LTE-Planning Sec04 100509 v01

OFDM/OFDMA and LTE Concepts

OFDM/OFDMA AnD LTE COnCEpTs

© Ima Telems & Meia

OFDM/OFDMA and LTE Concepts

ThE LTE LTE RADiO R ADiO inTERFA inTERFACE CE InTroducTIon To oFdM/oFdMA reqiemets  Me cmmiati Systems chael Bawith a Faig Flat Faig a Feqey Seletive Faig deig nawba a Wieba chaels cheee Bawith Mlti-caie Slti oFdM Basi Piiples Sb caie othgali othgality ty dpple Shit i rai chaels cheee Time cyli Pex/Ga Time Peak-t-Aveage Pwe rati (PAPr) Sigle caie – Feqey divisi Mltiple Aess (Sc-FdMA) LTE PHY Laye Paametes LTE Sb-caie Spaig LTE Timig a Famig Fame Type 2, Tdd   The rese Blk cmpais  rese Blks, chael Size a Samplig rate LTE chaels a chael Mappig LTE Lgial chaels LTE Taspt chaels LTE Physial chaels

4 4 6 6 8 10 12 14 16 18 18 20 22 24 28 28 30 32 34 36 38 40 42 44

© Ima Telems & Meia

OFDM/OFDMA and LTE Concepts

ThE LTE LTE RADiO R ADiO inTERFA inTERFACE CE InTroducTIon To oFdM/oFdMA reqiemets  Me cmmiati Systems chael Bawith a Faig Flat Faig a Feqey Seletive Faig deig nawba a Wieba chaels cheee Bawith Mlti-caie Slti oFdM Basi Piiples Sb caie othgali othgality ty dpple Shit i rai chaels cheee Time cyli Pex/Ga Time Peak-t-Aveage Pwe rati (PAPr) Sigle caie – Feqey divisi Mltiple Aess (Sc-FdMA) LTE PHY Laye Paametes LTE Sb-caie Spaig LTE Timig a Famig Fame Type 2, Tdd   The rese Blk cmpais  rese Blks, chael Size a Samplig rate LTE chaels a chael Mappig LTE Lgial chaels LTE Taspt chaels LTE Physial chaels

4 4 6 6 8 10 12 14 16 18 18 20 22 24 28 28 30 32 34 36 38 40 42 44

© Ima Telems & Meia

OFDM/OFDMA and LTE Concepts

chael Mappig Mappig chaels t the rese Blk chael Mappig  a 10MHz chael uplik Mappig  Physial chaels uplik Mappig  the ctl chael oveall Pite  uL Mappig Physial chaels a Mlati Shemes Syhisati a reeee Sigals Pimay a Seay Syh Seqees PSS a SS i the Fame Stte reeee Sigals LTE reeee Sigals dL cell Spei rS dL uE Spei rS uL uE Spei rS demlati reeee Sigals (dM rS) Sig reeee Sigals (SrS) Mlati, chael cig a Lik Aaptati chael cig HArQ (Hybi Atmati reqest) reptig  uE Feebak Pwe ctl i LTE   The use Plae a ctl Plae Ptls

© Ima Telems & Meia

46 48 50 52 54 56 58 60 62 64 68 70 72 74 76 76 78 80 84 86 88 90 92

OFDM/OFDMA and LTE Concepts

inTRODuCTiOn TO OFDM/OFDMA Reqremet o Moder Commcato sytem reet xe a mbile baba statistis sggest that the ema  ata is ieasig at a eve aeleatig ate. Sevies sh as Faebk, Ytbe a the Web 2.0 type appliatis have taitially bee aesse m xe baba etis, hweve with the isig pplaity  the smat phe, these appliatis ae mvig switly i t the mbile mai.  This pts pesse  the peats  mbile etwks t ese thee is siet apaity  the existig vie ta as well as all the ew mltimeia a sial etwkig appliatis.  The ema  high apaity makes the ai egiee lk t the ai hael t  aitial apaity. I eet yeas the bawith  the hael has gw sigiatly m 200KHz GSM t 5MHz uMTS/HSPA a the mlati a ig shemes have gw steaily me mplex a eiet. Give the et bawith a mplexity  systems like HSPA it wl be ilt t gai me apaity by simply ieasig the hael bawith witht makig the tehlgy phibitively mplex.

4

© Ima Telems & Meia

Fg. 1 – Web 2.0 – A Drver or hger Commcato seed? © Ima Telems & Meia

5

OFDM/OFDMA and LTE Concepts

Cael Badwdt ad Fadg  The ge ppsite illstates a typial ba evimet thgh whih ai sigals ppagate.  The tasmissi  the sigal m the se t the estiati is aie ve mltiple paths.  The mai eas  this is the existee  the biligs, vehiles, a the bstales whih a efet a satte the tasmitte sigal. The eeive sigal is a smmati  all these sigals m ieet paths. It is appaet that ay eeive will be sbjet t mltiple, time shi te pies  the same sigal.

Flat Fadg ad Freqecy selectve Fadg Eah  these paths expeiees a ieet dpple shit a egee  atteati. The eqey espse is the epesetati i the eqey mai  the spepsiti  all these paths. With the mltipath seai, whee the tasmitte sigals take plae ve ieet paths, the sigals eeive m eah path will a p at the eeive ipt  The pwe  the eeive sigal will vay as it is epeet p the elatiship betwee the phases  eah eeive mpet; whethe the eslt is sttive  esttive aiti  the phase vales. This is geeally kw as aig I the tasmitte hael is sietly aw the all the eqey mpets tasmitte i the hael will be atteate by the same amt, this is kw as fat aig  The piiple pblem with ieasig the bawith  the hael t ammate highe apaity is that the hael bemes ieasigly likely t se m eqey seletive aig. This is whee ly a pat  the veall tasmitte spetm ses m the atteati e t mltipath aig.

6

© Ima Telems & Meia

a) Tycal Mltat Evromet  Transmitter

Receiver

b) Flat Fadg Expected signal  Actual signal

    r     e     w     o       P

Frequency

c) Freqecy selectve Fadg Expected signal  Actual signal

    r     e     w     o       P

Frequency Fg. 2 © Ima Telems & Meia

7

OFDM/OFDMA and LTE Concepts

Defg narrowbad ad Wdebad Cael Whethe a hael is etemie t be wie  aw ba epes  the elative magite  the symbl time a the elay spea haateisti  the hael evimet. Tempal istti  the sigal is a eet  the mltipath evimet asig the same symbl t be eeive mltiple times ve a pei  time. The time ieees ae e t the ieig ppagati elays expeiee  ieet paths.  Typial  T ypial elay speas s peas  i a a  t evimets ae shw belw. be lw. I – 40S – 20S; 12m – 60m ot – 1S – 20S; 300m – 6Km  A hael a be sai t be aw ba whe the symbl time (Ts) is sigiatly lage tha ay elay spea peset (T) naw ba – Ts > T Hweve i the elay spea is sigiatly lage tha the symbl time the the hael may be siee wieba. Wieba – T > Ts Fllwig  m the isssi abve, egaig fat a eqey seletive aig, it a be sai that a hael that is ee as wieba, it is me likely t se m eqey seletive aig. csie w, that the symbl time is a ti  the hael bawith. ba with.  Ts = 1/Bw  Theee as the hael bawith ieases the symbl time will eease. e.g. Bw = 1MHz; Ts = 1S Bw = 1 10M 0MHz; Hz; Ts = 0.1S 0.1S It is me pbable theee that high apaity, high bawith ai haels will expeiee eqey seletive aig.

8

© Ima Telems & Meia

idoor Delay sread Transmitter

Receiver

RMs Delay sread t0 t1 t2 t3

    r     e     w     o       P

t4 t5

 Time RMS delay spread

narrowbad or WdeBad?  Ts  T s

 Td

Narrow band ~ Ts > Td Wideband ~ Td > Ts

Fg. 3 © Ima Telems & Meia

9

OFDM/OFDMA and LTE Concepts

Coerece Badwdt cheee bawith is a statistial mease  the age  eqeies ve whih the hael a be siee “fat” (i.e., a hael whih passes all spetal mpets with appximately eqal gai a liea phase). I the ws, heee bawith is the age  eqeies ve whih tw eqey mpets have a stg ptetial  amplite elati. cheee bawith is a ti  the elay spea evimet a a be allate sig the llwig expessi; B =

1 2πτms

Whee; τms is the ms elay spea  the hael.  The table belw shws typial elay speas  vais evimets a thei heee bawith. Kwig the heee bawith  typial eplymet evimets allws a estimati  the pbability that eqey seletive aig will  i the hael bawith  the system is kw k w..

