Data Transmission and Computer Accese ‘The Picturephone™ System: Widchand Data Service By E.G. BKNDIEK and RD. HOWSON, (Maas rod eter 8, 103 true of We eoving Vieturophone® noteork to provide commons vilted widebond date sein wate atep Ut ha eonticaing effet (0 Loti the sowing ne for woo Suforeation Jas, im graalr gue tite, oer Tongr tenn, and of Lower eae then 24 ow posible, Pall tow ss mle ftir pom salwar with nd minor madifentins Oe Fo focwtnfuc meng Feb! eens eapantites pert eeorent ate travsscan 3830.8 Bs; 3 expecta at date oon a! 12 ‘Mb al bone sland aa neve iprosamant ve made. ‘The rapid growth of data tears goer he paxt several oars dha indienod a nond for fndieg more evenk weone of wanemtirg Jarge esiouats of dla, Ae pont, Ie aj wf dale tonstssson covars arate ofa few Kiloi.x por sane over voieearadefaclitic. Modem oomputer-ueesced squipont ie eupwble of upersting <2 ea were) apvers 0: mizaibace euler an he wit 90 sigeiBeant ‘eonomie nenalty, Tor dats servivr nt mick igh speeds, wideband Irivate-ine faclitce ure avulabe. Adétionly, 1 comaror- oilelaa wider wrvin, cel Dante 80, 3 patil fable to pruvide SO-klys ivesuielon capobility over 1 forreity femerimentel network. Dawa servo aeicg the planned nstioavide net- Swork of Pistons “ures Tl pmeide anh ancuiee mn ar Ut rmgnibate genie th Thi, Widehund dats service uver the Dicturopkons network borics with the obesing, af w cote 4H08-U’c acu ily rough vse OF th Inited network of Posture tlie, Pater werview nt 194M KB/s fn aticiontel a alouek ‘apeuvemenis are mde itn 2 Sears Tt i expasted thee provision of evitehed widelund data cap. Abii on The Pletwrophone network will be signiion slop vomard 608) nen wes, stern TREMIEAE JOUNEAL, PrRRTARY 71 staying obe growing ou for high-speed duta eomumuaiensons. This ‘somsmo0-user ented service shot! he most atrctive towers whose ommucity of iateron include many etetone sprond aver a wide ‘ogmapie avin lh trae volome to dividual taons wot Ierge snough to justly (he we of wideband privatelin full, A devin objeulive or inl] data sarvigo ie to moske ull use of the aston with but ior modifoation to the basic fuc-to-awe serve. ais me be done vile roognising tht althoogh tha fave-tostace ‘Sgqal wraupiee a TMH andwidth vesious power epectnd distribu Sion and oroeessing epnstain'srectret the traraniaon 0 ambicear TEMA sigaals, Fre dats-iype signals, these constrade are mus sovere nh the interfer baleen he analog and dite! portions of te network. "The equipment used to provide thin intefece is eallad a codes ‘The entee which vil be ured for intial Pictasephone scree was Avsged peimazthy Zor vidos eervse. To accommodate signs the sneing intenfaoz iv aiaplivly lieed, bat both data and video “Synale nndergo the eoae bieis evening proces. "Thin procar lia trib ata serve to mtee el below ono szegabit per sound, As fhe network eantnuie to evolve, an improved andes i expentad to eve data rates up to La4L Mls by nlapuivey changing bie ene roving nese aa well as analog itera ‘Voth initia 46D S-RD/e anc tice 134-MDj wursien enw bob cained ‘Uuul extensive modifotion of the pwned Plea bore Tremere, Muay want its sash as N010R repeatere, central oEioe Fritehos and digital trunk will by sla hetioen video and dite eevee, ‘The fer eifronoce thet will be found bebneen the ceriece trill be in wuler operation, ention arrangements, and maintenance proved tho wiehand teenarission path in « (inl Picfarephone connac- tion involving gta felis will soit of om. eaalog loop, switch, fd trunk [uowed by a digital onceder, trunk, and decoder, ant Compiled bp the inverse ato try wot, an Joop. Several fan- ters i the bit speeds thet am ke realized through euch a pal reasonable cod, These factors includs the capacity of Uke digital rans, fesbaiea) nd etanomio considerations in enalo namin, td the methods vard to encode the