Jae Yeol Ha

Learn More
—The number of frequency channels specified for IEEE 802.15.4 low-rate wireless personal area networks (LR-WPANs) does not suffice to operate a variety of collocated WPAN applications that the standard is targeting. To overcome this limit, we introduce Virtual Channel, a novel concept to increase the number of available channels by efficiently managing(More)
— Two mechanisms are proposed to enhance through-put and energy efficiency of IEEE 802.15.4 CSMA-CA. The first one is an enhanced collision resolution (ECR) mechanism that adjusts the backoff exponent (BE) based on both consecutive clear channel assessment (CCA) busy results and a packet transmission. The second one is an enhanced backoff (EB) mechanism(More)
—This letter proposes the enhanced hierarchical routing protocol (EHRP) for ZigBee Mesh Networks. The EHRP finds the shortest hierarchical path based on the ZigBee hierarchical addressing scheme. The EHRP provides efficient and reliable routing paths. In addition, the EHRP is completely compatible with ZigBee v.1.0 standard. Simulation results demonstrate(More)
The number of channels specified for IEEE 802.15.4 Low-Rate Wireless Personal Area Networks (LR-WPANs) is too few to operate many applications of WPANs in the same area. To overcome this limit, we introduce Virtual Channel , a novel concept to increase the number of available channels when various WPAN applications coexist. A virtual channel is basically(More)
In this paper, we propose a near-ultrasound chirp signal-based communication for the TV's 2nd screen services. While near-ultrasound (with under 20 kHz frequency) communication has been developed for various applications recently, none of the previous work provides a perfect solution for 2nd screen services between TVs and smart devices. This is due mainly(More)
Wireless Sensor Network (WSN) is mostly used in real time applications, like as automobile traffic control, military purpose, medical area and environment examination. ZigBee is a Wireless Personal Area Network (WPAN) based on IEEE 802. 15. 4 wireless protocol. ZigBee gives short distance communication with low data rate, low power consumption and low(More)
  • 1