10

Evromet

Tycal rm Delay

Coerece Badwdt

Hilly aea

3-10 μse

53KHz-16KHz

u ba 

1-3 μse

160KHz-53KHz

Sbba

< 1 μse

> 160KHz

ope aea

< 200 se

> 795KHz

Is

10-50 se

16MHz-3.2MHz

© Ima Telems & Meia

Coherence bandwidth is a statistical measure o the range o requencies over which the channel can be considered “fat” (i.e., a channel which passes all spectral components with approximately equal gain and linear phase)

Bc =

1 2πτrms

Evromet

Tycal rm Delay

Coerece Badwdt

Hilly aea

3-10 μse

53KHz-16KHz

uba

1-3 μse

160KHz-53KHz

Sbba

< 1 μse

> 160KHz

ope aea

< 200 se

> 795KHz

Is

10-50 se

16MHz-3.2MHz

Fg. 4 – Coerece Badwdt © Ima Telems & Meia

11

OFDM/OFDMA and LTE Concepts

Mlt-Carrer solto Give the pblems tlie abve the slti  tay’s baba wieless systems is t tilise mlti-aie systems kw as oFdM (othgal Feqey divisi Mltiplexig)  oFdMA (othgal Feqey divisi Mltiple Aess).

FDM (Freqecy Dvo Mltle Acce) Mlti-aie systems split the high spee steam  seial baseba ata i t lwe spee paallel steams. The lwe bit ate  eah sb-aie eslts i a awe ai hael that is esistat t the eqey seletive ae. OFDM (Ortogoal Freqecy Dvo Mltlexg) Hweve, these mlti-aie systems ee t exhibit g spetal eiey, eah sb aie mst be plae lse t its ajaet aie with t asig iteeee. The hael spaig is 1/Ts whee Ts is the symbl time  imati mlate t the aie. Spaig the haels i this mae eses that the ete  eah aie esps with a ze ssig pit  eah  the eighbig sb-aies. This meas that the ete  the sb-aies a be sample, ee m iteeee  the ajaet sb-aies.

12

© Ima Telems & Meia

Tradtoally saced FDM Cael t1

t2

t3

t4

t5

t6

Ortogoally saced FDM Cael (b-carrer)

1/Ts

Fg. 5 © Ima Telems & Meia

13

OFDM/OFDMA and LTE Concepts

OFDM Bac prcle  The blk iagam ppsite shws the basi piiple  a oFdM tasmitte/eeive. The imig ata steam is st vete m seial ata t paallel ata, the mbe  paallel ata steam will epe  the bawith  the veall hael a the mbe  sb-aies available t ay the ata. Eah  the paallel steams  ata is the mlate  t eah sb aie whih the eges a IFFT (Ivese Fast Fie Tasm) whih tasms the eqey mai sigal it a tme mai sigal. The mplex time mai sigal is the ae t pe a mpsite a mplex wavem. I eeive the sigal mst be sample with siet eqey t ese all the mpsite eqey mpets ae apte. Whee thee ae me sb-aies the eeive sigal mst be sample me eqetly.  The tem FFT (Fast Fie Tasm) pits  samples, ees t the mbe  samples that mst take plae ig a sige FFT symbl, hee the lage mbe  FFT pits  highe bawith haels. The FFT symbl has a time eqivalet t the baseba symbl time bt is the mpsite  all the mlate sb-aies. The apte a sample sigal is tasme t the eqey mai by applyig a FFT. This eetively sepaates the sb-aies s they may be emlate iepeetly.

14

© Ima Telems & Meia

Fg. 6 – smle OFDM Block Dagram © Ima Telems & Meia

15

OFDM/OFDMA and LTE Concepts

sb Carrer Ortogoalty Give the vey tight spaig  the sb-aies  the oFdM hael it is vey imptat that the sb-aies emai thgal m eah the. distbaes i the time a eqey mai a ee the thgality  the aies esltig i a iease i BEr a geeally pe pemae. distti i the eqey mai a me m dpple shit e t uE mvemet  m p syhisati  the uE sb systems t the system lk. The latte pblem a be eslve by havig the enB baast syhisati sigals  a egla basis, allwig the uE t ajst a maitai its syhisati with the enB. This a als ee the eet  dpple shit, hweve the heee time  the hael will pvie a iiati  hw likely the eeive sigals will be aete by dpple shit.

16

© Ima Telems & Meia

Demodulated signal without frequency offset (zero ICI)

Demodulated signal with frequency offset causing ICI

Fg. 7 – sb Carrer Ortogoalty © Ima Telems & Meia

17

OFDM/OFDMA and LTE Concepts

Doler st  Rado Cael Feqey set is a imptat sieati, patilaly i oFdM systems. I mbile ai systems the velity  the uE will ase a appaet set m the ete aie  the ai hael, yielig pe pemae a highe BEr. I oFdM systems it will als ase ite sb-aie iteeee.  The llwig expessi may be se t etemie the eqey set e t dpple shit.   = sθ.

.υ 

Whee;  is the eqey  peati v is the velity  the eeive  is the spee  light

Coerece Tme  A imptat pemae attibte whe sieig the systems sesitivity t eets  eqey set is the heee time. The heee time is a ti  the amt  eqey set peset i the hael a is ee as;  The time ve whih a hael a be assme t be stat.  T =

9

√ 16π. 

2



2

 Theee a system that ses a symbl time whih is less tha the heee time will t be istte by the eets  dpple shit. e.g. Fi the heee time  a ai hael peatig at 2.6GHz a a mbile tavellig at 140kph. The agle  aival is 0 140kph = 38 m/s   = sθ.

2.6 x 109 . 3.8 3 x 108

  = 329.33 Hz  T =

9

√16π.329.33

2

2

  = 1.28 x 10-3 ses

18

© Ima Telems & Meia

Coerece Tme The time over which a channel can be assumed to be constant

Doler st  Rado Cael

Fg. 8 © Ima Telems & Meia

19

OFDM/OFDMA and LTE Concepts

Cyclc prefx/Gard Tme  The mlti-path evimet thgh whih the ai sigals ae tasmitte eate tempal isttis i the ata aie by the ai hael. The ieig ppagati ati  eah  the mlti-path mpets eate ite-symbl iteeee (ISI). Ite-symbl iteeee i oFdM systems at be tleate sie it ees the thgality betwee the sb-aies a ieases the BEr a ees pemae  the hael. All  the imati imptat t the FFT (Fast Fie Tasm) is taie withi the symbl time theee it is itial that thee is  istti ig this pei. Sie the ISI at be elimiate m the hael, the imati mst be ptete m its eet. The slti i oFdM systems is t exte the legth  eah symbl by a at eqivalet t the likely elay spea i the hael. This extesi t the symbl is kw as the yli pex (cP)  ga time.  The cP, whih appeas at the begiig  eah symbl a is atally a py  the last pat  that symbl. The ilsi  the ga pei elimiates the eets  mlti-path ISI at the expese  thgh pt, sie the cP aies  atal imati a is isae at the eeive e the rF sigal has bee sesslly igitise.

20

© Ima Telems & Meia

Creato o te Cyclc prefx

 T cp = 4.7µ S

Symbol = 66.7µS

 Total T ransmi tted Symbo l = 71.3µS

Cyclc prefx Oerato CP A

 

CP A

A

CPB

 

CPB

B

CPC

A

CPC

C

B

 T d

Compete Symbol FF T Sampling Ti me

Fg. 9 © Ima Telems & Meia

21

OFDM/OFDMA and LTE Concepts

peak-to-Average power Rato (pApR) oFdM es peset sme tehial halleges. The esltig mpsite wavem isplays lage vaiatis i amplite ase by the mbiati  a mbe  iivial sigals.  This is illstate i Fige 11. The eet is simila t that ase by the mltipath evimet – a esltat sigal ftatig i amplite as a eslt  the mbiig  s may sigals with isete phase a amplite ieees.  This esltat mpsite sigal has impliatis  A t d vet a rF amplie esig.  The yami age  the amplie mst be able t pe with the smallest a lagest sigal amplites – patilaly the lagest amplite as it this that l ase ve-ivig  the amplie. ove ivig a amplie ases -liea behavi esltig i the geeati  hamis a Itemlati Pts (IPs) whih will esie withi the wate spetm, bt will ase wate eets. The FFT pess will be egae as it attempts t eal with eqey mpets that shl t be thee, esltig i l st pakets.

22

© Ima Telems & Meia

Symbol time 2

Symbol time 3

Symbol time 4

Carrier 1

Carrier 2

Carrier 3

Carrier 4

Composite signal

Fg. 10 – peak to Average power (pApR) © Ima Telems & Meia

23

OFDM/OFDMA and LTE Concepts

sgle Carrer – Freqecy Dvo Mltle Acce (sC-FDMA) 3GPP has hse Sc-FdMA  the plik. nt spisigly, pwe smpti is a key sieati  uE temials. The high PAPr a elate lss  eiey assiate with oFdMA ae maj es. As a eslt, a alteative t oFdM was sght  se i the LTE plik. Sc-FdMA is well site t the LTE plik eqiemets. The basi tasmitte a eeive ahitete is vey simila (ealy ietial) t oFdMA, a it es the same egee   mltipath pteti. Mst imptat thgh is that the elyig wavem is essetially sigle-aie, a theee the PAPr is lwe.  The ge ppsite mpaes the oFdMA a Sc-FdMA sttes. F laity this example ses ly  (M) sbaies ve tw symbl peis with the payla ata epesete by qaate phase shit keyig (QPSK) mlati. data symbls i the time mai ae vete t the eqey mai sig a isete Fie tasm (dFT); the i the eqey mai they ae mappe t the esie lati i the veall hael bawith bee beig vete bak t the time mai sig a ivese FFT (IFFT). Fially, the cP is isete. Bease Sc-FdMA ses this tehiqe, it is smetimes alle isete Fie tasm spea oFdM  (dFT-SoFdM).  The mst bvis ieee betwee the tw shemes is that oFdMA tasmits the  QPSK ata symbls i paallel, e pe sbaie, while Sc-FdMA tasmits the  QPSK ata symbls i seies at  times the ate, with eah ata symbl pyig M x 15 kHz bawith.

