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Improvement of BER in LED based indoor communication using overlapping pulse position modulation and LDPC coding

Indoor optical wireless communication systems provide an attractive alternative for realizing next generation wireless local area network. Free space optical (FSO) communication suffers from several challenges in practical deployment. To overcome such limitation various modulation schemes are used. Generally modulation technique like on-off keying is used in visible light communication system to build a basic communication system. The schemes like combination of overlapping pulse position modulation - pulse width modulation (OPPM-PWM) are studied for visible light communication system. Then bit error rate analysis of these schemes is compared. A Linear error correcting code low-density parity-check (LDPC) scheme is introduced to see the change in the performance of the system. From the bit error rate analysis of these schemes it is seen that the system model with LDPC performs better than just with the modulation techniques.