Channel Access Methods for RF-Powered IoT Networks: A Survey

TL;DR

This survey addresses the challenge of channel access in RF-powered IoT networks with dedicated energy sources, compiling and classifying MAC approaches into contention-based and contention-free families, including Aloha, CSMA/CA, polling, dynamic TDMA, and NOMA with SIC. It examines three core dimensions: network architectures for energy delivery and data collection, time-slot structures that balance charging with transmission, and the trade-offs between uplink and downlink performance under energy and channel constraints. The authors provide a qualitative comparison across methods, discuss key metrics such as sum-rate and AoI, and highlight gaps such as imperfect CSI, energy availability signaling, and scalability to large networks, while outlining promising directions like IRS, GNNs, and multi-agent reinforcement learning. Overall, the work offers a comprehensive foundation for researchers and practitioners to design efficient, energy-aware MAC protocols in RF-energy harvesting IoT deployments with dedicated power sources.

Abstract

Many Internet of Things (IoT) networks with Radio Frequency (RF) powered devices operate over a shared medium. They thus require a channel access protocol. Unlike conventional networks where devices have unlimited energy, in an RF-powered IoT network, devices must first harvest RF energy in order to transmit or/and receive data. To this end, this survey presents the {\em first} comprehensive review of prior works that employ contention-based and contention-free protocols in IoT networks with one or more {\em dedicated} energy sources. Specifically, these protocols work in conjunction with RF-energy sources to deliver energy delivery or/and data. In this respect, this survey covers protocols based on Aloha, Carrier Sense Multiple Access (CSMA), polling, and dynamic Time Division Multiple Access (TDMA). Further, it covers successive interference cancellation protocols. It highlights key issues and challenges addressed by prior works, and provides a qualitative comparison of these works. Lastly, it identifies gaps in the literature and presents a list of future research directions.

Figures (12)

• Figure 1: Six main elements of IoT. In general, sensor devices gather data, which may process data locally or offload it to a gateway. Processed data is then provided to end users.
• Figure 2: An example IoT network with RF powered and conventional devices.
• Figure 3: Typical IoT networks: (a) an HAP charges device(s). Devices then use their harvested energy and reply to the HAP using a channel access method, (b) devices are charged by one or more power beacons. This architecture helps overcome the doubly near-far problem, and (c) some devices are used as relays to help forward data. Further, these relays may harvest energy from ambient or dedicated source(s).
• Figure 4: Wireless powered or RF charging IoT networks, and receiver architectures.
• Figure 5: Energy conversion efficiency of the P2110B RF power harvester powercast.