الفهرس 
Introduction
3G cdma2000Only 14 pages are availabe for public view
 |  | from | 136 |  |  |
| | | from | 136 | | |
Abstract
In the present work, the performance of multicarrier direct sequence code-division multiple-access MC-DS-CDMA system over multipath Nakagami-m fading channels is considered. Two main types of multicarrier techniques, are defined. The first type spreads the original data stream using a spreading code and then modulates different carriers with each chip. This is usually referred to as MC-CDMA . The second type spreads the serial to parallel converted streams using a spreading code after the parallel streams modulates different subcarrier frequencies. This is usually referred to as MC-DS-CDMA. The system performance is evaluated in terms of the bit error rate (BER) using three different combining schemes of diversity receivers. The first type is maximal ratio combining (MRC) which requires the individual signals from each path to be time aligned, cophased, optimally weighted by their own fading amplitude, and then summed. The second type is selection combining (SC) which processes one of the diversity branches, specifically, the one determined by the receiver to have the highest SNR. The third type is Generalized selection combining (GSC), which is a hybrid scheme involving first conventional SC followed by MRC. More specifically the SC chooses from the received signals the largest ones and then optimally weights (as per the rules of MRC) and sums these to produce the decision statistic