Mobile Communications

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1 Moble Communaons Pa IV- Popagaon Chaaess Mul-pah Popagaon - Fadng Poesso Z Ghassemlooy Shool o Compung, Engneeng and Inomaon Senes, Unvesy o Nohumba U.K. hp://soe.unn.a.uk/o

2 Conens Fadng Dopple Sh Dspeson Summay

3 The Moble Rado Popagaon Channel A weless hannel exhbs sevee luuaons o small dsplaemens o he anenna o small ae equeny oses. Channel Amplude n db vesus loaon (= me*veloy) and equeny

4 Tme Dspeson vs Fequeny Dspeson Tme Dspeson Fequeny Dspeson Tme doman - Channel vaaons - Delay spead nepeaon - Fas adng - Ine-symbol neeene - Coelaon dsane - Channel equalzaon Fequeny - Dopple speum - Fequeny seleve adng doman - Ineae Ineeene - Coheene bandwdh nepeaon

5 Two Dsn Mehansms Tme dspeson Fequeny dspeson Tme vaaons o he hannel ae aused by moon o he anenna Channel hanges evey hal a wavelengh Movng anenna gves Dopple spead Fas adng eques sho pake duaons, hus hgh b aes Delayed eleons ause nesymbol neeene Channel equalzaon may be needed. Fequeny seleve adng Mulpah delay speads eque long symbol mes Fequeny dvesy o spead speum may help Tme dspeson poses equemens on synhonzaon and ae o onvegene o hannel esmaon Ineleavng may help o avod bus eos

6 Fadng Small Sale Fla adng Mulpah me delay Fequeny seleve adng Fadng Dopple spead Fas adng Slow adng

7 Mulpah Popagaon - Fadng a Daed wave b Releed wave No de pah a b Anenna y = a + b a b Anenna y = 0 a & b ae n phase a & b ae ou o phase by Complee adng when 2d/ = n, d s he pah deene

8 Mulpah Popagaon - ond. Fo a saonay moble un wh no de pah, he eeved sgnal an be expessed as a sum o delayed omponens o n ems o phaso noaon: Pulse an S N ap 1 A sngle pulse S N ( ) a 1 os (2 Whee: a s he amplude o he saeed sgnal, p() s he ansmed sgnal (pulse) shape, s he me aken by he pulse o eah he eeve, N s he numbe o deen pahs s he ae equeny )

9 Sgnal sengh elave o 1uV (db) Fadng - Types Slow (Long) Tem Fas (Sho) Tem (Also known as Raylegh adng) 30 Fas adng Slow adng Dsane () Exa epesenaon o adng haaess s no possble, beause o nne numbe o suaon.

10 Fadng - Slow (Long) Tem Slowe vaaon n mean sgnal sengh (dsane 1-2 km) Podued by movemen ove muh longe dsanes Caused by: - Tean onguaon (hll, la aea e.): Resuls n loal mean (long em adng) aenuaon and luuaon. - The bul envonmen (ual and uban aeas e.), beween base saon and he moble un: Resuls n loal mean aenuaon

11 Fadng - Slow (Long) Tem Reeve n,2 pah n n,3 S () n,1 k,4 one subpah Tansme k,1 k,3 k,2 pah k Numbe o pah S ap0 1 pah aenuaon ao o he h pah C. D. Chaalambous e al N

12 Fadng- Fas (Sho) Tem Desbes he onsan amplude luuaons n he eeved sgnal as he moble moves aound. Caused by - mulpah eleon o ansmed sgnal by loal saes (houses, buldng e.) - andom luuaons n he eeved powe Obseved ove dsanes = /2 Sgnal vaaon up o 30 db. Is a equeny seleve phenomenon. Can be desbed usng - Raylegh sass, (no lne o sgh). - Ran sass, (lne o sgh).

13 Fadng- Fas (Sho) Tem - ond. N a S 1 ) os (2 ) ( A eeved sgnal amplude s gven as he sum o delayed omponens. In ems o phaso noaon s gven as: O N N a a S 1 1 ) sn( ) sn(2 ) os ( ) os(2 ) ( N N a a S 1 1 ) sn( ) sn(2 ) os ( ) os(2 ) ( In-phase Quadaue

14 Fadng- Fas (Sho) Tem - ond. The phase an be assumed o be unomly dsbued n he ange (0, 2), povded he loaons o buldngs e. ae ompleely andom. Fo a lage N, he amplude o he eeved sgnal s: S ( ) X os(2 ) Y sn(2 ) whee X N 1 a os ( ), Y N 1 a sn( ) X and Y ae ndependen, denally dsbued Gaussan andom vaables.

