다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Statistics for Spatial Data.

"A Survey of Mobility Models for Ad Hoc Network Research," Wireless Comm. & Mobile Computing (WCMC) : Special issue on Mobile Ad Hoc Networking : Research

In the performance evaluation of a protocol for an ad hoc network, the protocol should be tested under realistic conditions including, but not limited to, a sensible transmission range, limited buffer space for the storage of messages, representative data traffic models, and realistic movements of the mobile users (i.e., a mobility model). This paper is a survey of mobility models that are used in the simulations of ad hoc networks. We describe several mobility models that represent mobile nodes whose movements are independent of each other (i.e., entity mobility models) and several mobility models that represent mobile nodes whose movements are dependent on each other (i.e., group mobility models). The goal of this paper is to present a number of mobility models in order to offer researchers more informed choices when they are deciding upon a mobility model to use in their performance evaluations. Lastly, we present simulation results that illustrate the importance of choosing a mobility model in the simulation of an ad hoc network protocol. Specifically, we illustrate how the performance results of an ad hoc network protocol drastically change as a result of changing the mobility model simulated.

/pdf/a-survey-of-mobility-models-for-ad-hoc-network-research-ygkxat400x.pdf

A survey of mobility models for ad hoc network research

http://www.csun.edu/~andrzej/COMP529-S05/papers/Mesh%20Networks%20Survey.pdf

Wireless mesh networks: a survey

Wireless network access from moving vehicles can be challenged by many factors such as connection opportunities, mobility, handshake phase, and data sizes, etc. The handshake time and transmission rate can be influenced differently in vehicle-to-roadside networks than a static wireless LAN access. The radio signal strength changes and Doppler shift occur when the vehicle is moving. Switching among APs could cause significant connection stale, which could have a major impact on the handshake phase and transmission rate. The purpose of our paper is to enhance the understanding of these influential factors and study the feasibility of mobile vehicle access for a hybrid environment that contains sparse and dense access point deployments. Experiment data was collected in a moving vehicle, which traveled around the campus of the university. In the data analyze part, the above factors are analyzed for packet inter-arrival time, response time and transmission rate; Our main results are focused in security enabled protocols such as HTTPS and SSH, as well as TCP file transmission. Our data shows that IEEE 802.11g is still weak in supporting mobile vehicle access to the Wireless LAN. We expect that IEEE 802.11p, designed specifically for vehicle networks, can provide better mobile services.

Handshake time and transmission rate of 802.11g measurement in vehicular networks

ProtoGENI is one of the prototype implementations of global environment for network innovations (GENI). ProtoGENI proposes and executes the GENI control framework, including resource management and allocation for authenticated and authorized experimenters. Security and inevitably are the most important concerns in the whole development process. In this paper, we study and evaluate its security vulnerabilities according to GENI's security goals. We analyze the threat model of ProtoGENI and categorize four broad classes of attacks. Based on the role of an active experimenter, we demonstrate experiments as proof of the concept that each class of attacks can be successfully launched using common open source network tools. We also present analysis and experiments that show perspectives on the potential risks from an external user. Furthermore, we discuss the feasibility and possible defense strategies on ProtoGENI security with respect to our preliminary experiments and potential future directions. Our contribution lies in examining known vulnerabilities without requiring sophisticated experiments while remaining effective. We have reported our findings to the ProtoGENI Team. Our work indicates that the solutions have been deployed. This paper validates that experiment-based vulnerability exploration is necessary.

ProtoGENI, a Prototype GENI Under Security Vulnerabilities: An Experiment-Based Security Study

This paper presents a design of reconfigurable hardware platform for wireless sensor networks to achieve high flexibility and robustness in system operation and resource utilization. The goal of this research is to develop a new type of sensor networks with cognitive features (e.g., context awareness and situation understanding) such that human behavioral biometrics can be measured through distributed low-cost sensors. The proposed reconfigurable hardware platform can adjust its sensing and computing resources with respect to changing contexts and situations. It includes three components: (1) reconfigurable analog circuit for adaptive sensor conditioning, (2) reconfigurable ADC for maintaining high signal-to-noise ratio, and (3) FPGA based reconfigurable computing for situation understanding. In behavioral biometrics applications, such a reconfigurable platform can automatically change circuit parameters, ADC resolutions, filter coefficients, and algorithms according to application contexts and situations derived from sensory signal features. As a result, the sensing system can be adaptive to various behavioral biometrics applications with high fidelity and accuracy. Experimental results have demonstrated the advantages of the proposed hardware platform.

A reconfigurable hardware platform for cognitive sensor networks towards behavioral biometrics

In delay-tolerant networks (DTN), nodes explore various opportunities to connect and communicate with each other. A series of encounters of different nodes will create such opportunities and spread a message among many nodes and eventually deliver to the designated destination. We study one common DTN scenario where the message exchanges happen when nodes meet others at certain locations. In this situation, the success of message delivery and the quality of the delivery depend highly on the likeliness of nodes' encounters and time elapsed between encounters. We study two important qualities of service requirements: the probability of two nodes meeting each other (encounter probability) and the time it takes for two nodes to meet (encounter delay). The key considerations are how nodes pick their next locations (mobility patterns) and the features of the dwell time. In this paper, we will study several mobility patterns, including random movement, and activity agenda based movement. We also study an additional message delivery constraint, i.e., a message will be dropped if not delivered within a limited number of locations visited. We develop mathematical formulas using Markov chain as a main tool. Our work is presented as an illustration through case studies. The methodology applies to mobility models alike and is extendable to real trace analysis. We present numerical results when closed form formulas cannot be acquired. Our results help the management of message delivery for DTN, e.g., in selecting a proper time-to-live threshold for a message.

Delay management in delay-tolerant networks

Wireless networks have experienced fast deployments and fast user population growth. Understanding the delay characteristics can help us to correctly evaluate the performance of wireless networks. In this paper, we will analyze the delay performance of single-hop and multi-hop ad-hoc IEEE 802.11b wireless network based on testbed experiments. The influence of contention and RTS/CTS are investigated. Through capturing and analyzing all the on-the-fly IEEE 802.11b packets, we will compare and report our experiment results.

Xiaoyan Hong

Papers

Handshake time and transmission rate of 802.11g measurement in vehicular networks

ProtoGENI, a Prototype GENI Under Security Vulnerabilities: An Experiment-Based Security Study

A reconfigurable hardware platform for cognitive sensor networks towards behavioral biometrics

Delay management in delay-tolerant networks

Single-hop and multi-hop delay characteristics of ad-hoc 802.11b wireless network