Spread spectrum transmitter and spread spectrum receiver

• US 7,095,778 B2
• Filed: 01/02/2003
• Issued: 08/22/2006
• Est. Priority Date: 01/18/2002
• Status: Expired due to Fees

• Current Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Original Assignee: Mitsubishi Denki Kabushiki Kaisha (Mitsubishi Electric Corporation)
• Inventors: Uchiki, Tatsuya, Okubo, Seiji, Kojima, Toshiharu
• Primary Examiner(s): Ghebretinsae, Temesghen
• Application Number:
  US10/334,947
• Publication Number:
  US 20030138031A1
• Time in Patent Office: 1,328 Days
• Field of Search: 375/130, 375/146, 375/147, 375/140, 375/295, 375/316, 375/341, 375/308, 375/329, 375/279
• US Class Current: 375/130
• CPC Class Codes: H04B 1/70752 Partial correlation
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker

Abstract

A spread spectrum transmitter provides delays having different magnitudes to spread spectrum (SS) signals for a plurality of channels, and multiplexes the SS signals to generate transmission multiplex SS signal. A spread spectrum receiver calculates a partial correlation value between the transmission multiplex SS signal and spreading codes multiplied to the SS signals, multiplies the partial correlation values by a prescribed matrix prepared based on each orthogonal code sequence to calculate a plurality of orthogonal correlation values. The receiver identifies for a respective channel each parallel data sequence related in advance to an orthogonal code sequence whose orthogonal correlation value is a maximum, corrects delay differences of the parallel data sequences, and then performs sampling and parallel-serial conversion to obtain a serial demodulated data sequence.

Claims

1. A spread spectrum transmitter comprising:

a serial-parallel converting unit that inputs an information signal, sequentially converts the information signal into parallel data sequences of a prescribed data length, and sequentially distributes the parallel data sequences to N channels, where N is 2 or greater natural number;

an orthogonal sequence encoding unit that sequentially converts the parallel data sequences into prescribed orthogonal code sequences;

a spreading modulating unit that performs a spectrum spreading modulation process by respectively multiplying the orthogonal code sequences by prescribed spreading codes to output N spread spectrum signals;

a delay unit that provides delays having different magnitudes to the N spread spectrum signals;

a multiplexing unit that multiplexes the N spread spectrum signals in a prescribed manner to generate a transmission multiplex spread spectrum signal; and

a transmitting unit that performs prescribed signal processing for transmitting the transmission multiplex spread spectrum signal.

2. The spread spectrum transmitter according to claim 1, further comprising a phase-shifting unit that phase-shifts the spread spectrum signals by respective prescribed phase-shift amounts.

3. The spread spectrum transmitter according to claim 1, wherein

the serial-parallel converting unit determines a data length of the parallel data sequences as K+P bits, where K and P are natural numbers, and

the orthogonal sequence encoding unit is configured to sequentially convert K-bit data of the parallel data sequences into prescribed orthogonal code sequences,

the spread spectrum transmitter further comprising a phase-shift keying (PSK) modulating unit that phase-shifts the orthogonal code sequences by prescribed phase-shift amounts for PSK modulation determined depending on P-bit data of the parallel data sequences.

4. The spread spectrum transmitter according to claim 1, wherein

the serial-parallel converting unit determines a data length of the parallel data sequences as K+P bits, where K and P are natural numbers,

the spread spectrum transmitter further comprising a phase-shift keying (PSK) modulating unit that phase-shifts K-bit data of the parallel data sequences by prescribed phase-shift amounts for PSK modulation determined depending on P-bit data of the parallel data sequences, wherein

the orthogonal sequence encoding unit is configured to sequentially convert the K-bit data after the PSK modulation into prescribed orthogonal code sequences.

5. The spread spectrum transmitter according to claim 1, wherein the orthogonal sequence encoding unit is configured to employ Walsh sequences as the orthogonal code sequences.

6. A spread spectrum receiver comprising:

a partial correlation calculating unit that holds partial spreading codes obtained by dividing spreading codes employed in a spread spectrum transmitter by a bit number J of orthogonal code sequences, and calculates partial correlation values between a transmission multiplex spread spectrum signal transmitted from the spread spectrum transmitter and the partial spreading codes, the spread spectrum transmitter including

a serial-parallel converting unit that inputs an information signal, sequentially converts the information signal into parallel data sequences of a prescribed data length, and sequentially distributes the parallel data sequences to N channels, where N is 2 or greater natural number,

an orthogonal sequence encoding unit that sequentially converts the parallel data sequences into prescribed orthogonal code sequences,

a spreading modulating unit that performs a spectrum spreading modulation process by respectively multiplying the orthogonal code sequences by prescribed spreading codes to output N spread spectrum signals,

