US 5,774,450 A · Method of transmitting orthogonal frequency division multiplexing signal and receiver thereof

Abstract

An orthogonal frequency division multiplexing signal transmitted from the transmitting end to the receiving end intermittently includes a particular symbol S0 having a predetermined particular pattern in addition to a symbol Sm including data to be transmitted. At the receiving end, the variation in the receiving level and/or the variation in the frequency band of a received signal are detected and corrected on the basis of the received particular symbol S0. Since the particular symbol S0 has a particular pattern, the variation in the level and/or the variation in the frequency are strongly correlated with the variation in the receiving level and/or the variation in the frequency band of the received signal. Consequently, the variation in the receiving level and/or the variation in the frequency band of the received signal can be accurately detected from the particular symbol S0 and consequently high-precision correction can be made.

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Claims16

Dependent claims

A method of transmitting an orthogonal frequency division multiplexing signal for each of a plurality of symbols having a predetermined length, from a transmitting end to a receiving end through a wire or radio transmission line, said method comprising:

the transmitting end continuously transmitting a first symbol which includes data to be transmitted, a multiplexing signal of the data randomly changing;
and
the transmitting end intermittently transmitting a second symbol having a predetermined particular pattern, every time a predetermined number of the first symbols are transmitted;
and
the receiving end demodulating data on the basis of the received first symbol;
and
the receiving end correcting the variation in a receiving level based on the received second symbol.

4 more elements

a particular symbol having a predetermined particular pattern is intermittently inserted into the orthogonal frequency division multiplexing signal, said receiver comprising:
automatic gain control amplifying means having a control terminal and whose gain varies depending on a control signal inputted to said control terminal, for changing the level of the received orthogonal frequency division multiplexing signal;
and
control signal outputting means for detecting the particular symbol from the orthogonal frequency division multiplexing signal whose level has been changed by said automatic gain control amplifying means and generating a signal corresponding to the change in the level of the particular signal,
wherein the signal generated by said control signal outputting means is fed back as the control signal to said automatic gain control amplifying means, to correct the variation in the receiving level of the orthogonal frequency division multiplexing signal.

2 more elements

A receiver for receiving an orthogonal frequency division multiplexing signal transmitted for each of a plurality of symbols having a predetermined length, from a transmitting end through a wire or radio transmission line and demodulating data from the received orthogonal frequency division multiplexing signal, wherein a particular symbol having a predetermined particular pattern is intermittently inserted into the orthogonal frequency division multiplexing signal, said receiver comprising:

frequency converting means having a control terminal and whose amount of frequency shift varies depending on a control signal inputted to the control terminal for changing the frequency band of said orthogonal frequency division multiplexing signal;
and
control signal outputting means for detecting the particular symbol from the orthogonal frequency division multiplexing signal whose frequency band has been changed by said frequency converting means and generating a signal corresponding to the change in the frequency band of the particular symbol.
wherein the signal generated by said control signal outputting means is fed back as the control signal to correct the variation in the frequency band of the orthogonal frequency division multiplexing signal;
and wherein
said control signal outputting means comprises
envelope detecting means for envelope-detecting each of said symbols, to output and envelope signal representing an envelope of the detected symbol,
reference timing generating means for comparing a pattern of said envelope signal, for each symbol, with a particular pattern previously stored, to generate a reference timing signal indicating whether or not the particular symbol is detected,
frequency discriminating means for frequency-discriminating each of said symbols, to generate a frequency discriminating signal corresponding to the frequency of the symbol, and
sampling-and-holding means for sampling and holding as the control signal the frequency discriminating signal outputted from said frequency discriminating means when the reference timing signal represents the detected state of the particular symbol.

7 more elements

A receiver for receiving an orthogonal frequency division multiplexing signal transmitted for each of a plurality of symbols having a predetermined length from a transmitting end through a wire or radio transmission line and demodulating data from the received orthogonal frequency division multiplexing signal, wherein a particular symbol having a predetermined particular pattern is intermittently inserted into the orthogonal frequency division multiplexing signal, said receiver comprising:

frequency converting means having a control terminal and whose amount of frequency shift varies depending on a control signal inputted to the control terminal, for changing the frequency band of said orthogonal frequency division multiplexing signal:
and
control signal outputting means for detecting the particular symbol from the orthogonal frequency division multiplexing signal whose frequency band has been changed by said frequency converting means and generating a signal corresponding to the change in the frequency band of the particular symbol,
wherein the signal generated by said control signal outputting means is fed back as the control signal, to correct the variation in the frequency band of the orthogonal frequency division multiplexing signal;
and wherein
said control signal outputting means comprises
envelope detecting means for envelope-detecting each of said symbols, to output and envelope signal representing an envelope of the detected symbol,
reference timing generating means for comparing a pattern of said envelope signal, for each symbol, with a particular pattern previously stored, to generate a reference timing signal indicating whether or not the particular symbol is detected,
frequency region energy detecting means for dividing a signal component on the frequency axis of each of said symbols into two regions having a predetermined center frequency as its boundary, comparing energy in the region having a frequency lower than the center frequency with energy in the region having a frequency higher than the center frequency, to generate a frequency region energy signal corresponding to the difference in energy between both the regions, and
sampling-and-holding means for sampling and holding as the control signal the frequency region energy signal outputting from said frequency region energy detecting means when the reference timing signal represents the detected state of the particular symbol.

