Phase-continuous multi-BS signal aggregation for range estimation in ISAC systems
Yi Geng · ITU Journal on Future and Evolving Technologies · 2025
Achieving high-precision ranging in Integrated Sensing and Communications (ISAC) systems operating in low-frequency bands is challenging due to fragmented frequency resources and clock synchronization errors across multiple operators. Cross-operator Carrier Aggregation (CA) offers a potential solution by combining fragmented frequency resources, but clock synchronization errors between Base Stations (BSs) cause phase discontinuities that severely degrade ranging performance. This paper proposes a novel method for cross-operator CA scenarios that leverages successive echo signals to mitigate these phase discontinuities without requiring perfect clock synchronization between BSs. A comprehensive mathematical analysis of phase discontinuities in multi-BS systems is provided and their impact on range profiles is quantified, revealing a characteristic "fishbone effect" that substantially reduces ranging accuracy. Our proposed method effectively eliminates this effect by progressively matching phase transitions between signals from different BSs. Through extensive simulations in both single-target and multi-target scenarios, the proposed method achieves similar range accuracy comparable to systems under perfect synchronization conditions, offering a viable solution for applications requiring accurate positioning in resource-constrained environments.