An improved block CFO estimation algorithm based on zadoff-chu pilot sequence for LDACS in UAV channel

The L-Band Digital Aeronautical Communication System (LDACS) is a typical pilot-aided orthogonal frequency division multiplexing (OFDM) communication system. With the performance of LDACS in the Unmanned Aerial Vehicle (UAV) over-water channel, the pilot is redesign based on Zadoff-Chu (ZC) sequence. The new periodic ZC-pilot could reduce the effects of noise by correlated calculation. Based on new ZC-pilot, an improved block frequency offset estimation algorithm is proposed. The frequency offset of data frame is estimated and compensated by block pilots correlated calculation, which eliminates the influence of residual Doppler effect. The simulation results show that the stability and convergence of the block frequency offset estimation algorithm are much better than one-shot estimation algorithm. Besides, the proposed algorithm could obtain approximately 6dB performance gain in aviation enroute channel, while 4dB in the UAV over-water channel. Compared with the loop-filtering algorithm, the proposed algorithm has similar carrier-frequency offset (CFO) tracking performance and bit error rate (BER) performance, but saves 80% multiplexing resources, which leads to lower transmission latency and computational complexity.