6.02 Fall 2014 Lecture 1, Slide #1 6.02 Fall 2014Lecture #1• !Digital!vs.!analog!communica0on!• !The!birth!of!modern!digital!communica0on!• !Informa0on!and!entropy!• !Binary!codes!6.02 Fall 2014 Lecture 1, Slide #2 Katrina!LaCurts!George!Verghese!!Vincent!Chan!Srini!Devadas!Yury!Polyanskiy!Victor!Zue!!Ali!AlShehab!Max!Dunitz !!Ellen!Finch!Ameesh!Goyal!Ravi!Netravali!Quan!Nguyen!Evangelos!Taratoris!!Pra0ksha!Thaker!!!!!!!!!+ LAs and Graders! 6.02 Course Staff6.02 Fall 2014 Lecture 1, Slide #3 Course Ethos**Animating principlesGreat!material!…!!!!!!!!!!!!!!!!!a!direct!and!tangible!line!!!!!!!!!!!!!!!of!development!from!!!!!!!!!!!!!!!!200!years!ago!to!systems!!!!!!!!!!!!!!!!of!importance!today!!!!!!!!!!!!!!!(and!tomorrow!),!including!!!!!!!!!!!!!!!!many!links!to!MIT!!Lots!to!learn!(and!teach)!…!!!!!!!!!!!!!!!collabora0vely!!!Individual!effort!…!!!!!!!!!!!!!!!we!have!to!be!seeing!!!!!!!!!!!!!!!!!your!own!work!!!!!!!!!!!!!!!!on!anything!submiXed!!!!!!!!!!!!!!!!!for!evalua0on,!with!!!!!!!!!!!!!!!!!all!collabora0on!!!!!!!!!!!!!!!!fully!acknowledged!6.02 Fall 2014 Lecture 1, Slide #4 Lectures and Recitations…!are!!your!best!and!most!efficient!!entry!to!the!subject.!Even!the!stuff!that’s!confusing!or!not!clear!in!lecture/recita0on!is!useful!in!le]ng!you!know!what!to!get!!clarified.!So!please!aXend!!!!Your!“contract”!in!this!subject!is!not!with!notes!or!slides,!but!with!the!staff,!and!!specifically!with!what’s!developed!in!lectures!!and!recita0ons.!6.02 Fall 2014 Lecture 1, Slide #5 Digital vs. Analog Communication• ANALOG!!Communica0ng!a!con0nuousb0me!waveform!!(e.g.:!acous0c!speech;!voltage!from!a!microphone).!– Analog!electronics!– Fidelity!to!the!waveform!• DIGITAL!!Communica0ng!a!message!comprising!a!discreteb0me!sequence!of!symbols!from!some!source!alphabet!(e.g.:!wriXen!text;!Morse!telegraphy;!computer!communica0on)!– Ofen!coded!onto!some!other!sequence!of!symbols!that’s!adapted!to!the!communica0on!channel,!e.g.,!binary!digits,!0!and!1.!– Ofen!involving!analog!communica0on!across!the!physical!channel!!– Fidelity!to!the!message!– Well!suited!to!taking!advantage!of!ever!increasing!computa0onal!power,!storage,!interconnectedness!!!!!!!!6.02 Fall 2014 Lecture 1, Slide #66.02 Fall 2014 Lecture 1, Slide #7 Samuel F.B. Morse 1791-18726.02 Fall 2014 Lecture 1, Slide #86.02 Fall 2014 Lecture 1, Slide #9 Samuel F.B. Morse• Invented!(1832!onwards,!patent!#1,647!in!1840)!the!most!prac0cal!form!of!electrical!telegraphy,!including!keys,!wire!arrangements,!electromagnets,!marking!devices,!relays,!…,!and!Morse!code!!• Worked!0relessly!to!establish!the!technology!• Afer!ini0al!struggles,!telegraphy!was!quickly!adopted!and!widely!deployed!!– TransbAtlan0c!cable!aXempts!1857!(16!hours!to!send!98!words!from!Queen!Victoria!to!President!Buchanan!),!1858,!1865,!finally!success!in!1866!(8!words/minute)!– Transbcon0nental!US!in!1861!(effec0vely!ended!the!Pony!Express)!– TransbPacific!1902!• Telegraphy!transformed!communica0on!(transbAtlan0c!0me!from!10!days!by!ship!to!minutes!by!telegraph)!and!commerce,!also!spurred!major!developments!in!EE!theory!