Spread spectrum communication system

• US 5,960,028 A
• Filed: 08/07/1996
• Issued: 09/28/1999
• Est. Priority Date: 08/11/1995
• Status: Expired due to Fees

• Current Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Original Assignee: Sharp Kabushiki Kaisha (Hon Hai Precision Industry Co., Ltd.)
• Inventors: Kubota, Minoru, Okamoto, Naoki, Hamaguchi, Yasuhiro
• Primary Examiner(s): Chin, Stephen
• Assistant Examiner(s): Roundtree, Joseph
• Application Number:
  US08/689,412
• Time in Patent Office: 1,147 Days
• Field of Search: 342/58, 342/86-87, 342/92, 370/206, 370/208-209, 370/335, 370/479, 375/200, 375/206, 375/208-209, 375/340, 375/343, 455/65, 455/67.3, 455/67.6, 455/276.1, 455/279.1, 455/422, 455/562
• US Class Current: 375/130
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7097 Interference-related aspects
• CPC Class Codes: H04B 1/7107 Subtractive interference cancellation
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence
• CPC Class Codes: H04J 13/0022 PN, e.g. Kronecker
• CPC Class Codes: H04J 13/0077 Multicode, e.g. multiple codes assigned to one user
• CPC Class Codes: H04J 13/10 Code generation

Abstract

A transmitter of a spread spectrum communication system includes a data generating portion, a differential coding portion, an S/P converting portion, multipliers, PN generator, a local signal generator, modulators, delay elements, combiner, a frequency converting portion, a power amplifying portion and a transmission antenna. Parallel signals are multiplied by a spread code from the PN generator, and the results are delayed by delay elements and multiplexed. Time difference between the delay times are set to an arbitrarily time period of at least 1 chip from each other. Therefore, error rate characteristics can be improved, and degradation of correlated output is suppressed, whereby difficulty in demodulation can be avoided.

Claims

1. A spread spectrum communication apparatus, comprising:

serial/parallel converting means for converting a data sequence into a plurality of parallel signals;

spread code generating means for generating a spread code;

multiplying means for multiplying the plurality of parallel signals converted by said serial/parallel converting means by the spread code generated from said spread code generating means to generate a plurality of spread signals;

modulating means for modulating the plurality of spread signals output from said multiplying means to generate a plurality of intermediate frequency signals;

delay means, having a plurality of different delay times, for delaying the plurality of intermediate frequency signals generated from said modulating means by said plurality of different delay times, to generate a plurality of delayed signals; and

transmission signal output means for combining the plurality of delayed signals output from said delay means and for transmitting the combined delayed signals as a transmission signal,

said plurality of different delay times having an arbitrary time difference of at least 1 chip from each other.

5. The spread spectrum communication apparatus according to any of claims 1 to 4, further comprising:

differential coding means provided in a preceding stage of said serial/parallel converting means for differentially encoding said data sequence; and

receiving means, including demodulating means, for receiving and performing demodulation of said transmission signal,

said demodulating means including

differential decoding means for performing differential decoding of a signal based on the received transmission signal to generate a differential decoded signal having a time spread, and

integrating means for integrating the differential decoded signal generated from said differential decoding means in a prescribed time range.

6. The spread spectrum communication apparatus according to any of claims 1 to 4, further comprising:

parallel/delay control means for setting a number of the plurality of parallel signals to be output from said serial/parallel converting means and for setting said plurality of different delay times of said delay means in accordance with environment of use.

7. The spread spectrum communication apparatus according to any of claims 1 to 4, comprising:

data generating means for generating said data sequence with data rate varied in accordance with information content; and

parallel/delay control means for setting a number of the plurality of parallel signals to be output by said serial/parallel converting means and said plurality of different delay times of said delay means such that constant symbol rate is maintained regardless of variation of said data rate.

8. The spread spectrum communication apparatus according to any of claims 1 to 3, further comprising

means for setting said plurality of delay times such that adjacent ones of the plurality of delayed signals have constant time difference.