24

© Ima Telems & Meia

Q -1,1

1,1

1,1 -1,-1 -1,1 1,-1 -1,-1 1,1

Sequence of QPSK data symbols to be transmitted

I

-1,-1

1,-1 -1,1

1,-1

QPSK modulating data symbols

Constant subcarrier power during each SC-FDMA symbol period  V

  A   l    M   o    D    b    F   m   O   s  y

CP

  e    i  m    T

fc

V

Frequency

CP

  e    i  m    T

  A   l    M   o    D    b    F   O   y  m   s 15kHz

  A    M   l    D    F    b  o  -   m   C   S   s  y

fc

  A    M   l    D    F    b  o  -   m   C   y   S   s 60kHz

Frequency

OFDMA

SC-FDMA

Data symbols occupy 15kHz for one OFDMA symbol period

Data symbols occupy M*15kHz for 1/M SC-FDMA symbol periods

Fg. 11 – sgle Carrer – FDMA © Ima Telems & Meia

25

OFDM/OFDMA and LTE Concepts

Sc-FdMA sigal geeati begis with a speial pe-ig pess. The iagam ppsite shws the st steps, whih eate a time-mai wavem  the QPSK ata sb-symbls. usig the  l-e QPSK ata symbls m the pevis iagam, the pess eates e Sc-FdMA symbl i the time mai by mptig the tajety tae by mvig m e QPSK ata symbl t the ext. This is e at M times the ate  the Sc-FdMA symbl sh that e Sc-FdMA symbl tais M setive QPSK ata symbls. oe a IQ epesetati  e Sc-FdMA symbl has bee eate i the time mai, the ext step is t epeset that symbl i the eqey mai sig a dFT.  T mplete Sc-FdMA sigal geeati, the pess llws the same steps as  oFdMA. Pemig a IdFT vets the eqey-shite sigal t the time mai a isetig the cP pvies the ametal bstess  oFdMA agaist mltipath. The iagam ppsite shws the stages i mm with oFdM.

26

© Ima Telems & Meia

Geeratg te sC-FDMA sgal Q

 V(I)

-1,1

1,1

 V(I)

+1

+1

–1

–1

I

-1,-1

1,-1

One SC-FDMA symbol period

One SC-FDMA symbol period

Te sC-FDMA Block Dagram Unique to SC-FDMA

  a  n    t   a   i   s    d   t    i    b    M

Map data to constellation

Generate time domain waveform

Common with OFDMA

Perform M-point DFT (time to freq)

 Time domain

  a   t   u    t   a  o    d  s    t    i    M    b

De-map constellation to data

Generate constellation

Map symbols to subcarriers

Frequency domain

Perform M-point IDFT (time to freq)

De-map subcarriers to symbols

Perform N-point IFFT N >M

Upconvert and transmit

Time domain

Perform N-point DFT N >M

Receive and downconvert

Fg. 12 © Ima Telems & Meia

27

OFDM/OFDMA and LTE Concepts

LTE phY Layer parameter LTE is esige t meet may ieig eqiemets ilig ba, sbba, i a t evimets as well as pig with may ieet mbility itis m statiay t high spee mbility p t 500Kph. cell sizes may als vey m emt t lage al ma.  The age  spetm that LTE may be ptetially eply ass is als vey wie, 400MHz – 4GHz, the eplye system bawiths that may be sppt als ages m 1.4MHz t 20MHz. Give the eplymet fexibility  LTE the age  hael itis that it is expete t pem e is extemely wie a vaie. The itial paametes eqie t sppt this ivesity ae the sb-aie spaig a the yli pex.

LTE sb-Carrer sacg  The sb-aie spaig is 15KHz. csie the pevis isssis  heee bawith a esiliee t dpple eets, seleti  sb aie spaig  15KHz  LTE ai iteae is a mpmise base  the expete peatial evimet a expete levels  pemae.

28

© Ima Telems & Meia

Channel spacing = 1/Ts  Ts = 66.7µS Fs = 1/66.7µS = 15KHz

Fg. 13 – LTE sb-Carrer sacg © Ima Telems & Meia

29

OFDM/OFDMA and LTE Concepts

LTE Tmg ad Framg  The basi it  time i LTE is Ts, this is ee as 1/(15000*2408) = 32.56S, whee 15000 is the bawith  the sb-aie a 2048 is the maximm mbe  FFTs sppte. Evey elemet  time is sme mltiple  this vale.  The ge ppsite shws the type 1 ame,  Fame Stte 1 (FS1), this is the timig stte se  the plik a wlik  the Fdd (Feqey divisi dplex) haels. oe slt is a 0.5mS pei  time whih tais 7 symbls  66.67 µS. 2 slts make p e 1mS Sb-Fame, the sb-ame is smetimes eee t as the tasmissi time iteval (TTI) patilaly by the highe layes. Thee a 10 sb-ames  20 slts i e 10mS ame.  This stte is se i the time mai t map the physial haels. nte that the physial haels als eqie a eqey mai mpet  mplete mappig.

30

© Ima Telems & Meia

One radio frame, Tf  = 307200, Ts = 10 ms One slot, Tslot = 15360, Ts = 0.5 ms

#0

#1

#2

#3

#18

#19

One subframe

0 1 2 3 4 5 6 66.67µS Symbols

Fg. 14 – Frame Tye 1 FDD © Ima Telems & Meia

31

OFDM/OFDMA and LTE Concepts

Frame Tye 2, TDD  The ge ppsite shws the ame stte se  a Tdd (Time divisi dplex) hael. It has simila veall timig i.e. the veall ame legth is 10mS a 10 sb-ames  1mS eah. Hweve the stte  the sb-ames is i eet. I the FS2 the sb-ame allws bth a plik a wlik tasmissi/eepti pptity.  These ae eee t as the dwPTS (dwlik Pilt Time Slt) a upPTS (uplik Pilt Time Slt), these ae sepaate i the sb-ame by a ga pei (GP).  The ame has tw ieet swith pits i.e. the pit at whih a ee slt gati begis t epeat, these ae at 5mS a 10mS. I aiti thee ae 7 ieet ame gatis. I ay  these gatis sb-ame 0 a 6 ay wlik imati ly, a sb-ame aies plik ly. The table ppsite shws the ame gatis.

32

© Ima Telems & Meia

Cofgrato swtc-ot erodcty

sb-rame mber 0

1

2

3

4

5

6

7

8

9

0

5 ms

d

S

u

u

u

d

S

u

u

u

1

5 ms

d

S

u

u

d

d

S

u

u

d

2

5 ms

d

S

u

d

d

d

S

u

d

d

3

10 ms

d

S

u

u

u

d

d

d

d

d

4

10 ms

d

S

u

u

d

d

d

d

d

d

5

10 ms

d

S

u

d

d

d

d

d

d

d

6

10 ms

d

S

u

u

u

d

S

u

u

d

Fg. 15 – Frame Tye 2 TDD © Ima Telems & Meia

33

OFDM/OFDMA and LTE Concepts

Te Reorce Block Mappig  haels takes plae i the time a eqey mais i LTE. The pimay elemet that sppt the mappig pess is the rese Blk (rB). The rB has a xe size a is mm t all hael bawiths/FFT sizes. I the time mai the rB is e slt ( 7 x 66.67µS symbls). I the eqey mai thee ae 12 x 15KHz sb-aies. 1 symbl a 1 sb-aie is kw as a ese elemet. Fm the ge ppsite it a bee see that the rB pies 12 x 15KHz = 180KHz  ba with. I a 5MHz ai hael thee will be 300 rB pyig 4.5MHz  spetm. The mbe  FFTs eqie t pess this is 512, assmig sb-aie size  15KHz, 512 x 15KHz = 7.68MHz. 7.68MHz i the spae pie by 512 FFT pits a is t the tasmitte bawith, 7.68MHz is als the samplig eqey eqie t eve imati m the aie t ive the FFT (time mai t eqey mai) i the eeive.

34

© Ima Telems & Meia

1 slot   s   o   r   e    Z

DL or UL symbol

Resource block    )   z    H    k    0    8    1    (    2    1   =

  y   c   n   e   u   q   e   r    F

   B    R   c   s

   N

   )   z    H    M    5  .    4    (    0    0    3   =

   B    R   c   s

   N   x

   B    R

   )   z    H    M    8    6  .    7    (    2    1    5   =    M

   N

  s   o   r   e    Z

 Time

*5 MHz system with frame structure type 1

Fg. 16 – Defg a Reorce Block © Ima Telems & Meia

35

OFDM/OFDMA and LTE Concepts

Comaro o Reorce Block, Cael sze ad samlg Rate  The table ppsite shws the mbe  rB eqie  hael bawiths sppte by LTE, it shl be te that the eiti  hael bawith i this table ees t the mial hael size ee by the spetm eglatig by, it is t eessaily the tasmissi bawith. Sie eah rB tais 12 sb-aies the mbe  pie sb-aies a be etemie, mltiplyig the mbe  pie sb-aies by 15KHz will me aately esibe the tasmissi bawith  the vais ptis.  The IdFT/dFT (Ivese diseet Fie Tasm) esibes the mbe  FFT pits eqie t sesslly eve imati m the aie, it is always a vale  2 a etemies the mbe  steps  pesses eqie t stt/e-stt the mpsite oFdMA sigal.  The samplig ate a samples pe slt ae etemie m the FFT mbe a the sb-aie  bawith. E.g. i the 5MHz hael the samplig ate  7.68MHz wl eslt i 3840 samples evey 1mS.

