CDMA communication system and method

• US 20030214932A1
• Filed: 06/09/2003
• Published: 11/20/2003
• Est. Priority Date: 07/09/1996
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Denshi Kabushiki Kaisha, Hitachi, Ltd.
• Inventors: Shiga, Tesshin, Ohta, Yoshito, Ariyoshi, Masayuki, Doi, Nobukazu
• Granted Patent: US 7,545,777 B2
• Time in Patent Office: Days
• US Class Current: 370/342
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 1/7085 using a code tracking loop, e.g. a delay-locked loop
• CPC Class Codes: H04B 2201/709709 Methods of preventing interference
• CPC Class Codes: H04J 13/00 Code division multiplex systems for frequency hopping H04B1/713
• CPC Class Codes: H04W 56/0005 synchronizing of arrival of multiple uplinks
• CPC Class Codes: H04W 56/0085 detecting a given structure in the signal

Abstract

In CDMA communications, a base station detects a difference between a reference phase of a spreading code and a phase of a received signal of each terminal station, and feeds a phase jump signal PJ-i representative of the phase difference back to each terminal station. After timing acquisition, the reception operation is performed using the reference phase, and a shift amount between the phase of a received signal and the reference phase is fed back to each terminal station as phase synchronization control information PC-i. Each terminal station coarsely adjusts the phase of the spreading code in accordance with the phase jump signal PJ-i, and thereafter finely adjust the phase of its transmitting signal in accordance with the phase synchronization control information PC-i. It is therefore possible to synchronize the phases of signals transmitted from terminal stations and received at the base station. Accordingly, an orthogonal code is used for spreading on reverse links.

Claims

1. A communication method in a code division multiple access communication system for performing communication between a first station and a plurality of second stations, wherein said first station provides a plurality of channels to each of forward and reverse links and a pair of forward and reverse channels are assigned to respective second stations, comprising the steps of:

transmitting, in said first station, a phase difference information (PJ-i, PC-i) which indicates a phase difference between a phase of a spreading code of a received signal on each reverse channel and a reference phase of the spreading code for de-spreading said received signal, via the corresponding forward channel; and

controlling, in each second station, a phase of the spreading code of a transmitting signal on assigned reverse channel in accordance with the received phase difference information,

wherein the spreading code is selected from among a plurality of orthogonal codes.

2. A communication method according to claim 1, wherein the transmitting signals on a plurality of reverse channels are received at said first station in an orthogonal state with each other.

3. A communication method according to claim 1, wherein said phase difference information for each reverse channel includes a first phase difference information and a second phase difference information, wherein said first phase difference information indicates the phase difference detected at each reverse channel during an acquisition searching mode and said second phase difference information indicates the phase difference detected at each reverse channel during a phase tracking mode;

each of said second terminals sets the phase of the spreading code of the transmitting signal in accordance with the first phase difference information and adjusts the phase of the spreading code of the transmitting signal in accordance with the second phase difference information.

4. A communication method according to claim 1, wherein said phase difference information for each reverse channel includes a first phase difference information and a second phase difference information, wherein said first phase difference information indicates a completion of timing acquisition of the received signal on each reverse channel and said second phase difference information indicates the phase difference detected at each reverse channel during a phase tracking mode;

each of said second terminals transmits the transmitting signal which phase is slid by a predetermined amount and sets the phase of the spreading code of the transmitting signal in accordance with a received timing of the first phase difference information and adjusts the phase of the spreading code of the transmitting signal in accordance with the second phase difference information.

5. A communication method in a spread spectrum communication system for performing communication between a first station and second stations, comprising the steps of:

transmitting, in each second station, a transmitting signal spread with a code Wi assigned to respective second stations, wherein the code Wi is selected from among a plurality of orthogonal codes which are orthogonal to each other;

measuring, in said first station, a phase difference between a phase of code Wi of the transmitting signal transmitted from each second station and a reference phase of the code Wi for de-spreading the transmitting signal, and transmitting a phase difference information indicating the measured phase difference; and

controlling, in each second station, a phase of the code Wi of the transmitting signal in accordance with the received phase difference information.

6. A communication method according to claim 5, wherein the transmitting signals from a plurality of second stations are received at said first station in an orthogonal state with each other.