2. A spread spectrum communication apparatus, comprising:

serial/parallel converting means for converting a data sequence into a plurality of parallel signals;

spread code generating means for generating a spread code;

multiplying means for multiplying the plurality of parallel signals converted by said serial/parallel converting means by the spread code generated from said spread code generating means, to generate a plurality of baseband spread signals;

delay means, having a plurality of different delay times, for delaying said plurality of baseband spread signals by said plurality of different delay times to generate a plurality of delayed signals; and

transmission signal output means for combining and outputting as a transmission signal the plurality of delayed signals delayed by said delay means,

said plurality of different delay times having an arbitrary time difference of at least 1 chip from each other.

3. A spread spectrum communication apparatus, comprising:

serial/parallel converting means for converting a data sequence into a plurality of parallel signals that are baseband;

first delay means, having a plurality of different delay times, for delaying the plurality of parallel signals converted by said serial/parallel converting means by said plurality of different delay times to generate a plurality of delayed signals that are parallel;

spread code generating means for generating a spread code;

second delay means, having a same plurality of different delay times as said plurality of different delay times, for delaying the spread code generated from said spread code generating means by said plurality of different delay times to generate a plurality of delayed spread codes;

multiplying means for multiplying the plurality of delayed signals generated from said first delay means by the plurality of delayed spread codes output from said second delay means, to generate a plurality of spread signals; and

transmission signal output means for combining and outputting as a transmission signal the plurality of spread signals output from said multiplying means,

said multiplying means multiplying delayed signals and delayed spread codes having the same delay times, and

said plurality of different delay times having an arbitrary time difference of at least 1 chip from each other.

4. A spread spectrum communication apparatus, comprising:

serial/parallel converting means for converting a data sequence into a plurality of parallel signals;

latch means for latching said plurality of parallel signals to generate a plurality of latch signals;

spread code generating means for generating a spread code;

delay means, having a plurality of different delay times, for delaying the spread code generated from said spread code generating means by said plurality of different delay times to generate a plurality of delayed spread codes;

multiplying means for multiplying the plurality of latch signals latched in said latch means by the plurality of delayed spread codes output from said delay means, to generate a plurality of delayed spread signals;

transmission signal output means for combining and outputting as a transmission signal the plurality of delayed spread signals generated by said multiplying means; and

latch control means for generating a plurality of latch control signals which have the same timing as start chips of corresponding ones of the plurality of delayed spread codes,

said latch means latching the plurality of parallel signals converted by said serial/parallel converting means in accordance with said plurality of latch control signals, whereby timings of said plurality of latch control signals and timings of the plurality of delayed spread codes output from said multiplying means are matched, and

said plurality of different delay times having an arbitrary time difference of at least 1 chip from each other.

9. A spread spectrum communication apparatus for transmission/reception using spread spectrum communication in such a data format that has a known data portion at a preamble portion, comprising:

correlating means for correlating a reception signal and a predetermined code;

detecting means for detecting the known data portion from a signal correlated by said correlating means;

known data portion output means for outputting in advance a correlated output of the known data portion; and

delay profile calculating means for outputting a correlated signal at a time of actual measurements of said detecting means based on a detection signal from said detecting means, for comparing the output correlated signal with the correlated output from said known data portion output means, and for generating a delay profile indicating a state of the signal correlated by said correlating means.

10. The spread spectrum communication apparatus according to claim 9, further comprising:

delay spread calculating means for calculating delay spread from the delay profile generated by said delay profile calculating means, to generate various delay characteristics from the calculated delay spread based on a predetermined theoretical expression.

11. The spread spectrum communication apparatus according to claim 9, further comprising:

integrating means for integrating at every spread period timing a difference signal between two signals compared by said delay profile calculating means and for providing the integrated difference signal as the delay profile.

12. The spread spectrum communication apparatus according to claim 9, further comprising:

filter means for filtering, at a same spread period timing, a difference signal between two signals compared by said delay profile calculating means and for providing the filtered difference signal as the delay profile.

