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Routing for Wireless Sensor Routing for Wireless Sensor NetworkNetwork

行動通訊系統專題報告

教授 : 林振緯

班級 : 研一

報告人 : 郭彥蔚 , 黃皓祺

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AbstractAbstract Wireless Sensor Network(WSN) 是目前研究領

域的重要課題，這裡面包含了許多相關的研究方向。– Physical layer protocols and related issues– Routing protocols and data communications– System Reliability and Fault Tolerance– Target Detection, Classification and Tracking with

Sensor Networks – Data Fusion and Data Management– TCP over Wireless Networks– Other

傳統 ad hoc 路由協定為何不適用於 WSN WSN 路由協定所要解決的問題及方法

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AgendaAgendaWhat’s Wireless Sensor NetworkWSN vs MANETWireless Sensor Network Architecture Communication and Data Delivery ModelRouting ProtocolConclusionQ&A

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GlossaryGlossaryWSN – Wireless Sensor NetworkMANET – Mobile Ad-hoc NetworkMEMS – Micro Electro Mechanical Syste

ms

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What’s Wireless Sensor NetworkWhat’s Wireless Sensor Network

IntroductionFeatures of sensor networksWireless Sensor Networks Application

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IntroductionIntroduction

The development of low-cost, low-power, multifunctional sensor networks is due to advancement in wireless communications and electronics

The tiny sensor nodes consist of sensing, data processing, and communicating components

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Introduction (cont.)Introduction (cont.)

A sensor network is composed of a large number of sensor nodes that are densely deployed either inside the phenomenon or very close to it

The position of sensor nodes need not be engineered or predetermined

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Features of sensor networksFeatures of sensor networks

Sensors can be random deployment in inaccessible terrains; sensor network protocols and algorithms must possess self-organizing capabilities

Sensor networks require the cooperative effort of sensor nodes

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Features of sensor networks Features of sensor networks (cont.)(cont.)Instead of sending the raw data to the

nodes responsible for the fusion, sensor nodes use their processing abilities to locally carry out simple computations and transmit only the required and partially processed data

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Wireless Sensor Networks Wireless Sensor Networks ApplicationApplicationA wide range of application areas of sensor

networks are health, military, and home In military, the rapid deployment, self-

organization, and fault tolerance characteristics of sensor networks make them a very promising sensing techniques for military command, control, communication, computing, intelligence, surveillance, reconnaissance, and targeting systems

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Wireless Sensor Networks Wireless Sensor Networks Application (cont.)Application (cont.)In health, sensor nodes can also be

deployed to monitor patients and assist disabled patients

Commercial applications: managing inventory, monitoring product quality, and monitoring disaster areas

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WSN vs MANETWSN vs MANET

The differences between sensor networks and ad hoc networks are：– The number of sensor nodes are several orders

of magnitude higher– Sensor nodes are densely deployed– Sensor nodes are prone to failures– The topology of a sensor network changes

very frequently

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WSN vs MANET (cont.)WSN vs MANET (cont.)

Sensor nodes mainly use a broadcast communication paradigm whereas most ad hoc networks are based on point-to-point communications

Sensor nodes are limited in power, computational capacities, and memory

Sensor nodes may not have global identification (ID) because of the large amount of overhead and large number sensors

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WSN vs MANET (cont.)WSN vs MANET (cont.)  WSN MANET

節點數量 通常裝置的數量龐大 網路內的裝置數量有限

節點密度 密集 鬆散

節點故障率

很高 低

網路拓樸 變動頻率很高 變動頻率高但較 WSN 低

通訊方式 廣播 點對點

裝置硬體 電源、記憶體、計算能力有限

電源、記憶體、計算能力較好

識別方式 沒有特定的識別碼 有特定的識別碼

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Wireless Sensor Network Wireless Sensor Network ArchitectureArchitectureHardwareSoftwareWireless Sensor Network Design Factors

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Hardware ArchitectureHardware Architecture

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Hardware Architecture (cont.)Hardware Architecture (cont.)

Sensing Unit– The analog signals produced by the sensors based on

the observed phenomenon are converted to digital signals by the ADC, and then fed into the processing unit

Processing Unit– Sensor nodes use their processing abilities to locally

carry out simple computations and transmit only the required and partially processed data

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Hardware Architecture (cont.)Hardware Architecture (cont.)

Transceiver Unit– A transceiver connects the node to the

networkPower Unit

– Power unit may be supported by power scavenging units such solar cells

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SoftwareSoftware

Tiny OS– 無線感測網路 (Sensor Network) 上的每個點

都是一個小型電腦，都具備有通訊網路的功能，其上面的作業系統稱為 Tiny OS ，顧名思義是個極小的嵌入式作業系統。

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Wireless Sensor Network Design Wireless Sensor Network Design FactorsFactorsFault Tolerance

– the ability to sustain sensor network functionalities without any interruption due to sensor node failures

Scalability – The number of sensor nodes deployed in

studying a phenomenon may be on the order of hundreds or thousands Sensor Costs

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Wireless Sensor Network Design Wireless Sensor Network Design Factors (cont.)Factors (cont.)Production costs

– The cost of a sensor node should be much less than US$1 in order for the sensor network to be feasible

Hardware Constraints– A sensor node is made up of 4 basic

components a sensing unit, a processing unit, a transceiver unit, and a power unit

