Two-Level Spreading OFDM System Using Beamforming and Adaptive Code Assignment for Wireless Communication

Orthogonal frequency division multiple (OFDM) system with two-level spreading is an effective approach to suppress interference in wireless communication. However, in this system, the orthogonality of its spreading code can be destroyed by multipath fading. In this paper, we propose a novel resource allocation scheme that joints conventional two-level spreading OFDM and smart antenna so as to use beamforming to decrease multiuser interference in spatial domain. In order to achieve further interference suppression, we assign a proper spreading code at the transmitter and employ the zero-forcing equalizer at the receiver. Simulation results show that the new scheme is capable of achieving a significant improvement of efficiency for interference suppressing under multipath fading and jamming channels.