Hyung-Sin Kim

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In this paper, we consider a new channel sounding scheme for opportunistic scheduling with the use of reduced channel information in the uplink of orthogonal frequency division multiplexing (OFDM)-based wireless systems. To reduce signaling overhead for the sounding, we propose a two step channel sounding process considering the correlation characteristic(More)
Low-power and lossy networks (LLNs) comprised of thousands of embedded networking devices can be used in a variety of applications, such as smart grid automated metering infrastruc-tures (AMIs) and wireless sensor networks. Connecting these LLNs to the Internet has even greater potential, leading to the emerging concept of the Internet of Things (IoT). With(More)
—RPL is an IPv6 routing protocol for low-power and lossy networks (LLNs) designed to meet the requirements of a wide range of LLN applications including smart grid AMIs, industrial and environmental monitoring, and wireless sensor networks. RPL allows bi-directional end-to-end IPv6 communication on resource constrained LLN devices, leading to the concept of(More)
Updating price tags in a large-scale market is a recurrent task, still performed manually in most markets. Given that human-errors can easily lead to customer complaints and accounting inaccuracies, the ability to autonomously reconfigure price tags can be of significant benefit. With the introduction of low-power display techniques such as electronic ink,(More)
In this paper, we consider uplink channel sounding in time division duplex (TDD) orthogonal frequency division multiplexing (OFDM)-based cellular systems. The channel information provided by uplink sounding may be necessary to exploit closed loop transmission techniques in TDD-OFDM systems. However, conventional sounding schemes may suffer from large(More)
—IEEE 802.15.4 networks employ a medium access control scheme based on carrier sense multiple access with collision avoidance (CSMA/CA). However, CSMA/CA may seriously experience contention collision, suffering from resource wastage in time-varying operation environments. In this paper, we consider the alleviation of contention collision in IEEE 802.15.4(More)
—In this paper, we consider the construction of a large scale wireless sensor network (WSN) by means of distributed network association with scalability. We design a network association mechanism that allows each router to have its own addressing space for unique addressing of its child nodes based on a pre-initialized addressing tree. We also design a(More)
—In this paper, we consider interference mitigation in IEEE 802.15.4 beacon-enabled cluster-tree networks. The proposed scheme first detects the presence of interference by means of packet-error detection and/or channel sensing in a cluster-wise manner. In the presence of interference, the coordinator (or cluster head) fast notifies the presence of(More)