pair 1 Mm 300 Hz ! VLF = Very Low Frequency UHF = Ultra High Frequency ! LF = Low Frequency SHF = Super High Frequency

Transcription

1 nroduion o Wireless Neworks: proools and perormane analsis Luiano Bononi bononi@s.unibo.i Tesi onsigliai: William Sallings, Wireless Communiaions & Neworks, Prenie Hall,, SBN Johen H. Shiller, Mobile Communiaions, Addison Wesle,, SBN Yi B. Li, mri Chlama, Wireless and Mobile Nework Arhieures, John Wile & Sons,, SBN Theodore S. Rappapor, Wireless Communiaions: priniples and praie, Prenie Hall,, SBN 343 Cumulaive redis: some igures have been aken rom slides ound on he web, b he ollowing auhors (in alabehial order): J.J. Garia Luna Aeves (us), James F. Kurose & Keih W. Ross, Johen Shiller (ub), Niin Vaida (uiu)...alri esi e arioli saranno ornii in seguio. Frequenies or (wired and wireless) ommunia. wised pair oa able opial ransmission Mm 3 H km 3 kh m 3 MH m 3 MH mm 3 GH µm 3 TH µm 3 TH Wireless PHY level VLF LF MF HF VHF UHF SHF EHF inrared visible ligh UV! VLF = Ver Low Frequen UHF = Ulra High Frequen! LF = Low Frequen SHF = Super High Frequen! MF = Medium Frequen EHF = Era High Frequen! HF = High Frequen UV = Ulraviole Ligh! VHF = Ver High Frequen! Frequen and wave lengh:! λ = /! wave lengh λ, speed o ligh 3 8 m/s, requen 3 4 Frequenies or mobile ommuniaion Frequenies and regulaions! VHF/UHF ranges or mobile simple, small anenna or ars deerminisi propagaion haraerisis, reliable onneions! SHF and higher or direed links, saellie ommuniaion small anenna, large bandwidh available! Wireless LANs use requenies in UHF o SHF sperum some ssems planned up o EHF limiaions due o absorpion b waer and ogen moleules (resonane requenies) weaher dependen ading, loss aused b heav rainall... 5! TU-R holds auions or new requenies, manages requen bands worldwide (WRC, World Radio Conerenes) Cellular Phones Cordless Phones Wireless LANs 575 Ohers RF-Conrol 7, 8, 48, 433, 868 Europe USA Japan GSM , /46-467, , 89-95/935-96, 7-785/85-88 UMTS (FDD) 9-98, -9 UMTS (TDD) 9-9, -5 CT , CT DECT 88-9 EEE HPERLAN , 547- AMPS, TDMA, CDMA , TDMA, CDMA, GSM 85-9, PACS 85-9, PACS-UB EEE , RF-Conrol 35, 95 PDC 8-86, , , PHS JCT EEE RF-Conrol 46, 868 6

2 Signals Fourier represenaion o periodi s! phsial represenaion o daa union o ime and loaion! parameers: parameers represening he value o daa! lassiiaion g( ) = + n n= a sin(πn) + b os(πn) n n= oninuous ime/disree ime oninuous values/disree values = oninuous ime and oninuous values digial = disree ime and disree values! parameers o periodi s: period T, requen =/T, ampliude A, phase shi ϕ sine wave as speial periodi or a arrier: s() = A sin( π + ϕ ) 7 ew harmonis omposiion man (ininie) harmonis periodi ideal periodi 8 Signals Anennas: isoropi radiaor! Dieren represenaions o s ampliude (ampliude domain) requen sperum (requen domain) phase sae diagram (ampliude M and phase ϕ in polar oordinaes) A [V] A [V] Q = M sin ϕ! How eleromagnei waves diuse on spae?! soropi radiaor: equal radiaion in all direions (hree dimensional) onl a heoreial reerene anenna [s] ϕ = M os ϕ! Real anennas alwas have direive ees (veriall and/or horionall) ϕ [H]! Composed s ranserred ino requen domain using Fourier ransormaion! Digial s need ininie requenies or pere ransmission! Radiaion paern: measuremen o radiaion around an anenna ideal isoropi radiaor modulaion wih a arrier requen or ransmission (!) 9 Anennas: simple dipoles Anennas: direed and seoried! Real anennas are no isoropi radiaors bu, e.g., dipoles " shape o anenna proporional o wavelengh! Oen used or mirowave onneions or base saions or mobile phones (e.g., overage o a valle) λ/4 λ/ direed anenna! Eample: Radiaion paern o a simple Herian dipole side view (-plane) side view (-plane) op view (-plane) side view (-plane) side view (-plane) op view (-plane)! Gain: maimum power in he direion o he main lobe ompared o he power o an isoropi radiaor (wih he same average power) simple dipole op view, 3 seor op view, 6 seor seoried anenna

