WiBro PHY TTAS.KO R1, released on Dec. 6, 2004

Transcription

1 Standardization and Specifications of WiBro PHY TTAS.KO R1, released on Dec. 6, 2004 July 13, 2005 Hyoungsoo Lim Electronics and Telecommunications Research Institute (ETRI) Tel: (042) ETRI,

2 Contents IEEE OFDM OFDMA Design Principle Key Features OFDM System Parameters WiBro PHY Specifications (Mandatory Stuffs Only) Frame Structure Preamble Subchannelizations Channel codes Ranging Uplink Control Summary ETRI,

3 IEEE WiBro vs. IEEE e IEEE a (FBWA) as a baseline of WiBro design Unique baseline document developed in 2003 Code-named HPi (High-speed Portable internet) Adopted as the baseline document for WiBro (Wireless Broadband) standard in Jan Harmonization with IEEE e (mobile broadband MAN) in progress Supports all mandatory features of IEEE e ETRI,

4 IEEE IEEE 802: IEEE Standards for LAN/MAN LAN: Local Area Network (WLAN: IEEE ) MAN: Metropolitan Area Network (WMAN: IEEE ) Applications of IEEE Applications of IEEE Replacement of ADSL and CATV networks ETRI,

5 IEEE Nomadic and portable services ETRI,

6 IEEE IEEE : Air Interface for Fixed Broadband Wireless Access Systems IEEE Std published in Oct Task Groups: C/e/f/g/h/maint are currently active TGe Amendment to IEEE Std on enhancements to support mobility Scalability for OFDMA mode: 128/512/1024-FFT added Recently, 9 th draft has been released in June 2005 TGmaint Corrigendum to IEEE Std Recently, 3 rd draft has been released in May 2005 SC/SCa/OFDM/OFDMA/HUMAN modes SC: Single carrier for GHz, license-exempt band, TDD/FDD (LOS) SCa/OFDM/OFDMA: < 11 GHz, licensed bands, TDD/FDD (NLOS) HUMAN: < 11 GHz, license-exempt bands, TDD (NLOS) ETRI,

7 IEEE SC/SCa OFDM Orthogonal Frequency Division Multiplexing OFDMA Orthogonal Frequency Division Multiple Access ETRI,

8 IEEE FDD: Frequency Division Duplexing TDD: Time Division Duplexing ETRI,

9 IEEE Development Schedule Development Schedule TGmaint: IEEE s Maintenance Task Group Session #37 (May 2 5) Issue Draft #3 (May 12) Sponsor Ballot (June 1 July 1) Session #38 (July 18 21) Issue Draft #4 (July 29) TGe: Mobile WirelessMAN Adjourned to meet the TGmaint schedule Session #37 (May 2 5) Issue Draft #8 (May 23) Sponsor Ballot recirculation (May 27 June) Face-to-face meeting (June): Small group of experts (ETRI & SEC from Korea) Issue Draft #9 (June 26) Session #38 (July 18 21) Issue Draft #10 (Aug. 2) TGmaint & TGe (Common) Sponsor Ballot recirculation (Aug. 5 20) Submit to RevCom (Aug. 12) RevCom recommends approval (Sep. 21) IEEE SA Standards Board approval (Sep. 22) Publication as standard (Oct.) ETRI,

10 IEEE New Item Mobile Mesh/Relay Networking Proposed by KDDI & SEC at Session #37, May 2005 More than 40 participated in the meeting at Session #37 1 contribution from Nortel Networks Merits Coverage extension & throughput enhancement over NLOS area over highfrequency band in 2-6 GHz ETRI,

11 IEEE Keywords Mesh or relay? Maximum number of hops? Licensed or license-exempt band? PHY, MAC? (Supporting fast route changes) Compatibility with the PMP mode with OFDMA Tentative schedule Proposal to form Study Group at Session #38, July 2005 Complete a PAR at Session Session #41, Jan EC endorses PAR approval in March 2006 Task Group meetings from May 2006 ETRI,

12 IEEE Information Meetings Started in May 2003 (TGe) and Dec (TGmaint) Plenary meetings: Held every March, July, Nov. Interim meetings: Held every Jan., May, Sep. Major participants: Alvarion, ArrayCom, Beceem, ETRI, Huawei, Intel, LG(E), Motorola, Nortel, Runcom, Samsung, Wi-LAN, ZTE, etc. Web pages Open to anyone except for the private directory, IEEE Working Group: WG documents: Announcements Reports Comment DBs (Open with Commentary: TG web pages: Each contains TG documents and contributions TGe: TGmaint: reflector: ETRI,

