Optical wireless LDPC-coded PPM with unequal transmission power allocation scheme

In this paper, the low density parity check (LDPC) coded schemes with unequal transmission power allocation (UTPA) in optical wireless channel is evaluated. In particular, the bit error rate performance of the LDPC coded binary pulse position with UTPA is investigated in the presence of APD noise, thermal noise, scintillation. Consequently, the BER performance of the LDPC coded pulse position modulation with UTPA is better than that of the conventional LDPC coded pulse position modulation. It is found that there is optimum power ratio (R) and optimum R is varied by each average received laser power per slot (P_w). For example, when variance of scintillation is 0.1, the optimum R is 4.0 at P_w =-50[dBm]. Thus, the LDPC coded pulse position modulation with UTPA system is superior to the conventional system with R=1.0.