Code division multiple access mobile communication system

• US 5,943,329 A
• Filed: 09/09/1996
• Issued: 08/24/1999
• Est. Priority Date: 09/11/1995
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Ohgoshi, Yasuo, Doi, Nobukazu, Yano, Takashi
• Primary Examiner(s): NGUYEN, CHAU T
• Application Number:
  US08/709,734
• Time in Patent Office: 1,079 Days
• Field of Search: 370/320, 370/335, 370/342, 370/491, 370/206, 370/503, 370/479, 370/350, 370/468, 375/200, 375/206, 375/362, 375/344, 455/182.2, 455/192.2, 455/197.1
• US Class Current: 370/335
• 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 comprises a voltage-controlled oscillator for supplying a carrier to a radio frequency quadrature demodulator, and a frequency controller for detecting a frequency error from a phase correction signal of the first step to generate a control signal that controls the oscillator. The frequency controller includes an extracting circuit and an integrating circuit. The extracting circuit extracts a phase change based on the frequency error derived from the phase correction signal of the first step and from a signal preceding that signal by a predetermined delay time. The integrating circuit integrates the phase change and outputs the integrated result as the control signal. The predetermined delay time is preferably set within a range not exceeding the delay time needed for averaging by an averaging circuit that receives the phase correction signal of the first step and outputs a phase correction signal. The carrier to a radio frequency quadrature modulator is preferably supplied from the voltage-controlled oscillator.

Claims

1. A code division multiple access mobile communication system for spreading, modulating and transmitting a pilot signal along with data into radio frequency band signals, demodulating and despreading the received radio frequency band signals into a received pilot signal and received data, and generating a phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal during detection, the system comprising:

a plurality of mobile stations and a base station, said base station establishing up and down links in conjunction with said plurality of mobile stations;

each of said plurality of mobile stations having a detection circuit including;

a voltage-controlled oscillator for supplying a carrier to a radio frequency quadrature demodulator demodulating the received radio frequency band signals;

an averaging circuit for averaging a first step phase correction signal generated from the received pilot signal and outputting said phase correction signal; and

a frequency controller for detecting a frequency error from said first step phase correction signal, said frequency controller further generating from said frequency error a control signal to control the frequency of the carrier generated by said voltage-controlled oscillator, wherein said frequency controller comprises;

a phase change generating circuit for generating a phase change based on said frequency error derived from said first step phase correction signal and a signal preceding said first step phase correction signal by a predetermined delay time; and

an integrating circuit for integrating said phase change and outputting the integrated result as said control signal.

2. A code division multiple access mobile communication system according to claim 1, wherein said predetermined delay time is set within a range not exceeding the delay time needed for averaging by said averaging circuit.

3. A code division multiple access mobile communication system according to claim 2, wherein said plurality of mobile stations each include a radio frequency quadrature modulator supplied with the carrier from said voltage-controlled oscillator.

4. A code division multiple access mobile communication system according to claim 3, wherein said plurality of mobile stations each set a spreading ratio variably in keeping with changing bit rates of data and generate a spread signal for transmission having a constant chip rate.

5. A code division multiple access mobile communication system for transmitting and receiving data spread by a spread code over a radio frequency band, the system comprising:

a plurality of mobile stations and a base station;

said plurality of mobile stations each having a detection circuit including;

a temporary judge circuit acting when each of a sign of a cosine component and a sign of a sine component of despread data is found to be inverted one symbol later, said temporary judge circuit thereupon inverting the signs of the components individually and outputting the sign-inverted components, said temporary judge circuit further outputting the components uninverted when the signs thereof are found to be uninverted one symbol later;

a frequency controller for generating a phase change based on the frequency error derived from the output signal of said temporary judge circuit and from a signal preceding said output signal by a predetermined delay time, said frequency controller further integrating said phase change and outputting the integrated result as a control signal;

a voltage-controlled oscillator for receiving said control signal as a signal to control an oscillation frequency; and

a radio frequency quadrature demodulator for receiving the output signal of said voltage-controlled oscillator as a carrier to demodulate received radio frequency band signals;

wherein said base station establishes up and down links in conjunction with said plurality of mobile stations.

