Beacon Success Rate versus Gateway Density in Sub-GHz Sensor Networks

Area of Science:

• Wireless communication networks
• Internet of Things (IoT)
• Network performance analysis

Background:

• Multiple Gateways (GWs) enable Internet of Things (IoT) sensor connectivity in Wide Area Networks (WANs).
• End Nodes (ENs) discover Gateways (GWs) via periodic beacons, enhancing coverage diversity.
• Simultaneous beacon transmissions from nearby GWs cause interference and collisions, impacting network reliability.

Purpose of the Study:

• To analyze the impact of intra-network interference on coexisting Gateways (GWs).
• To determine the maximum number of GWs that can coexist in an IoT WAN.
• To develop a novel collision model considering Medium Access Control (MAC) and Physical (PHY) layer effects.

Main Methods:

• Development of a new collision model incorporating partial overlap durations and relative power of colliding events.
• Analysis of the relationship between collisions and packet loss rates.
• Performance evaluation using analytical methods (for validation) and simulation methods based on field measurement data.

Main Results:

• The study quantifies the impact of interference on GW coexistence and packet loss.
• Numerical results using Gaussian Frequency Shift Keying (GFSK) modulation are presented.
• Larger beacon intervals and frequency hopping reduce beacon loss but increase acquisition latency.
• Increased GW density reduces gateway discovery latency due to abundant beacons.

Conclusions:

• The findings provide guidance for selecting GFSK modulation parameters for low bit-rate, narrow-bandwidth IoT applications.
• Optimizing beacon intervals and employing frequency hopping are crucial for managing beacon loss and latency trade-offs.
• Understanding GW density effects is key to efficient gateway discovery in IoT WANs.