Spread spectrum communications system
First Claim
Patent Images
1. A data transmission system comprising a transmitter and a receiver,the transmitter comprising:
- converting means for converting transmission data into parallel data according to a symbol timing signal;
first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval;
first means for spreading the parallel data such that the parallel data is modulated based on π
/4-shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; and
transmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, andthe receiver comprising;
receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals;
second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively;
second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;
reproduction means for reproducing received data from the received despread data; and
recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data.
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Abstract
In a data transmission system, transmission data is modulated based on π/4-shift QPSK modulation according to two spreading code sequences which are generated according to a chip timing signal in each symbol interval. At a receiving side, the received spread spectrum signal is demodulated based on the same π/4-shift QPSK modulation according to the respective replicas of the spreading code sequences.
81 Citations
44 Claims
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1. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel data is modulated based on π
/4-shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel date is modulated based on π
/4-shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data; wherein the first means comprises; first phase shifting means for shifting a phase of the parallel data based on QPSK scheme according to the spreading code sequences at a chip rate of the chip timing signal to produce first quadrature spread spectrum signals; and second phase shifting means for shifting a phase of the first quadrature spread spectrum signals by one selected from 0 and π
/4 according to a first timing signal of one-half the chip rate synchronous with the chip timing signal. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel date is modulated based on π
/4 shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data; wherein the first means performs spectrum spreading of the parallel data such that the parallel data is mapped on a transmission signal constellation of π
/4-shift QPSK scheme according to respective logical levels of the spreading code sequences and the second timing signal of one-half the recovered chip rate synchronous with the recovered chip timing signal. - View Dependent Claims (14)
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15. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel date is modulated based on π
/4 shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data; wherein the second means comprises; third phase shifting means for shifting a phase of the received quadrature spread spectrum signals based on QPSK scheme at a recovered chip rate of the recovered chip timing signal according to the despreading code sequences to produce first quadrature despread data; and fourth phase shifting means for shifting a phase of the first quadrature despread data by one selected from 0 and -π
/4 according to a second timing signal of one-half the recovered chip rate synchronous with the recovered chip timing signal. - View Dependent Claims (16)
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17. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel date is modulated based on π
/4 shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data; wherein the second means comprises; third phase shifting means for shifting a phase of the received quadrature spread spectrum signals by one selected from 0 and -π
/4 according to the recovered chip timing signal and a second timing signal of one-half the recovered chip rate synchronous with the recovered chip timing signal, to produce phase-shifted quadrature spread spectrum signals;fourth phase shifting means for shifting a phase of the phase-shifted quadrature spread spectrum signals based on QPSK scheme at a recovered chip rate of the recovered chip timing signal according to the despreading code sequences to produce quadrature despread data; and accumulating means for accumulating the quadrature despread data in each symbol interval to produce the received despread data. - View Dependent Claims (18)
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19. A data transmission system comprising a transmitter and a receiver,
the transmitter comprising: -
converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel date is modulated based on π
/4 shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting means for transmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and the receiver comprising; receiving means for receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; converting means for converting the received quadrature spread spectrum signals into digital quadrature spread spectrum signals according to a recovered chip timing signal; second generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; recovery means for recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data; and wherein the second means comprises; third phase shifting means for shifting a phase of the digital quadrature spread spectrum signals based on QPSK scheme at a recovered chip rate of the recovered chip timing signal according to the despreading code sequences to produce first quadrature despread data; and fourth phase shifting means for shifting a phase of the first quadrature despread data by one selected from 0 and -π
/4 according to a second timing signal of one-half the recovered chip rate synchronous with the recovered chip timing signal. - View Dependent Claims (20, 21)
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22. A communication apparatus comprising a transmitter and a receiver,
the transmitter comprising: -
first converting means for converting transmission data into parallel data according to a symbol timing signal; first generating means for generating two spreading code sequences according to a chip timing signal in each symbol interval; first means for spreading the parallel data such that the parallel data is modulated based on π
/4-shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals;spectrum shaping means for spectrum-shaping the quadrature spread spectrum signals; analog converting means for converting the output signals of the spectrum shaping means into analog quadrature baseband signals; second converting means for converting the analog quadrature baseband signals to a radio transmission; and a transmission power amplifier for amplifying the radio transmission signal in power, and the receiving comprising; receiving means for receiving a radio transmission signal to produce received quadrature spread spectrum signals; converting means for converting the received quadrature spread spectrum signals into digital quadrature spread spectrum signals according to a recovered chip timing signal; replica generating means for generating two despreading code sequences which are replicas of the spreading code sequences, respectively; second means for despreading the digital quadrature spread spectrum signals such that the digital quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproduction means for reproducing received data from the received despread data; and recovery means for generating a recovered symbol timing signal and the recovered chip timing signal from the digital quadrature spread spectrum signals and the received data. - View Dependent Claims (23, 24)
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25. A method for transmitting data from a transmitter to a receiver, comprising the steps of:
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at the transmitter, converting transmission data into parallel data according to a symbol timing signal; generating two spreading code sequences according to a chip timing signal in each symbol interval; spreading the parallel data such that the parallel data is modulated based on π
/4-shift QPSK (quadrature phase shift keying) scheme according to the spreading code sequences to produce quadrature spread spectrum signals; andtransmitting a transmission signal which is generated based on the quadrature spread spectrum signals to the receiver, and at the receiver, receiving the transmission signal from the transmitter to produce received quadrature spread spectrum signals; generating two despreading code sequences which are replicas of the spreading code sequences, respectively; despreading the received quadrature spread spectrum signals such that the received quadrature spread spectrum signals are demodulated based on π
/4-shift QPSK scheme according to the despreading code sequences to produce received despread data;reproducing received data from the received despread data; and recovering a symbol timing signal and a chip timing signal from the received quadrature spread spectrum signals and the received data. - View Dependent Claims (26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42)
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43. A method for spreading transmission data in a CDMA system, comprising the steps of:
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converting the transmission data into an in-phase component and a quadrature component according to a symbol timing signal; generating an in-phase spreading code sequence and a quadrature spreading code sequence according to a chip timing signal in each symbol interval; and spreading the transmission data by phase-shifting the in-phase component and the quadrature component based on π
/4-shift QPSK scheme according to a combination of the in-phase spreading code sequence and the quadrature spreading code sequence.
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44. A method for despreading a spread spectrum signal in a CDMA system, comprising the steps of:
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converting the spread sprectrum signal into an in-phase digital component and a quadrature digital component according to a recovered chip timing signal; generating an in-phase despreading code sequence and a quadrature despreading code sequence according to the recovered chip timing signal in each symbol interval; and despreading the spread sprectrum signal by phase-shifting the in-phase digital component and the quadrature digital component based on π
/4-shift QPSK scheme according to a combination of the in-phase despreading code sequence and the quadrature despreading code sequence.
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Specification