CDMA communication system and method

• US 6,597,676 B1
• Filed: 04/18/2000
• Issued: 07/22/2003
• Est. Priority Date: 07/09/1996
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Denshi Kabushiki Kaisha, Hitachi, Ltd.
• Inventors: Doi, Nobukazu, Shiga, Tesshin, Ohta, Yoshito, Ariyoshi, Masayuki
• Primary Examiner(s): Kizou, Hassan
• Assistant Examiner(s): Hoang, Thai D
• Application Number:
  US09/550,807
• Time in Patent Office: 1,190 Days
• Field of Search: 370/277, 370/310, 370/328, 370/335, 370/342, 370/441, 370/913, 375/140, 375/226, 375/356, 375/358, 709/400
• US Class Current: 370/335
• 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 adjusts 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 the signals transmitted from terminal stations and received at the base station. Accordingly, an orthogonal code is used for spreading on the reverse links.

Claims

1. A communication method in a spread spectrum communication system for performing communication between a base station and terminal stations, comprising the steps of:

transmitting, in each terminal station, a first signal spread with a spreading code generated by a spreading code generator;

performing, in the base station, a timing acquisition of the first signal from each terminal station and transmitting first difference information which indicates a phase difference between the first signal and a reference phase used in the timing acquisition;

setting, in each terminal station, the phase of the spreading code generated by the spreading code generator in accordance with the first difference information and transmitting a second signal spread with the spreading code having the set phase;

performing, in the base station, a tracking of the second signal from each terminal station and transmitting second difference information between the second signal and the reference phase;

setting, in each terminal station, a delay amount of a delay circuit in accordance with the second difference information, wherein the delay circuit is between an antenna of each terminal station and the spreading code generator.

2. A communication method according to claim 1, wherein the delay circuit adjusts the phase of the spreading coded of a signal transmitted to the base station.

3. A communication method according to claim 1, wherein the base station calculates a first de-spread result of the second signal with the spreading code whose phase is forwarded by half-pitch and a second de-spread result of the second signal with the spreading code whose phase is delayed by half-pitch;

and

the base station outputs a difference between the first and second de-spread results as phase difference information which is used for generating the second difference information.

4. A terminal station for performing communication with a base station, comprising:

a spreading code generator which generates a spreading code assigned to the terminal station and having a phase set in accordance with first difference information transmitted from the base station, wherein the first difference information indicates a phase difference between a reference phase and a first spectrum spreading signal which is transmitted from each terminal station and received by the terminal station, said reference phase being used in a timing acquisition of the first spectrum spreading signal;

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

a delay circuit, between an antenna and the spreading code generator, whose delay is set in accordance with second difference information transmitted from the base station, wherein the second difference information indicates a difference during tracking between the reference phase and a second spectrum spreading signal which is transmitted from each terminal station and received by the base station.

5. A terminal station according to claim 4, wherein the delay adjusts a phase of the spreading code of a spectrum spreading signal spread by the modulator.

6. A terminal station for performing communication with a base station comprising:

a spreading code generator which generates a spreading code assigned to the terminal station, the spreading code generator slides a phase of the spreading code by a predetermined amount until receiving first difference information transmitted from the base station, wherein the first difference information indicates a completion of timing acquisition of the transmitting signal from the terminal station;

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

a delay circuit, between an antenna and the spreading code generator, whose delay amount is set in accordance with second difference information transmitted from the base station, wherein the second difference information indicates a difference during tracking between a reference and the transmitting signal which is transmitted from each terminal station and received by the base station.

7. A terminal station according to claim 6, further comprising a delay circuit which delay the generated spreading code and input the delayed spreading code to the modulator.

8. A terminal station according to claim 6, wherein the transmitting data are fixed as consecutive symbols before the completion of timing acquisition.

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

transmitting, in each terminal station, a first spectrum spreading signal;

performing, in the base station, a timing acquisition of the first spectrum spreading signal from each terminal station and transmitting first difference information which indicates a phase difference between a spreading code for the first spectrum spreading signal and a reference phase used in the timing acquisition;

setting, in each terminal station, a phase of a spreading code generated by a spreading code generator in accordance with the first difference information and transmitting a second spectrum spreading signal spread with the spreading code generated by the spreading code generator;

performing, in the base station, a phase tracking of the second spectrum spreading signal from each terminal station and transmitting second difference information which indicates a difference between the second spectrum spreading signal and the reference phase during the phase tracking;

setting, in each terminal station, a delay amount of a delay circuit in accordance with the second difference information, wherein the delay circuit is between an antenna of each terminal station and the spreading code generator.

10. A communication method according to claim 9, wherein the delay circuit adjusts a phase of a spreading code of a spectrum spreading signal transmitted to the base station.

11. A communication method according to claim 9, wherein the base station calculates a first de-spread result of the second spectrum spreading signal with the spreading code for the second spectrum spreading signal whose phase is forwarded by half-pitch and a second de-spread result of the second spectrum spreading signal with the spreading code for the second spectrum spreading signal whose phase is delayed by half-pitch;

and

the base station outputs a difference between the first and second de-spread results as phase difference information which is used for generating the second difference information.

12. A communication method in a spread spectrum communication system for performing communication between a base station and terminal stations, comprising the steps of:

in an asynchronous state between a first spectrum spreading signal and a reference phase, wherein the first spectrum spreading signal is transmitted from each terminal station and received by the base station, performing, in the base station, a timing acquisition of the first spectrum spreading signal and transmitting first difference information which indicates a phase difference between the first spectrum spreading signal and the reference phase used in the timing acquisition; and

setting, in each terminal station, a phase of a spreading code generated by a spreading code generator in accordance with the first difference information;

in a synchronous state between a second spectrum spreading signal and the reference phase, wherein the second spectrum spreading signal is transmitted from each terminal station and received by the base station, performing, in the base station, a tracking of the second spectrum spreading signal and transmitting second difference information which indicates a difference between the second spectrum spreading signal and the reference phase during the tracking; and

setting, in each terminal station, a delay amount of a delay circuit in accordance with the second difference information, wherein the delay circuit is between an antenna of each terminal station and the spreading code generator.

13. A communication method according to claim 12, wherein the delay circuit adjusts a phase of a spreading code of a spectrum spreading signal transmitted to the base station.

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

and

the base station outputs a difference between the first and second de-spread results as phase difference information which is used for generating the second difference information.