MIMO in (G) cllular systms August 2 Pag Qualcomm Propritary Qualcomm Propritary Pag
Outlin MIMO in cllular: myths & truths MIMO tchniqus across 3GPP rlass MIMO rcivrs: dsign & prformanc considrations Antnna managmnt tchniqus Rcnt dvlopmnts Lssons larnd Pag 2 Qualcomm Propritary Pag 2
MIMO in cllular: myths & truths (/2) Myth: high antnna corrlation prcluds fficint MIMO insufficint scattring in cllular nvironmnt high corrlation / low fficincy / blocking on usr dvic form factor Truth: smartphon antnnas allow for low corrlation across bands RX layout on a smartphon: corr.2 /.6 in high / low bands 7MHz (top), 8-9MHz (bottom),.7-6ghz (both) NYC pdstrian NYC mobility RX corrlation TX corrlation RX corrlation TX corrlation Truth: signal strngth wll abov thrmal >2dB in dns urban, >db (sub-)urban 9% Pag 3 Qualcomm Propritary Pag 3
MIMO in cllular: myths & truths (2/2) Myth: oprating CINRs too low to nabl systm lvl MIMO gains 3% UEs blow db, 6% UEs blow 5dB, 9% UEs blow 2dB MIMO gain ovr SIMO Equal grad of srvic Equal bandwidth 2 x 2 2 x x 2 x 2 2 x x ITU % 2% 8% 9% 36% 7% SCM -% 5% 5% 5% 22% 32% Truth: NWs oprat at fractional loading rsulting in high CINRs Dallas NYC pdstrian CL-SM OL-SM Pag Qualcomm Propritary Pag
LTE DL MIMO transmission mods LTE Rl TM Dscription Commnts 8 Singl antnna port aka SIMO 8 2 Transmit divrsity 8 3 Opn loop spatial multiplxing 8 Closd loop spatial multiplxing 8 5 Multi-usr MIMO 8 6 Closd loop rank prcoding 8 7 Singl stram bamforming 9 8 Dual stram bamforming 9 UE-RS basd SU-/MU-MIMO TM9 nhancmnts to support intr-cll coordination (CoMP) Applicabl to clls configurd w/ on CRS port, fairly uncommon across dploymnts SFBC for 2 CRS ports, FSTD+SFBC for CRS ports, rank fallback for opn/closd loop MIMO, usd for DL control Larg dlay CDD (LD-CDD): (still) prdominant MIMO TX mod across LTE NWs Closd loop pr-coding, dployd initially by ALU only, gtting incrasing traction, incrasing intrst w/ CRS Poorly dfind in trms of DEMOD (no rliabl mans of MU- MIMO dtction) and CSF, not usd in practic Functionally quivalnt to TM w/ codbook rstriction to rank, not sn in practical dploymnts Mainly drivn by 8TX TD-LTE dploymnts to support rciprocity basd bamforming, no ddicatd CSF Extnsion of TM7 to two spatial strams, sam purpos, somwhat bttr yt crippld CSF support Provisions for DEMOD & CSF w/ incrasd numbr of TX antnnas, up to 8 layrs, introduction of ddicatd RS for fdback (CSI-RS) Concpts of intrfrnc masurmnt sts and CSI procsss, notions of RS co-location to handl timing / frquncy and long trm channl paramtrs DEMOD: CRS CSF: CRS DEMOD: UE-RS CSF: CRS DEMOD: UE-RS CSF: CSI-RS Pag 5 Qualcomm Propritary Pag 5
LTE numrology and rfrnc signals LTE radio fram numrology Common rfrnc signals (CRS) 5 ms 2 3 5 6 7 8 9 Normal CP 2 3 5 6 2 3 5 6 R R2 R R R3 R subcarrir Extndd CP 2 3 5 2 3 5 R R2 R R R3 R subcarrir RB slot R R3 R R R2 R 2 3 R R3 R R R2 R 2 3 R R2 R R R3 R 5 6 R R2 R R R3 R 5 6 RB 7 7 8 8 subfram R R3 R R R2 R 9 R R3 R R R2 R 9 OFDM symbol slot slot subfram OFDM symbol slot slot subfram Pag 6 Qualcomm Propritary Pag 6
