CARTS: Cooperative and Adaptive Resource Triggering and Stitching for 5G ISAC

2025-07-18

AI Summary

In 5G integrated sensing and communication (ISAC) systems, asynchronous and non-uniform channel state information (CSI) measurements from demodulation reference signals (DMRS) and sounding reference signals (SRS) hinder effective CSI fusion, limit update frequency, and constrain sensing coverage. To address these challenges, this paper proposes CARTS—a novel uplink-oriented adaptive CSI fusion framework. Its key contributions are: (1) a channel stitching compensation mechanism that enables precise alignment and interpolation of heterogeneous, asynchronous CSI streams; and (2) a real-time SRS triggering algorithm for on-demand, low-overhead sensing resource allocation. CARTS is fully compliant with 3GPP Release 16/17 standards and requires no additional spectrum. Experimental results demonstrate that, under doubled user equipment (UE) density, CARTS reduces channel estimation error to 0.167 and achieves UE localization accuracy of 85 cm—substantially outperforming periodic SRS-based baselines. The framework significantly enhances sensing continuity and system scalability.

Technology Category

• Intelligent Robots: Multimodal Perception & Sensor Fusion
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Location- and context-aware Web and WoT applications and services
• Security and Privacy: Large-scale security measurements
• Search and Retrieval-Augmented AI: Personalized, context-aware and across-device search

Abstract

This paper presents CARTS, an adaptive 5G uplink sensing scheme designed to provide Integrated Sensing and Communication (ISAC) services. The performance of both communication and sensing fundamentally depends on the availability of accurate and up-to-date channel state information (CSI). In modern 5G networks, uplink CSI is derived from two reference signals: the demodulation reference signal (DMRS) and the sounding reference signal (SRS). However, current base station implementations treat these CSI measurements as separate information streams. The key innovation of CARTS is to fuse these two CSI streams, thereby increasing the frequency of CSI updates and extending sensing opportunities to more users. CARTS addresses two key challenges: (i) a novel channel stitching and compensation method that integrates asynchronous CSI estimates from DMRS and SRS, despite their different time and frequency allocations, and (ii) a real-time SRS triggering algorithm that complements the inherently uncontrollable DMRS schedule, ensuring sufficient and non-redundant sensing opportunities for all users. Our trace-driven evaluation shows that CARTS significantly improves scalability, achieving a channel estimation error (NMSE) of 0.167 and UE tracking accuracy of 85 cm while supporting twice the number of users as a periodic SRS-only baseline with similar performance. By opportunistically combining DMRS and SRS, CARTS therefore provides a practical, standard-compliant solution to improve CSI availability for ISAC without requiring additional radio resources.

Problem

• Fusing DMRS and SRS CSI streams for better ISAC performance
• Integrating asynchronous CSI estimates from different signal types
• Ensuring sufficient sensing opportunities without extra radio resources

Innovation

• Fuses DMRS and SRS CSI streams
• Novel channel stitching and compensation method
• Real-time SRS triggering algorithm