13 TTA PG302 TTA Project Group GHz 대역휴대인터넷프로젝트그룹 TTA Schedule : TTA Phase-I 규격승인 : TTA Phase-I 규격의 IEEE 규격과의호환성유지를위한 1단계규격수정안승인 Q : TTA Phase-II 규격의요소기술제안및평가 Q : TTA Phase-II 규격승인목표 ( 현재 2단계표준초안승인중 ) ETRI,

14 WiBro Service Schedule : 정보통신부휴대인터넷추진일정및기술방식확정 Compatible with IEEE & P802.16e Requirements Duplexing: TDD Frequency reuse factor: 1 Channel bandwidth: 9 MHz or more Mobility: 60 km/h Minimum data rate: UL 128 kbps, DL 512 kbps : 휴대인터넷사업자선정 KT, SK Telecom, Hanarotelecom 등 3개사업자조기선정 : 상용장비개발완료 각장비 ( 시스템, 중계기, 단말기등 ) 개발업체 2005년말또는 Q에상용시스템개발완료및시험예정 Q : 시범서비스 : 상용서비스시작 (KT, 서울 / 수도권지역 ) ETRI,

15 OFDM History 1957: Kineplex multi-carrier HF modem 1966: Chang, Bell Labs, OFDM paper & patent 1971: Weinstein & Ebert proposed use of FFT and guard interval 1985: Cimini described use of OFDM for mobile communications 1987: Alard & Lasalle, OFDM for digital broadcasting 1995: ETSI DAB standard, first OFDM-based standard 1997: DVB-T standard 1998: Magic WAND project demonstrates OFDM modems for wireless LAN 1999: IEEE a and HIPERLAN/2 standards for wireless LAN 2001: OFDM considered for new IEEE and standards Now: One of the most promising technologies ETRI,

16 OFDM OFDM systems DAB (Digital Audio Broadcasting) European HDTV (High-Definition TeleVision): DVB-T WLAN (Wireless Local Area Network): IEEE a, HiperLAN, HiperLAN2 WMAN (Wireless Metropolitan Area Network): IEEE a &.16e ADSL (Asymmetric Digital Subscribers Loop): DMT ETRI,

17 OFDM OFDM Orthogonal Frequency Division Multiplexing Parallel data transmissions Longer symbol duration Robust to timing offset compared with single carrier scheme FFT (Fast Fourier Transform) 0 1 frequency time 1 OFDM symbol duration signal bandwidth ETRI,

18 OFDM Subcarriers Null subcarriers Guard bands DC subcarrier Used subcarriers Data subcarriers Pilot subcarriers CP (Cyclic Prefix) Robust against multipath delay spread CP T g T b T s ETRI,

19 OFDM Pros Parallel data transmission with long symbol time Robust against multipath delay spread and timing offset Short symbols t t Long symbols (compared with max. multipath delay) t t ETRI,

20 OFDM Pros (cont d) Approximately flat channel per subcarrier One-tap equalizer Equalization for single carrier Large complexity ETRI,

21 OFDM Equalization for OFDM (One-tap equalizer) Can be approximated as constant gains for each subcarrier ETRI,

22 OFDM Pros (cont d) Time & frequency diversity with channel coding High spectral efficiency ETRI,

23 OFDM Cons Narrow subcarrier spacing Sensitive to carrier frequency error Typically, carrier frequency offset within 1 to 2 % of the subcarrier spacing is required Long symbol time Trade-off between mobility and pilot subcarrier overhead / channel estimation performance High mobility Short coherence time Densely distributed pilot subcarriers required for proper channel estimation performance Large PAPR (Peak-to-Average Power Ratio) Superposition of a bunch of randomly modulated subcarriers Limitation on transmit power due to nonlinear characteristic of the high-power amplifier at transmitter ETRI,

24 OFDMA OFDMA Allocation of subcarriers to multiple SS s (Subscriber Stations) in an OFDM symbol time Group of M subcarriers as a unit of allocation Subchannel Subchannelizations Diversity subchannels Statistically identical channel qualities for all diversity subchannels in an OFDM symbol time ETRI,

25 OFDMA Subchannelizations (cont d) Band AMC subchannels Enables efficient resource allocation with optimal transmit power and modulation/coding scheme for each SS in a cell ETRI,

26 OFDMA OFDM + FDMA + TDMA OFDM + FDMA + TDMA 2-dimensional resource allocation ETRI,

27 Design Principles OFDMA scheme Multiple user signals are multiplexed by unit of subchannel in the same OFDM symbols Provides high granularity (compared with OFDM-TDMA scheme) Frequency reuse factor 1 deployment Diversity subchannelization Guarantees the number of hits between subchannels of different cells is even and small Inter-cell interference is averaged Low coding rate Provides robustness against inter-cell interference under full loading ETRI,

