IEEE Broadband Wireless Access Working Group < Draft Document for SC-FDE PHY Layer System for Sub 11 GHz BWA

Transcription

1 Projct Titl Dat Submittd IEEE Broadband Wirlss Accss Working Group < Draft Documnt for SC-FDE PHY Layr Systm for Sub 11 GHz BWA Sourc(s) Anadr Bnyamin-Syar Harris Corporation Inc. 3 Hotl d Vill Dollard-ds-Ormaux, Qubc, Canada, H9B 3G4 Co-Contributors: David Falconr David Shani, Mosh Ran, Vacit Arat, Eran Grson Dmos Kostas, Todd Carothrs Rmi Chayr, Juan-Carlos Zuniga Malik Audh, Frdrick Enns, Bob Furniss Jo Hakim, Subir Varma, Dan Chang Brian Eidson, Yoav Hbron, J-P Dviux Sirikat Lk Ariyavisitakul John Langly David Fishr, Jrry Krinock, Arvind Lonkar, Chin-Chn L, Manont Singh, Anthony Tsangaropoulos Paul Struhsakr, Russl McKown Garik Markarian, David Williams Igor Prlitch, Ed Kvork, Ray Andrson Robrt Malkms Alln Klin Dani Haimov Voic: (514) Fax: (514) mailto: abnyami@harris.com Institutions: Carlton nivrsity TlsciCOM Ltd. Adaptiv Broadband Corporation Harris Corporation Inc. Hybrid Ntworks, Inc. Aprto Ntworks Conxant Systms Inc Broadband Wirlss Solutions Com21, Inc Radia Communications Raz Tchnologis Advancd Hardwar Architcturs Advantch Sarnoff Wirlss tchnology SR-Tlcom InnoWav R: Abstract Purpos This contribution is submittd to th IEEE a Task Group as proposd baslin txt for th SC-FDE PHY part of Draft Standard for Sub 11 GHz BWA. This documnt includs rsolution of commnts submittd in rspons to th Call for Commnts issud against th prvious vrbsion ( /59r1). For rviw by th Task Group and adoption as baslin txt. 0

2 Notic Rlas Patnt Policy and Procdurs This documnt has bn prpard to assist IEEE It is offrd as a basis for discussion and is not binding on th contributing individual(s) or organization(s). Th matrial in this documnt is subjct to chang in form and contnt aftr furthr study. Th contributor(s) rsrv(s) th right to add, amnd or withdraw matrial containd hrin. Th contributor grants a fr, irrvocabl licns to th IEEE to incorporat txt containd in this contribution, and any modifications throf, in th cration of an IEEE Standards publication; to copyright in th IEEE s nam any IEEE Standards publication vn though it may includ portions of this contribution; and at th IEEE s sol discrtion to prmit othrs to rproduc in whol or in part th rsulting IEEE Standards publication. Th contributor also acknowldgs and accpts that this contribution may b mad public by IEEE Th contributor is familiar with th IEEE Patnt Policy and Procdurs (Vrsion 1.0) < including th statmnt IEEE standards may includ th known us of patnt(s), including patnt applications, if thr is tchnical justification in th opinion of th standardsdvloping committ and providd th IEEE rcivs assuranc from th patnt holdr that it will licns applicants undr rasonabl trms and conditions for th purpos of implmnting th standard. Early disclosur to th Working Group of patnt information that might b rlvant to th standard is ssntial to rduc th possibility for dlays in th dvlopmnt procss and incras th liklihood that th draft publication will b approvd for publication. Plas notify th Chair <mailto:r.b.marks@i.org> as arly as possibl, in writtn or lctronic form, of any patnts (grantd or undr application) that may covr tchnology that is undr considration by or has bn approvd by IEEE Th Chair will disclos this notification via th IEEE wb sit < 1

3 TABLE OF CONTENTS 1 Scop Introduction Gnral Singl Carrir PHY Faturs 6 3 Dscription of th SC-FDE PHY SC-FDE Wirlss Accss Systm Modl Multipl Accss Formats and Framing Physical Layr Framing Structurs MAC and PHY Intrfac Layr Downlink Mods of Opration MIMO Systms and Application of Bamforming Antnna Tchnology Singl-Carrir with Frquncy Domain Equalization (SC-FDE) Schm Singl Carrir-Frquncy Domain Equalization (SC-FDE) Compatibility of Singl Carrir (SC-FDE) and OFDM Th frquncy rang and th channl bandwidth Duplx Schms TDD: FDD: Downstram Channl Downstram Multipl Accss Schm Modulation Schms Downstram Randomization, Channl Coding & Intrlaving, Symbol Mapping and Basband Shaping pstram Channl pstram Multipl Accss pstram Modulation Format pstram Randomization, Channl Coding & Intrlaving, Symbol Mapping And Basband Shaping RF Propagation Charactristics RF Ntwork Topology 61 2

4 3.8.2 RF bands and Channlization Trrain catgory: RF propagation impairmnts: Minimum Prformanc Spcifications Antnna Systms Application of Smart Antnna Antnna Divrsity 62 4 SC-FDE Systm Capacity and Modulation Efficincy Systm Capacity: SC-FDE Systm Throughput 63 5 LINK Budgt Analysis Minimum (Multipath) Prformanc Main Faturs and Bnfits of th PHY Standard Similarity to othr standards: Statmnt on Intllctual Proprty Rights: Rfrncs: APPENDIX A: Channl Modl For BWA PHY Systms Dploymnt Modls RF Channl Modls Larg LOS Clls Larg NLOS Clls NLOS Small Clls Appndix B: Block Turbo and Rd-Solomon Coding Turbo Cod Dscription Rd Solomon Coding 85 3

5 PHY Layr Systm for Singl Carrir Frquncy Domain Equalizr for Sub 11 GHz BWA (An OFDM Compatibl Solution) Contributors: Anadr Bnyamin-Syar, Rmi Chayr, Juan-Carlos Zuniga David Falconr David Shani, Mosh Ran, Vacit Arat, Eran Grson Dmos Kostas, Todd Carothrs Malik Audh, Frdrick Enns, Bob Furniss Jo Hakim, Subir Varma, Dan Chang Brian Eidson, Yoav Hbron, J-P Dviux Sirikat Lk Ariyavisitakul John Langly David Fishr, Jrry Krinock, Arvind Lonkar, Chin-Chn L, Manont Singh, Anthony Tsangaropoulos Paul Struhsakr, Russl McKown Garik Markarian, David Williams Igor Prlitch, Ed Kvork, Ray Andrson Robrt Malkms Alln Klin Dani Haimov, zi Padan Institutions: Harris Corporation Inc. Carlton nivrsity TlsciCOM Ltd. Adaptiv Broadband Corporation Hybrid Ntworks, Inc. Aprto Ntworks Conxant Systms Inc Broadband Wirlss Solutions Com21, Inc Radia Communications Raz Tchnologis Advancd Hardwar Architcturs Advantch Sarnoff Wirlss tchnology SR-Tlcom InnoWav 1 Scop This documnt dfins a Physical Layr (PHY) for IEEE802.16a Broadband Wirlss Accss (BWA) systms in licnsd frquncy bands from 2-11GHz. Fixd BWA is a communication systm that provids digital two-way voic, data, and vido srvics. Th BWA markt targts wirlss multimdia srvics to hom offics, small and mdium-sizd businsss and rsidncs. Th BWA systm shall b a point-to-multipoint architctur compris of Subscribr Stations (SS) and Bas Stations (BS, Hub station). Figur 1.1 illustrats a BWA rfrnc modl. 4