analog signal into digeal form, sexnppans pana sera 00 1 Dipiat Prananiesion ‘pecidcaly, the tonnaaiadon rate of (he T2-format bit wsemmn ueed in the Plcturptona plant ie G12 MIb/a A eouall percentage of the foal bits trummiteed must be soaved for enntvol snd ayuchioniza- ton of fhe digiel system bus the remainder ne available to curs mereege infornaton, 8 Analog Tronamiaion ‘A fundamental retrieion op maximum éate rate in anslag trons smiasion in Tinta chanel bnndwideh, According to Uhenry che mas mur bru-level PAM. bil rale that ean be abiained in Uie [MHS ideo chanel without insreyzibal interference would be 2 Mth/s Proetialy, inporieeions (a Use Patereptone leap snd trunk trense mission eharucereies reduce pode ‘hab ean be Teaized without ‘iaduly comples intrumensccion to tho viinity of 1.5 Mbje. Simplo tnethude neo available to encode dete. igual ul rales up to that speed ino tho @-Mo/e digital capacity of T2 bitstreams ‘Although epeed Limitations have bean diccuased above in terms of bitrate, 3 ia busially signaling zace that ia limited by restrieted bandwith, Consequently higher bitrates aro potantnlly achievable by tranzmitting mere information por sgeal pulte; key by using nulilvel signa) formct To additgn, mom efflon use of the avail ible line is posible if puril-response" cual is wel CGaforamnatey, oth of thes techniques for inereasing bitrate will also ineresce the aumber of sigue] smplioudas that mst be Uist fsvshed in avier to veenver the tnanamiced date. ‘Tie, tuna, wil Fedoee he eror manga ut th signal has agains: noite and crogeale Inforferenes accumalated curing transmision The maryin will bo teduoad even further ip the disortone exsouncered on the enalog fallin "To overcome the love ef a-0r margin insured by multilevel egos, it right erm retsoaable to doorevee the tranamitt signal power to ‘the point wenn che eroe rate in recovad vo tlerehe level. However, it is neeseery to concider che nosnibility that high-power data seasle vill exorstol: into other severe. To prorat usu serieey yatiew- larly taceto-fare video), prnive every Une lint the eboneble ‘cauumizeion powar for data sgncls have boen formulated.’ Tt Sonion 4.1, iti chown thar the inrfors, lowctons, and poxer linilalions that are expected on Piztyrrphone wanlog ope ‘and trune will im ecoxoriclly feasible trutmission to binery AM with « maximum reve nese LF Mo/e, 67) me sau evra aueninsce, Jee, PEDARY At 8 Digital Eneating od Doznding ‘The objastive of sexu altemers nee of Pistursphons facilities Tonk Io ch yonardane af qpeatning, scaling, wl gu sewer edie Tnvng haa date signal fast ae if wero a video sgl, TU be shew tie, thir anoaduve ie the prinerpal dastor in the tier of 4608 bie fore ait-erveo bie rte iy, pave Onrasnatm oF rae Pietunmphons somos To delorsing abs ox Patwophone ne:nonk, tho econ som pvnts Calor Ue ver ‘ll he oomeidened eepezu tly. Ta rier uf Mica, se ene fae aug loops ene Ek, digital dae tion red anaemia apatilitos for da txaneinon ate The ‘at Aralop Loops and Trunte "The Teapa sc trunks Ive Deore Aneel tain sing impintony the pertinent wpeos tall be vsteratd here hen nepde, "Tha msjer sour wt nlerrrenen to daca sigzal ia the analog plot fa impuice noize; bath yal, allocations at actual tazamision teat Indeate subetetil operating manic gaizat thermal uses ard erse- face, Quarcital sly, the mpxmoam imple aciee lave) ean be rated from the ipetise Tor ‘acetotaco Piurepnane series ‘Meamued on the equrized falitice, tbe objective je abst ths prob- ability of bun-in-ponie weighted noe exceeding 18 millivolts be less than or cquis Wo 15 x 10[eLN > 18 mV) 16 X10 4. Por com venicace dhe voltoge threshold ef 18 mV un be trata! we RV fostoW of 85 ADV, Then, aoting thas Ue farmlontane obierive iy u weighted objestve, a GUB inoifeatva to ~29 dBY ig made inte data series ie not fete hy aujoetion