13. A spread spectrum communication apparatus for transmission/reception using spread spectrum communication in such a data format that has a known data portion at a preamble portion, comprising:

correlating means for correlating a reception signal with a predetermined code;

detecting means for detecting the known data portion from the signal correlated by said correlating means;

delay profile calculating means for calculating a delay profile indicating a state of a delay signal from the known data portion detected by said detecting means; and

means for determining setting of path diversity based on the delay profile calculated by said delay profile calculating means.

14. A spread spectrum communication apparatus for transmission/reception using spread spectrum communication in such a data format that has a known data portion at a preamble portion, comprising:

correlating means for correlating a reception signal with a predetermined code;

detecting means for detecting the known data portion from the signal correlated by said correlating means;

delay profile calculating means for calculating a delay profile indicating a state of a delay signal from the known data portion detected by said detecting means; and

means for determining setting of a multipath canceler from the delay profile calculated by said delay profile calculating means.

15. The spread spectrum communication apparatus according to claim 14, wherein

said means for determining setting of a multipath canceler includes subtracting means for calculating a signal component at a delay amount corresponding to a data demodulation timing of the delay profile calculated by said delay profile calculating means in accordance with a demodulating data component and subtracting the calculated signal component from a correlated output of a timing portion of the reception signal used for demodulation of data other than the known data portion, based on the detection signal from said detecting means.

16. The spread spectrum communication apparatus according to claim 15, further comprising:

storing means for storing a reference value for determining whether subtraction is to be performed or not,

said subtracting means does not subtract the calculated signal component from the correlated output when the calculated signal component is smaller than the reference value stored in said storing means.

17. The spread spectrum communication apparatus for transmission/reception using spread spectrum communication in such a data format that has a known data portion at a preamble portion, comprising:

correlating means for correlating a reception signal with a predetermined code;

detecting means for detecting the known data portion from the signal correlated by said correlating means;

known data portion output means for outputting in advance a correlated output of the known data portion;

delay profile calculating means for calculating a delay profile indicating a state of a delay signal from the correlated output of said known data portion output means; and

modulating/demodulating means for delaying, combining and multiplexing the signal correlated by said correlating means, for determining a number of multiplexing and an amount of delay based on the delay profile output from said delay profile calculating means.

18. The spread spectrum communication apparatus according to claim 17, further comprising:

interference amount storing means for storing in advance an amount of interference corresponding to an error rate required in a communication link,

said modulating/demodulating means calculating an amount of interference at a data transmission timing based on a calculated value of the delay profile and selecting a number of multiplexing and an amount of delay which are optimal and not exceeding the amount of interference stored in said interference amount storing means.

20. The spread spectrum communication apparatus according to claim 17, wherein

the number of multiplexing and the amount of delay determined by said modulating/demodulating means are transmitted as information inserted into a specific data portion to be multiplexed, and

the number of multiplexing and the amount of delay are identified in the specific data portion, and demodulation is performed accordingly.

21. The spread spectrum communication apparatus according to claim 20, wherein

the spread spectrum communication apparatus is a system allowing bidirectional communication, and

determination and insertion of the number of multiplexing and the amount of delay into the specific data portion are performed in one direction, and the number of multiplexing and the amount of delay are the same in both directions of communication.

19. A spread spectrum communication apparatus for transmission/reception using spread spectrum communication in such a data format that has a known data portion at a preamble portion, comprising:

correlating means for correlating a reception signal with a predetermined code;

detecting means for detecting the known data portion from the signal correlated by said correlating means;

known data portion output means for outputting in advance a correlated output of the known data portion; and

modulating/demodulating means for not performing multiplexing of the known data portion output from said known data portion output means and a subsequent specific data portion, and for multiplexing by delaying and combining the signal correlated by said correlating means at a subsequent specific portion.

