In this paper, we propose a new multiple access protocol for the ubiquitous network and analyze its performance in the nonsaturated condition. Based on the concept of equilibrium analysis, we analyze its throughput and the contention window size that maximizes its throughput by constructing a Markov model of terminal state. From this work we introduce an index that uniquely decides throughput regardless of the number of terminals or the offered traffic and propose a contention window adjustment algorithm based on the index. Computer simulations that compare the proposed protocol to conventional protocols clarify that the former has superior throughput.