a delay unit that provides delays having different magnitudes to the N spread spectrum signals,

a multiplexing unit that multiplexes the N spread spectrum signals in a prescribed manner to generate a transmission multiplex spread spectrum signal, and

a transmitting unit that performs prescribed signal processing for transmitting the transmission multiplex spread spectrum signal;

an inverse matrix multiplying unit that holds an inverse matrix of an orthogonal code matrix having the orthogonal code sequences employed in the spread spectrum transmitter as row elements of the orthogonal code sequences, and multiplies the inverse matrix by a column vector consisting of the partial correlation values to calculate orthogonal correlation values respectively corresponding to the orthogonal code sequences;

a most-likelihood deciding/demodulating unit that identifies an orthogonal code sequence having an orthogonal correlation value as a maximum, to output a parallel data sequence related in advance to the orthogonal code sequence, as a demodulated parallel data sequence, to a respective one of N channels;

a delay difference correcting unit that corrects delay differences of the demodulated parallel data sequences of the channels depending on delay amounts provided to the spread spectrum signals in the channels of the spread spectrum transmitter; and

a demodulation data converting unit that samples the demodulated parallel data sequences after delay difference correction depending on a reproduced symbol clock synchronized to a cyclic period of spreading code of the transmission multiplex spread spectrum signal, and parallel-serial converts the sampled data of the channels to obtain a serial demodulated data sequence.

7. The spread spectrum receiver according to claim 6, further comprising:

a phase correcting unit that identifies a data reception timing for a respective channel delay-multiplexed depending on a prescribed data extraction timing of the reproduced symbol clock and a delay amount provided to the spread spectrum signal of the channel,

calculates a phase correction amount to cancel a phase-shift amount of the spread spectrum signal of the respective channel that is phase-shifted in the spread spectrum transmitter, the spread spectrum transmitter further including a phase-shifting unit that phase-shifts the spread spectrum signals by respective prescribed phase-shift amounts, and

respectively corrects phases of the orthogonal correlation values, depending on a phase correction amount corresponding to each of the channels, at the data reception timing of the channel.

8. The spread spectrum receiver according to claim 6 for receiving the transmission multiplex spread spectrum signal transmitted from the spread spectrum transmitter, the spread spectrum transmitter being configured such that

the serial-parallel converting unit determines a data length of the parallel data sequences as K+P bits, where K and P are natural numbers, and

the orthogonal sequence encoding unit sequentially converts K-bit data of the parallel data sequences into prescribed orthogonal code sequences,

the spread spectrum transmitter further includes a phase-shift keying (PSK) modulating unit that phase-shifts the orthogonal code sequences by prescribed phase-shift amounts for PSK modulation determined depending on P-bit data of the parallel data sequences,

wherein the most-likelihood deciding/demodulating unit includes

an absolute value calculating unit that respectively calculates absolute values of the orthogonal correlation values, and

a maximum value deciding/PSK demodulating unit that identifies an orthogonal correlation value having an absolute value as a maximum, identifies K-bit data related in advance to the orthogonal correlation value in the spread spectrum transmitter, as demodulated K-bit data, PSK-demodulates a phase of the identified orthogonal correlation value, and obtains demodulated P-bit data to generate demodulated parallel data sequences each consisting of the demodulated K-bit data and the demodulated P-bit data.

9. The spread spectrum receiver according to claim 6 for receiving the transmission multiplex spread spectrum signal transmitted from the spread spectrum transmitter, the spread spectrum transmitter wherein

the serial-parallel converting unit determines a data length of the parallel data sequences as K +P bits, where K and P are natural numbers,

the spread spectrum transmitter further including a phase-shift keying (PSK) modulating unit that phase-shifts K-bit data of the parallel data sequences by prescribed phase-shift amounts for PSK modulation determined depending on P-bit data of the parallel data sequences, wherein

the orthogonal sequence encoding unit is configured to sequentially convert the K-bit data after the PSK modulation into prescribed orthogonal code sequences,

wherein the most-likelihood deciding/demodulating unit includes

an absolute value calculating unit that respectively calculates absolute values of the orthogonal correlation values, and

a maximum value deciding/PSK demodulating unit that identifies an orthogonal correlation value having an absolute value as a maximum, identifies K-bit data related in advance to the orthogonal correlation value in the spread spectrum transmitter, as demodulated K-bit data, PSK-demodulates a phase of the identified orthogonal correlation value, and obtains demodulated P-bit data to generate demodulated parallel data sequences each consisting of the demodulated K-bit data and the demodulated P-bit data.

10. The spread spectrum receiver according to claim 6, wherein the inverse matrix multiplying unit is configured to hold an inverse matrix of an orthogonal code matrix having orthogonal code sequences of Walsh sequences as row elements of the orthogonal code sequences.