Iterative Frequency-Domain. Modulations. Rui Dinis

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1 Iterative Frequecy-Domai Detectio for Sigle-Carrier Modulatios Rui Diis 1

2 Summary 1 Cotext ad motivatio 2 OFDM ad SC-FDE modulatios 3 IB-DFEtechiques 4 Applicatios MIMO systems Network diversity schemes BS cooperatio 5 Coclusios 2

3 Equalizatio Techiques Frequecy selective chaels (time-dispersive) Iter-Symbol Iterferece (ISI) Performace degradatio MLSE receiver Optimum receiver Efficiet implemetatio: Viterbi equalizer Expoetial complexity Covetioal equalizers Time-domai implemetatio Complexity liear with L C Suitable for moderately dispersive chaels 3

4 Block Trasmissio Techiques Block trasmissio techiques Frequecy-domai receiver implemetatio Low complexity FFT-based receivers Suitable for severely time-dispersive chaels OFDM techiques Multicarrier modulatio CP-assisted block trasmissio Higher carrier sychroizatio requiremets High evelope fluctuatios 3 => Amplificatio difficulties 2 s(t) t/t 4

5 SC-FDE Modulatios CP-assisted block trasmissio Lower evelope fluctuatios FDE structure y Y k S k DFT X IDFT s FDE coefficiets F k F k 1/ Hk, ZF * Hk, MMSE 2 1/ SNR Hk 5

6 SC-FDE vs OFDM S k s y Y k k S S ˆk s y Y k S k s sˆ Similar overall complexity SC-FDE with simpler trasmitter => uplik OFDM with simpler receiver => dowlik => Hybrid OFDM/SC-FDE systems (eg, LTE) 6

7 SC-FDE Performace MFB (Matched Filter Boud): E 1 P E Q H b N 1 2 bmfb, 2 H k k0 k N0 N 10 0 : OFDM 10-1 : SC-FDE (ZF) o : SC-FDE (MMSE) : MFB BER E b /N 0 (db) 7

8 Performace Costraits for SC-FDE Liear FDE => Noise ehacemet, residual ISI Better performace with oliear equalizers Covetioal DFE Good performace/complexity tradeoffs Error propagatio p y ŝs s Ca we make a DFE for SC-FDE? 8

9 IB-DFE Desig Y k y s S k s ˆ F k ˆk S s ˆ Iterative FDE B k Optimum receiver coefficiets i * Hk Fk 2 2 1/ SNR 1 Hk Bk FkHk 1 1 with selected to esure 1 N N FH 1 k0 k k * 2 ad E s ˆ s / E s 12 Pb (for QPSK) 9

10 IB-DFE Performace 10 0 BER : IB-DFE : MFB (+): Iter 1 (*): Iter 2 (): Iter 3 ()It (o): Iter E b /N 0 (db) BER for iteratios 1 (liear FDE), 2, 3 ad 4 10

11 IB-DFE for Geeral Costellatios ti Y k F k S k X IDFT + - Required operatios B k x S k DFT s s LLR comput ( m) Average s comput Computatio of bits LLRs Computatio of average bit values Computatio of average symbol values Computatios of block reliabilities Dec 11

12 Geeralized Mappig Rule pp g Costellatio symbols expressed as fuctio of the Costellatio symbols expressed as fuctio of the correspodig bits as: 1 ) ( 1 (3) (2) (1) (2) 1) (, b g b g b b g b g b g g s m M m i is the biary represetatio of,,,,, 0, 1, 2, 1, i b g b g b b g b g b g g s i i i i m i i The log-likehood ratio of the mth bit of the th trasmitted symbol is by: s ed sy bo s by:, exp exp log 0 ~ Pr 1 ~ Pr log 2 ) ( ~ 2 ~ ) ( ) ( ) ( m s s S s s m m m s s 12 exp 0 Pr ) ( m S s 0 or1, respectively where subsets of are ad ) ( 1 ) ( 0 m m

13 Computatio of IB-DFE P t Parameters 1 1 ) ( ) ( ) ( Averagebit values coditioed to the FDE output M m i 0 0 ) ( ) (, 2 tah i m m i m m i b g s b the estimates Block reliability of 1 1 ) ( 2 M m i m 2 tah where, ˆ ) ( ) ( ) ( 2 *, m m M i m m i g g s E s E s m i 13 i0 g i