6 2 Introduction 1 Figur 1.1: Wirlss Accss Rfrnc Modl 2.1 Gnral This documnt will addrss th SC FDE PHY in dtail and will highlight th addd OFDM Compatibility Faturs. Th draft documnt dscribs th Singl Carrir (SC) PHY systm which adopts TDM/ TDMA bandwidth sharing schm. Th signal is transmittd downstram from th Bas Station to all assignd Subscribr Stations using a carrir frquncy in broadcast Tim Division Multiplx (TDM) mod. Th upstram signal is burst from th Subscribr Station sharing th sam RF carrir with othr assignd Subscribr Stations to th Bas Station in Tim Division Multipl Accss (TDMA) mod. This accss schm can b ithr FDD or TDD. Both duplxing schms hav intrinsic advantags and disadvantags, so for a givn application th optimum duplxing schm to b applid dpnds on dploymnt-spcific charactristics, i.., bandwidth availability, Tx-to-Rx spacing, traffic modls, and cost objctivs. Oprating frquncy band will b from 2 to 11 GHz and th Bas Station can us multipl sctors and will b capabl of supporting smart antnna in th futur. Th PHY layr uss a Singl Carrir (SC) modulation with a Frquncy Domain Equalizr (FDE) (or SC FDE). W hav shown that SC-FDE modulation can offr as good or bttr prformanc than Orthogonal Frquncy Division Modulation (OFDM) tchnology in solving th Non-Lin of Sight (NLOS) problm that may aris in th 2 to 10.5 GHz frquncy bands (S rfrncs [36 and 37]). In addition, this documnt discusss th compatibility btwn of th SC FDE and OFDM modulation schms for Sub 11 GHz BWA applications. Furthrmor, th prsntd fram structur in this draft documnt has all th 5

7 capabilitis for adaptiv modulation and coding. Th main objctiv of th fram structur has bn making th PHY almost indpndnt from th MAC. Th PHY hr is basd upon utilizing th structur of th MAC. 2.2 Singl Carrir PHY Faturs Th Singl Carrir PHY is a Broadband Wirlss Accss (BWA) Point-to-Multipoint communication systm that can provid digital, two-way voic, data, Intrnt and vido srvics. This PHY shall offr an ffctiv altrnativ to traditional wir lin (cabl or DSL) srvics. Employing th functions of th MAC such as QoS, th BWA systm using th PHY hr will support srvics; such as packt data and Constant Bit Rat (CBR) as wll as T1-E1, POTS, wid band audio and vido srvics. To maximiz th utilization of limitd spctrum rsourcs in th low frquncy bands (2 to 11 GHz), th airintrfac supports upstram statistical multiplxing ovr th air-intrfac using Tim Division Multipl Accss (TDMA) tchnology. Th ky faturs of th PHY ar th following: Full compatibility with th MAC. pstram multipl accss is basd on TDMA schm. Downstram multipl accss is basd on broadcast TDM schm. Duplxing is basd on ithr TDD or FDD schm. PHY uss a block adaptiv modulation and FEC coding in both pstram and Downstram paths. High capacity singl carrir modulation with frquncy Domain Equalization (SC-FDE) in addition to Dcision Fdback Equalization in th tim domain. Th us of singl carrir modulation tchniqus can rsult in low cost Subscribr Stations (SS) and Bas Stations (BS). Th modulation schm is robust in multi-path and othr channl impairmnts Th PHY is flxibl in trms of gographic covrag, in th us of frquncy band, and capacity allocation. Bas Station can us multipl sctor antnnas. Support for futur us of smart antnnas is fasibl and is implicit in th PHY dsign. Th PHY can asily accommodat multi-bam and antnna divrsity options; such as Multipl-In Multipl-Out (MIMO) and Dlay divrsity. Th SC -FDE PHY has an addd fatur of r-configurability to support OFDM modulation. For svr multipath, Singl Carrir QAM with simplifid frquncy-domain qualization prforms at last as wll as OFDM (bttr for uncodd systms). Frquncy domain linar qualization has ssntially th sam complxity as uncodd OFDM, with bttr prformanc in frquncy slctiv fading, and without OFDM s inhrnt backoff powr pnalty. A Compatibl frquncy domain rcivr structur can b programmd to handl ithr OFDM or Singl Carrir. Downlink OFDM / uplink singl carrir may yild potntial complxity rduction and uplink powr fficincy gains rlativ to downlink OFDM / uplink OFDM. 6

8 3 Dscription of th SC-FDE PHY As dscribd in th Functional Rquirmnt Documnt [1], quipmnt mploying this PHY and th MAC hav bn dsignd to addrss th critical paramtrs for srving singl family rsidntial, SOHO, small businsss and multi-tnant dwllings customrs--using Broadband Wirlss Accss tchnology. Ths critical paramtrs ar combination of covrag, capacity and quipmnt cost factors that affct total cost pr usr. Th PHY facilitats dployability, maintainability, and product costs associatd with th customr prmis installation, and th spctrum fficincy and rus for conomically srving th rquird numbr of customr locations. Of particular importanc to th PHY prsntd hr is th inhrnt vrsatility implicit in th Frquncy Domain Equalizr (FDE) architctur. Concptually, a dual mod rcivr could b implmntd in which th FDE configuration could b changd to rciv an OFDM signal. Th bass for this approach ar shown in Figur SC-FDE Wirlss Accss Systm Modl Figur 3.1 is a top lvl block diagram of th PHY layr systm for BWA srvics. Figur 3.1a is an illustration for Singl carrir systm and Figur 3.1b is th Compatibl OFDM systm. Data In Basband Intrfac Data Scramblr FEC Encod & Intrlavr Modulator pconvrtr & Synthsizrs Powr Amplifir Multipath Wirlss Channl AWGN Low Nois Amplifir Downconvrtr & Synthsizrs Carrir Rcovry & Dmod Frquncy & Tim Domain Equalizrs FEC Dcod & D- Intrlavr Data Dscramblr Basband Intrfac Data Out Figur 3.1a: Th Singl Carrir PHY Layr Block Diagram. 7