6. A mobile station for use with a code division multiple access mobile communication system for spreading, modulating and transmitting a pilot signal along with data into radio frequency band signals, demodulating and despreading the received radio frequency band signals into a received pilot signal and received data and generating a phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal during detection,

said mobile station having a detection circuit comprising:

a voltage-controlled oscillator for supplying a carrier to a radio frequency quadrature demodulator demodulating the received radio frequency band signals;

an averaging circuit for averaging a first step phase correction signal generated from the received pilot signal and outputting said phase correction signal; and

a frequency controller for detecting a frequency error from said first step phase correction signal, said frequency controller further generating from said frequency error a control signal to control the frequency of said voltage-controlled oscillator, wherein said frequency controller comprises;

a phase change generating circuit for generating a phase change based on said frequency error derived from said first step phase correction signal and from a signal preceding said first step phase correction signal by a predetermined delay time; and

an integrating circuit for integrating said phase change and outputting the integrated result as said control signal.

7. A mobile station according to claim 6, wherein said predetermined delay time is set within a range not exceeding the delay time needed for averaging by said averaging circuit.

8. A mobile station according to claim 7, further comprising a radio frequency quadrature modulator supplied with the carrier from said voltage-controlled oscillator.

9. A mobile station according to claim 8, further comprising means for setting a spreading ratio variably in keeping with changing bit rates of data and for generating a spread signal for transmission having a constant chip rate.

10. A mobile station for use with a code division multiple access mobile communication system for transmitting and receiving data spread by a spread code over a radio frequency band, said mobile station having a detection circuit comprising:

a temporary judge circuit acting when each of a sign of a cosine component and a sign of a sine component of despread data is found to be inverted one symbol later, said temporary judge circuit thereupon inverting the signs of the components individually and outputting the sign-inverted components, said temporary judge circuit further outputting the components uninverted when the signs thereof are found to be uninverted one symbol later;

a frequency controller for generating a phase change based on the frequency error derived from the output signal of said temporary judge circuit and from a signal preceding said output signal by a predetermined delay time, said frequency controller further integrating said phase change and outputting the integrated result as a control signal;

a voltage-controlled oscillator for receiving said control signal as a signal to control an oscillation frequency; and

a radio frequency quadrature demodulator for receiving the output signal of said voltage-controlled oscillator as a carrier to demodulate received radio frequency band signals.

11. A code division multiple access mobile communication system for spreading, modulating and transmitting a pilot signal along with data into radio frequency band signals, demodulating and despreading the received radio frequency band signals into a received pilot signal and received data and generating a phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal during detection, the system comprising:

a plurality of mobile stations and a base station, said base station establishing up and down links in conjunction with said plurality of mobile stations;

each of said plurality of mobile stations having a detection circuit including;

a voltage-controlled oscillator for supplying a carrier to a radio frequency quadrature demodulator demodulating the received radio frequency band signals;

an averaging circuit for averaging a first step phase correction signal generated from the received pilot signal and outputting said phase correction signal; and

means for detecting a frequency error from said first step phase correction signal, and for generating from said frequency error a control signal to control the frequency of the carrier generated by said voltage-controlled oscillator, wherein said means for detecting comprises;

means for generating a phase change based on said frequency error derived from said first step phase correction signal and from a signal preceding said first step phase correction signal by a predetermined delay time; and

means for integrating said phase change and outputting the integrated result as said control signal.

12. A mobile station for use with a code division multiple access mobile communication system for spreading, modulating and transmitting a pilot signal along with data into radio frequency band signals, demodulating and despreading the received radio frequency band signals into a received pilot signal and received data and generating a phase correction signal from the received pilot signal so that a phase error of the received data is corrected by use of said phase correction signal during detection,

said mobile station having a detection circuit comprising:

a voltage-controlled oscillator for supplying a carrier to a radio frequency quadrature demodulator demodulating the received radio frequency band signals;

an averaging circuit for averaging a first step phase correction signal generated from the received pilot signal and outputting said phase correction signal; and

means for detecting a frequency error from said first step phase correction signal, and for generating from said frequency error a control signal to control the frequency of said voltage-controlled oscillator, wherein said means for detecting comprises;

means for generating a phase change based on said frequency error derived from said first step phase correction signal and from a signal preceding said first step phase correction signal by a predetermined delay time; and

means for integrating said phase change and outputting the integrated result as said control signal.