28 Design Principles TDD (Time-Division Duplexing) Pros Cons Flexibility in the ratio of DL:UL Feasible for asymmetric services (such as internet) Channel reciprocity between DL (downlink) and UL (uplink) Fast link adaptation with small control overhead Spectrally efficient compared with FDD FDD requires large guard band between DL and UL Synchronism between BSs (Base-Stations) required to avoid large inter-bs interference Limited flexibility Sensitive to fast channel variation Disadvantageous for link adaptation such as AMC, adaptive antenna array, and MIMO Cell coverage reduced by 30% compared with FDD ETRI,

29 Design Principles Flexibly provides band selection and diversity schemes in a single frame User classification according to channel characteristics Band selection users and diversity users For diversity users Utilizes multiple dimensions of diversity to enhance statistical reliability Wideband frequency diversity and temporal diversity Cell planning employed with Partial Usage of Sub-Channels (PUSC) ETRI,

30 Design Principles For band selection users Maximizes multi-user scheduling gain by utilizing channel selectivity of each user Fast CQI (Channel Quality Indicator) report for bands from user terminals are provided BS selects users per band according to channel quality at bands and scheduling criteria BS decides appropriate modulation level and code rate for each user DL Band Selection ETRI,

31 Design Principles Example: AMC gain (1 slot = 24 subcarriers x 1 OFDMA symbol) Selecting the band with maximum SNR from a set of available bands in comparison to the whole band average ETRI,

32 WiBro Design Robustness against channel and interference fluctuation H-ARQ at UL (uplink) and DL (downlink) Fast physical layer retransmission Soft combining and Incremental redundancy Overcome the adaptation error of AMC Higher target FER at PHY (FER 1% 10%) Lower operating SINR (SINR 6 db 4 db) Capacity gain BS Packets MS Typical ARQ at Layer 2 ACK/NAK MAC PDU #1 MAC PDU #2 MAC PDU #2 MAC PDU #1 MAC PDU #2 MAC PDU #2 Hybrid ARQ at Layer 1 MAC PHY MAC PHY PHY #1 PHY #2 PHY #3 PHY #4 PHY #3 PHY #5 PHY #1 PHY #2 PHY #3 PHY #4 PHY #3 PHY #5 Fast retx PHY ETRI, PHY Soft bit combing and IR decoding

33 WiBro Design Short TTI (Transmission Time Interval) 5 ms (c.f., WCDMA 10 ms) Fast AMC Fast access and handoff Support of 60 km/h mobility Maximum Doppler spread 2.35 GHz, 60 km/h f d = Hz Fading coherent time (1/fd) = 7.66 ms Maximum DL pilot subcarrier rotation period 3 symbol spacing: µs < (Coherent time)/10 Maximum UL pilot subcarrier insertion period 6 symbol spacing: µs < (Coherent time)/10 ETRI,

34 Design Principles ETRI,

35 Requirements Value Duplexing Multiple Access Nominal Channel BW User data rate Frequency Reuse Factor Spectral Efficiency (bps/hz/cell) Handoff Mobility Service Coverage (Radius) TDD OFDMA 8.75 MHz UL: min. 128 kbps / max. 1 Mbps DL: min. 512 kbps / max. 3 Mbps 1 DL: max. 6 / avg. 2 UL: max. 2 / avg. 1 Inter-sector / inter-bs / inter-frequency: < 150 ms Max. 60 km/h Pico cell: 100 m Micro cell: 400 m Macro cell: 1 km ETRI,

36 Key Features Multiple Access/Duplexing Duplexing: : OFDMA/TDD Frame length: 5 ms Bandwidth: 8.75 MHz with 1K-FFT Occupied BW: 8.45 MHz Sampling frequency: 10 MHz Flexible subchannelization for diversity and band selection PUSC subchannels (Frequency reuse factor = 1/3) Diversity subchannels (Frequency reuse factor = 1) Fast AMC (Adaptive Modulation and Coding) subchannels Based on UL CQI ETRI,

37 Key Features Cell differentiation by Different subchannelization Different sequences for preamble / scrambling / pilots / etc. Pilot tone based DL and UL Modulation level: QPSK (DL/UL), 16QAM (DL/UL), 64QAM (DL only) More efficient channel coding Convolutional Turbo Code (CTC) Convolutional code (CC) Zero-Tailed Convolutional Code (ZT CC) H-ARQ in DL and UL Separate control channel in UL Dedicated ranging / ACK / CQI channel time slot ETRI,

