Adapted LDPC Error Correction Scheme for 2D Optical CDMA Multimedia System
Résumé
To provide multimedia services in optical networks, 2 Dimensional Optical Code Division Multiple Access (2D OCDMA) system is considered as a potential solution. We focus here on a 2D OCDMA system using 2D multi-weight codes and parallel mapping technique to provide respectively Quality of Service (QoS) and data rate differentiation. To improve the performance of such a scheme, we investigate Forward Error Correction (FEC) based on Low Density Parity Check (LDPC) codes known to have an efficient error correction power for Gaussian channels. We particularly propose an adaptation of the LDPC decoding scheme to the 2D OCDMA multimedia channel which has a specific noise distribution due to Multiple Acces Interference (MAI). We evaluate the system robustness to Additive White Gaussian Noise (AWGN) perturbation in addition to MAI and the gain provided in term of SNR. Finally, we show that the adapted FEC scheme we propose, not only permits improving the data rate per service but also the number of simultanously communicating users.