Dual Cost Function Fractionally Spaced Blind Equalization Algorithm for Broadband UAV Communications

In unmanned aerial vehicle (UAV) communication systems, high-order quadrature amplitude modulation (QAM) signals are widely used for their high data rates. However, the complex UAV channel environment reduces the equalizer's processing speed, making it challenging for the equalization algorithm to converge effectively. To address this issue, this paper proposes a dual-cost function fractional spaced blind equalization algorithm. By integrating second-order statistical information with conventional blind equalization methods, the algorithm optimizes the equalizer coefficients at two distinct points within each symbol period of the fractionally spaced equalizer (FSE) using two cost functions. Additionally, a dual-mode algorithm and variable step-size function are introduced, enhancing both convergence stability and speed. Simulation results show that the proposed algorithm adapts well to various UAV communication environments. Compared to traditional blind equalization methods, it significantly improves equalization performance and interference resistance for high-order QAM signals. The steady-state residual inter-symbol interference (ISI) is greatly reduced, and the Bit Error Rate (BER) decreases by approximately one order of magnitude. This demonstrates that the proposed algorithm provides an efficient and effective blind equalization solution for broadband UAV communication.