Hyung Su Lee

Surveillance Tracking System Using Passive Infrared Motion Sensors in Wireless Sensor Network

Wireless Sensor Networks for surveillance systems in home, office, or factory environment require correct tracking of intruders. For such systems, passive infrared motion sensors (PIR sensors) are ideal because they do not require any signal or devices on the object to be tracked and they can work in dark environment as well. This paper first analyzes the performance and the applicability of the PIR sensors for security systems. Then, we propose a region-based human tracking algorithm with actual implementation and experiment in real environment. From the experiments, we show that the human tracking algorithm based on the PIR sensors performs very well with proper sensor deployment.

The Method of Location Error Detection and Correcting in Smart Home Environments

The location awareness system is an essential factor for the development of low cost sensor networks for use in the smart home environments and ubiquitous networking. This paper addresses the problem of tracking a moving intelligent robot using the pharos indoor location system. Our motivating applications include intelligent robot navigation, where location sensors provide position information to a moving robot. All of these applications require the position of a device moving at human speeds to be tracked. Ubiquitous indoor environments often contain substantial amounts of metal and other such reflective materials that affect the propagation of radio frequency signals in non-trivial ways, causing severe multi-path effects, dead-spots, noise, and interference. In this paper, we address the location error detection and correcting problems of the sensor network platform with RF and ultrasonic for location tracking system. Especially we present a novel detecting error of location and correcting using LQI that is particularly well suited to support context-aware smart home computing. It is achieved by considering the speed variance of the moving object and the corrected the interference errors. This proposed scheme applied the method of an error correct to the mobile object. We brought a 5% efficiencies comparing with a three existing schemes (listener inference algorithm). And The system called Pharos, aims to combine the advantages of real-time tracking systems that implement distributed environment with regardless of infrastructure or infrastructure-less wireless sensor networks.

Multi-Channel Multi-Path video transmission over wireless sensor networks

Recently, various applications have emerged which utilize wireless sensor network (WSN) consisting of low cost and low power sensors in smart spaces. Here a great deal of research has been carried out on transmitting video over WSN. WSN has limited resources in terms of bandwidth and data processing capability, while video requires bulk data to be transmitted. In this paper we propose a two-stage Quality of Service (QoS) guaranteeing scheme for video transmission over WSN, called the Multi-Channel Multi-Path (MCMP) scheme. It selects the best paths from the source camera to the gateway based on hop-count, aggregated path energy, BER, and end-to-end delay. A failure recovery scheme is also provided to cope with link failure. Computer simulation reveals that the proposed scheme significantly outperforms the existing scheme in terms of channel utilization and delay.

Context-Aware cross layered multimedia streaming based on variable packet size transmission

Multimedia streaming is usually disturbed by the surroundings. Especially in the ubiquitous computing environment, seamless multimedia service is difficult to provide due to harsh environment of wireless network and limited power of small mobile devices. In this paper we propose a scheme which can enhance the QoS of MPEG-4 streaming. By exhaustive experimental test, we find that the QoS of multimedia streaming significantly depends on the SNR (Signal-to-Noise Ratio). The proposed scheme employs five different packet sizes and selects a one according to the SNR value and the data on the packet delay and loss. Experiment on MPEG-4 video transmission reveals that the proposed streaming with variable packet size allows fast adaptation before the error propagates, minimizes the power consumption, and saves the buffer space compared to the streaming with fixed packet size.

A new data propagation scheme for WSN network reprogramming in a noise-full environments

Network reprogramming should be able to transmit a great amount of data reliably given that it transmits the codes of operating systems and execution programs. Existing studies guarantee 100% reliability using ACK retransmission or NACK transmission. However, in reality, the potential for transmission error is quite high in the sensor network field. Hence, the methods used in existing studies require frequent retransmission, thus undermining the performance of the sensor network and increasing the energy overhead. This paper suggests a new data propagation method that decreases the rate of retransmission. The new method improves the reprogramming performance of the sensor network through its use of a data encoding method that effectively propagates the reprogramming data. The author compared the new method with Deluge, a very capable network reprogramming method used in TinyOS. For the comparison, the author applied the new method to Deluge and measured its performance using TOSSIM, a TinyOS network simulator. As a result, the new method showed a maximum performance enhancement of 38%.

A study on the indoor real-time tracking system to reduce the interference problem

The real-time tracking system is an essential component in the development of low cost sensor networks to be used in pervasive and ubiquitous computing. In this paper we address the interference problem of the sensor network platform that uses ultrasonic for location tracking. We also present a novel scheme reducing the error rate caused by interference, which is particularly suited for supporting context-aware computing. It is achieved by considering the speed variance of the mobile node and thereby correcting the interference errors. Performance evaluation using an actually implemented platform, Pharos, reveals that the proposed scheme outperforms the three existing schemes. It also identifies that error rate decreases as the number of packets transmitted for distance estimation increases, while it increases as the speed of the mobile node increases.

Packet control mechanism for seamless multimedia streaming service in wireless network

In the pervasive computing environment seamless multimedia service is difficult since the circumstances keeps changing and the portable devices have restrictive resources and power. In this paper we propose a variable packet size streaming scheme to enhance the QoS of MPEG-4 streaming in wireless environment. Though exhaustive experimental test, we found that the QoS of multimedia streaming is deeply related with SNR (signal-to-noise ratio). Thus we use five different packet sizes and decide the size according to the packet delay and loss rate with the RTP/RTCP. Experiment of a realistic setting reveals that the proposed approach displays higher PSNR than the existing transmission scheme of fixed size packets