1. A method of operating a network node in a communication network, the method comprising:', 'determining (121) a preferred configuration for one or more flexible subframes in a frame, the frame comprising one or more subframes allocated to uplink transmissions, one or more subframes allocated to downlink transmissions and one or more flexible subframes that can each be dynamically allocated to either uplink transmissions or downlink transmissions; and', 'transmitting (125) a message to a neighbouring network node in the communication network through an inter node interface, the message indicating the preferred configuration for the one or more flexible subframes.

2. A method as in claim 1 , the method further comprising:', 'adopting (127) the preferred configuration of the one or more flexible subframes after the message is sent to the neighbouring network node and using the preferred configuration in communications with mobile devices.

3. A method as in claim 1 or 2, the method further comprising:', 'receiving (133) a message from the neighbouring network node through the inter node interface indicating a preferred configuration of the neighbouring network node for the one or more flexible subframes in the frame; and', 'determining (135) the configuration of the one or more flexible subframes in the frame using the preferred configuration indicated in the received message and the preferred configuration of the network node.

4. A method as in claim 3, the method further comprising:', 'using (127) the determined configuration in communications with mobile devices once the configuration has been determined.

5. A method as in any of claims 1-4, wherein the message indicating the preferred configuration for the one or more flexible subframes is sent via an X2 interface between the network nodes.

6. A method as in any of claims 1-5, wherein the message comprises an information element, IE, that has a set of predefined values each corresponding to a respective

configuration of the subframes in the frame, and the network node selects a predefined value for the IE corresponding to the preferred configuration for the one or more flexible subframes.

7. A method as in any of claims 1-5, wherein multiple information elements, lEs, in the message are used to indicate the flexible subframe configuration.

8. A method as in any of claims 1-5, wherein the message indicating the preferred configuration for the one or more flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment information element, IE, and wherein the subframes for which the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

9. A method as in any of claims 1-5, wherein the message indicating the preferred configuration for the one or more flexible subframes is included in a message that is used to transfer load and interference co-ordination information between network nodes

10. A method as in claim 9, wherein the message is a LOAD INFORMATION message.1. A method as in claim 9 or 10, wherein the message includes an information element, IE, indicating the uplink or downlink configuration for each of the one or more flexible subframes

12. A method as in claim 9 or 10, wherein the message includes two information elements, lEs, with the first IE indicating which subframes in the frame are flexible subframes, and the second IE indicating the uplink or downlink configuration for the indicated flexible subframes

13. A method as in claim 12, wherein the first IE indicating which subframes in the frame are flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment IE, and wherein the subframes for which the different one of the uplink/downlink configuration

differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes

14. A method as in any of claims 1-13, where the message indicating the preferred configuration for the one or more flexible subframes further comprises information on the interference level experienced by the network node that transmits the message

15. A method as in claim 14, wherein information on the interference level is provided for each subframe and/or resource block

16. A method as in claim 15, wherein the information on the interference level is included in an information element, IE, in a LOAD INFORMATION message

17. A method as in claim 14, wherein the message is a LOAD INFORMATION message and comprises an UL Interference Overload Indication IE that provides interference levels experienced by the network node on a per resource block basis

18. A method as in claim 17, wherein the message further comprises information representing the level of interference experienced by the network node in the cell on a subframe and resource block basis

19. A method as in any of claims 1-18, the method further comprising:', 'receiving a message from the neighbouring network node through the inter node interface, the message indicating information on the interference level experienced by the neighbouring network node; and', 'determining the configuration of the one or more flexible subframes in the frame using the information on the interference level and the preferred configuration of the network node.

20. A method as in any of claims 1-19, further comprising sending information to the neighbouring network node on the traffic demand in the uplink to the network node and/or the downlink from the network node.

21. A method as in any of claims 1-20, wherein the message indicating the preferred configuration for the one or more flexible subframes further comprises information on

the transmission power that is going to be used in the frame and/or a maximum transmission power than can be used in the frame.

22. A method as in claim 21 , wherein the information on the actual and/or maximum transmission power is provided for particular subframes.

23. A method as in claim 21 , wherein the information on the actual and/or maximum transmission power is provided per physical resource block and/or per subframe in the frame.

