Jae-Han Lim

Recent advances in communications, controls, and embedded systems have changed the perception of a car. A vehicle has been the extension of the man’s ambulatory system, docile to the driver’s commands. It is now a formidable sensor platform, absorbing information from the environment (and from other cars) and feeding it to drivers and infrastructure to assist in safe navigation, pollution control, and traffic management. The next step in this evolution is just around the corner: the Internet of

Phase change materials (PCMs) have been considered as an innovative technology that can reduce the peak loads and heating, ventilating and air conditioning (HVAC) energy consumption in buildings. Basically they are substances capable of storing or releasing thermal energy as latent heat. Because the amount of latent heat absorbed or released is much larger than the sensible heat, the application of PCMs in buildings has significant potential to reduce energy consumption. However, because each PC

In vehicular safety systems, two types of safety messages are required: Emergency Safety Message (ESM) and Periodic Beacon Message (PBM). The ESM has to be disseminated within a specified area with stringent delay and delivery ratio requirements, while the PBM does not need to meet these requirements. For exchanging the safety messages in Vehicular Ad-hoc NETwork (VANET), Inter-Vehicle Communication (IVC) is necessary whose de facto standard is Dedicated Short-Range Communications (DSRC). Howeve

The electric power generation efficiency of photovoltaic (PV) panels depends on the solar irradiation flux and the operating temperature of the solar cell. To increase the power generation efficiency of a PV system, this study evaluated the feasibility of phase change materials (PCMs) to reduce the temperature rise of solar cells operating under the climate in Seoul, Korea. For this purpose, two PCMs with different phase change characteristics were prepared and the phase change temperatures and

Ambient backscatter communication enables passive sensors to convey sensing data on ambient RF signals in the air at ultralow power consumption. To extract data bits from such signals, threshold-based decoding has generally been considered, but suffers against Wi-Fi signals due to severe fluctuation of OFDM signals. In this paper, we propose a pattern-matching-based decoding algorithm for Wi-Fi backscatter communications. The key idea is the identification of unique patterns of signal samples th

To meet the increasing demands for remote sensing, a number of radar systems using Linear Frequency Modulation (LFM) waveforms have been deployed, causing the problem of depleting frequency resources. To address this problem, several researchers have proposed the Spectrum Shared Radar System (SSRS) in which multiple radars share the same frequency band to transmit and receive their own signals. To mitigate the interferences caused by the signal transmission by other radars, SSRS employs orthogon

Vehicular safety system has been drawing considerable attention as a key application of Vehicular Ad-hoc NETworks (VANETs). In the safety system, there are two types of safety messages: Emergency Safety Messages (ESM) and Periodic Beacon Messages (PBM). The ESM has to be disseminated to vehicles within specified area and meet latency and delivery ratio requirements, while the PBM is transmitted periodically with vehicle information such as position, speed and direction. For vehicular communicati

In wireless networks, broadcasting is a fundamental communication primitive for network management and information sharing. However, in multi-channel networks, the broadcast efficiency is very poor as devices are distributed across various channels. Thus, a sender tries all channels for broadcasting a single message, which causes large overhead. In this paper, we propose a novel scheme for efficient broadcast in multichannel networks. Our scheme leverages the overlapped band, which is the freque

Recently, geothermal heat pumps (GHPs), which are normally known as ground-source heat pumps (GSHPs), offer many advantages for heating and cooling of commercial buildings due to the higher energy efficiency compared with conventional EHP system. In Korea, a recent requirement for mandatory implementation of the renewable energy systems in public building has been enforced for buildings with floor area exceeding 3000 m2. While GHPs may be more costly to install initially than the regular heat pu

Weather radar networked system (WRNS) is composed of multiple weather radars that transmit a radio signal and receive an echo signal reflected by weather targets. In the current form of WRNS, each radar exploits a different non-orthogonal frequency band, which leads to inefficiency in frequency usage. To tackle this issue, we propose a novel frequency-shared WRNS and investigate its feasibility via actual experiments. The challenges in a frequency-shared WRNS lie in mitigating: 1) interference f

The purpose of this study was to evaluate the characteristics of daylighting environment in classroom of an school building due to the external shading devices such as fixed louvers, light shelves and exterior venetian blinds. In this study, we have made a field research with regard to the facade design in classroom of an school building. And we have made a classification of external shading devices considering the design parameters. Finally, through RADIANCE simulation, we have calculated the s