Pag 7 Qualcomm Propritary Pag 7 CRS basd MIMO transmission (/2) Concpt of transport block (TB) aka codword to layr mapping w/ maximum 2TBs rgardlss of th numbr of layrs OFDM Mappr OFDM signal gnration Layr Mappr Scrambling Prcoding Modulation Mappr Modulation Mappr OFDM Mappr OFDM signal gnration Scrambling cod words layrs antnna ports Numbr of layrs υ U ) (i D [ ] [ ] 2 2 2 2 2 i 3 3 8 3 3 3 2 3 3 2 i i 8 2 6 2 8 6 2 6 2 i i i 2CRS: I 2x2 CRS: cycls ovr prcodrs Opn loop spatial multiplxing (LD-SDD): altrnating prcodrs (CRS) w/ prmutation of prcodr vctors across REs symmtric stram virtual antnna mapping dsignd to oprat w/ common CQI across strams simplst & most prvalnt MIMO transmission mod to dat
CRS basd MIMO transmission (2/2) Closd loop spatial multiplxing: prcodd transmission w/ widband or sub-band PMI application 2CRS: PMIs @ rank, 2 PMIs @ rank 2 CRS: 6 PMIs @ rank, 2 Codbook indx Numbr of layrs υ 2 2 2 2 2 2 2 2 3 2 - diffrntiatd CQI valus across strams: nabld SIC rcivrs xplicit widband PMI or implicit sub-band PMI lss common but gaining traction, rnwd intrst w/ CRS Closd loop rank- prcoding: spcial cas of closd loop spatial multiplxing w/ rank rstriction functionally achivabl w/ TM, not much practical valu Multi-usr MIMO: quivalnt to closd loop rank- prcoding w/ halvd transmit powr assumption built into UE fdback lacks practical mans to dtct/handl MU intrfrnc, not usd Pag 8 Qualcomm Propritary Pag 8
UE-RS basd MIMO transmission Singl stram bamforming: channl rciprocity (TDD) to achiv transparnt bamforming, tailord to larg # antnnas UE spcific RS (UE-RS) through sam prcoding as data CSF from transmit divrsity: CSF DEMOD mismatch rlis on NW outr loop to rcovr bamforming gains China (8TX) & limitd dploymnts in Japan PDSCH RE UE-RS RE Dual stram bamforming: xtnds singl stram bamforming transparnt MU-MIMO w/ dtction & mitigation at th UE CSF inhritd from CRS mods: CSF DEMOD mismatch rquirs UL antnna switching fatur to nabl MIMO Rl-8 TxDiv fatur mandatd along w/ TM8 support rcnt dploymnts, prdominantly in China CRS RE CDM sprading Pag 9 Qualcomm Propritary Pag 9
CSF for lgacy DL MIMO UE fdback masurmnts basd on CRS constraints on NW spatial procssing & mismatch for UE-RS mods Priodic fdback snt on UL control channl (PUCCH) tradoff btwn constant ovrhad & dtail/accuracy widly usd across NWs Apriodic fdback snt as schduld UL upon NW rqust on-dmand fdback w/ DL schduling activity allowing for gratr fdback dtail/accuracy CQI fdback typ Widband CQI UE slctd sub-band CQI NW slctd sub-band CQI PMI fdback typ No Widband PMI Subband PMI Mod - Mod - Mod -2 TM,2,3,7 TM,5,6 TM,6 Mod 2- Mod 2- Mod 2-2 TM,2,3,7 TM,5,6 TM,6 Mod 3- Mod 3- TM,2,3,7 TM,5,6 N/A Priodic (PUCCH) only Apriodic (PUSCH) only Priodic (PUCCH) & apriodic (PUSCH) Sub-band schduling dployd w/ NW slctd fdback Pag Qualcomm Propritary Pag
Advancd DL MIMO dsign principls Fundamntal chang in RS dsign & us principls TX antnna dimnsion spatial multiplxing dimnsion CSI stimation accuracy dmodulation stimation accuracy nabl NW spatial procssing transparnt to th UE convrgnc towards UE-RS basd dmodulation dsign concpt of ddicatd CSI-RS in Rl- (TM9) Prcoding framwork to accommodat practical configurations hirarchical codbooks for commrcial 8TX configurations sparation into widband & sub-band spatial fdback Scaling to highr MIMO ordr & SU-MIMO support primarily xtnsion of UE-RS dsign Towards a bttr intr-cll coordination notions of intrfrnc masurmnt rsourcs (IMR) & CSI procss Pag Qualcomm Propritary Pag