15 Fadng- Fas (Sho) Tem - ond. The envelope o he eeved sgnal s: A Pobably densy unon ( X Y ) Raylegh Exponenal Whh wll be Raylegh dsbued: Assumng all omponens eeved have appoxmaely he same powe and ha all ae esulng om saeng. p 2 æ exp ç è 2s 2 2 s Whee 0< <, s 2 s vaane o A (he oal eeved powe n he mulpah sgnal). ö ø A o powe P

16 Rean Fadng I hee s one de omponen n addon o saeed omponens, he envelope eeved mulpah s Rean, whee he mpulse esponse has a non zeo mean. Rean dsbuon = Raylegh sgnal + de lne o sgh sgnal. The dsbuon s: p ö I ø æ s ç ès s æ exp ç è 2 2s s 2 ø ö s 2 s he powe o he lne o sgh sgnal and I 0 s a Bessel unon o he s knd

17 Fadng- Fas (Sho) Tem - ond. The pobably ha he ealzaon o he andom vaable has a value smalle han x s dened by he umulave dsbuon unon: d ( ) pd ( u) du Applyng o he Raylegh dsbuon d ( ) 1exp ( 2 / 2s 2 ) Fo small d ( ) ~ 2 / 2s 2

18 Feld sengh Fas Fadng Cases 1: Saonay Moble v Saonay v 4

19 Fas Fadng Cases 1 The numbe o adng depends on: Ta low Dsane beween he moble and movng as The eeved sgnal a he MU s: S N a P0 1

20 Fas Fadng Cases 1 whee Thus and s addonal elave delay (posve o negave) S 1 N N 1 j 2 jo x( ) e envelope x a o N 1 a e j 2

21 Fas Fadng Cases 2 1 ( 1 ) 2 ( 2 ) T 1 = d 1 / T 2 = d 2 / S x exp j j exp x N a a exp j 1 21

22 Feld sengh Fas Fadng Cases 3: Non-saonay Moble No saeed sgnals Sgnal level V The eeved sgnal a he moble s: s ( ) Amplude a o e j(2 o xos) x = V Wave numbe =2/ Tansmng equeny

23 Fas Fadng Cases 3: Dopple Fequeny A movng obje auses he equeny o a eeved wave o hange Subsung o and x, he expesson o he eeved sgnal s s ( ) a o e j2( V os) The Dopple equeny D V os m os The eeved sgnal equeny m os

24 Fas Fadng Cases 3: Dopple Fequeny When = 0 o (moble movng away om he ansme) m m When = 90 o (I.e. moble lng aound) When = 180 o (moble movng owads he ansme) m m

25 Fas Fadng Cases 4: Movng MU + Saonay Saee Volage Sandng Wave Paen x() s o () MU V s o () = 0 = ound p me

26 os 2 ) ( V j o o e a s o o V j o V j o e a e a s ) ( Inden sgnal Releed sgnal ø ö ç è æ o j o e V a j s sn 2 ) ( n V Fadng wh zeo amplude ous when Fas Fadng Cases 4 Reeved sgnal a he MU:

27 Fas Fadng Cases 5: Movng MU and Saees The esulan eeved sgnal s he sum o all he saeed waves om deen angles dependng upon he momenay aude o he vaous saees. s ( ) N 1 a o a e j 2 o Vos

28 Channel Fadng Ees Tansmng a sho pulse ove a () equeny-seleve (me-spead) adng hannel: Tansmed Reeved T p T p + d () me-seleve (Dopple-spead) adng hannel: Tansmed Reeved T p T p

29 Ees o Dopple shs Bandwdh o he sgnal ould nease o deease leadng o poo and/o mssed eepon. The ee n me s oheene me vaaon and sgnal dsoon Coheene me: Tme duaon ove whh hannel mpulse esponse s nvaan, and n whh wo sgnals have song poenal o amplude oelaon Coheene me s expessed by: T o D-max whee D-max s he maxmum Dopple sh, whh ous when = 0 degees To avod dsoon due o moon n he hannel, he symbol ae mus be geae han he nvese o oheene me.

30 How do sysems handle Dopple speads? Analog Cae equeny s low enough o avod poblems (andom FM) GSM Channel b ae well above Dopple spead TDMA dung eah b / bus ansmsson he hannel s aly onsan. Reeve anng/updang dung eah ansmsson bus Feedbak equeny oeon

31 Coheene Dsane Coheene dsane s he mnmum dsane beween pons n spae o whh he sgnals ae mosly unoelaed. Ths dsane s usually gae han 0.5 wavelenghs, dependng on anenna beamwdh and angle o aval dsbuon. A he BTS, s ommon pae o use spang o abou 10 and 20 wavelenghs o low-medum and hgh anenna heghs, espevely (120 o seo anennas).

32 Coheene Bandwdh (B) Range o equeny ove whh hannel s la I s he bandwdh ove whh wo equenes have a song poenal o amplude oelaon Powe Sgnal bandwdh B s Desbes equeny seleve phenomenon o as adng Coheene Bandwdh B Feq. Ee o equeny seleve adng on he eeved sgnal speum

33 Esmaon o Coheene Bandwdh Coheene bandwdh s esmaed usng he value o delay spead o he hannel, s Fo oelaon > 0.9 Fo oelaon > 0.5 Typal values o delay speads o vaous ypes o ean: 0.2 B Delay spead gues a 900 MHz B 0.02 Uban 1.3 Delay n moseonds Uban, wos-ase Sububan, ypal Sububan, exeme Indoo, maxmum 0.27 Delay Spead a 1900 MHz Buldngs, aveage Buldngs, wos - ase 1.47