24. A method as in any of claims 21-23, wherein the information on the actual and/or maximum transmission power is included in a relative narrowband transmit power, RNTP, information element, IE, that is adapted to include information on time resources.

25. A method as in any of claims 21-23, wherein the information on the actual and/or maximum transmission power is included in an information element, IE, in a LOAD INFORMATION message.

26. A method as in any of claims 1-25 the method further comprising:', 'receiving a message from the neighbouring network node through the inter node interface, the message indicating information on the transmission power that is going to be used in the frame and/or a maximum transmission power than can be used in the frame; and', 'determining the configuration of the one or more flexible subframes in the frame using the information on the transmission power and/or maximum transmission power and the preferred configuration of the network node.

27. A method as in any of claims 1-26, wherein the communication network is a Long Term Evolution, LTE, time division duplex, TDD network.

28. A computer program product having computer readable code embodied therein, the computer readable code being such that, on execution by a suitable computer or processor, the computer or processor performs the method of any of claims 1-27.

29. A network node (10) for use in a communication network (2), the network node (10) being adapted to:', 'determine a preferred configuration for one or more flexible subframes in a frame, the frame comprising one or more subframes allocated to uplink transmissions, one or more subframes allocated to downlink transmissions and one or more flexible subframes that can each be dynamically allocated to either uplink transmissions or downlink transmissions and to form a message indicating the preferred configuration for the one or more flexible subframes; and', 'transmit the message to a neighbouring network node (12) in the communication network (2) through an inter node interface.

30. A network node (10) as in claim 29, the network node (10) being further adapted to:', 'adopt the preferred configuration of the one or more flexible subframes after the message is sent to the neighbouring network node (12) and using the preferred configuration in communications with mobile devices (16).

31. A network node (10) as in claim 29 or 30, the network node (10) being further adapted to:', 'receive a message from the neighbouring network node (12) through the inter node interface indicating a preferred configuration of the neighbouring network node (12) for the one or more flexible subframes in the frame; and', 'determine the configuration of the one or more flexible subframes in the frame using the preferred configuration indicated in the received message and the preferred configuration of the network node (10).

32. A network node (10) as in claim 31 , the network node (10) being further adapted to:', 'use the determined configuration in communications with mobile devices (16) once the configuration has been determined.

33 A network node (10) as in any of claims 29-32, wherein the network node (10) is adapted to send the message indicating the preferred configuration for the one or more flexible subframes via an X2 interface between the network nodes (10, 12).

34. A network node (10) as in any of claims 29-33, wherein the message comprises an information element, IE, that has a set of predefined values each corresponding to a respective configuration of the subframes in the frame, and the network node (10) is adapted to select a predefined value for the IE corresponding to the preferred configuration for the one or more flexible subframes.

35. A network node (10) as in any of claims 29-33, wherein the network node (10) is adapted to use multiple information elements, lEs, in the message to indicate the flexible subframe configuration.

36. A network node (10) as in any of claims 29-33, wherein the network node (10) is adapted to indicate the preferred configuration for the one or more flexible subframes by signalling a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment information element, IE, and wherein the subframes for which the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

37. A network node (10) as in any of claims 29-33, wherein the network node (10) is adapted to indicate the preferred configuration for the one or more flexible subframes in a message that is used to transfer load and interference co-ordination information between network nodes.

38. A network node (10) as in claim 37, wherein the message is a LOAD INFORMATION message.

39. A network node (10) as in claim 37 or 38, wherein the network node (10) is adapted to include an information element, IE, in the message indicating the uplink or downlink configuration for each of the one or more flexible subframes.

40. A network node (10) as in claim 37 or 38, wherein the network node (10) is adapted to include two information elements, lEs, in the message with the first IE indicating which subframes in the frame are flexible subframes, and the second IE indicating the uplink or downlink configuration for the indicated flexible subframes.

41. A network node (10) as in claim 40, wherein the network node (10) is adapted to use the first IE to signal a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment IE, and wherein the subframes for which the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

42. A network node (10) as in any of claims 29-41 , where the network node (10) is further adapted to transmit the message indicating the preferred configuration for the one or more flexible subframes with information on the interference level experienced by the network node (10) that transmits the message.