DL CoMP framwork CoMP CSI nhancmnts CSI fdback rlatd to various/multipl transmission points introduc th notion of intrfrnc hypothss CoMP CSI nhancmnts virtual cll ID & quasi-colocation of rfrnc signals Homognous dploymnts Scn- Intra-NB CoMP Htrognous dploymnts Scn-3 Macro/RRHs ar configurd with diffrnt PCIs Scn-2 Intr-NB CoMP Scn- Macro/RRH ar configurd with th sam PCI common PDCCH control rgion Pag 2 Qualcomm Propritary Pag 2
Advancd DL MIMO rfrnc signals UE-RS to accommodat up to 8 MIMO strams unifid UE-RS pattrn structur scalabl w/ MIMO rank high rank ports addd through tim domain CDM trad ovrhad for lss tolranc w.r.t. mobility CSI-RS to accommodat up to 8 TX ports configurabl duty cycl: 5,,2,,8ms in 2 tons: 5us dlay sprad rsolution CSI procss: a combination of CSI-RS and IMR IMRs usd to masur intrfrnc undr diffrnt (CoMP) hypothss mix & match of TX channl & intrfrnc scnarios in UE rports Pag 3 Qualcomm Propritary Pag 3
Codbook dsign considrations Dual codbook structur to match antnna corrlation pattrns rlativly high corrlation btwn co-polarizd TX antnnas rlativly low corrlation btwn x-polarizd antnna sts scattring mostly around UE low RX corrlation 8 CSI-RS prcodrs follow Kronckr structur W - grid of bams within co-pol antnnas: x DFT vctors W 2-2x2 co-phasing matrics following lgacy dsign principl xtndd to TX in Rl-2 Fdback ovrhad rduction W : singl rportd valu across th ntir BW W 2 : sub-band PMI rporting nabld Pag Qualcomm Propritary Pag
UL MIMO in LTE Traffic: closd loop spatial multiplxing w/ up to four strams addition of CDM across DM-RS symbols to incras RS dimnsion prcoding codbook dsign following DL dsign principls addition of hot-bit prcodrs to nabl TX antnna slction constraints to prsrv SC-FDMA wavform Control: opn loop transmit divrsity orthogonal rsourcs allocatd for two transmit ports antnna virtualization for >2 transmit ports To dat no commrcial dploymnts supporting UL MIMO Pag 5 Qualcomm Propritary Pag 5
DL (MIMO) rcivr dsign Early MIMO prformanc spcifications assum LMMSE comptitiv analysis focusd on low/modrat mobility MIMO focus: singl cll, low corrlation, modrat CINR ( 3dB) Intrfrnc nulling rcivrs multi-cll valuation framwork dfind in RAN Rl-: intrfrnc rction combining (LMMSE-IRC) RX catgory Growing intrst in MIMO prformanc undr advrs conditions comptitiv analysis looks at wid rang of mobility / dlay sprad / antnna corrlation: EPA/EVA5L/H, EVA/ETU7L/H, ETU3L dlays sprads up to 5us, TX & RX corrlation up to.9 attntion to 3-dB CINR raising th bar for RF: I/Q mismatch, IPN Advancd UE catgoris furthr tightn prformanc rquirmnts Rl-2: rducd complxity ML (R-ML) rcivr as baslin prformanc rquirmnts basd on RX chain availability upcoming Pag 6 Qualcomm Propritary Pag 6
