A High-Sensitivity Reception for Space-Based ADS-B Signals Based on the Expectation Maximization Algorithm

Space-based Automatic Dependent Surveillance-Broadcast (ADS-B) can provide seamless real-time surveillance service for global aircraft due to its global coverage characteristic compared with terrestrial ADS-B systems. However, the low signal-to-noise ratio (SNR) caused by long transmission distance degrades the continuity in the required surveillance performance (RSP). To ensure surveillance continuity, this paper proposes a coherent reception method based on the expectation maximization (EM) algorithm, realizing high-sensitivity reception for space-based ADS-B signals with low SNR. The reception requirements and the SNR threshold when using the coherent method are first analyzed. An EM model is then established to estimate ADS-B signals’ carrier frequency offset (CFO) and carrier phase offset (CPO) accurately. Simulation experiments and in-orbit test results show that the reception sensitivity metric of space-based ADS-B receivers can be effectively heightened through the proposed method, which can reach -102 dBm at 90% correct decoding probability. Overall, the proposed coherent reception method is superior to the traditional non-coherent methods, improving the reception performance of the space-based ADS-B system for air traffic control.