Jong Hoon Youn

Adaptive radio channel allocation for supporting coexistence of 802.15.4 and 802.11b

As the explosive growth of the ISM band usage continues, there are many scenarios where different systems operate in the same place at the same time. One of growing concerns is the coexistence of wireless systems [18]. For the successful deployment of mission-critical systems such as wireless sensor networks, it is required to provide a solution for the coexistence. In this paper, we propose a new scheme using multiple radio channels for the coexistence of 802.15.4 LRWPAN and 802.11b WLAN. To evaluate the effectiveness of the proposed scheme, measurement and simulation study are conducted. The simulation results show that the proposed scheme is effective in performance improvement for multi-hop largescale network of 802.15.4. Keywords-component; coexistence; interference; ISM band; 802.15.4; 802.11b

Survey and evaluation of real-time fall detection approaches

As we grow old, our desire for independence does not diminish; yet our health increasingly needs to be monitored. Injuries such as falling can be a serious problem for the elderly. If a person falls and is not able to get assistance within an hour, casualties arising from that fall can result in fatalities as early as 6 months later [1]. It would seem then that a choice between safety and independence must be made. Fortunately, as health care technology advances, simple devices can be made to detect or even predict falls in the elderly, which could easily save lives without too much intrusion on their independence. Much research has been done on the topic of fall detection and fall prediction. Some have attempted to detect falls using a variety of sensors such as: cameras, accelerometers, gyroscopes, microphones, or a combination of the like. This paper is aimed at reporting which existing methods have been found effective by others, as well as documenting the findings of our own experiments. The combination of which will assist in the progression towards a safe, unobtrusive monitoring system for independent seniors.

Fault-tolerant wormhole routing algorithms in meshes in the presence of concave faults

A fault ring is a connection of only nonfaulty adjacent nodes and links such that the interior of the ring contains only faulty components. This paper proposes two wormhole routing algorithms that deal with more relaxed shapes of fault rings than previously known algorithms in the mesh networks. As a result, the number of components to be made disabled would be reduced considerably in some cases. First algorithm, called F4, uses four virtual channels and allows all four sides of fault rings to contain concave shapes. Second algorithm, F3, permits up to three sides to contain concave shapes using only three virtual channels. Both F3 and F4 are free of deadlock and livelock and guarantee the delivery of messages between any pair of nonfaulty and connected nodes in the network.

A topology-independent transmission scheduling in multihop packet radio networks

In this paper, based on coding theory concepts, a new time scheduling algorithm for multihop packet radio networks is described. Each mobile host is assigned a word from an appropriate constant weight code of length n, distance d and weight w. The host can send a message at the j/sup th/ slot provided the assigned code has a 1 in this j/sup th/ bit. The proposed algorithm is better than the previously known algorithms in terms of minimum system throughput. The algorithm also preserves other desired properties, such as topology independence, guaranteed minimum throughput, bounded maximum delay, and fair transmission policy.

Wireless sensor-driven intelligent navigation robots for indoor construction site security and safety

This paper introduces an on-going research effort at the Peter Kiewit Institute (PKI) at Omaha, Nebraska for developing sensor-aided intelligent mobile robots that provide high-level navigation functions for indoor construction site security and safety using wireless sensor networking (WSN) technology. The ultimate goal of the research is the complete integration of the sensor-equipped robots into the WSN system to visualize sensed data information into 3D graphical control interface for advanced planning and execution against any anomalies that have been detected in warehouses, office buildings, manufacturing facilities, and various construction sites - everywhere theres a need for advanced frontline security.

Recycled path routing in mobile ad hoc networks

In mobile ad hoc networks, many routing algorithms rely on some form of flooding to accomplish the route discovery process. Flooding, however, consumes many valuable network resources such as time, bandwidth, and power. Most current routing schemes expire valid routes after a time period to account for nodal movement. This paper proposes a new route discovery method, called recycled path routing (RPR), which directs broadcasts toward the destination node even in the absence of location information. The recycled path routing scheme reduces the search space for the destination node by implementing an expired route cache that is utilized by each node in the network. Routes are added to the expired route cache as they expire from the active route cache and remain there until some time interval has passed or a new route has been discovered. Since these expired routes can provide valuable insight into finding new routes, RPR uses them to direct broadcasts toward the destination node. RPR can save a significant quantity of valuable network resources because only nodes near the optimal path will rebroadcast route requests.

Efficient encoding and decoding schemes for balanced codes

In this paper, we introduce two encoding and decoding methods for balanced codes. The proposed methods are more efficient in terms of computational complexity. The first one complements several appropriate bits at a time instead of complementing one bit at a time as done in Knuths method. The second one is a parallel implementation of Knuths method.

On-board processing of acceleration data for real-time activity classification

The assessment of a persons ability to consistently perform the fundamental activities of daily living is essential in monitoring the patients progress and measuring the success of treatment. Therefore, many researchers have been interested in this issue and have proposed various monitoring systems based on accelerometer sensors. However, few systems focus on energy consumption of sensor devices. In this paper, we introduce an energy-efficient physical activity monitoring system using a wearable wireless sensor. The proposed system is capable of monitoring most daily activities of the human body: standing, sitting, walking, lying, running, and so on. To reduce energy consumption and prolong the lifetime of the system, we have focused on minimizing the total energy spent for wireless data exchange by manipulating real-time acceleration data on the sensor platform. Furthermore, one of our key contributions is that all functionalities including data processing, activity classification, wireless communication, and storing classified activities were achieved in a single sensor node without compromising the accuracy of activity classification. Our experimental results show that the accuracy of our classification system is over 95%.

Block Design-Based Asynchronous Neighbor Discovery Protocol for Wireless Sensor Networks

Neighbor discovery is a significant research topic in wireless sensor networks. After wireless sensor devices are deployed in specific areas, they attempt to determine neighbors within their communication range. This paper proposes a new Block design-based Asynchronous Neighbor Discovery protocol for sensor networks called BAND. We borrow the concept of combinatorial block designs for neighbor discovery. First, we summarize a practical challenge and difficulty of using the original block designs. To address this challenge, we create a new block generation technique for neighbor discovery schedules and provide a mathematical proof of the proposed concept. A key aspect of the proposed protocol is that it combines two block designs in order to construct a new block for neighbor discovery. We analyze the worst-case neighbor discovery latency numerically between our protocol and some well-known protocols in the literature. Our protocol reveals that the worst-case latency is much lower than others. Finally, we evaluate the performance of BAND and existing representative protocols through the simulation study. The results of our simulation study show that the average and maximum latency of BAND is about 40% lower than that of existing protocols. Furthermore, BAND spends approximately 30% less energy than others during the neighbor discovery process.

Efficient data dissemination and aggregation in large wireless sensor networks

In this paper, we investigate an energy-efficient data dissemination scheme that prolongs the lifetime of battery-powered sensors by reducing the amount of communication required. In order to save energy and bandwidth, the proposed scheme constructs and maintains only one grid structure per data type, and sources of same data type share the grid structure to disseminate sensing data. Another novel idea in the proposed scheme is to use a hash function in order to retrieves the position of the nearest grid point. By using a hashing function, a sink can substitute expensive local query flooding with unicasting. Our simulation results show that the proposed scheme consumes much less energy than previously known schemes by sharing grid structures and eliminating local flooding.