Novel block coding method for rate-adaptive optical wireless communications systems

In this paper, a novel rate-adaptive transmission scheme using block codes with codewords of variable Hamming weight is presented. This coding scheme is based on a multiplepulse position modulation (MPPM) technique, where codewords with different Hamming weight are allowed, including the all-zero one. The performance analysis of this new scheme has been presented by comparing with on-off keying (OOK) formats with memory and the HHH(1,13) code proposed and specified in the Very Fast Infrared (VFIr) standard by the Infrared Data Association (IrDA), but operating under a rate-adaptive transmission environment. The superiority of the block coding method has been corroborated, being the improvement in performance higher as the length of the data block is increased. Additionally, the use of very simple decoding schemes based on ML detection has been proposed as alternative to the procedure based on the Viterbi algorithm. Finally, an improved rate-adaptive capability is provided by the translation table adopted in the block coding here proposed, leading to an attractive adaptation procedure by swapping between proper translation tables.