Byung Joon Park

Virtual sink rotation: low-energy scalable routing protocol for ubiquitous sensor networks

In this paper we propose a new routing protocol called virtual sink rotation (VSR) routing for large-scale sensor networks. VSR can efficiently handle a large number of sources as well as a large number of sinks with potential mobility. Each sensor node is not required to know the global network topology nor the location awareness. The main ideas underlying the VSR are two folds. First, to alleviate the frequent location updates associated with multiple mobile sinks, the algorithm introduces a virtual sink, which acts as a data collection and dissemination center to collect the data from all the sources and forward them to the actual sinks. This virtual sink can easily support multiple sinks as well as the mobility of the sinks. Second, to address the excessive energy consumption among the sensor nodes around a sink, VSR employs virtual sink rotation, which distributes the role of the virtual sink over all the participating sensor nodes, thus achieving a uniform energy distribution across the entire sensor field and prolonging the lifetime of the network. Experimentation results confirm that the VSR routing can significantly save energy while it can also reduce both the message delay and the message delivery failures compared to previous schemes.

Efficient Detection of Content Polluters in Social Networks

A large number of Internet users are currently using social networking services (SNS) such as Twitter and Facebook. However, the SNS users are exposed to threats of malicious messages and spams from unwanted sources. It would be useful to have an effective method for detecting spammers or content polluters on social networks. In this paper, we present an efficient method for detecting content polluters on Twitter. Our approach needs only a few feature values for each Twitter user and hence requires a lot less time in the overall mining process. We demonstrate that our approach performs better than the previous approach in terms of the classification accuracy and the mining time.

Efficient decision support for detecting content polluters on social networks: an approach based on automatic knowledge acquisition from behavioral patterns

With the rise of social networking services such as Facebook and Twitter, the problem of spam and content pollution has become more significant and intractable. Using social networking services, users are able to develop relationships and share messages with others in a very convenient manner; however, they are vulnerable to receiving spam messages. The automatic detection of spammers or content polluters on the network can effectively reduce the burden on the service provider in making a decision on appropriate counteractions. Content polluters can be automatically identified by using the supervised learning technique of artificial intelligence. To build a classification model with high accuracy automatically from the training data set, it is important to identify a set of useful features that can classify polluters and non-polluters. Moreover, because we deal with a huge amount of raw data in this process, the efficiency of data preparation and model creation are also critical issues that need to be addressed. In this paper, we present an efficient method for detecting content polluters on Twitter. Specifically, we propose a set of features that can be easily extracted from the messages and behaviors of Twitter users and construct a new breed of classifiers based on these features. The proposed approach requires only a minimal number of feature values per Twitter user and thus adds considerably less time to the overall mining process compared to other methods. Experiments confirm that the proposed approach outperforms previous approaches in both classification accuracy and processing time.

BCTMA (bi-directional cut-through medium access) protocol for 802.11-based multi-hop wireless networks

In DCF of 802.11-based multi-hop wireless networks, a channel access sequence of 4-way handshake with RTS-CTS-DATA-ACK is used to forward a single packet. For multi-hop packet forwarding, multiple channel accesses with this 4-way handshake are required, and this might entail multiple collisions, which, in turn, results in poor end-to-end performance. To eliminate the overhead of these multiple channel accesses and, as a result, to reduce the possible number of collisions, the DCMA (Data-driven Cut-through Medium Access) protocol has been proposed[5]. We name the scheme used in the DCMA protocol the forward cut-through scheme. In this paper, we propose BCTMA (Bi-directional Cut-Through Medium Access)protocol for high performance 802.11-based multi-hop wireless networks by combining both forward and backward cut-through schemes. We have implemented BCTMAprotocol in ns-2[9]. We conducted a comprehensive simulation to study the performance improvements. The simulation results indicate that the performance is significantly improved and the number of dropped packets due to collisions can be significantly reduced as much as a half.

Study on L-V-C (Live-Virtual-Constructive) Interoperation for the National Defense M&S (Modeling & Simulation)

The evolution of the information technologies like computer and the Internet has been largely affecting military technology area. It has been changing warfare aspect a lot, and greatly improving high-tech fighting power as well. This study proposes a way to construct and operate the synthetic theater of war in order to improve the national military combat training, based on the emerging concept of it. This paper first studies the component technologies of the L-V-C(live virtual constructive)-based synthetic theater of war simulation system that enables the military training to be as similar as in the real combat field, and defines the various variables that can make effective use of the IEEE standard HLA/RTI By doing that, this paper proposes an interoperable scheme that is suited to L-V, V-C, and L-C interoperation.

On performance improvement for 802.11-based multi-hop ad hoc wireless networks

Collision due to the hidden terminals in contention-based medium access control protocols is one of the main reasons of the poor end-to-end performance of wireless networks. In this paper, we present a novel approach for MAC protocol improvements for 802.11-based multi-hop ad-hoc wireless networks to reduce unnecessary collisions, resulting in performance enhancement. Our main idea is to reduce unnecessary collisions by introducing a new time interval, named CAI (Collision Avoidance Interval) for the node in the carrier sensing zone[6]. Specifically, in the context of 802.11, the four-way handshake is specified as a collision avoidance medium access protocol and the protocol behavior for the node in the carrier sensing zone is required to be modified when it senses a signal for CTS, such that the node defers transmitting a frame during CAI, unlike during EIFS in the 802.11 specification. We carry in-depth analysis of the protocol behavior and have conducted a comprehensive simulation to study the performance improvements. The simulation results show that the end-to-end performance is greatly increased and the number of dropped frames due to collision is significantly reduced as much as one half, and so is the throughput cost.