9 E r c g ( c _ 2 9 r 1 ) P a t h L o s s M o d l ( 3 0 m B T S, 6. 5 m S S h t s ) Path Loss (db) R a n g ( k m ) M i n P a t h L o s s M a x P a t h L o s s 4 / 3 E a r t h L O S Figur 3.1b: Th Compatibl OFDM and Singl Carrir PHY Proposal Block Diagram. 3.2 Multipl Accss Formats and Framing In this Sction, w introduc multipl accss formats, and th PHY framing and MAC/ PHY intrfac structurs ncssary to accommodat ths formats. Sction dscribs th PHY framing structurs and sub-lmnts usd to support various multipl accss formats; Sction dscribs th MAC/PHY intrfac, and gos into dtails on th supportd multipl accss formats. In addition, Sction dscribs th us of adaptiv antnna tchnology Physical Layr Framing Structurs Ovrviw of Fram Formats and Thir Application Starting with a simpl fundamntal fram componnt and two formats, w construct PHY structurs that may b applid to svral multipl accss tchniqus. Two fundamntal PHY block format options ar availabl: 1. on usd for continuous transmissions, and 2. anothr usd for burst transmissions. As w shall vntually dmonstrat, th continuous transmission format might b usd on th downstram of on typ of a FDD systm. 8

10 Th burst format might b sn on th upstram of a FDD systm; or th upstram and downstram of a TDD systm; or th downstram of a burst-fdd systm. Th burst format may b furthr catgorizd into two subformats: 1. TDMA burst, and 2. TDM burst. A TDMA burst contains information intndd for on audinc. This audinc could b a singl usr, or a group of usrs rciving a broadcast mssag. In contrast a TDM burst gnrally contains multiplxd, concatnatd information addrssd to multipl audincs. A TDMA burst may, in fact, b intrprtd as a typ of TDM burst; howvr, bcaus of diffrncs rlatd to usag of adaptiv modulation, MAC mssaging and multipl accss, w shall in som sctions choos to discuss ths two burst typs sparatly Continuous Transmission Format As its nam suggsts, th continuous transmission format is utilizd for a continuous channl, which may b monitord, for xampl, by all of th Subscribr Stations (SSs) within a Bas Station (BS) cll sctor. In particular, on might s this format applid in th opration of a (continuous) FDD downstram channl niqu Word: Intrval Rquirmnts and sag On charactristic of th continuous transmission format is illustratd in Figur 3.1: th continuous format has a fundamntal pattrn that rpats. This pattrn consists of N-ol payloads sparatd by -ol niqu Words. niqu Word rpatd Evry N ols N N Payload Payload... W (and optional xtra pilot W (and optional xtra pilot ols) ols)... 2 Figur 3.1 niqu Word Intrvals for Continuous Format 9

11 niqu Word Intrval Rquirmnts A niqu Word is a contiguous, lngth- squnc of known ols, which ar not FEC-ncodd. A niqu Word is rpatd at a rgular intrval, N. Th intrval btwn th niqu Words is typically chosn to accommodat rcivrs using frquncy domain qualization, with F = N+ ols qualing th block lngth ovr which an FFT would b computd by a frquncy domain qualizr. To rduc computational rquirmnts of FFTs, th lngth F = N + should prfrably b 2 raisd to an intgr powr. Additional dtails on th composition of th ols within niqu Words, and thir accptd lngths,, may b found in Not that 0 is also an accptabl valu for th lngth. Additional dtails on accptd lngths for F may b found in Onc th paramtrs for and N (via F) ar st, thy should not b changd. In th vnt that ths paramtrs must b changd, rcivr rsynchronization may b ncssary niqu Word sag Th niqu Word may b usd as a cyclic prfix by a frquncy domain qualizr, and/or as pilot ols. Whn usd as a cyclic prfix, a niqu Words should b at last b as long as th maximum dlay sprad of a channl. As pilot ols, th niqu Words may assist in th stimation of dmodulation paramtrs such as stimating qualizr channl cofficints, carrir phas and frquncy offsts, ol timing, and optimal FFT window timing (in a frquncy domain qualizr). Th niqu Words may also assist in th acquisition of a channl Fram Hadr Indication Squnc: Rquirmnts and sag In addition to niqu Word intrvals, continuous format data is furthr framd into MAC-basd frams, and ths MAC fram boundaris ar dlinatd by a Fram Hadr Indication Squnc Fram Hadr Indication Squnc Rquirmnts As illustratd in Figur 3.2: Fram Hadr Indication Squncs of lngth H ar priodically rpatd, with rptition intrval I. Th rptition intrval, I, for a Fram Hadr Indication Squnc must b an intgr numbr of F = N+ niqu Word intrvals. Furthrmor, as Figur 3.3 illustrats, a Fram Hadr Indication Squnc must dirctly follow a niqu Word squnc.... H Fram Hadr Indication Squnc Intrval btwn Fram Hadrs (I ) Transportd Fram H Fram Hadr Indication Squnc Intrval btwn Fram Hadrs (I ) Transportd Fram... 3 Figur 3.2 Fram Hadr Intrvals for Continuous Format 10

12 W cyclic xtnsion Rquirmnt: Fram hadr must b distinct from W-followd bypilot concatnation rpatd within usr fram data. Implication: H > + P W Fram Hadr Indication Squnc H Bginning of Fram (Data within MAC hadr) W N 4 Figur 3.3 Fram Hadr Indication Squnc Position within a niqu Word Intrval Th Fram Hadr Indication Squnc is a contiguous squnc of known ols, which ar not FECncodd. As Figur 3.3 furthr indicats, th Fram Hadr Indication Squnc is a cyclic xtnsion of th niqu Word which implis that it is ithr a rptition of th niqu Word, or a partial rplication of th first H ols of th niqu Word, or a combination of a rptition and partial rplication of th niqu Word. Morovr, th Fram Hadr Indication Squnc must b longr than a squnc of additional pilot ols which may b contiguous to nsuing niqu Words within th data payload (s Figur 3.5 for dtails on th addition of xtra pilot ols). Onc th paramtrs for H and I ar st, thy should not b changd. In th vnt that ths paramtrs ar changd, rcivr rsynchronization may b ncssary Fram Hadr Indication Squnc sag As indicatd , MAC fram boundaris ar dlinatd by th Fram Hadr Indication Squnc. Idntification of th location of th MAC hadr is important during acquisition, bcaus th MAC hadr contains much of th systm and fram control information, including MAPs of usr data, thir lngths, modulation formats, and th FEC usd to ncod thm. Thrfor, onc th MAC hadr is locatd and dcodd, all nsuing usr data that has th CINR to b dcodabl can b dcodd. This bgs that th Fram Hadr Indication Squnc b distinct, so that th location of th fram hadr may b asily idntifid, and distinguishd from pilot ols. What s mor, th Fram Hadr Indication Squnc has a rol following initial acquisition. Th structur (usag of niqu Word lmnts) and placmnt of th Fram Hadr Indication Squnc also nabls r-acquisition and channl stimation bfor th outst of a subsqunt MAC fram. This is important whn pr-usr adaptiv modulation is usd, bcaus, as indicatd in , usr data is squncd in trms of modulation robustnss. Thrfor, rcivrs xprincing low CINRs may not b abl to track compltly through a MAC fram. Th Fram Hadr Acquisition Squnc aids such a rcivr in racquiring, or gtting a bttr, mor solid channl stimat, bfor th apparanc of data that it has th CINR to succssfully dcod. 11