38 OFDM System Parameters Frequency domain Parameter Sampling frequency Signal bandwidth Subcarrier spacing No. used subcarriers (including DC subcarrier) No. data subcarriers No. pilot subcarriers No. data subcarriers per subchannel Value 10 MHz 8.45 MHz 9.77 khz 865 (Diversity / AMC) 841 (DL & UL PUSC) 768 (Diversity, average / AMC) 720 (DL PUSC) 560 (UL PUSC, average) 96 (Diversity, average / AMC) 120 (DL PUSC) 280 (UL PUSC, average) 48 ETRI,

39 OFDM System Parameters Time domain Parameter Ratio of CP (Cyclic Prefix) time to basic OFDM symbol time Basic OFDMA symbol time CP time OFDMA symbol time TDD frame length Number of symbols in a frame TTG (Transmit/receive Transition Gap) RTG (Receive/transmit Transition Gap) Value 1/ µs 12.8 µs µs 5 ms µs 40.4 µs ETRI,

40 Frame Structure 5 ms frame length : 42 OFDM symbols Flexible DL and UL partitioning in time Separate UL control time slots Ranging channels CQI / ACK / MIMO feedback channels 5 ms Downlink Uplink TTG RTG Preamble Data CQI,ACK Ranging Data ETRI,

41 Frame Structure ETRI,

42 Frame Structure Dynamic resource allocation in a frame Diversity mode All subchannels in identical time slot are statistically identical Averaging inter-cell interference Trade-off with large control overhead and latency Appropriate for mobile SS s Band selection mode Efficient resource allocation to SS s enabled Sensitive to control latency Control overhead: Mitigated with an incremental scheme Appropriate for stationary SS s ETRI,

43 Frame Structure TTG Transmit/receive Transition Gap Larger than max{(max. round-trip delay) + (RX TX RF switching delay at SS), (max. TX RX RF switching delay at BS)} TTG BS DL TX-RX switching delay at BS UL Channel DL propagation delay UL propagation delay SS DL RX-TX switching delay at SS UL ETRI,

44 Frame Structure RTG Receive/transmit Transition Gap Larger than max{(max. TX RX RF switching delay at SS) (max. round-trip delay), (RX TX RF switching delay at BS)} RTG BS UL RX-TX switching delay at BS DL Channel UL propagation delay DL propagation delay SS UL TX-RX switching delay at SS DL ETRI,

45 PUSC PUSC: Partial Usage of Sub-Channels Partial employment of cell planning with frequency reuse factor of 1/3 FCH: Frame Control Header DL PUSC: c.f. FUSC: Full Usage of Sub-Channels ETRI,

46 DL Frame OFDM Parameters DL symbol parameter Number of bands Number of bins per band Number of tones per bin Number of bins per AMC subchannel Number of tones per subchannel Value (8 data + 1 pilot tones) 6 54 (48 data + 6 pilot tones) ETRI,

47 DL Frame Preamble Preamble structure Time domain First OFDM symbol in DL Conjugate symmetric OFDMA symbol + CP Implicitly repeats itself 3 times within the basic OFDMA symbol time ETRI,

48 DL Frame Preamble Frequency domain Non-zero pilot tones every 3 subcarriers (DC subcarrier is not modulated) Different subcarrier offset of pilot tones for different segments in a cell 114 different BPSK patterns defined for different cell & segment IDs Power boosted by 9 db per pilot 4.26 db higher OFDMA symbol energy than data OFDMA symbols Example of Segment ID = 0: Used Null Subcarrier index ETRI,

49 DL Frame Initial Sync. Procedure (Example) Example of initial synchronization procedure using the preamble Frame timing acquisition Searching for maximum auto-correlation between repeating patterns in time domain Frequency offset estimation Average phase rotation between sample pairs from repeating patterns (or CP s in the data payload after the preamble) Cell search Cross-correlations in frequency domain Differential demodulation to compensate frequency selective fading Best cell search by comparing the cross-correlation magnitudes Symbol timing estimation Average slope of phase rotation over all nonzero subcarriers Channel estimation More reliable than using pilot/data subcarriers embedded in payload ETRI,

50 DL Frame Common SYNC Symbol (Optional) Guarantees initial synchronization for SS s s at cell edge Transmitted at the end of DL frame every 4 frames Synchronous and identical for all BS s Time domain Length: 1 OFDMA symbol time 2 repetitions during basic OFDMA symbol time ETRI,

