A wideband DS-CDMA modem for a mobile station

This paper presents the design, implementation and test results of a complete wideband CDMA modem with a modulator and a demodulator for use in next-generation mobile stations. The modem is based on NTT DoCoMo´s proposal for the next generation W-CDMA air interface. The modulator supports multicode transmission capability, which enables three dedicated physical channels to be transmitted under a single radio link identification. The receiver consists of a searcher, three fingers and combiner and each finger can demodulate three dedicated physical channels simultaneously. For coherent QPSK data demodulation, a novel phase estimation algorithm has been employed. In this algorithm, a finger selects the minimum value after comparing four phase prediction values to the previous one to compute the correct phase. It has been shown that the proposed algorithm outperforms the WMSA proposed by NTT DoCoMo. The proposed mobile station modem was implemented with FPGAs and verified by the board-level experiment. Experiments have verified that the modem fully complies with the specification and is capable of up to 384 kbps data transmission when using multicode transmission.