Multiple carrier transmission in common-wave networks
First Claim
Patent Images
1. An apparatus used in a transmitter and/or receiver for multiple carrier modulated (OFDM modulated) digitally coded data,comprising at the transmitter side:
- means for generating a time sequence of OFDM symbols;
means for patterning said generated OFDM symbols into successive OFDM transmission frames, with each OFDM transmission frame being comprised of a frame head with one or several control symbols and an information data range with a plurality of data symbols, and with guard intervals preceding said data symbols; and
comprising at the receiver side;
means for extracting said data symbols and said control symbols from the received OFDM symbols;
means for synchronizing the received OFDM symbols in response to the time length of said guard intervals;
whereina predetermined means provided at the transmitter side and at the receiver side for selecting in each OFDM transmission frame the time length of the guard intervals for said symbols to be shorter than the time length of the guard intervals for said control symbols.
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Abstract
In order to prevent wanted signal capacity from being reduced during OFDM modulation of digital coded data, control symbol protecting intervals in the frame head of each OFDM transmission frame are larger than data symbol protecting intervals in wanted data areas of each OFDM transmission frame. The length of data symbol protecting intervals is determined during demodulation and data symbol scanning times are then determined on the thus determined length of the protecting intervals.
171 Citations
11 Claims
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1. An apparatus used in a transmitter and/or receiver for multiple carrier modulated (OFDM modulated) digitally coded data,
comprising at the transmitter side: -
means for generating a time sequence of OFDM symbols; means for patterning said generated OFDM symbols into successive OFDM transmission frames, with each OFDM transmission frame being comprised of a frame head with one or several control symbols and an information data range with a plurality of data symbols, and with guard intervals preceding said data symbols; and comprising at the receiver side; means for extracting said data symbols and said control symbols from the received OFDM symbols; means for synchronizing the received OFDM symbols in response to the time length of said guard intervals; wherein a predetermined means provided at the transmitter side and at the receiver side for selecting in each OFDM transmission frame the time length of the guard intervals for said symbols to be shorter than the time length of the guard intervals for said control symbols. - View Dependent Claims (2, 3)
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4. A method for multiple carrier modulation (OFDM modulation) of digitally coded data comprising the steps of:
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generating a time sequence of OFDM symbols which are patterned into successive OFDM transmission frames, each OFDM transmission frame having a frame head with at least one control symbol and a useful data range for a plurality of data symbols; providing a guard interval between successive control symbols and data symbols; and selecting the guard interval between said successive control symbols in said frame head to be larger than guard intervals between said successive data symbols in said useful data range of each transmission frame. - View Dependent Claims (5, 6, 7)
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8. A method for multiple carrier modulation (OFDM modulation) of digitally coded data comprising the steps of:
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modulating a plurality of orthogonal carriers in a frequency range by digitally coded OFDM symbols; synthesizing a time signal, which is periodic with a duration of TA using an inverse Fourier transform; storing the synthesized periodic time signal; converting the periodic time signal to an analog signal; selecting a duration TS of a symbol, which is larger than the periodic duration TA of the time signal such that TG =TS -TA, where TG is a guard interval duration; and transmitting said analog signal for the symbol duration over a channel. - View Dependent Claims (9)
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10. A method for multiple carrier demodulation (OFDM demodulation) of digitally coded OFDM modulated symbols received over a channel comprising the steps of:
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roughly synchronizing an OFDM transmission frame having a plurality of OFDM symbols; scanning a received time signal of a first transmitted OFDM symbol for a cycle duration; analyzing said received time signal in a frequency range using a Fourier transformation; demodulating individual orthogonal carriers in the frequency range; finely synchronizing said OFDM transmission frame by computation of a pulse response of the channel; determining amplitude and phase of the individual orthogonal carriers; and scanning subsequent transmitted OFDM symbols delayed by guard interval durations for respective transmitted OFDM symbols as a function of position of the respective transmitted OFDM symbol in the OFDM transmission frame, said guard interval durations being predetermined for control symbols and for data symbols. - View Dependent Claims (11)
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Specification