– Use MEMS technique

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Wireless Sensor Network Design Wireless Sensor Network Design Factors (cont.)Factors (cont.) Sensor Network Topology

– Planning and Deployment Phase 感測器的部署可以事先精心規劃，再依據所規劃的藍圖佈署感

測器。– Post-Deployment Phase

在感測器部署完成後，就已經形成一個完整的無線網路架構，但是感測器的位置容易受到環境因素，造成網路拓樸的改變；這時候，系統就必須對拓樸的改變做出即時反應，並迅速對殘缺的網路拓樸做出修正。

– Redeployment of Additional Phase 在經過一段時間後，許多感測器可能由於電力嚴重不足或是損

壞的緣故，造成整個感測網路中，可以偵測環境以及傳輸資料的節點個數不足。必須依靠外力 ( 人員、機械等 ) 在這個網路中新增一些額外的感測器，以彌補感測器數量不足的問題。

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Wireless Sensor Network Design Wireless Sensor Network Design Factors (cont.)Factors (cont.)

Environment – Sensors can be random deployment in

inaccessible terrains; sensor network protocols and algorithms must possess self-organizing capabilities

Transmission Media Power Consumption

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Communication and Data Delivery Communication and Data Delivery Model Model

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Communication and Data Delivery Communication and Data Delivery Model (Cont.)Model (Cont.)

Communication Model– Application– Infrastructure

Data Delivery Model– Application Layer

Continuous Even-Driven Observer-Initiated Hybrid

– Physical Layer Flooding, unicast, multicast

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Communication ModelCommunication Model

Application– 應用通訊主要是將所偵測到的資料及數

據傳送回基地台 , 因此通訊模式大多是點對點 (end-to-end) 的型態

– 此架構對資料的蒐集又可分為Cooperative

– Data fusion or Data Aggregation

Non-Cooperative

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Communication Model (cont.)Communication Model (cont.)

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Communication Model (cont.)Communication Model (cont.)

Infrastructure– 基礎建置通訊主要運用在感測器網路需

要 configure 、 maintain 、 optimize 網路時– 此架構依照任務需求 , 以不同的演算法進行

調整

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Data Delivery ModelData Delivery Model

Continuous– 資料以固定間隔持續的送至基地台

Even-Driven– 事件發生時 , 資料才送回基地台

Observer-Initiated– 由觀測者送出指令或需求時 , 資料才送回基地台

Hybrid– 上述三種型態都有的混合型

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Data Delivery Model (cont.)Data Delivery Model (cont.)

Flooding– 來源端傳送資料給所有的鄰居 , 一直到資料

抵達目的端

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Data Delivery Model (cont.)Data Delivery Model (cont.)

Unicast– 資料傳送至單一節點 , 可能為路由路徑的下

一節點或基地台Multicast

– 鄰近的感測器依需求建立群組 , 資料傳送可直接傳送給群組的各個成員

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Routing ProtocolRouting Protocol

The networking layer of sensor networks is usually designed according to the following principles:– Power efficiency

– Sensor networks are mostly data centric

– Data aggregation is useful only when it does not hinder the collaborative effort of the sensor nodes

– An ideal sensor network has attribute-base addressing and location awareness

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Power efficiencyPower efficiency

An energy-efficient route is selected by one of the following approaches:– Maxmum PA route– Minimum Energy (ME) route– Minimum Hop (MH) route– Maximum minimum PA node route

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Maximum PA routeMaximum PA route

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Minimum Energy (ME) routeMinimum Energy (ME) route

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Minimum Hop (MH) routeMinimum Hop (MH) route

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Maximum Minimum PA node Maximum Minimum PA node routeroute

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Routing Protocol (cont.)Routing Protocol (cont.)

Network Layer– SMECN– Flooding– Gossiping– SPIN– SAR– LEACH– Directed Diffusion

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Routing Protocol (cont.)Routing Protocol (cont.)

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Routing Protocol (cont.)Routing Protocol (cont.)

Transport Layer– Protocol are still unexplored– They may be purely UDP-type protocols, beca

use each sensor node has limited memory and power

Application Layer– SMP– TADAP– SQDDP

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ConclusionConclusion

Many researchers are currently engaged in developing the technologies needed for different layers of the sensor networks protocol stack

A list of current sensor network research projects shown in reference Table 3.

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ReferenceReference

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ReferenceReference Ian F. Akyildiz, Weilian Su, Yogesh Sankarasubramaniam, and

Erdal Cayirci @ GaTech A Survey on Sensor Networks IEEE Communications Magazine, 2002

S. Tilak, N. Abu-Ghazaleh, and W. Heinzelman @ Binghamton & RochesterA Taxonomy of Wireless Micro-Sensor Network Models. ACM Mobile Computing and Communications Review (MC2R), Volume 6, Number 2, April 2002

Holger Karl and Andreas WilligA Short Survey of Wireless Sensor Networks. TKN Technical Report TKN-03-018, October 2003

Deborah Estrin, Ramesh Govindan, John Heidemann and Satish Kumar @ USC/ISINext Century Challenges: Scalable Coordination in Sensor Networks.  In Proc. of the fifth Annual ACM International Conference on Mobile Computing and Networking, 1999, Seattle, Washington, USA