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

TL;DR

This paper investigates the challenges of timing synchronization in multi-LEO satellite communications for direct-to-handset links and proposes a timing-aware satellite association strategy to enhance throughput.

Contribution

It introduces a novel timing-aware satellite association method that accounts for propagation delays, improving cooperative transmission performance in LEO satellite networks.

Findings

The proposed strategy significantly improves throughput over single-satellite transmission.

Timing mismatch causes severe interference, limiting cooperative gains.

Simulation results validate the effectiveness of the timing-aware association approach.

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.