Age of Information Analysis for NOMA-Assisted Grant-Free Transmissions with Randomly Arrived Packets

2025-04-28

AI Summary

Excessive Age of Information (AoI) in uplink status update systems degrades timeliness-critical communication performance. Method: This paper proposes a NOMA-assisted grant-free transmission scheme, departing from the idealized generate-at-will (GAW) model by introducing a general stochastic packet generation model to capture random status update arrivals. It establishes rigorous analytical frameworks—both with and without retransmission—for NOMA-based grant-free access, quantitatively characterizing the impact of transmission success probability on AoI. Contribution/Results: Theoretical analysis and simulations demonstrate that the proposed NOMA scheme significantly reduces AoI compared to orthogonal multiple access (OMA). Moreover, retransmission yields substantial AoI gains under low update rates or high user density. This work provides a novel stochastic modeling framework and design paradigm for AoI-aware non-orthogonal random access.

Technology Category

• Planning, Routing, and Scheduling: Optimization of Spatio-temporal Systems
• Multiagent Systems: Agent Communication
• Reasoning under Uncertainty: Stochastic Optimization

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Web performance, measurement, and characterization
• Security and Privacy: Large-scale security measurements
• Social Networks and Social Media: Generative AI / large language models and their impact on social systems

Abstract

This paper investigates the application of non-orthogonal multiple access (NOMA) to grant-free transmissions to reduce the age of information (AoI) in uplink status update systems, where multiple sources upload their {status updates} to {a common} receiver. Unlike existing studies which {adopted} the idealized generate-at-will (GAW) model, {i.e., a status} update data can be generated and transmitted at any time, this paper utilizes a more practical model {to characterize} the inherent randomness of the generation of the status updating data packets. A rigorous analytical framework is established to precisely evaluate the average AoI achieved by the NOMA-assisted grant-free schemes for both {the} cases with and without retransmission. The impact of the choice of the probability {of transmission} on the average AoI is investigated. Extensive simulation results are provided to validate the accuracy of the developed analysis. It is shown that NOMA-assisted schemes are more superior in reducing AoI{, compared} to orthogonal multiple access (OMA) based schemes. In addition, compared to schemes without retransmission, the AoI performance {of} the schemes with retransmission can {be improved} significantly when the status update generation rate is low or the user density is relatively high.

Problem

• Reducing Age of Information in NOMA grant-free uplink systems
• Analyzing AoI with practical random packet generation model
• Comparing NOMA and OMA schemes for AoI performance

Innovation

• NOMA-assisted grant-free uplink transmissions
• Practical model for random packet generation
• Analytical framework for AoI evaluation