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

• US 6,611,493 B1
• Filed: 01/26/1999
• Issued: 08/26/2003
• Est. Priority Date: 01/27/1998
• Status: Expired due to Fees

• Current Assignee: Hitachi Denshi Kabushiki Kaisha
• Original Assignee: Hitachi Denshi Kabushiki Kaisha
• Inventors: Nakada, Tatuhiro, Tsukamoto, Nobuo, Akiyama, Toshiyuki, Miyashita, Atsushi, Sano, Seiichi, Takesue, Hiroyuki
• Primary Examiner(s): Olms, Douglas
• Assistant Examiner(s): Pizarro, Ricardo M.
• Application Number:
  US09/236,601
• Time in Patent Office: 1,673 Days
• Field of Search: 370/208, 370/204, 370/205, 370/206, 370/207, 370/212, 370/213, 370/215, 370/668, 370/210, 370/252, 370/543, 370/260, 370/244, 370/226, 370/364, 370/324, 370/362, 370/371, 370/261, 370/482, 370/480
• US Class Current: 370/208
• CPC Class Codes: H04L 5/0044 allocation of payload

Abstract

A communication method in an orthogonal frequency division multiplexing modulation communication system includes a transmission apparatus in which a frequency bandwidth of a signal modulated in accordance with an orthogonal frequency division multiplexing modulation system is changed and the modulated signal is transmitted and a receiving apparatus in which the modulated signal is received and a frequency bandwidth for demodulation of the received signal is changed to follow the change of the frequency bandwidth of the modulated signal.

Claims

1. 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 the number of carriers of said transmission signal, and

wherein said changing step of the 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 synchronization signal added to said modulated signal, and

changing a transmission signal level to satisfy a transmission condition.

2. A communication method according to claim 1, comprising performing, in accordance with the change of the number of carriers in said transmission apparatus, the steps of:

changing a reference signal pattern for synchronization detection in said receiving apparatus to detect the 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.

3. A communication method according to claim 1, wherein the number of carrier signals is detected from said received signal and when it is detected that the number of carriers is changed, a control signal for indicating change of a reference signal pattern for synchronization detection in said receiving apparatus, change of an effective data period of a signal obtained by decoding said received signal, and change of a taking-in period of data component in said effective data period is produced.

4. A communication method according to claim 1, further comprising the steps of:

producing a control signal for changing the setting of frequency bandwidth of said transmission signal to a predetermined bandwidth; and

changing the setting of frequency bandwidth of said signal modulated in accordance with the orthogonal frequency division multiplexing modulation method in accordance with said control signal.

11. A communication method according to claim 1, wherein said orthogonal frequency division multiplexing modulation system is a digital modulation system for at least one wave of carriers being a quadrature amplitude modulation system.

5. 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.

6. A communication method according to claim 5, wherein said modulated signal includes a synchronizing signal and said synchronizing signal is detected from said received signal, a phase of said detected synchronizing signal being compared with a phase of a reference signal prepared on the basis of a current clock signal in said receiving apparatus so that said frequency of said clock signal in said receiving apparatus is changed in accordance with a phase difference.

7. A communication method according to claim 5, wherein when an interval between adjacent carrier signals of said modulated signal is changed in accordance with the change of said frequency of said clock signal in said transmission apparatus and said received signal is decoded, omission of said carrier signals is detected and said frequency of said clock signal in said receiving apparatus is controlled to dissolve the omission of said carrier signals.

8. A communication method according to claim 7, wherein said changing step of said frequency of said clock signal in said receiving apparatus includes the steps of changing said frequency by a first change amount and a step of changing said frequency by a second change amount smaller than said first change amount.

9. A communication method according to claim 6, comprising controlling a phase of said clock signal together with the change of said frequency of said clock signal in said receiving apparatus.

10. A communication method according to claim 5, further comprising the steps of:

producing a control signal for changing said frequency bandwidth of said signal to be transmitted; and

changing said setting of frequency bandwidth of said signal modulated with the orthogonal frequency division multiplexing modulation method in accordance with said control signal.

12. 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.

13. 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.

14. A receiving method according to claim 13, wherein the number of carriers is detected from said received signal and when it is detected that the number of carriers is changed, a control signal for indicating change of said reference signal pattern for synchronization detection in said receiving apparatus, change of said effective data period of a signal obtained by decoding said received signal, and change of said taking-in period of the data component in said effective data period is produced.

15. 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.

16. A receiving method according to claim 15, wherein when an interval between adjacent carrier signals of said modulated signal is changed in accordance with change of a frequency of a clock signal in a transmission apparatus, omission of said carrier signals is detected when said received signal is decoded and said frequency of said clock signal in said receiving apparatus is controlled to dissolve the omission of said carrier signals.

17. 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.

18. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 17, wherein said receiving apparatus comprises an orthogonal demodulation processing unit for 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, which changes a pattern of a reference signal for detection of said synchronizing symbol, changes an effective data period of the decoded signal in said decoding unit, and changes a taking-in period of data component in said data rate inverse-conversion unit in accordance with the change of the number of carriers in said transmission apparatus.

19. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 17, wherein said receiving apparatus comprises an orthogonal demodulation processing unit for 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, which produces 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.

20. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 18 or 19, wherein said transmission apparatus further comprises transmission level changing means for adjusting a level of the transmission signal in accordance with the change of the number of carriers and changing a gain of said coding unit or said inverse Fourier transform unit by an inverse number of a value multiplied by a square root of a change rate of the number of carriers and said receiving apparatus further comprises reception level changing means for adjusting a level of the received signal in accordance with the change of the number of carriers and for changing a gain of said Fourier transform unit or said decoding unit by an inverse number of a value multiplied by a square root of the change rate of the number of carriers.

21. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 17, wherein the change of the number of carriers is made each symbol of said modulated signal.

22. 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.

23. 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.

24. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 23, wherein said receiving apparatus comprises an orthogonal demodulation processing unit for 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 the frequency bandwidth of the modulated signal on the basis of the decoded signal, a clock signal generation unit for supplying a clock signal to said orthogonal demodulation processing unit, said Fourier transform unit, said decoding 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.

25. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 24, wherein said receiving apparatus comprises a clock rate conversion unit for detecting said synchronizing symbol from the received signal and comparing a phase of said detected synchronizing symbol with a phase of a reference signal prepared on the basis of a current clock signal in said clock signal generation unit so that the frequency of the clock signal in said receiving apparatus is changed in accordance with a phase difference.

26. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 24, wherein an interval between adjacent carrier signals of said modulated signal is changed by changing the frequency of the clock signal in said transmission apparatus and omission of said carrier signals in the decoded signal in said decoding unit of said receiving apparatus is detected, so that said changing means of said clock signal frequency controls the frequency of said clock signal generation unit so that omission of said carrier signals is dissolved.

27. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 26, wherein said clock signal generation unit of said receiving apparatus includes a clock signal generator for changing the frequency by a first change amount and a second clock signal changing unit for further changing the clock frequency by a second change amount.

28. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 23, further comprising:

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,

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 from said monitoring apparatus.

29. An orthogonal frequency division multiplexing modulation communication apparatus according to claim 23, wherein said orthogonal frequency division multiplexing modulation system is a digital modulation system for at least one wave of carriers being a quadrature amplitude modulation system.

30. 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.

31. 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.

32. 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.

33. 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.

34. 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.