Dual-frequency multi-constellation (DFMC) satellite-based augmentation system (SBAS) is a new SBAS standard for aeronautical navigation systems. It supports aircraft navigation from the enroute to approach phases via the L1 and L5 frequencies (1575.42 and 1176.45 MHz). Although the ionosphere-free (IF) combination in the DFMC SBAS operation removes the first-order ionospheric delays in the pseudorange measurement, remaining terms including the satellite-clock offset errors and higher-order ionospheric (HOI) delays are still unaccounted for. The DFMC SBAS accuracy and integrity can be affected by the HOI effects, especially during severe ionospheric disturbances. In this work, we present the local DFMC SBAS corrections with and without the mitigation of HOI delays. We first estimate the HOI delay terms using the received pseudorange followed by separate satellite and receiver bias estimations based on the minimum sum-variance technique. The integrity terms can then be obtained. The performances of DFMC SBAS using the global navigation satellite system (GNSS) data including GPS, Galileo, and QZSS are evaluated using obtained GNSS data at stations in Thailand on the ionospheric quiet and disturbed days. The results show that with the HOI mitigation, the vertical positioning errors (VPE) on the quiet and disturbed days can be improved by 12% and 9%, whereas the vertical protection levels (VPL) are improved by 16% and 21%, respectively. In addition, we perform a preliminary assessment of DFMC SBAS based on the International Civil Aviation Organization (ICAO) requirements of two categories: Localizer Performance with Vertical guidance (LPV-200) and Category I precision approach (CAT-I) showing promising results.

双频多星座（DFMC）星基增强系统（SBAS）是航空导航系统的新SBAS标准。它通过 L1 和 L5 频率（1575.42 和 1176.45 MHz）支持飞机从航路到进近阶段的导航。尽管 DFMC SBAS 操作中的无电离层 (IF) 组合消除了伪距测量中的一阶电离层延迟，但包括卫星时钟偏移误差和高阶电离层 (HOI) 延迟在内的剩余项仍然未被考虑。DFMC SBAS 的准确性和完整性可能会受到 HOI 效应的影响，特别是在严重的电离层扰动期间。在这项工作中，我们提出了在减轻和不减轻 HOI 延迟的情况下的本地 DFMC SBAS 校正。我们首先使用接收到的伪距估计 HOI 延迟项，然后基于最小和方差技术分别估计卫星和接收机偏差。然后可以获得完整性条款。使用包括 GPS、Galileo 和 QZSS 在内的全球导航卫星系统 (GNSS) 数据的 DFMC SBAS 的性能是使用在电离层安静和扰动的日子在泰国站获得的 GNSS 数据进行评估的。结果表明，通过HOI缓解，安静天和受干扰天的垂直定位误差（VPE）可分别改善12％和9％，而垂直保护水平（VPL）分别改善16％和21％ 。此外，我们根据国际民用航空组织 (ICAO) 的两个类别要求对 DFMC SBAS 进行了初步评估：垂直引导定位器性能 (LPV-200) 和 I 类精密进场 (CAT-I)，显示出良好的结果。