Equalization and Decoding for IRDA RLL-Coded Systems

Very fast infrared (VFIr) was promoted by the IrDA for data rate of 16 Mb/s. VFIr adopts HHH (1,13) code (a kind of run length limited/RLL code) to avoid ISI problems. With the increase of data rate, the effect of component and channel induced inter-symbol interference (ISI) becomes more and more crucial and cannot be compensated easily only by HHH-code´s property. In this paper, we examine several possible approaches to deal with ISI problems in IrDA RLL-coded systems; joint equalizing and decoding methods for such systems are also discussed. Since the computational complexity of optimal joint receiver is quite high, we also provide sub-optimal algorithms, which are directly modified from the soft-decoder for HHH code without increasing the number of states of the encoding trellis. The simulation results show that our algorithm does yield good performance. Based on our sub-optimal algorithm, we provide the corresponding code design criterion so that the performance penalty can be further reduced