Tutorial on TDD Systems

Sujets

• Fiber Distributed Data Interface
• Spectrum (arena)
• Séparation (Royaumes oubliés)
• IEEE 802.11r-2008
• Coexistence pacifique
• Technologie

Informations

• Publié par: Zogit
• Nombre de lectures: 170
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Tutorial on TD D Systems FCC O f fic e o f Engineer in g and Techn o logy Monday , De cember 3, 2 0 01 Part 1: Overview of Duplex Schemes Rém i Cha y er Chairman TDD Coali t io n http:/ /w w w .tddcoalition. org E- ma il: rc h a y e r@ h a rr is .co mThe TD D Coalition It is th e po sition of the TDD Coalition th at wi th p r o p e r planning a n d reg u lato ry co nside r ation s , TDD and oth e r duple x ing t ech nologies can coe x ist in the sam e ge og ra phic a nd spe c t r al spa c e Aper to Ne t w orks LinkAir Malibu Netw orks Arra y c omm BeamRe ach Netw or ks Na v i ni Ne tw orks Caly Netw orks Pointred Te c hnologies Radian t Ne t w ork s Clear w i re Te chnologies Harri s Corpo r a t ion Raze Techn o logies InterDigi t al Wa v i on Ltd IP Wireless December 3, 2 0 0 1 2Overview of the Duplex Schemes ! Definitions " FDD " TDD " Adaptive TD D ! Comparison of TDD vs FDD " Spect r u m Efficiency " Spect r um All o cation and Utilization " Deployment and Net w o r k Planning Issu es " Comp atibility wi th eme r ging applicatio ns and all-IP ne t w o r ks with a s y m m e tr i c tra f f i c " Adaptability to advance d signal pro c e s sing (ada ptive anten na s, use r t e rminal beam -f ormin g , et c. ) " Field trials December 3, 2 0 0 1 3FDD – F requency Division Duplexing ! Separ a te in frequency the dow n stream and upstream directions of the traffic ! Ratio betw een dow n s tream an d upstream traffic fixed by equipment design " 1/2 - 1 / 2 fo r voice " 2/3 – 1 /3 f o r data (typical for 16 QAM do w n , 4 Q AM up ) ! FDD requires a guard band betw een the dow nstr eam and upstream F r equenc y Separati on: x MHz Do w n stre am Upstream Gua r d Band December 3, 2 0 0 1 4TDD – T ime Division Duplexing ! Separ a te in time the dow nstr eam and upstream directions of the traffic An exa m ple o f TDD is h a lf-duplex t r an smission on a n HF com m uni cati on sy ste m u s ing a push - to -talk s w it ch ! Use a single frequency for both dow nstream and upstream ! Ratio betw een dow n s tream an d upstream traffic can be fixed or adaptive ! TDD requires a guard time betw een the dow nstr eam and upstream but no guard band December 3, 2 0 0 1 5Data Traffic Asymmetry I nboun d & O u t bound T r a ffi c ( b p s ) LBL traffic is nearly 100 secs dur at i on, 1 sec bi ns symm e tric averag ed over 2 ed over 2 2. 0E + 0 6 hours (53/4 7 ) 1. 5E + 0 6 but but 1. 0E + 0 6 5. 0E + 0 5 as y mmetric 0. 0E + 0 0 over 1000 1010 1020 1030 1040 1050 1060 1070 10 80 1090 1100 shorter intervals Tim e (se c ) Statistics Averaged Over 2 H our T r ace: our T Aggreg ate: 392 kbps Aggreg Inboun d: 18 5 kbps Inboun Outbound: 20 7 kbps December 3, 2 0 0 1 6 Bits Pe r Se cReal-Time A daptive TDD ! Real-time adaptation provides highest transport efficiency " Milliseco nd re al-time a dap t a tion " 35% imp r ovement over FDD/TDMA ! TDD enabl es 100% use of available spectrum " Well-suited f o r wide , single block allocati ons and na rro w, d ual block allocati ons ! Min i mal latency variation enables prioritization of preferred subscriber s and critical applications December 3, 2 0 0 1 7Spectral Efficiency P e r c e n t I m pr o v m e n t i n S p e c t r a l U t il iz a t io n 45 % 40 % 35 % 30 % 25 % 20 % 15 % 10 % 5% 0% 12 345 6789 1 0 R a t i o 1 : X of T r a f f i c L o a d With asy mme tric traffic (data), TDD sy ste m s use spe c t rum more effi cien tly than FDD systems. December 3, 2 0 0 1 8 P e r cen tSpectral Efficiency ! Minimize guard band ! Change sy mmetry on the fly de pending on subscriber ’s needs ! Adaptive dow n s tream/upstream ratio allow s for emerging new applications w i thout the need for spectrum re-farming ! Enables advanced technologies such as mesh netw or k and adaptive antenna array s ! Highly effective for b u rsty data traffic w h ile still supporting voice December 3, 2 0 0 1 9Spectrum Allocation and Utilization ! TDD allow e d by the FCC, CEPT, Japan, Canada and many other countries ! Some countries still need to be convinced ! FDD absol u tely requires paired spectrum ! TDD can be used w i th paired and unpa ired spectrum “TDD can u s e eithe r sub - b and a nd t he middle gua rd band ” (f ro m an ITU-R Recom m en dation ) ! Block edge mask co ntributes to TDD/FDD coexisten ce ! New mitigation techniques are being dev e loped (Auton omo u s Freq uen cy Allocation – A F A for e x a m pl e) December 3, 2 0 0 1 10