7. A communication method according to claim 5, wherein said phase difference information for each second station includes a first phase difference information and a second phase difference information, wherein said first phase difference information indicates the phase difference detected during an acquisition searching mode and said second phase difference information indicates the phase difference detected during a phase tracking mode;

each of said second terminals sets the phase of the code Wi of the transmitting signal in accordance with the first phase difference information and adjusts the phase of code Wi of the transmitting signal in accordance with the second phase difference information.

8. A communication method according to claim 5, wherein said phase difference information for each second station includes a first phase difference information and a second phase difference information, wherein said first phase difference information indicates a completion of timing acquisition of the transmitting signal from the second station and said second phase difference information indicates the phase difference detected during a phase tracking mode;

each of said second terminals transmits the transmitting signal which phase is slid by a predetermined amount and sets the phase of the code Wi of the transmitting signal in accordance with a received timing of the first phase difference information and adjusts the phase of the code Wi of the transmitting signal in accordance with the second phase difference information.

9. A communication method in a spread spectrum communication system for performing communication between a first station and second stations, comprising the steps of:

transmitting, in each second station, a transmitting signal spread with a spreading code;

performing, in said first station, a timing acquisition of the transmitting signal from each second station and transmitting a first phase difference information which indicates a phase difference between a phase of the spreading code of the transmitting signal and a reference phase of the spreading code for de-spreading the transmitting signal on the timing acquisition;

setting, in each second station, the phase of the spreading code of the transmitting signal in accordance with the first phase difference information;

performing, in said first station, a phase tracking of the transmitting signal from each second station and transmitting a second phase difference information which indicates a phase difference between a phase of the spreading code of the transmitting signal and a reference phase of the spreading code for de-spreading the transmitting signal during the phase tracking;

adjusting, in each second station, the set phase of the spreading code of the transmitting signal in accordance with the second phase difference information.

11. A communication method according to 9, wherein the spreading code is selected from among a plurality of orthogonal codes which are orthogonal to each other.

12. A communication method according to claim 9, wherein said first station calculates a first de-spread result of the transmitting signal with the spreading code which phase is forwarded by half-pitch and a second de-spread result of the transmitting signal with the spreading code which phase is delayed by half-pitch;

and

outputs the second phase difference information as the difference between the first and second de-spread result.

10. A communication method in a spread spectrum communication system for performing communication between a first station and second stations, comprising the steps of:

transmitting, in each second station, a transmitting signal spread with a spreading code which phase is slid by a predetermined amount;

performing, in said first station, a timing acquisition of the transmitting signal from each second station and transmitting a first phase difference information which indicates a completion of the timing acquisition of the transmitting signal;

setting, in each second station, the phase of the spreading code of the transmitting signal in accordance with the received timing of the first phase difference information;

performing, in said first station, a phase tracking of the transmitting signal from each second station and transmitting a second phase difference information which indicates a phase difference between a phase of the spreading code of the transmitting signal and a reference phase of the spreading code for de-spreading the transmitting signal during the phase tracking;

adjusting, in each second station, the set phase of the spreading code of the transmitting signal in accordance with the second phase difference information.

13. A code division multiple access communication system comprising a first station and a plurality of second stations, the first station providing a plurality of channels to each of forward and reverse links and a pair of forward and reverse channels being assigned to respective second stations, wherein:

said first station includes demodulator which de-spreads a received signal on each reverse channel and measures a phase difference between a phase of a spreading code of the received signal and a reference phase of the spreading code for de-spreading the received signal; and

said each second station includes a modulator which spreads a transmitting data with the spreading code whose phase is variable;

wherein the spreading code is selected from among a plurality of orthogonal codes.

14. A code division multiple access communication system according to claim 13, wherein said modulator of said each second station spreads the transmitting data with the spreading code whose phase is set in accordance with a phase difference information indicating the measured phase difference in said first station.

15. A second station for performing communication with a first station comprising:

a spreading code generator which generates a spreading code assigned to said second station; and

a modulator which spreads a transmitting data with the generated spreading code;

wherein a phase of the spreading code for spreading the transmitting data in the modulator is variable.

16. A second station according to claim 15, wherein the spreading code is selected from among a plurality of orthogonal codes.

17. A second station according to claim 15, wherein the phase of the spreading code for spreading the transmitting data in the modulator is controlled in accordance with a phase difference information transmitted from the first station.

18. A second station according to claim 17, wherein said phase difference information includes a first phase difference information and a second phase difference information, wherein said first phase difference information indicates the phase difference detected during an acquisition searching mode and said second phase difference information indicates the phase difference detected during a phase tracking mode;

and

the phase of the spreading code for spreading the transmitting data is set in accordance with the first phase difference information and adjusted in accordance with the second phase difference information.

