Data transmission via multi-path channels using orthogonal multi-frequency signals with differential phase shift keying modulation
First Claim
1. A data communications system, for use over a multi-path channel, comprising:
- an orthogonal frequency division multiplexing (OFDM) sub-carrier signal generator that outputs a plurality of OFDM sub-carrier signals;
a differential quadrature phase shift keying (DQPSK) modulator that modulates each OFDM sub-carrier signal of the plurality of OFDM sub-carrier signals in response to input data, and forms a plurality of modulated OFDM sub-carrier signals in response to the input data;
a summer that combines the plurality of modulated OFDM sub-carrier signals to form a transmitted signal;
a receiver to output a received signal in response to the transmitted signal transmitted through the multi-path channel, the received signal having a missing sub-carrier signal at a center frequency located in the middle of a frequency spectrum of the received signal, the missing sub-carrier signal having zero amplitude;
an OFDM sub-carrier reference generator that outputs a plurality of OFDM sub-carrier reference signals, the plurality of OFDM sub-carrier reference signals including an OFDM sub-carrier reference signal located at the center frequency;
a non-coherent synchronizer that synchronizes an OFDM symbol interval to a demodulating interval by nulling a correlation between the received signal and the OFDM sub-carrier reference signal located at the center frequency; and
a demodulator, using a DQPSK multi-carrier detector, that demodulates the received signal to form an output signal.
1 Assignment
0 Petitions
Accused Products
Abstract
A method and an apparatus relating to an OFDM data communications system where the sub-carriers are modulated using differential quadrature phase-shift keying (DQPSK). The multi-carrier transmitted signal is directly generated by means of summation of pre-computed sample points. As part of the multi-carrier signal generation, a signal for the guard interval is established. In an acoustic application of this approach, direct radiation of the sub-carrier approach is facilitated. Symbol synchronization in the receiver is based on signal correlation with the missed sub-carrier. Separation of the sub-carriers in the receiver by means of correlation of the received signal and reference signals that are derived from a table of pre-computed values. Optimal non-coherent processing of the sub-carriers without any phase tracking procedures is achieved.
-
Citations
18 Claims
-
1. A data communications system, for use over a multi-path channel, comprising:
-
an orthogonal frequency division multiplexing (OFDM) sub-carrier signal generator that outputs a plurality of OFDM sub-carrier signals; a differential quadrature phase shift keying (DQPSK) modulator that modulates each OFDM sub-carrier signal of the plurality of OFDM sub-carrier signals in response to input data, and forms a plurality of modulated OFDM sub-carrier signals in response to the input data; a summer that combines the plurality of modulated OFDM sub-carrier signals to form a transmitted signal; a receiver to output a received signal in response to the transmitted signal transmitted through the multi-path channel, the received signal having a missing sub-carrier signal at a center frequency located in the middle of a frequency spectrum of the received signal, the missing sub-carrier signal having zero amplitude; an OFDM sub-carrier reference generator that outputs a plurality of OFDM sub-carrier reference signals, the plurality of OFDM sub-carrier reference signals including an OFDM sub-carrier reference signal located at the center frequency; a non-coherent synchronizer that synchronizes an OFDM symbol interval to a demodulating interval by nulling a correlation between the received signal and the OFDM sub-carrier reference signal located at the center frequency; and a demodulator, using a DQPSK multi-carrier detector, that demodulates the received signal to form an output signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
-
-
9. A data receiver, for use over a multi-path channel, comprising:
-
a receiver to output a received signal in response to a transmitted signal transmitted through the multi-path channel, the received signal having a missing sub-carrier signal at a center frequency located in the middle of a frequency spectrum of the received signal, the missing sub-carrier signal having zero amplitude; an orthogonal frequency division multiplexing (OFDM) sub-carrier reference generator that outputs a plurality of OFDM sub-carrier reference signals, the plurality of OFDM sub-carrier reference signals including an OFDM sub-carrier reference signal located at the center frequency; a non-coherent synchronizer that synchronizes an OFDM symbol interval to a demodulating interval by nulling a correlation between the received signal and the OFDM sub-carrier reference signal located at the center frequency; and a demodulator, using a differential quadrature phase shift keying (DQPSK) multi-carrier detector, that demodulates the received signal to form an output signal. - View Dependent Claims (10, 11, 12, 13)
-
-
14. A method for data communications, comprising:
-
receiving a received signal via a channel, the received signal having a missing sub-carrier signal at a center frequency located in the middle of a frequency spectrum of the received signal, the missing sub-carrier signal having zero amplitude; generating a plurality of orthogonal frequency division multiplexing (OFDM) sub-carrier reference signals, the plurality of OFDM sub-carrier reference signals including an OFDM sub-carrier reference signal located at the center frequency; non-coherently synchronizing an OFDM symbol interval and a demodulating interval by nulling a correlation between the received signal and the OFDM sub-carrier reference signal located at the center frequency; and demodulating, using a DQPSK multi-carrier detector, the received signal to form an output signal, wherein the generating, synchronizing and demodulating are performed by one or more circuits. - View Dependent Claims (15, 16, 17, 18)
-
Specification