1. An information communication system having an overlay network formed by participation of a plurality of node devices, mutually connected through a communication route, the node device one included in the plurality of node devices comprising:
a memory means for memorizing node information indicative of a node device to be a candidate of information transfer destination;
a participation request information transfer means for judging whether or not node information indicative of a node device of a transfer destination in response to node information of the participation request node device is memorized, in a case where a participation request into the overlay network is indicated and participation request information including the node information of the participation request node device requesting participation is received, and for transferring the participation request information to the node device, in a case where the node information indicative of the node device of the transfer destination is memorized;
an existence confirmation information sending means for judging whether or not node information indicative of a node device other than the transfer destination in response to the node information of the participation request node device being a sending source of the participation request information is memorized, in a case where the participation request information is received, and for sending existence confirmation information including the node information of the participation request node device to the node device, in a case where the node information indicative of the node device other than the transfer destination is memorized; and
a return information sending means for sending return information to the participation request node device in a case where the existence confirmation information is received.
2. A communication method in an information communication system having an overlay network that is formed by participation of a plurality of node devices mutually connected through a communication network, the communication method comprising:
a step for one node device included in the plurality of node devices of memorizing node information indicative of a node device that is included in the plurality of node devices and is to be a candidate of a information transfer destination;
a step of judging whether or not node information indicative of a node device of a transfer destination in response to the node information of the participation request node device is memorized, in a case where a participation request into the overlay network is indicated and participation request information including the node information of the participation request node device requesting participation is received, and of transferring the participation request information to the node device, in a case where the node information indicative of the node device of the transfer destination is memorized;
a step of judging whether or not node information indicative of a node device other than the transfer destination in response to the node information of the participation request node device being a sending source of the participation request information is memorized, in a case where the participation request information is received, and of sending existence confirmation information including the node information of the participation request node device to the node device, in a case where the node information indicative of the node device other than the transfer destination is memorized; and
a step of sending return information to the participation request node device in a case where the existence confirmation information is received.
3. One node device included in an information communication system having an overlay network that is formed by participation of a plurality of node devices mutually connected through a communication route comprising:
a memory means for memorizing node information indicative of a node device to be a candidate of information transfer destination;
a participation request information transfer means for judging whether or not node information indicative of a node device of a transfer destination in response to the node information of the participation request node device is memorized in a case where a participation request into the overlay network is indicated and participation request information including the node information of the participation request node device requesting participation is received, and for transferring the participation request information to the node device in a case where the node information indicative of the node device of the transfer destination is memorized;
an existence confirmation information sending means for judging whether or not node information indicative of a node device other than transfer destination in response to the node information of the participation request node device being a sending source of the participation request information is memorized, in a case where the participation request information is received, and for sending existence confirmation information including the node information of the participation request node device to the node device, in a case where the node information indicative of the node device other than the transfer destination is memorized; and
a return information sending means for sending return information to the participation request node device in a case where the existence confirmation information is received.
4. The node device receiving the return information from the node device according to claim 3, further comprising:
a memory means for memorizing the node information corresponding to the node device of the sending source of the return information thus received.
5. The node device according to claim 3,
wherein the memory means memorizes the node information and an inherent identification information corresponding to the node information in correspondence with every regions of the identification information,
the participation request information transfer means adds region designation information designating a predetermined region in the memory means to the participation request information when the participation request information is transferred, and
the existence confirmation information sending means sends the existence confirmation information to the node device, in a case where node information of the other node device to be the sending destination is memorized, based on whether or not the region designation information is added to the participation request information thus received and content of the region designation information.
6. The node device according to claim 5,
wherein a region of the identification information is divided into a plurality of regions according to a rule of the identification information and the region to which the own node device belongs is further divided into a plurality of regions according to the rule of the identification information up to a stage where the region to which only the own node device belongs exists,
the existence confirmation information sending means sends the existence confirmation information to the other node device belonging to a region corresponding to a region designation information of the memorized identification information in a case where the region designation information is added to the received participation request information, and
the participation request information transfer means adds the region designation information designating a region corresponding a smaller scope than that of the region of the identification information, corresponding to the region designation information, to the participation request information, in a case where the region designation information is added to the participation request information thus received.
7. The node device according to claim 3, further comprising:
a node information sending means for sending the node information of the node device being a sending destination of the existence confirmation information to the participation request node device in a case where the existence confirmation information is sent by the existence confirmation information sending means.
8. A computer program embodied in a computer-readable medium and representing a sequence of instructions, which when executed by a computer included in a node device, the instructions cause the computer to function as: the node device according to claim 3.
9. The node device according to claim 5, further comprising:
a node information sending means for sending the node information of the node device being a sending destination of the existence confirmation information to the participation request node device in a case where the existence confirmation information is sent by the existence confirmation information sending means.
