  In order to achieve the full potential of the Internet-of-Things,
connectivity between devices should be ubiquitous and efficient. Wireless mesh
networks are a critical component to achieve this ubiquitous connectivity for a
wide range of services, and are composed of terminal devices (i.e., nodes),
such as sensors of various types, and wall powered gateway devices, which
provide further internet connectivity (e..g, via WiFi). When considering large
indoor areas, such as hospitals or industrial scenarios, the mesh must cover a
large area, which introduces concerns regarding range and the number of
gateways needed and respective wall cabling infrastructure. Solutions for mesh
networks implemented over different wireless protocols exist, like the recent
Bluetooth Low Energy (BLE) 5.1. Besides range concerns, choosing which nodes
forward data through the mesh has a large impact on performance and power
consumption. We address the area coverage issue via a battery powered BLE relay
device of our own design, which acts as a range extender by forwarding packets
from end nodes to gateways. We present the relay's design and experimentally
determine the packet forwarding efficiency for several scenarios and
configurations. In the best case, up to 35% of the packets transmitted by 11
nodes can be forwarded to a gateway by a single relay under continuous
operation. A battery lifetime of 1 year can be achieved with a relay duty cycle
of 20%.
