Diversity in orthogonal frequency division multiplexing systems
AssigneeLucent Technologies Inc.
InventorsVijitha Weerackody, Zulfiquar Sayeed
Life of this patent
Estimating the term…
Abstract
A system and method is disclosed for improving diversity in a multiple transmitter or multiple receiver orthogonal frequency division multiplexing (OFDM) system. Signal diversity is improved by introducing phase offsets at the transmitters and/or the receivers. The phase offsets are unique to each transmitter or receiver. The unique phase offsets are applied to individual symbols of the OFDM signal in the frequency domain.
Claims27
A method for improving diversity in a multiple transmitter orthogonal frequency division multiplexing system, comprising the steps of:
- receiving a data signal at a first transmitter and a second transmitter;
- processing said data signal at said first transmitter and at said second transmitter to generate a plurality of differentially encoded complex symbols at said first and second transmitters;
- and
- introducing first phase offsets to said plurality of differentially encoded complex symbols at said first transmitter in the frequency domain to generate a first stream of transmit symbols;
- introducing second phase offsets to said plurality of differentially encoded complex symbols at said second transmitter in the frequency domain to obtain a second stream of transmit symbols;
- transforming said first and second streams of transmit symbols from the frequency domain to the time domain;
- and
- transmitting said first and second streams of transmit symbols in the time domain from said first and second transmitters, respectively, such that said first and second streams of transmit symbols at said first transmitter and at said second transmitter have unique phase offsets.
A method for transmitting a digital data signal on a frequency division multiplex system using at least two transmitters, each transmitter corresponding to a communication channel, the method comprising the steps of:
- applying a channel code to a digital signal to generate a sequence of sub-carrier symbols;
- applying first phase offsets to said sequence of sub-carrier symbols in the frequency domain at a first transmitter, said offsets unique to said first transmitter, to obtain a first sequence of phase offset symbols;
- applying second phase offsets to said sequence of sub-carrier symbols in the frequency domain at a second transmitter, said offsets unique to said second transmitter, to obtain a second sequence of phase offset symbols;
- a transforming said first and second sequence of phase offset symbols from the frequency domain to the time domain;
- and
- transmitting said first and second sequence of phase offset symbols in the time domain from said first and second transmitters, respectively, such that frequency diversity is increased in the frequency division multiplex system.
An orthogonal frequency division multiplexing transmission system for transmitting a data signal comprising:
- a plurality of transmitters (i), each of said transmitters comprising;
- a coder coupled to said data signal, said coder generating a differentially encoded complex signal comprising a plurality of complex symbols (n);
- a rotator coupled to said coder for introducing a phase offset in the frequency domain, said offset unique to each of said plurality of transmitters, to each of said plurality of complex symbols (n), wherein said phase offset is unique for each of said plurality of transmitters (i);
- an inverse Fourier transformer coupled to said rotator for transforming said differentially encoded complex signal from the frequency domain to the time domain to prepare said differentially encoded complex signal for transmitting;
- and
- wherein said transmitted plurality of differentially encoded complex signals are capable of being received by a single receiver.
An orthogonal frequency division multiplexing receiver system for receiving a data signal comprising:
- a plurality of receivers (i), each of said receivers comprising;
- a receiver circuit coupled to receive a differentially encoded complex data signal comprising a plurality of complex symbols (n);
- a Fourier transformer coupled to said receiver for transforming said differentially encoded complex signal from time domain to frequency domain;
- rotator coupled to said Fourier transformer for introducing a phase offset in the frequency domain, said offset unique to said each of said plurality of receivers, to each of said plurality of complex symbols (n), wherein said phase offset is unique for each of said plurality of receivers (i);
- and
- a combiner for combining said differentially encoded complex signal in the frequency domain after rotating;
- and
- a differential decoder for decoding said differentially encoded complex signal in the frequency domain after rotating and combining.
Dependencies are inferred from the claim text.