Code division multiple access communication system and code division multiple access transmitting apparatus

• US 6,714,582 B2
• Filed: 11/27/2002
• Issued: 03/30/2004
• Est. Priority Date: 07/11/2000
• Status: Expired due to Term

• Current Assignee: Fujitsu Limited
• Original Assignee: Fujitsu Limited
• Inventors: Obuchi, Kazuhisa, Aoki, Nobuhisa, Nakamura, Takaharu
• Primary Examiner(s): Tran, Khai
• Application Number:
  US10/308,267
• Publication Number:
  US 20030081655A1
• Time in Patent Office: 489 Days
• Field of Search: 375/141, 375/130, 375/142, 375/146, 375/147, 375/150, 375/295, 370/335, 370/320, 370/342
• US Class Current: 375/141
• CPC Class Codes: H04B 1/7103 the interference being multiple access interference
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/16 Code allocation

Abstract

In a CDMA transmitting apparatus, a cross-correlation value between different spreading-code sequences used to spread respective ones of a plurality of transmit signals is calculated, an interference interval of a spreading-code sequence is discriminated from the cross-correlation value calculated, and interference noise is reduced by halting transmission of at least one transmit signal, or partially altering at least one spreading-code sequence, with regard to all or part of a spreading-code sequence discriminated to be an interference interval.

Claims

1. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating a cross-correlation value of spreading-code sequences each of which is assigned to each transmit signal;

a discriminator for discriminating an interference interval of the spreading-code sequences from the cross-correlation value calculated; and

a switch for halting transmission of at least one of said plurality of transmit signals with regard to all or part of a spreading-code sequence discriminated to be an interference interval.

2. A spread signal transmitting apparatus according to claim 1, wherein said cross-correlation detector calculates a cross-correlation between spreading-code sequences in advance and saves the position of a spreading-code sequence for which the cross-correlation value exceeds a predetermined fixed value;

and

said switch halts transmission of a transmit signal with regard to all or part of a spreading-code sequence that corresponds to the position saved.

3. A spread signal transmitting apparatus according to claim 1, wherein halting of transmission is applied to a transmit signal that exhibits a smaller spreading rate.

4. A spread signal transmitting apparatus according to claim 1, wherein halting of transmission is applied to transmit signals selected from among said plurality of transmit signals in order, randomly or in accordance with predetermined order-selection logic.

5. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating, symbol by symbol, a cross-correlation value of spreading-code sequences each of which is assigned to each transmit signal;

a discriminator for discriminating an interference interval of the spreading-code sequence from the cross-correlation value calculated; and

a spreading-code altering unit for altering a code segment, which has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence among said spreading-code sequences.

6. A spread signal transmitting apparatus according to claim 5, wherein said cross-correlation detector calculates a cross-correlation between spreading-code sequences in advance and saves the position of a spreading-code sequence for which the cross-correlation value exceeds a predetermined fixed value;

and

said spreading-code altering unit alters a code segment of a spreading-code sequence, which corresponds to the position saved, to another code.

7. A spread signal transmitting apparatus according to claim 5, wherein altering of a spread code is applied to a transmit signal that exhibits a smaller spreading rate.

8. A spread signal transmitting apparatus according to claim 5, wherein altering of a spread code is applied to transmit signals selected from among said plurality of transmit signals in order, randomly or in accordance with predetermined order-selection logic.

9. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal transmitting apparatus has:

an encoder for encoding each item of transmit data;

a spread-spectrum modulator for modulating encoded data by different spreading-code sequences;

a transmitter for transmitting each spread-spectrum modulated signal;

a cross-correlation detector for calculating a cross-correlation value between said different spreading-code sequences;

a discriminator for discriminating an interference interval of the spreading-code sequences from the cross-correlation value calculated; and

a switch for halting transmission of at least one of said plurality of items of transmit data with regard to all or part of a spreading-code sequence discriminated to be an interference interval; and

said spread signal receiving apparatus has;

a despreading modulator for despreading receive data by a plurality of despreading-code sequences identical with spreading-code sequences; and

a decoder for decoding transmit data from each despread signal.

