A Modular Encoder Design Scheme for Turbo-ncoded BPPM-OCDMA System
Source: NORTH ATLANTIC UNIVERSITY UNION
A Turbo-encoded Optical Code Division Multiple Access (OCDMA) system has been simulated and an application specific design process has been proposed to implement a Turbo-encoded OCDMA modulated using Binary Pulse Position Modulation (BPPM) for transmission over optical fiber channels. The design process follows a modular approach and consists of four distinct modules RSC (Recursive Systematic Code) encoder, Pseudorandom Interleaver, Parallel to Serial Converter, BPPM circuit. A reference system has been designed for a frame size of 16 bits. Bit error rates were calculated for this reference design, assuming 10 simultaneous users using 5 iterations of the MAP decoding algorithm at various values of SNR for the two obtainable code rates (1/2; 1/3).