Multicarrier Spectral Shaping for Non-White Interference Channels: Application to Aeronautical Communications in the L-Band

Adaptive radio techniques have been extensively studied over the past two decades. In this paper, we investigate an adaptive algorithm to attain additive white Gaussian noise (AWGN) performance in non-white channels, using multicarrier communications such as OFDM and filter-bank multicarrier (FBMC). The non-white channel can be from non-white noise, or more commonly, interference. Our proposed algorithm: spectral shaping (SS), follows a simple optimization problem to find what we term reliable subcarriers, and then per subcarrier power allocations are made in order to attain the AWGN channel bit error ratio (BER). Subcarriers that experience high interference are deactivated or chosen as guard subcarriers. After describing our analysis, we show some simulation results in two non-white interference signal examples: the Gaussian pulse shaped high-power distance measuring equipment (DME) and a classical rectangular-pulse signal. The DME example is pertinent for currently proposed aeronautical communication systems, where new multicarrier techniques, e.g., the L-band digital Aeronautical communication systems (LDACS) have been designed as an inlay approach between the high-power DME channels in L-band. Our results show that in high DME power interferences, using this adaptive technique can improve the overall reliability and attain AWGN BER performance in AWGN channel. We provide power spectral density (PSD) results to compare OFDM and FBMC based spectra when our SS algorithm is applied. Also, we provide BER vs. bit energy to noise density ratio (E-b/N-0) results in the AWGN, as well as more realistic aeronautical channels to compare SS system performance. Our results show that in the presence of high power DME interference, using this adaptive technique can improve the overall reliability and enable us to attain non-interference BER performance in realistic aeronautical channels.