51 DL Frame Common SYNC Symbol (Optional) Frequency domain Non-zero pilot tones every 2 subcarriers BPSK modulation pattern 473A0B21CE9537F3A0B20316AC873A0B21CE95378C5F4DFCE9537F3A0B 21CE9537F3A0B20316AC80C5F4DE316AC873A0B20316AC800 (hexadecimal) PAPR: 3.32 db DC subcarrier is not modulated ETRI,

52 DL Frame FCH Frame Control Header First 4 PUSC subchannels DL Frame Prefix Used subchannel bitmap Ranging change indication Repetition coding indication: 1, 2, 4, or 6 repetitions Coding indication: DL-MAP encoding scheme (CC, CTC, ZTCC) DL-MAP length Channel coding & modulation 24 data bits 2 repetitions (48 bits) R=1/2 convolutional code (96 bits) QPSK (48 QPSK symbols) 4 repetitions (192 QPSK symbols) 4 PUSC subchannels (1 subchannel = 48 data subcarriers) ETRI,

53 DL Frame Pilots Pilot subcarriers in PUSC zone Identical positions for all cells PN cover for cell differentiation ETRI,

54 DL Frame Pilots Pilot subcarriers in AMC & diversity zone Separated by 9 subcarriers Cyclic shift by 3 subcarriers as symbol index increases Identical positions for all cells PN cover for cell differentiation ETRI,

55 DL Frame Pilots 6 pilot tones per AMC subchannel Example of 2x3: Pilot subcarrier Data subcarrier AMC subchannel Freq. Time ETRI,

56 DL Frame PUSC Clustering 840 subcarriers 60 clusters 1 cluster: (2 pilot + 12 data subcarriers) X 2 symbols Sectorization Allocate one or more major groups of clusters to a sector Subchannel IDcell-based permutation 1 subchannel = 24 distributed data subcarriers X 2 symbols Subcarriers Clusters Renumbering Major Groups Regrouping Subchannels C0 C1 840 subcarriers C59 C0 C1 C59 Segment 0 Segment 1 Segment 2 C0 ~ C11 12 ~ ~ ~ ~ ~ 59 6 data 4 data 24groups 24groups 24groups 24groups 24groups 24groups 24 data S0 S1 S9 S10 S1 S19 S20 S1 S29 6 subch 4 subch 6 subch 4 subch 6 subch 4 subch 2 symbols 2 symbols ETRI,

57 DL Frame PUSC Mandatory for FCH (IDcell( IDcell=0) Sectorization Sector 0 Default: subchannels 0~5 ( 6 subchannels) Sector 1 Default: subchannels 10~15 ( 6 subchannels) Sector 2 Default: subchannels 20~25 ( 6 subchannels) 1 cell - 3 sectors Sector 0 Sector 1 Sector 2 ETRI,

58 DL Frame Diversity Subchannels (O-FUSC) Subchannel IDcell-based permutation 48 distributed data subcarriers in a symbol Left Guard Band (86 subcarriers) Data subcarrier Pilot subcarrier Right Guard Band (87 subcarriers) Subcarriers Pilot subcarriers Data subcarriers Groups Subchannels G0 S0 864 subcarriers G1 G2 G47 48 subcarriers S1 S15 1 symbols 96 subcarriers 768 subcarriers 1 symbols ETRI,

59 Band AMC Subchannel (DL & UL) Band Structure 864 subcarriers 24 bands 1 band 4 bins (4x9=36 subcarriers) 1 bin 1 pilot subcarrier + 8 data subcarrier Rotated pilots 9-subcarrier spacing Same pattern every 3 symbols Pilot defined in a subchannel! 24 bands 4 bins... ETRI,

60 Band AMC Subchannel (DL & UL) Subchannel 6 adjacent bins 6 pilot + 48 data subcarriers 4 types Default (4+2, 2+4) 1 x 6 bins 2 x 3 bins 3 x 2 bins ETRI,

61 UL Frame OFDM Parameters UL symbol / tile parameter Number of bands Number of bins per band Number of tones per bin Number of tones per tile Number of bins per AMC subchannel Number of tiles per diversity & PUSC subchannels Value (8 data + 1 pilot tones) Diversity: 9 (8 data + 1 pilots) PUSC: 12 (8 data + 4 pilots) 6 6 ETRI,

62 UL Frame Pilots Pilot subcarriers for PUSC zone For low CINR SS s PN cover for cell differentiation Pilot subcarriers for diversity zone For high CINR SS s PN cover for cell differentiation ETRI,

