Code division multiple access mobile communication system
First Claim
1. A mobile station for use with a mobile communication system multiplexing a plurality of communication channels using spread spectrum codes comprising:
- an oscillator;
a radio frequency demodulator demodulating a radio frequency band signal transmitted from a base station by use of a signal from the oscillator; and
a despreading circuit extracting a pilot signal by despreading the demodulated radio frequency band signal using the spread spectrum code assigned to the pilot signal;
wherein an oscillation frequency of the oscillator is controlled by use of a change of a phase shift detected using a signal representing a phase shift detected from the extracted pilot signal.
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Accused Products
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.
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Citations
13 Claims
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1. A mobile station for use with a mobile communication system multiplexing a plurality of communication channels using spread spectrum codes comprising:
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an oscillator;
a radio frequency demodulator demodulating a radio frequency band signal transmitted from a base station by use of a signal from the oscillator; and
a despreading circuit extracting a pilot signal by despreading the demodulated radio frequency band signal using the spread spectrum code assigned to the pilot signal;
wherein an oscillation frequency of the oscillator is controlled by use of a change of a phase shift detected using a signal representing a phase shift detected from the extracted pilot signal. - View Dependent Claims (2, 3, 4, 5)
an accumulator converting the extracted pilot signal with a chip rate by the despreading circuit into a pilot signal with a symbol rate;
wherein a phase shift detected from the pilot signal is a phase shift with a symbol rate outputted by the accumulator.
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3. A mobile station according to claim 2, wherein the oscillation frequency of the oscillator is controlled by use of the phase shift detected with a symbol rate.
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4. A mobile station according to claim 2, wherein the oscillation frequency of the oscillator is controlled by use of an average of the phase shift detected with a symbol rate during a set period.
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5. A mobile station according to claim 1, wherein the oscillator is a voltage-controlled oscillator.
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6. A base station for use with a mobile communication system multiplexing a plurality of communication channels using spread spectrum codes comprising;
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a spreading circuit spreading a pilot signal using the spread spectrum code assigned to the pilot signal;
an oscillator;
a radio frequency modulator modulating the spread pilot signal into a radio frequency band signal by use of an oscillation frequency of the oscillator; and
a radio frequency demodulator demodulating a radio frequency band signal transmitted from a mobile station by use of an oscillation frequency of the oscillator;
wherein the radio frequency band signal transmitted from a mobile station is a signal modulated with a carrier controlled by use of a phase shift detected from the pilot signal. - View Dependent Claims (7)
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8. A mobile station for use with a mobile communication system multiplexing a plurality of communication channels using spread spectrum codes comprising:
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an oscillator;
a radio frequency demodulator demodulating a radio frequency band signal transmitted from a base station by use of a signal form the oscillator;
a first despreading circuit extracting a data signal by despreading the demodulated radio frequency band signal using the spread spectrum code assigned to the data signal;
a second despreading circuit extracting a pilot signal by despreading the demodulated radio frequency band signal using the spread spectrum code assigned to the pilot signal; and
a phase correction circuit performing phase correction for the data signal by use of a phase shift detected from the extracted pilot signal;
wherein an oscillation frequency of the oscillator is controlled by use of a signal representing the phase shift. - View Dependent Claims (9, 10, 11, 12, 13)
an accumulator converting the extracted pilot signal with a chip rate by the second despreading circuit into a pilot signal with a symbol rate;
wherein a phase shift detected from the pilot signal is a phase shift with a symbol rate outputted by the accumulator.
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10. A mobile station according to claim 9, further comprising:
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an averaging circuit averaging the phase shift with a symbol rate during a first period;
wherein the phase correction circuit performs phase correction for the data signal by use of the averaged phase shift.
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11. A mobile station according to claim 9, wherein the oscillation frequency of the oscillator is controlled by use of the phase of the phase shift detected with a symbol rate.
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12. A mobile station according to claim 10, wherein the oscillation frequency of the oscillator is controlled by use of an average of the phase of the phase shift detected with a symbol rate during a second period that does not exceed the first period.
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13. A mobile station according to claim 8, wherein the oscillator is a voltage-controlled oscillator.
Specification