Iterative equalization and decoding for the GSM-system

In iterative equalization and decoding (“turbo-detection”) the “turbo-principle” is used for detection of coded data transmitted over a frequency selective channel. Due to the burst and interleaver structure the turbo-detection scheme cannot be adopted to the GSM without modifications. We present some possibilities to adopt turbo detection to TDMA systems with interblock-interleaving like GSM and show that the turbo principle also works very well if extrinsic information is not available for all bits. Furthermore, we show that turbo-detection is a suitable method to improve the bit error rate not only of protected bits but also of bits transmitted uncoded in a system with unequal error protection, e.g. the class 2 bits in the GSM speech channel