Communication, transmission and receiving method and apparatus using orthogonal frequency division multiplexing modulation system

A communication method in an orthogonal frequency division multiplexing modulation communication system, comprising the steps of:

• changing, in a transmission apparatus, a setting of frequency bandwidth of a signal which was modulated in accordance with an orthogonal frequency division multiplexing modulation method to a predetermined bandwidth within a bandwidth allocated to said communication system;
• transmitting said modulated signal;
• and
• receiving, in a receiving apparatus, said modulated transmission signal and changing a setting of demodulation frequency bandwidth of said received signal to follow the change of said frequency bandwidth of said modulated signal,
• wherein the setting change of said frequency bandwidth of said modulated signal is made by changing a frequency of a clock signal in said transmission apparatus, and
• wherein the setting change of said frequency bandwidth of said modulated signal is detected based on said received signal and a frequency of a clock signal in said receiving apparatus is changed in accordance with the detected change of said frequency bandwidth to thereby change said demodulation frequency bandwidth.

A transmission method in an orthogonal frequency division multiplexing modulation communication system, comprising the steps of:

• changing a setting of frequency bandwidth of a signal which was modulated in accordance with an orthogonal frequency division multiplexing modulation method to a predetermined bandwidth within a bandwidth allocated to said communication system by changing the number of carriers of said signal;
• and
• transmitting said modulated signal,
• wherein said changing step of said number of carriers includes the steps of:
• changing an amount of input data per unit time in said transmission apparatus,
• changing an effective data period of said modulated signal,
• changing a pattern of a synchronizing signal added to said modulated signal, and
• changing a transmission signal level to satisfy a transmission condition.

A receiving method in an orthogonal frequency division multiplexing modulation communication system, comprising the steps of:

• receiving, in a receiving apparatus, an orthogonal frequency division multiplexing modulated signal having a changed bandwidth;
• and
• changing a demodulation frequency bandwidth of said received signal to follow change of a frequency bandwidth of said modulated signal;
• said changing step of said demodulation frequency bandwidth further including the steps of:
• changing a reference signal pattern for synchronization detection in said receiving apparatus to detect a synchronizing signal from said received signal;
• changing an effective data period of a signal obtained by decoding said received signal and
• changing a taking-in period of data component in said effective data period.

A receiving method in an orthogonal frequency division multiplexing modulation communication system, comprising the steps of:

• receiving, in a receiving apparatus, an orthogonal frequency division multiplexing modulated signal having a changed bandwidth;
• and
• changing a demodulation frequency bandwidth of said received signal to follow change of a frequency bandwidth of said modulated signal;
• said changing step of said demodulation frequency bandwidth further including the steps of:
• detecting a synchronizing signal from said received signal, comparing a phase of said detected synchronizing signal with a phase of a reference signal prepared on the basis of a current clock signal in said receiving apparatus, and changing a frequency of the clock signal in said receiving apparatus in accordance with a phase difference.

An orthogonal frequency division multiplexing modulation communication apparatus comprising:

• a transmission apparatus for changing a setting of frequency bandwidth of a signal modulated in accordance with an orthogonal frequency division multiplexing modulation system and transmitting the modulated signal;
• a receiving apparatus for receiving said modulated signal and changing a demodulation frequency bandwidth of the received signal to follow the change of said frequency bandwidth of said modulated signal;
• and
• means for changing the number of carriers of said modulated signal to thereby change said frequency bandwidth,
• wherein said transmission apparatus comprises:
• a data rate conversion unit for converting successively inputted data into data arrangement of frame unit constituted by a predetermined number of symbols,
• a coding unit for coding a signal supplied from said data rate conversion unit,
• an inverse Fourier transform unit for transforming the coded signal into a time-axis base signal,
• a synchronizing symbol insertion unit for inserting a synchronizing symbol into the inverse Fourier transformed signal every predetermined symbol period, and
• an orthogonal modulation processing unit for orthogonally modulating said synchronizing symbol inserted signal,
• wherein said means for changing the number of carriers includes:
• means for changing an input data amount per unit time in said data rate conversion unit, changing an effective data period of said modulated signal in said coding unit, and changing a pattern of said synchronizing symbol added to the signal in said synchronizing symbol insertion unit.

An orthogonal frequency division multiplexing modulation communication apparatus comprising:

• a transmission apparatus for changing a setting of frequency bandwidth of a signal modulated in accordance with an orthogonal frequency division multiplexing modulation system and transmitting the modulated signal;
• a receiving apparatus for receiving said modulated signal and changing a demodulation frequency bandwidth of the received signal to follow the change of said frequency bandwidth of said modulated signal;
• and
• a monitoring apparatus for monitoring a state of a communication path and producing a control signal for changing the frequency bandwidth of the signal to be transmitted, and
• wherein said transmission apparatus changes the frequency bandwidth of the signal modulated by the orthogonal frequency division multiplexing modulation system in accordance with said control signal.

