Two-Path Serial Inter-Symbol-Interference Cancellation for Air-to-Ground Communication

The high Doppler effect and severe multipath delay are among the major challenges in air-to-ground (A2G) communication scenarios, where the maximum multipath delay may exceed the duration of one or more orthogonal frequency division multiplexing (OFDM) symbols, resulting in severe inter-symbol interference (ISI). In this letter, we propose a new frame structure constituted by grouped training sequences (GTSs), OFDM symbols and guard interval (GI). Specifically, two GTSs are respectively prefixed and postfixed to several cyclic-prefix-free OFDM symbols for Doppler frequency offset (DFO) and multipath delay estimation. Moreover, a two-path serial ISI cancellation (TSIC) algorithm is designed to recover the transmitted signal. Compared with existing algorithms, the new scheme can reduce errors and increase the spectral efficiency of the system.