22. A spread spectrum communication apparatus in which an arbitrary number of delay waves delayed by an arbitrary number of chips with respect to a spread signal are multiplexed on a transmitting side, a modulated data obtained by differential decoding of data of continuous delay waves is received, comprising:

detecting means for estimating phase difference caused by frequency offset between transmission and reception; and

compensating means for providing compensation with demodulated data in accordance with the amount of delay of each of the multiplexed delay waves in accordance with detected correlation peak and phase difference estimated by said detecting means.

23. A spread spectrum communication apparatus, comprising:

correlating means for detecting a correlation peak value of each wave of multiplexed spread signals;

correlation peak period detecting means for detecting a period of correlation peak value of each wave of the multiplexed spread signals based on an output from said correlating means;

differential demodulating means for differentially demodulating the output from said correlating means to output data;

demodulated data rotating means for rotating a phase of the data output by said differential demodulating means;

phase difference detecting means for extracting a phase difference of each wave of the multiplexed spread signals based on a signal from said differential demodulating means; and

means, responsive to detection of the periods of the correlation peak value by said correlation peak period detecting means, for estimating a mean value of phase difference of each wave of the multiplexed spread signals based on the phase difference extracted by said phase difference detecting means and for controlling rotation of the data by said demodulated data rotating means.

24. The spread spectrum communication apparatus according to claim 23, wherein said means for estimating comprises:

phase difference estimating means for estimating the mean value of phase difference of each wave of the multiplexed spread signals based on the phase difference extracted by said phase difference extracting means; and

operating means, controlled in accordance with an output from said correlation peak period detecting means, for multiplying the mean value of phase difference estimated by said phase difference detecting means by a coefficient in accordance with an amount of delay, to compensate for demodulated data output from said demodulated data rotating means.

25. The spread spectrum communication apparatus according to claim 23, wherein said means for estimating comprises:

first switching means for switching dependent on whether the correlation peak value detected by said correlation peak period detecting means is a first value or a second value;

first phase difference estimating means, responsive to switching of said first switching means when the correlation peak value is the first value, for estimating the mean value of phase difference of each wave of the multiplexed spread signal extracted by said phase difference determining means;

second phase difference estimating means, responsive to switching of said first switching means when the correlation peak value is the second value, for estimating the mean value of phase difference of each wave of the multiplexed spread signal extracted by said phase difference determining means; and

second switching means, switched dependent on whether the correlation peak value detected by said correlation peak period detecting means is the first value or the second value, for providing compensation for demodulated data output from said demodulated data rotating means in accordance with an amount of delay, based on the mean value of phase difference estimated by said first and second phase difference estimating means.

26. A spread spectrum communication apparatus, comprising:

multiplexing means for spreading a transmission signal by using a single spread code to generate a plurality of spread symbols, delaying continuous spread symbols by a single or a plurality of chips of the spread transmission signal and for multiplexing the plurality of spread symbols and the delayed spread symbols; and

data inserting means for inserting data for maintaining constant or multiplying by a constant value the spread symbols delayed by a single or a plurality of chips.

27. A spread spectrum communication apparatus in which a transmission signal is spread by using a single spread code to generate a plurality of spread symbols, continuous spread symbols are delayed by one or a plurality of chips of the spread code and the plurality of spread symbols are multiplexed and transmitted, and the transmitted spread spectrum signal is received, the spread spectrum communication apparatus comprising:

correlating means for receiving and correlating the transmitted spread spectrum signal with a predetermined code and for outputting a correlation peak value;

pattern recognition means for recognizing a pattern indicative of a correlation peak value output from said correlating means; and

means for setting a code different from said predetermined code, based on a pattern recognized by said pattern recognizing means.

