H.A. Chan

Energy Efficient Clustering Algorithms for Wireless Sensor Networks

Energy efficiency is a major concern in wireless sensor networks (WSNs). Many clustering algorithms have been proposed for such a purpose. This paper investigates the existing clustering algorithms. The algorithms have been classified and some representatives are described in each category. After analyzing the strengths and the weaknesses of each category, an important characteristic of WSNs is pointed out for further improvement of energy efficiency for WSNs.

Superconducting gravity gradiometer for space and terrestrial applications

A three‐axis superconducting gravity gradiometer with a potential sensitivity better than 10−3 Eotvosu2009Hz−1/2 is currently under development for applications in space. Although such a high sensitivity may be needed for only a limited number of terrestrial applications, superconductivity offers many extraordinary effects which can be used to obtain a gravity gradiometer with other characteristics necessary for operation in a hostile moving‐base environment. Utilizing a number of recently devised techniques which rely on certain properties of superconductors, we have produced a design for a sensitive yet rugged gravity gradiometer with a high degree of stability and a common‐mode rejection ratio greater than 109. With a base line of 0.11 m, a sensitivity of 0.1 Eotvosu2009Hz−1/2 is expected in an environment monitored to a level of 10−2 mu2009s−2u2009Hz−1/2 for linear vibration and 7×10−6 radu2009s−1u2009Hz−1/2 for angular vibration. A conventional stabilized platform can be used at this level. The intrinsic noise level, which ...

Honeycyber: Automated signature generation for zero-day polymorphic worms

Signature-based intrusion detection systems (IDSs) can be evaded by polymorphic worms which vary their payloads in every infection attempt. In this paper, we propose Honeycyber, a system for automated signature generation for zero-day polymorphic worms. We have designed a novel double-Honeynet system, which is able to automatically detect new worms and isolate the attack traffic from innocuous traffic. We introduce unlimited Honeynet outbound connections, which allow us to capture different payloads in every infection of the same worm. The system is able to generate signatures to match most polymorphic worm instances with low false positives and low false negatives.

A Survey on Cluster Schemes in Ad Hoc Wireless Networks

Efficient cluster schemes play an important role in the self-organizing ad hoc wireless networks. This paper surveys and compares recent cluster schemes. We classify some of these schemes into the 3 major categories of (1) energy efficient schemes, (2) K-tree schemes, and (3) management schemes. Issues in these schemes are considered: overlaps between the clusters; clusterhead (CH) not at the center of the cluster; higher power consumption in CHs than in normal nodes; energy wasted by duplicated transmission of data. A TMDA dynamic cluster (TDC) algorithm trying to solve these problems is also proposed for ad hoc wireless sensor networks

IEEE802.21 Optimized handover delay for proxy Mobile IPV6

Next generation wireless networks are envisaged to be a combination of different but complementary access technologies. Interworking of these heterogeneous wireless networks will provide ubiquitous access to roaming network users. Thus, a seamless mobility mechanism with low handover delay to maintain active communication flows during handover across these networks is required. Several solutions, mainly host-based localized mobility management schemes, have been widely proposed to reduce handover delay in heterogeneous wireless networks. However, the handover delay remains high and unacceptable for delay-sensitive services. Moreover, host-based mobility management schemes involve the mobile node in mobility-related signaling hence effectively increasing the handover delay. This paper analyzes the reduction of handover delay in a network-based localized mobility management framework assisted by IEEE 802.21 media independent handover services. It compares the handover signaling procedures with host-based localized Mobile IPv6 (HMIPv6), with network-based Mobile IPv6 (PMIPv6), and with PMIPv6 assisted by IEEE 802.21 to show how much handover delay reduction can be achieved.

Fuzzy Logic Based Call Admission Control for Next Generation Wireless Networks

Different radio access technologies (RATs) such as UMTS, WiMax, WLAN, etc, will coexist in next generation wireless networks (NGWN). This coexistence of RATs necessitates joint radio resource management (JRRM) for efficient radio resource utilization and improved users satisfaction. Admitting a call into the most appropriate RAT based on many selection criteria is major challenge in NGWN. This paper focuses on joint call admission control (JCAC) algorithm which is one of the JRRM algorithms. We propose a Fuzzy Logic based JCAC scheme for NGWN. The JCAC scheme consists of local CAC algorithms and a RAT selection algorithm. Each RAT has a local CAC algorithm which select the most appropriate cell for an incoming call, and determine whether the call can be admitted into the cell or not. A RAT selection algorithm then selects the most appropriate RAT for the incoming call among the RATs whose selected cell meets the local call admission condition. The proposed JCAC scheme is illustrated using two local CAC criteria and five RAT selection criteria.

Streaming multimedia content over home network with an intelligent controller

A product to stream multimedia content with an intelligent control in a home network environment is designed and implemented. The home network used in this multimedia content streaming design consists of a multimedia center, client player (MP3 player or MPEG-I video set-top-box) and a remote control type device (palm pilot PDA). The multimedia center streams MP3 songs or MPEG-I video clips in multicasting mode using real time transport protocol (RTP). The client player receives RTP packets from the multicast channel and decodes the streaming data back to analog signals. Palm pilot PDA gets a list of songs and video clips from the multimedia center and indicates the client machines to playback the contents. The implementation of the whole environment and its operation are under Linux OS with various applications, tools and packages.

Joint Call Admission Control for Next Generation Wireless Network

Next generation wireless network (NGWN) will be heterogeneous in nature where different radio access technologies (RATs) such as UMTS, WiMax, WLAN, etc, coexist. This coexistence necessitates joint radio resource management (JRRM). This paper focuses on joint call admission control (JCAC) for NGWN. Factors that determine a users preference for a particular RAT are discussed. We propose a JCAC algorithm which considers the users preference in making admission decision. A specific case where the user prefers to be served by the RAT which has the least service cost is modeled and evaluated using Markov decision process. The results obtained shows that overall service cost in heterogeneous network can be significantly reduced by using the proposed joint call admission control

A formulation of environmental stress testing and screening

Although hard-defects may be detectable in factory tests, weak products may exhibit failures or degrade only under certain stress conditions. Without stress testing, these weak products may often be shipped to customers causing early failures in the field. Early failures usually come from product weaknesses resulting in the presence of weak populations and the lower end of a broad main population for the product strength distribution. The requirements on the product strength distribution are determined by the reliability criteria and by the distribution of the lifetime maximum stress of the product. Environmental stress testing (EST), which includes corrective actions, aim at eliminating product weaknesses to achieve robustness. Environmental stress screening may augment EST, but is applicable only under certain conditions. Its applicability also depends on whether the dominating failure may be stimulated by threshold stress, cumulative stresses or their combination.<<ETX>>

Integrating fast mobile IPv6 and SIP in 4G network for real-time mobility

4G mobile communication network will encompass various access technologies to provide a heterogeneous environment with IP as the network protocol. Within the heterogeneity framework, there is a need to create mobility standards to support seamless roaming among the various access technologies and the adaptive provisioning for multimedia applications. In this paper, an analysis of combining fast mobile IPv6 and session initiation protocol (SIP) to handle real-time mobility is proposed. Advanced resource management techniques to support quality of service (QoS) are also considered for real-time mobility within the next generation network (NGN) platform. The techniques may use a QoS Manager to allow an end-to-end coordination and provisioning of quality of service. The function of the QoS manager also includes dynamic allocation of resources during handover.