COMMUNICATION DEVICE AND METHOD FOR SYNCHRONISATION

• US 20110176534A1
• Filed: 10/21/2008
• Published: 07/21/2011
• Est. Priority Date: 10/23/2007
• Status: Abandoned Application

• Current Assignee: Agency For Science Technology and Research
• Original Assignee: Agency For Science Technology and Research
• Inventors: Subramanian, Ananth, Chin, Po Shin Francois, Peng, Xiaoming
• Application Number:
  US12/739,350
• Publication Number:
  US 20110176534A1
• Time in Patent Office: Days
• US Class Current: 370/350
• CPC Class Codes: H04J 3/0685 Clock or time synchronisation in a node; Intranode synchronisation
• CPC Class Codes: H04L 7/08 the synchronisation signals recurring cyclically
• CPC Class Codes: H04W 56/002 Mutual synchronization

Abstract

A communication device is provided, the communication device comprising a receiving circuit configured to receive a message from another communication device; a time base circuit providing a time base signal that specifies a plurality of time periods; a determining circuit configured to determine, based on an expected reception time of the message and a reception time of the message, a parameter value characterizing a time base offset between the communication device and the other communication device; an offset generating circuit configured to generate a time period offset value specifying a time offset from a point in time, the time period offset value corresponding to a number of time periods from the plurality of time periods, wherein the number of time periods is determined according to the parameter value.

Claims

1-66. -66. (canceled)

67. A communication device comprising:

a receiving circuit configured to receive a message from another communication device;

a time base circuit providing a time base signal that specifies a plurality of time periods;

a determining circuit configured to determine, based on an expected reception time of the message and a reception time of the message, a parameter value characterizing a time base offset between the communication device and the other communication device;

an offset generating circuit configured to generate a time period offset value specifying a time offset from a point in time, the time period offset value corresponding to a number of time periods from the plurality of time periods, wherein the number of time periods is determined according to the parameter value;

wherein the time base signal is a periodic time base signal; and

wherein the parameter value also characterizes the difference of the periodicity of the time base signal and the periodicity of the time base signal of the other communication device.

68. The communication device according to claim 67, wherein the message is a message of a plurality of messages transmitted periodically.

69. The communication device according to claim 67, wherein the parameter value characterizes a difference between the time base signal and a time base signal of the other communication device.

70. The communication device according to claim 67, wherein, if the parameter specifies that the time base signal is ahead of the time base signal of the other communication device, the number of time periods for the time offset is determined to be lower than the number of time periods given by the time base signal.

71. The communication device according to claim 67, wherein the time base signal is a clock signal.

72. The communication device according to claim 71, wherein the clock signal is provided by a physical quartz crystal.

73. The communication device according to claim 71, wherein the communication device receives from the other communication device a periodic message being transmitted with reference to a transmission time point determined based on a time base signal of the other communication device.

74. The communication device according to claim 73, wherein the time point is the Beacon Period Start Time of the other communication device or the Beacon Period Start Time of the communication device.

75. The communication device according to claim 73, wherein the periodicity of the periodic message the communication device receives does not change for a fixed time period and the periodicity refers to a period length.

76. The communication device according to claim 75, wherein the periodic message is a beacon, the period length is a superframe duration of the other communication device in accordance with the time base signal of the other communication device, and the fixed time period is the duration of two superframes in accordance with the time base signal of the other communication device.

77. The communication device according to claim 75, wherein the communication device estimates the clock period or the time base signal of the other communication device with reference to the time base signal or the clock period of the communication device during the fixed time period.

78. The communication device according to claim 77, wherein the clock period C_D of the other communication device is estimated to be C_D=(Y′

−

Y)/(p+m(n₂−

n₁)), wherein Y is the reception time of a beacon from the other communication device at superframe N;

Y′

is the reception time of a beacon from the other communication device at superframe N+1;

p is the number of clock periods during a superframe duration for the communication device;

m is the number of clock periods during a beacon period for the communication device;

n₂ is the beacon slot number of the beacon from the other communication device in superframe N+1; and

n₁ is the beacon slot number of the beacon from the other communication device in superframe N.