weighting, snail ful use fro and deamphiss, Tmpalse soe ditribntinae fal lature Sarto ae expecta to dingy lune of 10 ty £2.08 par Aetode change in probability, Applving a 2dB slope wo uke —20 {TAY objet leads tothe woper Trt frase nese shown in Fig To determine mnsimum allowble date porters, searence met be toede to the protvtivn evteia Zor inercornection” One ition feveeming power pnsenk ix narow bands is met with emple margin by tandem dein eiwule, but = ascond aaterion for total power in peste. wider bute poss cover reitions on sgavl powur. Caleu- Tntime for the mason tearonabie binary date rato of 5 Mbjs indicate allowable traatnion levele of 2.6 dim, Mn tars of petk voltage eerose tho LOUD Tine hia Iva ie —7.5 ABV. winmaiso oath eeasice en | Ei pHi drs pstoranae eve ingle wis mtv fo ang ‘The errr pertonmanes ef this sign’ ean now be relat uote Ln pols nase objective dceuesed proviowy, To meet he use widehand fate eror rate objective of 10 Zor 9 pete cual level of —7.5 ABV, ie ie requzed that the probubilly of wie greair than —7.5 4B bo logs then or equal to 2 X10"[POY > —75dBV) 33 2X 10"), The factor of tro arses from the 50 pera probability Lat the noise and fignal are of opposite polarity. AW chown in Fig. 1 the data performance objective fs met with TTB of yagi, 'o fur the diswussion ns boon record with the ect of noiee on ‘et synale. Tn practice, however, even wih Uke ieband gain wel ‘equalized, two sigifcentsouzees ef siznal distortion remisin. Te frst CF thice is devistion of the net phase charaetaratie from sn idea) linear ehergeerstie, and the eoeond. is vovialn of trausmiaion characterises due tothe Juke of wemperture region om De lope land trom for initial server "To investigate the effest of dieortion on date guns, 1344-Mb/e ota signle were testod on sinulicedIvelee, The role wre ila trated by the "eye" patterns? of Ing 2."The pastern of Tig 2a was 672 rm mm svermw spore, roumeaL, risen 107. taken with th vest data eet sonnet acketo-bac and is, therefore, the reference patter. Expected worst-case phive station wos sim= lated by 42 kit of 22 AWG cable maintainod al constant temperature snd gain-equalied by repeaters spaced at KIL intervele. The die- tated “eye” is ahown in Fig. 2b, A Bode Equalizer wns used to smn- late worst-case distortion due to temperature variations, The ‘equalizer ebape was a comprouizg between tho regultion chsrsctar~ fstce of 0 kit of 24 ann 16 kl of 26 ATG ele; both of thee have 18 aB of gaia at tho L-MITz hand wige corespending to a 50°F vemperatore dferetial. Ue zerul is pictured in Fig. Zc. Mewsure= ‘nents of the “eye” paler ee the saripling points show an eective Io of margin neti! noe lative to an ideal undistorted sigial of 06 dB, 15 dB, and 15 dB for bask-to-back, phuso distortion, and vempernture dsvortion respetvely. The phare and temperature dise tation conditions od in thom eta sre extrem, It i aob unreteon fable, therefore, to allot $ dB of margin for wozet-aue facility Wktor- ‘font and dete vet (aleunecs ois ancipaed thet ecrond-senecwiin onble equalizers will nelude both temperstone regulation and improved phase conte, but the extra ‘engin derived therefrom wil bo locate Zor the extension of loop id trun length. Therefore, xo appresitble Improvement of analog ‘runanision performace shoud be erveeted from second- generat: faelites, co) ermmited: 0 base ali Gy ge «alae ised hat ond tore chen wronassn ens sear ors ‘he effect of distortion ean bo relate! lo the perform eurve o ig. 1. ‘The idea) signal ban an 11-€B murgin ganas Sxpulse noise. 