Convolutional coded dual header pulse interval modulation for line of sight photonic wireless links

The analysis and simulation for convolutional coded dual header pulse interval modulation (CC-DH-PIM) scheme using a rate 1/2 convolutional code with the constraint length of 3 is presented. Decoding is implemented using the Viterbi algorithm with a hard decision. Mathematical analysis for the slot error rate (SER) upper bounds is presented and results are compared with the simulated data for a number of different modulation techniques. The authors show that the coded DH-PIM outperforms the pulse position modulation (PPM) scheme and offers > 4 dB code gain at the SER of 10^-4 compared to the standard DH-PIM. Results presented show that the CC-DH-PIM with a higher constraint length of 7 offers a code gain of 2 dB at SER of 10^-5 compared to the CC-DH-PIM with a constraint length of 3. However, in CC-DH-PIM the improvement in the error performance is achieved at the cost of reduced transmission throughput compared to the standard DH-PIM.