19. A second station according to claim 18, further comprising a delay circuit which delay the generated spreading code and input the delayed spreading code to the modulator,

wherein said spreading code generator generates the spreading code with a phase set in accordance with the first phase different information, and a delay amount of said delay circuit is set in accordance with the second phase different information.

20. A second station according to claim 17, wherein said phase difference information includes a first phase difference information which indicates a completion of timing acquisition of the transmitting signal from the second station;

and

said spreading code generator generates the spreading code which phase is slid by a predetermined amount until the second station receives the first phase different information, and set the phase of the spreading code for spreading the transmitting data in accordance with a received timing of the first phase different information.

21. A second station according to claim 20, further comprising a delay circuit which delay the generated spreading code and input the delayed spreading code to the modulator,

wherein said phase difference information includes a second phase difference information which indicates the phase difference detected during a phase tracking mode;

and

a delay amount of said delay circuit is set in accordance with the second phase different information.

22. A second station according to claim 18, wherein the transmitting data are fixed as consecutive symbols during the acquisition searching mode.

23. A second station according to claim 20, wherein the transmitting data are fixed as consecutive symbols before the completion of timing acquisition.

24. A system for modulating an transmitting data in a spread spectrum communication system, comprising:

an orthogonal code generator which generates an orthogonal code;

a pseudo-noise (PN) code generator which generates a PN code; and

a modulator which spreads the transmitting data with the generated orthogonal code and the generated PN code;

wherein phases of generated orthogonal code and PN code are variable.

25. A system according to 24, further comprising:

a first delay circuit which delays the generated orthogonal code and input the delayed orthogonal code to the modulator; and

a second delay circuit which delays the generated PN code and input the delayed PN code to the modulator.

26. A system according to claim 25, wherein phases of the generated orthogonal code and the generated PN code are equal to each other;

and

Delay amounts of said first delay circuit and second delay circuit are equal to each other.

27. A first station for performing communication with second stations via a plurality of forward channels and reverse channels comprising:

a demodulator which de-spreads a received signal on each reverse channel with a first spreading code corresponding to the reverse channel;

a phase synchronization controller which generates phase difference information indicating a phase difference between a phase of the first spreading code of the received signal and a reference phase of the first spreading code for de-spreading the received signal;

a modulator which spreads the phase difference information with a second spreading code corresponding to each forward channel.

28. A first station according to claim 27, wherein said first and second spreading codes are selected from among a plurality of orthogonal codes.

29. A first station according to claim 27, further comprising:

a acquisition circuit which performs a timing acquisition of the received signal and detects a phase difference between a phase of the first spreading code of the received signal and a reference phase of the first spreading code for de-spreading the received signal; and

a phase state decision circuit which performs a phase tracking of the received signal and detects a phase difference between a phase of the first spreading code of the received signal and a reference phase of the first spreading code for de-spreading the received signal.

30. A first station according to claim 27, wherein the same phase as the phase of the second spreading code for spreading the phase difference information on the forward channel or as the phase of the first spreading code for de-spreading the received signal on one of reverse channels is set as the reference phase of the first spreading code for de-spreading the received signal.

31. A first station according to claim 27, wherein the timing acquisition is determined by setting the accumulation period in a de-spreading processing for the received signal on the reverse channel longer than an one-symbol data period.

32. A communication method in a spread spectrum communication system for performing communication between a first station and second stations, comprising the steps of:

transmitting a transmitting signal spread with a code Wi assigned to respective second stations, wherein the code Wi is selected from among a plurality of orthogonal codes which are orthogonal to each other;

receiving a phase difference information indicating a phase difference between a phase of code Wi of the transmitting signal and a reference phase of the code Wi for de-spreading the transmitting signal; and

controlling a phase of the code Wi of the transmitting signal in accordance with the received phase difference information.

33. A communication method in a spread spectrum communication system for performing communication between a first station and second stations, comprising the steps of:

receiving a received signal transmitted from each second stations, wherein the received signal is spread with a code Wi assigned to respective second stations;

measuring a phase difference between a phase of code Wi of the received signal and a reference phase of the code Wi for de-spreading the received signal; and

transmitting a phase difference information indicating the measured phase difference,

wherein the code Wi is selected from among a plurality of orthogonal codes which are orthogonal to each other.