Time Division Duplex (TDD)-based bidirectional digital field pick-up unit (FPU) system is now being studied. Hence this new digital FPU system shares its frequency band with other wireless systems, digital FPU system should detect and avoid the interference from other systems. We studied the frequency sensing scheme using received power within preamble signals. From the results of indoor experiment, it was confirmed that the proposed scheme achieved an excellent performance of interference detection.
