Reconfigurable filtered OFDM waveform for next generation air-to-ground communications

To meet an ever increasing demand of the spectrum for communication between aircrafts and ground terminals, orthogonal frequency division multiplexing (OFDM) based L-band (960–1164MHz) Digital Aeronautical Communication System (LDACS) has been recently proposed as an alternative to existing narrowband systems. However, OFDM based LDACS needs additional control signaling for time and frequency alignment and the use of cylic prefix and high out-of-band emission limits the spectrum utilization efficiency to less than 50%. In this paper, a new waveform has been proposed which offers better spectrum utilization than OFDM without compromising on computational complexity and interference to legacy users in L-band. It also allows transceivers to dynamically adapt the transmission bandwidth to meet the desired quality of service. Since the proposed waveform employs a reconfigurable multiband linear phase filter, it is referred as reconfigurable filtered OFDM (RF-OFDM). Simulation results and extensive analysis show that the proposed RF-OFDM offers around 40 dB better out-of-band emission than OFDM which in turn leads to significant increase in the transmission bandwidth for a given BER and interference constraints. The computational complexity of RF-OFDM is slightly higher than that of OFDM but it is significantly less than other waveforms making RF-OFDM an attractive waveform for next generation air-to-ground communications.