Eeects of Periodic Communication on Distributed Decision-making

A set of performance scenarios as a function of periodic communication is hypothesized and leads to an analysis of optimal communication rates. In general, we expect that performance over time follows certain patterns with respect to the reception of messages regarding global state. To explore the hypothesis, we present a model of distributed game automata which make decisions probabilistically concerning group, or coalition, formation. The uncertainty in the players' coalition strategies can be reduced by increasing communication but at the expense of more overhead. In a job scheduling application , the players make good decisions concerning group formation only if there is suucient communication. The results agree with the hypothesized trade-oo of decision quality versus communication overhead. I. Introduction Our interest is in the fundamental uncertainty in distributed systems 1] as innuenced by the common-knowledge problem 2] in which a decision-maker (DM) cannot know the level of knowledge obtained by others. Frequent communication decreases the uncertainty in global state but has a cost which can adversely aaect performance 3]. This trade-oo suggests that an optimal period of communication balances the two tendencies. In general, we expect that performance over time follows certain patterns with respect to the reception of messages regarding the global system state. The reception of a message provides a \fresh" update of the system state and we would expect that performance will be good for the near future. However, as this information becomes \stale", we would expect the performance to degrade. The rate at which performance degrades will depend on the application and on the particular environment. Our particular objective is to improve performance by understanding and addressing this communication problem in distributed decision-making; this is relevant to coordination 4] which is informally deened as \the activity of independent agents making harmonious, non-connicting decisions". We hypothesize that given periodic communication, the shape of the curve deening performance degradation over time will exhibit a certain characteristic geometric pattern. For particular simple geometric patterns, we examine the optimal communication period that balances the communication overhead with the beneets derived from good views of the global state. Our paper outlines these diierent general patterns and argues for their reasonableness.