Combined iterative demapping and decoding for coded UWB-IR systems

This paper presents a novel decoding strategy, called combined iterative demapping/decoding (CIDD), for coded ultra wideband impulse radio (UWB-IR) systems. From the viewpoint of coding, coded UWB-IR systems can be viewed as a class of serially concatenated coding, because channel encoder and pulse mapper in the UWB-IR systems plays a role of outer and inner encoder in serial concatenated coding, respectively. For serially concatenated coding, it is well known that iterative decoding between the inner and outer decoder brings additional coding gain by using a soft-in/soft-out (SISO) decoding algorithm. In this paper, we derive a SISO algorithm for pulse demapper based on a max log-maximum a posteriori probability (MAP) algorithm to make the CIDD applicable, and then we show that this CIDD strategy improves the error rate performance with a reasonable complexity from simulation results. By applying the CIDD, larger coding gain is achieved with less computational complexity than turbo coded systems.