Relay system in ring topology

A unit of digital radio frequency transport system, comprising:

• a first processor configured to receive a de-framed first signal from a first transport processing path while operating in a first mode, receive another de-framed first signal from a second transport processing path while operating in a second mode, and perform digital processing on a service signal in the de-framed first signal and the other de-framed first signal, wherein the service signal is transmitted to a user terminal;
• a second processor configured to perform digital processing on a terminal signal transmitted from the user terminal, transmit the digital processed terminal signal to the second transport processing path while operating in the first mode, and transmit the digital processed terminal signal to the first transport processing path while operating in the second mode;
• and
• a controller configured to switch between the first mode and the second mode for each of the first processor and the second processor based on a mode control signal,
• wherein the de-framed first signal is a signal generated by the first transport processing path de-framing a first signal transmitted from a first adjacent unit through a first transmission medium, and the other de-framed first signal is generated by the second transport processing path de-framing the first signal transmitted from the first adjacent unit through the first transmission medium, and
• wherein the first transport processing path comprises:
• a de-framer configured to de-frame the first signal transmitted from the first adjacent unit through the first transmission medium, transmit the de-framed first signal to the first processor while operating in the first mode, and de-frame a second signal transmitted from a second adjacent unit through a second transmission medium while operating in the second mode;
• and
• a framer configured to frame the de-framed first signal while operating in the first mode, and frame a signal, which is generated by summing the de-framed second signal and the digital processed terminal signal transmitted from the second processor, while operating in the second mode.