Grant-free Radio Access IoT Networks: Scalability Analysis in Coexistence Scenarios

TL;DR

This paper analyzes the impact of coexisting radio access technologies in IoT networks, deriving formulas for performance metrics and validating them through simulations to understand how coexistence affects success probability, battery life, and delay.

Contribution

It introduces an analytical model for coexistence scenarios in grant-free IoT networks, accounting for multiple technologies sharing resources, and explores mitigation strategies like densification and joint reception.

Findings

Coexistence can significantly degrade success probability and battery lifetime.

Densification and joint reception can mitigate performance degradation.

The analytical model aligns well with simulation results.

Abstract

IoT networks with grant-free radio access, like SigFox and LoRa, offer low-cost durable communications over unlicensed band. These networks are becoming more and more popular due to the ever-increasing need for ultra durable, in terms of battery lifetime, IoT networks. Most studies evaluate the system performance assuming single radio access technology deployment. In this paper, we study the impact of coexisting competing radio access technologies on the system performance. Considering $\mathpzc K$ technologies, defined by time and frequency activity factors, bandwidth, and power, which share a set of radio resources, we derive closed-form expressions for the successful transmission probability, expected battery lifetime, and experienced delay as a function of distance to the serving access point. Our analytical model, which is validated by simulation results, provides a tool to evaluate the coexistence scenarios and analyze how introduction of a new coexisting technology may degrade the system performance in terms of success probability and battery lifetime. We further investigate solutions in which this destructive effect could be compensated, e.g., by densifying the network to a certain extent and utilizing joint reception.