Wireless access system and control method for same
Provided are a wireless access system provided with a remote unit capable of handling a high-frequency region without being made complicated, and a control method for the same. A wireless access system according to the present invention is provided with: a center unit ( 1 ); and a remote unit ( 3 ) that converts a baseband signal generated by the center unit ( 1 ) into a high-frequency signal and emits the high-frequency signal from an antenna ( 12 ). The center unit ( 1 ) includes a 1-bit modulator ( 5 ) that converts the baseband signal into a 1-bit signal on the basis of a generated clock signal and outputs the 1-bit signal. The remote unit ( 3 ) includes: a local generation unit ( 10 ) that extracts the clock signal from the 1-bit signal output from the center unit ( 1 ), and generates a local signal using the extracted clock signal as a reference signal; a filter ( 13 ) that extracts a desired band component from the 1-bit signal; and an up-converter ( 14 ) that converts, using the local signal, an output signal of the filter into a high-frequency signal.
1. A wireless access system comprising:
a center unit; and
a remote unit that is placed in a location away from the center unit, converts a baseband signal generated at the center unit to a high-frequency signal, and emits the high-frequency signal through an antenna, wherein
the center unit comprises a digital baseband that generates the baseband signal, an oscillator that generates a clock signal, and a 1-bit modulator that converts the baseband signal to a 1-bit signal, based on the clock signal, and outputs the 1-bit signal, and
the remote unit comprises a local generation unit that extracts a clock signal from the 1-bit signal output from the center unit and generates a local signal by using the extracted clock signal as a reference signal, a filter that extracts a desired band component from the 1-bit signal, and an up-converter that converts an output signal of the filter to the high-frequency signal by using the local signal.
2. The wireless access system according to claim 1 , wherein the 1-bit modulator comprises a ΔΣ modulator that performs ΔΣ modulation.
3. The wireless access system according to claim 1 , wherein the oscillator is capable of changing a clock rate of the clock signal to be generated.
4. The wireless access system according to claim 1 , wherein the filter is configured with a digital down-converter that performs down conversion and a lowpass filter that extracts desired signal components from quadrature signals output from the digital down-converter.
5. The wireless access system according to claim 4 , wherein:
the digital down-converter comprises a first selector that takes input of the 1-bit signal and outputs the 1-bit signal selectively to a plurality of paths, a second selector that takes input of a first signal among signals from the plurality of paths and an inverted signal of the first signal and alternately outputs the first signal and the inverted signal of the first signal, and a third selector that takes input of a second signal among signals from the plurality of paths and an inverted signal of the second signal and alternately outputs the second signal and the inverted signal of the second signal; and
the first selector, the second selector, and the third selector output output signals of the second selector and the third selector as the quadrature signals to the lowpass filter in synchronization with a clock signal extracted from the 1-bit signal.
6. The wireless access system according to claim 1 , wherein the remote unit comprises a down-converter that down-converts a high-frequency signal received from a terminal through the antenna to a low-frequency-band signal by using a local signal generated by the local generation unit or a second local signal generated by a second local generation unit by extracting a clock signal from the 1-bit signal and using the extracted clock signal as a reference signal.
7. The wireless access system according to claim 6 , wherein the remote unit comprises a ΔΣ analog-digital converter that converts a signal down-converted by the down-converter to a 1-bit signal.
8. A control method for controlling a wireless access system comprising a center unit and a remote unit that is placed in a location away from the center unit, converts a baseband signal generated at the center unit to a high-frequency signal, and emits the high-frequency signal through an antenna, the control method comprising:
converting, by the center unit, a baseband signal to a 1-bit signal by using a clock signal;
transmitting, by the center unit, the 1-bit signal to the remote unit;
extracting, by the remote unit, a clock signal from the 1-bit signal;
generating, by the remote unit, a local signal by using the extracted clock signal as a reference signal;
extracting, by the remote unit, a desired band component from the 1-bit signal; and
converting, by the remote unit, the desired band component to the high-frequency signal by using the local signal.
9. The control method according to claim 8 , further comprising changing, by the center unit, a clock rate of the clock signal.
10. The control method according to claim 8 , further comprising down-converting, by the remote unit, a high-frequency signal received from a terminal through the antenna to a low-frequency-band signal by using the local signal or a second local signal generated by using the extracted clock signal as a reference signal.