14 Turbo FDE s s s s 14

15 BER Performace BER : Turbo FDE : IB-DFE (soft) : MFB (+): Iter 1 (*): Iter 2 (o): Iter E b /N 0 (db) Coded BER performace for IB-DFE ad Turbo FDE 15

16 MIMO Systems P trasmitters ad RP multiple receivers rth Received sigal P ( r) eq( r) ( r) T Y S, H, N Y H S N k k p k p k k k k k p1 T T Detectio of a give sigal S, F, Y B, S Optimum receiver coefficiets 1 2 H 2 N H k, p k p k 2 R k S F H I P H I H B H F e k, p k k, p p P k p k p k k p k diag( 1, 2,, P ) 16

17 Network Diversity Techiques Noise ad/or collisios => Corrupted packets Covetioal schemes Discard corrupted packets + retrasmissios => Poor performace Packet Combiig g( (PC) ad Multi-Packet Detectio (MPD) Take advatage of iformatio i corrupted packets Improved performace with retrasmissios 17

18 Packet Combiig (Diversity Combiig) i Type-II H-ARQ scheme Code-combiig based o repetitio codes => Reduced complexity

19 SC-FDE with Diversity Combiig Receiver structure 19

20 IB-DFE Optimizatio Feedforward coefficiets: ( r)* ( r) Hk F 1/ SNR 1 H r1 k selected to have k 2 R ( r) 1 N 1 L ( r) ( r) N F k 0 r 1 k H k 1 2 Feedback coefficiets: R ( r ) ( r ) k r 1 k k B F H 1 20

21 Copig with Fixed Chaels Ideal coditios: ucorrelated chaels (UC) Copig with fixed chaels: shifted packet (SP) 3 25 N 2 H k k/n 21

22 PER Performace Liear FDE with PC (1, 2, 3, 4 retrasmissios) 22

23 PER Performace IB-DFE with PC (4 iteratios; 1, 2, 3, 4 retrasmissios) 23

24 Gooput Performace R max =5 retrasmissios ad saturated load 24

25 NDMA (Network Diversity Multiple Access) Collisios 25

26 IB-DFE-Based Receiver for NDMA 26

27 PER Performace Turbo IB-DFE (4 iteratios) 27

28 Q Simultaeous Users 28

29 Copig with Q>Q Q max Usolvable collisios whe Q>Q max Backoff techiques to reduce the umber of trasmitters Costat backoff (CB) p k = p Expoetial backoff (EB) p k = p k+1 Optimum p * Saturated throughput with J=8 users ad Q max =4 29

30 Throughput for Q max =1, 2 4 ad J E b /N 0 =11dB E b /N 0 =1dB 30

31 Base Statio Cooperatio Poit-to-poit to liks Capacity: Shao limit Performace close to capacity Cellular system (multipoit-to-multipoit) Differet frequecies for differet cells Poor spectral efficiecy Network-level techiques to icrease spectral efficiecy BS (Base Statio) cooperatio 31

32 BS Cooperatio Same frequecy for MTs i adjacet cells Iheret macro-diversity ature Muliuser sceario IB-DFE-based receiver as i MIMO systems 32

33 BER Performace Macro-Diversity Iterferece sceario without BS cooperatio (P=2, R=1) 33

34 BER Performace with P=R=2 2 Equal-power users Low ad high power users 34

35 Iterferece Aligemet At 1 At 1 BS 1 W 1,l At M H 1,1,l H 2,1,l At M UT 1 G 1,l At 1 H K,1, l At 1 BS 2 W 2,l At M At M UT 2 G 2,l At 1 H1, K, l H 2 2, Kl, At 1 BS K At M H K, Kl, At M W K, l UT K G K, l K-user MIMO iterferece chael 35

36 MC-CDMA with Iterferece Aligemet Trasmitter structure for a geeric user with IA s/p s/p Spreadig (L) Spreadig (L) IA Preco dig IA Preco dig IFFT + CP IFFT + CP Atea 1 Atea M CSI from Other Tx Receiver structure Atea 1 FFT - CP Equalizer + Noise Whiteig IB-DFE Atea M FFT - CP CSI Eq Chaels 36

37 Receiver Structure IB-DFE (PIC approach) applied to the received sigal after oise whiteig process x + - S/P Despreadig (L) Despreadig (L) Demod Demod x P/S Spreadig (L) Spreadig (L) Mod Mod 37