79. The communication device according to claim 77 wherein the communication device assumes its clock period to be 1/528 microseconds, or 1/66 microseconds, or 1/F seconds, wherein F is the frequency of the physical clock crystal used by the communication device.

80. The communication device according to claim 75, wherein the communication device determines the Beacon Period Start Time of the other communication device to be B_D=Y−

(n₁−

1)C_Dm=Y−

(n₁−

1)(Y′

−

Y)m/(p+m(n₂−

n₁)), wherein Y is the reception time of a beacon from the other communication device at superframe N;

Y′

is the reception time of a beacon from the other communication device at superframe N+1;

p is the number of clock periods during a superframe duration for the communication device;

m is the number of clock periods during a beacon period for the communication device;

n₂ is the beacon slot number of the beacon from the other communication device in superframe N+1; and

n₁ is the beacon slot number of the beacon from the other communication device in superframe N;

C_D is the clock period of the other communication device with reference to the clock period of the communication device.

81. The communication device according to claim 75 wherein the communication device determines that the number of clock periods the other communication device counts in accordance with the time base signal of the other communication device during the period length of the periodic message is F times 0.065536 clock cycles wherein F is the frequency of the physical clock crystal used by the device.

82. The communication device according to claim 75 wherein the communication device determines the number of clock periods given by a physical clock of the communication device in accordance with the time base signal during the period length of the periodic message.

83. The communication device according to claim 75 wherein the communication device sets up a virtual clock cycle counter at the end of the fixed time period and initializes the virtual clock cycle counter to be zero at the end of the fixed time period.

84. The communication device according to claim 83, wherein the device updates the virtual clock cycle counter after it is initialized to zero such that the virtual clock cycle counter is obtained from the number of physical clock cycles given by a physical clock since the end of the fixed time period or since the initialization of the virtual clock cycle counter to zero by subtracting one clock cycle from the number of physical clock cycles every Floor[P/(P−

Q)] or Round[P/(P−

Q)] of physical clock cycles if P is greater than Q, wherein P is the number of clock cycles given by the physical clock of the communication device in accordance with the time base signal during the period length of the message, and wherein Q is the number of clock cycles given by the physical clock of the other communication device in accordance with the time base signal of the other communication device during the period length of the message.

85. The communication device according to claim 83, wherein the communication device sets its virtual clock to be the same as a physical clock of the communication device if P is less than or equal to Q, wherein P is the number of clock cycles given by the physical clock of the communication device in accordance with the time base signal during the period length of the message, and wherein Q is the number of clock cycles given by the physical clock of the other communication device in accordance with the time base signal of the other communication device during the period length of the message.

86. The communication device according to claim 75, wherein the device determines that its physical clock is slower than the physical clock of the other communication device if P is less than or equal to Q, wherein P is the number of clock cycles given by the physical clock of the communication device in accordance with the time base signal during the period length of the message, and wherein Q is the number of clock cycles given by the physical clock of the other communication device in accordance with the time base signal of the other communication device during the period length of the message.

87. The communication device according to claim 75, wherein the device determines that its physical clock is faster than the physical clock of the other communication device if P is greater than Q, wherein P is the number of clock cycles given by the physical clock of the communication device in accordance with the time base signal during the period length of the message, and wherein Q is the number of clock cycles given by the physical clock of the other communication device in accordance with the time base signal of the other communication device during the period length of the message.

88. The communication device according to claim 83, wherein the communication device resets its virtual clock counter to zero at the end of every superframe of the other communication device in accordance with the time base signal of the other communication device.

89. The communication device according to claim 86, wherein the device determines if it has the slowest physical clock in a communication system comprising the communication device and neighboring devices of the communication device.

90. The communication device according to claim 87, wherein the other communication device has the slowest physical clock of the communication devices in the communication system.

91. The communication device according to claim 71, wherein the time base signal of the other communication device is a clock signal and the parameter characterizes the clock drift between the clock signal and the clock signal of the other communication device.

92. The communication device according to claim 67, wherein the receiving circuit is configured to receive a first message and a second message and the determining circuit is configured to determine the parameter value, based on an expected reception time of the first message, an expected reception time of the second message, a reception time of the first message, and a reception time of the second message.

