BACKGROUND

1. Field

The inventive concept relates to a satellite signal relay system.

2. Description of the Related Art

In recent years, in response to a decrease in cell size and an increase in the number of cells in a service coverage due to a rapid increase in mobile traffic, a plurality of mobile communication service providers adopt a distributed type mobile communication base station structure in which a baseband unit (or a digital unit), which is a data processing unit of a base station, is arranged in a central office and a plurality of remote radio units, which are signal transmission and reception units of the base station, are separately arranged in a remote site. In addition, the plurality of mobile communication service providers centrally install a plurality of baseband units in the central office to optimize base station performance and efficiency, and to facilitate management and operation.

Each of the plurality of baseband units uses a satellite signal, for example, a global positioning system (GPS) signal, as a reference signal for synchronization. In this case, it is required to additionally provide a dedicated antenna for receiving satellite signals for each of the plurality of baseband units, so that costs for constructing the base station may increase, and efficiency of space utilization may be lowered. Furthermore, if the plurality of baseband units cannot receive satellite signals due to installation environment of the plurality of baseband units, jamming, or the like, synchronization becomes impossible and a service failure occurs.

SUMMARY

The inventive concept is directed to a satellite signal relay system capable of reducing construction cost of a mobile communication base station, improving spatial and installation efficiency, and preventing occurrence of a service failure, thereby improving service reliability of a base station.

According to an aspect of the inventive concept, a satellite signal relay system includes a plurality of remote units configured to receive an analog satellite signal, to convert the analog satellite signal into a digital satellite signal, to generate a characteristic signal for the analog satellite signal, to generate a transmission frame based on the digital satellite signal and the characteristic signal, and to convert the transmission frame into an optical transmission frame; and a central unit configured to convert optical transmission frames received from the plurality of remote units into transmission frames through an optical transmission medium, respectively, to extract a digital satellite signal and a characteristic signal from each of the converted transmission frames, and to convert any one of the extracted digital satellite signals into an analog satellite signal based on the extracted characteristics signals.

In an example embodiment, each of the plurality of remote units may detect characteristic information of the analog satellite signal, and may generate the characteristic signal based on the detected characteristic information.

In an example embodiment, the characteristic information may indicate a carrier-to-noise ratio (CN) of the analog satellite signal.

In an example embodiment, each of the plurality of remote units may receive a delay measurement signal received from the central unit through the optical transmission medium, and may generate the transmission frame based on the delay measurement signal, the digital satellite signal, and the characteristic signal such that the delay measurement signal is retransmitted to the central unit.

In an example embodiment, each of the plurality of remote units may include a remote-side RF processor configured to perform low-noise amplification on the analog satellite signal, to frequency down-convert the low-noise amplified analog satellite signal, and to filter and output the frequency down-converted analog satellite signal; an analog-to-digital converter configured to convert the filtered analog satellite signal into the digital satellite signal; a remote-side detector configured to detect characteristic information on the analog satellite signal distributed from the remote-side RF processor; a remote-side controller configured to generate the characteristic signal based on the detected characteristic information; a remote-side digital processor configured to generate the transmission frame based on the digital satellite signal received from the analog-to-digital converter and the characteristic signal received from the remote-side controller; and a remote-side optical transceiver configured to convert the transmission frame into the optical transmission frame and to transmit the optical transmission frame to the central unit through the optical transmission medium.

In an example embodiment, the remote-side digital processor may include a remote-side framer configured to generate the transmission frame based on the digital satellite signal and the characteristic signal.

In an example embodiment, the remote-side digital processor may include a remote-side deframer configured to extract a delay measurement signal from an optical transmission frame that is received from the central unit through the optical transmission medium, wherein the remote-side framer may generate the transmission frame based on the delay measurement signal, the digital satellite signal, and the characteristic signal received from the remote-side deframer.