36

© Ima Telems & Meia

chael bawith (MHz)

1.4

3

5

10

15

20

nmbe  ese blks (n rB)

6

15

25

50

75

100

nmbe  pie sbaies

72

180

300

600

900

1200

IdFT(Tx)/dFT(rx) size

128

256

512

1024

1536

2048

Sample ate (MHz)

1.92

3.84

7.68

15.36

23.04

30.72

Samples pe sht

960

1920

3840

7680

11520

15360

Fg. 17 – Table o Reorce Block sze ad Cael Badwdt © Ima Telems & Meia

37

OFDM/OFDMA and LTE Concepts

LTE Cael ad Cael Mag Imati, bth sigallig a se, is tasmitte thgh the ptl stak a ve ai sig haels. Thee ae 3 basi types  hael ee, Lgial, Taspt a Physial haels. Eah hael is ee by a set  tis  attibtes whih etemies the halig  the ata ve the ai iteae.

Logcal Cael Lgial chaels exist betwee the PdcP laye a MAc, they ae piipally ee by the type  imati that they ay. Thee ae lgial haels that ay tl ata, a lgial haels that ay se ta. Traort Cael  Taspt chaels exist betwee the MAc laye a the Physial Laye a ae ee the mae i whih the ata will be tasee, i.e. the type  hael ig, whethe the ata is ptete m es, size  ata pakets, et. The attibtes  ata tase applie t the ata i the taspt hael is thewise kw as the taspt mat. pycal Cael Physial chaels ae the atal implemetati  the taspt haels i the physial laye.  The ly exist i the physial laye a epe  the physial laye haateistis, i.e. hael bawith, FFT size, et.

38

© Ima Telems & Meia

 Traffic channel

MAC

PHY

Control channel

Logical channels Defined by Type of information i.e. traffic, control, e.g. BCCH, PCCH, CCCH, MCCH, DCCH

Transport channels Defined by Transport attribute i.e. channel coding, CRC, interleaving, size of radio data packets, e.g. BCH, PCH, DL-SCH, MCH

Physical channels Defined by actual physical layer characteristics, bandwidth, FFT size, e.g. PDSCH, PDCCH, PMCH, PBCH…

Fg. 18 – LTE Cael © Ima Telems & Meia

39

OFDM/OFDMA and LTE Concepts

LTE Logcal Cael  Thee ae tw types  lgial hael, tl haels a ta haels, they ae esibe belw.

Cotrol Cael ctl haels ae se  tase  tl plae imati ly. The tl haels ee by MAc ae: Broadcast Control Channel (BCCH)  A wlik hael  baastig system tl imati. Imati baast  this hael is shae by all the ses i the ell, the imati baast elates t the opeat ietity, ell gati, aess imati et Paging Control Channel (PCCH)  A wlik hael that tases pagig imati. This hael is se whe the etwk es t kw the lati ell  the uE. Common Control Channel (CCCH) chael  tasmittig tl imati betwee uEs a etwk. This hael is se  uEs havig  rrc eti with the etwk. It wl be se ig the ealiest phases  mmiati establishmet. Multicast Control Channel (MCCH)  A pit-t-mltipit wlik hael se  tasmittig MBMS tl imati m the etwk t the uE,  e  seveal MTcHs. This hael is ly se by uEs that eeive MBMS. Dedicated Control Channel (DCCH)  A pit-t-pit bi-ietial hael that tasmits eiate tl imati betwee a uE a the etwk. uEs havig a rrc eti will exhage rrc a nAS sigallig, it shl be te that appliati level sigallig (SIP messages m the IMS) is t hale by the dccH. Trafc Cael  Ta haels ae se  the tase  se plae imati ly. The ta haels ee by MAc ae: Dedicated Trafc Channel (DTCH)  A deiate Ta chael (dTcH) is a pit-t-pit hael, eiate t e uE,  the tase  se imati. The dTcH will als ay sigallig m the appliati layes, this may be SIP a rTSP sigallig i the EPc sppts IMS (IP Mltimeia Sbsystem) Multicast Trafc Channel (MTCH)  A pit-t-mltipit wlik hael  tasmittig ta ata m the etwk t the uE.  This hael is ly se by uEs that eeive MBMS.

40

© Ima Telems & Meia

LTE Logical Channels

Logical Control Channels

Broadcast Control Channel (BCCH) System Information Messages •

Paging Control Channel (PCCH) Paging Messages, UE Location not known

Logical Trafc Channels

Dedicated Traffic Channel (DTCH) Point-Point bi-directional channel, User data and application level signalling (SIP) •

•

Multicast Traffic Traffic Channel (MTCH) Point-Multi-point channel supporting data transfer for the MMBS service •

Common Control Channel (CCCH) Early communication, no RRC connection •

Multicast Control Channel (MCCH) Multicast control signalling •

Dedicated Control Channel (DCCH) Bi-Directional signalling, RRC connection, RRC and NAS Signalling •

Fg. 19 – LTE Logcal Cael © Ima Telems & Meia

41

OFDM/OFDMA and LTE Concepts

LTE Traort Cael  Taspt haels ae lassie i t plik a wlik haels a ae esibe belw.

Broadcat Cael (BCh)  The BcH has a xe a pe-ee taspt mat lagely ee by the eqiemet t be baast i the etie veage aea  the ell sie the imati aie by this hael tais system imati. Dowlk sared Cael (DL-sCh ( DL-sCh))  This hael will ay wlik sigallig a ta a may have t be baast i the etie ell, give the ate  the ata i this hael it will als sppt  bth yami a semi-stati ese allati with the pti t sppt  uE istis eepti (drX) t eable uE pwe savig, E tl is sppte i this hael by meas   HArQ a yami lik aaptati by vayig the mlati, ig a tasmit pwe. Spetal eiey a als be iease e t the pssibility  sig beammig atea tehiqes. The hael als sppts MBMS tasmissis. pagg Cael (pCh)  This hael is assiate with the PccH a will ay pagig message t uEs t etly ete t the etwk. The PcH sppts istis eepti (drX) t eable uE pwe savig whee the sleep yle is iiate by the etwk t the uE. The PcH may als have t be baast i the etie veage aea  the ell. The PcH is als mappe t physial eses whih a be se yamially als  ta/the tl haels. Mltcat Cael (MCh)  The hael is assiate with the mltiast sevies m the ppe layes a as sh thee is a eqiemet t baast bth tl a se ata ve the etie veage aea  the ell. It als sppt the Sigle Feqey netwk as semi-stati ese allati ulk sared Cael (uL-sCh)  The uL_ScH aies mm a eiate sigallig as well as eiate ta imati. It sppts the same eates as the dL dL-ScH. -ScH. Radom Acce Cael (RACh)  The rAcH is a vey spei taspt hael, it aies limite tl imati ig the vey ealiest stages  eti establishmet. This a mm plik hael theee thee is the isk  llisis ig uE tasmissi.

42

© Ima Telems & Meia

LTE Transport Channels

Downlink Transport Channels

Broadcast Channel (BCH) xed, pre-dened transport format; broadcast in the entire coverage area of the cell. • •

Downlink Shared Channel (DL-SCH) HARQ; dynamic link adaptation by varying the modulation, coding and transmit power; broadcast in the entire cell; beamforming; dynamic and semi-static resource allocation; UE discontinuous reception (DRX) to enable UE power saving; MBMS transmission. • •

• •

Uplink Transport Channels

Uplink Shared Channel (UL-SCH) beamforming dynamic link adaptation by varying the transmit power and potentially modulation and coding; HARQ; dynamic and semi-static resource allocation. • •

• •

Random Access Channel (RACH) limited control information; collision risk; • •

•

•

•

Paging Channel (PCH) UE discontinuous reception (DRX) to enable UE power saving broadcast in the entire coverage area of the cell; mapped to physical resources which can be used dynamically also for trafc/other control channels. •

•

•

Multicast Channel (MCH) broadcast in the entire coverage area of the cell; MBSFN combining of MBMS transmission on multiple cells; support for semi-static resource allocation e.g. with a time frame of a long cyclic •