43. A network node (10) as in claim 42, wherein information on the interference level is provided for each subframe and/or resource block.

44. A network node (10) as in claim 43, wherein the network node (10) is adapted to include the information on the interference level in an information element, IE, in a LOAD INFORMATION message.

45. A network node (10) as in claim 42, wherein the message is a LOAD INFORMATION message and comprises an UL Interference Overload Indication IE that provides interference levels experienced by the network node (10) on a per resource block basis.

46. A network node (10) as in claim 45, wherein the network node (10) is adapted to include in the message information representing the level of interference experienced by the network node (10) in the cell on a subframe and resource block basis.

47. A network node (10) as in any of claims 421-46, the network node (10) being further adapted to:', 'receive a message from the neighbouring network node (12) through the inter node interface, the message indicating information on the interference level experienced by the neighbouring network node (12); and', 'determine the configuration of the one or more flexible subframes in the frame using the information on the interference level and the preferred configuration of the network node (10).

48. A network node (10) as in any of claims 29-47, wherein the network node (10) is further adapted to send information to the neighbouring network node (12) on the traffic demand in the uplink to the network node and/or the downlink from the network node (10).

49. A network node (10) as in any of claims 29-48, wherein the network node (10) is further adapted to include information on the transmission power that is going to be used in the frame and/or a maximum transmission power than can be used in the frame in the message.

50. A network node (10) as in claim 49, wherein the network node (10) is adapted to provide information on the actual and/or maximum transmission power for particular subframes.

51. A network node (10) as in claim 49, wherein the network node (10) is adapted to provide information on the actual and/or maximum transmission power per physical resource block and/or per subframe in the frame.

52. A network node (10) as in any of claims 49-51 , wherein the network node (10) is adapted to include the information on the actual and/or maximum transmission power in a relative narrowband transmit power, RNTP, information element, IE, that is adapted to include information on time resources.

53. A network node (10) as in any of claims 48-50, wherein the network node (10) is adapted to include the information on the actual and/or maximum transmission power in an information element, IE, in a LOAD INFORMATION message.

54. A network node (10) as in any of claims 49-51 the network node (10) further adapted to:', 'receive a message from the neighbouring network node (12) through the inter node interface, the message indicating information on the transmission power that is going to be used in the frame and/or a maximum transmission power than can be used in the frame; and

determine the configuration of the one or more flexible subframes in the frame using the information on the transmission power and/or maximum transmission power and the preferred configuration of the network node (10).

55. A network node (10) as in any of claims 29-54, wherein the communication network is a Long Term Evolution, LTE, time division duplex, TDD network.

56. A method of operating a network node in a communication network, the method comprising:', 'receiving (133) a message from a neighbouring network node in the communication network through an inter node interface, the message indicating a preferred configuration of the neighbouring network node for one or more flexible subframes in a frame, the frame comprising one or more subframes allocated to uplink transmissions, one or more subframes allocated to downlink transmissions and one or more flexible subframes that can each be dynamically allocated to either uplink transmissions or downlink transmissions; and', 'determining (135) the configuration of the one or more flexible subframes in the frame using the preferred configuration indicated in the received message.

57. A method as in claim 56, the method further comprising the step of:', 'using the determined configuration in communications with mobile devices.

58. A method as in claim 56 or 57, the method further comprising the step of:', 'determining (131) a preferred configuration for the one or more flexible subframes in the frame; and', 'wherein the step of determining the configuration of the one or more flexible subframes comprises using the preferred configuration of the network node and the preferred configuration of the neighbouring network node indicated in the received message.

59. A method as in any of claims 56-58, wherein the message indicating the preferred configuration for the one or more flexible subframes is received via an X2 interface between the network nodes.

60. A method as in any of claims 56-59, wherein the message comprises an information element, IE, that has a set of predefined values each corresponding to a

respective configuration of the subframes in the frame, and the message indicates one of predefined values for the IE corresponding to the preferred configuration of the neighbouring network node for the one or more flexible subframes.

61. A method as in any of claims 56-59, wherein multiple information elements, lEs, in the message are used to indicate the flexible subframe configuration.

