Using Age of Information for Throughput Optimal Spectrum Sharing

2025-09-22

AI Summary

This paper addresses spectrum access in an N-channel cognitive radio network where primary users (PUs) and secondary users (SUs) share spectrum, with PU occupancy modeled as a Markov chain. The SU must maximize its throughput while minimizing interference to PUs—subject to strict PU priority guarantees. To this end, we innovatively incorporate Age of Information (AoI) into spectrum sensing decisions and propose a Whittle index-based dynamic scheduling policy. We first establish threshold optimality and indexability for the single-channel case; then extend the framework to multi-channel settings with inter-channel state dependencies and unknown transition probabilities, integrating reinforcement learning for adaptive index estimation. Simulation results demonstrate that the proposed method significantly improves SU throughput across diverse PU occupancy patterns, while rigorously bounding the PU–SU collision probability within prescribed constraints—thus achieving a favorable trade-off between spectral efficiency and coexistence robustness.

Technology Category

• Planning, Routing, and Scheduling: Scheduling under Uncertainty
• Reasoning under Uncertainty: Stochastic Optimization
• Search and Optimization: Mixed Discrete/Continuous Search

Application Category

• Economics, Online Markets and Human Computation: Incentives in network design for Web infrastructures and ecosystems
• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• User Modeling, Personalization and Recommendation: User privacy protection in personalized systems

Abstract

We consider a spectrum sharing problem where two users attempt to communicate over N channels. The Primary User (PU) has prioritized transmissions and its occupancy on each channel over time can be modeled as a Markov chain. The Secondary User (SU) needs to determine which channels are free at each time-slot and attempt opportunistic transmissions. The goal of the SU is to maximize its own throughput, while simultaneously minimizing collisions with the PU, and satisfying spectrum access constraints. To solve this problem, we first decouple the multiple-channel problem into N single-channel problems. For each decoupled problem, we prove that there exists an optimal threshold policy that depends on the last observed PU occupancy and the freshness of this occupancy information. Second, we establish the indexability of the decoupled problems by analyzing the structure of the optimal threshold policy. Using this structure, we derive a Whittle index-based scheduling policy that allocates SU transmissions using the Age of Information (AoI) of accessed channels. We also extend our insights to PU occupancy models that are correlated across channels and incorporate learning of unknown Markov transition matrices into our policies. Finally, we provide detailed numerical simulations that demonstrate the performance gains of our approach.

Problem

• Optimizing secondary user throughput while minimizing primary user collisions
• Designing spectrum access policies using Age of Information metrics
• Developing Whittle index-based scheduling for opportunistic channel access

Innovation

• Decouples multi-channel problem into single-channel subproblems
• Proves optimal threshold policy using Age of Information
• Derives Whittle index-based scheduling policy