38 BER Performace for K=3, M= B E R x44 IA ZF 4x4 IA MMSE 4x4 IA ZF+IB-DFE 1 iter 4x4 IA ZF+IB-DFE 2 iter 4x4 IA ZF+IB-DFE 3 iter 4x4 IA ZF+IB-DFE 4 iter MF L=128 B E R x4 IA ZF 4x4 IA MMSE 4x4 IA MMSE+IB-DFE 1 iter 4x4 IA MMSE+IB-DFE 2 iter 4x4 IA MMSE+IB-DFE 3 iter 4x4 IA MMSE+IB-DFE 4 iter MF L= Eb/No (db) Eb/No (db) ZF IA MMSE IA 38

39 Coclusios IB-DFE receivers for SC-FDE Iterative receivers implemeted i the frequecy domai Extesio for etwork diversity (DC ad/or NDMA), BS cooperatio, etc BER performace close to the MFB Suitable for broadbad wireless systems 39

40 Refereces Geeral IB-DFE issues AGusmão, PTorres, RDiis ad NEsteves, A Turbo FDE Techique for Reduced-CP SC-Based Block Trasmissio Systems, IEEE Tras o Comm, Vol 55, No 1, pp 16-20, Ja 2007 AGusmão, PTorres, RDiis ad NEsteves, A Reduced-CP Approach to SC/FDE Block Trasmissio for Broadbad Wireless Commuicatios, IEEE Tras o Comm, Vol 55, No 4, pp , April 2007 RDiis, PSilva ad AGusmão, IB-DFE Receivers with Space Diversity for CP-Assisted DS-CDMA ad MC-CDMA Systems, Europea Tras o Telecomm, Vol 18, No 7, pp , Nov 2007 NBeveuto, RDiis, DFalcoer ad STomasi, "Sigle Carrier Modulatio with No Liear Frequecy Domai Equalizatio: A Idea Whose Time Has Come Agai", IEEE Proceedigs, Vol 98, No 1, page 69-96, Ja 2010 F Silva, R Diis ad P Motezuma, Estimatio of the Feedback Reliability for IB-DFE Receivers, ISRN Commuicatios ad Networkig Joural, 2011 F Amaral, R Diis, P Motezuma, N Souto, Approachig the MFB with Block Trasmissio Techiques, Europea Tras o Telecommuicatios, Vol 23, No 1, pp 76-86, February, 2012 J Silva, R Diis, N Souto, P Motezuma, Sigle-carrier frequecy domai equalisatio with hierarchical costellatios: a efficiet trasmissio techique for broadcast ad multicast systems, IET Commuicatios, Vol 6, No 13, pp , Sep

41 Refereces MIMOsystems RDiis, RKalbasi, DFalcoer ad ABaihashemi, "Iterative Layered Space-Time Receivers for Sigle-Carrier Trasmissio over Severe Time-Dispersive Chaels", IEEE Comm Letters, Set 2004 PSilva ad RDiis, Multiuser Detectio for the Uplik of Prefix-Assisted DS-CDMA Systems Employig Multiple trasmit ad Receive Ateas, IEEE VTC 06(Fall), Motreal, Caada, Sep 2006 PSilva ad RDiis, Frequecy-Domai Multiuser Detectio for CP-Assisted DS-CDMA Sigals, IEEE VTC 06 (Sprig), Melboure, Australia, May 2006 RKalbasi, DFalcoer, ABaihashemi ad RDiis, "A Compariso of Frequecy Domai Block MIMO Trasmissio Systems", IEEE Tras o Vehicular Techology, Vol 58, No 1, pp , Ja

