Adaptive Polar-Coded LiFi-OFDM for UAV Communications

In this paper, we present a simulation study of a joint Polar-coded Adaptive OFDM-LiFi communication system for short-range UAV applications. The proposed framework integrates Arikan's polar codes (N=256, R=1/2) with a four-order adaptive modulation engine (BPSK/QPSK/16-QAM/64-QAM) governed by SNR-dependent switching thresholds derived from a BER target of 10⁻³. The channel polarization is constructed via a closed-form SNR-adaptive Bhattacharyya recursion that updates the frozen set at each SNR operating point to track atmospheric scintillation variations. A log-normal turbulence model parameterized by the Rytov variance (σR² ∈ {0.0, 0.1, 0.5, 1.5}) is employed; this model is validated for σR² ≤ 1.0, and results at σR² = 1.5 are interpreted as conservative baselines only. A min-sum Successive Cancellation (SC) decoder with O(N log N) = 2048 operations per codeword and ~4 kB memory is employed, confirming feasibility on UAV-class embedded processors. Simulation results under perfect-CSI and static-geometry assumptions (upper bounds) show: under AWGN, a peak polar coding gain of 8–10 dB and a combined Polar+Adaptive gain of up to 12 dB over a conventional fixed-QPSK baseline; under moderate turbulence (σR² = 0.5), gains of 12–22 dB are observed. The adaptive system achieves 47.6% throughput improvement and 13.7% capacity improvement over the conventional system at SNR = 20 dB. Identified limitations include: static UAV geometry (pointing errors neglected), perfect CSI assumed (no pilot overhead), LED nonlinearity not modeled, and log-normal model applied at σR² = 1.5. All gains are simulation-based upper bounds requiring hardware prototype validation.