In an example embodiment, the converted transmission frames may further include a delay measurement signal that each of the plurality of remote units retransmits to the central unit, wherein the central unit may measure a delay value for each of the plurality of remote units based on a delay measurement signal included in each of the converted transmission frames, may compensate for a delay of the extracted digital satellite signals based on at least one of the measured delay values and a predetermined delay value, and may convert any one of the delay-compensated digital satellite signals into the analog satellite signal based on the extracted characteristic signals.

In an example embodiment, the central unit may include a center-side optical transceiver configured to convert the optical transmission frames received from the plurality of remote units into the transmission frames through the optical transmission medium, respectively; a center-side digital processor configured to extract the digital satellite signal and the characteristic signal from each of the transmission frames received from the center-side optical transceiver, and to selectively output any one of the extracted digital satellite signals; a digital-to-analog converter configured to convert the digital satellite signal output from the center-side digital processor into the analog satellite signal; and a center-side RF processor configured to frequency up-convert the analog satellite signal.

In an example embodiment, the center-side digital processor may include a plurality of center-side deframers configured to extract a digital satellite signal and a characteristic signal from a corresponding one of the transmission frames received from the center-side optical transceiver; and a selector configured to selectively output any one of the extracted digital satellite signals.

In an example embodiment, the central unit may further include a center-side controller configured to control the selector such that any one of the extracted digital satellite signals is selectively output based on the characteristic signals received from the plurality of center-side deframers.

In an example embodiment, the converted transmission frames may further include a delay measurement signal that each of the plurality of remote units retransmits to the central unit, wherein the center-side digital processor may extract the digital satellite signal, the characteristics signal, and the delay measurement signal from each of the transmission frames received from the center-side optical transceiver, may compensate for a delay of the extracted digital satellite signals, and may selectively output any one of the delay-compensated digital satellite signals.

In an example embodiment, the center-side digital processor may include a plurality of center-side deframers configured to extract a digital satellite signal, a characteristic signal, and a delay measurement signal from a corresponding one of the transmission frames received from the center-side optical transceiver; a plurality of delay compensators configured to compensate for a delay of a digital satellite signal received from a corresponding one of the plurality of center-side deframers; and a selector configured to selectively output any one of the delay-compensated digital satellite signals received from the plurality of delay compensators.

In an example embodiment, the central unit may further include a center-side controller configured to measure a delay value for each of the plurality of remote units based on a delay measurement signal transmitted to the plurality of center-side deframers, to control the plurality of delay compensators such that the delay of the digital satellite signals is compensated based on at least one of the measured delay values and a predetermined delay value, and to control the selector such that any one of the delay-compensated digital satellite signals is selectively output based on the characteristic signals received from the plurality of deframers.

According to another aspect of the inventive concept, a satellite signal relay system includes a remote unit configured to receive an analog satellite signal, to convert the analog satellite signal into a digital satellite signal, to generate a transmission frame based on the digital satellite signal, and to convert the transmission frame into an optical transmission frame; and a central unit configured to convert an optical transmission frame received from the remote unit through an optical transmission medium into a transmission frame, to extract a digital satellite signal from the converted transmission frame, and to convert the digital satellite signal into an analog satellite signal.

In an example embodiment, the analog satellite signal may be a signal received from a global positioning system (GPS) satellite.

In an example embodiment, the remote unit may receive a delay measurement signal received from the central unit through the optical transmission medium, and may generate the transmission frame based on the delay measurement signal and the digital satellite signal such that the delay measurement signal is retransmitted to the central unit, wherein the central unit may extract the digital satellite signal and the delay measurement signal from the converted transmission frame, may measure a delay value for the remote unit based on the extracted delay measurement signal, may compensate for a delay of the extracted digital satellite signal based on at least one of the measured delay value and a predetermined delay value, and may convert the delay-compensated digital satellite signal into the analog satellite signal.

In an example embodiment, the central unit may transmit the analog satellite signal to at least one baseband unit constituting a base station through a predetermined transmission medium.

A satellite signal relay system according to embodiments of the inventive concept may reduce construction cost of a mobile communication base station, improve spatial and installation efficiency, and prevent occurrence of a service failure, thereby improving service reliability.