13 Adaptiv Modulation Concpt of Adaptiv Modulation Many SSs ar intndd to rciv th continuous downstram channl. Du to diffring conditions at th various SS sits (.g., variabl distancs from th BS, prsnc of obstructions, local intrfrnc), SS rcivrs may obsrv significantly diffrnt CINRs. For this rason, som SSs may b capabl of rliably dtcting (non-pilot) payload data only whn it is drivd from crtain lowr-ordr modulation alphabts, such as QPSK. Similarly, CINR-disadvantagd SSs may rquir mor powrful and rdundant FEC schms. On th othr hand, CINR-advantagd stations may b capabl of rciving vry high ordr modulations (.g., 64-QAM), with high cod rats. Obviously, to maximiz th ovrall capacity of th systm, th modulation and coding format should b adaptd to ach class of SS, basd on what th SS can rciv rliably. Dfin th adaptation of modulation typ and FEC to a particular SS (or group of SSs) as 'adaptiv modulation', and th choic of a particular modulation and FEC as an 'adaptiv modulation typ.' Th continuous transmission mod (as dos th burst transmission mod) supports adaptiv modulation and th us of adaptiv modulation typs Fram Control Hadr Information and Adaptiv Modulation As Figur 3.4 illustrats, Fram Control MAC mssags ar priodically transmittd ovr th continuous channl, using th most robust adaptiv modulation typ supportd. Among othr information, ths Fram hadrs provid adaptiv modulation typ formatting instructions. As dscribs, in ordr that Fram hadrs may b asily rcognizd during initial channl acquisition or r-acquisition, th transmittr PHY insrts an uncodd Fram Hadr Indication Squnc immdiatly bfor th Fram hadr, and immdiatly aftr a niqu Word. Figur 3.4 illustrats this point, as wll Adaptiv Modulation Squncing Within th MAC Fram hadr, a PHY control map (DL_MAP) is usd to indicat th bginning location of ach of adaptiv modulation typ payload that follows. Howvr, th DL_MAP dos not dscrib th bginning locations of th payload groups that immdiatly follow; it dscribs th payload distributions at som MAC-prscribd tim in th futur. This dlay is ncssary so that FEC dcoding of MAC information (which could b itrativ, in th cas of turbo cods) may b compltd, th adaptiv data intrprtd, and th dmodulator schduling st up for th propr squncing. As Figur 3.4 illustrats, following th MAC Fram hadr, payload groups ar squncd in incrasing ordr of robustnss (.g., first QPSK, thn 16-QAM, thn 64-QAM). This robustnss squncing improvs rcivr prformanc, bcaus it nabls rcivrs xprincing lowr CINRs to track only through th modulation typs that thy can rliably rciv. This squncing also facilitats changs of modulation typ at locations that ar not contiguous to niqu Word boundaris. 12

14 ... H Fram Hadr Indication Squnc Intrval btwn Fram Hadrs (I ) Transportd Fram... MAC Fram Hadr (Broadcast) sr Data sr Data Squncd in Dcrasing ordr of 'modulation typ' robustnss (.g., QPSK, 16-QAM, 64-QAM; or 1.5 bits/, 2.5 bits/, tc.) Most Robust Modulation Typ 5 Figur 3.4 Adaptiv Modulation Squncing within a Continuous Mod Fram W Boundary-fr Transitions Btwn Modulation Typs Not also that adaptiv modulation typ-to-othr-modulation typ changs ar not rstrictd to occur only at niqu Word boundaris. Thy may chang anywhr that th DL_MAP mssag indicats that thy should chang Pr-Adaptiv-Modulation-Typ FEC Encapsulation So that disadvantagd-snr SSs ar not advrsly affctd by transmissions intndd for othr advantagd-cinr usrs, FEC blocks nd whn a particular adaptiv modulation typ nds. Among othr things, this implis that th FEC intrlavr dpth and cod blocks ar adaptd to accommodat th span of a particular adaptiv modulation typ. Not, howvr, that data from svral usrs could b concatnatd by th MAC (and intrlavd togthr by th PHY) within th span of a givn adaptiv modulation typ MAC Hadr FEC Encapsulation So that th MAC hadr data may b dcodd by a rcivr that has just acquird (and dos not yt know th modulation lngths and distributions of usr data), th MAC hadr data should b 1. a fixd, a priori-known block siz; and 2. sparatly FEC-ncodd (and intrlavd) from all othr usr-spcifically-addrssd data Empty payloads Whn data is not availabl for transmission, part of a payload may b stuffd with dummy data, or lft mpty, at th systm oprator s discrtion. Howvr, th transmittr cannot shut compltly down. Th 13

15 uniqu words ar always transmittd, so that all listning SSs may track th channl, and maintain synchronization Additional Pilot Symbols Whn multipath dlay sprad spans almost th ntir niqu Word intrval, vry littl data rmains that is not uncorruptd by dlay sprad from th arbitrary, a priori unknown payload ols. In such an nvironmnt, non-dcision aidd channl (dlay profil) stimation could bcom xcdingly difficult. On rcours is th incrasd utilization of dcision-aidd channl stimation. To add an xtra masur of robustnss, many systm oprators may prfr, instad, to opt for th addition of P additional pilot ols. For this rason, th addition of an xtra P pilot ols pr niqu Word intrval is an option, as contiguous cyclic xtnsions of th niqu Word. A contiguous cyclic xtnsion of P ols implis that it th pilots ar ithr a rptition of th niqu Word, or a partial rplication of th first P ols of th niqu Word, or a combination of a rptition and partial rplication of th niqu Word. Figur 3.5 illustrats thr cass whr pilot ols hav bn addd: on for a cas whn only a fw ols hav bn addd, anothr whr th numbr of addd pilot ols and niqu Word ols ar th sam (i.., th niqu Word has bn rplicatd), and on for a cas whr th numbr of pilot ols is much gratr than th numbr of niqu Word ols (i.., whr th W is rplicatd at last onc, thn cyclically xtndd.) Not that it is also possibl to add zro xtra pilot ols. Th rang of limits for P ar 0 P N. 14

