Kamol Kaemarungsi

Indoor localization improvement via adaptive RSS fingerprinting database

In location fingerprinting based indoor positioning system, received signal strength (RSS) indications from a set of Wi-Fi access points are used as a unique fingerprint to identify a specific location. However these RSS fingerprints may become outdated when there are unanticipated environmental changes. Re-measuring RSS fingerprints for all locations to maintain an up-to-date RSS database incurs high operational cost, which is impractical in dynamically changed environment. In this paper, we propose a method to estimate the RSS fingerprint of a specific location from a set of neighboring re-measured RSS fingerprints, called “feedbacks”. The proposed method searches for new feedbacks and some necessary old RSS fingerprints in the cut-off area and then applies plane-interpolation to calculate the new RSS fingerprint for a specific location. Based on simulation results, about 5% of re-measured RSS feedbacks are required to satisfy 80% of positioning correctness in the simulated 30×30 m2 area.

Differences in bandwidth requirements of various applications due to IPv6 migration

In this paper, we compare performances of Internet applications in a transition network model of IPv6 to IPv4 (6 to 4) tunneling with those IPv4-only and IPv6-only network models. These applications are remote login, web browsing, voice communication, database transaction, and video streaming. The objective of this study is to investigate the differences in bandwidth requirements and delay effects among the three network models in order to prepare for future network capacity planning of Internet Service Providers. The performance studies are done through the OPNET v14.5 simulator to investigate the impacts on these applications for service providers which still have limited implementation of IPv6 and transition networks. The focused performance parameters are throughput and delay of these five different Internet applications.

Robust Floor Determination Algorithm for Indoor Wireless Localization Systems under Reference Node Failure

One of the challenging problems for indoor wireless multifloor positioning systems is the presence of reference node (RN) failures, which cause the values of received signal strength (RSS) to be missed during the online positioning phase of the location fingerprinting technique. This leads to performance degradation in terms of floor accuracy, which in turn affects other localization procedures. This paper presents a robust floor determination algorithm called Robust Mean of Sum-RSS (RMoS), which can accurately determine the floor on which mobile objects are located and can work under either the fault-free scenario or the RN-failure scenarios. The proposed fault tolerance floor algorithm is based on the mean of the summation of the strongest RSSs obtained from the IEEE 802.15.4 Wireless Sensor Networks (WSNs) during the online phase. The performance of the proposed algorithm is compared with those of different floor determination algorithms in literature. The experimental results show that the proposed robust floor determination algorithm outperformed the other floor algorithms and can achieve the highest percentage of floor determination accuracy in all scenarios tested. Specifically, the proposed algorithm can achieve greater than 95% correct floor determination under the scenario in which 40% of RNs failed.

Botnet Statistical Analysis Tool for Limited Resource Computer Emergency Response Team

Botnet is recognized as one of the fastest growing threat to the Internet and most users do not aware that they were victimized. ThaiCERT is one of many computer emergency response teams that have limited resources in term of budget to monitor and handle this kind of threat. An interim solution for teams with limited resource is to subscribe to the Shadowserver Foundation’s mailing list instead of deploying their own capturing and monitoring tools. The valuable information from the Shadowserver Foundation in form of plaintext e-mails may be difficult to manage and analyze. However, there is a need to analyze information provided by the Shadowserver Foundation to be able to efficiently handle botnet’s incidents for our own constituency. In this manuscript, we present our approach to handle the botnet threat using available information from the Shadowserver Foundation and describe our automate tool using by our incident handling team. Finally, we present our statistical data on botnet’s threat in our constituency over the last two years.

CPW-Fed disc patch antennas with an annular ground plane for UWB applications

This paper presents a design of an antenna for Ultra-Wide band (UWB) applications and a design of an UWB antenna with band-notched characteristics. The proposed antennas consist of an annular ring strip as a ground plane and there are two types of the radiating elements, a circular disc patch, and a C-shaped slot on disc patch. As a result, a circular disc patch radiating element has an impedance bandwidth with the return loss (S11<−10dB) and can operate over an UWB frequency range (3.1–10.6GHz). The antenna with the C-shaped slot showed rejection ability in WiMAX band (3.3–3.6 GHz).

Ultra-wideband pulse generator with cascode impulse shaping circuit

Ultra-wideband (UWB) pulse generator circuit is said to be the heart of any UWB systems. It is the fundamental circuit for application and development of UWB technology. This paper presents an UWB pulse generator with cascode transistors operating as a pulse shaping circuit to generate Gaussian pulses. In this work, the UWB pulse generator consists of three parts: an edge triggered driver, an edge sharpener SRD, and a cascode for impulse shaping. The proposed circuit allows the generator to create short and high amplitude Gaussian-like pulses at low-cost. Our measured UWB pulse was 1.0 ns pulse with 2.8 Vpeak.

Robust System Design Using BILP for Wireless Indoor Positioning Systems

In wireless indoor positioning system designs, reference node (RN) failures during the online phase cause received signal strength values to be unavailable. This leads to accuracy performance degradation and a lack of system reliability in smart office systems. Moreover, the major design concern in the reliability of indoor positioning systems under the faulty RNs during the online phase has not been yet investigated in previous works. To address these gaps, we propose a novel mathematical formulation using a Binary Integer Linear Programming (BILP) approach that employs the Simulated Annealing (SA) solution technique. The proposed robust system design aims to put in place a suitable number of RNs and to determine their optimum locations, which may be located on a single floor or on multiple floors. In particular, the proposed system design provisions to support robust operation both during a normal situation and when there are some RN failures. Experimental results and comparative performance evaluation revealed that the proposed robust system design outperformed other system designs and was able to achieve the highest location accuracy performance in both fault-free and RN-failure scenarios. Specifically, when nine of the RNs in a three-story building failed, the proposed system design achieved 84.6%, 54.7%, and 32.9% more accurate performance than the Uniform, the MSMR, and the PhI-Uni, respectively.

Pseudo-ranging Based on Round-Trip Time of Bluetooth Low Energy Beacons.

This paper presents a utilization of Bluetooth Low Energy (BLE) for a pseudo-ranging determination in indoor positioning systems. Most of BLE-based ranging techniques rely on Received Signal Strength Indicator (RSSI) of the broadcasting beacons, which has a shortcoming as it is highly sensitive to the surroundings or the orientation of the device. Therefore, this paper proposes the two-way Time-of-Flight (ToF) approach for ranging of BLE beacons. The Round-Trip Time (RTT) of the beacons has been measured using a CPU clock cycle generated by an external Temperature Compensated Crystal Oscillator (TCXO), and the pseudo-ranging calculation has been performed afterwards. The study results indicate that the accuracy can be improved by considering the RTT from the advertising channel that gives the best RSSI. The equation representing the relationship between the RTT and distance has been derived.