93. The communication device according to claim 67, wherein the time periods are regular time periods.

94. The communication device according to claim 67, wherein the time periods are clock cycles.

95. The communication device according to claim 67, wherein the offset generating circuit is configured to count a number of clock cycles having passed since the point in time.

96. The communication device according to claim 95, wherein the number of clock cycles is the number of clock cycles that have passed according to the time base signal, increased or decreased according to the parameter value.

97. The communication device according to claim 96, wherein the parameter value specifies the periodicity with which a clock cycle among the clock cycles indicated by the time base signal is not counted as clock cycle having passed since the point in time.

98. A method for generating a time indication comprising:

receiving a message from another communication device;

providing a time base signal that specifies a plurality of time periods;

determining, based on an expected reception time of the message and a reception time of the message, a parameter value characterizing a time base offset between the communication device and the other communication device;

generating a time period offset value specifying a time offset from a point in time, the time period offset value corresponding to a number of time periods from the plurality of time periods, wherein the number of time periods is determined according to the parameter value;

wherein the time base signal is a periodic time base signal; and

wherein the parameter value also characterizes the difference of the periodicity of the time base signal and the periodicity of the time base signal of the other communication device.

99. A computer program product which, when executed by a computer, makes the computer perform a method for generating a time indication comprising:

receiving a message from another communication device;

providing a time base signal that specifies a plurality of time periods;

determining, based on an expected reception time of the message and a reception time of the message, a parameter value characterizing a time base offset between the communication device and the other communication device;

generating a time period offset value specifying a time offset from a point in time, the time period offset value corresponding to a number of time periods from the plurality of time periods, wherein the number of time periods is determined according to the parameter value;

wherein the time base signal is a periodic time base signal; and

wherein the parameter value also characterizes the difference of the periodicity of the time base signal and the periodicity of the time base signal of the other communication device.

100. A method for operating an ad-hoc radio communication device in a devices'"'"' communication group, the method comprising:

generating a tone nulling synchronization negotiation message including information about the frequencies corresponding to which the ad-hoc radio communication device will null tones and including information about a specification of at least one time interval during which the ad-hoc radio communication device will null the frequencies or tones; and

transmitting the tone nulling synchronization negotiation message to at least one other ad-hoc radio communication device with which the ad-hoc radio communication device has an established communication connection in a current frequency channel;

wherein the tone nulling synchronization negotiation message further comprises a specification of a first tone or a first frequency from a set of tones or a set of frequencies according to which the ad-hoc radio communication device will null tones during the time interval.

101. An ad-hoc communication device comprising:

a sending circuit configured to transmit data on a control channel operating at a frequency range differing from another frequency range or the frequency range at which another frequency channel operates;

wherein the other frequency range or other frequency channel is used by the device to communicate with other ad-hoc communication devices in a communication group;

a memory configured to store a parameter specifying, a time interval and at least one frequency range or a starting frequency of at least one frequency range, wherein the at least one frequency range may not be used for transmitting data during the time interval using the other frequency range or the other frequency channel;

a first message generating unit configured to generate a message including a specification specifying, a time interval and at least one frequency range or the starting frequency of at least one frequency range wherein the frequency range may not be used for transmitting data during the time interval using the other frequency range or the other frequency channel;

a second message generating unit configured to generate a message including a specification of the other frequency range or the other frequency channel, the highest time slot occupied in a time period on the other frequency channel, and a time of reference for the device in the other frequency channel;

a transmitting circuit configured to transmit the messages generated by the first message generating unit and the second message generating unit.

102. The ad-hoc communication device of claim 101, wherein the control channel is a 2.4 GHz channel or a 5 GHz channel.

103. The ad-hoc communication device of claim 101, wherein the other frequency range is a band or band group, the other operating channel is a Time Frequency Code (TFC), the highest time slot occupied is a highest occupied beacon slot, the time period is the beacon period of the device, the time of reference is the Beacon Period Start Time of the device or time between the end of preamble of the message and the Beacon Period Start Time of the device in the next superframe, the data is the data included in a frame, and the message corresponds to a control frame.