Data Communication and Media • Concept and Model of Communications • Analogy Signal and Digital Signal • Signal Frequency, Spectrum and Bandwidth • System Frequency Response and Bandwidth • Transmission Media and Types • Transmission Modes - Parallel & Serial Transmission - Asynchronous & Synchronous Transmissions - Simplex & Duplex Transmission • Communication Standards: RS/EIA-232 & Others Lecture 1
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Data Communication and Media Concept and Model of Communications Analogy Signal and Digital Signal Signal Frequency, Spectrum and Bandwidth System Frequency.
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Data Communication and Media
Data Communication and Media
• Concept and Model of Communications• Analogy Signal and Digital Signal• Signal Frequency, Spectrum and Bandwidth• System Frequency Response and Bandwidth• Transmission Media and Types• Transmission Modes - Parallel & Serial Transmission - Asynchronous & Synchronous Transmissions - Simplex & Duplex Transmission• Communication Standards: RS/EIA-232 &
Others
• Concept and Model of Communications• Analogy Signal and Digital Signal• Signal Frequency, Spectrum and Bandwidth• System Frequency Response and Bandwidth• Transmission Media and Types• Transmission Modes - Parallel & Serial Transmission - Asynchronous & Synchronous Transmissions - Simplex & Duplex Transmission• Communication Standards: RS/EIA-232 &
Others
Lecture 1
General Communications: face-to-face conversation, write a letter, etc.
Electronic Communications: telephone, wireless phone, TV, radar, etc.
Lecture 1
Concept and Model of CommunicationsConcept and Model of Communications
Our Focus Computer Communication
General Communication Model
Source TransmitterTransmission
SystemReceiver Destination
S(t) T(t) Tr(t) Sd(t)
MicrophoneTelephoneComputerScanner
TransformerEncoderCompressModulator
Line/CableFiber/AirSatelliteNetwork
TransformerDecoderUncompressDemodulator
SpeakerEarphoneComputerPrinter
Basic Communication Criteria: Speed, Reliability, Security (SRS)
Information must be converted into electrical energy, called signal, before transmission.
Text, voiceVideo, etc
Lecture 1
Analogy Signal and Digital SignalAnalogy Signal and Digital Signal
System Frequency Response & BandwidthSystem Frequency Response & Bandwidth
System: H()Input Signal x(t)
Output Signal y(t) =H[x(t)]
Input Spectrum: X(f)
Output Spectrum: Y(f)
System Frequency Response: H(f) = Y(f)/X(f)
f
H(f)
System Bandwidth B = F2 – F1
Signal can passSignal can’t pass
F1 F2
TransmissionBandwidth
Lecture 1
Transmission MediaTransmission Media
A transmission medium: - a connection between a sender and a receiver - a signal can pass but with attenuation/distortion - a special system with a transmission bandwidth
Simplex Transmission and Duplex TransmissionSimplex Transmission and Duplex Transmission
Device A Device BSimplexTransmission
Direction of data
Device A Device BHalf DuplexTransmission
Direction of data at time 1
Device A Device BFull DuplexTransmission
Direction of data all the time
Direction of data at time 2
One can send and the other can receive
Both can send and receive but in different time
Both can send and receive simultaneously
複信 - Wikipedia
Lecture 1
Communication Standards and Related OrganizationsCommunication Standards and Related Organizations
Communications need standards for inter-operations of different devices
Standard Organizations: - ISO (International Standards Organization): ISO number - ITU (International Telecommunication Union): V.num & X.num - EIA (Electronic Industries Association): EIA-num - IEEE (Institute of Electronics Engineers): IEEE.num - ANSI (American National Standards Institute): ASCII, etc. - ATM Forum and ATM Consortium - IETF (Internet Society and Internet Engineering Task Force): RFC num - W3C (World Wide Web Consortium): HTTP, HTML, XML, … - WAP Forum (Wireless Application Protocol): WAP-num
Lecture 1
Serial & Asynchronous Transmission StandardsSerial & Asynchronous Transmission Standards
Standards of transmission in short distance: - EIA-232 or RS-232 - V.24 - ISO 2110 - EIA-449/RS-422/RS-423 - EIA-530 - X.21
Their common features - Serial & asynchronous transmission - Transmissions of ASCII code, byte, char - Use twisted copper lines - Low speed: several Kbits ~ Mbits per second - Short distance: < several tens of meters
Lecture 1
EIA/RS-232 StandardEIA/RS-232 Standard
Device ASender
Device BReceiver
• Transmit characters (7 or 8 bits)• Sender: 0 +15v and 1 -15v • Start bit (0) and stop bit (1) for every character 9/10 bits in total• A sender never leaves wire at 0v; when idle, puts –15v, i.e., 1• Receiver: 0 (+3v, +15v) and 1 (-3v, -15v), otherwise error
Wave form of ‘+’, 2B or 0101101bit 0
RS-232, Wikipedia
Lecture 1
EIA/RS-232 Standard (cont.)EIA/RS-232 Standard (cont.)
• Agreement of transmission timing or rate/speed bps bits per second, bit rate or transmission speed - 300bps, 2.4Kbps, 4.8Kbps, …, 19.2Kbps, 33.6Kbps, 56Kbps• Setting bit rate (transmission speed) of devices/hardware - switch (manually), software, auto-detection• Either simplex or duplex
T: Transmitter R: Receiver G: Ground
Lecture 1
EIA/RS-232 and Other StandardsEIA/RS-232 and Other Standards
1. Two signals are given in the following figures. Whose bandwidth is large? Why?
t
s(t)
(a) (b)
2. Draw the RS-232 waveform diagrams of ASCII letters of R (1010010) and S (1110011).
3. Give at least one example for each of the following transmission/communication modes: parallel transmission, serial transmission, simplex transmission and duplex transmission.
4. Suppose one sent 10000 7bit characters across an EIA-232 or RS-232 connection that operated at 9600 bps (9.6Kbps). How long will the minimum transmission time be required? (Hint: remember to add a start bit and a stop bit on each character.)