1. 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

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

3. 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

4. What is information

5. Logical components of network
Communication network
node
link
station

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

7. 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.

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

9. 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

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

11. 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）

12. Relation between Frequency and Period
t = 1/f

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

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

15. Time Domain and Frequency Domain

16. Time and Frequency Domain Including DC

17. Complicated Wave Forms

18. Frequency Spectra of Periodic and Non-Periodic Signals

19. 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

20. 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

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

22. 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)

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

24. 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)

25. 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.

26. Information and Transmission Rate
TV phone
HDTV
TV conference
Fax
Telephone

27. Signal Distortion

28. Analog and Digital Signal Transmission

29. 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

30. 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.

31. 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.

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