Communication and Networks: A historical perspective EPL 324 Andreas Pitsillides

Epl324 Networks: A historical 1 perspective Communicating Humans From human presence on earth: Some selected examples • Sign language? ---first (?) intelligent form of communication? – Allows communicaiton, BUT – Limited by distance (100’s of meters), coded and limited by lack of richness of language – Quality of Communication poor. • Speech – Richness of language, more natural, but limited by distance (100s of meters), could be corrupted by noise, i.e many people talking together (a ‘protocol’ or ‘code of conduct’ is required). • Written – Richness of language, not necessarily limited by distance, limited by encrypted form (must know script form). Must have pen and paper (not so natural). Can be corrupted by e.g. ‘bad’ handwriting or spilling coffee on the paper (noise) • Pigeon – Not limited by distance much, but limited by volume, – unreliable - could easily be lost – (pigeon is not necessarily reliable — could go elsewhere, be eaten by a vulture, etc.) Epl324 Networks: A historical 2 perspective Communicating Humans (cont.)

• Smoke signals – Limited by distance, limited by volume (rate of information transfer), limited by vocabulary-Smoke ON/Smoke OFF – [is this a big problem? Recall digital/binary communication] – limited by encrypted form (not many are smoke signal readers—could be an advantage. When?), – can be corrupted by wind

Epl324 Networks: A historical 3 perspective Communicating Humans (cont.)

• over electrical wires – Not limited as much by distance, – limited by volume over a given time period (information rate), – limited by encrypted form (not many are Morse code readers), – can be corrupted by electromagnetic noise, but not as easily as the smoke signal

• signal (as in radio and TV) – Not limited as much by distance, – not limited as much by volume, – not limited by encrypted form, but it is encoded (modulated), – can be corrupted by electromagnetic noise (it touches upon quality of signal).

Epl324 Networks: A historical 4 perspective Communicating Humans and communication channels • Radio signals bounced on upper layers of atmosphere, or even satellites – Not limited by distance--universe, not limited a lot by volume, can be influenced by weather conditions, can be influenced by position of satellite (geostationary, etc…) • Binary (digital) computer signals – Not limited by distance by using repeaters, not limited a lot by volume, limited by encrypted form (not many are data signal code readers), not as easily corrupted by noise (if properly designed), offers reliable / dependable quality • Light signals (optical fibers) – Not limited by distance, not limited (at all) by volume, limited by encrypted form, not corrupted by e-m noise, offers reliable / dependable quality • Power lines

Epl324 Networks: A historical 5 perspective Some indicative early systems

• Polybius (203-120 BC) – Coding: B=21, S=34 – 2 sets of 5 torches behind screens – 2 torches up = Ready-to-send / Clear-to-send – Left screen, then right screen – : ~ 2 words/minute – Remained ‘state-of-the-art’ for roughly 2000 years

Epl324 Networks: A historical 6 perspective Some indicative early systems

• (1763-1805) • 1792: Optical (arms & telescopes) • 2 arms x 7 positions x 4 bar positions = 196 symbols • Operated by two people • Can run full-duplex (but hard!) • Delay: Paris-Lille (190km) in 32 minutes • Bandwidth: ~ 15 bits/minutes • Most of the features of modern networks (routing, error correction, flow control)

Epl324 Networks: A historical 7 perspective Some indicative early systems

• Morse code

– 1837: Cooke and Wheatstone – 25 characters/minute – 1851: Paris – London cable – 1852: 6400km cable in England – 1866: London – New York

– 20 words for $100

Epl324 Networks: A historical 8 perspective Some indicative early systems

• (“voice over wires”) – Reiss (1863), Bell (1876),Gray(1876), Edison(1877), Siemens (1878), .... – “This ‘phone’ has way too many shortcomings to consider it as a serious way of communicating. The unit is worthless to us.” [Western Union,1876]

Epl324 Networks: A historical 9 perspective Communicating Humans and communication channels (cont.) • What do the earlier examples have in common? – Human adaptability and ingenuity in finding different (often ‘unnatural’) ways to communicate – Different channels (guides) have been used (wind, air-space for pigeons, line-of-sight for smoke signals, radio waves, electricity signals, e-m waves, guides, light (optical) waves – Often to surpass limitations of the medium, encryption and noise cancelling techniques are used. At times information is piggy- backed on other more convenient signal (e.g radio ) – Offered quality of service must be at acceptable levels To achieve our goal of effective and reliable communication, from anywhere, we need to study communication and networking (starting with the fundamentals)

Epl324 Networks: A historical 10 perspective