| Popis: |
The BER degradation caused by imperfect channel estimation as well as the adverse effect of jamming on pilot symbols, which are used for the channel estimation (CE), is often neglected while analyzing OFDM und MC-CDMA systems leading to over-optimistic results. Therefore, to provide a more realistic analysis, we analyze the vulnerability of pilot symbol aided CE schemes for OFDM/MC-CDMA systems to narrowband and partial band jamming. We derive closed form BER expressions for studying the effect of imperfect CE for OFDMA/MC-CDMA in the absence of jamming in a frequency selective Rayleigh fading environment. We extend these results via simulations and theory (wherever permitted by mathematical tractability) to account for jamming. Some possible solutions such as the use of boosted pilots and the use of jamming side information, whenever available, to excise the jammed pilots or provide MMSE equalization are proposed to reduce the impact of jamming on the CE. |
