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行動計算與網路簡介Introduction to Mobile Computing a

nd Networking

王國禎國立交通大學資訊科學系

行動計算與寬頻網路實驗室http://pds.cis.nctu.edu.tw

Email: kwang@cis.nctu.edu.tw

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大綱• 行動計算與網路發展背景• 無線通信本質• 電腦的行動性• 無線網路技術• 行動式電腦技術• 研究主題• 結論

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行動計算與網路發展背景• 無線數位通信技術快速發展

• 通信及行動電腦成本降低– 行動計算應用由業者推廣至一般消費者

• 目標：無遠弗屆

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無線通信的本質• 頻寬窄及變動大

• 高位元錯誤率 (BER)

• 電池蓄電的限制

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電腦的行動性• 新研究課題：對網路、作業系統及資訊

系統的影響– 網路及通信主題– 位置管理：位置不固定 (Mobile IP)– 應用軟體：位置相關性 (Locati

on-dependent applications)– 主從架構 (on-demand) 與出版式架構

(publishing)

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無線與有線環境的最大差異

• 單一頻寬為所有使用者共享• 無干擾的情況下，同頻道 (channels)

可以再用• cells → microcells → picocells

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Hierarchical Cell Structure (HCS)

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無線網路技術• Analog cellular systems

• Digital cellular systems

• Cordless telephony

• Wireless LANs

• Private wireless data networks and metropolitan area wireless networks

• Satellite networks

• Future PCS (IMT-2000)

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IMT-2000 的目標

• Expanded range of services

• A unified, seamless infrastructure

• Integration of mobile and fixed networks

• Bridge the telecommunication gap

• Broadband transport

• Self-adaptive, reprogrammable terminals

• Virtual home environment

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IMT-2000 的系統規格

• Hierarchical cell structure

• Globe roaming– Terminal mobility– Personal mobility– Service provider portability (via

software radio)

• Expanding radio spectrum

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Major Difference between cdma2000 and WCDMA (1)• Duplex and multiple access scheme– cdma2000: Frequency Division Duplex

Multi-Carrier CDMA (FDD MC-CDMA)–WCDMA: Frequency Division Duplex

Direct-Sequence CDMA (FDD DS-CDMA)• Chip rate– cdma2000: 3.6864Mcps–WCDMA: 3.84Mcps

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Major Difference between cdma2000 and WCDMA (2)• Forward link pilot for channel estimation– cdma2000: CDM common pilot channel–WCDMA: Common pilot channel or TDM

dedicated pilot channel• Antenna beam forming and spot beams– cdma2000: Auxiliary pilot channel–WCDMA: TDM dedicated pilot channel

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Major Difference between cdma2000 and WCDMA (3)• Base station synchronization– cdma2000: Synchronous– WCDMA: Asynchronous

• Base station acquisition and detection– cdma2000: Synchronization through time

shifted PN correlation– WCDMA: 3 step parallel code search for base

station detection and slot/frame

• Network Signaling Support– cdma2000: IS-41,GSM-MAP– WCDMA: GSM-MAP

Next generation network service portability

Frequency allocation

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GPRS• GPRS is an extension of existing

GSM bearer services

• Enlarge the data rate from 9.6 kb/s to 170 kb/s

• Uses packet-switch instead of circuit -switch

• GPRS is well suited to replace SMS, or may be as an SMS bearer

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第三代行動電話• 寬頻高速傳輸– 顯示即時新聞– 傳遞數位影像

• 連接網際網路– 瀏覽首頁– 收發電子郵件– 執行電子商務

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第三代行動網路應用

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即時影像與電子商務

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行動式電腦技術

• 電池壽命增長： doze mode

• 儲存技術： flash memory v.s. disks

• 使用者介面： pen-based

• 顯示技術： small-size

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高能源效率軟體之設計

• CPU scheduling for low power

• New communication protocols

• Energy-aware application designs

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研究主題• Mobile networking (DL, NL, TL)• Information services (mobile wireless clients

information resources on the fixed networks)

• Power management (at the software level as well as at the hardware level)

• System issues in mobile computing (key issues: the issues of disconnection)– affects file system and database design

• Research prototypes

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行動計算之主要研究挑戰• Mobility (registration vs. searching)

• Variable communication conditions– fading– noise– interference

• Energy limitations

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行動計算與行動通信• Mobile communications involve– Physical layer: IR, radio–MAC layer: CSMA/CA, FDMA, TDMA,

CDMA, W-CDMA

• Mobile computing involves–Mobile networking (DL, NL, TL)– Software applications (AL)

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IEEE 802.11 vs. HomeRF

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Bluetooth• Major joint computing and telecomm

industry initiative

• Plan to deliver a revolutionary radio-based solution– Cable replacement, no line of sight

restrictions– Prefect for mobile devices - small, low

power, low cost– Open specification(license free)

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應用層設計主題• Application layer–WAP (Wireless Application Protocol)– I-mode (NTT DoCoMo)– Context-sensitive applications

• Ubiquitous multimedia mobile computing

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•Scroll through the menu of the phone: Services, Bookmarks, PDS.

•Select PDS. You can change the language if you wish.

•Give your PDS codes.

• First you will see the available subscription services menu: Movie, Train, Airplane, Hotel, Restaurant.•For example: Select Hotel

•Select the location of the hotel.

•Select the hotel you are interesting.

•Select the kind of room you want and the check in day.

•Send.

•You will receive a confirmation message.

PDS Entertainment Subscription Services

PDS

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I-mode• 由 NTT DoCoMo 在 99 年 2 月推出之服務• 封閉的 PDC 系統 : 技術比 GSM 所提出的

WAP 還要優越• 提供一千兩百多個網站 , 內容可分為 :– 生活資訊 : 新聞、氣象– 金融服務 : 轉帳、查詢– 定票服務 : 機票、火車票、餐廳訂位– 線上訂貨 : 超市、百貨

• 與美軍合作 , 開發軍用 JINI 無線網際網路語言

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結論• Ubiquitous (seamless) multimedia

mobile computing and networking

• Providing right information at any time, any place, any terminal

• Context-sensitive applications

• Wearable computing

• Personal web

• Global village