Evaluation of the MAP decoder for the turbo codes of IMT-2000

One of the primacy ITU objectives for IMT-2000 is `improved operational efficiencies, particularly for data and multimedia services´. Data and multimedia services require the BER below 10^-6 . To do this, specification groups accepted the turbo code for one of the channel coding schemes. Even though the turbo code has good performance in itself the decoding complexity and its delay are critical points in implementing it. In this paper, various simulations are performed using standards proposed by 3GPP and 3GPP2. These two standards use CDMA in FDD mode. We use the AWGN environment to simulate them. In the specification by 3GPP2, 26 different turbo-encoding cases exist as the radio configuration (RC). In the specification by 3GPP, 4 cases exist as the data rate. We varied the data rate, code rate and the number of iteration for decoding according to Eb/No values. The performance of turbo decoders using max log-MAP and log-MAP are compared. Finally, the case using the window framing method and the case not using it are compared. As a conclusion, from the many simulation results, we propose various choices to the designers who want to design turbo decoder for the IMT-2000 system