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April 14, 2007 History of telecommunications Basics of telecommunications Information Networks Communication Data Analog vs. digital Digital signal Encode, decode
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センサネットワークSensor Networks
担当:山内規義 教授Prof. Noriyoshi Yamauchi
April 17, 2008
April 14, 2007History of telecommunications
Basics of telecommunications-Information-Networks-Communication-Data-Analog vs. digital-Digital signal-Encode, decode
Class schedule (tentative)4/10 Orientation, Introduction4/17 Basics of telecommunications (1)4/24 Basics of telecommunications (2) 5/1 Basics of wireless communications5/8 International standards of wireless communications5/15 protocols5/22 ZigBee5/29 Blue Tooth6/5 Applications of WSN (1)6/12 Future trends of WSN (2)6/19 Applications of WSN to automobiles6/26
What is information
Communication network
Logical components of network
node
station
link
What is network
A a wide variety of systems of interconnected componentstypically, computers.
What is communicationCommunication 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 certainformat.
Container of information
Datum (singular単数 )
Data (plural複数 )
Analog Signal and Digital Signal
Analog signal:振幅が時間とともに連続的に変化する信号Continuous change withtime
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
Voltage Voltage
Periodic Signal and Aperiodic Signal
f(x)=f(x+T)
T : period
Periodic Aperiodic
Sine Wave
y=sin T2 t( ) t:時間(秒)
AmplitudeMaximum value
Minimum value
Time
Period
Relation between Frequency and Period
Frequency Period
t = 1/f
Sine Wave with Different Phase
y=sin T2 t( + ) :位相 (phase)
Amplitude
Time
Changes of Amplitude, Frequency and Phase
Amplitude change Frequency change
Phase change
Time Domain and Frequency Domain
Time domain 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Bandwidth: f1 – f2
Amplitude
Frequency
Digital Signal
bit “ 1” または“ 0”1 bit
0.5 bits8 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 bpsIn 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
Telephone
Fax
TV phone
TV conferenceHDTV
Signal Distortion
Analog and Digital Signal TransmissionAnalog
Digital
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 theTransmission 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 whichfits 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 TransmissionInformation Signal Signal Information
Encode Decode
Information source
Noise
Transmitter Receiver Recipient