63 UL Frame Pilots Pilot subcarriers for AMC zone Separated by 9 subcarriers in a symbol Cyclic shift by 3 subcarriers as symbol index increases PN cover for cell differentiation ETRI,

64 UL Frame Pilots 6 pilot tones per AMC subchannel Example of 2x3: Pilot subcarrier Data subcarrier AMC subchannel Freq. Time ETRI,

65 UL Frame PUSC Tile structure 4 subcarriers x 3 symbols 4 pilot tones + 8 data tones Subchannel IDcell-based permutation 6 distributed tiles 24 pilot tones + 48 data tones Pilot defined in a subchannel! Segmentation Using UL allocated subchannel bitmap (in UCD) Subcarriers Tiles Tile groups Subchannels 840 subcarriers... T0 T1 T2 T209 T0~T34 T35~T69 T175~T209 6 tiles... S0 S1 S34 3 symbols 210 tiles 6 groups 35 subchannels ETRI,

66 UL Frame Diversity Subchannel Tile structure 3 subcarriers x 3 symbols 1 pilot tone + 8 data tones Subchannel IDcell-based permutation 6 distributed tiles 6 pilot tones + 48 data tones Pilot defined in a subchannel! Segmentation Using UL allocated subchannel bitmap (in UCD) Subcarriers Tiles Tile groups Subchannels 864 subcarriers... T0 T1 T2 T287 T0~T15 T16~T31 T32~T47 T252~T267 T268~T287 6 tiles... S0 S1 S34 3 symbols 288 tiles 18 groups 48 subchannels ETRI,

67 UL Frame Mini Subchannel UL mini subchannel Same tile structure (3x3 tile) as in UL diversity subchannel Concatenated M (=2,3,6) subchannels in time domain 1 mini subchannel: 6/M tiles x M symbols 4 types: CType = 00, 01, 10, 11 ETRI,

68 Channel Coding and Modulation Process Data burst Padding and randomization FEC Bit interleaving Repetition Scrambling Modulation Subchannels Forward Error Correction (FEC) coding Convolutional Coding For Frame Control Header (FCH) Convolutional Turbo Coding without HARQ For MAP and Traffic Burst Convolutional Turbo Coding with HARQ For Traffic Burst Zero-tailed convolutional coding Low rate coding and Repetition Provides a high processing gain for users at the cell edge ETRI,

69 Padding & Randomization Padding before randomization Add 1 to the end of the burst, if Data size < Allocated size Data scrambled by a PN sequence PRBS generator: 1+X 14 +X 15 msb lsb data in data out ETRI,

70 Channel Coding CC & ZT-CC CC (Convolutional( Code) R=1/2, (171, 173) 8 Applied to FCH ZT CC (Zero Tailed Convolutional Code) 0x00 tail byte is appended at the end of each burst (after randomization) ETRI,

71 Channel Coding CC Encoder Mother code rate of 1/2 and Constraint length K=7 Higher code rate 2/3, 3/4, and 5/6 by puncturing Lower code rate 1/4, 1/8, and 1/12 by repetition FEC payload size 6, 9, 12, 18, 24, 27, 30, 36 [bytes] X output Data in 1 bit delay 1 bit delay 1 bit delay 1 bit delay 1 bit delay 1 bit delay Y output ETRI,

72 Channel Coding Bit Interleaving Block Interleaving Applied to (concatenated) FEC block(s) Two step permutation 1 st step permutation Mapping adjacent coded bits onto nonadjacent subcarriers For frequency diversity 2 nd step permutation Alternatively mapping adjacent coded bits onto LSB or MSB of the constellation For avoiding long runs of lowly reliable bits ETRI,

73 Channel Coding Repetition Repetition R = 2, 4, or 6 Group-wise repetition of the encoded and interleaved block Lower code rates of 1/4, 1/8, and 1/12 by repetition of 2, 4, and 6 of a R=1/2 encoded block ETRI,

74 Channel Coding CTC Convolutional Turbo Code Rate 1/3 mother code for H-ARQ (Incremental redundancy) Effective code rate: 1/12 ~ 5/6 with QPSK, 16QAM, 64QAM Repetition and puncturing from mother code Fixed size encoder input sizes Large information block size up to 4800 bits Provides interleaving gain ETRI,

75 Channel Coding CTC H-ARQ supported H-ARQ not supported ETRI,

76 Channel Coding CTC Encoder Coded bit stream: A 1 B 1 A 2 B 2 A N B N, Y 11 Y 21 W 21 Y 22 W 22 Y 2N W 2N 11 W 11 Y 12 W Y 1N 1N W 1N, output A B A B CTC Interleaver 1 2 switch Constituent Encoder C 1 C 2 Y 1 W 1 Y 2 W 2 Systematic part A S 1 S 2 S 3 B W Y Parity part ETRI,

