  We propose a novel formulation of the "effectiveness problem" in
communications, put forth by Shannon and Weaver in their seminal work [2], by
considering multiple agents communicating over a noisy channel in order to
achieve better coordination and cooperation in a multi-agent reinforcement
learning (MARL) framework. Specifically, we consider a multi-agent partially
observable Markov decision process (MA-POMDP), in which the agents, in addition
to interacting with the environment can also communicate with each other over a
noisy communication channel. The noisy communication channel is considered
explicitly as part of the dynamics of the environment and the message each
agent sends is part of the action that the agent can take. As a result, the
agents learn not only to collaborate with each other but also to communicate
"effectively" over a noisy channel. This framework generalizes both the
traditional communication problem, where the main goal is to convey a message
reliably over a noisy channel, and the "learning to communicate" framework that
has received recent attention in the MARL literature, where the underlying
communication channels are assumed to be error-free. We show via examples that
the joint policy learned using the proposed framework is superior to that where
the communication is considered separately from the underlying MA-POMDP. This
is a very powerful framework, which has many real world applications, from
autonomous vehicle planning to drone swarm control, and opens up the rich
toolbox of deep reinforcement learning for the design of multi-user
communication systems.