•

•

Fg. 20 – LTE Traort Cael © Ima Telems & Meia

43

OFDM/OFDMA and LTE Concepts

LTE pycal Cael  The physial haels ae the atal implemetatis  the taspt haels  the ai iteae. They ly exist withi the physial laye a ae highly epeat  the atal apabilities  the physial laye itsel.  The physial haels ae:

pycal broadcat cael (pBCh)  The system imati is tasmitte ylially withi BcH taspt blk a mappe t  sbames ve a 40 ms iteval, thee is miimal syhisati m the uE pespetive sie the 40 ms timig is blily etete, i.e. thee is  expliit sigallig iiatig 40 ms timig. Eah sbame is assme t be sel-eable, i.e. the BcH a be ee m a sigle eepti, assmig sietly g hael itis. pycal cotrol ormat dcator cael (pCFiCh)  This hael ims the uE abt the mbe  oFdM symbls se  the PdccHs a is tasmitte i evey sbame. pycal dowlk cotrol cael (pDCCh)  This hael ims the uE abt the ese allati  PcH a dL-ScH, a Hybi  ArQ imati elate t dL-ScH a als aies the plik shelig gat. pycal hybrd ARQ idcator Cael (phiCh) caies Hybi ArQ AcK/nAKs i espse t plik tasmissis. pycal dowlk ared cael (pDsCh) caies the dL-ScH a PcH. pycal mltcat cael (pMCh) caies the McH, Mlitast/Baast imati pycal lk cotrol cael (puCCh)  This hael aies plik tl imati sh as Hybi ArQ AcK/nAKs i espse t wlik tasmissi, aies Shelig reqest (Sr) a, cQI epts. pycal lk ared cael (pusCh) caies the uL-ScH, se ata a appliati level sigallig pycal radom acce cael (pRACh) caies the am aess peamble set by the uE t iitiate a rrc eti.  Thee ae als physial sigals whih ae set  the wlik bt ae t give ay hael esigati, they ile; • •

44

reeee sigals – e sigal tasmitte pe wlik atea pt Syhisati sigals – pimay a seay syhisati sigals.

© Ima Telems & Meia

LTE Physical Channels

Downlink Physical Channels

Physical broadcast channel (PBCH) BCH transport block is mapped to four subframes within a 40 ms blindly detected, there is no explicit signalling indicating 40 ms timing; the BCH can be decoded from a single reception. •

•

Uplink Physical Channels

Physical uplink control channel (PUCCH) Carries Hybrid ARQ ACK/NAKs ; Carries Scheduling Request (SR); Carries CQI reports. • • •

•

Physical control format indicator channel (PCFICH) Informs the UE about the number of OFDM symbols used for the PDCCHs; Transmitted in every subframe. •

•

Physical uplink shared channel (PUSCH) Carries the UL-SCH. •

Physical random access channel (PRACH) Carries the random access preamble. •

Physical downlink control channel (PDCCH) resource allocation of PCH and DL-SCH, and Hybrid ARQ information related to DL-SCH; Carries the uplink scheduling grant. •

•

Physical Hybrid ARQ Indicator Channel (PHICH) Carries Hybrid ARQ ACK/NAKs •

Physical downlink shared channel (PDSCH) Carries the DL-SCH and PCH. •

Physical multicast channel (PMCH) Carries the MCH. also for trafc/other control channels. • •

Multicast Channel (MCH) - broadcast in the entire coverage area of the cell; - MBSFN combining of MBMS transmission on multiple cells; - support for semi-static resource allocation e.g. with a time frame of a long cyclic

Fg. 21 – LTE pycal Cael © Ima Telems & Meia

45

OFDM/OFDMA and LTE Concepts

Cael Mag  The iagam ppsite shws the pssible mappig  haels betwee lgial, taspt a physial haels. It a be te that, whilst the lgial haels ay spei types  imati, they a be mappe t mm taspt haels a i the ase  the mltiast tl a ta haels ieet taspt haels a be se t ay the ata. I the ase  the BccH lgial hael, it will be te that bth the BcH a dL-ScH may be se t ay the system imati. This epes  the type  system imati beig tasmitte. citial system imati messages sh as thse that ay shelig imati a ee t be tasmitte  a egla basis ae tasmitte as a xe mat message via the BcH a PBcH. Mappig system imati t the dL_ScH allws sme fexibility a aitial apaity  less time epeat imati.  The rAcH hael aies ly the aess peamble a has  istae abve the MAc laye, theee the hael is t mappe t a lgial hael. oe a rrc eti has bee gate the rAcH is  lge se. Sme physial haels  t ay imati abve the physial laye theee have  taspt hael eqivalets. Examples ile PuccH, PdccH, PcFIcH, PHIcH, these ay imati elate t the ig  the physial blks a HArQ mehaism.

46

© Ima Telems & Meia

Logical PCCH

BCCH

CCCH

DCCH

DTCH

MCCH

MTCH

 Transport PCH

BCH

UL-SCH

DL-SCH

MCH

PUCCH PCFICH

RACH

Physical

PDCCH PHICH

PBCH

PUSCH

PDSCH

PMCH

PRACH

Fg. 22 – Logcal to Traort Cael Mag © Ima Telems & Meia

47

OFDM/OFDMA and LTE Concepts

Mag Cael to te Reorce Block  The ge ppsite shws the pess  mappig the wlik tl a shae haels t a ese blk. The syhisati a eeee sigals ae als ile. nte the PdccH s i the st ew symbls  eah sb-ame, the mbe  symbls is sigalle by the PHFIcH. Als te the aagemet  the pimay a seay syhisati sigals a the PBcH. Whe this imati is mappe t the 10mS ame it a be see that the P-ScH, S-ScH a PBcH ae tasmitte i sb-ame 1 a the P-ScH, S-ScH is tasmitte agai i sb-ame 5. This meas that pimay a seay syhisati sigals ae etasmitte evey 5mS. The PBcH is tasmitte with 40mS peiiity.

48

© Ima Telems & Meia

Fg. 23 – Mag o Dowlk Cotrol ad sCh pycal Cael to a Reorce Block © Ima Telems & Meia

49

OFDM/OFDMA and LTE Concepts

Cael Mag o a 10Mhz Cael  The ge ppsite shws the wlik mappig  a 10MHz hael. The syh a baast ata is late i the ete  the ba t ai the uE ell seah pess.

50

© Ima Telems & Meia

One radio frame = 10 ms

One subframe = 1 ms

Slot 0 0

1

2

3

4

Slot 1 5

6

0

1

2

3

4

Slot 2 5

6

0

1

2

3

4

Slot 10 5

6

0

1

2

3

4

Slot 19 5

6

0

1

2

3

4

5

6

0 1 2 3 4 5 6 7 8 9 10 11 RB  Ant 0 /   Ant 1 reference

258

• channel estimation • channel quality measurement

259 260 261 262 263 264 265 266 267

PDCCH

268

• DL scheduling decision • UL scheduling grants • ACK/NACK information

269 270 271 272 273 274 275 276 277

P-/S-SCH

278

• cell search • frequency and timing acquisition

279 280 281 282 283 284 285 286 287

PBCH

288

• broadcasting channel • cell specific information

289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306

595 596 597 598 599 600

Fg. 24 – Detaled pycal Cael Mag or 5Mhz Cael © Ima Telems & Meia

51

OFDM/OFDMA and LTE Concepts

ulk Mag o pycal Cael  The plik haels ae mappe i a simila ashi t the wlik, the biggest ieee hee beig the absee  sb-aies sie Sc-FdMA is se the ese blk tais 7 time mai symbls (1 slt) a a sigle Sc-FdMA hael.  The mappig  the plik shae hael is shw i the ge ppsite. nte the pesee  the plik eeee sigal i symbl 3  evey slt.

52

© Ima Telems & Meia

Fg. 25 – Mag o uL sared Cael to Reorce Block ad Frame © Ima Telems & Meia

53

OFDM/OFDMA and LTE Concepts

ulk Mag o te Cotrol Cael  The ge ppsite shws the mappig aagemet  the PuccH a its eeee sigals.  The PrAcH hael is als mappe it this sb-ame mat althgh its pesee a lati mst be sigalle by the etwk.

54

© Ima Telems & Meia

Fg. 26 – Mag o uL Cotrol Cael to Reorce Block © Ima Telems & Meia

55

OFDM/OFDMA and LTE Concepts

Overall pctre o uL Mag  The ge ppsite shws the geeal aagemet  mappig plik tl a shae haels ve time a eqey mais.

56

© Ima Telems & Meia

   e     m      i      T

Frequency n

PUSCH

n

Demodulation reference signal (for PUSCH)

n

PUCCH

n

Demodulation reference signal for PUCCH format 0 & 1

Fg. 27 – Detaled Mag o uL Data ad Cotrol Cael © Ima Telems & Meia

57

OFDM/OFDMA and LTE Concepts

pycal Cael ad Modlato sceme  Thee ae geeally 3 ieet types  imati tasmitte ve the ai lik, sigallig, ata a speial eeee sigals. Physial laye sigallig has the pimay eqiemet  eliability theee the mlati shemes sppte by the sigallig haels ae lw level “bst” shemes. QPSK is the mlati sheme se i mst ases althgh the PuccH has the pti  sig BPSK i imstae whee iteeee is vey high. data’s mai eqiemet is e  spee a spetal eiey. Mst appliatis beet m high ata tase ates a the etwk beets m high spetal eiey, theee the highest e mlati sheme wl geeally be selete, 64QAM, hweve thee ae times whe iteeee is high a the high e shemes at be maitaie, theee the shae haels als sppt 16QAM a QPSK.  The speial sigals ’t tasmit expliit imati, istea, mplex sigals whih imply a hael iti  psiti i mplex seqee geeati ae tasmitte. The sigals ae se by the uE a the enB t etemie hael itis  MIMo pessig a etwk syhisati. The rS, P-ScH a S-ScH all tasmit mplex ata seqees.

