Adaptive frequency diversity OFDM (AFD-OFDM) communication system in the narrow-band interference channel

We study FD-OFDM (frequency diversity orthogonal frequency division multiplexing) system in the narrow-band jamming interference channel. Then, we propose an AFD-OFDM (adaptive FD-OFDM) to cope with the interference more adaptively. In FD-OFDM system, the information symbol of each parallel branch is multiplied by the orthogonal sequence and distributed into all subcarriers. So, each subcarrier transmits the orthogonally segmented information from the parallel branches in the FD-OFDM symbol duration. This FD-OFDM shows the frequency diversity characteristic. Therefore, FD-OFDM can be robust to the narrow-band jamming interference. But, the FD-OFDM also can´t suppress its performance loss in a very strong narrow-band jamming interference channel. So, in this paper, AFD-OFDM system is novelly proposed to countermeasure the deficiency of the FD-OFDM system, and it is very robust to the high power narrow-band jamming interference. In this AFD-OFDM, the overall system bandwidth is divided into several subbandwidths. Modulation level of each subbandwidth is adaptively controlled according to the channel environment. Therefore, it can get the high transmission throughput even in the severe channel condition. Simulation results show that this AFD-OFDM is better than the FD-OFDM in the strong narrow-band jamming interference.