77 H-ARQ H-ARQ: Hybrid Automatic Repeat and request Incremental Redundancy based H-ARQ H for UL and DL To mitigate the effect of channel and interference fluctuation Overcome adaptation error of AMC in fading channel To render performance improvement due to SNR gain and time diversity achieved by combiningng sub-packets Transmit different redundancy version for different sub-packet H-ARQ provides flexibility to adapt the sub-packet transmission rate according to the most recent channel quality feedback Maximum number of sub-packet retransmission depends on service classes ETRI,

78 Interleaving & Symbol Selection for H-ARQH CTC Encoder Interleaver Symbol Selection Uplink Puncturing A B A' B' CTC Interleaver 1 2 switch Constituent Encoder C 1 C 2 Interleaving Symbol Selection Z Puncturing AB Subblock Y1 Y2 W1 W2 Subblock Subblock Subblock Subblock Subblock Subblock Subblock Subblock Subblock Interleaver Interleaver Interleaver Interleaver Interleaver ETRI,

79 H-ARQ Gain Throughput gain of H-ARQ H soft combining Incremental redundancy 1 Throughput of HARQ with code combining and diversity combining: R=2/3 sub codes over AWGN Max iteration= 8, Information block size=496bits, Number of sub codes for combining=2 0.9 Code Combining (2/3, 2/3) 0.8 Diversity Combining (2/3, 2/3) 0.7 HARQ Type I without SC THROUGHPUT Es/No (db) ETRI,

80 Modulation Scrambling Scramble all pilot and data Using a cell/sector-specific PN pattern, p[n] For the discrimination of target pilot and data from those of different cells/sectors PRBS generation 1+X 9 +X 11 MSB 초기화벡터 b 10 b 9 b 8 LSB b 7 b 6 b 5 b 4 b 3 b 2 b 1 b p[n] ETRI,

81 Modulation Pilot Modulation BPSK modulation of the scrambling sequence Pilot boosting 2.5 db boosting, compared with data tone Re{c k }=4(1-2w k )/3, Im{c k }=0 ETRI,

82 Modulation Data Modulation Constellation Mapping Gray mapping DL: QPSK, 16QAM, 64QAM UL: QPSK, 16QAM b Q c = 1/ I b b 2b1b Q c = 1/ b 1 b Q c = 1/ I b 3 b ETRI, b 010 I 5b4b3

83 Mapping DL 2-D allocation Maps data symbols in the order of increasing subchannel index and then OFDMA symbol index ETRI,

84 Mapping UL 1-D allocation Maps data symbols in the order of increasing OFDMA symbol index and then subchannel index ETRI,

85 UL Control Symbols First 3 UL OFDMA symbols Diversity subchannels Ranging channels Initial ranging & handoff ranging: First 2 OFDMA symbols Periodic ranging & bandwidth request ranging: 3 rd OFDMA symbol CQI, ACK, MIMO feedback channels Fast feedback on PHY link Allocated to users, like a dedicated channel ETRI,

86 UL Control Ranging Objectives BS can detect the received timing and power of each ranging signals Synchronization of UL bursts arrival timings at BS Coarse UL power control Ranging = Distance measurement = Measurement of propagation delay & path loss = UL timing & power alignment Additional (UL) carrier frequency synchronization possible UL bandwidth request Ranging: Contention-based aceess in time-frequency-code space Can be exploited in random access for UL resource allocation request ETRI,

87 UL Control Ranging 4 ranging modes defined Initial ranging Hand off (HO) ranging Periodic ranging Bandwidth request (BR) ranging Ranging modes are differentiated by frequency-domain code and time slot Initial & handoff rangings: First 2 UL OFDM symbols Periodic & bandwidth request rangings: 3 rd UL OFDM symbol Ranging codes generated with a PN code generator according to cell ID Total 255 ranging codes per cell ID Distinct code sets for each ranging mode ETRI,

88 UL Control Ranging Time domain structure Initial & HO ranging Periodic & BR ranging Initial & handoff rangings: Continuous phase over 2 OFDM symbol times Enables successful detection of the ranging code and its timing offset at BS Carrier frequency offset can be estimated using the repeating pattern ETRI,

89 UL Control Ranging Separate time interval for initial/handoff ranging Interference is localized in time No interference to data traffic Users are allowed to collide on ranging subchannels Contention based random access with randomly selected code and ranging channel (spaced in time-frequency domain) Max. 255 BPSK-modulated 144-bit sequences per cell in freq. domain ETRI,

