Combined Coding and Spread Spectrum Modulatin in Wideband Code Division Multiple Access Communication Systems

In this paper, we introduce two techniques, recently proposed in (۱-۲], for combination of coding and spread spectrum modulation in wideband Code Division Multiple Access (CDMA) systems. These coding schemes, named as an internal coding, do not require extra bandwidth further than what is needed for a conventional uncoded spread spectrum system. They have been applied to both radio and optical ultra wideband code division multiple access communication systems. Their performance based on both analytical analysis and simulation for various radio and optical applications, and for a variety of single user and multiuser receivers, has been investigated. The results indicate that the internal coded schemes substantially outperform the conventional uncoded scheme, for the same transmitter powers and spectral efficiencies. Also, the various methods for providing multi services and multi rates for the internally coded systems have been introduced and their performance bas been investigated.