16 Cyclic xtnsion of W usd as pilot ols; pilots always appar at bginning of 'payload & pilots' block, immdiatly following W Payload & Pilot Symbols N s W Pilot Symbols [partial cyclic xtnsion of W] Payload N-P s niqu Word P< Payload & Pilot Symbols N W Pilot Symbols [full cyclic xtnsion (rplication) of W] Payload N-P = N-... P= Payload & Pilot Symbols N s W Pilot Symbols (rplication and cyclic xtnsion of W) Payload N-P s P> 6 Figur 3.5 Thr xampls whr xtra pilot ols hav bn addd, via cyclic xtnsion of th niqu Word [W]. (top) pilots ols lss than W ols; (middl) pilot ols qual to W ols; (bottom) pilot ols gratr than W ols. Not that th numbr of additional pilot ols, P, usd pr N-ol intrval (in th continuous mod) may not chang. In th vnt that ths paramtrs must b changd, rcivr rsynchronization may b ncssary. Additional dtails on th composition of th ols within niqu Words, and thir accptd lngths,, may b found in Additional dtails rlatd to accptd lngths for F = N + (whr N is th intrval btwn niqu Word rptitions) may b found in Burst Transmission Format In addition to th continuous transmission format, a scond transmission format xists: th burst transmission format. As its nam implis, th burst transmission format is utilizd for burst transmissions, all of which may or may not b monitord by all SSs within a BS cll sctor. In th broadband wirlss application, on might s bursts on th (multipl-accss) upstram, a TDD upstram and downstram, or a burst-fdd downstram. As dscribd in th MAC/PHY Intrfac Layr Dscription in Sction 3.2.2, half duplx burst FDD opration is also possibl using this format. 15

17 Both TDMA and TDM burst options ar supportd. As Figur 3.8 dmonstrats, a TDMA burst contains information intndd for on audinc. This audinc could b a singl usr, or a group of usrs rciving a broadcast mssag. In contrast, as Figur 3.8 also dmonstrats, a TDM burst gnrally contains multiplxd, concatnatd information that is gnrally addrssd to multipl audincs. A TDMA burst may, in fact, b intrprtd as a typ of TDM burst; howvr, du to thir diffrncs in aras such as adaptiv modulation, multipl accss, and MAC mssaging, w shall trat ths two burst typs sparatly. TDMA:Pr-Burst Payload TDMA:Pr-Burst Payload TDMA1: Singl Payload/On Modulation Typ,.g., QPSK TDMA2: Singl Payload/On Modulation Typ,.g., 64-QAM TDM1: QPSK Payload TDM2: 64-QAM Payload TDM: Contiguous Multipl Payloads within a burst 7 Figur 3.6 Exampl Comparison of TDMA and TDM bursts Burst Ramping: Ramp-p and Ramp-Down Bursts bgin with a ramp-up squnc, and nd with a ramp-down squnc, ach of lngth R ols. Th slction for R is lft to th systm oprator. Th slction for R may b basd on svral factors, such as rgulatory rquirmnts rlatd to adjacnt channl nrgy spillag, powr amplifir considrations, antnna divrsity snsing and switching dlays, and th lngth of th startup transint of th transmit filtr. In crating th ramp-up squnc, th transmit filtr is initially filld with zro-valud (null) ols, and thn dsird transmit data ols ar pushd into th systm to naturally ramp th systm powr up to its full valu. If a ramp-up squnc lngth shortr than on-half th lngth of th impuls rspons of th transmit filtr is dsird, th transmit filtr output sampls rlatd to first fw ols may b supprssd and a rampd powr buildup achivd by windowing th ramp-up squnc, using a raisdcosin window of th dsird lngth R, for xampl. 16

18 In crating th ramp-down squnc, zro-valud (null) ols ar pushd into th transmit filtr data path following th last dsird transmit ol. If a ramp-down squnc lngth shortr than on-half th lngth of th impuls rspons of th transmit filtr is dsird, th transmit filtr output sampls in th ramp-down rgion may b windowd, using a raisd-cosin window of th dsird lngth R, for xampl niqu Word: Intrval Rquirmnts and sag A niqu Word is a contiguous, lngth- squnc of known ols, which ar not FEC-ncodd. In th middl portions of a burst, a niqu Word is gnrally rpatd at a rgular intrval, N. Th intrval btwn th niqu Words is typically chosn to accommodat rcivrs using frquncy domain qualization, with F = N+ ols qualing th block lngth ovr which an FFT would b computd by a frquncy domain qualizr niqu Word: Intrval Rquirmnts Lik th continuous transmission format illustratd in Figur 3.1, th middl portions of a burst contain a fundamntal pattrn consisting of N-ol Payloads sparatd by -ol niqu Words. In th cas of a short burst, this fundamntal pattrn may b no mor than a singl niqu Word-Payload- niqu Word combination. For longr bursts, this may b a niqu Word-Payload-niqu Word- Payload (niqu Word-Payload) niqu Word-Payload-niqu Word combination. Not that th pattrnd middl portion of th block must always commnc and conclud with a niqu Word. All payload blocks within a burst xcpt, potntially, th last payload block, must b of th sam lngth, N. To rduc computational rquirmnts of FFTs for frquncy domain qualizrs, th lngth F = N + should prfrably b 2 raisd to an intgr powr. nlik th continuous transmission format, howvr, th final payload block nd not b th sam lngth as th othr payload blocks. It may b shortnd to a lngth N nd. This accommodats finr ovrall block lngth granularitis. Mor dtails on shortning may b found in and its subsctions. nlik th continuous format, th paramtrs in us for, F, and F nd usd by th burst format can potntially b modifid on a burst-by-burst basis---if th MAC mssaging MAPs for burst profils so allow. Additional dtails on th composition of th ols within niqu Words, and thir accptd lngths,, may b found in Not that 0 is also an accptabl valu for th lngth. Additional dtails on accptd lngths for F and F nd may b found in Variabl Burst Sizs A charactristic of th burst format is that, for fficint opration, it may b ncssary to accommodat many diffrnt burst sizs. Ths burst sizs could b diffrnt from som intgr multipl of th nominal FFT siz, F =N +, of a frquncy domain qualizr. 17

