A HMM-Based Spectrum Access Method Used for HF Communication

Aiming at the drawbacks of spectrum access strategy based on listening before transport in HF ALE protocols, a modified HMM is proposed to predict the channel availability and decide channel access. Giving full consideration to the usage regulation of HF channel, this model makes better use of the ´partially available´ channel which is considered as ´occupied´ under traditional two-state channel partition mechanism by a three-state one. The simulation results tells that in comparison to existing two-state HMM, this method uses channel longer with a lower switch rate and has higher predicting accuracy and channel utilization compared with traditional listening before transport strategy especially when ´partially available´ channel appears frequently or SNR is low.