1 Ba of this i alleen fair and daa vob datrtions, 8 aR of margin renaine to be distsibuced bacwven gxin misignmert, thermal ‘oie and erostalk: interfere ‘From the preceding eonideraton, it ean be concluded that date twanrmneson ab satee up ta 18 Mb/s is feasible ox Uke Pisturephone fiog loops ar tranks, The ‘anamission levels will cause neither fecenive interference ito wer rervces nor excceive susceptibility to inputs aces, However, margine aro so emall that transmission e Higher bit eotes pear ankle without wpprerable mereszo in data sel compiles. Lefoe closing this selion, (wo actions points should be consi eed, Bat i ll be shore i che felling ation cbt fh initiel- fervice eadee will nol srt ccte eater mach greute= ube 500 Kit find slenuls encountesing dicted trunk wil be subject to codec fitter end quantiring roise. Turthermars, n:erk protction erierin Impoce more severe power limitations on sigrals in this speed rong heoause their energy is concentrate? in she region of the transmission band where che tte of erosstolky interorenee to ocher earsogs is greater, Fortonataly, cable equaliawien “ents i enncenrate inter ferwnae x he high end ofthe bal; Uhe qaplifieation weeded ve ost ‘able valle euhances the hiah-frequenry componente of nsiso ant foetal. This tends to milo the sina and interference spectre Gineiny the nek reul e expected kobe performanoe sleet as good. ‘ac that a: 1.5 Mba, The expectation hae sen bame ut by peli ery testing an Pictwephone ssa! Caililie ‘The sevond point eonosmns low-freqcener‘ranemission rectors tics, To nllow for de potential dsforonens between ropeatze, the rene mnision jth rs be a-ecupled. ‘The extol ix in the viciily of 1 the wate time eonstant is on the order of 160 ms. With the BO-stage sorambler/dercrauler cemeky inoue wideband data tele the prolebity thas reoce chan 20 consovative symbols ef sie "ne polity wil be traramistoa i nelle. At a BD kb/s rat this forrespoads vo way 40 na without 9 sign, transition Ite les, thee Tore, tas low-frequerey catof will hove ao appreciable eel on Pictarenhene data teapanission, 42 Digitad Facttes A tentosed én eoxpacion ails" digital fetes will cary the hulle of Pletureptone tol traraminon. The basie bailing lat of the digital faites the 6312 M/s liferencial pole code mode (rd uu pia, overese nacuEMUON SOURNAL, HHUA 1 lated (DPCM) signal derived from the A/D operation in Une enc. Thin Bit lrvam may be toansmitad by ‘ef over TR facies or rmaltpleved nith oiler bit steers for lansmiaion over ratio or tool eassior ersten. * 4421 Codes Operation "The interface between the digital snd analog fcitos is provided by the codes which woes difential enowling to transform the normal Alls tnalce signal to a G12 Mb/e PCM signal’ Boouuse of busi format differences betmeen video nl Guth signals cis ocossry thet the codec te able to oper in (vy distinet meee. This is webieved by Sensing the preeanen of abeenoe of oo eymr signals to determine Inhethee the isput sgyal i ideo or data "For data signals te coda operates as » simple nonsyachronos Aifferontialeneider, The input sigal ie Drought to a nominal lol, O72 wove paakcte-pek, by a 6 dB AGC which compensates forall bot catastrophe tin misaligoment ia the analog plant. This signal in then sampled at t 2016 Mle rate with cao sample diferentally fmeaded into one! eight signal loves (412, --86, 284, =180 mill ots relative tu the input signal level), The reeultnt levels ate then bit excodods traming, elfing ard eaing bits are added; an a Barz Mb/s PCM sgual is delivered vo the digits! Suit. AL Ube fe tail, the eppusite procedure i ured to 2ecorer a nomine-ievel analog ‘Sgnal fo be sent to the sppropriate ead section. This is Mustrated in Fig 8 which compares typiea data signal as soon ab the input of th nearend endae, ig, da, to che ruling signal atthe output of the facend code, Hig. 8b, “From Fig. 3 one eo observe the distortion aud by thees typos of impairment introdead by the sodee: jitter, slope overlord (roantiving noe, iter introduend into the sgoal By the noxsynvhro- 1.3 piel $808:b/ di gna fous (th Input tow sar cet Soden ah et spt fa fend ots,