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 - 法政大学 情報科学部cis.k.hosei.ac.jp/~jianhua/course/com/Lecture1.pdf · Data Communication and Media ... Analogy Signal and Digital Signal
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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 Response and Bandwidth• Transmission Media and Types• Transmission Modes
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 BandwidthB = F2 – F1
Signal can pass
Signal can’t pass
F1 F2
TransmissionBandwidth
Lecture 1
Transmission 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
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 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 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
• 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 Standards
• EIA-232: rate<64Kbps; connection length< 15 meters; 25 pin connector- pin 2: receive (RxD); pin 3: transmit (TxD); pin 7: groud- other pins for transmission control
• EIA-449: rate<10Mbps; connection length< 12 meters; 37/9 pin connector• EIA-530: same as the above; 25 pin connector• X.21: 64/192 Kbps (N-ISDN rate); 15/8 pin connector RS-232 - ウィキペディア
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.)