hierarchical modulation and demodulation method and apparatus of the OFDM transmission systems

摘要

A method and an apparatus for hierarchical modulation/demodulation in an OFDM(Orthogonal Frequency Division Multiplexing) system are provided to perform an in-phase demodulation by using a pilot which is transferred to a second layer. A hierarchical modulation apparatus in an OFDM system includes first and second encoders(110,120), a pilot insertion unit(130), and a hierarchical modulation unit(140). The first encoder encodes a first layer signal stream, which is a basic layer signal. The second encoder encodes a second layer signal stream which is an enhancement layer signal. The pilot insertion portion inserts a pilot signal for estimating a channel coefficient to an encoded second layer signal stream. The hierarchical modulation portion modulates the second layer signal stream, to which the pilot signal is inserted, and the encoded first layer signal stream, and combines the encoded signals with each other.