• Journal of Internet of Things and Convergence
• /
• v.10 no.4
• /
• pp.1-8
• /
• 2024

As technology advances, Internet of Things (IoT) technology is rapidly evolving as well. Various protocols, including Message Queuing Telemetry Transport (MQTT), are being used in IoT technology. MQTT, a lightweight messaging protocol, is considered a de-facto standard in the IoT field due to its efficiency in transmitting data even in environments with limited bandwidth and power. In this paper, we propose a method to improve the message transmission method in MQTT 5.0, specifically focusing on the shared subscription feature. The widely used round-robin method in shared subscriptions has the drawback of not considering the current state of the clients. To address this limitation, we propose a method to select the optimal transmission method by considering the current state. We model this problem based on Markov decision process (MDP) and utilize Q-Learning to select the optimal transmission method. Through simulation results, we compare our proposed method with existing methods in various environments and conduct performance analysis. We confirm that our proposed method outperforms existing methods in terms of performance and conclude by suggesting future research directions.

• The KIPS Transactions:PartD
• /
• v.12D no.5 s.101
• /
• pp.797-806
• /
• 2005

The objective of the In-h(High Level Architecture) have recommended by DoD(Department of Defense) is to facilitate interoperability among simulations and to promote reuse of their components. There are many legacy simulation softwares developed before the HLA becomes simulation standard. The integration of legacy simulations into federations using the HLA is an important research topic in M&S(Modeling and Simulation) area. Legacy simulation softwares of the mission critical industry such as nuclear and aerospace are generally use Fortran language. However, the reuse of those is not easy because the HLA is not support Fortran language. This paper suggests a integration method which minimizes the modification of legacy simulation software and migrates the legacy simulation software to HLA federation. Each federate participating in federation have the separated executables that communicate via a shared memory created at run-time. Two types of shared memory blocks are used for publication and subscription. Declaration block for global variables used in legacy simulation software is separated for publication and subscription and then mapped as classes of objects and interactions for the HLA FOM design. To validate the suggested method, we approached the HLA integration of legacy nuclear simulation code being used in plant design and to observe the integration results, we used the FMT(Federation Management Tool). The diagnostic information which the FTM displays showed that our method can be successfully and effectively used for a HLA federation.

• Journal of Korean Library and Information Science Society
• /
• v.49 no.3
• /
• pp.283-305
• /
• 2018

Although academic library budgets have been decreasing, the rates of print and electronic journal subscription price have consistently increased. In response to this, as part of efforts to ensure access to foreign academic materials, the Ministry of Education and Korea Education & Research Information Service (KERIS) have initiated and operated Foreign Research Information Center (FRIC) since 2006, pursuing shared acquisition and sharing of foreign print journals. This study investigates the roles/values, issues raised by stakeholders, improvements in services, and new service elements of FRIC through the in-depth interviews with librarians in charge of FRIC in addition to examining its current state. The findings show that FRIC has contributed to sharing of academic materials and to promoting research. However, it was also found that the five types of stakeholders (i.e., the Ministry of Education/KERIS, universities/libraries, users, FRICs, and publishers/agencies) have diverse issues and problems with FRIC. Therefore, this study makes some suggestions to address the issues in terms of policy, system, management, and service.