3 Signal propagaion ranges Signal propagaion! Transmission range! Propagaion in ree spae alwas like ligh (sraigh line) ommuniaion possible low error rae! Deeion range deeion o he possible no ommuniaion possible! nererene range ma no be deeed sender ransmission deeion inererene disane! Reeiving power proporional o /d² (d = disane beween sender and reeiver)! Reeiving power addiionall inluened b ading (requen dependen) shadowing releion a large obsales reraion depending on he densi o a medium saering a small obsales diraion a edges adds o he bakground noise 3 shadowing releion reraion saering diraion 4 Real world eample Mulipah propagaion! Signal an ake man dieren pahs beween sender and reeiver due o releion, saering, diraion LOS pulses mulipah pulses a sender a reeiver! Time dispersion: is dispersed over ime " inererene wih neighbor smbols, ner Smbol nererene (S)! The reahes a reeiver direl and phase shied " disored depending on he phases o he dieren pars 5 6 Ees o mobili Mulipleing: muliple use o shared medium! Channel haraerisis hange over ime and loaion pahs hange dieren dela variaions o dieren pars dieren phases o pars " quik hanges in he power reeived (shor erm ading)! Addiional hanges in disane o sender obsales urher awa power shor erm ading long erm ading " slow hanges in he average power reeived (long erm ading)! Mulipleing in 4 dimensions spae (s i ) ime () requen () ode ()! Goal: muliple use o a shared medium hannels k i s k k k 3 k 4 k 5 k 6 s 3 s! mporan: guard spaes needed! 7 8

4 Frequen muliple Time muliple! Separaion o he whole sperum ino smaller requen bands! A hannel ges a erain band o he sperum or he whole ime! Advanages: no dnami oordinaion neessar works also or s! Disadvanages: k k k 3 k 4 k 5 k 6 wase o bandwidh i he rai is disribued unevenl inleible guard spaes! A hannel ges he whole sperum or a erain amoun o ime! Advanages: onl one arrier in he medium a an ime hroughpu high even or man users! Disadvanages: k k k 3 k 4 k 5 k 6 preise snhroniaion neessar 9 Time and requen muliple Code muliple! Combinaion o boh mehods! Eah hannel has a unique ode! A hannel ges a erain requen band or a erain amoun o ime! All hannels use he same sperum a he same ime Eample: GSM! Advanages: k k k 3 k 4 k 5 k 6! Advanages: beer proeion agains apping proeion agains requen seleive inererene higher daa raes ompared o ode mu! bu: preise oordinaion required k k k 3 k 4 k 5 k 6 bandwidh eiien no oordinaion and snhroniaion neessar good proeion agains inererene and apping! Disadvanages: lower user daa raes more omple regeneraion ( )! mplemened using sperum ehnolog Modulaion Modulaion and demodulaion! Digial modulaion digial daa is ranslaed ino an (baseband) ASK, FSK, PSK dierenes in speral eiien, power eiien, robusness! Analog modulaion shis ener requen o baseband up o he arrier (i.e. FM) baseband digial daa digial modulaion modulaion ransmier arrier! Moivaion smaller anennas (e.g., λ/4) Frequen Division Mulipleing medium haraerisis! Basi shemes Ampliude Modulaion (AM) Frequen Modulaion (FM) Phase Modulaion (PM) 3 demodulaion arrier baseband snhroniaion deision digial daa reeiver 4