62. A method as in any of claims 56-59, wherein the message indicating the preferred configuration for the one or more flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment information element, IE, and wherein the subframes for which the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

63. A method as in any of claims 56-59, wherein the message indicating the preferred configuration for the one or more flexible subframes is included in a message that is used to transfer load and interference co-ordination information between network nodes.

64. A method as in claim 63, wherein the message is a LOAD INFORMATION message.

65. A method as in claim 63 or 64, wherein the message includes an information element, IE, indicating the uplink or downlink configuration for each of the one or more flexible subframes.

66. A method as in claim 63 or 64, wherein the message includes two information elements, lEs, with the first IE indicating which subframes in the frame are flexible subframes, and the second IE indicating the uplink or downlink configuration for the indicated flexible subframes.

67. A method as in claim 66, wherein the first IE indicating which subframes in the frame are flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment IE, and wherein the subframes for which the different one of the uplink/downlink configuration

differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

68. A method as in any of claims 56-67, where the message indicating the preferred configuration for the one or more flexible subframes further comprises information on the interference level experienced by the network node that transmits the message.

69. A method as in claim 68, wherein information on the interference level is provided for each subframe and/or resource block.

70. A method as in claim 69, wherein the information on the interference level is included in an information element, IE, in a LOAD INFORMATION message.

71. A method as in claim 68, wherein the message is a LOAD INFORMATION message and comprises an UL Interference Overload Indication IE that provides interference levels experienced by the neighbouring network node on a per resource block basis.

72. A method as in claim 71 , wherein the message further comprises information representing the level of interference experienced by the neighbouring network node in the cell on a subframe and resource block basis.

73. A method as in any of claims 68-72, wherein the step of determining (135) the configuration of the one or more flexible subframes in the frame uses the preferred configuration indicated in the received message and the received information on the interference level.

74. A method as in any of claims 56-73, the method further comprising the step of: receiving information from the neighbouring network node on the traffic demand in the uplink to the neighbouring network node and/or the downlink from the neighbouring network node.

75. A method as in any of claims 56-74, wherein the received message indicating the preferred configuration of the neighbouring network node for the one or more flexible subframes further comprises information on the transmission power that is going to be

used in the frame and/or a maximum transmission power than can be used in the frame.

76. A method as in claim 75, wherein the information on the actual and/or maximum transmission power is provided for particular subframes.

77. A method as in claim 75, wherein the information on the actual and/or maximum transmission power is provided per physical resource block and/or per subframe in the frame.

78. A method as in any of claims 75-77, wherein the information on the actual and/or maximum transmission power is included in a relative narrowband transmit power, RNTP, information element, IE, that is adapted to include information on time resources.

79. A method as in any of claims 75-78, wherein the information on the actual and/or maximum transmission power is included in an information element, IE, in a LOAD INFORMATION message.

80. A method as in any of claims 75-79 further comprising the step of', 'determining the configuration of the one or more flexible subframes in the frame using the received information on the transmission power and/or maximum transmission power and the preferred configuration of the neighbouring network node.

81. A method as in any of claims 56-80, wherein the communication network is a Long Term Evolution, LTE, time division duplex, TDD network.

82. A computer program product having computer readable code embodied therein, the computer readable code being such that, on execution by a suitable computer or processor, the computer or processor performs the method of any of claims 56-81.

83. A network node (10) for use in a communication network (2), the network node (10) being adapted to:', 'receive a message from a neighbouring network node (12) in the communication network (2) through an inter node interface, the message indicating a preferred configuration of the neighbouring network node (12) for one or more flexible subframes

in a frame, the frame comprising one or more subframes allocated to uplink transmissions, one or more subframes allocated to downlink transmissions and one or more flexible subframes that can each be dynamically allocated to either uplink transmissions or downlink transmissions; and', 'determine the configuration of the one or more flexible subframes in the frame using the preferred configuration indicated in the received message.

84. A network node (10) as in claim 83, the network node being (10) further adapted to:', 'use the determined configuration in communications with mobile devices (16).

85. A network node (10) as in claim 83 or 84, the network node (10) being further adapted to:', 'determine a preferred configuration for the one or more flexible subframes in the frame;', 'wherein the determination of the configuration of the one or more flexible subframes uses the preferred configuration of the network node (10) and the preferred configuration of the neighbouring network node (12) indicated in the received message.

