Simulation and Experiment of Soft-Decision Decoding for Short-Frame Fountain Code Over Plasma Sheath Channel

A hypersonic vehicle is covered by a plasma sheath during flight, which seriously attenuates the power of electromagnetic (EM) waves and generates the so-called “radio blackout” phenomenon when the equivalent frequency of plasma is greater than the carrier frequency. However, the parameters of plasma sheath vary randomly with time. The variation produces some random time slots where the equivalent frequency of plasma is lower than the carrier frequency, so the EM waves can penetrate the plasma sheath. Random time slots cause the receiver unable to receive information in the form of a complete frame, resulting in the traditional communication methods being no longer applicable. In order to receive the complete frame in random time slots and maximize the use of temporal resources of the plasma sheath channel, this article constructs a temporal-varying plasma sheath channel, proposes a soft-decision decoding algorithm for short-frame fountain codes (SFFCs), studies the relationship between the encode parameters and the characteristics of the channel, and designs communication experiments based on inductively coupling plasma (ICP). The short-frame fountain code (SFFC) has the characteristics of no-rate and short-frame, which can adapt to the short-time and random of the plasma sheath. In addition, soft-decision decoding algorithm can effectively reduce misjudgment of the receiver, reduce packet error rate, and improve the utilization of limited temporal resources of the plasma sheath channel. Simulation and experiments show that the proposed method achieves higher utilization of temporal resources of plasma sheath channel, and improves the reliability of communication. Even if the plasma equivalent frequency is higher than the carrier frequency, the uninterrupted and correct transmission of information can be realized.