5 Digial modulaion Advaned Frequen Shi Keing! Modulaion o digial s known as Shi Keing! Ampliude Shi Keing (ASK): ver simple low bandwidh requiremens ver susepible o inererene! Frequen Shi Keing (FSK): needs larger bandwidh! Phase Shi Keing (PSK): more omple robus agains inererene! bandwidh needed or FSK depends on he disane beween he arrier requenies (range o requen variaion).! speial pre-ompuaion avoids sudden phase shis " MSK (Minimum Shi Keing)! bi separaed ino even and odd bis, he duraion o eah bi is doubled! depending on he bi values (even, odd) he higher or lower requen, original or invered is hosen! he requen o one arrier is wie he requen o he oher! Equivalen o ose QPSK! even higher bandwidh eiien using a Gaussian low-pass iler " GMSK (Gaussian MSK), used in GSM 5 6 Eample o MSK Advaned Phase Shi Keing daa even bis odd bis low requen high requen MSK No phase shis! bi even odd h n n h value h: high requen n: low requen +: original -: invered 7! BPSK (Binar Phase Shi Keing): bi value : sine wave bi value : invered sine wave ver simple PSK low speral eiien robus, used e.g. in saellie ssems! QPSK (Quadraure Phase Shi Keing): bis oded as one smbol smbol deermines shi o sine wave A needs less bandwidh ompared o BPSK more omple! Oen also ransmission o relaive, no absolue phase shi: DQPSK - Dierenial QPSK (S-36, PHS) Q Q 8 Quadraure Ampliude Modulaion Hierarhial Modulaion! Quadraure Ampliude Modulaion (QAM): ombines ampliude and phase modulaion! i is possible o ode n bis using one smbol! n disree levels, n= idenial o QPSK! bi error rae inreases wih n, bu less errors ompared o omparable PSK shemes Q Eample: 6-QAM (4 bis = smbol)! Smbols and have he same phase, bu dieren ampliude. and have dieren phase, bu same ampliude.! " used in sandard 96 bi/s modems 9! modulaes wo separae daa sreams ono a single sream! High Priori (HP) embedded wihin a Low Priori (LP) sream! Muli arrier ssem, abou or 8 arriers! QPSK, 6 QAM, 64QAM Q! Eample: 64QAM good reepion: resolve he enire 64QAM onsellaion poor reepion, mobile reepion: resolve onl QPSK porion 6 bi per QAM smbol, mos signiian deermine QPSK HP servie oded in QPSK ( bi), LP uses remaining 4 bi 3