19 Variabl Burst Sizs and Frquncy Domain Equalizrs Evn for implmntations using a frquncy domain qualizr, th singl carrir burst PHY using frquncy domain has som flxibility in this rgard. For mssags intndd for a rcivr with a frquncy domain qualizr, th final payload block can b shortnd to th lngth N nd, undr th constraints N nd + = 2 n, n is an intgr, and 2 n Variabl Burst Sizs and Tim Domain Equalizrs For rcivrs using tim domain qualizrs (such as dcision fdback qualizrs), th shortnd lngth of th last block, N nd, can b compltly arbitrary, and is only limitd by MAC packt lngth granularity rstrictions Variabl Lngth Ngotiation Exchang of information rgarding rcivr capabilitis during initial rgistration is on mthod to nsur that mssag granularitis always conform to a burst rcivr s capabilitis to procss thm Broadcast/Multicast Mssags Broadcast or multicast mssags would always b snt assuming a frquncy domain qualizr s granularity limitations, sinc thos limitations ar mor rstrictiv niqu Word sag Th niqu Word may b usd as a cyclic prfix by a frquncy domain qualizr, and/or as pilot ols. Whn usd as a cyclic prfix, a niqu Words should b at last b as long as th maximum dlay sprad of a channl. As pilot ols, th niqu Words may assist in th stimation of dmodulation paramtrs such as stimating qualizr channl cofficints, carrir phas and frquncy offsts, ol timing, and optimal FFT window timing (in a frquncy domain qualizr) Additional Pilot Symbols Whn multipath dlay sprad spans almost th ntir niqu Word intrval, vry littl data rmains that is not uncorruptd by dlay sprad from th arbitrary, a priori unknown payload ols. In such an nvironmnt, non-dcision aidd channl (dlay profil) stimation could bcomxcdingly difficult. On rcours is th incrasd utilization of dcision-aidd channl stimation. To add an xtra masur of robustnss, many systm oprators may prfr, instad, to opt for th addition of P additional pilot ols. For this rason, th addition of an xtra P pilot ols pr niqu Word intrval is an option, as contiguous cyclic xtnsions of th niqu Word. A contiguous cyclic xtnsion of P ols implis that it th pilots ar ithr a rptition of th niqu Word, or a partial rplication of th first P ols of th niqu Word, or a combination of a rptition and partial rplication of th niqu Word. 18

20 Figur 3.7 illustrats thr cass whr pilot ols hav bn addd: on for a cas whn only a fw ols hav bn addd, anothr whr th numbr of addd pilot ols and niqu Word ols ar th sam (i.., th niqu Word has bn rplicatd), and on for a cas whr th numbr of pilot ols is much gratr than th numbr of niqu Word ols (i.., whr th W is rplicatd at last onc, thn cyclically xtndd.) Not that it is also possibl to add zro xtra pilot ols. Th rang for th addition of pilot ols, P, is 0 P N. Cyclic xtnsion of W usd as pilot ols; pilots always appar at bginning of 'payload & pilots' block, immdiatly following W Payload & Pilot Symbols N s W Pilot Symbols [partial cyclic xtnsion of W] Payload N-P s niqu Word P< Payload & Pilot Symbols N W Pilot Symbols [full cyclic xtnsion (rplication) of W] Payload N-P = N-... P= Payload & Pilot Symbols N s W Pilot Symbols (rplication and cyclic xtnsion of W) Payload N-P s P> 8 Figur 3.7 Thr xampls whr xtra pilot ols hav bn addd, via cyclic xtnsion of th niqu Word [W]. (top) pilots ols lss than W ols; (middl) pilot ols qual to W ols; (bottom) pilot ols gratr than W ols. Th numbr of additional pilot ols, P, pr N-ol intrval within a particular burst, shall b fixd for that burst. Morovr, many oprators may fix P to b th sam for all bursts. Howvr, this dos not hav to b th cas. P may chang from burst to burst, at th discrtion of, and by dirction from, th MAC. This information would b containd in th MAC s MAP information, in th fild that provids burst profils. Additional dtails on th composition of th ols within niqu Words, and thir accptd lngths,, may b found in Additional dtails rlatd to accptd lngths for F = N + (whr N is th intrval btwn niqu Word rptitions) may b found in

21 Burst Elmnt Dtails Including th Acquisition Prambl A burst conforming to th TDM or TDMA burst format is illustratd in Figur 3.8. Not that th burst may b long or short. In othr words, it may consist of multipl niqu Word Intrvals of lngth F = N + (i., multipl FFTs for a frquncy domain qualizr) plus on xtra prfixing niqu Word, or a singl niqu Word Intrval of lngth F = N + (singl FFT for a frquncy domain qualizr) plus on xtra prfixing niqu Word. Th final payload sction may also b shortnd. Additional dtails on th us and intrvals of niqu Words within burst formats may b found in As Figur 3.8 illustrats may possss an optional acquisition prambl, of lngth A ols. This optional prambl must b composd of niqu Word ols that ar a contiguous cyclic xtnsion of th niqu Word which follows th prambl. In othr words, this contiguous cyclic xtnsion of A ols implis that if A=, thn th prambl is a rptition of th niqu Word; if A<, thn th prambl is a partial rplication of th last A ols of th niqu Word; othrwis, th prambl is a combination of a rptition and partial rplication of th last ols in th niqu Word. Not that th ramp-up squnc as dscribd in may b drivd in part from this acquisition prambl, if all zro ol (null) inputs ar supprssd from by th ramp-up windowing squnc. Burst profil paramtrs dlivrd by th MAC dictat th lngth of th acquisition prambl. Th nominal lngth of A, usd in broadcast systm mssags containing MAC MAP information, is TBD. FFT intrval for FDE block F = + N FFT intrval for FDE block F = + N FFT intrval for FDE block F = + N Shortnd FFT intrval for final FDE block F = + N nd Cyclic Ramp p; (containd in Acq Pramb or in 1st W; TX filtr input initializd with zros) R R A Acqusition Prambl (optional; cyclic xtnsion of W which follows) Acquisition Squnc (W can b rusd) W N Payload (& Optional Pilots) W N Payload (& Optional Pilots) W... sr Data W N Payload (& Optional Pilots) W N nd Shortnd Payload (& Optional Pilots) W R R D Ramp Down (clar TX filtr with zros) 9 Figur 3.8 TDM/TDMA burst format: lmnt locations and dtails As Figur 3.8 illustrats, th ramp-down squnc is xtrnal to th final FFT intrval which might b usd by a frquncy domain qualizr. illustrats anothr burst approach (profil), which uss lss ovrhad. In this approach, th burst-nding niqu Word is liminatd, and rplacd by -ol idl data rgion, within which no data is transmittd. A part of this idl rgion is th ramp down; th ramp down dirctly follows th final databaring sction. Th idl intrval is ncssary for dlay sprad to clar th rcivr. Not that th idl rgion may b usd in rcivr procssing to intgrat mor dlay sprad nrgy into th dcision- 20