58

© Ima Telems & Meia

Te pycal Layer Cael o LTE DL cael

Fll ame

proe

PBcH

Physial baast hael

caies ell-spei imati

PMcH

Physial mltiast hael

caies the McH taspt hael

PdccH

Physial wlik tl hael

Shelig, AcK/nAcK

PdScH

Physial wlik shae hael

Payla

PcFIcH

Physial tl mat iiat hael

dees mbe  PdccH oFdMA symbls pe sb-ame (p t 4)

PHIcH

Physial hybi ArQ iiat hael

caies HArQ AcK/nAcK

uL cael

Fll ame

proe

PrAcH

Physial am aess hael

call setp

PuccH

Physial plik tl hael

Shelig, AcK/nAcK

PuScH

Physial plik shae hael

Payla

Te pycal Layer sgal o LTE DL gal

Fll ame

proe

P-ScH*

Pimay syhisati sigal

use  ell seah a ietiati by the uE. caies pat  the ell Id (e   thee thgal seqees)

S-ScH*

Seay syhisati sigal

use  ell seah a ietiati by the uE. caies the emaie  the ell Id (e  168 biay seqees)

rS

reeee sigal (pilt)

use  dL hael estimati. Exat seqee eive m ell Id (e   3 x 168 = 504) pse am seqees)

uL gal

Fll ame

proe

rS

reeee sigal (emlati a sig)

use  syhisati t the uE a uL hael estimati

Fg. 28 © Ima Telems & Meia

59

OFDM/OFDMA and LTE Concepts

sycroato ad Reerece sgal syc seqece ad Cell searc  A uE eteig a ell  the st time mst isve the time a eqey paametes that ae eqie t sesslly mmiate with the enB. I the ws the uE mst syhise with the enB. Syhisati sigals ae baast m the enB  a eqet basis that eable the time mai a eqey mai paametes t be ea by the uE, i aiti this imati a impat ell ietiati.  The eqiemets  syhisati a be empse it thee mai tis. 1. Symbl timig aqisiti, whee the et symbl stat psiti is ietie, t set the et FFT wiw psiti. 2. caie eqey syhisati, whih is eee t ee  elimiate the eet   eqey es aisig m the mismath  lal sillat t the tasmitte a eeive, als the eqey isttis aisig m tempeate it, ageig a dpple eets. 3. It is als eessay t have the samplig lk syhise.  The uE is eqie t pem ell seah eithe iitially whe eteig the system ate swith  a ietiyig a ew ell (i.e. eighb ell) e ete t the system.

60

© Ima Telems & Meia

1.

Symbol timing acquisition

2.

Carrier requency synchronisation

3.

Synchronised sampling clock

Fg. 29 – sycroato Reqremet © Ima Telems & Meia

61

OFDM/OFDMA and LTE Concepts

prmary ad secodary syc seqece  Thee ae 2 syh sigals tasmitte m the enB, the Pimay Syh Sigal (PSS) a the Seay Syh Sigal (SSS)  The PSS eables the uE t etet the slt timig a als pvies a physial laye ietity  the ell. The SSS pvies the ai ame timig, the ell Id, cyli Pex (cP) eteti a a iati  Tdd  Fdd. I the ell seah is  iitial ety i t the system the uE will etet PSS llwe by SSS the g  t  a ee the Baast imati i the ell, imati baast will elive the imptat ell paametes allwig the uE t miy its behavi aig t the selete ell. I the uE has aleay etee the etwk the eteti  ajaet ell PSS a SSS will be llwe by the eteti a measemet  the eighb ell sigal stegth a qality.

62

© Ima Telems & Meia

PSS Detection

Slot Timing PHY Layer ID

SSS Detection

Radio Frame Timing Cell ID CP Length Detection TDD/FDD Detection

Initial synchronisation

PBCH Decode

PBCH Timing Detection System Information Access

New cell identification

RS Detection

Measure and Report… Signal Quality Signal Strength

RS Detection

Measure and Report… Signal Quality Signal Strength

Fg. 30 – syc seqece ad syc Actvty © Ima Telems & Meia

63

OFDM/OFDMA and LTE Concepts

pss ad ss  te Frame strctre  The stte  the PSS a SSS is shw i the ge ppsite. I bth the Tdd a Fdd ame stte the PSS a SSS ae tasmitte peiially, twie i evey 10mS ame. Hweve the atal stte  the PSS a SSS as applie t the ame is slightly ieet epeig  whethe the ame is Tdd  Fdd a whethe the lg  sht cP is se.  The Fdd ame lates the PSS a SSS i the last 2 symbls  the 1st a 11th slts   the ai ame. Allwig the uE t btai slt bay timig iepeetly  cP legth. I the Tdd ame the PSS is late i the thi symbl  the 3 a 13th slts  the ai ame, the SSS is tasmitte 3 symbls ealie.

64

© Ima Telems & Meia

pss ad sss Frame ad slot strctre  Tme Doma  te FDD Cae 10 ms radio frame 2

3

4

5

7

8

1 ms subframe

9

SSS

10

PSS

0.5 ms 1 slot 1

2

3

1

4

2

5

3

6

4

5

7

Normal CP

6

Extended CP

pss ad sss Frame ad slot strctre  Tme Doma  te TDD Cae 10 ms radio frame 1

2

3

4

5

6

7

8

1 ms subframe

9

SSS

10

PSS

0.5 ms 1 slot 1

1

2

2

3

4

3

5

4

6

5

7

6

1

1

2

2

3

4

3

5

4

6

5

7

Normal CP

6

Extended CP

Fg. 31 © Ima Telems & Meia

65

OFDM/OFDMA and LTE Concepts

66

© Ima Telems & Meia

pss ad sss Frame strctre  Freqecy ad Tme Doma or a FDD Cell 10 ms radio frame

   B    R    6

1

2

3

4

5

6

7

1

2

3

4

5

6

7

SSS PSS RS Unused RE

1 ms subframe

Fg. 31 © Ima Telems & Meia

67

OFDM/OFDMA and LTE Concepts

Reerece sgal  Ay imati tasmitte i t a ai hael will expeiee atteati a istti   the imati as well as the aitive amlati  ise a ISI ase by the mltipath ai evimet. Theee ay imati tasmitte m A – B will eqie sme eig  eqalisati t be applie t it. The eteti pesses a eithe be heet  -heet. cheet pesses se expliit kwlege  the hael mease m kw imati passe thgh the hael. This avatage  this eteti pess is the simpliity  implemetati at the expese  vehea ata, whih ees the spetal eiey  the hael. n-heet eteti elies  sme pi kwlege  a paameti mel  the hael, explitig the elati ppeties  the hael  sig bli estimati. Whilst these tehiqes may be me spetal eiet they ae geeally mplex t implemet. LTE ses a heet eteti meth by passig, s alle, reeee Sigals (rS) thgh the hael at spei time a eqey itevals.

68

© Ima Telems & Meia

Noise

Channel, H

 A

B

 Attenuation, distortion, ISI, fading

Fg. 32 – ug Reerece sgal  te Cael © Ima Telems & Meia

69

OFDM/OFDMA and LTE Concepts

LTE Reerece sgal  Thee ae a mbe  ieet eeee sigals se i LTE. •

•

•

70

cell spei rS  mm rS, these ae available t al the uEs i a ell t pem basi hael estimati tis. uE spei rS, embee i the ata stte  uL a dL  spei uE. The uL a dL sttes ae ieet. I the uL thee ae 2 ieet types  uL rS, demlati rS (dM rS) whih ae se t take hael estimates  heet emlati a Sig rS (SrS) whih ae t ietly assiate with uL ata  tl. The SrS is se pimaily  hael qality etemiati t eable eqey-seletive shelig  the plik.  Thee ae als rS that ae spei sigals tasmitte whih ae ly se  the Mltimeia Baast Sigle Feqey netwk.

© Ima Telems & Meia

R0

      y       c       n       e       u       q       e       r        F

R0

R0

R0

R0

R0

R0

R0

 Time

Fg. 33 – Geeral Arragemet o Rs  te LTE RB © Ima Telems & Meia

71

OFDM/OFDMA and LTE Concepts

DL Cell secfc Rs  The ge ppsite shws hw the eeee sigals ae aage i the eqey a time mai.  The atal sepaati  the rS i the time mai is etemie m the maximm dpple spea expete i the hael. LTE is esige t wk p t 500Kph, assmig 2GHz spetm the maximm dpple shit wl be ~950Hz, aig t the nyqist samplig theem the sigal shl be sample with a iteval  less tha twie the ivese  the eqey shit. Theee thee shl be at least 2 rS pe slt (whee a slt i 0.5mS) i the time mai.  The sepaati  the rS i the eqey mai is elate t the amt  elay spea peset i the hael. The rMS elay spea is assme t be  wse that 991S theee the heee bawith  90% a 50%  the rMS spea expete is smewhee betwee 20KHz a 200KHz. The rS ae istibte evey 3 sb-aie (ve 2 symbls), theee the expete eqey vaiatis may be eslve.  The LTE dL has bee esige t wk with mltiple ateas, theee thee ae ieet rS pattes  eah atea pts that may be i se. The psiti  the rS i the time a eqey mais is aelly hse t ese thee is  velap betwee the atea pts.  This allws the eeive t take p t 4 sepaate dL hael estimates.  The rS its sel is a pse am seqee m a legth – 31 Gl seqee with ieet iitialisati vales epeig  the type  rS. The rS a als ay e  501 ieet ell ietities a eah rS has a ell spei eqey shit applie t it, t ee the time-eqey llisis that may  i a eqey e-se system.