34 Channel Classaon Based on Tme-Speadng Fla Fadng 1. B S < B C T m < T s 2. Raylegh, Rean dsb. 3. Speal haa. o ansmed sgnal peseved Fequeny Seleve 1. B S > B C T m > T s 2. Inesymbol Ineeene 3. Speal haa. o ansmed sgnal no peseved 4. Mulpah omponens esolved Channel Sgnal Channel Sgnal B C B S eq. B S B C eq. C. D. Chaalambous e al

35 Fadng n Dgal Moble Communaons I B s >> B, hen a noh appeas n he speum. Thus esulng n ne-symbol neeene (ISI). - To oveome hs, an adapve equalse (AE) wh nvese esponse may be used a he eeve. Tanng sequenes ae ansmed o updae AE. I B s << B, hen la adng ous, esulng n a bus o eo. - Eo oeon odng s used o oveome hs poblem.

36 Fequeny Dspeson Caused by he delay spead o he hannel Has no elaon o he veloy o he anenna Typal sample o mpulse esponse h() I we ansm a pulse () we eeve h() Delay pole: PDF o eeved powe: "aveage h 2 ()" Loal-mean powe n delay bn s p ()

37 Mulpah Delay Spead Fs-aval delay (τ A ) Mean exess delay e ( A) P( ) d

38 Mulpah Delay Spead The sandad devaon o he dsbuon o mulpah sgnal ampludes s alled delay spead. Fo deve anenna s haaezed by he ms delay spead o he ene delay pole, whh s dened as: whee avg = Σ j P j j, j s he delay o he j h delay omponen o he pole P j = (powe n he j h delay omponen) / (oal powe n all omponens Delay spead vaes wh he ean wh ypal values o ual, uban and sububan aeas: 3.0ms uban 0.5ms sububan 0.2ms ual 2 ( 2 ms P j j j avg ) 2

39 Typal Values o Delay Spead Poells GHz: T RMS < 50 nse nse Home 50 nse Shoppng mall nse Ralway saon nse Oe blok nse Indoo: oen 50 nse s assumed DECT (1 Mb/s) woks well up o 90 nse Oudoos, DECT has poblem ange >

40 Mulpah Delay Spead - Dspeson The delay spead lms he maxmum daa ae: No new mpulses should ave a he eeve beoe he las epla o he pevous mpulse has peshed. Ohewse symbol speads (dspeson) no s adjaen slo, hus esulng n Ine Symbol Ineeene (ISI) Tansmed symbols Reeved symbols The sgnal aved a he eeve dely and phase shed Dsoed sgnal dependng on he phases o he deen pas

41 Mgaon Tehnques o he Mulpah Fadng Channel Spae dvesy Sgnals a he same equeny usng wo o hee anennas loaed seveal wavelenghs a pa. Anennas ae onneed o wo o hee ado eeves. The eeve wll he songes sgnal s eleed Dsadvanage: Uses wo o moe anennas, heeoe he need o a lage se. Fequeny dvesy Sgnals a deen equenes eeved by he same anenna vey aely ade smulaneously. Thus he use o seveal ae equenes o he use o a wdeband sgnal o omba adng. A sngle aeal onneed o a numbe eeve, eah uned o a deen equeny, whose oupus ae onneed n paallel. The eeve wh he songes nsananeous sgnal wll povde he oupu. Dsadvanage: Uses wo o moe equenes o ansm he same sgnal.

42 Mgaon Tehnques o he Mulpah Fadng Channel Tme dvesy Spead ou he ees o eos hough neleavng and odng Mulpah dvesy Consde he apped delay lne model o a hannel shown pevously I mulpahs an be pu ogehe oheenly a he eeve, dvesy mpovemen esuls Ths s wha he RAKE eeve does (see nex vewgaph)

43 RAKE Mulpah Sgnal Poessng R.E. Zeme 2002

44 Sysem Desgn and Peomane Pedon Base saon plaemen dependen on Popagaon envonmen Anpaed geogaph dsbuon o uses Eonom onsdeaons (mnmze numbe o base saons) Polal and publ opnon onsdeaons Ta ypes (3G) Peomane gue o me Speum eeny o voe: η v voe us/mhz/base saon Speum eeny o nomaon: η bps/mhz/base saon Dopped all ae aon o alls ended pemauely

45 Summay The andom luuaons n he eeved powe ae due o adng. I hee s a elave moon beween ansme and eeve (moble) he esul s Dopple sh I maxmum Dopple sh s less han he daa ae, hee s slow adng hannel. I maxmum Dopple sh s lage han he daa ae, hee s as adng hannel.

46 Quesons and Answes Tell me wha you hnk abou hs leue Nex leue: Modulaon Tehnques

calculating electromagnetic

calculating electromagnetic Theoeal mehods fo alulang eleomagne felds fom lghnng dshage ajeev Thoapplll oyal Insue of Tehnology KTH Sweden ajeev.thoapplll@ee.kh.se Oulne Despon of he poblem Thee dffeen mehods fo feld alulaons - Dpole