28. A spread spectrum communication apparatus, comprising:

a reception antenna for receiving a transmission signal;

frequency converting means for frequency converting the transmission signal received by said reception antenna with a frequency in synchronization with transmission frequency to baseband I and Q signals;

converting means for converting the baseband I and Q signals to digital signals;

first correlating means for correlating an output from said converting means with a predetermined code;

first determining means for determining an output from said first correlating means and outputting demodulated data;

spread symbol estimating means for estimating, using determination data of an output of said first determining means, preceding and succeeding spread symbols multiplexed on a multiplexed spread symbol to be cancelled;

multiplexed signal removing means for cancelling, by subtracting preceding and succeeding spread symbols to be cancelled multiplexed on the multiplexed spread symbol to be cancelled, by adjusting through successive delay timings of the spread symbol to be cancelled of the output from said spread symbol estimating means and timing of the multiplexed spread symbol to be cancelled of the output from said converting means;

second correlating means for correlating an output from said multiplexed signal removing means and a predetermined code; and

second determining means for determining an output from said second correlating means and providing demodulated data.

29. The spread spectrum communication apparatus according to claim 28, further comprising:

second spread symbol estimating means for estimating preceding spread symbol multiplexed on a multiplexed spread symbol to be cancelled, by using an output from said second determining means.

30. The spread spectrum communication apparatus according to claim 28, wherein said multiplexed signal removing means comprises:

a plurality of first delay means for successively delaying timing of a spread symbol of the output from said spread symbol estimating means which is to be cancelled;

second delay means for delaying timing of the multiplexed spread symbol of the output from said converting means which is to be cancelled; and

subtracting means for subtracting the spread symbol to be cancelled as delayed by said plurality of first delay means from the multiplexed spread symbol to be cancelled as delayed by said second delay means.

31. The spread spectrum communication apparatus according to claim 30, further comprising

amplitude adjusting means for adjusting amplitude level of the spread symbol to be cancelled as delayed by said plurality of first delay means to a level obtained by dividing amplitude level of the multiplexed spread symbol to be cancelled by a number of multiplexing.

32. The spread spectrum communication apparatus according to claim 28, wherein said multiplexed signal removing means comprises:

amplitude adjusting means for adjusting amplitude level of the multiplexed spread symbol of the output of said converting means which is to be cancelled to ten and several times of the amplitude level of the multiplexed spread symbol to be cancelled;

a plurality of first delay means for successively delaying timing of the spread symbol of the output of said spread symbol estimating means which is to be cancelled;

second delay means for delaying the output from said amplitude adjusting means; and

subtracting means for subtracting the spread symbol to be cancelled as delayed by said plurality of first delay means from the multiplexed spread symbol to be cancelled as delayed by said plurality of second delay means.

33. A spread spectrum communication apparatus comprising:

a reception antenna for receiving a transmission signal;

frequency converting means for frequency converting the transmission signal received by said reception antenna with a frequency in synchronization with or close to transmission frequency to baseband I and Q signals;

converting means for converting the baseband I and Q signals to digital signals;

correlating means for correlating an output from said converting means with a predetermined code;

differential demodulating means for differentially demodulating an output from said correlating means; and

determining means for determining an output from said differential demodulating means to provide demodulated data,

wherein a signal is spread by using a single spread code to generate spread signals, continuous spread symbols are delayed by one or a plurality of chips of the spread code, and a plurality of the delayed spread symbols are multiplexed and transmitted as the transmission signal received by said reception antenna, and

wherein assuming a random transmission data, a possibility of generation of signal points on I and Q phase planes of the output of said differential demodulating means is calculated in advance, a mean coordinate thereof is calculated in consideration of the possibility of generation, and determination by said determining means is performed after I and Q coordinate values of the mean coordinate are subtracted from data of the baseband I and Q signals.

34. A spread spectrum communication apparatus comprising:

a reception antenna for receiving a transmission signal

frequency converting means for frequency converting the transmission signal received by said reception antenna with a frequency in synchronization with or close to transmission frequency to baseband I and Q signals;

converting means for converting the baseband I and Q signals to digital signal;

correlating means for correlating an output from said converting means with a predetermined code;

differential demodulating means for differentially demodulating an output from said correlating means; and

determining means for determining an output from said differential demodulating means and obtaining demodulated data,

wherein a signal is spread by using a single spread code to generate spread symbols, continuous spread symbols are delayed by one or a plurality of chips of the spread code and a plurality of the delayed spread symbols are multiplexed and transmitted as the transmission signal received by said reception antenna, and

wherein assuming random transmission data, a possibility of generation of signal points on I and Q phase planes of the output of said differential demodulating means is calculated in advance, a mean coordinate thereof is calculated in consideration of the possibility of generation, and said determining means determines using I and Q coordinate delay of the mean coordinate as references for determining the baseband I and Q signals.