72

© Ima Telems & Meia

R0

      y       c       n       e       u       q       e       r        F

R0

R0

R0

R1

R0

R1

R0

R0

Antenna port (0)

R1

R1

R1

R0

R1

(a)

R1

R1

Antenna port (1)

 Time •

Pattern o RS Depends on the Antenna Port used

•

Time and Freq separation determined rom Doppler and Delay Spread

•

RS is ormed rom a length-31 Gold sequence

Fg. 34 – DL Rs Freq-Tme Locato or 2 port Tx Atea © Ima Telems & Meia

73

OFDM/OFDMA and LTE Concepts

DL uE secfc Rs rS whih ae spei t uE may als be se, they ae embee i the rese Blks (rB) whih ae tasmitte t a spei uE. Me aately they  i the rB t whih the PdScH is mappe  uE whih ae ge t peate i this me. The me is ge by highe laye rrc sigallig. uE spei rS may be se t eable the appliati  beam-mig ateas, whee a sigle beam is me t tasmit ata t the uE. Whee beam-mig ateas ae se the hael espse  ieet uEs will be ieet thee  the se  Eu spei rS is vey sel.  The psiti  the uE spei rS i the rB is shw i the iagam ppsite, the lati   the rS i the eqey a time mai is hse s as t t llie with the ell spei rS.

74

© Ima Telems & Meia

R5

R5

      y       c       n       e       u       q       e       r        F

R5

R5

R5

R5

R5

R5

R5

R5

R5

R5

 Time

•

Specifc to a UE

•

Used to assist DL Beam-orming

•

UE RS position orthogonal to cell specifc RS

Fg. 35 – uE secfc DL Rs poto © Ima Telems & Meia

75

OFDM/OFDMA and LTE Concepts

uL uE secfc Rs  As with the wlik (dL), the plik (uL) speies the se  eeee sigals t eable the heet eteti  the hael. The rS a be se t sppt hael estimati, hael qality estimati  uL shelig, pwe tl, timig estimati a ieti--aival estimati  wlik beam-mig.  Thee ae tw types  rS: •

•

demlati rS (dM rS) assiate with tasmissi  ata  the PuScH a tl ata  the PuccH. Pimaily se t eive the hael estimate  heet emlati Sig rS (SrS) se t etemie the uL hael qality a eive the eqey seletive shelig  the uL

Demodlato Reerece sgal (DM Rs)  The uL rS ae e agai base  the Za-ch seqees, simila t thse se i the PSS a SSS. Thee ae 30 base-seqees available whse legth is etemie by the mbe  rBs allate t a uE. Withi a base-seqee thee ae 12 pssible thgal (g ss elati) time shite vesis  the seqee. A ell will be allate   the 30 base seqees a the BS will allate e  the 12 pssible time shits t the uEs. I a -MIMo ase the same time-shite seqee l be se  all uEs sie thee tasmissis ae sepaate i the eqey a time mais. Whee MIMo is se i the hael the the meas ae eqie t sepaate the uE tasmissis. I this ase the uEs shaig the MIMo hael will be allate ieet time shite seqees m the same base-seqee i the ell.  The dM rS appea  the uL hael i the 4th symbl  eah allate slt a spa the etie allate bawith. This is te  allatis  PuScH a PuccH.

76

© Ima Telems & Meia

DM Rs seqece Geerato ad Allocato Cell allocation

UE allocation

ZC Seq

ZC Seq U0

Group U29

ZC Seq U1

ZC Seq

ZC Seq U2

Group U29 ZC Seq U12

ZC Seq Group U29

ZC Seq Group U29

Mag DM Rs to te pycal Cael

  y   c   n   e   u   q   e   r    F

     H      C      S      U      P

     S      H      R      C      S      M      U      D      P

     H      C      S      U      P

     S      H      R      C      S      M      U      D      P

   k   c   o    l    b   e   c   r   u   o   s   e    R

0 1 2 3 4 5 6 Symbol

 Time Fg. 36 © Ima Telems & Meia

77

OFDM/OFDMA and LTE Concepts

sodg Reerece sgal (sRs)  The SrS have thig t  with the spei tasmissi  ata they allw the hael qality t be estimate a eables eqey seletive shelig. I aiti the mease imati may be se t ehae pwe tl,  t sppt vais stat p tis  uE with ew uL allatis. E.g. iitial McS, iitial pwe tl, timig avae a eqey seletive allatis  the st sb-ame slt.  The SrS pies the last symbl  the sb-ame, a may py a bawith geate tha that se by the ata tasmissi, epeig  spei tl ata set t the uE. The tasmissi  the SrS may be apeii whee a spei eqest is mae  SrS  peii, whee the pei may be ay vale 2,5,10,20,40,80,160  320mS.  The stte  the SrS sigal is sh that it a allw allatis  SrS sig that velap i the eqey mai. This is eessa y t allw eqey seletive shelig betwee uEs.

78

© Ima Telems & Meia

  y   c   n   e   u   q   e   r    F

     H      C      S      U      P

     H      C      S      U      P

     S      R      M      D

     S      R      S

   k   c   o    l    b   e   c   r   u   o   s   e    R

0

1

2

3 Symbol

4

5

6

2nd slot of a sub-frame  Time

Fg. 37 – Allocato o pusCh sowg sRs Locato © Ima Telems & Meia

79

OFDM/OFDMA and LTE Concepts

Modlato, Cael Codg ad Lk Adatato  The LTE ai iteae sppts seveal mlati a ig shemes a allws the shemes t be aapte aig t the qality  the ai lik. The LTE ai lik is evelpe pimaily  the tasmissi  paket ata theee the lik ate is allwe t ise a all as the qality   the lik ises a alls. F stat bit ate sevies sh as vie, meths sh as pwe tl a be se t aapt the pwe tpt t keep lik qality a theee the lik ate stat. LTE sppts QPSK, 16QAM a 64QAM with vais e ates epeig  the qality  the hael.

80

© Ima Telems & Meia

Modlato sceme sorted by LTE

QPSK 2 bits/Baud

16QAM 4 bits/Baud

64QAM 6 bits/Baud

Tycal snR perormace o LTE Modlato ad Codg Typical SNR Performance of LTE Modulation and Coding BLER

10-1

10-2

0

5

10

15

20

25

SNR

QPSK, r = �∕ 

QPSK, r = ½

QPSK, r = ∕ 

QPSK, r = 4 ∕ 5

16QAM, r = �∕ 

16QAM, r = ½

16QAM, r = ∕ 

16QAM, r = 4 ∕ 5

64QAM, r = �∕ 

64QAM, r = ½

64QAM, r = ∕ 

64QAM, r = 4 ∕ 5

Fg. 38 © Ima Telems & Meia

81

OFDM/OFDMA and LTE Concepts

82

© Ima Telems & Meia

Modlato ad Codg Rate wt sectral Efcecy CQi dex

Modlato

Aroxmate code rate

Efcecy (ormato bt er ymbol)

0

n tasmissi

–

–

1

QPSK

0.076

0.1523

2

QPSK

0.12

0.2344

3

QPSK

0.19

0.3770

4

QPSK

0.3

0.6016

5

QPSK

0.44

0.8770

6

QPSK

0.59

1.1758

7

16QAM

0.37

1.4766

8

16QAM

0.48

1.9141

9

16QAM

0.6

2.4063

10

64QAM

0.45

2.7305

11

64QAM

0.55

3.3223

12

64QAM

0.65

3.9023

13

64QAM

0.75

4.5234

14

64QAM

0.85

5.1152

15

64QAM

0.93

5.5547

Fg. 38 © Ima Telems & Meia

83

OFDM/OFDMA and LTE Concepts

Cael Codg Cyclc Reddacy Ceck (CRC)  A crc ig pess is applie t eah Taspt Blk ( TB) – 24-bit crc applie t dLScH, PcH, a McH taspt blks a 16-bit crc applie t BcH a dcI e blks. segmetato ce blk segmetati is applie t dL-ScH, PcH, a McH taspt blks (i.e., ata that ae tb ee), with a aitial 24-bit crc mpte  eah e-blk (i ases whee segmetati pes me tha e e-blk). Ecodg  A Tb e is applie t dL-ScH, PcH, a McH ata t be aie ve a wlik physial hael is samble pi t mlati. cvltial e is applie t BcH a dcI ata (sigle e blk). chael ig se ve the LTE ai iteae is base  the uTrAn release 6 tb-ig shemes. othe shemes ae e sieati with the mai ives beig • • • • •

Impvemet i pwe eiey (lw Eb/n) Lwe mplexity ee i the uE ce ates lwe tha 1/3. Extesi  maximm e blk size remval  tail

 All the abve bjetives ae i psit  a eti i vehea, a impvemet i rF pemae, a eti i eqipmet sts. cig shemes beig stie by 3GPP ile: • • • • • •

d-biay tb es Ite-blk pemtati tb e (IBPTc) rate-mpatible/qasi yli LdPc e (rc/QcLdPc) cateate zigzag LdPc e  Tb sigle paity hek (SPc) lw-esity paity hek (LdPc) e Shtee tb e by iseti  tempay bits

Rate Matcg rate mathig is applie  a e-blk basis t dL-ScH, PcH, McH, BcH, a dcI ata.  This ti pems apppiate ptig aig t the AMc paametes. Fige 39 is a shemati iagam  the abve pesses.

