  Decentralized control in multi-robot systems is dependent on accurate and
reliable communication between agents. Important communication factors, such as
latency and packet delivery ratio, are strong functions of the number of agents
in the network. Findings from studies of mobile and high node-count
radio-frequency (RF) mesh networks have only been transferred to the domain of
multi-robot systems to a limited extent, and typical multi-agent robotic
simulators often depend on simple propagation models that do not reflect the
behavior of realistic RF networks. In this paper, we present a new open source
swarm robotics simulator, BotNet, with an embedded standards-compliant
time-synchronized channel hopping (6TiSCH) RF mesh network simulator. Using
this simulator we show how more accurate communications models can limit even
simple multi-robot control tasks such as flocking and formation control, with
agent counts ranging from 10 up to 2500 agents. The experimental results are
used to motivate changes to the inter-robot communication propagation models
and other networking components currently used in practice in order to bridge
the sim-to-real gap.
