modem
Download
Skip this Video
Download Presentation
Modem

Loading in 2 Seconds...

play fullscreen
1 / 14

Modem - PowerPoint PPT Presentation


  • 212 Views
  • Uploaded on

Modem. Modem connection. PC. PC. modem. modem. 110011. 110011. DCE. DCE. DTE. DTE. Modem type. Asynchronous, Synchronous Half-Duplex, Full-Duplex. Modulation method. FSK 1 bit per baud. max speed =2400 bps PSK, DPSK up 3 bit per baud

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Modem' - kailey


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript
modem connection
Modem connection

PC

PC

modem

modem

110011

110011

DCE

DCE

DTE

DTE

modem type
Modem type
  • Asynchronous, Synchronous
  • Half-Duplex, Full-Duplex
modulation method
Modulation method
  • FSK 1 bit per baud. max speed =2400 bps
  • PSK, DPSK up 3 bit per baud
  • QAM combines ASK and PSK, encoding 4-7 bits per baud
  • TCM same as QAM, but adds extra bits for error correction
signal constellation
Signal Constellation

distance = sqrt(C2+D2)

point defines a legimate signal change

C

C

angle = sin-1

sqrt(C2+D2)

D

  • distance defines signal抯 amplitude
  • angle defines phase shift
constellation samples
Constellation samples

V.22

600 baud 1200 bps

PSK

V.22bis

600 baud 2400 bps

QAM

V.32

2400 baud 9600 bps

TCM

v 29 signal constellation
V.29 Signal Constellation

90

  • 8 phases with 4 amplitudes QAM
  • 2400 baud, 9600 bps

1010

3*sqrt(2)

0010

1000

1011

sqrt(2)

0011

5

0000

3

0

180

0111

1111

0001

1001

0101

0110

1101

0100

1110

1100

270

some standards
Some standards
  • V.32bis
    • 2-dimensional TCM with 128 pts.
    • transmission rate up to 14,400 bps
  • V.32ter
    • 2-dimensional TCM with 512 points
    • Transmisiion rates up to 19,200 bps
  • V.34
    • 4-dimensional TCM with 768 points
    • Transmisiion rates up to 28,800 bps
error correcting
Error correcting
  • LAPD (Link Access Protocol D) based on HDLC sychronous protocol
  • MNP (Micrcom Networking protocol)trademark of Microcom
  • TCM modulation with error detecting code
  • V.42CRC error correcting standard
mnp protocol
MNP protocol
  • Microcom Networking Protocol (MNP)Modem protocol developed by Micocom, Inc.
  • Divided into classes 1-10 MNP modems negotiate to operate at the highest supported class
  • Considered a de facto industry standard
v 42 recommendation
V.42 Recommendation
  • V.42
    • Defines error-checking standard
    • uses CRC for each data block
  • V.42bis
    • Defines modem compression using the Lempel Ziv method
fallback
9,600 bps

modem

modem

Down

speed

7,200 bps

modem

modem

4,800 bps

modem

modem

Fallback
smart modem
Smart modem
  • Introduces by Hayes Microcomputer Products
    • known as Hayes-comptible modems
  • Properties
    • standard modem with microprocessor
    • automatic dialling
    • provides command in ASCII form
  • Hayes command
    • known as Hayes-comptible modems
    • AT DT 9,9985800
hayes response codes
Hayes Response Codes
  • 0 OK
  • 1 CONNECT
  • 2 RING
  • 3 NO CARRIER
  • 4 ERROR
  • 5 CONNECT 1200
  • 6 NO DIALTONE
  • 7 BUSY
  • 8 NO ANSWER
  • 10 CONNECT 2400
ad