US5610908A
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Digital signal transmission system using frequency division multiplex
Assignee: British Broadcasting Corp
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Filing: 1993-09-06
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Granted: 1997-03-11
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Expires: 2013-09-06
Abstract
Abstract PCT No. PCT/GB93/01884 Sec. 371 Date Jul. 28, 1995 Sec. 102(e) Date Jul. 28, 1995 PCT Filed Sep. 6, 1993 PCT Pub. No. WO94/06231 PCT Pub. Date Mar. 17, 1994A frequency-division multiplexer for carrying an OFDM signal on a large number of closely-spaced carriers receives the digital data at an input (12), applies coding such as convolutional coding (14), time interleaves (16) the signals, and assembles them frame-by-frame in a matrix (18). The data are converted to parallel form by a shift register (18), frequency interleaved (24), differentially encoded (26), and quadrature-phase-modulated (28) on several hundred or more closely-spaced carriers. A first inverse Fast Fourier Transform (FFT) circuit (30) transforms this information from the frequency domain into the time domain. Instead of being transmitted directly, the resultant signals are then amplitude-limited (42) and applied to an FFT (44) to reconvert them into the frequency domain. The phases of the wanted signals are then re-set, and the amplitudes of the signals near the edges of the band are reduced, in correction circuits (46). The resultant signals are applied to a second inverse FFT (48) for transmission. The output of the second inverse FFT contains smaller power peaks than the output of the first inverse FFT (30). The output is converted to serial form by a shift register (32), a guard interval is added (34), and the resultant converted (36) to analog form.
Inventors
- 👤 Peter Shelswell
- 👤 Mark Charles D. Maddocks
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-26 21:17
CPC Classifications
H; H04; H04L; H04L1/00; H04L1/004; H04L1/0056; H04L1/0059; H04L1/0071; H04L27/00; H04L27/26; H04L27/2601; H04L27/2614; H04L27/2621; H04L27/2623; H04L27/2626; H04L27/2627; H04L27/2634
Claims Analysis
Total Claims: 21
Claim 1
Independent Claim
150 words
A method of transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising the steps of: modulating a plurality of carriers with respective bits of the digital data by a modulation method which carries the information in the phase or amplitude of the individual carriers to provide a plurality of first modulated signals; reversibly transforming the first modulated signals from the frequency domain to the time domain to provide first time domain signals; limiting the first time domain signal to limit their amplitude or power to provide limited time domain signals; inversely transforming the limited time domain signals into a plurality of second modulated signals in the frequency domain; adjusting the phase and/or amplitude of some of the second modulating signals to provide a plurality of adjusted signals; and transforming the adjusted signals from the frequency domain to the time domain to provide second time domain signals for transmission.
Claim 2
Independent Claim
150 words
A method of transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising the steps of: modulating a plurality of carriers with respective bits of the digital data by a modulation method which carries the information in the phase or amplitude of the individual carriers to provide a plurality of first modulated signals; reversibly transforming the first modulated signals from the frequency domain to the time domain to provide first time domain signals; limiting the first time domain signal to limit their amplitude or power to provide limited time domain signals; inversely transforming the limited time domain signals into a plurality of second modulated signals in the frequency domain; adjusting the phase and/or amplitude of some of the second modulating signals to provide a plurality of adjusted signals; and transforming the adjusted signals from the frequency domain to the time domain to provide second time domain signals for transmission.
Claim 3
Dependent Claim
198 words
A many-carrier frequency-division-multiplex transmitter, comprising: input means for receiving a digital data stream for transmission; means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data by a modulation method which carries the information in the phase or amplitude of the individual carriers to provide a plurality of first modulated signals; first transform means coupled to the modulating means for reversibly transforming the first modulated signals from the frequency domains to the time domain to provide first time domain signals; means coupled to the first transform means for limiting the first time domain signals to limit their amplitude or power to provide limited time domain signals; second transforms means coupled to the limiting means for inversely transforming the limit time domain signals into a plurality of second modulated signals in the frequency domain; means coupled to the second transform means for adjusting the phase and/or amplitude of some of the second modulated signals to provide a plurality of adjusted signals; and third transform means coupled to the adjusting means for transforming the adjusting signals from the frequency domain to the time domain to provide second time domain signals for transmission.
Claim 4
Dependent Claim
198 words
A many-carrier frequency-division-multiplex transmitter, comprising: input means for receiving a digital data stream for transmission; means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data by a modulation method which carries the information in the phase or amplitude of the individual carriers to provide a plurality of first modulated signals; first transform means coupled to the modulating means for reversibly transforming the first modulated signals from the frequency domains to the time domain to provide first time domain signals; means coupled to the first transform means for limiting the first time domain signals to limit their amplitude or power to provide limited time domain signals; second transforms means coupled to the limiting means for inversely transforming the limit time domain signals into a plurality of second modulated signals in the frequency domain; means coupled to the second transform means for adjusting the phase and/or amplitude of some of the second modulated signals to provide a plurality of adjusted signals; and third transform means coupled to the adjusting means for transforming the adjusting signals from the frequency domain to the time domain to provide second time domain signals for transmission.