RX antnna managmnt tchniqus Antnna slction attracts attntion sinc arly days of MIMO cost & powr ffctiv way to improv prformanc & covrag howvr littl traction in WWAN industry for yars ral stat & layout considrations don t appal to OEMs cost & insrtion loss of xtra componnts Fatur volution of portabl dvics antnna sharing Wi-Fi intgration cross-tch antnna sharing LTA carrir aggrgation (CA) rquirs additional RX chains: facilitats antnna slction or combining Cross-tch antnna sharing framwork systm-wid optimization of antnna assignmnt on tch only activ (LTE or WiFi), diffrnt QoS (VoLTE w/ data on WiFi) LTE backhaul (MiFi) Pag 7 Qualcomm Propritary Pag 7
RX antnna slction fild rsults Throughput analysis w/ 2TX/cll and up to RX at th UE two cross-polarizd TX antnnas at NodB @ 2.7GHz smart-phon & laptop form factors, no hand blocking mix of indoor / outdoor masurmnts Gains w/ adaptiv 2 out of slction instantanous: 5% mdian & 3% (%) tail ms dlay: 5% mdian & 2% (%) tail 5ms dlay: 2% mdian & 2% (%) tail fixing primary antnna rtains most of th gain Slction or combining? ithr option is availabl for CA capabl UEs UE CA capability will oftn xcds th nd in most scnarios combining across multipl RX chains incurs substantial powr pnalty smart antnna slction & rcivr switching algorithms Pag 8 Qualcomm Propritary Pag 8
Towards highr ordr MIMO Currntly 2TX dploymnts dominat worldwid TDD: 8TX antnnas in China, yt configurd w/ 2CRS FDD: CRS trial NW in Europ (TMO), SKT pionrd commrcial CRS maor commrcial rollout of TX/CRS NWs xpctd latr this yar What to xpct w/ CRS? UE-RS mods ar dsignd to bttr scal w/ numbr of TX howvr TM9() ar not yt commrcially availabl CRS dploymnts long trm of transitional? Scnario Tst 2x2 x2 Nar cll MHz Cll dg MHz DL FTP (Mbps) 32.7 33. UL FTP (Mbps).. DL FTP (Mbps) 3.59 6.63 UL FTP (Mbps).2.9 Highr ordr spatial multiplxing yt to b sn Pag 9 Qualcomm Propritary Pag 9
Nw aras in DL MIMO Ntwork assistd intrfrnc cancllation Rl-2: signaling framwork to convy nighbor cll paramtrs to UEs in ordr to facilitat RS and/or data intrfrnc cancllation nighbor (virtual) cll IDs, CRS & MBSFN configuration, TM rstriction Rl-3: considr xtnding th sam for (intra-cll) MU-MIMO Highr ordr modulation schms 256QAM coming in Rl-2 Non-orthogonal multipl accss (NOMA) advancd MIMO transmission tchniqus.g. suprposition / DPC MMW MIMO aka massiv MIMO Pag 2 Qualcomm Propritary Pag 2
G MIMO: lssons larnd (/2) Avoid/minimiz pilot pollution in a broadband wirlss dsign broadband data ntworks ar partially loadd widband/continuous/scattrd pilots gnrat intrfrnc floor high cost of pilot intrfrnc mitigation maks htrognous dploymnts intractabl pilot collisions undrmins utility of channl fdback much RAN work ovr past fw yars focusd on mitigating th impact of common pilots (CRS) dsignd in Rl-8 Pay attntion to channl stat fdback dsign data ntworks tnd to oprat in low PHY BLER rgim accurat fdback is critical to highlight (advancd) rcivr gains inaccurat CQI partly mitigatd by NW rat control loops much hardr to fix incorrct rank Pag 2 Qualcomm Propritary Pag 2
G MIMO: lssons larnd (2/2) Dsign MAC w/ practical traffic bhavior in mind cllular systms hav bn mostly dsignd/valuatd undr full buffr modl bttr prformanc can b achivd w/ advancd coordination tchniqus Pag 22 Qualcomm Propritary Pag 22