  This article evaluates the quality-of-service performance and scalability of
the recently released Bluetooth Mesh protocol and provides general guidelines
on its use and configuration. Through extensive simulations, we analyzed the
impact of the configuration of all the different protocol's parameters on the
end-to-end reliability, delay, and scalability. In particular, we focused on
the structure of the packet broadcast process, which takes place in time
intervals known as \textit{Advertising Events} and \textit{Scanning Events}.
Results indicate a high degree of interdependence among all the different
timing parameters involved in both the scanning and the advertising processes
and show that the correct operation of the protocol greatly depends on the
compatibility between their configurations. We also demonstrated that
introducing randomization in these timing parameters, as well as varying the
duration of the \textit{Advertising Events}, reduces the drawbacks of the
flooding propagation mechanism implemented by the protocol. Using data
collected from a real office environment, we also studied the behavior of the
protocol in the presence of WLAN interference. It was shown that Bluetooth Mesh
is vulnerable to external interference, even when implementing the standardized
limitation of using only 3 out of the 40 Bluetooth Low Energy frequency
channels. We observed that the achievable average delay is relatively low, of
around 250~ms for over 10 hops under the worst simulated network conditions.
However, results proved that scalability is especially challenging for
Bluetooth Mesh since it is prone to broadcast storm, hindering the
communication reliability for denser deployments.
