Modeling and Validation of Processor Deallocation Time in Hypercube Systems

Moh, Sangman 朝鮮大學校 電子情報通信硏究所 2003 電子情報通信硏究所論文誌 Vol.6 No.2

In parallel computer systems, job scheduling and processor allocation strategies are crucial in viewpoint of resource management, hence performance modeling and evaluation as well as the design of efficient algorithms have been studied actively since the advent of such systems. In this paper, we present the modeling and validation of processor deallocation time in hypercube systems. The processor deallocation time △_(x)(k), which is defined as the average time required for k busy processors are to become free out of (2ⁿ - x) busy processors when x processors are free in an n-cube system, has been simply modeled and then validated by simulating the scheduling and allocation behavior of a 6-cube system. According to our comparative evaluation of simulation and analysis results, the derived model is matched with the simulation results.

Adaptive multicast on mobile ad hoc networks using tree-based meshes with variable density of redundant paths

Moh, Sangman,Lee, Sang Jun,Yu, Chansu Springer-Verlag 2009 WIRELESS NETWORKS Vol.15 No.8

A Cooperative Diversity-Based Robust MAC Protocol in Wireless Ad Hoc Networks

Sangman Moh,Chansu Yu IEEE 2011 IEEE transactions on parallel and distributed syst Vol.22 No.3

<P>In interference-rich and noisy environment, wireless communication is often hampered by unreliable communication links. Recently, there has been active research on cooperative communication that improves the communication reliability by having a collection of radio terminals transmit signals in a cooperative way. This paper proposes a medium access control (MAC) algorithm, called Cooperative Diversity MAC (CD-MAC), which exploits the cooperative communication capability of the physical (PHY) layer to improve robustness in wireless ad hoc networks. In CD-MAC, each terminal proactively selects a partner for cooperation and lets it transmit simultaneously so that this mitigates interference from nearby terminals, and thus, improves the network performance. For practicability, CD-MAC is designed based on the widely adopted IEEE 802.11 MAC. For accurate evaluation, this study presents and uses a realistic reception model by taking bit error rate (BER), derived from Intersil HFA3861B radio hardware, and the corresponding frame error rate (FER) into consideration. System-level simulation study shows that CD-MAC significantly outperforms the original IEEE 802.11 MAC in terms of packet delivery ratio and end-to-end delay.</P>

Adjacency-Based Mapping of Mesh Processes for Switch-Based Cluster Systems of Irregular Topology

모상만(Sangman Moh) 大韓電子工學會 2010 電子工學會論文誌-CI (Computer and Information) Vol.47 No.2

가상의 프로세스 토폴로지를 물리적인 프로세서 토폴로지로 매핑하는 문제는 병렬 프로그래밍에서 가장 중요한 이슈 중의 하나이다. 그러나 이 매핑은 토폴로지 비규칙성 및 라우팅 복잡성으로 인해 어려운 문제로 여겨지고 있다. 본 논문에서는 프로세스간 통신 패턴으로 2차원 메쉬 프로세스 토폴로지를 가정하여, 비규칙 클러스터 시스템을 위한 새로운 프로세스 매핑 기법인 인접 기반 매핑(AM)을 제안한다. 클러스터 시스템은 전통적인 규칙성 네트워크에서는 달성하기 어려운 상호연결 유연성과 시스템 확장성을 제공하기 때문에 여러 해 동안 활발히 연구 개발되어 오고 있다. 제안한 AM은 가상 프로세스 토폴로지에서 이웃하는 프로세스를 물리적인 프로세서 토폴로지의 인접한 프로세서에게 매핑시킨다. 시뮬레이션 결과에 따르면, 제안한 AM 은 기존 방법에 비하여 매핑 품질이 우수하고 프로세스간 지연시간이 감소하는 결과를 나타낸다. Mapping virtual process topology to physical processor topology is one of the most important design issues in parallel programming. However, the mapping problem is complicated due to the topology irregularity and routing complexity. This paper proposes a new process mapping scheme called adjacency-based mapping (AM) for irregular cluster systems assuming that the two-dimensional mesh process topology is specified as an interprocess communication pattern. The cluster systems have been studied and developed for many years since they provide high interconnection flexibility, scalability, and expandability which are not attainable in traditional regular networks. The proposed AM tries to map neighboring processes in virtual process topology to adjacent processors in physical processor topology. Simulation study shows that the proposed AM results in better mapping quality and shorter interprocess latency compared to the conventional approaches.

MAC Protocols for Ad Hoc Networks with Directional Antennas

Bipula Khatiwada,Sangman Moh 한국통신학회 2011 정보와 통신 Vol.28 No.12

In recent years, the employment of directional antennas in ad hoc networks has significantly increased. MAC protocols for ad hoc networks with directional antennas have the potentiality of spatial reuse, large coverage range and network capacity, which mitigates the negative effects associated with omnidirectional antenna systems. However, they suffer from some issues such as hidden terminal problems, deafness, neighbor discovery, flaws with directional carrier sensing, etc. In this paper, we have surveyed the MAC protocols for ad hoc networks with directional antennas, which have been published in the literature, and compared them qualitatively in terms of major characteristics and network performances.

