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A hybrid mo-demodulation approach, fully insensitive to the phase noise induced by the sources, is described for CDMA applications at optical frequencies. It is analytically demonstrated that, using bipolar codes in conjunction with polarisation modulation, the considered system can improve the performance of coherent schemes with not negligible laser linewidths, as well as the performance of more conventional noncoherent schemes based on intensity modulation and unipolar codes.
Franco CHIARALUCE Ennio GAMBI Marta MAZZONE
Two new algorithms are introduced, respectively called syndrome erasing and double syndrome decoding, which permit to achieve fast error correction with a wide class of cyclic codes.
Franco CHIARALUCE Ennio GAMBI Giorgia RIGHI
This paper extends previous analytical approaches for the study of CDMA systems to the relevant case of multipath environments where users can operate at different bit rates. This scenario is of interest for the Wideband CDMA strategy employed in UMTS, and the model permits the performance comparison of classic and more innovative spreading signals. The method is based on the characteristic function approach, that allows to model accurately the various kinds of interferences. Some numerical examples are given with reference to the ITU-R M.1225 Recommendations, but the analysis could be extended to different channel descriptions.
Franco CHIARALUCE Ennio GAMBI Roberto GARELLO Paola PIERLEONI
A performance comparison is developed between a chaotic communication system and a spread spectrum system with similar features in terms of bandwidth and transceiver structure but based on more conventional Gold sequences. Comparison is made in the presence of noise and multipath contributions which degrade the channel quality. It is shown that, because of its more favourable correlation properties, the chaotic scheme exhibits lower error rates, at a parity of the bandwidth expansion factor. The same favourable correlation properties are also used to explain and show, through a numerical example, the benefits of chaotic segments in a multi-user environment.
Andrea BORELLA Franco CHIARALUCE
We propose a modification of the perfect shuffle connectivity graph used in optical networks, which ensures the balance of the traffic load on the WDM channels. When applied to the simple but popular case of 8 nodes, connected through a shortest path routing algorithm, it allows to increase the aggregate capacity of more than 14%.