Turbo-Codes and Turbo-Coded Modulation in CDMA Mobile Radio Systems for Short Frame Transmission

Abstract | Recently, binary parallel concatenated recursive convolutional codes termed Turbo-Codes received great atten-tion due to their amazing error correcting capabilities. Nev-ertheless, reaching near Shannon limit performance is only possible with very large interleavers prohibiting an applica-tion in speech-transmission. This paper presents simulation results for a short-frame data transmission system based on DS-CDMA (Direct-Sequence Code Division Multiple Access) employing Turbo-Codes. Furthermore, the performance of a turbo-coded modulation scheme is investigated with respect to the typical conditions of DS-CDMA systems. As a result, it is shown that Turbo-Codes are no longer superior to classical convolutional codes if the same decoding costs are assumed. Additionally, simulation results illustrate that coded modula-tion schemes are not well suited for the application in CDMA systems. Finally, it is proved that an accurate channel estima-tion is necessary for allowing of high coding gains. I