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초록

With the rapid increase of Internet of Things (IoT) devices, an efficient communication protocol is needed to effectively manage the exchange and generation of data from these devices. Message Queuing Telemetry Transport (MQTT) is widely adopted in IoT systems due to its lightweight design and the support for topic-based publish-subscribe architectures. In MQTT, multiple IoT devices are connected to a server, referred to as a broker, to facilitate efficient data transmission and reduce network overhead. However, the traditional single-broker system is unable to efficiently support the massive number of IoT devices. Although a multi-broker system is proposed as a solution, the use of the flooding method for updating topics has generated a significant amount of inter-broker traffic, causing severe congestion in the brokers. As a result, this will lead to long topic update delay. To resolve this issue, in this paper, we propose a topic update dissemination scheme by considering the congestion in brokers. We formulate the topic update dissemination problem using the Lyapunov function, to minimize the topic update delay in the multi-broker system. To solve the problem, we propose a heuristic algorithm for the update dissemination forwarding decision. The simulation results show that the proposed algorithm can effectively reduce the topic update delay compared to other existing algorithms.