Prof. Noriyoshi Yamauchi April 17, 2008 センサネットワーク Sensor Networks 担当：山内規義 教授 Prof. Noriyoshi Yamauchi

April 14, 2007 History of telecommunications Basics of telecommunications Information Networks Communication Data Analog vs. digital Digital signal Encode, decode

Class schedule (tentative) 4/10 Orientation, Introduction 4/17 Basics of telecommunications (1) 4/24 Basics of telecommunications (2) 5/1 Basics of wireless communications 5/8 International standards of wireless communications 5/15 protocols 5/22 ZigBee 5/29 Blue Tooth 6/5 Applications of WSN (1) 6/12 Future trends of WSN (2) 6/19 Applications of WSN to automobiles 6/26

What is information

Logical components of network Communication network node link station

What is network A a wide variety of systems of interconnected components typically, computers.

What is communication Communication is the process of exchanging information usually via a common system of symbols. Telecommunication is the extension of communication over a distance. In practice it also recognizes that something may be lost in the process; hence the term 'telecommunication' covers all forms of distance and/or conversion of the original communications, including radio, telegraphy, television, telephony, data communication and computer networking.

What is data Expression of information using a certain format. Container of information Datum (singular単数) Data (plural複数)

Analog Signal and Digital Signal Voltage Voltage Digital signal： 離散的な時間に対し，離散的な値 しかとらない信号．一般に”0”と“1” の2値で表される． Discrete value for discrete time. Usually expressed using 0 and 1 Analog signal: 振幅が時間とともに連続 的に変化する信号 Continuous change with time

Periodic Signal and Aperiodic Signal f(x)=f(x+T) T：period

Sine Wave y=sin T 2p t ( ) t:時間（秒） Amplitude Maximum value Time Period Minimum value y=sin T 2p t ( ) t:時間（秒）

Relation between Frequency and Period t = 1/f

Sine Wave with Different Phase Amplitude Time 2p ( + f) y=sin t f:位相(phase) T

Changes of Amplitude, Frequency and Phase Amplitude change Frequency change Phase change

Time Domain and Frequency Domain

Time and Frequency Domain Including DC

Complicated Wave Forms

Frequency Spectra of Periodic and Non-Periodic Signals

Frequency Spectrum 信号に含まれる周波数成分がどのくらいある かを表したグラフ

Bandwidth（周波数帯域） 周波数帯域：信号が含む周波数の範囲（何Hzから何Hzまで） 帯域幅：周波数スペクトルの幅 Amplitude Frequency 周波数帯域：信号が含む周波数の範囲（何Hzから何Hzまで） 帯域幅：周波数スペクトルの幅 Bandwidth: f1 – f2

Digital Signal bit　“1”または“0” 1 bit 0.5 bits 8 bits = 1 Byte

Transmission Speed（ビットレート，bit rate） 1秒間に伝送できるビット数のこと The number of bits transmitted in 1 sec Unit: bps (bit per second)

Transmission Speed Unit：bit per second bps In this case, the bit rate is 8 bps

Bandwidth アナログ信号の場合： 周波数スペクトルの幅のこと，Hzを単位とする In analog signal: f1 – f2 (Hz) ディジタル信号の場合： 信号の伝送速度のこと，bpsを単位とする In digital signal: Transmission speed (bps)

Transmission Speed and Frequency Spectra 伝送速度を早くすればするほど，信号の伝送にはよ り広い周波数帯域幅が必要になる． The faster the bit rate, the wider bandwidth we need.

Information and Transmission Rate TV phone HDTV TV conference Fax Telephone

Signal Distortion

Analog and Digital Signal Transmission

通信容量（Channel Capacity） ある通信路を通過できる最大の伝送速度 のこと The maximum bit rate allowed in the Transmission medium

符号化（エンコード，Encode） 情報を伝送路に適した形式の信号に変換する こと To transform the information to signal which fits the transmission media.

復号化（デコード，Decode） 符号化された信号を元の情報に変換すること To return the signal to the original Information.

Signal Transmission Information Signal Signal Information Encode Decode Receiver Recipient Transmitter Information source Noise