Wideband channel characterization for 3G/4G systems

The tendency of 3G/4G wireless communication systems is to support wideband access to achieve high bandwidth requirements of projected multimedia applications. Wideband communications systems suffer from frequency selective channels. Accordingly, 3G/4G systems have endorsed the concept of multi-carrier modulation such as OFDM and MC-CDMA, where the wideband channel is sub-divided into numerous sub-carriers. Each sub-carrier may be viewed as a flat fading channel. In that context, sub-carriers are usually modeled as independent Rayleigh channels with emphasis only on their average fade duration and level crossing rate parameters. In this paper, a thorough study of wideband frequency selective channels from the perspective of multi- carrier modulation systems is presented. The study investigates more adequate distributions than the Rayleigh distribution to represent the fading behavior of different individual sub-carriers. In addition, monitoring of the correlation among sub-carriers as well as studying of the notches behavior of the wideband channel is performed. Such parameters may be used to provide more insight on strategies for better sub-carrier and power allocation schemes in multi-carrier modulation systems.