[Paper Review] Are Multiagent Systems Resilient to Communication Failures?

Philip N. Brown, Holly Borowski+1 more|arXiv (Cornell University)|Oct 23, 2017

Game Theory and Applications18 references3 citations

TL;DR

This paper investigates whether multiagent systems remain resilient to communication failures in game-theoretic control frameworks. It shows that even a single agent losing communication with one other agent can lead to arbitrarily poor system outcomes under standard learning rules, but identifies conditions—particularly when proxy payoffs are aligned with the potential function—under which resilience can be preserved through structured design of local utility functions.

ABSTRACT

A challenge in multiagent control systems is to ensure that they are appropriately resilient to communication failures between the various agents. In many common game-theoretic formulations of these types of systems, it is implicitly assumed that all agents have access to as much information about other agents' actions as needed. This paper endeavors to augment these game-theoretic methods with policies that would allow agents to react on-the-fly to losses of this information. Unfortunately, we show that even if a single agent loses communication with one other weakly-coupled agent, this can cause arbitrarily-bad system states to emerge as various solution concepts of an associated game, regardless of how the agent accounts for the communication failure and regardless of how weakly coupled the agents are. Nonetheless, we show that the harm that communication failures can cause is limited by the structure of the problem; when agents' action spaces are richer, problems are more susceptible to these types of pathologies. Finally, we undertake an initial study into how a system designer might prevent these pathologies, and explore a few limited settings in which communication failures cannot cause harm.

Motivation & Objective

• To investigate whether game-theoretic multiagent systems remain resilient when agents lose communication with one another.
• To examine the impact of communication failures on solution concepts like Nash equilibria in distributed control systems.
• To determine whether agents can be endowed with online-reactive policies that maintain system performance despite missing information.
• To identify structural conditions under which communication failures do not compromise system behavior.

Proposed method

• The authors model the system as a potential game with a unique pure Nash equilibrium and analyze how communication loss affects best-response dynamics.
• They introduce a reduced potential function $\tilde{W}$ that maximizes over the actions of the lost-communication agent, serving as a proxy for the true potential function.
• Proxy utility functions $\tilde{U}_1$ are designed to align with $\tilde{W}$, ensuring that best responses still lead toward the global optimum.
• A certificate is proposed: if a player's proxy utility function maximizes over actions consistent with the reduced potential, then the reduced game remains weakly-acyclic under best replies.
• The analysis focuses on memoryless learning rules, particularly asynchronous best-response dynamics, to evaluate convergence properties.
• Theoretical results are derived using game-theoretic concepts such as best-reply paths, potential functions, and Nash equilibrium uniqueness.

Experimental results

Research questions

• RQ1 Can a multiagent system with a unique pure Nash equilibrium remain resilient to communication failures between agents?
• RQ2 Under what conditions can agents compute proxy payoffs that preserve convergence to the optimal equilibrium when communication is lost?
• RQ3 Does the structure of the potential function allow for safe proxy payoff design that prevents pathological outcomes?
• RQ4 How does the loss of information about a single agent’s action affect the convergence of learning algorithms in potential games?
• RQ5 Can memoryless learning rules still ensure system-wide efficiency when agents lack full information about others?

Key findings

• Even a single agent losing communication with one other agent can cause arbitrarily poor outcomes in standard game-theoretic learning rules, regardless of coupling strength.
• Communication failures can lead to convergence to suboptimal equilibria due to misaligned proxy payoffs when agents lack information about others’ actions.
• When proxy payoffs are aligned with the reduced potential function $\tilde{W}$, the system remains weakly-acyclic under best replies and converges to the unique Nash equilibrium.
• A sufficient condition for resilience is that the proxy utility function for a player must maximize over actions consistent with the reduced potential function.
• The existence of safe proxy payoffs is guaranteed in potential games with unique pure Nash equilibria, but these may not be computable without access to the global potential function.
• The results suggest that system designers must carefully align local utility functions with the global potential to preserve resilience under information loss.