7 more elements

frequency converting means having a control terminal and whose amount of frequency shift varies depending on a control signal inputted to the control terminal, for changing the frequency band of said orthogonal frequency division multiplexing signal:
and
control signal outputting means for detecting the particular symbol from the orthogonal frequency division multiplexing signal whose frequency band has been changed by said frequency converting means and generating a signal corresponding to the change in the frequency band of the particular symbol,
wherein the signal generated by said control signal outputting means is fed back as the control signal, to correct the variation in the frequency band of the orthogonal frequency division multiplexing signal;
and wherein
said control signal outputting means comprises
envelope detecting means for envelope-detecting each of said symbols, to output and envelope signal representing an envelope of the detected symbol,
reference timing generating means for comparing a pattern of said envelope signal, for each symbol, with a particular pattern previously stored, to generate a reference timing signal indicating whether or not the particular symbol is detected,
correlation detecting means for outputting a correlation signal representing the correlation intensity between a frequency component of each of said symbols and a frequency component of the particular symbol previously stored and the shift from a predetermined center frequency,
peak value frequency detecting means for detecting the frequency at which a peak value of the correlation intensity exists from the correlation signal outputted from said correlation detecting means and outputting a peak value frequency signal corresponding to the difference between the detected frequency and the predetermined center frequency, and
sampling-and-holding means for sampling and holding as the control signal the peak value frequency signal outputted from said peak value frequency detecting means when said reference timing signal represents the detected state of the particular symbol.

8 more elements

Dependencies are inferred from the claim text.

Description11,611 words

Summary3,477 words

#1. Field of the Invention

#The present invention relates generally to a method of transmitting an orthogonal frequency division multiplexing signal and a receiver thereof, and more particularly, to a method of transmitting an orthogonal frequency division multiplexing signal for each symbol having a predetermined length from the transmitting end to the receiving end through a predetermined transmission line, and a receiver thereof.

#2. Description of the Background Art

Brief description of the drawings12 figures

#FIG. 1 is a diagram showing one example of the structure of an OFDM signal transmitted from the transmitting end in the present invention;

#FIG. 2 is a block diagram showing the construction of a receiver according to a first embodiment of the present invention;

#FIG. 3 is a waveform diagram showing signals in each of sections of the receiver shown in FIG. 2;

Detailed description7,877 words

#Description is now made of embodiments of the present invention on the basis of drawings. FIG. 1 is a diagram showing one example of the structure of an OFDM signal transmitted from the transmitting end to the receiving end in the present invention. Particularly, FIG. 1 (a) shows respective symbols of the OFDM signal along the time axis, and FIG. 1 (b) shows a portion .alpha. shown in FIG. 1 (a) in an enlarged manner.

#As shown in FIG. 1 (a), an OFDM signal S is constructed by arranging a particular symbol S0 for automatic gain control indicated by hatching and symbols Sm (m=1, 2, . . . ) for demodulation indicated without hatching along the time axis. The symbol S0 is inserted for each predetermined symbol interval (e.g., for each interval of 15 symbols). The OFDM signal S takes the form of an analog complex signal in which a real part and an imaginary part are superposed with respect to each of the symbols S0 and Sm on a transmission line.

#Each of the symbols Sm is constructed by multiplexing (performing an inverse fast Fourier operation of) a plurality of (tens to thousands of, for example, 512) carriers which differ in frequency (which are orthogonal in symbol time ts) on the frequency axis. Each of the carriers is subjected to digital modulation (e.g., QPSK modulation or 16QAM) by data to be demodulated at the receiving end. Therefore, each of the symbols Sm exhibits a random amplitude distribution, as shown in FIG. 1 (b).

Description11,611 words

Summary3,477 words

#1. Field of the Invention

#2. Description of the Background Art

Brief description of the drawings12 figures

#FIG. 1 is a diagram showing one example of the structure of an OFDM signal transmitted from the transmitting end in the present invention;

#FIG. 2 is a block diagram showing the construction of a receiver according to a first embodiment of the present invention;

#FIG. 3 is a waveform diagram showing signals in each of sections of the receiver shown in FIG. 2;

Detailed description7,877 words

Method of transmitting orthogonal frequency division multiplexing signal and receiver thereof

Life of this patent

Method of transmitting orthogonal frequency division multiplexing signal and receiver thereof

Life of this patent

Life of this patent

Abstract

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Claims16

Description11,611 words

Drawings

Classification11 codes

Life of this patent

Description11,611 words