Comparative Study of Polar Codes with QPSK and High-Order QAM in AWGN Channels

الملخص

This work provides a comprehensive evaluation of communication systems employing quadrature phase-shift keying (QPSK) and high-order quadrature amplitude modulation (QAM) schemes (16-QAM to 2048-QAM) over additive white Gaussian noise (AWGN) channels. The study compares uncoded transmission with polar-coded systems to assess error-correction efficacy. Important measurements like bit error rate (BER) receive thorough evaluations via comprehensive simulations. Without polar codes, high-order QAM (e.g., 2048-QAM) exhibits significantly higher BER, particularly at low signal-to-noise ratios (SNRs), due to increased noise susceptibility. In contrast, QPSK maintains robustness owing to its lower information rate. Monte Carlo simulations are conducted to measure BER performance across modulation schemes, both with and without polar codes. The polar code construction employs successive cancellation decoding, with code rates optimized for each modulation order. Channel conditions are modeled using AWGN with varying signal-to-noise ratios (SNRs). Polar codes markedly improve error resilience across all modulation schemes: QPSK achieves near-error-free performance, while high-order QAM schemes show substantial BER reductions. However, polar codes’ effectiveness diminishes with higher modulation orders. For example, 2048-QAM requires significantly greater computational effort for marginal gains in spectral efficiency. The study highlights a critical trade-off: uncoded high-throughput QAM systems achieve higher data rates but suffer from elevated BER, whereas polar-coded systems prioritize reliability at the expense of throughput. Practical recommendations are provided for selecting modulation-code pairings tailored to channel conditions. These insights are vital for designing adaptive communication systems that balance data rate requirements with error-correction capabilities in AWGN environments.