84

© Ima Telems & Meia

UE… UE1  TB2

TB CRC  TB1

#CB

PDSCH Transport block (TB) processing Codeblock (CB) Segmentation

#CB

#CB

CB CRC

Turbo encoder (internal interleaver)

#CB Subblock interleaver Subblock interleaver Subblock interleaver

Layer Mapping

• Rate

matching • HARQ

Scrambling

# layers

Modulation

functionality Precoding

No. of antennas

RF Front-End

CP Insertion

IFFT

Resource Element Mapper (Subframe builder)

PBCH, Ref. Signals, P-SCH, S-SCH, PCFICH, PDCCH, PHICH, PMCH

Fg. 39 – Cael Codg proce  LTE © Ima Telems & Meia

85

OFDM/OFDMA and LTE Concepts

hARQ (hybrd Atomatc Reqet) HArQ is mmly se i emegig mmiati systems t pvie a high eliability ve wieless haels. HArQ is essetially a mbiati  Atmati reqest (Arc) a Fwa E ceti (FEc) tehiqes. Amg tw ieet types  HArQ ae chase mbiig a iemetal eay (Ir), whih ae als kw as HArQ Type-I a HArQ Type-II ( Type-III), espetively. I the chase mbiig sheme the eeive ses a etasmissi t the tasmitte i the iitial paket ails t be sesslly ee. The the tasmitte eses the same paket agai s that the eeive mbies the pevisly eeive paket with the ew paket. I the Ir sheme istea  eseig the same paket, the tasmittes i geeal a me eay tha the pevis paket a eeate a ieet paket eliveig the same imati. The eeive ees t keep the pevis ees paket (paket with ba crc) i the memy a mbie it with the ewly eeive paket  ahievig a highe ig gai.

86

© Ima Telems & Meia

normal ARQ Oerato CRC

Data #2

CRC

Data #1

CRC

Data #1

x

Discard data

x

Buffer data

 ARQ data #1

CRC

Data #1

hybrd-ARQ Oerato CRC

Data #2

CRC

Data #1

CRC

Data #1

 ARQ data #1

CRC

Data #1

CRC

CRC

•

UL-SCH, DL-SCH support HARQ

•

1 Bit HARQ Field

Data #1 buffered

Data #1 combined

Dowlk •  Asynchronous •

 ACK/NACK on PUCCH and PUSCH

ulk • Synchronous •

 ACK/NACK on PHICH Fg. 40 – LTE hARQ

© Ima Telems & Meia

87

OFDM/OFDMA and LTE Concepts

Reortg o uE Feedback  The uE a be ge t ept the qality  the hael t assist the enB with seletig the mst apppiate mlati a ig sheme. The epts ae eive m the wlik sigal qality base  the wlik eeee sigals. The ept sigal qality is t a iet iiati  the SInr i the hael, istea the chael Qality Iiat (cQI) ees t the highest level  mlati a ig it a ee with a e ate t exeeig 10%. This meth  eptig allws ay avae sigal pessig a hael eig tehiqes t be emplye.  The eptig may sist  the llwig elemets: cQI(hael qality iiat) is a iiati  the wlik mbile ai hael qality as expeiee by this uE. Essetially, the uE is ppsig t the enB a ptimm mlati sheme a ig ate t se  a give ai lik qality, s that the esltig taspt blk e ate wl t exee 10%. 16 mbiatis  mlati sheme a ig ate ae speie as pssible cQI vales. The uE may ept ieet types  cQI.  A s-alle “wieba cQI” ees t the mplete system bawith. Alteatively, the uE may evalate a “sb-ba cQI” vale pe sb-ba  a etai mbe  ese blks whih is ge by highe layes. The ll set  sb-bas wl ve the etie system bawith. I ase  spatial mltiplexig, a cQI pe e w ees t be epte. PMI(peig matix iiat) is a iiati  the ptimm peig matix t be se i the base stati  a give ai iti. The PMI vale ees t the ebk table.  The etwk ges the mbe  ese blks that ae epesete by a PMI ept.  Ths t ve the ll bawith, mltiple PMI epts may be eee. PMI epts ae eee  lse lp spatial mltiplexig, mlti-se MIMo a lse-lp ak 1 peig MIMo mes. rI(ak iiati) is the mbe  sel tasmissi layes whe spatial mltiplexig is se. F tasmit ivesity the ak is eqal t 1.  The eptig may be peii  apeii a is ge by the ai etwk. Apeii eptig is tiggee by a cQI eqest taie i the plik shelig gat. The uE wl se the ept  PuScH. I the ase  peii eptig, PuccH is se i  PuScH is available.

88

© Ima Telems & Meia

CQi – Cael Qalty idcator •

DL channel quality as experienced by UE

•

UE proposes optimum modulation and coding scheme

•

Wideband CQI – complete system bandwidth

•

Sub-band CQI – number or resource blocks

pMi – precodg Matrx idcator •

Indicates optimum precoding matrix

•

Reers to codebook table

•

Closed loop, MU-MIMO, Closed loop rank 1

Ri – Rak idcato •

Number o useul transmission layers or spatial multiplexing

•

TX diversity Rank is 1

•

Periodic or aperiodic

•

CQI request on DL – UE reports on PUSCH

•

UE reports on PUCCH i no PUSCH available

Fg. 41 – Cael Reortg © Ima Telems & Meia

89

OFDM/OFDMA and LTE Concepts

power Cotrol  LTE Like may mbile ai systems LTE sppts yami  aaptive pwe tl. The eas  pwe tl systems is t ee the pwe emissis m evies a theee ee the veall iteeee ass the etwk.  The system  LTE pwe tl is shw  the ppsite page. The sheme basially ivlves paametes that ae etemie by the et pie bawith, etwk etemie mpets  the ell a uE, the ai lik pathlss a a pwe tl mma m the etwk.  The uE will ea this imati m the system imati blks  i eiate messages ig eti setp. May  the paametes ae etemie by the ppe layes a sigalle ig ese allati. Sme paametes sh as the pwe tl mma ae yami a a by mie  a egla basis.

90

© Ima Telems & Meia

PMAX is the maximum allowed power that depends on the UE power class MPUSCH(i) is the bandwidth of the PUSCH resource assignment expressed in number of resource blocks valid for subframe i

PO_PUSCH(j) = PO_NOMINAL_PUSCH(j) + PO_UE_PUSCH(j) where

PO_NOMINAL_PUSCH (j) is a 8-bit cell specific signalled from higher layers PO_UE_PUSCH(j) is a 4-bit UE specific component PPUSCH(i) = min {PMAX, 10log10 (MPUSCH(i) ) + PO_PUSCH(j) + α(j).PL + ∆ TF(i) +ƒ(i)}

α(j)

= 0, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1 depending on certain configurations

PL is the downlink pathloss estimate calculated in the UE

∆ TF

is related to the Transport Block Size (TBS) and the number of resource elements

ƒ(i) = ƒ(i–1) + δPUSCH(i–KPUSCH ) where δPUSCH is a UE specific correction value, also referred to as a TPC command

Fg. 42 – power Cotrol  LTE © Ima Telems & Meia

91

OFDM/OFDMA and LTE Concepts

Te uer plae ad Cotrol plae protocol Te uer plae Fige 43 shw the use Plae ptls, Paket data cvegee Ptl (PdcP), rai Lik ctl (rLc) a Meim Aess ctl (MAc). These ptls will igiate a temiate i the enB a uE PDCP Layer   The PdcP will eeive se ata m the nAS a wa it t the rLc laye, a vie vesa. It als pvies etasmissi, seqeig, a pliate paket eteti  have whe rLc peates i akwlege me. cipheig, heae e/mpessi a time base paket isa ae sme  the the tis that this laye pvies.

RLC Layer   The piipal ti  rLc is t pvie a laye 2 atalik-like ti. The rLc laye will eeive ata se ata m the PdcP a wa it  shele tasmissi t the MAc laye a vie vesa.  This laye a pvie ArQ base e eteti/eti, segmetati a eassembly  pakets, seqee elivey  ppe laye imati (t ig have) a pliate eteti. rLc sppts 3 mes  ata tase akwlege me, -akwlege me, a taspaet me (AM, uM, TM). Eah tase me will be selete epeig  the eqie QS  the ppe late sevies.

MAC Layer   The MAc laye is pimaily espsible  esig se ata is mappe t the et haels  tasmissi  the physial laye, this pess is kw as lgi al t physial hael mappig. othe tis ile mltiplexig/e-mltiplexig  imati m mltiple ai beaes, HArQ e eti, piity halig a shelig, taspt mat seleti a paig.  The MAc laye a als ept ta vlme measemets t ppe layes.

92

© Ima Telems & Meia