An orthogonal frequency division multiplexing modulation communication apparatus comprising:

• a transmission apparatus for changing a setting of frequency bandwidth of a signal modulated in accordance with an orthogonal frequency division multiplexing modulation system and transmitting the modulated signal;
• a receiving apparatus for receiving said modulated signal and changing a demodulation frequency bandwidth of the received signal to follow the change of said frequency bandwidth of said modulated signal;
• and
• means for changing the frequency bandwidth by changing a frequency of a clock signal used in said transmission apparatus,
• wherein said transmission apparatus comprises:
• a data rate conversion unit for converting successively inputted data into data arrangement of frame unit constituted by a predetermined number of symbols,
• a coding unit for coding a signal supplied from said data rate conversion unit,
• an inverse Fourier transform unit for transforming the coded signal into a time-axis base signal,
• a synchronizing symbol insertion unit for inserting a synchronizing symbol into the inverse Fourier transformed signal every predetermined symbol period, and
• an orthogonal modulation processing unit for orthogonally modulating said synchronizing symbol inserted signal, and
• wherein said means for changing the frequency bandwidth includes:
• said data rate conversion unit,
• said coding unit,
• said inverse Fourier conversion unit,
• said synchronizing symbol insertion unit, and
• means for changing the frequency of the clock signal supplied to said orthogonal modulation processing unit.

A transmission apparatus for an orthogonal frequency division multiplexing modulated signal, comprising:

• a data rate conversion unit for converting successively inputted data into data arrangement of frame unit constituted by a predetermined number of symbols;
• a coding unit for coding a signal supplied from said data rate conversion unit;
• an inverse Fourier transform unit for transforming the coded signal into a time-axis base signal;
• a synchronizing symbol insertion unit for inserting a synchronizing symbol into the inverse Fourier transformed signal every predetermined symbol period;
• an orthogonal modulation processing unit for orthogonally modulating said synchronizing symbol inserted signal;
• and
• means for changing an input data amount per unit time in said data rate conversion unit, changing an effective data period of said modulated signal in said coding unit, and changing a pattern of said synchronizing symbol added to the signal in said synchronizing symbol insertion unit to thereby control the number of carriers of a transmission signal to change a frequency bandwidth of the transmission signal.

A transmission apparatus for an orthogonal frequency division multiplexing modulated signal, comprising:

• a data rate conversion unit for converting successively inputted data into data arrangement of frame unit constituted by a predetermined number of symbols;
• a coding unit for coding a signal supplied from said data rate conversion unit;
• an inverse Fourier transform unit for transforming the coded signal into a time-axis base signal;
• a synchronizing symbol insertion unit for inserting a synchronizing symbol into the inverse Fourier transformed signal every predetermined symbol period;
• an orthogonal modulation processing unit for orthogonally modulating said synchronizing symbol inserted signal;
• and
• means for changing a frequency bandwidth in accordance with change of a frequency of a clock signal used in said transmission apparatus and including said data rate conversion unit, said coding unit, said inverse Fourier transform unit, said synchronizing symbol insertion unit and means for changing a frequency of a clock signal supplied to said orthogonal modulation processing unit.

A receiving apparatus for an orthogonal frequency division multiplexing modulated signal, comprising:

• an orthogonal demodulation processing unit for receiving the orthogonal frequency division multiplexing modulated signal having a bandwidth changed by changing the number of carriers and orthogonally demodulating the received signal;
• a Fourier transform unit for transforming the demodulated signal into a frequency-axis base signal;
• a decoding unit for decoding the Fourier transformed signal;
• a data rate inverse-conversion unit for converting the decoded signal into successive data;
• a synchronization detection unit for detecting a synchronizing symbol from the received signal;
• and
• a control unit for changing a pattern of a reference signal for detection of said synchronizing symbol, changing an effective data period of the decoded signal in said decoding unit, and changing a taking-in period of data component in said data rate inverse-conversion unit in accordance with the change of the number of carriers.

A receiving apparatus for an orthogonal frequency division multiplexing modulated signal, comprising:

• an orthogonal demodulation processing unit for receiving the orthogonal frequency division multiplexing modulated signal having a bandwidth changed by changing the number of carriers and orthogonally demodulating the received signal;
• a Fourier transform unit for transforming the demodulated signal into a frequency-axis base signal;
• a decoding unit for decoding the Fourier transformed signal;
• a data rate inverse-conversion unit for converting the decoded signal into successive data;
• a synchronization detection unit for detecting a synchronizing symbol from the received signal;
• a data confirmation unit for detecting the number of carrier signals from the Fourier transformed signal;
• and
• a control unit for producing a control signal for changing a pattern of a reference signal for detection of said synchronizing symbol, changing an effective data period of the decoded signal in said decoding unit, and changing a taking-in period of data component in said data rate inverse-conversion unit when said data confirmation unit detects that the number of carriers is changed.

A receiving apparatus for an orthogonal frequency division multiplexing modulated signal, comprising:

• an orthogonal demodulation processing unit for receiving the orthogonal frequency division multiplexing modulated signal having a changed bandwidth and orthogonally demodulating the received signal;
• a Fourier transform unit for transforming the demodulated signal into a frequency-axis base signal;
• a decoding unit for decoding the Fourier transformed signal;
• a data rate inverse-conversion unit for converting the decoded signal into successive data;
• a synchronization detection unit for detecting a synchronizing symbol from the received signal;
• a data confirmation unit for detecting change of a frequency bandwidth of said modulated signal on the basis of the decoded signal;
• a clock signal generating unit for supplying a clock signal to said orthogonal demodulation processing unit, said Fourier transform unit, said coding unit, said data rate conversion unit, said synchronization detection unit and said data confirmation unit;
• and
• means for changing a frequency of the clock signal of said clock signal generation unit in accordance with detection of the change of the frequency bandwidth.