4/11/40 page 1 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Modem

4/11/40 page 2 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Modem connection DTE DCE modem PC modem PC

4/11/40 page 3 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Modem type Asynchronous, Synchronous Half-Duplex, Full-Duplex

4/11/40 page 4 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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

4/11/40 page 5 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Signal Constellation distance = sqrt(C 2 +D 2 ) D C C sqrt(C 2 +D 2 ) angle = sin -1 point defines a legimate signal change distance defines signal 抯 amplitude angle defines phase shift

4/11/40 page 6 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Constellation samples V baud 1200 bps PSK V.22bis 600 baud 2400 bps QAM V baud 9600 bps TCM

4/11/40 page 7 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL V.29 Signal Constellation 8 phases with 4 amplitudes QAM 2400 baud, 9600 bps sqrt(2) 3*sqrt(2)

4/11/40 page 8 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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

4/11/40 page 9 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Interface V.S. Operating rate modem PC interface speedoperating rate

4/11/40 page 10 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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.42 CRC error correcting standard

4/11/40 page 11 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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

4/11/40 page 12 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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

4/11/40 page 13 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Fallback modem 9,600 bps Down speed 7,200 bps modem 4,800 bps

4/11/40 page 14 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL 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,

4/11/40 page 15 Department of Computer Engineering, Kasetsart University Introduction to Computer Communications and Networks CONSYL Hayes Response Codes 0OK 1CONNECT 2RING 3NO CARRIER 4ERROR 5CONNECT NO DIALTONE 7BUSY 8NO ANSWER 10CONNECT 2400