Code division multiple access mobile communication system

• US 7,336,697 B2
• Filed: 02/26/2004
• Issued: 02/26/2008
• Est. Priority Date: 09/11/1995
• Status: Expired due to Fees

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohgoshi, Yasuo, Doi, Nobukazu, Yano, Takashi
• Primary Examiner(s): Tran; Khai
• Application Number:
  US10/786,092
• Publication Number:
  US 20040165651A1
• Time in Patent Office: 1,461 Days
• Field of Search: 375/141, 375/130, 375/147, 375/150, 370/335, 370/362, 341/173
• US Class Current: 375/141
• CPC Class Codes: H04B 1/707 using direct sequence modulation
• CPC Class Codes: H04B 7/2628 using code-division multiple access [CDMA] or spread spectrum multiple access [SSMA] H04B7/2618 takes precedence

Abstract

A code division multiple access (CDMA) mobile communication system with improvements to permit stable reception with a minimum of bit error. The system includes a base station and a mobile station for communicating with the base station. The mobile station includes an oscillator, a radio frequency demodulator for demodulating a radio frequency band signal received from the base station by use of a first signal from the oscillator, a radio frequency modulator for modulating a second signal to be transmitted by use of the first signal from the oscillator, and an antenna for receiving the radio frequency band signal transmitted from the base station, and for transmitting the modulated second signal to the base station. An oscillation frequency of the oscillator is controlled by use of a change of phase shift detected using the demodulated radio frequency band signal received from the base station.

Claims

1. A mobile station for communicating with a base station, comprising;

an oscillator;

a radio frequency demodulator for demodulating a radio frequency band signal received from said base station by use of a first signal from said oscillator;

a radio frequency modulator for modulating a second signal to be transmitted by use of the first signal from said oscillator; and

an antenna for receiving said radio frequency band signal transmitted from said base station, and for transmitting said modulated second signal to said base station,

wherein an oscillation frequency of the oscillator is controlled by use of a change of phase shift detected using the demodulated radio frequency band signal received from the base station.

2. A mobile station according to claim 1, wherein the change of phase shift is detected using a pilot signal received from said base station.

3. A mobile station according to claim 2, wherein said pilot signal is extracted by despreading the demodulated radio frequency band signal using a spread spectrum code assigned to the pilot signal.

4. A method of transmitting a first signal from a mobile station to a base station, comprising the steps of:

demodulating a radio frequency band signal received from said base station by use of a second signal from an oscillator;

modulating the first signal to be transmitted by use of the second signal from the oscillator; and

transmitting said modulated first signal,

wherein an oscillation frequency of the oscillator is controlled by use of a change of phase shift detected using the demodulated radio frequency band signal received from the base station.

5. A method of transmitting a first signal from a mobile station according to claim 4, wherein said change of phase shift is detected using a pilot signal received from said base station.

6. A method of transmitting a first signal from a mobile station according to claim 5, further comprising the step of:

despreading the demodulated radio frequency band signal to extract said pilot signal.

7. A mobile station which receives signals from a base station, comprising:

an antenna for receiving said signals from said base station;

an oscillator;

a demodulator for demodulating said received signals using a signal from said oscillator,

wherein an oscillation frequency of said oscillator is controlled by use of a change of phase shift detected using the demodulated signal received from the base station.

8. A mobile station according to claim 7, wherein said received signals include a pilot signal, and said change of phase shift is detected using said pilot signal.

9. A mobile station according to claim 8, further comprising:

a despreader for despreading the demodulated signal to extract said pilot signal.

10. A mobile station for communicating with a base station, comprising:

an antenna for receiving signals transmitted from said base station based on phase shift keying, and for transmitting signals to said base station;

an oscillator;

a demodulator for demodulating the received signals using a signal from said oscillator;

a frequency correction circuit for controlling an oscillation frequency of the oscillator to correct frequency error based on a detected phase of the demodulated signal; and

a phase correction circuit for correcting a phase of at least a part of the demodulated signals based on said detected phase of the demodulated signal.

11. A mobile station according to claim 10, wherein said phase correction circuit performs phase correction on a symbol basis.

12. A mobile station according to claim 10, said detected phase is a phase detected using a pilot signal received from said base station.