90 UL Control CQI CQI channel DL CINR feedback For AMC operation MIMO antenna weight feedback MIMO mode feedback For MIMO mode and subcarrier permutation selection Payload: 4, 5, (or 6) bits DL CINR for diversity/pusc subchannels Differential CINR for band AMC subchannels 1 bit (up/down) per 2 adjacent bands 4, 5, (or 6) differential CINRs in a CQI Subchannel 6 3x3 tiles (same as the diversity subchannel) 54 tones = 6 pilot tones + 48 data tones ETRI,

91 UL Control CQI CQI encoding Non-binary block coding CQI channel Payload (4, 5, or 6 bits) Codeword (6 vector indices) Example of 5 bit payload: 5-bit payload Vector indices per tile 0b b b ETRI,

92 UL Control CQI Pilot tone Data tone ETRI,

93 UL Control CQI Channel Modulation Modulation 8-ary orthogonal modulation 6 vector indices 6 symbol vectors in 6 tiles One vector index one symbol vector (8 QPSK symbols) Vector index Symbol vector 0 P0, P1, P2, P3, P0, P1, P2, P3 1 P0, P3, P2, P1, P0, P3, P2, P1 2 P0, P0, P1, P1, P2, P2, P3, P3 3 P0, P0, P3, P3, P2, P2, P1, P1 4 P0, P0, P0, P0, P0, P0, P0, P0 5 P0, P2, P0, P2, P0, P2, P0, P2 6 P0, P2, P0, P2, P2, P0, P2, P0 7 P0, P2, P2, P0, P2, P0, P0, P2 M n, 8 m π 3π 3π π P 0 = exp( j ), P 1 = exp( j ), P 2 = exp( j ), P3 = exp( j ) CQI/ACK Symbol Mapping in m th Tile M n, 8m+ 1 M n, 8m+ 2 M n, 8m+ 3 Pilot Tone M n, 8m+ 4 M n, 8m+ 5 M n, 8m+ 6 M n, 8m+ 7 ETRI,

94 UL Control MIMO Antenna Weight Feedback MIMO antenna weight feedback via CQI channel A complex weight represented by a CQI Example of 5 bit payload: ETRI,

95 UL Control Channels MIMO Mode Feedback MIMO mode feedback via CQI channel Example of 5 bit payload Value 0b b b b b b b b00111 Description STTD and PUSC/diversity permutation STTD and AMC permutation SM and PUSC/diversity permutation SM and AMC permutation Closed-loop SM and PUSC/diversity permutation Closed-loop SM and AMC permutation Closed-loop SM + Beamforming and AMC permutation TD + Beamforming and AMC permutation ETRI,

96 UL Control Channels ACK ACK channel ACK/NACK feedback for H-ARQ operation For ACK channel: 3 tiles used (One subchannel two ACK CHs) ACK/NACK bit (1 bits) Block coding Codeword (3 alphabets) 8-ary orthogonal modulation ACK channel (Three 3-by-3 tiles) Pilot tone Data tone ETRI,

97 UL Control Channels ACK ACK encoding Non-binary block coding Payload (1 bit) Codeword (3 vector indices) 1-bit payload Vector indices per Tile 0 0, 0, 0 1 4, 7, 2 3 symbol vectors in 3 tiles ETRI,

98 Summary WiBro and IEEE e IEEE TTA PG302 OFDM History Basics Pros and cons OFDMA OFDM + FDMA + TDMA Subchannelizations ETRI,

99 Summary WiBro design principles OFDMA for spectral efficiency, granularity, band AMC gain, etc. Frequency reuse factor of 1 (1/3 with PUSC) Dynamic mode control: Diversity / band AMC / PUSC H-ARQ WiBro key features OFDMA/TDD with 5 ms frame 8.75 MHz channel bandwidth with 1K-FFT Flexible subchannelization for diversity / band AMC / PUSC Channel codes: CC / CTC / ZT CC H-ARQ in DL and UL Separate control channel in UL frame for ranging / ACK / CQI ETRI,

100 Summary PHY specifications Frame Structure Preamble & common SYNC symbol Subchannelizations & pilot subcarrier allocations DL: Diversity, PUSC, band AMC UL: Diversity, PUSC, band AMC, mini-subchannel Channel coding: CC, ZT-CC, CTC H-ARQ Modulation & mapping Uplink control symbols Ranging CQI MIMO antenna weight feedback MIMO mode feedback ACK ETRI,

101 Thank You ETRI,