CDMA COMMUNICATION SYSTEM AND METHOD

• US 20090245210A1
• Filed: 06/08/2009
• Published: 10/01/2009
• Est. Priority Date: 07/09/1996
• Status: Active Grant

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi Communication Technologies, Ltd. (Hitachi, Ltd.)
• Inventors: ARIYOSHI, Masayuki, DOI, Nobukazu, SHIGA, Tesshin, OHTA, Yoshito
• Granted Patent: US 7,916,699 B2
• Time in Patent Office: Days
• 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 base station for communicating with a plurality of terminal stations, comprising:

an antenna for receiving uplink signals from said plurality of terminal stations and transmitting downlink signals to said plurality of terminal stations;

a modulator-demodulator for despreading signals received from said plurality of terminal stations, and for spreading signals to be transmitted to said plurality of terminal stations; and

a phase synchronization controller for generating a phase control signal for controlling a phase of an uplink signal transmitted from one of said plurality of terminal stations,

wherein said modulator-demodulator detects a phase difference between a phase of a spreading code of a signal received from said terminal station and a reference phase, and

said phase synchronization controller generates, in an acquisition searching mode, a first phase control signal, and, in a phase tracking control mode, a second phase control signal, based on said detected phase difference.