42 Refereces Network Diversity RDiis, PCarvalho, LBerardo, ROliveira, MPereira ad PPito, Frequecy-Domai Multipacket Detectio: A High Throughput Techique for SC-FDE Systems, IEEE Tras o Wireless Commuicatios, Vol 8, No 7, pp , Jul 2009 F Gahão, M Pereira, L Berardo, R Diis, R Oliveira, P Pito, Performace of Hybrid ARQ for NDMA Access Schemes with Uiform Average Power Cotrol, Joural of Commuicatios, Vol 6, No 9, pp , Academy Publishers, Dec 2011 M Pereira, L Berardo, R Diis, R Oliveira, P Motezuma, P Pito, Performace of diversity combiig ARQ error cotrol i a TDMA SC-FDE system, IEEE Tras o Commuicatios, Vol 60, No 3, pp , Mar 2012 F Gahão, R Diis, L Berardo ad R Oliveira, Aalytical BER ad PER Performace of Frequecy-Domai Diversity Combiig, Multipacket Detectio ad Hybrid Schemes, IEEE Trasactios o Commuicatios, Vol 60, No 8, pp , Aug 2012 M Silva, R Diis, P Motezuma, Iterative Frequecy-Domai Packet Combiig Techiques for UWB Systems with Strog Iterferece Levels, Wireless Persoal Commuicatios, Vol 9, No 9, July, 2012 M Pereira, L Berardo, R Diis, R Oliveira, P Pito, Frequecy-Domai Cross-Layer Diversity Techiques: A Efficiet Way of Copig with Lost Packets i Broadbad Wireless Systems, IEEE Wireless Commuicatios Magazie, 2013 M Pereira, L Berardo, R Diis, R Oliveira, P Pito, O the Use of Frequecy-Domai Cross-Layer Diversity Techiques to Cope with Lost Packets, Physical Commuicatio, Elsevier Physical Commuicatio F Gahão, M Pereira, L Berardo, R Diis, R Oliveira, P Pito, Performace Aalysis of a Hybrid ARQ Adaptatio of NDMA Schemes, IEEE Trasactios o Commuicatios,

43 Refereces Joit detectio/estimatio CLam, DFalcoer, FDailo-Lemoie ad RDiis, Chael Estimatio for SC-FDE Systems Usig Frequecy Domai Multiplexed Pilots, IEEE VTC 06(Fall), Motreal, Caada, Sep 2006 RDiis, CLam ad DFalcoer, "Joit Frequecy-Domai Equalizatio ad Chael Estimatio usig Superimposed Pilots", IEEE WCNC'08 RDiis, TAraújo, PPedrosa ad FNues, "Joit Turbo Equalizatio ad Carrier Sychroizatio for SC- FDE Schemes", Europea Tras o Telecomm, Vol 21, No 2, pp , Mar 2010 P Pedrosa, R Diis ad F Nues, Iterative Frequecy Domai Equalizatio ad Carrier Sychroizatio for Multi-resolutio Costellatios, IEEE Tras o Broadcastig, Vol56, No4, pp , Dec 2010 P Pedrosa, R Diis i ad F Nues, Aalytical l Performace Evaluatio of a Class of Receivers with Joit Equalizatio ad Residual CFO Estimatio, accepted for publicatio at Trasactios o Emergig Telecommuicatios Techologies P Pedrosa, R Diis, F Nues, J Bioucas-Dias, Phase Drift Estimatio ad Symbol Detectio i Digital Commuicatios: A Stochastic Recursive Filterig Approach, IEEE Commuicatios Letters, Vol 16, No 6, pp , Jue 2012 F Silva, R Diis, P Motezuma, Chael Estimatio ad Equalizatio for Asychroous Sigle Frequecy Networks, IEEE Trasactios o Broadcastig,

44 Refereces Offset modulatios J Luzio, R Diis, P Motezuma, SC-FDE for Offset Modulatios: A Efficiet Trasmissio Techique for Broadbad Wireless Systems, IEEE Tras o Commuicatios, Vol 60, No 7, pp , July 2012 M Luzio, R Diis, P Motezuma, Pragmatic Frequecy Domai Equalizatio for Sigle Carrier with Offset Modulatios, IEEE Trasactios o Wireless Commuicatios, 2013 NL chaels PSilva ad RDiis, "A Turbo SDMA Receiver for Strogly gynoliearly Distorted MC-CDMA Sigals", Caadia Joural of Electrical ad Computer Egieerig, 2008 PSilva ad RDiis, Joit Turbo Equalizatio ad Multiuser Detectio of MC-CDMA Sigals With Strogly Noliear Trasmitters, IEEE Tras o Vehicular Techology, Vol 58, No 5, pp , 2298, Ju 2009 RDiis ad PSilva, "Iterative Detectio of Multicode DS-CDMA Sigals with Strog Noliear Distortio Effects", IEEE Tra o Vehicular Techology, Vol 58, No 8, pp , Oct 2009 RDiis, i PSilva ad TAraújo, Turbo Equalizatio with Cacelatio of Noliear Distortio ti for CP-Assisted ad Zero-Padded MC-CDM Schemes, IEEE Tras o Commuicatios, Vol 57, No 8, pp , Aug

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