• The KIPS Transactions:PartA
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• v.9A no.1
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• pp.19-28
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• 2002

A new class of applications based on event interactions are emerging for the wide-area network such as Internet, which is characterized as loose coupling, heterogeneity. and asynchrony. Content-barred publish/subscribe systems are widely being studied to implement the extent notification service for wide-area networks. In this paper, we analyze some problems of the content-based routing algorithm in SIENA, a recently developed as a representative event notification service architecture, and develop an enhanced routing algorithm.

• Journal of KIISE
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• v.42 no.7
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• pp.939-945
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• 2015

From 2009, the market of smart devices has been rapidly increasing. These devices provide various services to users. The cloud messaging service, especially, is applied to many various services, and sends messages asynchronously. In the cloud messaging service, there are two methods for message transmission, message transmission based on an IP address and a publish/subscribe technique. Each technique uses basic messages in order to send messages to mobile devices. In this paper, the hybrid message transmission, based on user-customized analysis to reduce basic messages, is proposed. The hybrid message transmission uses Exponential Moving Average (EMA) and K-means algorithms for user-customized analysis, and determines the message transmission techniques in each timeslot.

• Journal of Korea Multimedia Society
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• v.22 no.8
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• pp.913-922
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• 2019

The Internet of Things (IoT) envisions smart objects collecting and sharing data at a massive scale via the Internet. One challenging issue is how to disseminate data to relevant data consuming objects efficiently. In such a massive IoT network, Mission critical data dissemination imposes constraints on the message transfer delay between objects. Due to the low power and communication range of IoT objects, data is relayed over multi-hops before arriving at the destination. In this paper, we propose a quorum-based adaptive dissemination algorithm (QADA) for the critical data in the monitoring-based applications of massive IoTs. To design QADA, we first design a new stepped-triangular grid structures (sT-grid) that support data dissemination, then construct a triangular grid overlay in the fog layer on the lower IoT layer and propose the data dissemination algorithm of the publish/subscribe model that adaptively uses triangle grid (T-grid) and sT-grid quorums depending on the mission critical in the overlay constructed to disseminate the critical data, and evaluate its performance as an analytical model.

• KNOM Review
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• v.22 no.1
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• pp.30-41
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• 2019

MQTT protocol is one of open Publish / Subscribe systems for IoT information transmission. In this paper, we are proposing an algorithm to assign a subscriber, which dynamically participate in MQTT clustering system, to an appropriate broker. In MQTT systems with a centralized broker, there are losses of connectivity and messages between subscribers and brokers. In this paper, we addressed this issue for developing scalable open IoT systems and consider clustering MQTT brokers on the SDN infrastructure. In particular, this paper focuses on the problem of allocating subscribers to brokers in accordance with sharing brokers' topics to reduce brokers' load and communication cost in SDN based MQTT cluster. The Experimental results show that the proposed algorithm will reduce the load and the cost as compared to existing methods.

• Journal of the Korea Society for Simulation
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• v.17 no.2
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• pp.21-29
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• 2008

The High Level Architecture(HLA) specifies a framework for interoperation between heterogeneous simulators, and Run-Time Infrastructure(RTI) is a implementation of the HLA Interface Specification. The Data Distribution Management(DDM) services, one category of IEEE 1516 HLA/RTI management services, control filters for data transmission and reception of data volume among simulators. In this paper, we propose design concept of DDM and show its implementation for light-weighted RTI. The design concept of DDM is to minimize total amount of message that each federate and a federation process generate using the rate of RTI service execution. The design of our proposed DDM follows that a data transfer mechanism is differently applied as the rate of RTI service execution. A federate usually publishes or subscribes data when it starts. The federate constantly updates the data and modifies associated regions while it continues to advance its simulation time. Therefore, the proposed DDM design provides fast update or region modification in exchange of complex publish and subscribe services. We describe how to process the proposed DDM in IEEE 1516 HLA/RTI and experiment variable scenarios while modifying region, changing overlap ratio, and increasing data volume.

