Timing-Aware Satellite Association for Multi-LEO Direct-to-Handset Communications

TL;DR

This paper analyzes the received-signal model under the 3rd Generation Partnership Project (3GPP) transmitter structure and proposes a timing-aware satellite association strategy that enables cooperation only with satellites expected to satisfy a UT-side timing tolerance, thereby avoiding dominant asynchronous interference by design.

Abstract

The rapid deployment of large-scale low Earth orbit (LEO) satellite constellations has positioned direct-to-handset (D2H) communications as a key enabler of future non-terrestrial networks. However, the limited link budget of handheld devices makes broadband service delivery challenging, and multi-satellite cooperative transmission is often required to provide sufficient power gain. In practice, such cooperation is severely hindered by asynchronous reception across satellites. This paper analyzes the received-signal model under the 3rd Generation Partnership Project (3GPP) transmitter structure and shows that satellite-dependent propagation delays prevent simultaneous timing alignment for multiple user terminals (UTs). This timing mismatch induces severe inter-carrier interference (ICI) and inter-symbol interference (ISI), even from the intended signals, which fundamentally constrains the achievable cooperative gain. To address this issue, we propose a timing-aware satellite association strategy that enables cooperation only with satellites expected to satisfy a UT-side timing tolerance, thereby avoiding dominant asynchronous interference by design. Simulation results demonstrate that the proposed strategy improves throughput performance compared to single-satellite transmission and fully connected multi-satellite baselines.

Figures (10)

• Figure 1: System model of multi-LEO satellite D2H communication, consisting of $M$ LEO satellites and $K$ UTs. Each satellite and UT is equipped with a UPA.
• Figure 2: MIMO-OFDM transmitter architecture as specified in 3GPP Book_lte.
• Figure 3: Illustration of asynchronous reception at a $k$-th UT, where propagation delay differences among multiple satellites cause sample-level misalignment of the received signals.
• Figure 4: Overall framework of the proposed satellite association strategy.
• Figure 5: Illustration of the attachable region for a target UT. Satellites whose propagation-delay offsets fall within $(L_{\mathrm{CP}}^{\mathrm{add}}+L_{\mathrm{margin}})$ are regarded as attachable, and the UT associates only with satellites in this region.