10. The node device according to claim 6, further comprising:
a node information sending means for sending the node information of the node device being a sending destination of the existence confirmation information to the participation request node device in a case where the existence confirmation information is sent by the existence confirmation information sending means.
The claims below are in addition to those above.
All refrences to claim(s) which appear below refer to the numbering after this setence.
1. A method comprising:
receiving an incoming signal communicated across a multiple-input-multiple-output (MIMO) communication channel;
sampling the incoming signal to generate a sampled signal;
transforming the sampled signal from a time-domain signal to a frequency-domain signal by use of a Fast Fourier Transform (FFT) to generate a transformed sampled signal;
determining a carrier frequency offset (CFO) from the sampled signal, in which preambles to be utilized for channel estimation are communicated in symbols over more than one time period and in which the symbols have subcarriers that are orthogonal, wherein a first symbol communicated during a first time period and a second symbol communicated during a second time period have a substantially flat phase response across respective subcarriers, but have a phase difference between the first symbol and the second symbol that results in a CFO phase shift between the first and second symbols that is due to a difference in time between the first and the second time periods;
calculating the phase difference between the first and second symbols at one subcarrier;
applying the calculated phase difference to all subcarriers;
applying the transformed sampled signal and calculated phase difference to modify a weighting matrix that is employed to perform channel estimation to determine an estimate of the communication channel, the weighting matrix modified for all subcarriers to account for the CFO phase shift; and
performing channel estimation using the modified weighting matrix to correct for the CFO phase shift between the first and second time periods.
2. The method of claim 1, wherein the first and second symbols are communicated by orthogonal frequency division multiplexing (OFDM).
3. The method of claim 2, wherein an OFDM signal is communicated in more than one time period, in which even tones of the OFDM signal are communicated during one of the first or second time period and odd tones are communicated during other of the first or second time period.
4. The method of claim 3, wherein the weighting matrix has terms to account for both a carrier frequency phase \u03b1 for the first symbol and a carrier frequency phase \u03b2 for the second symbol, in which the subcarriers represent tones of the OFDM signal and the tones have a flat phase response across all tones that are present.
5. The method of claim 4, wherein the weighting matrix is further modified to provide a second weighting matrix, in which a phase difference (\u03b2\u2212\u03b1) is absorbed into the second weighting matrix to account for the CFO phase shift when performing channel estimation.
6. The method of claim 5, wherein the second weighting matrix is utilized on a modified channel H\u2032 to perform channel estimation on symbols received by one of a plurality of receiving antennas, in which the channel estimation is provided using a training sequence present in one or more preambles in the first and second symbols.
7. An apparatus comprising:
a sampling module coupled to receive an incoming signal communicated across a multiple-input-multiple-output (MIMO) communication channel and to sample the incoming signal;
a Fast Fourier Transform (FFT) module coupled to transform the sampled signal from a time-domain signal to a frequency-domain signal;
a carrier frequency offset (CFO) calculation module coupled to receive the sampled signal from the sampling module and to determine a phase of the carrier frequency for the incoming signal based on preambles that are to be utilized for channel estimation, the CFO calculation module to determine a carrier frequency phase for a first symbol and for a second symbol, in which the symbols have subcarriers that are orthogonal and substantially flat in phase response, but have a phase difference between the first symbol and the second symbol that results in a CFO phase shift between the first and second symbols that is due to a difference in time between a first time period and a second time period, wherein the CFO calculation module calculates the phase difference between the first and second symbols at one subcarrier and applies the calculated phase difference to all subcarriers;
a channel estimator module coupled to the FFT module to receive the transformed sampled signal and also coupled to the CFO calculation module to receive phase difference information to perform channel estimation of the communication channel which is corrected for the phase difference, the channel estimator module to modify a weighting matrix that is employed to perform channel estimation by use of the phase difference information to determine an estimate of the communication channel, the weighting matrix modified to account for the CFO phase shift between the first time period and the second time period.
8. The apparatus of claim 7, wherein the incoming signal is a orthogonal frequency division multiplexing (OFDM) signal.
9. The apparatus of claim 8, wherein the weighting matrix has terms to account for both a carrier frequency phase \u03b1 for the first symbol and a carrier frequency phase \u03b2 for the second symbol, in which the subcarriers represent tones of the OFDM signal and the tones have a flat phase response across all tones that are present.
10. The apparatus of claim 9, wherein the weighting matrix is further modified to provide a second weighting matrix, in which a phase difference (\u03b2\u2212\u03b1) is absorbed into the second weighting matrix to account for the CFO phase shift when performing channel estimation.
11. The apparatus of claim 7 further comprising a CFO correction generator module coupled to the CFO calculation module to generate an offset signal to correct for the CFO phase shift of the incoming signal.
12. The apparatus of claim 8, wherein the OFDM signal is received in which even tones of the OFDM signal are received during one of the first or second time block and odd tones are received during other of the first or second time block.