DEMODULATION METHOD OF MOBILE COMMUNICATION SYSTEM SUPPORTING MULTI-LEVEL MODULATION AND DEVICE THEREFOR

摘要

PURPOSE: A demodulation method of a mobile communication system supporting multi-level modulation and a device therefor are provided to demodulate high order modulation signals, by transforming a mobile station receiving unit of an ordinary CDMA(Code Division Multiple Access) mobile communication system at minimum. CONSTITUTION: Receiving signals loaded on a carrier are converted to baseband signals by mixers(310,315), pass a baseband interface filter(320) and inputted to a PN(Pseudo-random Noise) despreader(330) to be PN-despreaded with a corresponding PN code, then inputted to a channel estimator(340) and N Walsh despreaders(350). The channel estimator(340) extracts a pilot channel signal to decide a channel estimation signal, and outputs the channel estimation signal to a symbol demodulator(360). The Walsh despreaders(350) generate signals by the symbol by using a corresponding Walsh code of a packet channel, and symbols outputted in the N Walsh despreaders(350) are inputted to the symbol demodulator(360). The symbol demodulator(360) compensates phase distortion of a Walsh-despreaded data symbol by using the channel estimation signal and arranges symbols divided into N channels to calculate a soft decision value, then outputs the calculated soft decision value to a block deinterleaver(370). The soft decision value outputted from the symbol demodulator(360) is collected by the frame in the block deinterleaver(370) for block de-interleaving and inputted to a channel decoder(380). The channel decoder(380) receives outputs of the block deinterleaver(370) for decoding and restores original packet data.