Hyeonwoo Kim

Correlation analysis of MQTT loss and delay according to QoS level

MQTT is an open protocol developed and released by IBM. To ensure the reliability of message transmission, MQTT supports three levels of QoS. In this paper, we analyze MQTT message transmission process which consists of real wired/wireless publish client, broker server and Subscribe client. By transmitting messages through 3 levels of QoS with various sizes of payloads, we have captured packets to analyze end-to-end delays and message loss.

Protocol Reverse Engineering to Facebook Messages

In this paper, we will present the results of protocol reverse engineering for Facebook protocol, which includes Facebook message format and its exchange sequences. In order to learn message exchange sequences, we will rely on passive traffic monitoring approach which is based on packet capturing and behavior analysis. And Facebook message formats are deduced from the source program code trace on a test Facebook client that was developed for generating probing messages based on Facebook open Graph API. Deduced Facebook message formats are described in the form of constraint HTTP message specification, and Facebook message exchange sequences are depicted in sequence diagrams with objects of the Facebook client and Facebook servers.

Mobile network configuration for large-scale multimedia delivery on a single WLAN

We report performance measurements and analyses of a variety of wireless networks to arrive at an appropriate network structure configuration for smooth multimedia streaming service with a variety of smart devices in a single wireless network environment. Unlike the usual infrastructure network, configurations such as the IEEE 802.11 ad hoc network and the Wi-Fi direct network use direct connections between devices without going through a wireless AP. Therefore, these configurations prevent concentrating traffic at the wireless AP. We generated three types of wireless network performance measurements and arrived at a suitable network for multimedia streaming service using a variety of smart devices. The wireless network was configured in a structure for efficient multimedia streaming service in a single wireless LAN environment, and subsequently, the network performance was measured.

Efficient method for inferring a firewall policy

We propose a framework which infers the policy of firewall deployed in the Internet access point and computer system. The proposed methodology shows how to infer a firewall policy from restricted probing packets, using consecutive characteristics of the IP address and TCP/UDP port number. We also show the experimental results and the performance of the proposed method.

Development of a gateway system for social network services

In this paper, we propose a method to reduce mobile social network services (SNSs) traffic using a mobile integrated SNS gateway (MISG) to improve network communication performance between the mobile client and SNS servers. The gateway connects the client and SNS servers using the contents adapter and the web service adapter and helps to improve communication performance using its cache engine. An integrated SNS application, the users client, communicates with the gateway server using integrated SNS protocol. In addition, the gateway can alert the client to new SNS contents because of the broker server implemented by the message queuing telemetry transport protocol. We design and develop the modules of the gateway server and the integrated SNS application. We then measure the performance of MISG in terms of content response time and describe the result of the experiment.

Design of an effective framework for mash-up service development

With the advance of wireless communication technology, new computing technologies such as cloud computing, mobile computing, IoT, and etc. have been emerged. Based on emerging technologies, a variety of services have been provided for users. The mash-up service means a way to generate a new service by mixing more than two of existing services. Since service developers exploit existing services to make a new service, the efficiency of the development has improved and the period of development decreased as well as the new service fulfill the various requirements. So far, simple mash-up services have been developed, but it is difficult for developers to generate complex mash-up service. In this paper, we proposed framework design for efficient mash-up service development. The proposed framework is designed to satisfy complex and various service requirements. We designed a service scenario called as Campus Safety Management Mash-up Service (CSMMS) to evaluate the feasibility of the proposed framework.

Scalable Video Streaming Relay for Smart Mobile Devices in Wireless Networks

Recently, smart mobile devices and wireless communication technologies such as WiFi, third generation (3G), and long-term evolution (LTE) have been rapidly deployed. Many smart mobile device users can access the Internet wirelessly, which has increased mobile traffic. In 2014, more than half of the mobile traffic around the world was devoted to satisfying the increased demand for the video streaming. In this paper, we propose a scalable video streaming relay scheme. Because many collisions degrade the scalability of video streaming, we first separate networks to prevent excessive contention between devices. In addition, the member device controls the video download rate in order to adapt to video playback. If the data are sufficiently buffered, the member device stops the download. If not, it requests additional video data. We implemented apps to evaluate the proposed scheme and conducted experiments with smart mobile devices. The results showed that our scheme improves the scalability of video streaming in a wireless local area network (WLAN).

Development of gate security system based on mash-up framework

Variety of types of security systems have been utilized in a lot of places such as government office, company, and etc. Among them, gate security system is a representative security system. In the existing gate security systems, ID card or biometrics is frequently exploited for identification and authorization. ID card based gate security system is widely adopted, but it is vulnerable to replication and modification of the ID card. Biometrics based gate security system has no weakness of replication and modification, but it requires high complexity and shows the high false identification ratio rather than ID card based system. In this paper, we proposed gate security system based on mash-up framework. In our scheme, both ID card and biometrics are utilized to prevent the use of forged ID card and to increase the ratio of identification. We implemented the proposed scheme for performance evaluation, and our proposed scheme shows better performance than the existing gate security systems.

A synchronized playback method with dynamic buffering time awareness for media streaming

We propose a synchronized playback method for the real-time synchronization of the playback position of streaming media to multiple clients from a streaming server. The playback-related information that is used in this synchronized playback method comprises the current time and the playback position, and the server transmits the playback position and the current time to the client. The client can determine the playback position of the server based on the playback position and the current time and can synchronize playback using this information. In this paper, we describe the configuration of the experimental environment for synchronized media playback and present the synchronization algorithms used in this method for both the server and the client. Then, we present a method for measuring the synchronization accuracy and the results of such measurements. The average synchronization accuracy is 26 msec. According to the Haas effect, the experimentally measured sync accuracy is sufficiently high that the corresponding sound error is not detectable by the human ear.

Development of a Visitor Recognition System Using Open APIs for Face Recognition

Recently, as the interest rate and necessity for security is growing, the demands for a visitor recognition system are being increased. In order to recognize a visitor in visitor recognition systems, the various biometric methods are used. In this paper, we propose a visitor recognition system based on face recognition. The visitor recognition system improves the face recognition performance by integrating several open APIs as a single algorithm and by performing the ensemble of the recognition results. For the performance evaluation, we collected the face data for about five months and measured the performance of the visitor recognition system. As the results of the performance measurement, the visitor recognition system shows a higher face recognition rate than using a single face recognition API, meeting the requirements on performance.