6 Spread sperum ehnolog Spread sperum ehnolog! Problem o ransmission: requen dependen ading an wipe ou narrow band s or duraion o he inererene! CDMA: narrowband ino broadband using speial ode! proeion agains narrow band inererene power inererene power deeion a reeiver proeion agains narrowband inererene! Side ees: oeisene o several s wihou dnami oordinaion ap-proo (anno be deeed wihou knowing he ode)! Alernaives: Dire Sequene, Frequen Hopping inererene 3! inuiive eample: narrowband inererene ee on ransmission: ransmi Hello World oded using narrowband ellow requen and broadband man olors requenies H e l l o W o r l d H e l l o W o r l d a burs o ellow inererene adds o he or a signiian ime: wha is he resul a he reeiver? Narrowband inererene H e l? l? o? W?? o r l d H e l l o W? o r l d Narrowband Broadband FHSS Broadband CDMA ime Narrowband Broadband FHSS Broadband CDMA 3 Spreading and requen seleive ading DSSS (Dire Sequene Spread Sperum) hannel quali hannel quali narrow band sperum 3 4 guard spae 5 6 requen requen narrowband hannels sperum hannels! XOR o he wih pseudo-random number (hipping sequene) man hips per bi (e.g., 8) resul in higher bandwidh o he (low hroughpu) b! Advanages redues requen seleive ading in ellular neworks base saions an use he same requen range several base saions an dee and reover he so handover! Disadvanages b : bi period : hip period user daa XOR hipping sequene = resuling 33 preise power onrol neessar 34 DSSS (Dire Sequene Spread Sperum) reeived user daa X hipping sequene arrier demodulaor sperum ransmier reeiver lowpass ilered arrier hipping sequene modulaor orrelaor ransmi sampled produs sums daa X inegraor deision 35 FHSS (Frequen Hopping Spread Sperum)! Disree hanges o arrier requen sequene o requen hanges deermined via pseudo random number sequene (e.g. seed = (hos ideniier in Blueooh))! Two versions Fas Hopping: several requenies per user bi Slow Hopping: several user bis per requen! Advanages requen seleive ading and inererene limied o shor period simple implemenaion uses onl small porion o sperum a an ime! Disadvanages no as robus as DSSS simpler o dee 36

7 FHSS (Frequen Hopping Spread Sperum) FHSS (Frequen Hopping Spread Sperum) b user daa user daa narrowband modulaor modulaor ransmi 3 d slow (3 bis/hop) ransmier requen snhesier sequene 3 d as (3 hops/bi) reeived sequene demodulaor requen snhesier narrowband demodulaor daa b : bi period d : dwell ime reeiver Spae division mu: ell sruure Frequen planning! spae division muliple: base saion overs a erain ransmission area (ell)! Mobile saions ommuniae onl via he base saion! Advanages o ell sruures: higher apai, higher number o users less ransmission power needed more robus, deenralied base saion deals wih inererene, ransmission area e. loall! Frequen reuse onl wih a erain disane beween he base saions! Sandard model using 7 requenies: ! Fied requen assignmen: erain requenies are assigned o a erain ell problem: dieren rai load in dieren ells! Problems: ied nework needed or he base saions (inrasruure) handover (hanging rom one ell o anoher) neessar inererene wih oher ells! Dnami requen assignmen: base saion hooses requenies depending on he requenies alread used in neighbor ells more apai in ells wih more rai! Cell sies rom some m in iies o, e.g., 35 km on he ounr side (GSM) - even less or higher requenies 39 assignmen an also be based on inererene measuremens 4 PHY modelling issues PHY modelling issues! Usuall he PHY laer is onsidered a Blak bo in he simulaion model (e.g. when suding higher laers)! Man PHY parameers an have a deep ee on higher laers behavior (and are inherenl oninuous...) a modeler needs o know wha is required o be modeled or obaining signiian resuls (e.g. mapping o disree...) simpliing assumpions an lead o wrong resuls Warning: more analsis?! Usuall he hoie is o model onl ew parameers o he PHY laer, desribing he aggregae ee o main parameers (see laer) and heir values disribuions. Trae driven simulaion? Regression daa rom logged rae resuls? e.g. hannel saes # Bi error rae # prob. o pake error? e.g. nework opolog # inererene # bi error rae? e.g. oding and rasmission ehnique # daa rae? 4! Homework: analiial analsis o a PHY ssem a given hannel is DSSS wih 8 hips/bi maimum hipping rae =.. hip/se an reover up o hip errors/bi probabili o hip error = Pe probabili o a bi error? rame lengh (onsan) = 5 Bes probabili o rame error? will be used as he PHY (blak bo) reliabili parameer... imeou dela beore pake reransmission aemp = se average dela beore agged rame s suessul ransmission? 4