86. A network node (10) as in any of claims 83-85, wherein the message indicating the preferred configuration for the one or more flexible subframes is received via an X2 interface between the network nodes (10, 12).

87. A network node (10) as in any of claims 83-86, wherein the message comprises an information element, IE, that has a set of predefined values each corresponding to a respective configuration of the subframes in the frame, and the message indicates one of predefined values for the IE corresponding to the preferred configuration of the neighbouring network node for the one or more flexible subframes.

88. A network node (10) as in any of claims 83-86, wherein multiple information elements, lEs, in the message are used to indicate the flexible subframe configuration.

89. A network node (10) as in any of claims 83-86, wherein the message indicating the preferred configuration for the one or more flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment information element, IE, and wherein the subframes for which

the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

90. A network node (10) as in any of claims 83-86, wherein the message indicating the preferred configuration for the one or more flexible subframes is included in a message that is used to transfer load and interference co-ordination information between network nodes.

91. A network node (10) as in claim 90, wherein the message is a LOAD INFORMATION message.

92. A network node (10) as in claim 90 or 91 , wherein the message includes an information element, IE, indicating the uplink or downlink configuration for each of the one or more flexible subframes.

93. A network node (10) as in claim 90 or 91 , wherein the message includes two information elements, lEs, with the first IE indicating which subframes in the frame are flexible subframes, and the second IE indicating the uplink or downlink configuration for the indicated flexible subframes.

94. A network node (10) as in claim 93, wherein the first IE indicating which subframes in the frame are flexible subframes signals a different one of an uplink/downlink time division duplex, TDD, configuration to that contained in a Subframe Assignment IE, and wherein the subframes for which the different one of the uplink/downlink configuration differs with respect to the configuration contained in the Subframe Assignment IE are the flexible subframes.

95. A network node (10) as in any of claims 83-94, where the message indicating the preferred configuration for the one or more flexible subframes further comprises information on the interference level experienced by the network node (12) that transmits the message.

96. A network node (10) as in claim 95, wherein information on the interference level is provided for each subframe and/or resource block.

97. A network node (10) as in claim 96, wherein the information on the interference level is included in an information element, IE, in a LOAD INFORMATION message.

98. A network node (10) as in claim 95, wherein the message is a LOAD INFORMATION message and comprises an UL Interference Overload Indication IE that provides interference levels experienced by the neighbouring network node (12) on a per resource block basis.

99. A network node (10) as in claim 98, wherein the message further comprises information representing the level of interference experienced by the neighbouring network node (12) in the cell on a subframe and resource block basis.100. A network node (10) as in any of claims 85-99, adapted such that the determination of the configuration of the one or more flexible subframes in the frame uses the preferred configuration indicated in the received message and the received information on the interference level.101. A network node (10) as in any of claims 83-100, the network node further adapted to', 'receive information from the neighbouring network node (12) on the traffic demand in the uplink to the neighbouring network node (12) and/or the downlink from the neighbouring network node (12).102. A network node (10) as in any of claims 83-101 , wherein the network node (10) is further adapted to receive information on the transmission power that is going to be used in the frame and/or a maximum transmission power than can be used in the frame in the message.103. A network node (10) as in claim 102, wherein the network node (10) is adapted to receive information on the actual and/or maximum transmission power for particular subframes.104. A network node (10) as in claim 102, wherein the network node (10) is adapted to receive information on the actual and/or maximum transmission power per physical resource and/or per subframe block in the frame.105. A network node (10) as in any of claims 102-104, wherein the network node (10) is adapted to receive the information on the actual and/or maximum transmission power in a relative narrowband transmit power, RNTP, information element, IE, that is adapted to include information on time resources.106. A network node (10) as in any of claims 102-105, wherein the network node (10) is adapted to receive the information on the actual and/or maximum transmission power in an information element, IE, in a LOAD INFORMATION message.107. A network node (10) as in any of claims 102-106 further adapted to:', 'determine the configuration of the one or more flexible subframes in the frame using the received information on the transmission power and/or maximum transmission power and the preferred configuration of the neighbouring network node (12).108. A network node (10) as in any of claims 83-107, wherein the communication network (2) is a Long Term Evolution, LTE, time division duplex, TDD network.']