10. A code division multiple access communication system according to claim 9, wherein the spread signal transmitting apparatus has an encoder for performing encoding processing by adopting a bit, which corresponds to a segment of a spreading-code sequence not transmitted by the switch, as a non-transmit bit, thereby reducing the number of transmit bits, and means for reporting the position of the non-transmit bit to the spread signal receiving apparatus;

and

the spread signal receiving apparatus has a decoder for performing decoding processing upon excluding the non-transmit bit based upon non-transmit-bit information reported from the transmitter via transmitting means.

11. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal transmitting apparatus has:

an encoder for encoding each item of transmit data;

a spread-spectrum modulator for modulating encoded data by different spreading-code sequences;

a transmitter for transmitting each spread-spectrum modulated signal;

a cross-correlation detector for calculating, symbol by symbol, a cross-correlation value between said different spreading-code sequences;

a discriminator for discriminating an interference interval of the spreading-code sequences from the cross-correlation value calculated; and

a spreading-code altering unit for altering a code segment, which has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence among said spreading-code sequences; and

said spread signal receiving apparatus has;

a despreading modulator for despreading receive data by a plurality of despreading-code sequences identical with spreading-code sequences; and

a decoder for decoding transmit data from each despread signal.

12. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal transmitting apparatus has:

a cross-correlation detector for calculating a cross-correlation value of the spreading-code sequences each of which is assigned to each transmit signal;

a discriminator for discriminating an interference interval of the spreading-code sequences from the cross-correlation value calculated;

a spreading-code altering unit for altering a code segment, which corresponds to a spreading-code sequence that has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence; and

means for reporting altered condition of a spreading-code sequence to the spread signal receiving apparatus; and

said spread signal receiving apparatus has a despreading-code altering unit which, based upon the altered condition of the spreading-code sequence reported, is for altering a despreading-code sequence in such a manner that it will become identical with said spreading-code sequence after the alteration.

13. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal receiving apparatus has:

a cross-correlation detector for calculating a cross-correlation value of code sequences that a transmitter uses for spread-spectrum modulation;

a discriminator for discriminating an interference interval of the spreading-code sequences from the cross-correlation value calculated; and

means for detecting position of a spreading-code sequence discriminated to be an interference interval, or position of code coincidence chip by chip within a spreading-code sequence discriminated to be an interference interval, and reporting this position to the transmitter; and

said spread signal transmitting apparatus has;

means for receiving position information sent from a receiver; and

a switch for halting transmission of at least one transmit signal with regard to all or part of a prescribed spreading-code sequence based upon the position information reported.

14. A code division multiple access communication system according to claim 13, wherein said spread signal transmitting apparatus has an encoder for performing encoding processing by adopting a bit, which corresponds to a spreading-code sequence for which the cross-correlation value reported from the receiver is large, as a non-transmit bit, thereby reducing the number of transmit bits;

and

the spread signal receiving apparatus has a decoder for decoding transmit data by performing decoding processing upon excluding a bit curtailed based upon information reported to the transmitter.

15. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal receiving apparatus has:

a cross-correlation detector for calculating a cross-correlation value of code sequences that a transmitter uses for spread-spectrum modulation;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

means for detecting position of a spreading-code sequence discriminated to be an interference interval, or position of code coincidence chip by chip within a spreading-code sequence discriminated to be an interference interval, and reporting this position to the transmitter; and

said spread signal transmitting apparatus has;

means for receiving position information sent from a receiver; and

a spreading-code altering unit for altering a code segment of a spreading-code sequence, which corresponds to said reported position information, to another code with regard to at least one spreading-code sequence.

16. A code division multiple access communication system according to claim 15, comprising:

a despreading-code sequence altering unit which, based upon the position information, is for altering a despreading-code sequence in such a manner that it will become identical with the spreading-code sequence after the alteration.

17. A code division multiple access communication system according to claim 15, wherein said spread signal transmitting apparatus has means for reporting altered condition of a spreading-code sequence to the receiver;

said spread signal receiving apparatus has a despreading-code altering unit which, based upon the altered condition of the spreading-code sequence reported from the transmitter, is for altering a despreading-code sequence in such a manner that it will become identical with said spreading-code sequence after the alteration.

18. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated transmit signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a switch for halting transmission of at least one of said plurality of transmit signals with regard to all or part of a spreading-code sequence discriminated to be an interference interval.

19. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated transmit signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a spreading-code altering unit for altering a code segment, which has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence among said spreading-code sequences.

20. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of transmit signals to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding a transmit signal from the despread signal, wherein said spread signal transmitting apparatus has:

an encoder for encoding each item of transmit data;

a spread-spectrum modulator for modulating encoded data by different spreading-code sequences;

a transmitter for transmitting each spread-spectrum modulated signal;

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a switch for halting transmission of at least one of said plurality of items of transmit data with regard to all or part of a spreading-code sequence discriminated to be an interference interval; and

said spread signal receiving apparatus has;

a despreading modulator for despreading receive data by a plurality of despreading-code sequences identical with spreading-code sequences; and

a decoder for decoding transmit data from each despread signal.

21. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal transmitting apparatus has:

an encoder for encoding each item of transmit data;

a spread-spectrum modulator for modulating encoded data by different spreading-code sequences;

a transmitter for transmitting each spread-spectrum modulated signal;

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a spreading-code altering unit for altering a code segment, which has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence among said spreading-code sequences; and

said spread signal receiving apparatus has;

a despreading modulator for despreading receive data by a plurality of despreading-code sequences identical with spreading-code sequences; and

a decoder for decoding transmit data from each despread signal.

22. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal transmitting apparatus has:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a spreading-code altering unit for altering a code segment, which corresponds to a spreading-code sequence that has been discriminated to be an interference interval, to another code with regard to at least one spreading-code sequence; and

means for reporting altered condition of a spreading-code sequence to the spread signal receiving apparatus; and

said spread signal receiving apparatus has a despreading-code altering unit which, based upon the altered condition of the spreading-code sequence reported, is for altering a despreading-code sequence in such a manner that it will become identical with said spreading-code sequence after the alteration.

23. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal receiving apparatus has:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

means for detecting position of a spreading-code sequence discriminated to be an interference interval, or code coincidence position chip by chip within a spreading-code sequence discriminated to be an interference interval, and reporting this position to a transmitter; and

said spread signal transmitting apparatus has;

means for receiving position information sent from a receiver; and

a switch for halting transmission of at least one transmit signal with regard to all or part of a prescribed spreading-code sequence based upon the position information reported.

24. A code division multiple access communication system having a spread signal transmitting apparatus for subjecting a plurality of items of transmit data to spread-spectrum modulation processing using mutually different spreading-code sequences and simultaneously transmitting a plurality of spread-spectrum signals obtained, and a spread signal receiving apparatus for despreading a receive signal by a despreading-code sequence identical with a spreading-code sequence and decoding transmit data from the despread signal, wherein said spread signal receiving apparatus has:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

means for detecting position of a spreading-code sequence discriminated to be an interference interval, or code coincidence position chip by chip within a spreading-code sequence discriminated to be an interference interval, and reporting this position to a transmitter; and

said spread signal transmitting apparatus has;

means for receiving position information sent from a receiver; and

a spreading-code altering unit for altering a code segment of a spreading-code sequence, which corresponds to said reported position information, to another code with regard to at least one spreading-code sequence.

25. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating a cross-correlation value of spreading-code sequences each of which is assigned to each transmit signal;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a halting unit for halting transmission of at least one of said plurality of transmit signals with regard to all or part of a spreading-code sequence discriminated to be an interference interval.

26. A spread signal transmitting apparatus in a code division multiple access communication system for spread-spectrum modulating a plurality of transmit signals using different spreading-code sequences, and simultaneously communicating a plurality of spread-spectrum modulated signals, comprising:

a cross-correlation detector for calculating a cross-correlation value between spread-spectrum modulated transmit signals;

a discriminator for discriminating an interference interval of a spreading-code sequence from the cross-correlation value calculated; and

a halting unit for halting transmission of at least one of said plurality of transmit signals with regard to all or part of a spreading-code sequence discriminated to be an interference interval.