22 making (and qualization) procsss.. As was th cas for Figur 3.8, th lngth N nd in should b chosn such that lngth N nd + adhrs to th lngth guidlins in 0. FFT intrval for FDE block F = + N FFT intrval for FDE block F = + N Cyclic Ramp p; (containd in Acq Pramb or in 1st W; TX filtr input initializd with zros) R R A Acqusition Prambl (optional; cyclic xtnsion of W which follows) Acquisition Squnc (W can b rusd) W N N Payload Payload... (& Optional Pilots) W (& Optional Pilots) sr Data W N Payload (& Optional Pilots) W N nd R Shortnd Payload (& Optional Pilots) R D DS & RD Ramp Down (clar TX filtr with zros) Intrval for Ramp Down and Dlay Sprad to Clar Rcivr 10 Figur 3.9 Exampl of altrnativ TDM/TDMA burst format whr final W is liminatd, th ramp down intrval is advancd, and, in plac of th final W, an idl rgion is insrtd Dtails Prtinnt to TDMA Bursts A TDMA burst will support only a singl modulation typ in its data payload, sinc all bursts ar addrssd to a singl audinc. Howvr, subsqunt bursts may b transmittd using a diffrnt modulation typ. What s mor, th numbr of ols in th acquisition prambl, if any, may b dpndnt on th burst profil assignd for ithr that modulation typ, or th burst profil for th particular usr bing addrssd by th TDMA burst. Such usr profil data would b snt in control bursts, addrssd ithr to a particular usr, or to all usrs in th systm, as a whol Dtails Prtinnt to TDM Bursts Som dtails, such as adaptiv modulation, ar only prtinnt to th TDM burst format---sinc th TDMA format only supports a broadcast to on audinc Adaptiv Modulation Squncing for TDM bursts Within th MAC Fram hadr, a PHY control map (MAP) is usd to indicat th bginning location of ach of adaptiv modulation typ payload that follows. Howvr, th MAP dos not dscrib th bginning locations of th payload groups that immdiatly follow; it dscribs th payload distributions at som MAC-prscribd tim in th futur. This dlay is ncssary so that FEC dcoding of MAC information (which could b itrativ, in th cas of turbo cods) may b compltd, th adaptiv data intrprtd, and th dmodulator schduling st up for th propr squncing. Not that this information containing th distribution of data within a particular burst may b containd in anothr burst. Within a burst, payload groups ar squncd in incrasing ordr of robustnss (.g., first QPSK, thn 16-QAM, thn 64-QAM). This robustnss squncing improvs rcivr prformanc, bcaus it nabls rcivrs xprincing lowr CINRs to track only through th modulation typs that thy can rliably 21

23 rciv. This squncing also facilitats changs of modulation typ at locations that ar not contiguous to niqu Word boundaris W Boundary-fr Transitions Btwn Modulation Typs (TDM) Not also that adaptiv modulation typ-to-othr-modulation typ changs ar not rstrictd to occur only at niqu Word boundaris. Thy may chang anywhr that a MAC MAP mssag indicats that thy should chang Pr-Adaptiv-Modulation-Typ FEC Encapsulation (TDM) So that disadvantagd-snr SSs ar not advrsly affctd by transmissions intndd for othr advantagd-cinr usrs, FEC blocks nd whn a particular adaptiv modulation typ nds. Among othr things, this implis that th FEC intrlavr dpth and cod blocks ar adaptd to accommodat th span of a particular adaptiv modulation typ. Not, howvr, that data from svral usrs could b concatnatd by th MAC (and intrlavd togthr by th PHY) within th span of a givn adaptiv modulation typ MAC Hadr FEC Encapsulation (TDM) So that th MAC hadr data may b dcodd by a rcivr that has just acquird (and dos not yt know th modulation lngths and distributions of usr data), th MAC hadr data should b 1. a fixd, a priori-known block siz; and 2. sparatly FEC-ncodd (and intrlavd) from all othr usr-spcifically-addrssd data niqu Word Dtails Th niqu Word squnc is omniprsnt, apparing in all fram structurs, both in th continuous and burst formats niqu Word Squnc Dsign Critria Th choic of niqu Word is critical, bcaus it is usd as both a Cyclic prfix for frquncy domain qualizrs, and also for channl stimation. Its cyclic prfix rol imposs on constraint: th niqu Word must b at last as long as th maximum dlay sprad to b xprincd by an intndd rcivr. Its channl stimation rol imposs anothr constraint: th niqu Word should hav good corrlation proprtis, and a broadband, un-notchd frquncy rspons. And lastly, sinc th niqu Word introducs ovrhad, it should b no longr than it nd b; sctors/installations that xprinc lss dlay sprad should not b burdnd with th ovrhad of xcssivly long niqu Words. This implis that som flxibility in th choic (or construction) of niqu Words is rquird. 22

24 niqu Word Squnc Spcification On squnc class that sms to possss all of th dsird proprtis is th modifid PN squnc, as dscribd by Milwski in Rfrnc [26]. As th titl suggsts in Rfrnc [26], this squnc class has optimal proprtis for channl stimation and fast start-up qualization. What s mor, constructions for various squnc lngths ar simpl, du to thir drivation from PN squncs. Th modifid PN squnc is a complx-valud (I + jq) squnc that might b dscribd as quasi- BPSK. It posssss th following structur: Th I channl componnt is drivd from a PN-gnrator (linar fdback shift rgistr) of priod =2 n -1 (whr n is an intgr), and Th Q channl componnt is a small, but non-zro constant squnc, with valu 1. n 2 1 In ordr to rfrnc th constllation to th unit circl, th I and Q componnts dscribd abov ach should n b scald by 1 2. Tabl 3.1 lists th gnrator polynomials that must b usd in gnrating th I componnt of th niqu Word, ovr a usful and practical rang of squnc lngths,. Support for th lngths = 63, and 127 is mandatory. Support of all othr lngths is optional. 11 Tabl 3.1 W lngths and Gnrator Polynomials usd to Gnrat PN Squnc for I Channl (shadd must b supportd) Lngth, (ols) PN Gnrator Polynomial (Binary, with <-> x 5 + x 2 + 1) FFT Intrval (W Intrval) Spcifications In addition to th lngth,, of th niqu Word squnc, anothr important framing paramtr is th intrval btwn niqu Words, N. Howvr, rathr than spcifying N dirctly, w prfr to spcify, F 23