Claim 5
Dependent Claim
23 words
A transmitter according to claim 2, in which the adjusting means resets the phases of at least some of the second modulated signals.
Claim 6
Dependent Claim
19 words
A transmitter according to claim 2, in which the adjusting means filters out some of the second modulated signals.
Claim 7
Dependent Claim
43 words
A transmitter according to claim 2, in which there are more first time domain signals than there are first modulated signals, and the adjusting means reduces the amplitude of some of the second modulated signals which do not correspond to first modulated signals.
Claim 8
Dependent Claim
32 words
A transmitter according to claim 2, in which the modulating means, first transform means, limiting means, second transform means, adjusting means, and third transform means, operate on successive groups of data bits.
Claim 9
Dependent Claim
32 words
A transmitter according to claim 6, in which the periodicity of the said successive groups, in T S , and the spacing of the carriers is 1/T S or a multiple thereof.
Claim 10
Dependent Claim
20 words
A transmitter according to claim 2, in which the modulating means is a quadrature phase shift keying or 4-PSK modulator.
Claim 11
Dependent Claim
30 words
A transmitter according to claim 2, in which the second transform means transforms with a Fourier transform, and the first and third transform means transform with an inverse Fourier transform.
Claim 12
Dependent Claim
31 words
A transmitter according to claim 2, in which the limiting means, second transform means, adjusting means, and third transform means are repeated one or more than to provide an iterative operation.
Claim 13
Dependent Claim
21 words
A transmitter according to claim 2, in which the modulation means modulates in accordance with a phase shift keying modulation method.
Claim 14
Independent Claim
108 words
A method of transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising the steps of: modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals; reversibly encoding the modulated signals by an encoding function to provide encoded signals; subjecting the encoded signals to a predetermined function to provide modified encoded signals; decoding the modified encoded signals to provide decoded signals; adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals; and recording the adjusted signals by the said encoding function to provide encoded output signals for transmission.
Claim 15
Independent Claim
108 words
A method of transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising the steps of: modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals; reversibly encoding the modulated signals by an encoding function to provide encoded signals; subjecting the encoded signals to a predetermined function to provide modified encoded signals; decoding the modified encoded signals to provide decoded signals; adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals; and recording the adjusted signals by the said encoding function to provide encoded output signals for transmission.
Claim 16
Dependent Claim
160 words
Apparatus for transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising: input means for receiving a digital data stream for transmission; means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals; encoding means coupled to the modulating means for reversibly encoding the modulated signals by an encoding function to provide encoded signals; means coupled to the encoding means for subjecting the encoded signals to a predetermined function to provide modified encoded signals; decoding means coupled to the function subjecting means for decoding the modified encoded signals to provide decoded signals; means coupled to the decoding means for adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals; and recoding means coupled to the adjusting means for recoding the adjusted signals by the said encoding function to provide encoded output signals for transmission.
Claim 17
Dependent Claim
160 words
Apparatus for transmitting a digital data stream on a many-carrier frequency-division-multiplex signal, comprising: input means for receiving a digital data stream for transmission; means coupled to the input means for modulating a plurality of carriers with respective bits of the digital data to provide a plurality of modulated signals; encoding means coupled to the modulating means for reversibly encoding the modulated signals by an encoding function to provide encoded signals; means coupled to the encoding means for subjecting the encoded signals to a predetermined function to provide modified encoded signals; decoding means coupled to the function subjecting means for decoding the modified encoded signals to provide decoded signals; means coupled to the decoding means for adjusting at least some of the decoded signals to conform more closely with the modulated signals and provide adjusted signals; and recoding means coupled to the adjusting means for recoding the adjusted signals by the said encoding function to provide encoded output signals for transmission.
Claim 18
Dependent Claim
25 words
Apparatus according to claim 13, in which the means for subjecting the encoded signals to a predetermined function comprises means for limiting the encoded signals.
Claim 19
Dependent Claim
34 words
Apparatus according to claim 13, in which the decoding means comprises transform means for transforming the modified encoded signals from the time domain into a large number of decoded signals in the frequency domain.
Claim 20
Dependent Claim
32 words
Apparatus according to claim 13, in which the means for adjusting at least some of the decoded signals comprises means for adjusting the phase and/or amplitude of some of the decoded signals.
Claim 21
Dependent Claim
25 words
Apparatus according to claim 13, in which the recording means comprises means for transforming the adjusted signals from the frequency domain to the time domain.
References Cited (Backward Citations)
US4495620A
Cited
WO1986007223A1
Cited
US4881241A
Cited
EP0441730A1
Cited
EP0499560A1
Cited
EP0553841A2
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 2000-03-10 | 2000-09-09 | 2001-03-11 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2004-03-10 | 2004-09-09 | 2005-03-11 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2008-03-10 | 2008-09-09 | 2009-03-11 | $7700.00 | Window Closed / Lapsed |