• Journal of the Korea Society for Simulation
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• v.24 no.4
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• pp.107-118
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• 2015

Many approaches to agent collaboration have been introduced in military war-games, and those approaches address methods for simulation entity (actor) collaboration within a team to achieve given goals. To meet fast-changing battlefield situations, an actor must be loosely coupled with their tasks and be able to take over the role of other actors if necessary to reflect role handovers occurring in real combat. Achieving these requirements allows the transfer of tasks assigned one actor to another actor in circumstances when that actor cannot execute its assigned role, such as when destroyed in action. Tight coupling between an actor and its tasks can prevent role handover in fast-changing situations. Unfortunately, existing approaches and war-game strictly assign tasks to actors during design, therefore they prevent the loose coupling. To overcome these shortcomings, our Role-based Command Hierarchy (ROCH) model dynamically assigns roles to actors based on their situation at runtime. In the model, "Role" separates actors from their tasks. In this paper, we implement the ROCH model as a component that uses a publish-subscribe pattern to handle the link between an actor and the roles of its subordinates (other actors).

• KIPS Transactions on Computer and Communication Systems
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• v.8 no.9
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• pp.209-216
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• 2019

Publish-subscribe communication model is popular for various type of distributed applications because of its loosely coupled style connections. Among the various architecture style for publish-subscribe system, peer-to-peer architecture has been used for the mission critical application domain since it provides high scalability and real-timeness. On the other hand, to utilize the bandwidth of given networks, message filtering is frequently used to reduce the number of messages on the system. Even if P2P provides superior scalability, it is hard to apply filtering to the its messaging system because the filtering process should be done on the peer-side in P2P architecture that are usually done on the broker server in conventional pub/sub architecture. In this paper, we propose a hierarchical subscription management structure as well as message forwarding scheme for efficient data dissemination. Our proposed scheme reduces the number of received messages by filter-out un-wanted messages and offloading the message dissemination work to other subscribers to enhance the messaging throughput.

• Proceedings of the Korean Information Science Society Conference
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• 2002.04a
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• pp.238-240
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• 2002

MoIM(Mobile Message Internet Middleware)-Message 시스템은 이러한 메시지 시스템의 요구사항을 만족하는 메시지 시스템으로서 Point-to-Point 및 Publish-Subscribe 방식을 제공하는 시스템이다. 이 시스템의 통신 방법은 RMI(Remote Method Invocation)을 사용한다. 최근의 인터넷 사용자 수가 급증함에 따라서 메시징 서버를 사용하는 동시 클라이언트의 수도 수천에서 수만으로 이를 것으로 예상되어 대규모의 동시 사용자를 지원하는 연결 기술이 필요하다. 이 논문에서는 이러만 대용량의 데이터를 RMI 통신방법을 사용하여 설계 및 구현한 방법을 기술한다.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.21 no.7
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• pp.1320-1326
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• 2017

Recently, IoT has been studying a lightweight protocol to satisfy device communication in a limited network environment. MQTT is a typical lightweight protocol. It supports small fixed headers to minimize overhead, and adopts publish/subscribe structure to guarantee real-time performance. However, MQTT does not support prioritization of important data and can not provide QoS in a specific IoT service. In this paper, we propose a message processing method to consider the priority of various IoT services in MQTT. In the proposed method, the priority flag is added to the fixed header of the MQTT in the node to transmit the message, and the broker confirms the priority of the corresponding message and processes it preferentially. Through experiment and evaluation, we confirmed the reduction of end-to-end delay between nodes according to priority.

• Journal of KIISE:Databases
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• v.35 no.4
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• pp.368-378
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• 2008

In recent years, publish-subscribe (pub-sub) systems based on XML document filtering have received much attention. In a typical pub-sub system, subscribed users specify their interest in profiles expressed in the XPath language, and each new content is matched against the user profiles so that the content is delivered to only the interested subscribers. As the number of subscribed users and their profiles can grow very large, the scalability of the system is critical to the success of pub-sub services. In this paper, we propose a fast and scalable XML filtering system called SFiST which is an extension of the FiST system. Sharable segments are extracted from twig patterns and stored into the hash-based Segment Table in SFiST system. Segments are used to represent user profiles as Terse Sequences and stored in the Compact Segment Index during filtering. Our experimental study shows that SFiST system has better performance than FiST system in terms of filtering time and memory usage.