25 = N +, whr F would b th FFT lngth of a ol-spacd frquncy domain qualizrs. Th lngth F = N + should prfrably b 2 raisd to an intgr powr n; in othr words, F = 2 n. A rcivr and transmittr must support n = 1,2,10, which implis that th maximum FFT siz which must b supportd is F = 2 10 = Othr dsirabl FFT sizs, for longr dlay sprad channls, or highr data rats, ar n = 11,12,13, i.., F = 2048, 4096, Framing Rcommndations for Transmit Divrsity Divrsity tchniqus ar likly to find application in som broadband wirlss installations. Noninvasiv tchniqus such as rciv divrsity do not rquir that any spcial considrations on th part of th air intrfac, or framing. For 2-way dlay transmit divrsity, whr two transmit antnnas ar usd and th output of th scond antnna is dlayd with rspct to th first, th considrations ar minor. Both rcivr qualization and framing must b adquat to accommodat th xtra dlay sprad introducd in th systm du to th dlayd output of th scond transmittr. Howvr, th framing rquirs som thought whn th Alamouti transmit divrsity schm [36], which achivs 2-way maximal ratio transmit divrsity combining, is usd. Th Alamouti Algorithm: Alamouti divrsity combining may b applid to ithr th continuous or burst formats, if two conscutiv niqu Word Intrvals (which w will dnot hr as blocks ) ar logically coupld, and ar jointly procssd at both th transmittr and rcivr. Hr w shall illustrat a tchniqu which is particularly amnabl to frquncy domain qualization. Figur 3.10 illustrats th aforsaid concpt of block pairing, and also illustrats th ncssity of sparating th conscutivly paird blocks with dlay sprad guard bands, so that no block laks dlayd information onto th othr. Dlay Sprad Guard (DSG) N s (payload) Dlay Sprad Guard (DSG) N s (payload) Block 1 Block 2 12 Figur 3.10 Two Blocks (niqu Word Intrvals), to which Alamouti transmit divrsity combinr procssing ar intndd to b applid Tabl 3.2 indicats th block signaling structur that must b usd at th transmittr. Not that Transmit Antnna 0 would transmit data according to burst or continuous format spcifications, with no modifications. Howvr, Transmit Antnna 1 must not only rvrs th block 24

26 25 ordr, and conjugat th transmittd complx ols, but must also rvrs th tim squnc of data within ach block bfor snding data ovr th air. 13 Tabl 3.2 Multiplxing arrangmnt to nabl block Alamouti-lik procssing of dlayspradd data with a Singl Carrir Systm. Block 0 Block 1 Transmit Antnna 0 () t s 0 () t s 1 Transmit Antnna 1 ( ) s t * 1 ( ) s t * 0 14 Lt ( ) jω S 0, ( ) jω S 1, ( ) jω H 0, ( ) jω H 0, ( ) jω H 1, ( ) jω N 0 and ( ) jω N 1 b th Discrt-tim Fourir transforms of ol squncs () t s 0 and () t s 1, channl rsponss () t h 0 and () t h 1, and additiv nois squncs () t n 0 and () t n 1. Th rcivd signals associatd with ach block, intrprtd in th frquncy domain, ar: ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ω ω ω ω ω ω ω ω ω ω ω ω j j j j j j j j j j j j N S H S H R N S H S H R 1 * 0 1 * = + = Equation 3.1 Assuming that th channl rsponss ( ) jω H 0 and ( ) jω H 1 ar known, on can us th frquncy domain combining schm ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ω ω ω ω ω ω ω ω ω ω j j j j j j j j j j R H R H C R H R H C 1 * 0 * * * = + =, to obtain th combinr outputs ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ( ) ω ω ω ω ω ω ω ω ω ω ω ω ω ω ω ω j j j j j j j j j j j j j j j j N H N H S H H C N H N H S H H C 1 * 0 * * * = =. Ths combinr outputs can b qualizd using a frquncy domain qualizr (s Rfrnc[20], for xampl) to (vntually) obtain stimats for () t s 0 and () t s 1. Th channl rsponss can also b stimatd using pilot ols. Assum that corrsponding pilot ols ar th sam in th 0 and 1 blocks, i..,

27 S jω pilot jω pilot jω pilot jω pilot 0 ( ) = S 1 ( ) S( ), and that S( ) is known. sing th xprssion from Equation 3.1, on can asily show that S * S jω pilot jω pilot jω pilot jω pilot jω 2 pilot jω pilot ( ) R0 ( ) + S( ) R1 ( ) = 2 S( ) H 0 ( ) jω pilot jω pilot jω pilot jω pilot jω 2 * pilot jω pilot ( ) R ( ) + S( ) R ( ) = 2 S( ) H ( ) 0 1 jω jω This suggsts that on can stimat th channls H 0 ( ) and ( ) 1. H 1 at th pilot locations, and thus idntify th channls thmslvs (if th pilot sampling locations ar slctd proprly) using th xprssions Hˆ Hˆ 0 1 * jω pilot jω pilot jω pilot jω jω pilot pilot S ( ) ( ) R0 ( ) + S ( ) R1 ( ) = jω 2 pilot 2 S ( ) * jω pilot jω pilot jω pilot jω jω pilot pilot S ( ) ( ) R0 ( ) + S ( ) R1 ( ) = 2 S jω pilot ( ) 2. Figur 3.11 illustrats a fram structur, with pilot ols (niqu Word rptitions) which nabls implmntation of th aforsaid tchniqus, including simultanous stimation (or channl updats) of th two channls arising from th us of two transmit antnnas. Not that although th although th spacing btwn basic niqu Words is th sam as prviously, th intrvals ovr which FFTs (for a frquncy domain qualizr) ar computd ar rducd. 26

28 block for channl st B = FFT intrval for FDE block F = M block for channl st B = FFT intrval for FDE block F = M M M W u(t) pilot W u(t) pilot W u(t) Payload 1 p 1 (t) W u(t) pilot W u(t) pilot W u(t) Payload 2 p 2 (t) W u(t) ffctiv cyclic prfix ffctiv cyclic prfix pilot W u * (-t) pilot W -u * (-t) W -u * (-t) tim rv Payload 2 -p * 2 (-t) pilot W -u * (-t) pilot W u * (-t) W u * (-t) tim rv Payload 1 p * 1 (-t) pilot W u * (-t) ffctiv cyclic prfix ffctiv cyclic prfix 15 Figur 3.11 Fram structur suitabl for Alamouti transmit divrsity signaling and associatd channl stimation, whn channl stimation is rquird Figur 3.12 illustrats a similar cas as Figur 3.11, but whr channl stimats and/or channl updats ar not ndd. This cas might occur with in burst format applications, whr th channls might b stimatd with sufficint accuracy using information in th acquisition prambl. 27