Identity-Based Key Agreement Protocol Employing a Symmetric Balanced Incomplete Block Design

Shen, Jian,Moh, Sangman,Chung, Ilyong The Korea Institute of Information and Commucation 2012 Journal of communications and networks Vol.14 No.6

Key agreement protocol is a fundamental protocol in cryptography whereby two or more participants can agree on a common conference key in order to communicate securely among themselves. In this situation, the participants can securely send and receive messages with each other. An adversary not having access to the conference key will not be able to decrypt the messages. In this paper, we propose a novel identity-based authenticated multi user key agreement protocol employing a symmetric balanced incomplete block design. Our protocol is built on elliptic curve cryptography and takes advantage of a kind of bilinear map called Weil pairing. The protocol presented can provide an identification (ID)-based authentication service and resist different key attacks. Furthermore, our protocol is efficient and needs only two rounds for generating a common conference key. It is worth noting that the communication cost for generating a conference key in our protocol is only O($\sqrt{n}$) and the computation cost is only O($nm^2$), where $n$ implies the number of participants and m denotes the extension degree of the finite field $F_{p^m}$. In addition, in order to resist the different key attack from malicious participants, our protocol can be further extended to provide the fault tolerant property.

Comparative Analysis on Localization in Wireless Sensor Networks

Jian Shen,Sangman Moh,Ilyomg Chung 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7

As a novel technology for acquiring and processing information, wireless sensor networks (WSNs) have been studied and developed for a multitude of diverse applications. The problem of self-localization, that is, determining where a given node is physically or relatively located in a network, is a challenging issue, and yet extremely crucial for many applications in WSNs. In this paper, the evaluation criteria, taxonomy and algorithms of self-localization systems designed for WSNs are extensively surveyed. The principles and characteristics of representative localization schemes are discussed with comparison. The directions of research in this area are also introduced.

Comparisons of MAC Protocols for Ad Hoc Networks with Directional Antennas

Bipula Khatiwada,Sangman Moh 대한전자공학회 2009 ITC-CSCC :International Technical Conference on Ci Vol.2009 No.7

MAC protocols in ad hoc networks with directional antennas have the potentiality of spatial reuse, larger coverage range and network capacity, which mitigates the limitations associated with omnidirectional antenna systems. However, these MAC protocols also suffer from some issues such as hidden terminal problem, deafness, neighbor discovery, flaws with directional carrier sensing, etc. In this paper, we survey MAC protocols for ad hoc networks with directional antennas and compare them in terms of major characteristics and network performance.

A Survey on Smart Dust Motes for Wireless Sensor Networks

Xin Su,Sangman Moh,Ilyong Chung 한국멀티미디어학회 2009 한국멀티미디어학회 학술발표논문집 Vol.2009 No.1

A sensor network consists of a large number of sensing devices capable of detecting waves of sound, heat, magnetism and so on. Each sensing device needs to collaborate with its neighboring devices to perform a given task by disseminating data through the network. We call these devices Smart dust Motes, which an attractive architecture for sensor networks is to have each sensing device mounted on a small computer. They have characteristics including low-power consumption, small size, and flexibility. Smart dust motes are battery-powered, and can communicate in a wireless fashion by broadcasting messages over radio frequency. They are energy constrained and range of their radio transmission is limited to their neighborhood. So, they form a multi-hop network to deliver information packets. In this paper, we survey different kinds of modem smart dust motes and give briefly specification by using a comparative table.

Routing Protocols in Underwater Sensor Networks : A Comparative Survey

Jian Shen,Sangman Moh,Ilyong Chung 한국멀티미디어학회 2008 한국멀티미디어학회 학술발표논문집 Vol.2008 No.2

Underwater sensor networks (UWSNs) are a class of emerging networks that experience variable and high propagation delays and limited available bandwidth. There are comprehensive applications in this area which are envisioned to enable applications for oceanographic data collection, pollution monitoring, offshore exploration, disaster prevention, assisted navigation and tactical surveillance applications. Hence, UWSNs has great potential and contains enormous values in economic and social field. Because of the different environment under the ocean, obviously, the whole protocol stack should be re-designed to fit for the surroundings. In this paper, however, we only focus on the routing protocols in the network layer. We survey the state-of-the-art routing protocols and give a comparison of them with respect to the important challenging issues in UWSNs. The routing protocols are classified into three categories: proactive, reactive and geographical routing protocols. The pros and cons as well as performance are discussed and compared for the routing protocols. Especially, we give a comparison study about the localization schemes in geographic routing protocols.