35. A method of direct spread spectrum communication, in which a signal spread by one spread code is delayed by arbitrarily several chips and multiplexed for transmission, a code of which an auto-correlation side lobe is determined uniquely by a value of either preceding or succeeding data regardless of auto-correlation of odd or even correlation being used as the spread code,

with a correlation value to be canceled being a central correlation value, correlations of data timings of (number of multiplexing-1) are held preceding and succeeding the correlation to be canceled, the preceding or succeeding data is selected to select and add correlated values of preceding data and succeeding data determined uniquely, a result of addition is divided by a division rate, and the correlation value to be canceled is added to/subtracted from a result of division to provide a correlated output with an auto/correlation side lobe canceled.

36. The method of direct spread spectrum communication according to claim 35, wherein when the correlated values are divided into blocks by the number of multiplexing and one of the blocked correlated values is to be canceled, an amount of delay is controlled such that all combinations of preceding and succeeding data are processed in one block,

said correlations corresponding to the block are held, correlated values other than the correlation value to be canceled are selected and added, a result of addition is divided by a spread rate, and the correlation value to be canceled is added to/subtracted from a result of division, canceling the auto-correlation side lobe.

37. The method of direct spread spectrum communication according to claim 36, wherein when a Barker code of 11 chips which has a sign opposite to a signal used as a reference for canceling the auto-correlation side lobe is used for division and the number of multiplexing is k, a divisor is 11-k+2, and

when a Barker code of 13 chips which has a same sign as the signal used as a reference for canceling the auto-correlation side lobe, and the number of multiplexing is k, the divisor is 13+k-2.

38. The method of direct spread spectrum communication according to claim 35, wherein when demodulation is performed by using post detection integration, at a demodulation timing used for post detection integration, in order to cancel the auto-correlation side lobe, with correlation corresponding to the post detection integration to be canceled being a center, preceding and succeeding data timing correlations corresponding to the number of multiplexing are held, correlation values of uniquely determined preceding data and succeeding data are selected and added, the result of addition is divided by a spread rate, and the result of division is added to/subtracted from the correlated value of the timing of the post detection integration to be canceled, canceling the auto-correlation side lobe.

39. The method of direct spread spectrum communication according to claim 35, wherein when the correlated values are divided into blocks of the number of multiplexing and one of the blocks of correlated values is to be canceled,

all data of the block of correlated values to be canceled are added, a result of addition is divided by a spread rate, and the block of correlated values to be canceled is added to/subtracted from a result of division, canceling the auto-correlation side lobe.

40. The method of direct spread spectrum communication according to claim 39, wherein when a Barker code of 11 chips having a sign opposite to a signal used as a reference for canceling the auto-correlation side lobe is used as the spread code for division and the number of multiplexing is k, a divisor is 11-k+1, and

when a Barker code of 13 chips having a same sign as the signal used as a reference for canceling the auto-correlation side lobe and the number of multiplexing is k, the divisor is 13+k-1.

41. The method of direct spread spectrum communication according to claim 37, wherein when the 11 chip Barker code is used, the divisor is set to 8, and division is performed by shifting data 3 bits by 3 bits with a least significant 3 bits removed, and

when the 13 chip Barker code is used, the divisor is set to 16 and division is performed by shifting data 4 bits by 4 bits with a least significant 4 bits removed.

42. The method of direct spread spectrum communication according to claim 35, wherein an amplitude level of a reception signal is controlled by varying gain and the gain varied reception signal is digitized and quantified,

gain being controlled by the correlated output.