EVM Based HF Adaptive Modulation

High frequency (HF) communications may face interference, and the conventional signal-to-noise ratio (SNR) based adaptive modulation cannot fully reflect the HF channel state information. This paper proposes an error vector magnitude (EVM) based adaptive modulation mechanism for HF communication. EVM is first demonstrated that it can be applied to the design of HF adaptive modulation system where interference may be present. On this basis, the EVM threshold can be determined under the constraint by the relationship between EVM and symbol error rate, and then the design of the adaptive modulation mechanism is completed. Simulation results further show that EVM can better characterize HF channel state and interference, and is suitable as a channel state parameter for HF communication systems. In particular, compared to traditional SNR based adaptive modulation, the proposed approach can get higher spectrum utilization while the complexity is kept low.