Blind 5G NR LEO Initial Access Receiver

Abstract

LEO satellite links pose severe challenges for 5G Non-Terrestrial Network (NTN) initial access due to large carrier frequency offsets, rapidly varying Doppler, and low SNR, making fully blind operation essential in cold-start scenarios. Using a real 5G NTN LEO over-the-air testbed emulation, we show that Doppler compensation accuracy directly governs user equipment (UE) connection outcomes, with residual errors below 3 kHz required for reliable synchronization and attachment. We then present a fully blind, feedfor ward receiver that computes bounded reliability scores at each processing stage and uses them for hypothesis gating, burst selection, conservative log-likelihood ratio (LLR)-domain combining, weighting, and final lock de cisions. The design includes a conservative, reliability aware multi-Synchronization Signal Block (SSB) Phys ical Broadcast Channel (PBCH) soft-combining stage that only supplements single-SSB channel quality as sessment. Deterministic results from 3GPP-compliant simulations demonstrate robust blind synchronization under ±100kHz frequency offsets and successful PBCH decoding at low signal-to-noise ratios in urban line-of sight (LOS) and non-line-of-sight (NLOS) conditions. The simulation code used is publicly available.