Orthogonal frequency division multiplexing (OFDM) systems are inherently vulnerable to jamming attacks due to the independent transmission of data symbols across subcarriers. In this paper, we propose a novel anti-jamming OFDM scheme to ensure robust communication even under severe jamming attacks while maintaining high spectral efficiency. The core idea is to utilize a spreading matrix that transforms a data symbol vector into a higher-dimensional modulated vector, thereby exploiting both the spreading gain and the frequency diversity gain to mitigate jamming attacks. To recover the transmitted data symbols, we develop an efficient maximum likelihood detection (MLD) method that achieves optimal detection performance with significantly reduced computational complexity. Furthermore, we derive the theoretical bit error rate (BER) upper bound and the optimal modulation order that minimizes the BER while preserving spectral efficiency according to the jamming environment. To address practical scenarios where jamming attacks are unknown and dynamic, we establish a jamming-adaptive communication framework. This framework enables the system to estimate the jamming parameters and adapt to the dynamic environment with the optimal modulation order. Simulation results demonstrate that the proposed scheme significantly outperforms existing OFDM schemes in both BER and effective throughput, validating its robustness under various and dynamic jamming scenarios.

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