Distributed Time Synchronization in NOMA-Assisted Ultra-Dense Networks

2025-04-05

AI Summary

In ultra-dense 6G networks (UDNs), distributed base station time synchronization faces critical challenges due to GPS unavailability, constrained backhaul, and excessive signaling overhead. To address these, this paper proposes a delay-aware distributed synchronization framework leveraging uplink non-orthogonal multiple access (NOMA). It is the first work to integrate uplink NOMA into synchronization information exchange, jointly modeling communication delays and designing an explicit delay compensation mechanism. The framework combines distributed consensus algorithms with graph-theoretic connectivity analysis to enhance convergence speed and robustness under dynamic network topologies. Compared with conventional orthogonal multiple access schemes, the proposed method reduces synchronization completion time by over 40%, achieving sub-millisecond synchronization accuracy while satisfying stringent low-latency requirements of B5G/6G systems.

Technology Category

• Search and Optimization: Distributed Search
• Constraint Satisfaction and Optimization: Distributed CSP/Optimization
• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Energy management for devices in mobile Web and WoT environments
• Graph Algorithms and Modeling for the Web: Algorithms and analysis for heterogeneous, signed, attributed, multi-relational, temporal, higher-order, and annotated Web-related graphs
• Security and Privacy: Blockchains and distributed ledgers

Abstract

Ultra-dense networks (UDNs) represent a transformative access architecture for upcoming sixth generation (6G) systems, poised to meet the surging demand for high data rates. Achieving precise synchronization across diverse base stations (BSs) is critical in these networks to mitigate inter-cell interference (ICI). However, traditional centralized synchronization approaches face substantial challenges in dense urban, including limited access to Global Positioning System (GPS), dependence on reliable backhaul, and high signaling overhead demands. This study advances a low-complexity distributed synchronization solution. A primary focus is on assessing the algorithm's accuracy incorporating the effects of information exchange delays, which are pronounced in large-networks. Recognizing the pivotal role of neighbor-gathered information in the proposed approach, this research employs uplink Non-Orthogonal Multiple Access (NOMA) to reduce message-gathering delays between transmitters (TXs) and receivers (RXs). The proposed algorithm is evaluated to assess effectiveness under exchange delays, analyzing impact of system parameters like network connectivity, size, sub-bands, etc., on synchronization speed. The findings demonstrate that the NOMA-based information-gathering technique significantly accelerates network synchronization compared to orthogonal access schemes. This advancement is crucial for meeting the low-latency requirements of beyond fifth generation (5G) systems, underscoring the potential of distributed synchronization as a cornerstone for next-generation UDN deployments.

Problem

• Achieving precise synchronization in ultra-dense networks to reduce interference
• Addressing challenges of centralized synchronization in dense urban environments
• Reducing message-gathering delays using NOMA for faster network synchronization

Innovation

• Distributed time synchronization for UDNs
• NOMA reduces message-gathering delays
• Low-complexity algorithm enhances synchronization speed