto a third transmission span; and

multiplexing overhead information for the local transmission onto a fourth transmission span.

90. The computer readable storage medium encoded with a computer program of claim 89, wherein the overhead information for the wide-area transmission indicates frequency and time location of each data channel for the wide-area transmission, and wherein the overhead information for the local transmission indicates frequency and time location of each data channel for the local transmission.

91. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

selecting the first and second transmission spans based on an amount of data to broadcast for the wide-area transmission and an amount of data to broadcast for the local transmission.

92. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

adjusting the first and second transmission spans based on time of day.

93. The computer readable storage medium encoded with a computer program of claim 67, further comprising:

adjusting the first and second transmission spans based on a predetermined schedule.

94. A computer readable storage medium encoded with a computer program, the program comprising instructions that when executed by data processing apparatus cause the data processing apparatus to perform operations comprising:

receiving via a wireless link a broadcast transmission comprised of a wide-area transmission and a local transmission, the wide-area transmission being sent from a plurality of transmitters in the network, and the local transmission being sent from a subset of the plurality of transmitters;

when the wide-area transmission is being received, demultiplexing the data for the wide-area transmission from a first transmission span; and

when the local transmission is being received, demultiplexing the data for the local transmission from a second transmission span.

95. The computer readable storage medium encoded with a computer program of claim 94, wherein the data for the wide-area transmission is frequency division multiplexed (FDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second sets of frequency subbands, respectively, obtained with multi-carrier modulation.

96. The computer readable storage medium encoded with a computer program of claim 94, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, and wherein the first and second transmission spans are first and second time segments, respectively, of a frame.

97. The computer readable storage medium encoded with a computer program of claim 96, wherein the first time segment for the wide-area transmission is prior to the second time segment for the local transmission.

98. The computer readable storage medium encoded with a computer program of claim 94, wherein the wireless broadcast network utilizes orthogonal frequency division multiplexing (OFDM).

99. The computer readable storage medium encoded with a computer program of claim 98, wherein the data for the wide-area transmission is time division multiplexed (TDM) with the data for the local transmission, wherein the first transmission span includes all frequency subbands usable for data transmission in a first time segment of a frame, and wherein the second transmission span includes all frequency subbands usable for data transmission in a second time segment of the frame.

100. The computer readable storage medium encoded with a computer program of claim 94, further comprising:

when the wide-area transmission is being received, processing the data for the wide-area transmission in accordance with a first demodulation and decoding scheme; and

when the local transmission is being received, processing the data for the local transmission in accordance with a second demodulation and decoding scheme.

101. The computer readable storage medium encoded with a computer program of claim 94, further comprising:

when the wide-area transmission is being received, demultiplexing overhead information for the wide-area transmission from a third transmission span; and

when the local transmission is being received, demultiplexing overhead information for the local transmission from a fourth transmission span.

102. The computer readable storage medium encoded with a computer program of claim 101, wherein the overhead information for the wide-area transmission indicates frequency and time location of each data channel for the wide-area transmission, and wherein the overhead information for the local transmission indicates frequency and time location of each data channel for the local transmission.

103. The computer readable storage medium encoded with a computer program of claim 94, further comprising:

when the wide-area transmission is being received,

demultiplexing a first pilot from a third transmission span,

deriving a first channel estimate for the wide-area transmission based on the first pilot, and

processing the data for the wide-area transmission with the first channel estimate.

104. The computer readable storage medium encoded with a computer program of claim 103, further comprising:

when the local transmission is being received,

demultiplexing a second pilot from a fourth transmission span,

deriving a second channel estimate for the local transmission based on the second pilot, and

processing the data for the local transmission with the second channel estimate.

105. The computer readable storage medium encoded with a computer program of claim 104, wherein the first and second channel estimates are respectively associated with first and second impulse response estimates having different lengths.

106. The computer readable storage medium encoded with a computer program of claim 105, further comprising:

performing thresholding to zero out channel taps of the first impulse response estimate that are below a first predetermined threshold; and

performing thresholding to zero out channel taps of the second impulse response estimate that are below a second predetermined threshold.

107. The computer readable storage medium encoded with a computer program of claim 106, wherein the first predetermined threshold is equal to the second predetermined threshold.

108. The computer readable storage medium encoded with a computer program of claim 104, further comprising:

when the wide-area transmission is being received, processing the first pilot with a first set of at least one time-domain filter to derive the first channel estimate; and

when the local transmission is being received, processing the second pilot with a second set of at least one time-domain filter to derive the second channel estimate.

109. The computer readable storage medium encoded with a computer program of claim 108, wherein the first and second sets of at least one time-domain filter have different lengths, different coefficients, or both different lengths and different coefficients.