Performance limitation of M-ary pulse position modulation and on-off keying in a direct detection optical wireless communication system

Performance analysis is carried out for an optical wireless link in the presence of atmospheric scintillation using OOK and M-ary PPM modulation schemes. The bit error rate (BER) performance results evaluated at a bit rate of 1 Gbps show that system suffers significant penalty in required photon count per bit to achieve a given BER due to atmospheric scintillation effect. It is noticed that penalty is approximately 128.2, 186.7, 215 and 356.6 photons per bit corresponding to OPPM, QPPM, OOK and BPPM respectively at a scintillation variance of 0.01.