&!prac0ce!(Henry,!Kelvin,!Heaviside,!Pupin,!…)!!6.02 Fall 2014 Lecture 1, Slide #10 Route of the 1858 trans-Atlantic cable6.02 Fall 2014 Lecture 1, Slide #116.02 Fall 2014 Lecture 1, Slide #12 Need a Space symbol for instantaneous and unique decodability6.02 Fall 2014 Lecture 1, Slide #136.02 Fall 2014 Lecture 1, Slide #14 Fast-forward 100 years• Via!– Telephone!(“Improvement!in!Telegraphy”,!patent!#!174,456,!Bell!1876)!– Wireless!telegraphy!(Marconi!1901)!– AM!radio!(Fessenden!1906)!!– FM!radio!(Armstrong!1933)!!– Television!broadcas0ng!by!the!BBC!(1936)!• Mostly!back!to!analog!for!a!while!!• Bell!Labs!galaxy!of!researchers,!who!also!set!the!stage!for!a!return!to!digital!– Nyquist,!Bode,!Hartley,!…!!!6.02 Fall 2014 Lecture 1, Slide #15 Alexander Graham Bell1847–19226.02 Fall 2014 Lecture 1, Slide #16 Harry Nyquist1889–1976Prolific!and!seminal!work!from!Bell!Labs,!including!“Certain!topics!in!telegraph!transmission!theory”!1928!6.02 Fall 2014 Lecture 1, Slide #17 Claude E. Shannon, 1916-20011937!Masters!thesis,!EE!Dept,!MIT!!A"symbolic"analysis"of"relay"and"switching""circuits!!Introduced!applica0on!of!Boolean!!!algebra!to!logic!circuits,!and!vice!versa.!!!Very!influen0al!in!digital!circuit!design.!!“Most!important!Masters!thesis!of!the!century”!!1940!PhD,!Math!Dept,!MIT!!!An"algebra"for"theore6cal"gene6cs"!To!analyze!the!dynamics!of!Mendelian!!!popula0ons.!!!Joined!Bell!Labs!in!1940.!!!!!!!!!!!!!!“A!mathema0cal!theory!of!cryptography”!1945/1949!!!!!!!!“A!mathema)cal!theory!of!communica)on”!1948!!!!!!!!!!!!!!!!!!!!!!!!MIT faculty 1956-19786.02 Fall 2014 Lecture 1, Slide #18 Stationary Discrete Memoryless Probabilistic SourceS!…, s8 , s2 , s11 , s1 , s4 , s13 , s2 , … Emi]ng!symbols!sequen0ally!in!0me,!with!the!symbol!at!each!0me!chosen!independently!of!the!choices!at!other!0mes,!but!using!the!same!!probability!distribu0on,!i.e.,!an!independent,!iden0cally!distributed!or!i.i.d.!symbol!stream!!6.02 Fall 2014 Lecture 1, Slide #19 Single Link Communication ModelDigitize (if needed) Original source Source coding Bit stream Render/display, etc. Receiving app/user Source decoding Bit stream Channel coding (for bit error protection) Recv samples + Demapper Mapper + Xmit samples Bits Signals (voltages) over physical link Channel decoding (bit error correction) End-host devices Bits Source symbols6.02 Fall 2014 Lecture 1, Slide #20 6.02 SyllabusPointbtobpoint!communica0on!channels!(transmiXer→receiver):!• Measuring!and!appropriately!encoding!informa0on!BITS!• Transmission!on!physical!channels!SIGNALS!• Noise,!bit!errors,!error!correc0on!• Sharing!a!channel!Mul0bhop!networks:!• Packet!switching,!efficient!rou0ng!PACKETS!• Reliable!delivery!on!top!of!a!bestbefforts!network!6.02 Fall 2014 Lecture 1, Slide #21 Probabilistic Models• Universe!U!of!elementary!outcomes!e1,!e2,!…!.!One!and!only!one!outcome!in!each!experiment!or!run!of!the!model.!• Events!A,!B,!C,!…!are!subsets!of!!U.!We!say!event!A!has!occurred!if!the!outcome!of!the!experiment!lies!in!A.!•