Uplink access schemes reduce delay and energy in ambient IoT devices
System-Level Evaluation of Uplink Access Schemes for Ambient IoT
Networking and Internet Architecture
Summary
Ambient IoT devices often run on tiny amounts of harvested energy, making sending data tricky and energy costly. The authors study different ways these devices can send data to reduce delay and energy use. They compare the standard method to others that keep some connection info or mix reserved and random access. Their new hybrid approach reduces delay by up to 69%, and another method cuts energy use by up to 24%, improving how these tiny devices communicate.
What this means in practice
- •For iot system integrators: Optimize uplink data transmission in energy-constrained ambient IoT deployments to improve battery life and reduce communication delays.
- •For network infrastructure engineers: Configure and evaluate uplink access protocols in NB-IoT networks to support dense ambient IoT device populations with low energy consumption.
Authors
Douglas Dziedzorm Agbeve, Henrique Duarte Moura, Andrey Belogaev, Jeroen Famaey
Abstract
Ambient Internet of Things (A-IoT) devices operate under stringent energy constraints, relying on harvested power in the $μ$W-to-mW range and limited energy storage. The A-IoT air interface for active devices is still under development; we therefore use Narrowband Internet of Things (NB-IoT) as an implementable reference for evaluating autonomous Uplink (UL) access under harvested energy. Under these conditions, the standard NB-IoT contention-based Random Access (RA) procedure incurs substantial per-packet overhead, making UL access in dense A-IoT networks increasingly energy-expensive. Context-retaining UL access schemes reduce this overhead, but their energy-latency trade-offs are insufficiently studied in literature under realistic harvesting and protocol constraints. To address this gap, we extend the LENA-NB ns-3 module with solar energy harvesting, supercapacitor storage, and a hysteretic brown-out mechanism, and propose Hybrid Scheduling Request (HSR), a hybrid UL access scheme combining reserved request occasions with opportunistic contention. We compare RA, Scheduling Request (SR), HSR and an Idealized Fast Uplink Grant (FUG) serving as a performance bound. Results show that HSR reduces mean packet delay by up to 69% and SR reduces energy per delivered bit by up to 24%, both relative to RA.